21 CFR 520.1802c - Piperazine-carbon disulfide complex with phenothiazine suspension.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Piperazine-carbon disulfide complex with... ANIMAL DRUGS § 520.1802c Piperazine-carbon disulfide complex with phenothiazine suspension. (a) Specifications. Each fluid ounce contains 5 grams of piperazine-carbon disulfide complex and 0.83 gram...
21 CFR 520.1802c - Piperazine-carbon disulfide complex with phenothiazine suspension.
Code of Federal Regulations, 2012 CFR
2012-04-01
... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Piperazine-carbon disulfide complex with... ANIMAL DRUGS § 520.1802c Piperazine-carbon disulfide complex with phenothiazine suspension. (a) Specifications. Each fluid ounce contains 5 grams of piperazine-carbon disulfide complex and 0.83 gram...
21 CFR 520.1802c - Piperazine-carbon disulfide complex with phenothiazine suspension.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Piperazine-carbon disulfide complex with... ANIMAL DRUGS § 520.1802c Piperazine-carbon disulfide complex with phenothiazine suspension. (a) Specifications. Each fluid ounce contains 5 grams of piperazine-carbon disulfide complex and 0.83 gram...
21 CFR 520.1802c - Piperazine-carbon disulfide complex with phenothiazine suspension.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Piperazine-carbon disulfide complex with... ANIMAL DRUGS § 520.1802c Piperazine-carbon disulfide complex with phenothiazine suspension. (a) Specifications. Each fluid ounce contains 5 grams of piperazine-carbon disulfide complex and 0.83 gram...
21 CFR 520.1802c - Piperazine-carbon disulfide complex with phenothiazine suspension.
Code of Federal Regulations, 2013 CFR
2013-04-01
... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Piperazine-carbon disulfide complex with... ANIMAL DRUGS § 520.1802c Piperazine-carbon disulfide complex with phenothiazine suspension. (a) Specifications. Each fluid ounce contains 5 grams of piperazine-carbon disulfide complex and 0.83 gram...
2015-06-10
WarpVisit is an insitu simulation application that integrates the Warp laser plasma accelerator simulation framework with Visit a parallel visualization application. WarpVisit is written in python and supports interactive or live mode where user can connect to Warp with the Visit GUI and batch mode for batch for non-interactive use on high-performance computing resources.
NASA Astrophysics Data System (ADS)
Swarup, Bob
2008-01-01
Warp drives are a staple of science fiction, transporting the heroes of shows like Star Trek between galaxies in a matter of hours. Now, increasing numbers of cosmologists are wondering whether this technology might eventually become science fact. Dozens of scientific papers on warp drives have appeared since 1994 when Miguel Alcubierre - a theoretical physicist then at the University of Wales in Cardiff - first argued that a warp drive was theoretically possible (Class. Quantum Grav. 11 L73)
NASA Astrophysics Data System (ADS)
González-Díaz, Pedro F.
2007-09-01
In this Letter we consider a warp drive spacetime resulting from that suggested by Alcubierre when the spaceship can only travel faster than light. Restricting to the two dimensions that retains most of the physics, we derive the thermodynamic properties of the warp drive and show that the temperature of the spaceship rises up as its apparent velocity increases. We also find that the warp drive spacetime can be exhibited in a manifestly cosmological form.
Slagter, R. J.
2010-06-23
We present a cosmic string solution in Einstein-Yang-Mills Gauss-Bonnet theory on a warped 5 dimensional space-time conform the Randall-Sundrum-2 theory. In a simplipied model, we find an exact solutions with exponential decreasing or periodic warp function. In a more general setting, where the metric- and Yang-Mills components depend on both scales and one of the YM components resides in the bulk, we find a time dependent numerical solution.
NASA Astrophysics Data System (ADS)
Anninos, Dionysios; Samani, Joshua; Shaghoulian, Edgar
2014-02-01
We study the applicability of the covariant holographic entanglement entropy proposal to asymptotically warped AdS3 spacetimes with an SL(2, ℝ) × U(1) isometry. We begin by applying the proposal to locally AdS3 backgrounds which are written as an ℝ1 fibration over AdS2. We then perturb away from this geometry by considering a warping parameter a = 1 + δ to get an asymptotically warped AdS3 spacetime and compute the dual entanglement entropy perturbatively in δ. We find that for large separation in the fiber coordinate, the entanglement entropy can be computed to all orders in δ and takes the universal form appropriate for two-dimensional CFTs. The warping-dependent central charge thus identified exactly agrees with previous calculations in the literature. Performing the same perturbative calculations for the warped BTZ black hole again gives universal two-dimensional CFT answers, with the left-moving and right-moving temperatures appearing appropriately in the result.
NASA Astrophysics Data System (ADS)
White, H.
This paper will begin with a short review of the Alcubierre warp drive metric and describes how the phenomenon might work based on the original paper. The canonical form of the metric was developed and published in [6] which provided key insight into the field potential and boost for the field which remedied a critical paradox in the original Alcubierre concept of operations. A modified concept of operations based on the canonical form of the metric that remedies the paradox is presented and discussed. The idea of a warp drive in higher dimensional space-time (manifold) will then be briefly considered by comparing the null-like geodesics of the Alcubierre metric to the Chung-Freese metric to illustrate the mathematical role of hyperspace coordinates. The net effect of using a warp drive "technology" coupled with conventional propulsion systems on an exploration mission will be discussed using the nomenclature of early mission planning. Finally, an overview of the warp field interferometer test bed being implemented in the Advanced Propulsion Physics Laboratory: Eagleworks (APPL:E) at the Johnson Space Center will be detailed. While warp field mechanics has not had a "Chicago Pile" moment, the tools necessary to detect a modest instance of the phenomenon are near at hand.
NASA Technical Reports Server (NTRS)
White, Harold
2011-01-01
This paper will begin with a short review of the Alcubierre warp drive metric and describes how the phenomenon might work based on the original paper. The canonical form of the metric was developed and published in [6] which provided key insight into the field potential and boost for the field which remedied a critical paradox in the original Alcubierre concept of operations. A modified concept of operations based on the canonical form of the metric that remedies the paradox is presented and discussed. The idea of a warp drive in higher dimensional space-time (manifold) will then be briefly considered by comparing the null-like geodesics of the Alcubierre metric to the Chung-Freese metric to illustrate the mathematical role of hyperspace coordinates. The net effect of using a warp drive technology coupled with conventional propulsion systems on an exploration mission will be discussed using the nomenclature of early mission planning. Finally, an overview of the warp field interferometer test bed being implemented in the Advanced Propulsion Physics Laboratory: Eagleworks (APPL:E) at the Johnson Space Center will be detailed. While warp field mechanics has not had a Chicago Pile moment, the tools necessary to detect a modest instance of the phenomenon are near at hand.
Generalized Canonical Time Warping.
Zhou, Feng; De la Torre, Fernando
2016-02-01
Temporal alignment of human motion has been of recent interest due to its applications in animation, tele-rehabilitation and activity recognition. This paper presents generalized canonical time warping (GCTW), an extension of dynamic time warping (DTW) and canonical correlation analysis (CCA) for temporally aligning multi-modal sequences from multiple subjects performing similar activities. GCTW extends previous work on DTW and CCA in several ways: (1) it combines CCA with DTW to align multi-modal data (e.g., video and motion capture data); (2) it extends DTW by using a linear combination of monotonic functions to represent the warping path, providing a more flexible temporal warp. Unlike exact DTW, which has quadratic complexity, we propose a linear time algorithm to minimize GCTW. (3) GCTW allows simultaneous alignment of multiple sequences. Experimental results on aligning multi-modal data, facial expressions, motion capture data and video illustrate the benefits of GCTW. The code is available at http://humansensing.cs.cmu.edu/ctw. PMID:26761734
NASA Astrophysics Data System (ADS)
Coule, D. H.
1998-08-01
The warp drive spacetime of Alcubierre is impossible to set up without first being able to distribute matter at tachyonic speed, put roughly, you need one to make one! However, over small distances, where the energy conditions possibly can be violated, one can envision opening the light-cones to increase the apparent speed of light.
NASA Astrophysics Data System (ADS)
Osborne, Jonathan
2010-02-01
João Magueijo's article "Cargo-cult training" about the failings of compulsory educational training for lecturers (December 2009 pp16-17) is an illustration of why some university lecturers do need to be educated about education. His argument that we should use lectures because students like them ignores the large body of educational research stating that this is the least effective form of education. It might, as the well-known aphorism states, be a successful means of transferring the notes of the lecturer to the notes of the students without going through the minds of either, but the evidence shows that only 10% of students learn material in this way. Rather, all the educational literature points to the fact that interactive, discursive methods are much more likely to produce learning with understanding.
LittleQuickWarp: an ultrafast image warping tool.
Qu, Lei; Peng, Hanchuan
2015-02-01
Warping images into a standard coordinate space is critical for many image computing related tasks. However, for multi-dimensional and high-resolution images, an accurate warping operation itself is often very expensive in terms of computer memory and computational time. For high-throughput image analysis studies such as brain mapping projects, it is desirable to have high performance image warping tools that are compatible with common image analysis pipelines. In this article, we present LittleQuickWarp, a swift and memory efficient tool that boosts 3D image warping performance dramatically and at the same time has high warping quality similar to the widely used thin plate spline (TPS) warping. Compared to the TPS, LittleQuickWarp can improve the warping speed 2-5 times and reduce the memory consumption 6-20 times. We have implemented LittleQuickWarp as an Open Source plug-in program on top of the Vaa3D system (http://vaa3d.org). The source code and a brief tutorial can be found in the Vaa3D plugin source code repository. PMID:25233807
Warped general gauge mediation
NASA Astrophysics Data System (ADS)
McGarrie, Moritz; Thompson, Daniel C.
2010-12-01
We develop the formalism of “general gauge mediation” for five-dimensional theories in a slice of AdS space. A set of current correlators encodes the effect of a supersymmetry breaking hidden sector localized on the IR brane. These current correlators provide a tree-level gaugino mass and loop-level sfermion masses on the UV brane. We also use this formalism to calculate the Casimir energy and masses for bulk hyperscalars. To illustrate this general construction we consider a perturbative hidden sector of generalized messengers coupled to a spurion. For models with large warping, we find that when the AdS warp factor k is less than the characteristic mass scale M of the hidden sector, the whole Kaluza-Klein tower of vector superfields propagate supersymmetry breaking effects to the UV brane. When M is less than k, the zero modes dominate.
Asymmetrically warped spacetimes
Csaki, C.
2001-01-01
We investigate spacetimes in which the speed of light along flat 4D sections varies over the extra dimensions due to different warp factors for the space and the time coordinates ('asymmetrically warped' spacetimes). The main property of such spaces is that while the induced metric is flat, implying Lorentz invariant particle physics on a brane, bulk gravitational effects will cause apparent violations of Lorentz invariance and of causality from the brane observer's point of view. An important experimentally verifiable consequence of this is that gravitational waves may travel with a speed different from the speed of light on the brane, and possibly even faster. We find the most general spacetimes of this sort, which are given by certain types of black hole spacetimes characterized by the m a s and the charge of the black hole. We show how to satisfy the junction conditions and analyze the properties of these space-times.
Warp drive with zero expansion
NASA Astrophysics Data System (ADS)
Natário, José
2002-03-01
It is commonly believed that Alcubierre's warp drive works by contracting space in front of the warp bubble and expanding the space behind it. We show that this contraction/expansion is but a marginal consequence of the choice made by Alcubierre and explicitly construct a similar spacetime where no contraction/expansion occurs. Global and optical properties of warp-drive spacetimes are also discussed.
Kobayashi, Takeshi; Mukohyama, Shinji
2010-06-23
We present a curvaton model from type IIB string theory compactified on a warped throat with approximate isometries. Considering an (anti-)D3-brane sitting at the throat tip as a prototype standard model brane, we show that the brane's position in the isometry directions can play the role of curvatons. The basic picture is that the fluctuations of the (anti-)D3-brane in the angular isometry directions during inflation eventually turns into the primordial curvature perturbations, and subsequently the brane's oscillation excites other open string modes on the brane and reheat the universe. We find in the explicit case of the KS throat that a wide range of parameters allows a consistent curvaton scenario. It is also shown that the oscillations of branes at throat tips are capable of producing large non-Gaussianity, either through curvature or isocurvature perturbations. Since such setups naturally arise in warped (multi-)throat compactifications and are constrained by observational data, the model can provide tests for compactification scenarios. This work gives an explicit example of string theory providing light fields for generating curvature perturbations. Such mechanisms free the inflaton from being responsible for the perturbations, thus open up new possibilities for inflation models. The discussions in this paper are based on [1].
Kobayashi, Takeshi; Mukohyama, Shinji E-mail: shinji.mukohyama@ipmu.jp
2009-07-01
We present a curvaton model from type IIB string theory compactified on a warped throat with approximate isometries. Considering an (anti-)D3-brane sitting at the throat tip as a prototype standard model brane, we show that the brane's position in the isometry directions can play the role of curvatons. The basic picture is that the fluctuations of the (anti-)D3-brane in the angular isometry directions during inflation eventually turns into the primordial curvature perturbations, and subsequently the brane's oscillation excites other open string modes on the brane and reheat the universe. We find in the explicit case of the KS throat that a wide range of parameters allows a consistent curvaton scenario. It is also shown that the oscillations of branes at throat tips are capable of producing large non-Gaussianity, either through curvature or isocurvature perturbations. Since such setups naturally arise in warped (multi-)throat compactifications and are constrained by observational data, the model can provide tests for compactification scenarios. This work gives an explicit example of string theory providing light fields for generating curvature perturbations. Such mechanisms free the inflaton from being responsible for the perturbations, thus open up new possibilities for inflation models.
ERIC Educational Resources Information Center
Chaudhury, S. Raj
2011-01-01
Academic lectures for the purpose of instruction maintain an important presence in most colleges and universities worldwide. This chapter examines the current state of the lecture and how learning sciences research can inform the most effective use of this method. The author presents evidence that the lecture can be an effective element of…
Copeland, H Liesel; Longworth, David L; Hewson, Mariana G; Stoller, James K
2000-01-01
OBJECTIVE In a study conducted over 3 large symposia on intensive review of internal medicine, we previously assessed the features that were most important to course participants in evaluating the quality of a lecture. In this study, we attempt to validate these observations by assessing prospectively the extent to which ratings of specific lecture features would predict the overall evaluation of lectures. MEASUREMENTS AND MAIN RESULTS After each lecture, 143 to 355 course participants rated the overall lecture quality of 69 speakers involved in a large symposium on intensive review of internal medicine. In addition, 7 selected participants and the course directors rated specific lecture features and overall quality for each speaker. The relations among the variables were assessed through Pearson correlation coefficients and cluster analysis. Regression analysis was performed to determine which features would predict the overall lecture quality ratings. The features that most highly correlated with ratings of overall lecture quality were the speaker's abilities to identify key points (r = .797) and be engaging (r = .782), the lecture clarity (r = .754), and the slide comprehensibility (r = .691) and format (r = .660). The three lecture features of engaging the audience, lecture clarity, and using a case-based format were identified through regression as the strongest predictors of overall lecture quality ratings (R2= 0.67, P = 0.0001). CONCLUSIONS We have identified core lecture features that positively affect the success of the lecture. We believe our findings are useful for lecturers wanting to improve their effectiveness and for educators who design continuing medical education curricula. PMID:10886470
A breathing mode for warped compactifications
NASA Astrophysics Data System (ADS)
Underwood, Bret
2011-10-01
In general warped compactifications, non-trivial backgrounds for the warp factor and the dilaton break D-dimensional diffeomorphism invariance, so that dilaton fluctuations can be gauged away completely and eaten by the metric. More specifically, the warped volume modulus and the dilaton are not independent, but combine into a single gauge-invariant degree of freedom in the lower dimensional effective theory, the warped breathing mode. This occurs for all strengths of the warping, even the weakly warped limit. This warped breathing mode appears as a natural zero mode deformation of backgrounds sourced by p-branes and affects the identification of the independent degrees of freedom of flux compactifications.
Time Warp Operating System (TWOS)
NASA Technical Reports Server (NTRS)
Bellenot, Steven F.
1993-01-01
Designed to support parallel discrete-event simulation, TWOS is complete implementation of Time Warp mechanism - distributed protocol for virtual time synchronization based on process rollback and message annihilation.
Time-Warped Geodesic Regression
Hong, Yi; Singh, Nikhil; Kwitt, Roland; Niethammer, Marc
2016-01-01
We consider geodesic regression with parametric time-warps. This allows, for example, to capture saturation effects as typically observed during brain development or degeneration. While highly-flexible models to analyze time-varying image and shape data based on generalizations of splines and polynomials have been proposed recently, they come at the cost of substantially more complex inference. Our focus in this paper is therefore to keep the model and its inference as simple as possible while allowing to capture expected biological variation. We demonstrate that by augmenting geodesic regression with parametric time-warp functions, we can achieve comparable flexibility to more complex models while retaining model simplicity. In addition, the time-warp parameters provide useful information of underlying anatomical changes as demonstrated for the analysis of corpora callosa and rat calvariae. We exemplify our strategy for shape regression on the Grassmann manifold, but note that the method is generally applicable for time-warped geodesic regression. PMID:25485368
Csaki, Csaba; Grossman, Yuval; Tanedo, Philip; Tsai, Yuhsin
2011-04-01
We present an analysis of the loop-induced magnetic dipole operator in the Randall-Sundrum model of a warped extra dimension with anarchic bulk fermions and an IR brane-localized Higgs. These operators are finite at one-loop order and we explicitly calculate the branching ratio for {mu}{yields}e{gamma} using the mixed position/momentum space formalism. The particular bound on the anarchic Yukawa and Kaluza-Klein (KK) scales can depend on the flavor structure of the anarchic matrices. It is possible for a generic model to either be ruled out or unaffected by these bounds without any fine-tuning. We quantify how these models realize this surprising behavior. We also review tree-level lepton flavor bounds in these models and show that these are on the verge of tension with the {mu}{yields}e{gamma} bounds from typical models with a 3 TeV Kaluza-Klein scale. Further, we illuminate the nature of the one-loop finiteness of these diagrams and show how to accurately determine the degree of divergence of a five-dimensional loop diagram using both the five-dimensional and KK formalism. This power counting can be obfuscated in the four-dimensional Kaluza-Klein formalism and we explicitly point out subtleties that ensure that the two formalisms agree. Finally, we remark on the existence of a perturbative regime in which these one-loop results give the dominant contribution.
NASA Astrophysics Data System (ADS)
Detournay, Stéphane; Hartman, Thomas; Hofman, Diego M.
2012-12-01
We study field theories in two spacetime dimensions invariant under a chiral scaling symmetry that acts only on right-movers. The local symmetries include one copy of the Virasoro algebra and a U(1) current algebra. This differs from the two-dimensional conformal group but in some respects is equally powerful in constraining the theory. In particular, the symmetries on a torus lead to modular covariance of the partition function, which is used to derive a universal formula for the asymptotic density of states. For an application we turn to the holographic description of black holes in quantum gravity, motivated by the fact that the symmetries in the near-horizon geometry of any extremal black hole are identical to those of a two-dimensional field theory with chiral scaling. We consider two examples: black holes in warped AdS3 in topologically massive gravity and in string theory. In both cases, the density of states in the two-dimensional field theory reproduces the Bekenstein-Hawking entropy of black holes in the gravity theory.
Wireless Augmented Reality Prototype (WARP)
NASA Technical Reports Server (NTRS)
Devereaux, A. S.
1999-01-01
Initiated in January, 1997, under NASA's Office of Life and Microgravity Sciences and Applications, the Wireless Augmented Reality Prototype (WARP) is a means to leverage recent advances in communications, displays, imaging sensors, biosensors, voice recognition and microelectronics to develop a hands-free, tetherless system capable of real-time personal display and control of computer system resources. Using WARP, an astronaut may efficiently operate and monitor any computer-controllable activity inside or outside the vehicle or station. The WARP concept is a lightweight, unobtrusive heads-up display with a wireless wearable control unit. Connectivity to the external system is achieved through a high-rate radio link from the WARP personal unit to a base station unit installed into any system PC. The radio link has been specially engineered to operate within the high- interference, high-multipath environment of a space shuttle or space station module. Through this virtual terminal, the astronaut will be able to view and manipulate imagery, text or video, using voice commands to control the terminal operations. WARP's hands-free access to computer-based instruction texts, diagrams and checklists replaces juggling manuals and clipboards, and tetherless computer system access allows free motion throughout a cabin while monitoring and operating equipment.
Cultural Warping of Childbirth, Revisited
Budin, Wendy C.
2007-01-01
In this column, the editor of The Journal of Perinatal Education revisits Doris Haire's classic 1972 article, “The Cultural Warping of Childbirth,” and describes the birth culture of today. The editor also describes the contents of this issue, which offer a broad range of resources, research, and inspiration for childbirth educators in their efforts to promote normal birth.
Warping the Weak Gravity Conjecture
NASA Astrophysics Data System (ADS)
Kooner, Karta; Parameswaran, Susha; Zavala, Ivonne
2016-08-01
The Weak Gravity Conjecture, if valid, rules out simple models of Natural Inflation by restricting their axion decay constant to be sub-Planckian. We revisit stringy attempts to realise Natural Inflation, with a single open string axionic inflaton from a probe D-brane in a warped throat. We show that warped geometries can allow the requisite super-Planckian axion decay constant to be achieved, within the supergravity approximation and consistently with the Weak Gravity Conjecture. Preliminary estimates of the brane backreaction suggest that the probe approximation may be under control. However, there is a tension between large axion decay constant and high string scale, where the requisite high string scale is difficult to achieve in all attempts to realise large field inflation using perturbative string theory. We comment on the Generalized Weak Gravity Conjecture in the light of our results.
NASA Astrophysics Data System (ADS)
González-Díaz, Pedro F.
2000-08-01
In this paper the problem of the quantum stability of the two-dimensional warp drive spacetime moving with an apparent faster than light velocity is considered. We regard as a maximum extension beyond the event horizon of that spacetime its embedding in a three-dimensional Minkowskian space with the topology of the corresponding Misner space. It is obtained that the interior of the spaceship bubble becomes then a multiply connected nonchronal region with closed spacelike curves and that the most natural vacuum allows quantum fluctuations which do not induce any divergent behavior of the renormalized stress-energy tensor, even on the event (Cauchy) chronology horizon. In such a case, the horizon encloses closed timelike curves only at scales close to the Planck length, so that the warp drive satisfies Ford's negative energy-time inequality. Also found is a connection between the superluminal two-dimensional warp drive space and two-dimensional gravitational kinks. This connection allows us to generalize the considered Alcubierre metric to a standard, nonstatic metric which is only describable on two different coordinate patches.
Atlas warping for brain morphometry
NASA Astrophysics Data System (ADS)
Machado, Alexei M. C.; Gee, James C.
1998-06-01
In this work, we describe an automated approach to morphometry based on spatial normalizations of the data, and demonstrate its application to the analysis of gender differences in the human corpus callosum. The purpose is to describe a population by a reduced and representative set of variables, from which a prior model can be constructed. Our approach is rooted in the assumption that individual anatomies can be considered as quantitative variations on a common underlying qualitative plane. We can therefore imagine that a given individual's anatomy is a warped version of some referential anatomy, also known as an atlas. The spatial warps which transform a labeled atlas into anatomic alignment with a population yield immediate knowledge about organ size and shape in the group. Furthermore, variation within the set of spatial warps is directly related to the anatomic variation among the subjects. Specifically, the shape statistics--mean and variance of the mappings--for the population can be calculated in a special basis, and an eigendecomposition of the variance performed to identify the most significant modes of shape variation. The results obtained with the corpus callosum study confirm the existence of substantial anatomical differences between males and females, as reported in previous experimental work.
ERIC Educational Resources Information Center
Brittain, Sarah; Glowacki, Pietrek; Van Ittersum, Jared; Johnson, Lynn
2006-01-01
At some point in their educations, students must learn copious amounts of information. To do this, they use a variety of well-known strategies such as study groups, note-taking services, and videotapes of lectures. In fall 2004, a group of first-year dental students at the University of Michigan (U-M) School of Dentistry asked to have all dental…
Improving Your Lecturing. Revised.
ERIC Educational Resources Information Center
Diamond, Nancy A.; And Others
A guide for faculty who want to improve their lecturing skills is presented. After identifying advantages and disadvantages of the lecture method, suggestions are offered for effective lecture preparation, with attention to organizing the body of the lecture, and beginning and closing the lecture. Vocal aspects of lecture delivery are addressed,…
Warped circumbinary disks in active galactic nuclei
Hayasaki, Kimitake; Sohn, Bong Won; Jung, Taehyun; Zhao, Guangyao; Okazaki, Atsuo T.; Naito, Tsuguya
2014-07-20
We study a warping instability of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on a circular orbit. Such a circumbinary disk is subject to not only tidal torques due to the binary gravitational potential but also radiative torques due to radiation emitted from an accretion disk around each black hole. We find that a circumbinary disk initially aligned with the binary orbital plane is unstable to radiation-driven warping beyond the marginally stable warping radius, which is sensitive to both the ratio of vertical to horizontal shear viscosities and the mass-to-energy conversion efficiency. As expected, the tidal torques give no contribution to the growth of warping modes but tend to align the circumbinary disk with the orbital plane. Since the tidal torques can suppress the warping modes in the inner part of circumbinary disk, the circumbinary disk starts to be warped at radii larger than the marginally stable warping radius. If the warping radius is of the order of 0.1 pc, a resultant semi-major axis is estimated to be of the order of 10{sup –2} pc to 10{sup –4} pc for 10{sup 7} M{sub ☉} black hole. We also discuss the possibility that the central objects of observed warped maser disks in active galactic nuclei are binary supermassive black holes with a triple disk: two accretion disks around the individual black holes and one circumbinary disk surrounding them.
Warp Drive - From Imagination to Reality
NASA Astrophysics Data System (ADS)
Gardiner, J.
The realisation of warp drive is far beyond current science and technology; nevertheless, setting out a timetable for the realisation of warp drive is instructive as this will set expectations for the progress of future research. It is proposed that a time scale for the realisation of warp drive can be estimated by historical analogy with the development of manned space travel to the Moon, using conventional project estimation techniques. A timeline for space travel to the Moon begins with Cyrano de Bergerac's Voyage dans la Lune in 1657 and culminates with the Apollo 11 Moon landing in 1969, a little over 300 years later. A similar timeline for warp drive begins with John W. Campbell's novel Islands of Space in 1930. Fictional conjecture on the warp drive has given way to serious scientific speculation following publication of Alcubierre's seminal warp drive paper in 1994. It is concluded that the realisation of warp drive might be achieved around the year 2180. A projected timetable for the realisation of warp drive through phases of conjecture , speculation , science , technology and application suggests that the warp drive proposal should enter the science phase around the year 2030.
The unphysical nature of `warp drive'
NASA Astrophysics Data System (ADS)
Pfenning, M. J.; Ford, L. H.
1997-07-01
We will apply the quantum-inequality-type restrictions to Alcubierre's warp drive metric on a scale in which a local region of spacetime can be considered `flat'. These are inequalities that restrict the magnitude and extent of the negative energy which is needed to form the warp drive metric. From this we are able to place limits on the parameters of the `warp bubble'. It will be shown that the bubble wall thickness is on the order of only a few hundred Planck lengths. Then we will show that the total integrated energy density needed to maintain the warp metric with such thin walls is physically unattainable.
Warped Circumbinary Disks in Active Galactic Nuclei
NASA Astrophysics Data System (ADS)
Hayasaki, Kimitake; Sohn, Bong Won; Okazaki, Atsuo T.; Jung, Taehyun; Zhao, Guangyao; Naito, Tsuguya
2014-07-01
We study a warping instability of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on a circular orbit. Such a circumbinary disk is subject to not only tidal torques due to the binary gravitational potential but also radiative torques due to radiation emitted from an accretion disk around each black hole. We find that a circumbinary disk initially aligned with the binary orbital plane is unstable to radiation-driven warping beyond the marginally stable warping radius, which is sensitive to both the ratio of vertical to horizontal shear viscosities and the mass-to-energy conversion efficiency. As expected, the tidal torques give no contribution to the growth of warping modes but tend to align the circumbinary disk with the orbital plane. Since the tidal torques can suppress the warping modes in the inner part of circumbinary disk, the circumbinary disk starts to be warped at radii larger than the marginally stable warping radius. If the warping radius is of the order of 0.1 pc, a resultant semi-major axis is estimated to be of the order of 10-2 pc to 10-4 pc for 107 M ⊙ black hole. We also discuss the possibility that the central objects of observed warped maser disks in active galactic nuclei are binary supermassive black holes with a triple disk: two accretion disks around the individual black holes and one circumbinary disk surrounding them.
Fundamental limitations on 'warp drive' spacetimes
NASA Astrophysics Data System (ADS)
Lobo, Francisco S. N.; Visser, Matt
2004-12-01
'Warp drive' spacetimes are useful as 'gedanken-experiments' that force us to confront the foundations of general relativity, and among other things, to precisely formulate the notion of 'superluminal' communication. After carefully formulating the Alcubierre and Natário warp drive spacetimes, and verifying their non-perturbative violation of the classical energy conditions, we consider a more modest question and apply linearized gravity to the weak-field warp drive, testing the energy conditions to first and second orders of the warp-bubble velocity, v. Since we take the warp-bubble velocity to be non-relativistic, v Lt c, we are not primarily interested in the 'superluminal' features of the warp drive. Instead we focus on a secondary feature of the warp drive that has not previously been remarked upon—the warp drive (if it could be built) would be an example of a 'reaction-less drive'. For both the Alcubierre and Natário warp drives we find that the occurrence of significant energy condition violations is not just a high-speed effect, but that the violations persist even at arbitrarily low speeds. A particularly interesting feature of this construction is that it is now meaningful to think of placing a finite mass spaceship at the centre of the warp bubble, and then see how the energy in the warp field compares with the mass energy of the spaceship. There is no hope of doing this in Alcubierre's original version of the warp field, since by definition the point at the centre of the warp bubble moves on a geodesic and is 'massless'. That is, in Alcubierre's original formalism and in the Natário formalism the spaceship is always treated as a test particle, while in the linearized theory we can treat the spaceship as a finite mass object. For both the Alcubierre and Natário warp drives we find that even at low speeds the net (negative) energy stored in the warp fields must be a significant fraction of the mass of the spaceship.
Hydrodynamic instability in warped astrophysical discs
NASA Astrophysics Data System (ADS)
Ogilvie, Gordon I.; Latter, Henrik N.
2013-08-01
Warped astrophysical discs are usually treated as laminar viscous flows, which have anomalous properties when the disc is nearly Keplerian and the viscosity is small: fast horizontal shearing motions and large torques are generated, which cause the warp to evolve rapidly, in some cases at a rate that is inversely proportional to the viscosity. However, these flows are often subject to a linear hydrodynamic instability, which may produce small-scale turbulence and modify the large-scale dynamics of the disc. We use a warped shearing sheet to compute the oscillatory laminar flows in a warped disc and to analyse their linear stability by the Floquet method. We find widespread hydrodynamic instability deriving from the parametric resonance of inertial waves. Even very small, unobservable warps in nearly Keplerian discs of low viscosity can be expected to generate hydrodynamic turbulence, or at least wave activity, by this mechanism.
Design of Warped Stretch Transform.
Mahjoubfar, Ata; Chen, Claire Lifan; Jalali, Bahram
2015-01-01
Time stretch dispersive Fourier transform enables real-time spectroscopy at the repetition rate of million scans per second. High-speed real-time instruments ranging from analog-to-digital converters to cameras and single-shot rare-phenomena capture equipment with record performance have been empowered by it. Its warped stretch variant, realized with nonlinear group delay dispersion, offers variable-rate spectral domain sampling, as well as the ability to engineer the time-bandwidth product of the signal's envelope to match that of the data acquisition systems. To be able to reconstruct the signal with low loss, the spectrotemporal distribution of the signal spectrum needs to be sparse. Here, for the first time, we show how to design the kernel of the transform and specifically, the nonlinear group delay profile dictated by the signal sparsity. Such a kernel leads to smart stretching with nonuniform spectral resolution, having direct utility in improvement of data acquisition rate, real-time data compression, and enhancement of ultrafast data capture accuracy. We also discuss the application of warped stretch transform in spectrotemporal analysis of continuous-time signals. PMID:26602458
Design of Warped Stretch Transform
Mahjoubfar, Ata; Chen, Claire Lifan; Jalali, Bahram
2015-01-01
Time stretch dispersive Fourier transform enables real-time spectroscopy at the repetition rate of million scans per second. High-speed real-time instruments ranging from analog-to-digital converters to cameras and single-shot rare-phenomena capture equipment with record performance have been empowered by it. Its warped stretch variant, realized with nonlinear group delay dispersion, offers variable-rate spectral domain sampling, as well as the ability to engineer the time-bandwidth product of the signal’s envelope to match that of the data acquisition systems. To be able to reconstruct the signal with low loss, the spectrotemporal distribution of the signal spectrum needs to be sparse. Here, for the first time, we show how to design the kernel of the transform and specifically, the nonlinear group delay profile dictated by the signal sparsity. Such a kernel leads to smart stretching with nonuniform spectral resolution, having direct utility in improvement of data acquisition rate, real-time data compression, and enhancement of ultrafast data capture accuracy. We also discuss the application of warped stretch transform in spectrotemporal analysis of continuous-time signals. PMID:26602458
Design of Warped Stretch Transform
NASA Astrophysics Data System (ADS)
Mahjoubfar, Ata; Chen, Claire Lifan; Jalali, Bahram
2015-11-01
Time stretch dispersive Fourier transform enables real-time spectroscopy at the repetition rate of million scans per second. High-speed real-time instruments ranging from analog-to-digital converters to cameras and single-shot rare-phenomena capture equipment with record performance have been empowered by it. Its warped stretch variant, realized with nonlinear group delay dispersion, offers variable-rate spectral domain sampling, as well as the ability to engineer the time-bandwidth product of the signal’s envelope to match that of the data acquisition systems. To be able to reconstruct the signal with low loss, the spectrotemporal distribution of the signal spectrum needs to be sparse. Here, for the first time, we show how to design the kernel of the transform and specifically, the nonlinear group delay profile dictated by the signal sparsity. Such a kernel leads to smart stretching with nonuniform spectral resolution, having direct utility in improvement of data acquisition rate, real-time data compression, and enhancement of ultrafast data capture accuracy. We also discuss the application of warped stretch transform in spectrotemporal analysis of continuous-time signals.
Disk Galaxy Warp Formation via Close Encounters
NASA Astrophysics Data System (ADS)
Kim, Jeonghwan; Peirani, S.; Kim, S.; Yoon, S.
2012-01-01
Warped disks appear to be ubiquitous among spiral galaxies. We present a new scenario for the warp formation, in which galactic fly-by encounters are main drivers of the warp structure. Based on N-body simulation using a publicly available code Gadget2, we investigate morphological and kinematical structures of disk galaxies while the galaxies are undergoing fly-by encounters with adjacent dark matter halos. In this study, we find that warps can be excited by impulsive encounters and sustained for a few billion years. We also find that encounters cause the initially spherical halos to deform into intricate shape halos at the inner regions where warps are generated. Most of the warps from the simulation show inclination angles that are comparable to the observations. The creation of warps, their inclination and their lifetimes are governed primarily by the following three parameters: the impact parameter (the minimum distance between two halos), the mass ratio between two galaxies, and the incoming angle of the intruder. We discuss pros and cons about our alternative scenario in comparison with existing explanations.
Decaying hidden dark matter in warped compactification
Chen, Xingang
2009-09-01
The recent PAMELA and ATIC/Fermi/HESS experiments have observed an excess of electrons and positrons, but not anti-protons, in the high energy cosmic rays. To explain this result, we construct a decaying hidden dark matter model in string theory compactification that incorporates the following two ingredients, the hidden dark matter scenario in warped compactification and the phenomenological proposal of hidden light particles that decay to the Standard Model. In this model, on higher dimensional warped branes, various warped Kaluza-Klein particles and the zero-mode of gauge field play roles of the hidden dark matter or mediators to the Standard Model.
NASA Astrophysics Data System (ADS)
Obousy, R. K.; Cleaver, G.
Certain classes of higher dimensional models suggest that the Casimir Effect is a candidate for the cosmological constant. In this paper we demonstrate that a sufficiently advanced civilization could, in principal, manipulate the radius of the extra dimension to locally adjust the value of the cosmological constant. This adjustment could be tuned to generate an expansion/ contraction of spacetime around a spacecraft creating an exotic form of field-propulsion. Due to the fact that spacetime expansion itself is not restricted by relativity, a faster-than-light `warp drive' could be created. Calculations of the energy requirements of such a drive are performed and an `ultimate' speed limit, based on the Planckian limits on the size of the extra dimensions is found.
Thermal excitations of warped membranes.
Košmrlj, Andrej; Nelson, David R
2014-02-01
We explore thermal fluctuations of thin planar membranes with a frozen spatially varying background metric and a shear modulus. We focus on a special class of D-dimensional "warped membranes" embedded in a d-dimensional space with d ≥ D + 1 and a preferred height profile characterized by quenched random Gaussian variables {h(α)(q)}, α = D + 1,...,d, in Fourier space with zero mean and a power-law variance h(α)(q(1))h(β)(q(2)) ∼ δ(α,β)δ(q(1),-q(2))q(1)(-d(h)). The case D = 2, d = 3, with d(h) = 4 could be realized by flash-polymerizing lyotropic smectic liquid crystals. For D < max{4,d(h)} the elastic constants are nontrivially renormalized and become scale dependent. Via a self-consistent screening approximation we find that the renormalized bending rigidity increases for small wave vectors q as κ(R) ∼ q(-η(f)), while the in-hyperplane elastic constants decrease according to λ(R),μ(R) ∼ q(+η(u)). The quenched background metric is relevant (irrelevant) for warped membranes characterized by exponent d(h) > 4-η(f)((F)) (d(h) < 4-η(f)((F))), where η(f)((F)) is the scaling exponent for tethered surfaces with a flat background metric, and the scaling exponents are related through η(u) + η(f) = d(h) -D (η(u) + 2η(f) = 4-D). PMID:25353441
Hydrodynamics in type B warped spacetimes
Carot, J.; Nunez, L.A.
2005-10-15
We discuss certain general features of type B warped spacetimes which have important consequences on the material content they may admit and its associated dynamics. We show that, for warped B spacetimes, if shear and anisotropy are nonvanishing, they have to be proportional. We also study some of the physics related to the warping factor and of the underlying decomposable metric. Finally we explore the only possible cases compatible with a type B warped geometry which satisfy the dominant energy conditions. As an example of the above mentioned consequences we consider a radiating fluid and two nonspherically symmetric metrics which depend upon an arbitrary parameter a, such that for a=0 spherical symmetry is recovered.
Warped Disks and Inclined Rings around Galaxies
NASA Astrophysics Data System (ADS)
Casertano, Stefano; Sackett, Penny D.; Briggs, Franklin H.
2006-11-01
Preface; Acknowledgements; Workshop participants; Group photograph; 1. The intergalactic HI supply F. Briggs; 2. Neutral gas infall into NGC 628 J. Kamphuis and F. Briggs; 3. VLA HI observations of the radio galaxy Centaurus A J. M. van der Hulst, J. H. van Gorkom, A. D. Haschick and A. D. Tubbs; 4. A geometric model for the dust-band of Centaurus A R. A. Nicholson, K. Taylor and J. Bland; 5. The circumgalactic ring of gas in Leo S. E. Schneider; 6. Using gas kinematics to measure M/L in elliptical galaxies T. de Zeeuw; 7. Velocity fields of disks in triaxial potentials P. J. Teuben; 8. Modeling the atomic gas in NGC 4278 J. F. Lees; 9. A few statistics from the catalog of polar-ring galaxies B. C. Whitmore; 10. Dynamics of polar rings L. S. Sparke; 11. Mergers and the structure of disk galaxies L. Hernquist; 12. Formation of polar rings H.-W. Rix and N. Katz; 13. Gas-dynamical models of settling disks D. Christodoulou and J. E. Tohline; 14. Evolutionary processes affecting galactic accretion disks T. Steiman-Cameron; 15. Particle simulations of polar rings T. Quinn; 16. A bending instability in prolate stellar systems D. Merritt; 17. The Milky Way: lopsided or barred? K. Kuijken; 18. Merger origin of starburst galaxies L. Hernquist; 19. Warped and flaring HI disks A. Bosma; 20. Behaviour of warps in extended disks F. Briggs and J. Kamphuis; 21. Observational constraints for the explanation of warps E. Battaner, E. Florido, M.-L. Sanchez-Saavedra and M. Prieto; 22. Warps in S0s: observations versus theories G. Galletta; 23. Warps and bulges J. Pitesky; 24. Time evolution of galactic warps P. Hofner and L. S. Sparke; 25. Are warps normal modes? S. Casertano; 26. Disk warping in a slewing potential E. C. Ostriker; 27. Concluding discussion Moderator: K. C. Freeman; Name index; Object index; Subject index.
Warped Disks and Inclined Rings around Galaxies
NASA Astrophysics Data System (ADS)
Casertano, Stefano; Sackett, Penny D.; Briggs, Franklin H.
1991-05-01
Preface; Acknowledgements; Workshop participants; Group photograph; 1. The intergalactic HI supply F. Briggs; 2. Neutral gas infall into NGC 628 J. Kamphuis and F. Briggs; 3. VLA HI observations of the radio galaxy Centaurus A J. M. van der Hulst, J. H. van Gorkom, A. D. Haschick and A. D. Tubbs; 4. A geometric model for the dust-band of Centaurus A R. A. Nicholson, K. Taylor and J. Bland; 5. The circumgalactic ring of gas in Leo S. E. Schneider; 6. Using gas kinematics to measure M/L in elliptical galaxies T. de Zeeuw; 7. Velocity fields of disks in triaxial potentials P. J. Teuben; 8. Modeling the atomic gas in NGC 4278 J. F. Lees; 9. A few statistics from the catalog of polar-ring galaxies B. C. Whitmore; 10. Dynamics of polar rings L. S. Sparke; 11. Mergers and the structure of disk galaxies L. Hernquist; 12. Formation of polar rings H.-W. Rix and N. Katz; 13. Gas-dynamical models of settling disks D. Christodoulou and J. E. Tohline; 14. Evolutionary processes affecting galactic accretion disks T. Steiman-Cameron; 15. Particle simulations of polar rings T. Quinn; 16. A bending instability in prolate stellar systems D. Merritt; 17. The Milky Way: lopsided or barred? K. Kuijken; 18. Merger origin of starburst galaxies L. Hernquist; 19. Warped and flaring HI disks A. Bosma; 20. Behaviour of warps in extended disks F. Briggs and J. Kamphuis; 21. Observational constraints for the explanation of warps E. Battaner, E. Florido, M.-L. Sanchez-Saavedra and M. Prieto; 22. Warps in S0s: observations versus theories G. Galletta; 23. Warps and bulges J. Pitesky; 24. Time evolution of galactic warps P. Hofner and L. S. Sparke; 25. Are warps normal modes? S. Casertano; 26. Disk warping in a slewing potential E. C. Ostriker; 27. Concluding discussion Moderator: K. C. Freeman; Name index; Object index; Subject index.
New Lower Bounds for Warp Drive Energy
NASA Astrophysics Data System (ADS)
Gauthier, C.; Gravel, P.; Melanson, J.
The introduction of the warp drive metric by Alcubierre1 has aroused great interest over the past few years. Using an uncertainty-type principle, Ford and Pfenning2 proved that the warp drive transport of a spaceship in a regular bubble having a radius of 100 m is unrealistic. However, Van Den Broeck3 has shown that the situation largely improves when one uses a warp drive bubble with a small surface area and large spatial volume. Putting aside many physics problems related to the realization of the warp drive concept, we show in this paper4 how to modify Van Den Broeck's idea to improve his results. We find new lower bounds for the warp drive energy by working on parameters whose latitude has never been considered before. We also consider micro warp drive bubbles which can be treated as physical entities of their own and could possibly be used to transmit information faster than the speed of light. The conditions prevailing just after the Big Bang allow the spontaneous formation of such micro bubbles which could still be present in our period of time.
Diphoton portal to warped gravity
NASA Astrophysics Data System (ADS)
Falkowski, Adam; Kamenik, Jernej F.
2016-07-01
The diphoton excess around mX=750 GeV observed by ATLAS and CMS can be interpreted as coming from a massive spin-2 excitation. We explore this possibility in the context of warped five-dimensional models with the Standard Model (SM) fields propagating in the bulk of the extra dimension. The 750 GeV resonance is identified with the first Kaluza-Klein (KK) excitation of the five-dimensional graviton that is parametrically lighter than KK resonances of SM fields. Our setup makes it possible to realize nonuniversal couplings of the spin-2 resonance to matter, and thus to explain nonobservation of the 750 GeV resonance in leptonic channels. Phenomenological predictions of the model depend on the localization of fields in the extra dimension. If, as required by naturalness arguments, the zero modes of the Higgs and top fields are localized near the IR brane, one expects large branching fractions to t t ¯, h h , W+W- and Z Z final states. Decays to Z γ can also be observable when the KK graviton couplings to the SM gauge fields are nonuniversal.
Observing the geometry of warped compactification via cosmic inflation.
Shiu, Gary; Underwood, Bret
2007-02-01
Using Dirac-Born-Infeld inflation as an example, we demonstrate that the detailed geometry of warped compactification can leave an imprint on the cosmic microwave background. We compute cosmic microwave background observables for Dirac-Born-Infeld inflation in a generic class of warped throats and find that the results (such as the sign of the tilt of the scalar perturbations and its running) depend sensitively on the precise shape of the warp factor. In particular, we analyze the warped deformed conifold and find that the results can differ from those of other warped geometries, even when these geometries approximate well the exact metric of the warped deformed conifold. PMID:17358841
Density of States for Warped Energy Bands
Mecholsky, Nicholas A.; Resca, Lorenzo; Pegg, Ian L.; Fornari, Marco
2016-01-01
Warping of energy bands can affect the density of states (DOS) in ways that can be large or subtle. Despite their potential for significant practical impacts on materials properties, these effects have not been rigorously demonstrated previously. Here we rectify this using an angular effective mass formalism that we have developed. To clarify the often confusing terminology in this field, “band warping” is precisely defined as pertaining to any multivariate energy function E(k) that does not admit a second-order differential at an isolated critical point in k-space, which we clearly distinguish from band non-parabolicity. We further describe band “corrugation” as a qualitative form of band warping that increasingly deviates from being twice differentiable at an isolated critical point. These features affect the density-of-states and other parameters ascribed to band warping in various ways. We demonstrate these effects, providing explicit calculations of DOS and their effective masses for warped energy dispersions originally derived by Kittel and others. Other physical and mathematical examples are provided to demonstrate fundamental distinctions that must be drawn between DOS contributions that originate from band warping and contributions that derive from band non-parabolicity. For some non-degenerate bands in thermoelectric materials, this may have profound consequences of practical interest. PMID:26905029
Density of States for Warped Energy Bands
NASA Astrophysics Data System (ADS)
Mecholsky, Nicholas A.; Resca, Lorenzo; Pegg, Ian L.; Fornari, Marco
2016-02-01
Warping of energy bands can affect the density of states (DOS) in ways that can be large or subtle. Despite their potential for significant practical impacts on materials properties, these effects have not been rigorously demonstrated previously. Here we rectify this using an angular effective mass formalism that we have developed. To clarify the often confusing terminology in this field, “band warping” is precisely defined as pertaining to any multivariate energy function E(k) that does not admit a second-order differential at an isolated critical point in k-space, which we clearly distinguish from band non-parabolicity. We further describe band “corrugation” as a qualitative form of band warping that increasingly deviates from being twice differentiable at an isolated critical point. These features affect the density-of-states and other parameters ascribed to band warping in various ways. We demonstrate these effects, providing explicit calculations of DOS and their effective masses for warped energy dispersions originally derived by Kittel and others. Other physical and mathematical examples are provided to demonstrate fundamental distinctions that must be drawn between DOS contributions that originate from band warping and contributions that derive from band non-parabolicity. For some non-degenerate bands in thermoelectric materials, this may have profound consequences of practical interest.
Density of States for Warped or non-Warped Energy Bands
NASA Astrophysics Data System (ADS)
Mecholsky, Nicholas; Resca, Lorenzo; Pegg, Ian; Fornari, Marco
The goal of this talk is to investigate when band warping affects density-of-states effective mass. Further, band ``corrugation,'' a form of band warping referring to energy dispersions that deviate ``more severely'' from being twice-differentiable at isolated critical points, may also correlate in different ways with density-of-states effective masses and other band warping parameters. In this talk, an angular effective mass formalism is developed and used to study the electronic density of states of warped and non-warped energy bands towards an application in thermoelectric transport design. We demonstrate effects of band warping and prove the superiority of the angular effective mass treatment for valence energy bands in cubic materials. We explore examples that can also be critical to precisely distinguish the contributions due to band warping and to band non-parabolicity in non-degenerate bands of thermoelectric materials that have a consequent practical interest. The presenter wished to thank the Vitreous State Laboratory.
Bouncing Brane Cosmologies from Warped String Compactifications
Kachru, Shamit
2002-08-08
We study the cosmology induced on a brane probing a warped throat region in a Calabi-Yau compactification of type IIB string theory. For the case of a BPS D3-brane probing the Klebanov-Strassler warped deformed conifold, the cosmology described by a suitable brane observer is a bouncing, spatially flat Friedmann-Robertson-Walker universe with time-varying Newton's constant, which passes smoothly from a contracting to an expanding phase. In the Klebanov-Tseytlin approximation to the Klebanov-Strassler solution the cosmology would end with a big crunch singularity. In this sense, the warped deformed conifold provides a string theory resolution of a spacelike singularity in the brane cosmology. The four-dimensional effective action appropriate for a brane observer is a simple scalar-tensor theory of gravity. In this description of the physics, a bounce is possible because the relevant energy-momentum tensor can classically violate the null energy condition.
NASA Astrophysics Data System (ADS)
Long, K. F.
The prospects for a realistic engineered warp drive are currently within the realms of scientific speculation. The pioneering paper by Alcubierre has started a new field of research and in a period of a little over a decade has seen some encouraging developments. This has led to a better definition of the problem using the mathematical tools of general relativity and quantum field theory. Many publications now exist which have identified many technical problems and explored realisable solutions. Some of these ideas may one day make warp drive a genuine contender for breaking the interstellar distance barrier - the biggest obstacle towards the potential interaction of interstellar civilizations. This paper will review the current status of the warp drive since the seminal paper and discuss the tremendous theoretical advances that have been made. The problem definition will be considered in the context of the NASA Horizon mission methodology.
Origin of the warped heliospheric current sheet
NASA Astrophysics Data System (ADS)
Wilcox, J. M.; Hoeksema, J. T.; Scherrer, P. H.
1980-08-01
The warped heliospheric current sheet for early 1976 is calculated from the observed photospheric magnetic field by a potential field method. Comparisons with measurements of the interplanetary magnetic field polarity for early 1976 obtained at several locations in the heliosphere by Helios 1, Helios 2, Pioneer 11, and at the earth show a rather detailed agreement between the computed current sheet and the observations. It appears that the large-scale structure of the warped heliospheric current sheet is determined by the structure of the photospheric magnetic field and that 'ballerina skirt' effects may add small scale ripples.
Robert Crease
2010-09-01
Crease presents "Recombinant Science: The Birth of the Relativistic Heavy Ion Collider," a lecture that follows on the 429th Brookhaven Lecture, in which Crease talked about the early history of BNL. Both lectures are part of the ongoing celebration of BNL's 60th anniversary year.
Robert Crease
2007-12-12
Crease presents "Recombinant Science: The Birth of the Relativistic Heavy Ion Collider," a lecture that follows on the 429th Brookhaven Lecture, in which Crease talked about the early history of BNL. Both lectures are part of the ongoing celebration of BNL's 60th anniversary year.
ERIC Educational Resources Information Center
Shellaberger, Donna J.
This manual is designed to help lawyers develop the skills needed to present effective, stimulating continuing legal education (CLE) lectures. It focuses on the particular purpose and nature of CLE lecturing, relationships and interplay of personalities in CLE, commitments and constraints which lecturers should observe, program structure and…
Rollback Hardware For Time Warp Multiprocessor Systems
NASA Technical Reports Server (NTRS)
Robb, Michael J.; Buzzell, Calvin A.
1996-01-01
Rollback Chip (RBC) module is computer circuit board containing special-purpose memory circuits for use in multiprocessor computer system. Designed to help realize speedup potential of parallel processing for simulation of discrete events by use of Time Warp operating system.
Needle bar for warp knitting machines
Hagel, Adolf; Thumling, Manfred
1979-01-01
Needle bar for warp knitting machines with a number of needles individually set into slits of the bar and having shafts cranked to such an extent that the head section of each needle is in alignment with the shaft section accommodated by the slit. Slackening of the needles will thus not influence the needle spacing.
Radiation-Driven Warping. 2; Nonisothermal Disks
NASA Technical Reports Server (NTRS)
Maloney, Philip R.; Begelman, Mitchell C.; Nowak, Michael A.
1998-01-01
Recent work by Pringle and by Maloney, Begelman, & Pringle has shown that geometrically thin, optically thick, accretion disks are unstable to warping driven by radiation torque from the central source. This work was confined to isothermal (i.e., surface density Sigma varies as R(sup -3/2) disks. In this paper we generalize the study of radiation-driven warping to include general power-law surface density distributions, Sigma varies as R(sup -delta).We consider the range from Delta = 3/2 (the isothermal case) to Delta = -3/2, which corresponds to a radiation-pressure-supported disk; this spans the range of surface density distributions likely to be found in real astrophysical disks. In all cases there are an infinite number of zero-crossing solutions (i.e., solutions that cross the equator), which are the physically relevant modes if the outer boundary of the disk is required to lie in a specified plane. However, unlike the isothermal disk, which is the degenerate case, the frequency eigenvalues for Delta does not equal 3/2 are all distinct. In all cases the location of the zero moves outward from the steady state (pure precession) value with increasing growth rate; thus, there is a critical minimum size for unstable disks. Modes with zeros at smaller radii are damped. The critical radius and the steady state precession rate depend only weakly on Delta. An additional analytic solution has been found for Delta = 1. The case Delta = 1 divides the solutions into two qualitatively different regimes. For Delta greater than or equal to 1, the fastest growing modes have maximum warp amplitude, close to the disk outer edge, and the ratio of Beta(sub max) to the warp amplitude at the disk inner edge, Beta(sub o), is much greater than 1. For Delta less than 1, Beta(sub max/Beta(sub o) approximately equals 1, and the warp maximum steadily approaches the origin as Delta decreases. This implies that nonlinear effects must be important if the warp extends to the disk inner edge
Relaxation of Warped Disks: The Case of Pure Hydrodynamics
NASA Astrophysics Data System (ADS)
Sorathia, Kareem A.; Krolik, Julian H.; Hawley, John F.
2013-05-01
Orbiting disks may exhibit bends due to a misalignment between the angular momentum of the inner and outer regions of the disk. We begin a systematic simulational inquiry into the physics of warped disks with the simplest case: the relaxation of an unforced warp under pure fluid dynamics, i.e., with no internal stresses other than Reynolds stress. We focus on the nonlinear regime in which the bend rate is large compared to the disk aspect ratio. When warps are nonlinear, strong radial pressure gradients drive transonic radial motions along the disk's top and bottom surfaces that efficiently mix angular momentum. The resulting nonlinear decay rate of the warp increases with the warp rate and the warp width, but, at least in the parameter regime studied here, is independent of the sound speed. The characteristic magnitude of the associated angular momentum fluxes likewise increases with both the local warp rate and the radial range over which the warp extends; it also increases with increasing sound speed, but more slowly than linearly. The angular momentum fluxes respond to the warp rate after a delay that scales with the square root of the time for sound waves to cross the radial extent of the warp. These behaviors are at variance with a number of the assumptions commonly used in analytic models to describe linear warp dynamics.
Brane modeling in warped extra-dimension
NASA Astrophysics Data System (ADS)
Ahmed, Aqeel; Grzadkowski, Bohdan
2013-01-01
Five-dimensional scenarios with infinitesimally thin branes replaced by appropriate configurations of a scalar field were considered. A possibility of periodic extra dimension was discussed in the presence on non-minimal scalar-gravity coupling and a generalized Gibbons-Kallosh-Linde sum rule was found. In order to avoid constraints imposed by periodicity, a non-compact spacial extra dimension was introduced. A five dimensional model with warped geometry and two thin branes mimicked by a scalar profile was constructed and discussed. In the thin brane limit the model corresponds to a set-up with two positive-tension branes. The presence of two branes allows to address the issue of the hierarchy problem which could be solved by the standard warping of the four dimensional metric provided the Higgs field is properly localized. Stability of the background solution was discussed and verified in the presence of the most general perturbations of the metric and the scalar field.
Entanglement entropy in warped conformal field theories
NASA Astrophysics Data System (ADS)
Castro, Alejandra; Hofman, Diego M.; Iqbal, Nabil
2016-02-01
We present a detailed discussion of entanglement entropy in (1+1)-dimensional Warped Conformal Field Theories (WCFTs). We implement the Rindler method to evaluate entanglement and Renyi entropies for a single interval and along the way we interpret our results in terms of twist field correlation functions. Holographically a WCFT can be described in terms of Lower Spin Gravity, a SL (2, ℝ) × U (1) Chern-Simons theory in three dimensions. We show how to obtain the universal field theory results for entanglement in a WCFT via holography. For the geometrical description of the theory we introduce the concept of geodesic and massive point particles in the warped geometry associated to Lower Spin Gravity. In the Chern-Simons description we evaluate the appropriate Wilson line that captures the dynamics of a massive particle.
Image Stitching with Perspective-Preserving Warping
NASA Astrophysics Data System (ADS)
Xiang, Tianzhu; Xia, Gui-Song; Zhang, Liangpei
2016-06-01
Image stitching algorithms often adopt the global transform, such as homography, and work well for planar scenes or parallax free camera motions. However, these conditions are easily violated in practice. With casual camera motions, variable taken views, large depth change, or complex structures, it is a challenging task for stitching these images. The global transform model often provides dreadful stitching results, such as misalignments or projective distortions, especially perspective distortion. To this end, we suggest a perspective-preserving warping for image stitching, which spatially combines local projective transforms and similarity transform. By weighted combination scheme, our approach gradually extrapolates the local projective transforms of the overlapping regions into the non-overlapping regions, and thus the final warping can smoothly change from projective to similarity. The proposed method can provide satisfactory alignment accuracy as well as reduce the projective distortions and maintain the multi-perspective view. Experimental analysis on a variety of challenging images confirms the efficiency of the approach.
Time evolution of a warped cosmic string
NASA Astrophysics Data System (ADS)
Slagter, Reinoud Jan
2014-06-01
The time evolution of a self-gravitating U(1) cosmic string on a warped five-dimensional (5D) axially symmetric spacetime is numerically investigated. Although cosmic strings are theoretically predicted in four-dimensional (4D) general relativistic models, there is still no observational evidence of their existence. From recent observations of the cosmic microwave background (CMB), it is concluded that these cosmic strings cannot provide a satisfactory explanation for the bulk of density perturbations. They even could not survive inflation. It is conjectured that only in a 5D warped braneworld model there will be observable imprint of these so-called cosmic superstrings on the induced effective 4D brane metric for values of the symmetry breaking scale larger than the grand unified theory (GUT) values. The warp factor makes these strings consistent with the predicted mass per unit length on the brane. However, in a time-dependent setting, it seems that there is a wavelike energy-momentum transfer to infinity on the brane, a high-energy braneworld behavior. This in contrast to earlier results in approximation models. Evidence of this information from the bulk geometry could be found in the gravitational cosmic background radiation via gravitational wave energy-momentum affecting the brane evolution. Fluctuations of the brane when there is a U(1) gauge field present, are comparable with the proposed brane tension fluctuations, or branons, whose relic abundance can be a dark matter candidate. We briefly made a connection with the critical behavior at the threshold of black hole formation found by Choptuik several decades ago in self-gravitating time-dependent scalar field models. The critical distinction between dispersion of the scalar waves and singular behavior fade away when a time-dependent warp factor is present.
Lorentz Violation in Warped Extra Dimensions
Rizzo, Thomas G.; /SLAC
2011-08-11
Higher dimensional theories which address some of the problematic issues of the Standard Model(SM) naturally involve some form of D = 4 + n-dimensional Lorentz invariance violation (LIV). In such models the fundamental physics which leads to, e.g., field localization, orbifolding, the existence of brane terms and the compactification process all can introduce LIV in the higher dimensional theory while still preserving 4-d Lorentz invariance. In this paper, attempting to capture some of this physics, we extend our previous analysis of LIV in 5-d UED-type models to those with 5- d warped extra dimensions. To be specific, we employ the 5-d analog of the SM Extension of Kostelecky et al. which incorporates a complete set of operators arising from spontaneous LIV. We show that while the response of the bulk scalar, fermion and gauge fields to the addition of LIV operators in warped models is qualitatively similar to what happens in the flat 5-d UED case, the gravity sector of these models reacts very differently than in flat space. Specifically, we show that LIV in this warped case leads to a non-zero bulk mass for the 5-d graviton and so the would-be zero mode, which we identify as the usual 4-d graviton, must necessarily become massive. The origin of this mass term is the simultaneous existence of the constant non-zero AdS{sub 5} curvature and the loss of general co-ordinate invariance via LIV in the 5-d theory. Thus warped 5-d models with LIV in the gravity sector are not phenomenologically viable.
Industrial applications of multiaxial warp knit composites
NASA Technical Reports Server (NTRS)
Kaufmann, James R.
1992-01-01
Over the past few years, multiaxial warp knit (MWK) fabrics have made significant inroads into the industrial composites arena. This paper examines the use of MWK fabrics in industrial composite applications. Although the focus is on current applications of MWK fabrics in composites, this paper also discusses the physical properties, advantages and disadvantages of MWK fabrics. The author also offers possibilities for the future of MWK fabrics in the industrial composites arena.
Warp evidence in precessing galactic bar models
NASA Astrophysics Data System (ADS)
Sánchez-Martín, P.; Romero-Gómez, M.; Masdemont, J. J.
2016-04-01
Most galaxies have a warped shape when they are seen edge-on. The reason for this curious form is not completely known so far, so in this work we apply dynamical system tools to contribute to its explanation. Starting from a simple, but realistic model formed by a bar and a disc, we study the effect of a small misalignment between the angular momentum of the system and its angular velocity. To this end, a precession model was developed and considered, assuming that the bar behaves like a rigid body. After checking that the periodic orbits inside the bar continue to be the skeleton of the inner system even after inflicting a precession to the potential, we computed the invariant manifolds of the unstable periodic orbits departing from the equilibrium points at the ends of the bar to find evidence of their warped shapes. As is well known, the invariant manifolds associated with these periodic orbits drive the arms and rings of barred galaxies and constitute the skeleton of these building blocks. Looking at them from a side-on viewpoint, we find that these manifolds present warped shapes like those recognised in observations. Lastly, test particle simulations have been performed to determine how the stars are affected by the applied precession, this way confirming the theoretical results.
KK parity in warped extra dimension
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Falkowski, Adam; Low, Ian; Servant, Géraldine
2008-04-01
We construct models with a Kaluza-Klein (KK) parity in a five-dimensional warped geometry, in an attempt to address the little hierarchy problem present in setups with bulk Standard Model fields. The lightest KK particle (LKP) is stable and can play the role of dark matter. We consider the possibilities of gluing two identical slices of AdS5 in either the UV (IR-UV-IR model) or the IR region (UV-IR-UV model) and discuss the model-building issues as well as phenomenological properties in both cases. In particular, we find that the UV-IR-UV model is not gravitationally stable and that additional mechanisms might be required in the IR-UV-IR model to address flavor issues. Collider signals of the warped KK parity are different from either the conventional warped extra dimension without KK parity, in which the new particles are not necessarily pair-produced, or the KK parity in flat universal extra dimensions, where each KK level is nearly degenerate in mass. Dark matter and collider properties of a TeV mass KK Z gauge boson as the LKP are discussed.
WARPED IONIZED HYDROGEN IN THE GALAXY
Cersosimo, J. C.; Figueroa, N. Santiago; Velez, S. Figueroa; Soto, C. Lozada; Mader, S.; Azcarate, D.
2009-07-01
We report observations of the H166{alpha} ({nu} = 1424.734 MHz) radio recombination line (RRL) emission from the Galactic plane in the longitude range l = 267 deg. - 302 deg. and latitude range b = -3.{sup 0}0 to +1.{sup 0}5. The line emission observed describes the Carina arm in the Galactic azimuth range from {theta} = 260 deg. to 190 deg. The structure is located at negative latitudes with respect to the formal Galactic plane. The observations are combined with RRL data from the first Galactic quadrant. Both quadrants show the signature of the warp for the ionized gas, but an asymmetry of the distribution is noted. In the fourth quadrant, the gas is located between Galactic radii R {approx} 7 and 10 kpc, and the amplitude of the warp is seen from the midplane to z {approx} -150 pc. In the first quadrant, the gas is found between R {approx} 8 and 13-16 kpc, and flares to z {approx} +350 pc. We confirm the warp of the ionized gas near the solar circle. The distribution of the ionized gas is compared with the maximum intensity H I emission (0.30 < n{sub HI} < 0.45 cm{sup -3}) at intervals of the Galactic ring. The ionized material is correlated with the H I maximum intensity in both quadrants, and both components show the same tilted behavior with respect to the mid-Galactic plane.
ERIC Educational Resources Information Center
Nettleship, Lois
Three lectures on law enforcement are presented that were prepared for study purposes at Johnson County Community College. The first lecture examines the fundamental ideas of the Age of Enlightenment and discusses their influence on the American Revolution, the United States Constitution, and the Bill of Rights. Major provisions of the Bill of…
ERIC Educational Resources Information Center
Holt, Charles
If teaching is the effective communication of knowledge, the teacher first must be knowledgeable about the subject being taught. Communicating that knowledge to students is just as important. One standard teaching method is the lecture. A lecture is prepared before class by the teacher and should include not only the facts to be learned by the…
Circular orbits on a warped spandex fabric
NASA Astrophysics Data System (ADS)
Middleton, Chad A.; Langston, Michael
2014-04-01
We present a theoretical and experimental analysis of circular-like orbits made by a marble rolling on a warped spandex fabric. We show that the mass of the fabric interior to the orbital path influences the motion of the marble in a nontrivial way and can even dominate the orbital characteristics. We also compare a Kepler-like expression for such orbits to similar expressions for orbits about a spherically symmetric massive object in the presence of a constant vacuum energy, as described by general relativity.
Characterization of multiaxial warp knit composites
NASA Technical Reports Server (NTRS)
Dexter, H. Benson; Hasko, Gregory H.; Cano, Roberto J.
1991-01-01
The objectives were to characterize the mechanical behavior and damage tolerance of two multiaxial warp knit fabrics to determine the acceptability of these fabrics for high performance composite applications. The tests performed included compression, tension, open hole compression, compression after impact and compression-compression fatigue. Tests were performed on as-fabricated fabrics and on multi-layer fabrics that were stitched together with either carbon or Kevlar stitching yarn. Results of processing studies for vacuum impregnation with Hercules 3501-6 epoxy resin and pressure impregnation with Dow Tactix 138/H41 epoxy resin and British Petroleum BP E905L epoxy resin are presented.
Warped flavor symmetry predictions for neutrino physics
NASA Astrophysics Data System (ADS)
Chen, Peng; Ding, Gui-Jun; Rojas, Alma D.; Vaquera-Araujo, C. A.; Valle, J. W. F.
2016-01-01
A realistic five-dimensional warped scenario with all standard model fields propagating in the bulk is proposed. Mass hierarchies would in principle be accounted for by judicious choices of the bulk mass parameters, while fermion mixing angles are restricted by a Δ(27) flavor symmetry broken on the branes by flavon fields.The latter gives stringent predictions for the neutrino mixing parameters, and the Dirac CP violation phase, all described in terms of only two independent parameters at leading order. The scheme also gives an adequate CKM fit and should be testable within upcoming oscillation experiments.
Alcubierre's warp drive: Problems and prospects
NASA Astrophysics Data System (ADS)
van den Broeck, Chris
2000-01-01
Alcubierre's warp drive geometry seemingly represents the ultimate dream for interstellar travel: there is no speed limit, the passengers are weightless whatever the acceleration, and there is no time dilation. However, in its original form, the proposal suffers from several fatal flaws, such as unreasonably high energies, energy moving in a locally spacelike direction, and a violation of the energy conditions of classical Einstein gravity. I present a possible solution for one of these problems, and I suggest ways to at least soften the others. .
Radio frequency and infrared drying of sized textile warp yarns
Ruddick, H.G. )
1990-11-01
Drying sized textile warp yarns without contacting the warp is easily accomplished by either radio frequency or infrared techniques. Although the process is more expensive than conventional drying, the substantial savings accrued during subsequent weaving and finishing of the cloth can help keep the US textile industry competitive and support electrical load. 5 refs., 8 figs., 14 tabs.
Warp Characteristics of Spiral Galaxies in the Virgo Cluster
NASA Astrophysics Data System (ADS)
Bae, Hyun-Jin; Chung, A.; Kim, S. S.; Jozsa, G. I. G.; Yoon, S.
2012-01-01
We present the warp characteristics of 22 spiral galaxies in the Virgo cluster based on their VLA HI datacubes with unprecedented precision. The tilted-ring modeling method is used to examine kinematic properties of the HI disks including the inclination and position angle. The main results are as follows. First, 17 out of the 19 (89.5 %) successfully-modeled galaxies exhibit either weak or strong warps, indicating that the warps are very common not only galaxies in isolation but ones in dense environments. Second, the warp strength decreases with increasing dynamical mass, supporting the notion that the warps are primarily controlled by dark matter halos. Last, the warp characteristics in our sample are distinct from those of isolated galaxies, in that the warps in our sample varies a great deal in inclination, but little in position angle. This implies that in dense environments, the main driver of the disk warps is most likely the galactic tidal interaction, rather than other explanations such as the cosmic infall scenario.
A non-uniform warping theory for beams
NASA Astrophysics Data System (ADS)
El Fatmi, Rached
2007-08-01
This Note proposes a non-uniform warping beam theory including the effects of torsion and shear forces. Based on a displacement model using three warping parameters associated to three St Venant warping functions corresponding to torsion and shear forces, this theory is free from the classical assumptions on the warpings or on the shears, and is valid for any kind of homogeneous elastic and isotropic cross-section. The result on the structural behavior of the beam specifies the effect of the non-symmetry of the cross-section, and the closed form results obtained for the stresses show the contribution of each internal force. Comparison with St Venant beam theory highlights the additional effects due to the non-uniformity of the warping. To cite this article: R. El Fatmi, C. R. Mecanique 335 (2007).
Warped de Sitter Solutions in the Scalar-Tensor Theory
NASA Astrophysics Data System (ADS)
Flachi, Antonino; Minamitsuji, Masato; Uzawa, Kunihito
2015-01-01
We consider a class of higher dimensional theories consisting of D-dimensional gravity coupled to a scalar dilaton and a form field propagating over a warped higher dimensional spacetime. In the simplest set-up, the models are characterized by two moduli: one related to the volume of the internal space, the other to the modulus of the warp factor. While the volume-modulus can be fixed by appropriately tuning the gauge field strength, curvature of the internal space, and cosmological constant, the same mechanism cannot work for the warp modulus. Here, we will present a stabilizing mechanism for the warp modulus and its mass in terms of quantum fluctuations from both moduli. We will show that, while quantum effects from the modulus associated to the warp modulus can only provide a stabilization mechanism of the mass scale in a restricted region of the parameter space, quantum effects from the volume modulus offer an efficient mechanism of stabilization.
Learning from Online Video Lectures
ERIC Educational Resources Information Center
Brecht, H. David
2012-01-01
This study empirically examines the instructional value of online video lectures--videos that a course's instructor prepares to supplement classroom or online-broadcast lectures. The study examines data from a classroom course, where the videos have a slower, more step-by-step lecture style than the classroom lectures; student use of videos is…
10 Suggestions for Enhancing Lecturing
ERIC Educational Resources Information Center
Heitzmann, Ray
2010-01-01
Criticism of the lecture method remains a staple of discussion and writing in academia--and most of the time it's deserved! Those interested in improving this aspect of their teaching might wish to consider some or all of the following suggestions for enhancing lectures. These include: (1) Lectures must start with a "grabber"; (2) Lectures must be…
DOE R&D Accomplishments Database
Salam, A.
1956-04-01
Lectures with mathematical analysis are given on Dispersion Theory and Causality and Dispersion Relations for Pion-nucleon Scattering. The appendix includes the S-matrix in terms of Heisenberg Operators. (F. S.)
Jason Graetz
2008-02-20
Learn about the pioneering work being done at BNL in the field of hydrogen storage as Jason Graetz of the Energy Sciences & Technology Department presents the 433rd Brookhaven Lecture, "Fueling Up With Hydrogen: New Approaches to Hydrogen Storage."
Broken discs: warp propagation in accretion discs
NASA Astrophysics Data System (ADS)
Nixon, Christopher J.; King, Andrew R.
2012-04-01
We simulate the viscous evolution of an accretion disc around a spinning black hole. In general, any such disc is misaligned, and warped by the Lense-Thirring effect. Unlike previous studies, we use effective viscosities constrained to be consistent with the internal fluid dynamics of the disc. We find that non-linear fluid effects, which reduce the effective viscosities in warped regions, can promote breaking of the disc into two distinct planes. This occurs when the Shakura & Sunyaev dimensionless viscosity parameter α is ≲0.3 and the initial angle of misalignment between the disc and hole is ≳45°. The break can be a long-lived feature, propagating outwards in the disc on the usual alignment time-scale, after which the disc is fully co-aligned or counter-aligned with the hole. Such a break in the disc may be significant in systems where we know the inclination of the outer accretion disc to the line of sight, such as some X-ray binaries: the inner disc, and so any jets, may be noticeably misaligned with respect to the orbital plane.
Warped seesaw mechanism is physically inverted
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Hong, Sungwoo; Vecchi, Luca
2016-07-01
Warped extra dimensions can address both the Planck-weak and flavor hierarchies of the Standard Model (SM). In this paper we discuss the SM neutrino mass generation in a scenario in which a SM singlet bulk fermion—coupled to the Higgs and the lepton doublet near the IR brane—is given a Majorana mass of order the Planck scale on the UV brane. Despite the resemblance to a type I seesaw mechanism, a careful investigation based on the mass basis for the singlet four-dimensional modes reveals a very different picture. Namely, the SM neutrino masses are generated dominantly by the exchange of the TeV-scale mass eigenstates of the singlet, that are pseudo-Dirac and have a sizable Higgs-induced mixing with the SM doublet neutrino; remarkably, in warped five-dimensional (5D) models the anticipated type I seesaw morphs into a natural realization of the so-called "inverse" seesaw. This understanding uncovers an intriguing and direct link between neutrino mass generation (and possibly leptogenesis) and TeV-scale physics. We also perform estimates using the dual conformal field theory picture of our framework, which back up our 5D calculation.
Towards establishing the spin of warped gravitons
NASA Astrophysics Data System (ADS)
Antipin, Oleg; Soni, Amarjit
2008-10-01
We study the possibility of experimental verification of the spin=2 nature of the Kaluza-Klein (KK) graviton which is predicted to exist in the extra-dimensional Randal-Sundrum (RS) warped models. The couplings of these gravitons to the particles located on or near the TeV brane is the strongest as the overlap integral of their profiles in the extra-dimension is large. Among them are unphysical Higgses (W±L and ZL) and KK excitations of the Standard Model (SM) gauge bosons. We consider the possibility to confirm the spin-2 nature of the first KK mode of the warped graviton (G1) based on the angular distribution of the Z bozon in the graviton rest frame in the gg → G1 → WKK(ZKK)W(Z) → WWZ, gg → G1 → ZZ and gg → G1 → ZKKZ → ZZH decay channels. Using Wigner D-matrix properties, we derive the relationship between the graviton spin, signal angular distribution peak value, and other theoretically calculable quantities. We then study the LHC signals for these decay modes and find that with 1000 fb-1 of data, spin of the RS graviton up to ~ 2 TeV may be confirmed in the pp → WKK(ZKK)W(Z) → WWZ → 3 leptons + jet + \\slashed{E}_T and pp → ZZ → 4 leptons decay modes.
NASA's Wireless Augmented Reality Prototype (WARP)
NASA Astrophysics Data System (ADS)
Agan, Martin; Voisinet, Leeann; Devereaux, Ann
1998-01-01
The objective of Wireless Augmented Reality Prototype (WARP) effort is to develop and integrate advanced technologies for real-time personal display of information relevant to the health and safety of space station/shuttle personnel. The WARP effort will develop and demonstrate technologies that will ultimately be incorporated into operational Space Station systems and that have potential earth applications such as aircraft pilot alertness monitoring and in various medical and consumer environments where augmented reality is required. To this end a two phase effort will be undertaken to rapidly develop a prototype (Phase I) and an advanced prototype (Phase II) to demonstrate the following key technology features that could be applied to astronaut internal vehicle activity (IVA) and potentially external vehicle activity (EVA) as well: 1) mobile visualization, and 2) distributed information system access. Specifically, Phase I will integrate a low power, miniature wireless communication link and a commercial biosensor with a head mounted display. The Phase I design will emphasize the development of a relatively small, lightweight, and unobtrusive body worn prototype system. Phase II will put increased effort on miniaturization, power consumption reduction, increased throughput, higher resolution, and ``wire removal'' of the subsystems developed in Phase I.
Symmetric time warping, Boltzmann pair probabilities and functional genomics.
Clote, Peter; Straubhaar, Jürg
2006-07-01
Given two time series, possibly of different lengths, time warping is a method to construct an optimal alignment obtained by stretching or contracting time intervals. Unlike pairwise alignment of amino acid sequences, classical time warping, originally introduced for speech recognition, is not symmetric in the sense that the time warping distance between two time series is not necessarily equal to the time warping distance of the reversal of the time series. Here we design a new symmetric version of time warping, and present a formal proof of symmetry for our algorithm as well as for one of the variants of Aach and Church [1]. We additionally design quadratic time dynamic programming algorithms to compute both the forward and backward Boltzmann partition functions for symmetric time warping, and hence compute the Boltzmann probability that any two time series points are aligned. In the future, with the availability of increasingly long and accurate time series gene expression data, our algorithm can provide a sense of biological significance for aligned time points - e.g. our algorithm could be used to provide evidence that expression values of two genes have higher Boltzmann probability (say) in the G1 and S phase than in G2 and M phases. Algorithms, source code and web interface, developed by the first author, are made publicly available via the Boltzmann Time Warping web server at bioinformatics.bc.edu/clotelab/. PMID:16791652
The WARP Code: Modeling High Intensity Ion Beams
Grote, D P; Friedman, A; Vay, J L; Haber, I
2004-12-09
The Warp code, developed for heavy-ion driven inertial fusion energy studies, is used to model high intensity ion (and electron) beams. Significant capability has been incorporated in Warp, allowing nearly all sections of an accelerator to be modeled, beginning with the source. Warp has as its core an explicit, three-dimensional, particle-in-cell model. Alongside this is a rich set of tools for describing the applied fields of the accelerator lattice, and embedded conducting surfaces (which are captured at sub-grid resolution). Also incorporated are models with reduced dimensionality: an axisymmetric model and a transverse ''slice'' model. The code takes advantage of modern programming techniques, including object orientation, parallelism, and scripting (via Python). It is at the forefront in the use of the computational technique of adaptive mesh refinement, which has been particularly successful in the area of diode and injector modeling, both steady-state and time-dependent. In the presentation, some of the major aspects of Warp will be overviewed, especially those that could be useful in modeling ECR sources. Warp has been benchmarked against both theory and experiment. Recent results will be presented showing good agreement of Warp with experimental results from the STS500 injector test stand. Additional information can be found on the web page http://hif.lbl.gov/theory/WARP{_}summary.html.
DigiWarp: a method for deformable mouse atlas warping to surface topographic data
Joshi, Anand A; Chaudhari, Abhijit J; Li, Changqing; Dutta, Joyita; Cherry, Simon R; Shattuck, David W; Toga, Arthur W; Leahy, Richard M
2011-01-01
For pre-clinical bioluminescence or fluorescence optical tomography, the animal's surface topography and internal anatomy need to be estimated for improving the quantitative accuracy of reconstructed images. The animal's surface profile can be measured by all-optical systems, but estimation of the internal anatomy using optical techniques is non-trivial. A 3D anatomical mouse atlas may be warped to the estimated surface. However, fitting an atlas to surface topography data is challenging because of variations in the posture and morphology of imaged mice. In addition, acquisition of partial data (for example, from limited views or with limited sampling) can make the warping problem ill-conditioned. Here, we present a method for fitting a deformable mouse atlas to surface topographic range data acquired by an optical system. As an initialization procedure, we match the posture of the atlas to the posture of the mouse being imaged using landmark constraints. The asymmetric L2 pseudo-distance between the atlas surface and the mouse surface is then minimized in order to register two data sets. A Laplacian prior is used to ensure smoothness of the surface warping field. Once the atlas surface is normalized to match the range data, the internal anatomy is transformed using elastic energy minimization. We present results from performance evaluation studies of our method where we have measured the volumetric overlap between the internal organs delineated directly from MRI or CT and those estimated by our proposed warping scheme. Computed Dice coefficients indicate excellent overlap in the brain and the heart, with fair agreement in the kidneys and the bladder. PMID:20885019
Metamaterial-based model of the Alcubierre warp drive
NASA Astrophysics Data System (ADS)
Smolyaninov, Igor I.
2011-09-01
Electromagnetic metamaterials are capable of emulating many exotic space-time geometries, such as black holes, rotating cosmic strings, and the big bang singularity. This paper presents a metamaterial-based model of the Alcubierre warp drive and studies its limitations due to available range of material parameters. It appears that the material parameter range introduces strong limitations on the achievable “warp speed” so that ordinary magnetoelectric materials cannot be used. However, newly developed “perfect” bianisotropic nonreciprocal magnetoelectric metamaterials should be capable of emulating the physics of warp drive gradually accelerating up to 1/4c.
Some examples of image warping for low vision prosthesis
NASA Technical Reports Server (NTRS)
Juday, Richard D.; Loshin, David S.
1988-01-01
NASA has developed an image processor, the Programmable Remapper, for certain functions in machine vision. The Remapper performs a highly arbitrary geometric warping of an image at video rate. It might ultimately be shrunk to a size and cost that could allow its use in a low-vision prosthesis. Coordinate warpings have been developed for retinitis pigmentosa (tunnel vision) and for maculapathy (loss of central field) that are intended to make best use of the patient's remaining viable retina. The rationales and mathematics are presented for some warpings that we will try in clinical studies using the Remapper's prototype.
Warped Unification, Proton Stability, and Dark Matter
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Servant, Géraldine
2004-12-01
We show that solving the problem of baryon-number violation in nonsupersymmetric grand unified theories (GUT's) in warped higher-dimensional spacetime can lead to a stable Kaluza Klein particle. This exotic particle has gauge quantum numbers of a right-handed neutrino, but carries fractional baryonnumber and is related to the top quark within the higher-dimensional GUT. A combination of baryonnumber and SU(3) color ensures its stability. Its relic density can easily be of the right value for masses in the 10GeV few TeV range. An exciting aspect of these models is that the entire parameter space will be tested at near future dark matter direct detection experiments. Other exotic GUT partners of the top quark are also light and can be produced at high energy colliders with distinctive signatures.
Lectures in accelerator theory
Month, M
1980-01-01
Lecture I deals with the behavior of particles in the nonlinear field arising from the electromagnetic interaction of colliding beams. The case treated, that of counter-rotating proton beams crossing each other at a non-zero angle, has the simple feature that the force between the beam is one dimensional. In lecture II, an analysis of the development of traveling waves on particle beams is presented. The situation studied is that of a uniform beam current in a circular accelerator and the excitation for the coherent motion is induced by the resistivity of the vacuum chamber wall. Finally, in lecture III, a description of the current accumulation process used at the proton storage rings at CERN (The ISR) is given. Particle pulses of rather low average current are injected and stored along the length and width of the vacuum chamber. The efficiency is very high and large currents (over 40 amperes) have been achieved.
Memory for Lectures: How Lecture Format Impacts the Learning Experience
Varao-Sousa, Trish L.; Kingstone, Alan
2015-01-01
The present study investigated what impact the presentation style of a classroom lecture has on memory, mind wandering, and the subjective factors of interest and motivation. We examined if having a professor lecturing live versus on video alters the learning experience of the students in the classroom. During the lectures, students were asked to report mind wandering and later complete a memory test. The lecture format was manipulated such that all the students received two lectures, one live and one a pre-recorded video. Results indicate that lecture format affected memory performance but not mind wandering, with enhanced memory in the live lectures. Additionally, students reported greater interest and motivation in the live lectures. Given that a single change to the classroom environment, professor presence, impacted memory performance, as well as motivation and interest, the present results have several key implications for technology-based integrations into higher education classrooms. PMID:26561235
Memory for Lectures: How Lecture Format Impacts the Learning Experience.
Varao-Sousa, Trish L; Kingstone, Alan
2015-01-01
The present study investigated what impact the presentation style of a classroom lecture has on memory, mind wandering, and the subjective factors of interest and motivation. We examined if having a professor lecturing live versus on video alters the learning experience of the students in the classroom. During the lectures, students were asked to report mind wandering and later complete a memory test. The lecture format was manipulated such that all the students received two lectures, one live and one a pre-recorded video. Results indicate that lecture format affected memory performance but not mind wandering, with enhanced memory in the live lectures. Additionally, students reported greater interest and motivation in the live lectures. Given that a single change to the classroom environment, professor presence, impacted memory performance, as well as motivation and interest, the present results have several key implications for technology-based integrations into higher education classrooms. PMID:26561235
The Lecture Is Dead Long Live the e-Lecture
ERIC Educational Resources Information Center
Folley, Duncan
2010-01-01
This research paper investigates if the traditional lecture is no longer appropriate for Neomillennial Learning Styles and whether an alternative blended approach could/should be used? Over the past decade the lecture as we know it, has gradually been under attack from constructivists, Twigg (1999) for example argues that the lecture is in the…
The Geodesic Motion Near Hypersurfaces in the Warped Products Spacetime
NASA Astrophysics Data System (ADS)
Choi, Jaedong; Kim, Yong-Wan; Park, Young-Jai
2013-09-01
In the framework of Lorentzian multiply warped products we study the Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) spacetime near hypersurfaces in the interior of the event horizon. We also investigate the geodesic motion in hypersurfaces.
Star Trek's Lt. Uhura's Warp-Speed Visit to Dryden
Actress Nichelle Nichols warped to many worlds as Lt. Uhura in the 1960s Star Trek TV show. However, her real-life adventures have taken her to where no one has gone before in advocacy for NASA and...
Accelerating Universes from Compactification on a Warped Conifold
Neupane, Ishwaree P.
2007-02-09
We find a cosmological solution corresponding to the compactification of 10D supergravity on a warped conifold that easily circumvents the ''no-go'' theorem given for a warped or flux compactification, providing new perspectives for the study of supergravity or superstring theory in cosmological backgrounds. With fixed volume moduli of the internal space, the model can explain a physical Universe undergoing an accelerated expansion in the 4D Einstein frame, for a sufficiently long time. The solution found in the limit that the warp factor dependent on the radial coordinate y is extremized (giving a constant warping) is smooth and it supports a flat four-dimensional Friedmann-Robertson-Walker cosmology undergoing a period of accelerated expansion with slowly rolling or stabilized volume moduli.
Accelerating universes from compactification on a warped conifold.
Neupane, Ishwaree P
2007-02-01
We find a cosmological solution corresponding to the compactification of 10D supergravity on a warped conifold that easily circumvents the "no-go" theorem given for a warped or flux compactification, providing new perspectives for the study of supergravity or superstring theory in cosmological backgrounds. With fixed volume moduli of the internal space, the model can explain a physical Universe undergoing an accelerated expansion in the 4D Einstein frame, for a sufficiently long time. The solution found in the limit that the warp factor dependent on the radial coordinate y is extremized (giving a constant warping) is smooth and it supports a flat four-dimensional Friedmann-Robertson-Walker cosmology undergoing a period of accelerated expansion with slowly rolling or stabilized volume moduli. PMID:17358928
Cosmic string dynamics and evolution in warped spacetime
Avgoustidis, A.
2008-07-15
We study the dynamics and evolution of Nambu-Goto strings in a warped spacetime, where the warp factor is a function of the internal coordinates giving rise to a ''throat'' region. The microscopic equations of motion for strings in this background include potential and friction terms, which attract the strings towards the bottom of the warping throat. However, by considering the resulting macroscopic equations for the velocities of strings in the vicinity of the throat, we note the absence of enough classical damping to guarantee that the strings actually reach the warped minimum and stabilize there. Instead, our classical analysis supports a picture in which the strings experience mere deflections and bounces around the tip, rather than strongly damped oscillations. Indeed, 4D Hubble friction is inefficient in the internal dimensions and there is no other classical mechanism known, which could provide efficient damping. These results have potentially important implications for the intercommuting probabilities of cosmic superstrings.
Namaste (counterbalancing) technique: Overcoming warping in costal cartilage
Agrawal, Kapil S.; Bachhav, Manoj; Shrotriya, Raghav
2015-01-01
Background: Indian noses are broader and lack projection as compared to other populations, hence very often need augmentation, that too by large volume. Costal cartilage remains the material of choice in large volume augmentations and repair of complex primary and secondary nasal deformities. One major disadvantage of costal cartilage grafts (CCG) which offsets all other advantages is the tendency to warp and become distorted over a period of time. We propose a simple technique to overcome this menace of warping. Materials and Methods: We present the data of 51 patients of rhinoplasty done using CCG with counterbalancing technique over a period of 4 years. Results: No evidence of warping was found in any patient up to a maximum follow-up period of 4 years. Conclusion: Counterbalancing is a useful technique to overcome the problem of warping. It gives liberty to utilize even unbalanced cartilage safely to provide desired shape and use the cartilage without any wastage. PMID:26424973
Time Warp Operating System, Version 2.5.1
NASA Technical Reports Server (NTRS)
Bellenot, Steven F.; Gieselman, John S.; Hawley, Lawrence R.; Peterson, Judy; Presley, Matthew T.; Reiher, Peter L.; Springer, Paul L.; Tupman, John R.; Wedel, John J., Jr.; Wieland, Frederick P.; Younger, Herbert C.
1993-01-01
Time Warp Operating System, TWOS, is special purpose computer program designed to support parallel simulation of discrete events. Complete implementation of Time Warp software mechanism, which implements distributed protocol for virtual synchronization based on rollback of processes and annihilation of messages. Supports simulations and other computations in which both virtual time and dynamic load balancing used. Program utilizes underlying resources of operating system. Written in C programming language.
Electroweak constraints on warped geometry in five dimensions and beyond
NASA Astrophysics Data System (ADS)
Archer, Paul R.; Huber, Stephan J.
2010-10-01
Here we consider the tree level corrections to electroweak (EW) observables from standard model (SM) particles propagating in generic warped extra dimensions. The scale of these corrections is found to be dominated by three parameters, the Kaluza-Klein (KK) mass scale, the relative coupling of the KK gauge fields to the Higgs and the relative coupling of the KK gauge fields to fermion zero modes. It is found that 5D spaces that resolve the hierarchy problem through warping typically have large gauge-Higgs coupling. It is also found in D> 5 where the additional dimensions are warped the relative gauge-Higgs coupling scales as a function of the warp factor. If the warp factor of the additional spaces is contracting towards the IR brane, both the relative gauge-Higgs coupling and resulting EW corrections will be large. Conversely EW constraints could be reduced by finding a space where the additional dimension’s warp factor is increasing towards the IR brane. We demonstrate that the Klebanov Strassler solution belongs to the former of these possibilities.
Three-dimensional warping registration of the pelvis and prostate
NASA Astrophysics Data System (ADS)
Fei, Baowei; Kemper, Corey; Wilson, David L.
2002-05-01
We are investigating interventional MRI guided radio- frequency (RF) thermal ablation for the minimally invasive treatment of prostate cancer. Among many potential applications of registration, we wish to compare registered MR images acquired before and immediately after RF ablation in order to determine whether a tumor is adequately treated. Warping registration is desired to correct for potential deformations of the pelvic region and movement of the prostate. We created a two-step, three-dimensional (3D) registration algorithm using mutual information and thin plate spline (TPS) warping for MR images. First, automatic rigid body registration was used to capture the global transformation. Second, local warping registration was applied. Interactively placed control points were automatically optimized by maximizing the mutual information of corresponding voxels in small volumes of interest and by using a 3D TPS to express the deformation throughout the image volume. Images were acquired from healthy volunteers in different conditions simulating potential applications. A variety of evaluation methods showed that warping consistently improved registration for volume pairs whenever patient position or condition was purposely changed between acquisitions. A TPS transformation based on 180 control points generated excellent warping throughout the pelvis following rigid body registration. The prostate centroid displacement for a typical volume pair was reduced from 3.4 mm to 0.6 mm when warping was added.
Warped Kaluza-Klein reduction from string duality
NASA Astrophysics Data System (ADS)
Schulz, Michael; Tammaro, Elliott
2014-03-01
Virtually all phenomenologically relevant string theory compactifications are of warped type, in which the overall scale factor of 4D spacetime varies over the internal dimensions. However, the procedure for Kaluza-Klein (KK) reduction is more poorly understood for warped compactifications than for standard compactifications. The simplest standard compactifications are compactifications on tori, and the simplest warped compactifications differ from these by the addition of parallel D-branes and O-branes. It is astonishing that a direct derivation of the dimensionally reduced action does not exist even for these simple warped compactifications (which are T-dual to Type I), although the answer is known on supersymmetry grounds. We fill this void. We derive the procedure for the KK reduction of a simple Type IIA warped compactification with D6 branes and O6 planes, via its lift to the standard compactification of M-theory on K3. Our derivation utilizes an approximate K3 metric of Gibbons-Hawking form, which is exactly equivalent to the classical type IIA supergravity description of the warped compactification. This material is based upon work supported by the National Science Foundation under Grant Nos. PHY09-12219 and PHY11-25915.
Richard Ferrieri
2010-09-01
In this lecture titled "Striving Towards Energy Sustainability: How Will Plants Play a Role in Our Future?" Richard Ferrieri discusses how radiotracers and positron emission tomography (PET imaging) are providing a new look into plant processes that could lead to more renewable biofuels.
Peter Vanier
2010-09-01
With new radiation detectors, finding smuggled nuclear materials in a huge container among thousands of others in a busy port becomes possible. To learn about these new detectors from a specialist who has spent several years developing these technologies, watch the 412th Brookhaven Lecture, "Advanced Neutron Detection Methods: New Tools for Countering Nuclear Terrorism."
David Jaffe
2010-09-01
"The Pesky Neutrino". In this lecture, Jaffe describes the past, present and possible future of the "pesky" neutrino, the existence of which was first hypothesized in 1930 to rescue energy conservation in the radioactive beta decay of nuclei. Recent evidence that neutrinos are massive is the only experimental evidence in particle physics that is inconsistent with the Standard Model.
Mei Bai
2010-09-01
Among other things, scientists at BNL's Relativistic Heavy Ion Collider (RHIC) are studying a fundamental question of particle physics: What is responsible for proton "spin"? Physicist Mei Bai discusses this topic at the 423rd Brookhaven Lecture, "RHIC: The Worlds First High-Energy, Polarized-Proton Collider."
Peter Steinberg
2010-09-01
In a lecture titled "Hotter, Denser, Faster, Smaller...and Nearly Perfect: What's the Matter at RHIC?", Steinberg discusses the basic physics of the quark-gluon plasma and BNL's Relativistic Heavy Ion Collider, with a focus on several intriguing results from RHIC's recently ended PHOBOS experiment.
Richard Ferrieri
2009-10-28
In this lecture titled "Striving Towards Energy Sustainability: How Will Plants Play a Role in Our Future?" Richard Ferrieri discusses how radiotracers and positron emission tomography (PET imaging) are providing a new look into plant processes that could lead to more renewable biofuels.
Dax Fu
2010-09-01
"Molecular Design of a Metal Transporter." Metal transporters are proteins residing in cell membranes that keep the amount of zinc and other metals in the body in check by selecting a nutritional metal ion against a similar and much moreabundant toxic one. How transporter proteins achieve this remarkable sensitivity is one of the questions addressed by Fu in this lecture.
ERIC Educational Resources Information Center
Seitz, W. A.; Matsen, F. A.
1974-01-01
Discusses the use of a central computer linked to a CRT console, with display projected onto a large screen, to operate computer augmentation of lectures in large group instruction. Indicates that both introductory tutorial and computer modes are feasible in subject matter presentation. (CC)
Pines, A.
1988-08-01
These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 32 refs., 56 figs.
Peter Vanier
2006-02-15
With new radiation detectors, finding smuggled nuclear materials in a huge container among thousands of others in a busy port becomes possible. To learn about these new detectors from a specialist who has spent several years developing these technologies, watch the 412th Brookhaven Lecture, "Advanced Neutron Detection Methods: New Tools for Countering Nuclear Terrorism."
Justice and Lecturer Professionalism.
ERIC Educational Resources Information Center
Macfarlane, Bruce
2001-01-01
Presents a conceptual framework for debating the ethics of pedagogy. The concepts of procedural, retributive, remedial, and distributive justice are presented as a means of incorporating many of the key ethical challenges that confront lecturers new to higher education. Recommends this justice framework as a means of encouraging practitioners to…
Organic Lecture Demonstrations.
ERIC Educational Resources Information Center
Silversmith, Ernest F.
1988-01-01
Provides a listing of 35 demonstrations designed to generate interest in organic chemistry and help put points across. Topics include opening lecture; molecular structure and properties; halogenation; nucleophilic substitution, alkenes and dienes, stereochemistry, spectroscopy, alcohols and phenols, aldehydes and ketones; carboxylic acids, amines,…
Pines, A.
1986-09-01
These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 55 figs.
NASA Technical Reports Server (NTRS)
Froidevaux, Lucien
1993-01-01
Three lectures will be given. The first one will draw from the general literature on microwave sounding from space. The next two will focus on a description of the Microwave Limb Sounder (MLS) and results obtained from its measurements relating to atmospheric chemistry and dynamics; this will draw from material recently published (or soon-to-be published) by the MLS team.
Participatory Lecture Demonstrations.
ERIC Educational Resources Information Center
Battino, Rubin
1979-01-01
The use of participatory lecture demonstrations in the classroom is described. Examples are given for the following topics: chromatography, chemical kinetics, balancing equations, the gas laws, kinetic molecular theory, Henry's law of gas solubility, electronic energy levels in atoms, and translational, vibrational, and rotational energies of…
ERIC Educational Resources Information Center
Webster, R. Scott
2015-01-01
In response to the lecture format coming under "attack" and being replaced by online materials and smaller tutorials, this paper attempts to offer not only a defence but also to assert that the potential value of the lecture is difficult to replicate through other learning formats. Some of the criticisms against lectures will be…
The curious case of null warped space
NASA Astrophysics Data System (ADS)
Anninos, Dionysios; Compère, Geoffrey; de Buyl, Sophie; Detournay, Stéphane; Guica, Monica
2010-11-01
We initiate a comprehensive study of a set of solutions of topologically massive gravity known as null warped anti-de Sitter spacetimes. These are pp-wave extensions of three-dimensional anti-de Sitter space. We first perform a careful analysis of the linearized stability of black holes in these spacetimes. We find two qualitatively different types of solutions to the linearized equations of motion: the first set has an exponential time dependence, the second — a polynomial time dependence. The solutions polynomial in time induce severe pathologies and moreover survive at the non-linear level. In order to make sense of these geometries, it is thus crucial to impose appropriate boundary conditions. We argue that there exists a consistent set of boundary conditions that allows us to reject the above pathological modes from the physical spectrum. The asymptotic symmetry group associated to these boundary conditions consists of a centrally-extended Virasoro algebra. Using this central charge we can account for the entropy of the black holes via Cardy's formula. Finally, we note that the black hole spectrum is chiral and prove a Birkoff theorem showing that there are no other stationary axisymmetric black holes with the specified asymptotics. We extend most of the analysis to a larger family of pp-wave black holes which are related to Schrödinger spacetimes with critical exponent z.
Diphoton resonance from a warped extra dimension
NASA Astrophysics Data System (ADS)
Bauer, Martin; Hörner, Clara; Neubert, Matthias
2016-07-01
We argue that extensions of the Standard Model (SM) with a warped extra dimension, which successfully address the hierarchy and flavor problems of elementary particle physics, can provide an elegant explanation of the 750 GeV diphoton excess recently reported by ATLAS and CMS. A gauge-singlet bulk scalar with {O} (1) couplings to fermions is identified as the new resonance S, and the vector-like Kaluza-Klein excitations of the SM quarks and leptons mediate its loop-induced couplings to photons and gluons. The electroweak gauge symmetry almost unambiguously dictates the bulk matter content and hence the hierarchies of the Sto γ γ, W W,ZZ,Zγ, toverline{t} and dijet decay rates. We find that the S → Zγ decay mode is strongly suppressed, such that Br( S → Zγ) /Br( S → γγ) < 0 .1. The hierarchy problem for the new scalar boson is solved in analogy with the Higgs boson by localizing it near the infrared brane. The infinite sums over the Kaluza-Klein towers of fermion states converge and can be calculated in closed form with a remarkably simple result. Reproducing the observed pp → S → γγ signal requires Kaluza-Klein masses in the multi-TeV range, consistent with bounds from flavor physics and electroweak precision observables.
Flavor structure of warped extra dimension models
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Perez, Gilad; Soni, Amarjit
2005-01-01
We recently showed that warped extra-dimensional models with bulk custodial symmetry and few TeV Kaluza-Klein (KK) masses lead to striking signals at B factories. In this paper, using a spurion analysis, we systematically study the flavor structure of models that belong to the above class. In particular we find that the profiles of the zero modes, which are similar in all these models, essentially control the underlying flavor structure. This implies that our results are robust and model independent in this class of models. We discuss in detail the origin of the signals in B physics. We also briefly study other new physics signatures that arise in rare K decays (K→πνν), in rare top decays [t→cγ(Z,gluon)], and the possibility of CP asymmetries in D0 decays to CP eigenstates such as KSπ0 and others. Finally we demonstrate that with light KK masses, ˜3 TeV, the above class of models with anarchic 5D Yukawas has a “CP problem” since contributions to the neutron electric dipole moment are roughly 20 times larger than the current experimental bound. Using AdS/CFT correspondence, these extra-dimensional models are dual to a purely 4D strongly coupled conformal Higgs sector thus enhancing their appeal.
CERN LHC signals from warped extra dimensions
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Belyaev, Alexander; Krupovnickas, Tadas; Perez, Gilad; Virzi, Joseph
2008-01-01
We study production of Kaluza-Klein (KK) gluons at the Large Hadron Collider (LHC) in the framework of a warped extra dimension with the standard model fields propagating in the bulk. We show that the detection of the KK gluon is challenging since its production is suppressed by small couplings to the proton’s constituents. Moreover, the KK gluon decays mostly to top pairs due to an enhanced coupling and hence is broad. Nevertheless, we demonstrate that for MKKG≲4TeV, 100fb-1 of data at the LHC can provide discovery of the KK gluon. We utilize a sizable left-right polarization asymmetry from the KK gluon resonance to maximize the signal significance, and we explore the novel feature of extremely highly energetic “top-jets.” We briefly discuss how the detection of electroweak gauge KK states (Z/W) faces a similar challenge since their leptonic decays (golden modes) are suppressed. Our analysis suggests that other frameworks, for example, little Higgs, which rely on UV completion via strong dynamics might face similar challenges, namely, (1) suppressed production rates for the new particles (such as Z'), due to their “light-fermion-phobic” nature, and (2) difficulties in detection since the new particles are broad and decay predominantly to third generation quarks and longitudinal gauge bosons.
Flavor Structure of Warped Extra Dimension Models
Agashe, Kaustubh; Perez, Gilad; Soni, Amarjit
2004-08-10
We recently showed, in hep-ph/0406101, that warped extra dimensional models with bulk custodial symmetry and few TeV KK masses lead to striking signals at B-factories. In this paper, using a spurion analysis, we systematically study the flavor structure of models that belong to the above class. In particular we find that the profiles of the zero modes, which are similar in all these models, essentially control the underlying flavor structure. This implies that our results are robust and model independent in this class of models. We discuss in detail the origin of the signals in B-physics. We also briefly study other NP signatures that arise in rare K decays (K {yields} {pi}{nu}{nu}), in rare top decays [t {yields} c{gamma}(Z, gluon)] and the possibility of CP asymmetries in D{sup 0} decays to CP eigenstates such as K{sub s}{pi}{sup 0} and others. Finally we demonstrate that with light KK masses, {approx} 3 TeV, the above class of models with anarchic 5D Yukawas has a ''CP problem'' since contributions to the neutron electric dipole moment are roughly 20 times larger than the current experimental bound. Using AdS/CFT correspondence, these extra-dimensional models are dual to a purely 4D strongly coupled conformal Higgs sector thus enhancing their appeal.
LHC Signals from Warped Extra Dimensions
Agashe, K.; Belyaev, A.; Krupovnickas, T.; Perez, G.; Virzi, J.
2006-12-06
We study production of Kaluza-Klein gluons (KKG) at the Large Hadron Collider (LHC) in the framework of a warped extra dimension with the Standard Model (SM) fields propagating in the bulk. We show that the detection of KK gluon is challenging since its production is suppressed by small couplings to the proton's constituents. Moreover, the KK gluon decaysmostly to top pairs due to an enhanced coupling and hence is broad. Nevertheless, we demonstrate that for MKKG<~;; 4 TeV, 100 fb-1 of data at the LHC can provide discovery of the KK gluon. We utilize a sizeable left-right polarization asymmetry from the KK gluon resonance to maximize the signal significance, and we explore the novel feature of extremely highly energetic"top-jets." We briefly discuss how the detection of electroweak gauge KK states (Z/W) faces a similar challenge since their leptonic decays ("golden" modes) are suppressed. Our analysis suggests that other frameworks, for example little Higgs, which rely on UV completion via strong dynamics might face similar challenges, namely (1) Suppressed production rates for the new particles (such as Z'), due to their"lightfermion-phobic" nature, and (2) Difficulties in detection since the new particles are broad and decay predominantly to third generation quarks and longitudinal gauge bosons.
Wofford, Marcia M; Spickard, Anderson W; Wofford, James L
2001-01-01
Advancing computer technology, cost-containment pressures, and desire to make innovative improvements in medical education argue for moving learning resources to the computer. A reasonable target for such a strategy is the traditional clinical lecture. The purpose of the lecture, the advantages and disadvantages of “live” versus computer-based lectures, and the technical options in computerizing the lecture deserve attention in developing a cost-effective, complementary learning strategy that preserves the teacher-learner relationship. Based on a literature review of the traditional clinical lecture, we build on the strengths of the lecture format and discuss strategies for converting the lecture to a computer-based learning presentation. PMID:11520384
Exploring Tablet PC Lectures: Lecturer Experiences and Student Perceptions in Biomedicine
ERIC Educational Resources Information Center
Choate, Julia; Kotsanas, George; Dawson, Phillip
2014-01-01
Lecturers using tablet PCs with specialised pens can utilise real-time changes in lecture delivery via digital inking. We investigated student perceptions and lecturer experiences of tablet PC lectures in large-enrolment biomedicine subjects. Lecturers used PowerPoint or Classroom Presenter software for lecture preparation and in-lecture pen-based…
Local and global dynamics of warped astrophysical discs
NASA Astrophysics Data System (ADS)
Ogilvie, Gordon I.; Latter, Henrik N.
2013-08-01
Astrophysical discs are warped whenever a misalignment is present in the system, or when a flat disc is made unstable by external forces. The evolution of the shape and mass distribution of a warped disc is driven not only by external influences but also by an internal torque, which transports angular momentum through the disc. This torque depends on internal flows driven by the oscillating pressure gradient associated with the warp, and on physical processes operating on smaller scales, which may include instability and turbulence. We introduce a local model for the detailed study of warped discs. Starting from the shearing sheet of Goldreich and Lynden-Bell, we impose the oscillating geometry of the orbital plane by means of a coordinate transformation. This warped shearing sheet (or box) is suitable for analytical and computational treatments of fluid dynamics, magnetohydrodynamics, etc., and it can be used to compute the internal torque that drives the large-scale evolution of the disc. The simplest hydrodynamic states in the local model are horizontally uniform laminar flows that oscillate at the orbital frequency. These correspond to the non-linear solutions for warped discs found in previous work by Ogilvie, and we present an alternative derivation and generalization of that theory. In a companion paper, we show that these laminar flows are often linearly unstable, especially if the disc is nearly Keplerian and of low viscosity. The local model can be used in future work to determine the non-linear outcome of the hydrodynamic instability of warped discs, and its interaction with others such as the magnetorotational instability.
NASA Astrophysics Data System (ADS)
Back, Bill
Leonard F. Konikow (U.S. Geological Survey), Hydrology Program Chairman for the 1986 AGU Spring Meeting, has been selected to be the 1985-1986 Birdsall Distinguished Lecturer for the Geological Society of America. Papers that will be presented on the distinguished tour include “Modeling Solute Transport and Dispersion in Groundwater,” “Groundwater Contamination and Aquifer Reclamation at the Rocky Mountain Arsenal, Colorado,” and “Predictive Accuracy of Groundwater Models: Lessons from Postaudits.” If you wish to have the Birdsall Distinguished Lecturer visit your institution either this or next year, please contact William Back, Chairman of the Hydrogeology Division, 431 National Center, U.S. Geological Survey, Reston, VA 22092.
None
2011-04-25
Troisième série de "Gregory lectures" en mémoire de B.Gregory (1919-1977),DG de 1965 à 1970. La première conférence B.Gregory a été donné par le Prof.V.Weisskopf, son prédécesseur. Chris Greeg (?)de Berkley prend aussi la parole
Rose, Nancy E
2002-10-01
SUMMARY This paper describes a lecture about my extended family, in which I discuss a variety of configurations consisting of lesbian, gay, and bisexual adults, and our children. It raises an array of issues, including alternative insemination, biological and nonbiological parentage, donors and birthmothers, adoption, co-parenting and blended families, significant others, and gay marriage and domestic partnership. It helps many students obtain both a more expansive sense of family and adeeper understanding of homophobia. PMID:24804601
Frame Shift/warp Compensation for the ARID Robot System
NASA Technical Reports Server (NTRS)
Latino, Carl D.
1991-01-01
The Automatic Radiator Inspection Device (ARID) is a system aimed at automating the tedious task of inspecting orbiter radiator panels. The ARID must have the ability to aim a camera accurately at the desired inspection points, which are in the order of 13,000. The ideal inspection points are known; however, the panel may be relocated due to inaccurate parking and warpage. A method of determining the mathematical description of a translated as well as a warped surface by accurate measurement of only a few points on this surface is developed here. The method uses a linear warp model whose effect is superimposed on the rigid body translation. Due to the angles involved, small angle approximations are possible, which greatly reduces the computational complexity. Given an accurate linear warp model, all the desired translation and warp parameters can be obtained by knowledge of the ideal locations of four fiducial points and the corresponding measurements of these points on the actual radiator surface. The method uses three of the fiducials to define a plane and the fourth to define the warp. Given this information, it is possible to determine a transformation that will enable the ARID system to translate any desired inspection point on the ideal surface to its corresponding value on the actual surface.
Warped document image correction method based on heterogeneous registration strategies
NASA Astrophysics Data System (ADS)
Tong, Lijing; Zhan, Guoliang; Peng, Quanyao; Li, Yang; Li, Yifan
2013-03-01
With the popularity of digital camera and the application requirement of digitalized document images, using digital cameras to digitalize document images has become an irresistible trend. However, the warping of the document surface impacts on the quality of the Optical Character Recognition (OCR) system seriously. To improve the warped document image's vision quality and the OCR rate, this paper proposed a warped document image correction method based on heterogeneous registration strategies. This method mosaics two warped images of the same document from different viewpoints. Firstly, two feature points are selected from one image. Then the two feature points are registered in the other image base on heterogeneous registration strategies. At last, image mosaics are done for the two images, and the best mosaiced image is selected by OCR recognition results. As a result, for the best mosaiced image, the distortions are mostly removed and the OCR results are improved markedly. Experimental results show that the proposed method can resolve the issue of warped document image correction more effectively.
Constraining the age of the NGC 4565 H I disk WARP: Determining the origin of gas WARPS
Radburn-Smith, David J.; Dalcanton, Julianne J.; Stilp, Adrienne M.; De Jong, Roelof S.; Streich, David; Bell, Eric F.; Monachesi, Antonela; Dolphin, Andrew E.; Holwerda, Benne W.; Bailin, Jeremy
2014-01-01
We have mapped the distribution of young and old stars in the gaseous H I warp of NGC 4565. We find a clear correlation of young stars (<600 Myr) with the warp but no coincident old stars (>1 Gyr), which places an upper limit on the age of the structure. The formation rate of the young stars, which increased ∼300 Myr ago relative to the surrounding regions, is (6.3{sub −1.5}{sup +2.5})×10{sup −5} M {sub ☉} yr{sup –1} kpc{sup –2}. This implies a ∼60 ± 20 Gyr depletion time of the H I warp, similar to the timescales calculated for the outer H I disks of nearby spiral galaxies. While some stars associated with the warp fall into the asymptotic giant branch (AGB) region of the color-magnitude diagram, where stars could be as old as 1 Gyr, further investigation suggests that they may be interlopers rather than real AGB stars. We discuss the implications of these age constraints for the formation of H I warps and the gas fueling of disk galaxies.
Warping of unsymmetric cross-ply graphite/epoxy laminates
NASA Technical Reports Server (NTRS)
Hahn, H. T.
1981-01-01
Warping in unsymmetric graphite/epoxy laminates was studied with particular attention given to the change of residual stresses resulting from long term environmental exposure. Square, cured prepreg sheets were measured for edge deflection with a cathetometer, then quartered and remeasured. Two postcuring durations were then used, 7.5 and one hr at 177 C; varying cooldown rates after curing were used for other samples, and one set was stored in vacuum at 75 C. Maximum deflections and weight changes were measured periodically at room temperature. Average curvatures, the effect of postcure, and the effect of long-term exposure were determined. Larger panels exhibited cylindrical warping and smaller panels underwent anticlastic warping. The deflections were related to weight changes, i.e. moisture absorption, and the lower the moisture content, the higher the deflection. Relaxation of residual stresses at 75 C was neglibible after 220 days.
Holographic entropy of Warped-AdS3 black holes
NASA Astrophysics Data System (ADS)
Donnay, Laura; Giribet, Gaston
2015-06-01
We study the asymptotic symmetries of three-dimensional Warped Anti-de Sitter (WAdS) spaces in three-dimensional New Massive Gravity (NMG). For a specific choice of asymptotic boundary conditions, we find that the algebra of charges is infinite dimensional and coincides with the semidirect sum of Virasoro algebra with non-vanishing central charge and an affine û(1) k Kač-Moody algebra. We show that the WAdS black hole configurations organize in terms of two commuting Virasoro algebras. We identify the Virasoro generators that expand the associated representations in the dual Warped Conformal Field Theory (WCFT) and, by applying the Warped version of the Cardy formula, we prove that the microscopic WCFT computation exactly reproduces the entropy of black holes in WAdS space.
Aspects of warped AdS3/CFT2 correspondence
NASA Astrophysics Data System (ADS)
Chen, Bin; Zhang, Jia-Ju; Zhang, Jian-Dong; Zhong, De-Liang
2013-04-01
In this paper we apply the thermodynamics method to investigate the holographic pictures for the BTZ black hole, the spacelike and the null warped black holes in three-dimensional topologically massive gravity (TMG) and new massive gravity (NMG). Even though there are higher derivative terms in these theories, the thermodynamics method is still effective. It gives consistent results with the ones obtained by using asymptotical symmetry group (ASG) analysis. In doing the ASG analysis we develop a brute-force realization of the Barnich-Brandt-Compere formalism with Mathematica code, which also allows us to calculate the masses and the angular momenta of the black holes. In particular, we propose the warped AdS3/CFT2 correspondence in the new massive gravity, which states that quantum gravity in the warped spacetime could holographically dual to a two-dimensional CFT with {c_R}={c_L}=24 /{Gm{β^2√{{2( {21-4{β^2}} )}}}}.
Two Virasoro symmetries in stringy warped AdS3
NASA Astrophysics Data System (ADS)
Compère, Geoffrey; Guica, Monica; Rodriguez, Maria J.
2014-12-01
We study three-dimensional consistent truncations of type IIB supergravity which admit warped AdS3 solutions. These theories contain subsectors that have no bulk dynamics. We show that the symplectic form for these theories, when restricted to the non-dynamical subsectors, equals the symplectic form for pure Einstein gravity in AdS3. Consequently, for each consistent choice of boundary conditions in AdS3, we can define a consistent phase space in warped AdS3 with identical conserved charges. This way, we easily obtain a Virasoro × Virasoro asymptotic symmetry algebra in warped AdS3; two different types of Virasoro × Kač-Moody symmetries are also consistent alternatives.
A twisted disk equation that describes warped galaxy disks
NASA Technical Reports Server (NTRS)
Barker, K.
1994-01-01
Warped H1 gas layers in the outer regions of spiral galaxies usually display a noticeably twisted structure. This structure is thought to arise primarily as a result of differential precession in the H1 disk as it settles toward a 'preferred orientation' in an underlying dark halo potential well that is not spherically symmetric. In an attempt to better understand the structure and evolution of these twisted, warped disk structures, we have utilized the 'twist-equation' formalism. Specifically, we have generalized the twist equation to allow the treatment of non-Keplerian disks and from it have derived the steady-state structure of twisted disks that develop from free precession in a nonspherical, logarithmic halo potential. This generalized equation can also be used to examine the time-evolutionary behavior of warped galaxy disks.
Torsion of Flanged Members with Cross Sections Restrained Against Warping
NASA Technical Reports Server (NTRS)
Hill, H N
1943-01-01
The longitudinal stresses and the stiffness of flange members - I-beams, channels, and Z-bars - were investigated when these members were subjected to torque with constraint against cross-sectional warping. Measured angles of rotation agreed with corresponding calculated values in which the torsion bending factor of the cross section was involved; the agreement was better for the I-beam and the Z-bar than for the channel. Longitudinal stresses measured at the mid-span were found to agree with the calculated values that involved unit warping as well as the torsion-bending factors: the channel showed the greatest discrepancy between measured and calculated values. When commonly given expressions for rotations and maximum longitudinal stresses in a twisted I-beam were applied to the channel and to the Z-bar, values were obtained that were in reasonably good agreement with values obtained by the method of torsion-bending constant and unit warping.
What causes the warp in the heliospheric current sheet
NASA Technical Reports Server (NTRS)
Wilcox, J. M.; Scherrer, P. H.
1981-01-01
A comparative discussion of the warp in the heliospheric current sheet is presented. Pioneer 10 and 11 data of the interplanetary magnetic field compared with earlier data (Helios 1 and 2) show a good agreement on the phenomenon of the warp; however, the interpretations differ. One theory (Thomas and Smith, 1980) proposes that fast solar wind streams associated with interaction regions may move the current sheet higher to heliospheric latitudes, thus causing the warp; while the earlier theory (1976) adequately explained the phenomenon by using the observed photospheric magnetic field and the Zeeman effect but omitted the solar wind dynamical considerations as part of the computations. It is shown that the Helios data of the polarity of the interplanetary magnetic field are in good agreement with the computed location of the current sheet, confirming the earlier theory.
Human low vision image warping - Channel matching considerations
NASA Technical Reports Server (NTRS)
Juday, Richard D.; Smith, Alan T.; Loshin, David S.
1992-01-01
We are investigating the possibility that a video image may productively be warped prior to presentation to a low vision patient. This could form part of a prosthesis for certain field defects. We have done preliminary quantitative studies on some notions that may be valid in calculating the image warpings. We hope the results will help make best use of time to be spent with human subjects, by guiding the selection of parameters and their range to be investigated. We liken a warping optimization to opening the largest number of spatial channels between the pixels of an input imager and resolution cells in the visual system. Some important effects are not quantified that will require human evaluation, such as local 'squashing' of the image, taken as the ratio of eigenvalues of the Jacobian of the transformation. The results indicate that the method shows quantitative promise. These results have identified some geometric transformations to evaluate further with human subjects.
Some Examples Of Image Warping For Low Vision Prosthesis
NASA Astrophysics Data System (ADS)
Juday, Richard D.; Loshin, David S.
1988-08-01
NASA and Texas Instruments have developed an image processor, the Programmable Remapper 1, for certain functions in machine vision. The Remapper performs a highly arbitrary geometric warping of an image at video rate. It might ultimately be shrunk to a size and cost that could allow its use in a low-vision prosthesis. We have developed coordinate warpings for retinitis pigmentosa (tunnel vision) and for maculapathy (loss of central field) that are intended to make best use of the patient's remaining viable retina. The rationales and mathematics are presented for some warpings that we will try in clinical studies using the Remapper's prototype. (Recorded video imagery was shown at the conference for the maculapathy remapping.
A look at dynamic time warping in seismology
NASA Astrophysics Data System (ADS)
Mikesell, T. D.; Malcolm, A. E.; Mordret, A.; Bozdag, E.
2015-12-01
Dynamic time warping (DTW) is a method used to compare two time series. The idea is to search for a warping function that minimizes the misfit between the two time series. In seismology we can use DTW to measure arrival time differences in seismic traces or spatial differences in seismic images. Here we give an overview of the method and applications in seismology. We focus on a coda wave interferometry example and a waveform inversion example. We will cover the advantages of dynamic time warping; for example, DTW has been shown to outperform windowed-cross correlation when the signal-to-noise ratio is low. Finally, we will highlight new directions in which this method may find more application in seismology.
Design of a reading test for low vision image warping
NASA Technical Reports Server (NTRS)
Loshin, David S.; Wensveen, Janice; Juday, Richard D.; Barton, R. S.
1993-01-01
NASA and the University of Houston College of Optometry are examining the efficacy of image warping as a possible prosthesis for at least two forms of low vision - maculopathy and retinitis pigmentosa. Before incurring the expense of reducing the concept to practice, one would wish to have confidence that a worthwhile improvement in visual function would result. NASA's Programmable Remapper (PR) can warp an input image onto arbitrary geometric coordinate systems at full video rate, and it has recently been upgraded to accept computer-generated video text. We have integrated the Remapper with an SRI eye tracker to simulate visual malfunction in normal observers. A reading performance test has been developed to determine if the proposed warpings yield an increase in visual function; i.e., reading speed. We will describe the preliminary experimental results of this reading test with a simulated central field defect with and without remapped images.
VME rollback hardware for time warp multiprocessor systems
NASA Technical Reports Server (NTRS)
Robb, Michael J.; Buzzell, Calvin A.
1992-01-01
The purpose of the research effort is to develop and demonstrate innovative hardware to implement specific rollback and timing functions required for efficient queue management and precision timekeeping in multiprocessor discrete event simulations. The previously completed phase 1 effort demonstrated the technical feasibility of building hardware modules which eliminate the state saving overhead of the Time Warp paradigm used in distributed simulations on multiprocessor systems. The current phase 2 effort will build multiple pre-production rollback hardware modules integrated with a network of Sun workstations, and the integrated system will be tested by executing a Time Warp simulation. The rollback hardware will be designed to interface with the greatest number of multiprocessor systems possible. The authors believe that the rollback hardware will provide for significant speedup of large scale discrete event simulation problems and allow multiprocessors using Time Warp to dramatically increase performance.
Validation of a dose warping algorithm using clinically realistic scenarios
Dehghani, H; Green, S; Webster, G J
2015-01-01
Objective: Dose warping following deformable image registration (DIR) has been proposed for interfractional dose accumulation. Robust evaluation workflows are vital to clinically implement such procedures. This study demonstrates such a workflow and quantifies the accuracy of a commercial DIR algorithm for this purpose under clinically realistic scenarios. Methods: 12 head and neck (H&N) patient data sets were used for this retrospective study. For each case, four clinically relevant anatomical changes have been manually generated. Dose distributions were then calculated on each artificially deformed image and warped back to the original anatomy following DIR by a commercial algorithm. Spatial registration was evaluated by quantitative comparison of the original and warped structure sets, using conformity index and mean distance to conformity (MDC) metrics. Dosimetric evaluation was performed by quantitative comparison of the dose–volume histograms generated for the calculated and warped dose distributions, which should be identical for the ideal “perfect” registration of mass-conserving deformations. Results: Spatial registration of the artificially deformed image back to the planning CT was accurate (MDC range of 1–2 voxels or 1.2–2.4 mm). Dosimetric discrepancies introduced by the DIR were low (0.02 ± 0.03 Gy per fraction in clinically relevant dose metrics) with no statistically significant difference found (Wilcoxon test, 0.6 ≥ p ≥ 0.2). Conclusion: The reliability of CT-to-CT DIR-based dose warping and image registration was demonstrated for a commercial algorithm with H&N patient data. Advances in knowledge: This study demonstrates a workflow for validation of dose warping following DIR that could assist physicists and physicians in quantifying the uncertainties associated with dose accumulation in clinical scenarios. PMID:25791569
The origin of the warped heliospheric current sheet
NASA Astrophysics Data System (ADS)
Wilcox, J. M.; Scherrer, P. H.; Hoeksema, J. T.
1980-03-01
The warped heliospheric current sheet in early 1976 was calculated from the observed photospheric magnetic field using a potential field method. Comparisons with measurements of the interplanetary magnetic field polarity in early 1976 obtained at several locations in the heliosphere at Helios 1, Helios 2, Pioneer 11 and Earth show a rather detailed agreement between the computed current sheet and the observations. It appears that the large scale structure of the warped heliospheric current sheet is determined by the structure of the photospheric magnetic field, and that "ballerina skirt" effects may add small scale ripples.
A `warp drive' with more reasonable total energy requirements
NASA Astrophysics Data System (ADS)
Van Den Broeck, Chris
1999-12-01
I show how a minor modification of the Alcubierre geometry can dramatically improve the total energy requirements for a `warp bubble' that can be used to transport macroscopic objects. A spacetime is presented for which the total negative mass needed is of the order of a few solar masses, accompanied by a comparable amount of positive energy. This puts the warp drive in the mass scale of large traversable wormholes. The new geometry satisfies the quantum inequality concerning WEC violations and has the same advantages as the original Alcubierre spacetime.
The origin of the warped heliospheric current sheet
NASA Technical Reports Server (NTRS)
Wilcox, J. M.; Scherrer, P. H.; Hoeksema, J. T.
1980-01-01
The warped heliospheric current sheet in early 1976 was calculated from the observed photospheric magnetic field using a potential field method. Comparisons with measurements of the interplanetary magnetic field polarity in early 1976 obtained at several locations in the heliosphere at Helios 1, Helios 2, Pioneer 11 and Earth show a rather detailed agreement between the computed current sheet and the observations. It appears that the large scale structure of the warped heliospheric current sheet is determined by the structure of the photospheric magnetic field, and that "ballerina skirt" effects may add small scale ripples.
The dynamical settling of warped disks and angular momentum transport in galaxies
NASA Technical Reports Server (NTRS)
Fisher, P.
1994-01-01
We present results of three-dimensional, hydrodynamic models of gaseous disks settling in a nonspherical potential. As the gas settles, differential precession creates a warped disk similar to the warps seen in spiral galaxies. A logarithmic potential, indicative of a massive halo, seems to induce warps more extreme than those produced by a l/r potential with a quadrupole distortion.
NASA Astrophysics Data System (ADS)
The Association for Women Geoscientists Foundation has received a $9000 grant from Phillips Petroleum Company to fund the Phillips-AWG Distinguished Lectures. The money will pay travel expenses for the women geoscientists listed with the AWG Speakers Bureau.More than 100 women geoscientists are available through the AWG Speakers Bureau. Their topics cover all the Earth sciences including geology, geophysics, geochemistry, paleobotany, planetary geology and mineral exploration. Their areas of study range from the U.S., Europe and South America to Mars. They come from academia, government and industry in 33 states and the District of Columbia.
NASA Astrophysics Data System (ADS)
Loebbert, Florian
2016-08-01
In these introductory lectures we discuss the topic of Yangian symmetry from various perspectives. Forming the classical counterpart of the Yangian and an extension of ordinary Noether symmetries, first the concept of nonlocal charges in classical, two-dimensional field theory is reviewed. We then define the Yangian algebra following Drinfel’d's original motivation to construct solutions to the quantum Yang–Baxter equation. Different realizations of the Yangian and its mathematical role as a Hopf algebra and quantum group are discussed. We demonstrate how the Yangian algebra is implemented in quantum, two-dimensional field theories and how its generators are renormalized. Implications of Yangian symmetry on the two-dimensional scattering matrix are investigated. We furthermore consider the important case of discrete Yangian symmetry realized on integrable spin chains. Finally we give a brief introduction to Yangian symmetry in planar, four-dimensional super Yang–Mills theory and indicate its impact on the dilatation operator and tree-level scattering amplitudes. These lectures are illustrated by several examples, in particular the two-dimensional chiral Gross–Neveu model, the Heisenberg spin chain and { N }=4 superconformal Yang–Mills theory in four dimensions.
Technology Lecturer Turned Technology Teacher
ERIC Educational Resources Information Center
Lee, Kerry
2009-01-01
This case study outlines a program developed by a group of 6 teachers' college lecturers who volunteered to provide a technology program to year 7 & 8 children (11- and 12-year-olds) for a year. This involved teaching technology once a week. As technology education was a new curriculum area when first introduced to the college, few lecturers had…
Surviving Lecture: A Pedagogical Alternative
ERIC Educational Resources Information Center
Berry, Whitney
2008-01-01
Lecture is the approach traditionally used to teach music theory courses. Although efficient in the delivery of large amounts of information in a short period of time, lecture lacks the effectiveness of an active learning approach. "Theory Survivor" is a unique cooperative-learning method based on the Student Teams-Achievement Divisions technique…
Co-ordinated Classroom Lectures.
ERIC Educational Resources Information Center
Harmon, Darell Boyd
From a series of lectures, a selection of eight are oriented principally toward the biologically developing child, and the physiological operations in visual process. The numbered lectures are--(1) The Coordinated Classroom, its Philosophy and Principles, (2) An Outline of a Biological Point of View, (3) The Evolution of Structure--despite man's…
The warped product approach to magnetically charged GMGHS spacetime
NASA Astrophysics Data System (ADS)
Choi, Jaedong
2014-11-01
In the framework of Lorentzian multiply warped products we study the magnetically charged Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) interior spacetime in the string frame. We also investigate geodesic motion in various hypersurfaces, and compare their solutions of geodesic equations with the ones obtained in the Einstein frame.
Self-dual warped AdS3 black holes
NASA Astrophysics Data System (ADS)
Chen, Bin; Ning, Bo
2010-12-01
We study a new class of solutions of three-dimensional topological massive gravity. These solutions can be taken as nonextremal black holes, with their extremal counterparts being discrete quotients of spacelike warped AdS3 along the U(1)L isometry. We study the thermodynamics of these black holes and show that the first law is satisfied. We also show that for consistent boundary conditions, the asymptotic symmetry generators form only one copy of the Virasoro algebra with central charge cL=(4νℓ)/(G(ν2+3)), with which the Cardy formula reproduces the black hole entropy. We compute the real-time correlators of scalar perturbations and find a perfect match with the dual conformal field theory (CFT) predictions. Our study provides a novel example of warped AdS/CFT correspondence: the self-dual warped AdS3 black hole is dual to a CFT with nonvanishing left central charge. Moreover, our investigation suggests that the quantum topological massive gravity asymptotic to the same spacelike warped AdS3 in different consistent ways may be dual to different two-dimensional CFTs.
Wing Warping and Its Impact on Aerodynamic Efficiency
NASA Astrophysics Data System (ADS)
Loh, Ben; Jacob, Jamey
2007-11-01
Inflatable wings have been demonstrated in many applications such as UAVs, airships, and missile stabilization surfaces. A major concern presented by the use of an inflatable wing has been the lack of traditional roll control surfaces. This leaves the designer with several options in order to have control about the roll axis. Since inflatable wings have a semi-flexible structure, wing warping is the obvious solution to this problem. The current method is to attach servos and control linkages to external surface of the wing that results in variation of profile chamber and angle of attack from leading edge or trailing edge deflection. Designs using internal muscles will also be discussed. This creates a lift differential between the half-spans, resulting in a roll moment. The trailing edge on the other half-span can also be deflected in the opposite direction to increase the roll moment as well as to reduce roll-yaw coupling. Comparisons show that higher L/D ratios are possible than using traditional control surfaces. An additional benefit is the ability to perform symmetric warping to achieve optimum aerodynamic performance. Via warping alone, an arbitrary span can be warped such that it has the same aerodynamic characteristics as an elliptical planform. Comparisons between lifting line theory and test results will be presented.
10. View of Draper darby chain loom from warp beam ...
10. View of Draper darby chain loom from warp beam end, patent date 1913, made by Drpaer Corporation, Hopedale, Massachusetts. Acquired ca. 1941. Note Draper-Northrop name on automatic spindle changer. - Riverdale Cotton Mill, Corner of Middle & Lower Streets, Valley, Chambers County, AL
NASA Technical Reports Server (NTRS)
Dennis, Brian R.
2006-01-01
This lecture will cover solar thermal radiation, particularly as it relates to the high energy solar processes that are the subject of this summer school. After a general review of thermal radiation from the Sun and a discussion of basic definitions, the various emission and absorption mechanisms will be described including black-body emission, bremsstrahlung, free-bound, and atomic line emissions of all kinds. The bulk of the time will be spent discussing the observational characteristics of thermal flare plasma and what can be learned about the flare energy release process from observations of the thermal radiation at all wavelengths. Information that has been learned about the morphology, temperature distribution, and composition of the flare plasma will be presented. The energetics of the thermal flare plasma will be discussed in relation to the nonthermal energy of the particles accelerated during the flare. This includes the total energy, the radiated and conductive cooling processes, and the total irradiated energy.
NASA Astrophysics Data System (ADS)
Beristain, Sergio
2002-11-01
Some thirty years ago acoustics lecturing started in Mexico at the National Polytechnic Institute in Mexico City, as part of the Bachelor of Science degree in Communications and Electronics Engineering curricula, including the widest program on this field in the whole country. This program has been producing acoustics specialists ever since. Nowadays many universities and superior education institutions around the country are teaching students at the B.Sc. level and postgraduate level many topics related to acoustics, such as Architectural Acoustics, Seismology, Mechanical Vibrations, Noise Control, Audio, Audiology, Music, etc. Also many institutions have started research programs in related fields, with participation of medical doctors, psychologists, musicians, engineers, etc. Details will be given on particular topics and development.
Lecturing with a Virtual Whiteboard
NASA Astrophysics Data System (ADS)
Milanovic, Zoran
2006-09-01
Recent advances in computer technology, word processing software, and projection systems have made traditional whiteboard lecturing obsolete. Tablet personal computers connected to display projectors and running handwriting software have replaced the marker-on-whiteboard method of delivering a lecture. Since the notes can be saved into an electronic file, they can be uploaded to a class website to be perused by the students later. This paper will describe the author's experiences in using this new technology to deliver physics lectures at an engineering school. The benefits and problems discovered will be reviewed and results from a survey of student opinions will be discussed.
Introductory Lectures on Collider Physics
NASA Astrophysics Data System (ADS)
Tait, Tim M. P.; Wang, Lian-Tao
2013-12-01
These are elementary lectures about collider physics. They are aimed at graduate students who have some background in computing Feynman diagrams and the Standard Model, but assume no particular sophistication with the physics of high energy colliders.
AMUM LECTURE: Therapeutic ultrasound
NASA Astrophysics Data System (ADS)
Crum, Lawrence A.
2004-01-01
The use of ultrasound in medicine is now quite commonplace, especially with the recent introduction of small, portable and relatively inexpensive, hand-held diagnostic imaging devices. Moreover, ultrasound has expanded beyond the imaging realm, with methods and applications extending to novel therapeutic and surgical uses. These applications broadly include: tissue ablation, acoustocautery, lipoplasty, site-specific and ultrasound mediated drug activity, extracorporeal lithotripsy, and the enhancement of natural physiological functions such as wound healing and tissue regeneration. A particularly attractive aspect of this technology is that diagnostic and therapeutic systems can be combined to produce totally non-invasive, imageguided therapy. This general lecture will review a number of these exciting new applications of ultrasound and address some of the basic scientific questions and future challenges in developing these methods and technologies for general use in our society. We shall particularly emphasize the use of High Intensity Focused Ultrasound (HIFU) in the treatment of benign and malignant tumors as well as the introduction of acoustic hemostasis, especially in organs which are difficult to treat using conventional medical and surgical techniques.
Introductory lecture: nanoplasmonics.
Brongersma, Mark L
2015-01-01
Nanoplasmonics or nanoscale metal-based optics is a field of science and technology with a tremendously rich and colourful history. Starting with the early works of Michael Faraday on gold nanocolloids and optically-thin gold leaf, researchers have been fascinated by the unusual optical properties displayed by metallic nanostructures. We now can enjoy selecting from over 10 000 publications every year on the topic of plasmonics and the number of publications has been doubling about every three years since 1990. This impressive productivity can be attributed to the significant growth of the scientific community as plasmonics has spread into a myriad of new directions. With 2015 being the International Year of Light, it seems like a perfect moment to review some of the most notable accomplishments in plasmonics to date and to project where the field may be moving next. After discussing some of the major historical developments in the field, this article will analyse how the most successful plasmonics applications are capitalizing on five key strengths of metallic nanostructures. This Introductory Lecture will conclude with a brief look into the future. PMID:25968246
Chromatographic peak alignment using derivative dynamic time warping.
Bork, Christopher; Ng, Kenneth; Liu, Yinhan; Yee, Alex; Pohlscheidt, Michael
2013-01-01
Chromatogram overlays are frequently used to monitor inter-batch performance of bioprocess purification steps. However, the objective analysis of chromatograms is difficult due to peak shifts caused by variable phase durations or unexpected process holds. Furthermore, synchronization of batch process data may also be required prior to performing multivariate analysis techniques. Dynamic time warping was originally developed as a method for spoken word recognition, but shows potential in the objective analysis of time variant signals, such as manufacturing data. In this work we will discuss the application of dynamic time warping with a derivative weighting function to align chromatograms to facilitate process monitoring and fault detection. In addition, we will demonstrate the utility of this method as a preprocessing step for multivariate model development. PMID:23292764
Warped black holes in 3D general massive gravity
NASA Astrophysics Data System (ADS)
Tonni, Erik
2010-08-01
We study regular spacelike warped black holes in the three dimensional general massive gravity model, which contains both the gravitational Chern-Simons term and the linear combination of curvature squared terms characterizing the new massive gravity besides the Einstein-Hilbert term. The parameters of the metric are found by solving a quartic equation, constrained by an inequality that imposes the absence of closed timelike curves. Explicit expressions for the central charges are suggested by exploiting the fact that these black holes are discrete quotients of spacelike warped AdS 3 and a known formula for the entropy. Previous results obtained separately in topological massive gravity and in new massive gravity are recovered as special cases.
A method and apparatus for sizing and separating warp yarns
Sheen, Shuh-Haw; Chien, Hual-Te; Raptis, Apostolos C.; Kupperman, David S.
1997-12-01
A slashing process for preparing warp yarns for weaving operations includes the steps of sizing and/or desizing the yarns in an acoustic resonance box and separating the yarns with a leasing apparatus comprised of a set of acoustically agitated lease rods. The sizing step includes immersing the yarns in a size solution contained in an acoustic resonance box. Acoustic transducers are positioned against the exterior of the box for generating an acoustic pressure field within the size solution. Ultrasonic waves that result from the acoustic pressure field continuously agitate the size solution to effect greater mixing and more uniform application and penetration of the size onto the yarns. The sized yarns are then separated by passing the warp yarns over and under lease rods. Electroacoustic transducers generate acoustic waves along the longitudinal axis of the lease rods, creating a shearing motion on the surface of the rods for splitting the yarns.
Dynamic time warp pattern matching using an integrated multiprocessing array
Weste, N.; Burr, D.J.; Ackland, B.D.
1983-08-01
Dynamic time warping is a well-established technique for time alignment and comparison of speech and image patterns. This paper describes the architecture, algorithms and design of a CMOS integrated processing array used for computing the dynamic time warp algorithm. Emphasis is placed on speech recognition applications because of the real-time constraints imposed by isolated and continuous speech recognition. High throughput is obtained through the use of extensive pipelining, parallel computation and simultaneous matching of multiple patterns. A realistic speech recognition application based on 40 nine-component linear predictor coefficient (LPC) vectors per word permits 20000 isolated word comparisons per second or, equivalently, real time recognition of a 20000 word vocabulary. The paper also illustrates a trend in IC design in which the architecture of the system leads to an embodiment which far outperforms solutions based on current design methodologies. 27 references.
Conformal Gravity and the Alcubierre Warp Drive Metric
NASA Astrophysics Data System (ADS)
Varieschi, Gabriele; Burstein, Zily
2013-04-01
We present an analysis of the classic Alcubierre metric based on conformal gravity, rather than standard general relativity. The main characteristics of the resulting warp drive remain the same as in the original study by Alcubierre, namely that effective super-luminal motion is a viable outcome of the metric. We show that for particular choices of the shaping function, the Alcubierre metric in the context of conformal gravity does not violate the weak energy condition, as was the case of the original solution. In particular, the resulting warp drive does not require the use of exotic matter. Therefore, if conformal gravity is a correct extension of general relativity, super-luminal motion via an Alcubierre metric might be a realistic solution, thus allowing faster-than-light interstellar travel.
Development of Warp Yarn Tension During Shedding: A Theoretical Approach
NASA Astrophysics Data System (ADS)
Ghosh, Subrata; Chary, Prabhakara; Roy, Sukumar
2015-10-01
Theoretical investigation on the process of development of warp yarn tension during weaving for tappet shedding is carried out, based on the dynamic nature of shed geometry. The path of warp yarn on a weaving machine is divided into four different zones. The tension developed in each zone is estimated for every minute rotation of the bottom shaft. A model has been developed based on the dynamic nature of shed geometry and the possible yarn flow from one zone to another. A computer program, based on the model of shedding process, is developed for predicting the warp yarn tension variation during shedding. The output of the model and the experimental values of yarn tension developed in zone-D i.e. between the back rest and the back lease rod are compared, which shows a good agreement between them. The warp yarn tension values predicted by the model in zone-D are 10-13 % lesser than the experimentally measured values. By analyzing the theoretical data of the peak value of developed yarn tension at four zones i.e. zone-A, zone-B, zone-C and zone-D, it is observed that the peak yarn tension value of A, B, C-zones are much higher than the peak tension near the back rest i.e. at zone-D. It is about twice or more than the yarn tension near the back rest. The study also reveals that the developed yarn tension peak values are different for the extreme positions of a heald. The impact of coefficient of friction on peak value of yarn tension is nominal.
Alcubierre warp drive: On the matter of matter
NASA Astrophysics Data System (ADS)
McMonigal, Brendan; Lewis, Geraint F.; O'Byrne, Philip
2012-03-01
The Alcubierre warp drive allows a spaceship to travel at an arbitrarily large global velocity by deforming the spacetime in a bubble around the spaceship. Little is known about the interactions between massive particles and the Alcubierre warp drive, or the effects of an accelerating or decelerating warp bubble. We examine geodesics representative of the paths of null and massive particles with a range of initial velocities from -c to c interacting with an Alcubierre warp bubble traveling at a range of globally subluminal and superluminal velocities on both constant and variable velocity paths. The key results for null particles match what would be expected of massive test particles as they approach ±c. The increase in energy for massive and null particles is calculated in terms of vs, the global ship velocity, and vp, the initial velocity of the particle with respect to the rest frame of the origin/destination of the ship. Particles with positive vp obtain extremely high energy and velocity and become “time locked” for the duration of their time in the bubble, experiencing very little proper time between entering and eventually leaving the bubble. When interacting with an accelerating bubble, any particles within the bubble at the time receive a velocity boost that increases or decreases the magnitude of their velocity if the particle is moving toward the front or rear of the bubble, respectively. If the bubble is decelerating, the opposite effect is observed. Thus Eulerian matter is unaffected by bubble accelerations/decelerations. The magnitude of the velocity boosts scales with the magnitude of the bubble acceleration/deceleration.
Of warps and woofs: the tapestry of medical education.
Friedman, C P
1993-06-01
The author likens some major aspects of academic medical centers to tightly and carefully woven tapestries. The metaphor is intended to highlight the complexity of medical centers and to help those who are working to promote meaningful and sustainable innovations in medical education. Underlying the presentation is the premise that there already exist several "good ideas" to improve medical education, and that deeper understanding of the barriers to change can promote adoption of these ideas and others. Three tapestries are presented. Each has a vertical "warp" representing one dimension of an academic medical center, and each has a horizontal "woof" representing an interrelated dimension. (In one tapestry, for example, departmental resources constitute the warp and the faculty functions of teaching, research, and service constitute the woof.) In each tapestry, the warp is presently the dominant feature. In each, strengthening or empowering the woof is seen as a step that would facilitate change. Because educational change is a difficult and inevitably slow process, those who work for change are counseled to be patient and have realistic expectations. PMID:8507322
Effective fermion couplings in warped 5D Higgsless theories
NASA Astrophysics Data System (ADS)
Bechi, J.; Casalbuoni, R.; de Curtis, S.; Dominici, D.
2006-11-01
We consider a 5-dimensional SU(2) gauge theory with fermions in the bulk and with additional SU(2) and U(1) kinetic terms on the branes. The electroweak breaking is obtained by boundary conditions. After deconstruction, fermions in the bulk are eliminated by using their equations of motion. In this way, standard model fermion mass terms and direct couplings to the internal gauge bosons of the moose are generated. The presence of these new couplings gives a new contribution to the γ3 parameter in addition to the gauge boson term. This allows the possibility of a cancellation between the two contributions, which can be local (site by site) or global. Going back to the continuum, we show that the implementation of local cancellation in any generic warped metric leaves massless fermions. This is due to the presence of one horizon on the infrared brane. However, we can require a global cancellation of the new physics contributions to the γ3 parameter. This fixes relations among the warp factor and the parameters of the fermion and gauge sectors. It turns out that the warping of the metric does not substantially modify the results obtained in the flat case.
Effective fermion couplings in warped 5D Higgsless theories
Bechi, J.; Casalbuoni, R.; De Curtis, S.; Dominici, D.
2006-11-01
We consider a 5-dimensional SU(2) gauge theory with fermions in the bulk and with additional SU(2) and U(1) kinetic terms on the branes. The electroweak breaking is obtained by boundary conditions. After deconstruction, fermions in the bulk are eliminated by using their equations of motion. In this way, standard model fermion mass terms and direct couplings to the internal gauge bosons of the moose are generated. The presence of these new couplings gives a new contribution to the {epsilon}{sub 3} parameter in addition to the gauge boson term. This allows the possibility of a cancellation between the two contributions, which can be local (site by site) or global. Going back to the continuum, we show that the implementation of local cancellation in any generic warped metric leaves massless fermions. This is due to the presence of one horizon on the infrared brane. However, we can require a global cancellation of the new physics contributions to the {epsilon}{sub 3} parameter. This fixes relations among the warp factor and the parameters of the fermion and gauge sectors. It turns out that the warping of the metric does not substantially modify the results obtained in the flat case.
A new beam theory using first-order warping functions
NASA Technical Reports Server (NTRS)
Ie, C. A.; Kosmatka, J. B.
1990-01-01
Due to a certain type of loading and geometrical boundary conditions, each beam will respond differently depending on its geometrical form of the cross section and its material definition. As an example, consider an isotropic rectangular beam under pure bending. Plane sections perpendicular to the longitudinal axis of the beam will remain plane and perpendicular to the deformed axis after deformation. However, due to the Poisson effect, particles in the planes will move relative to each other resulting in a form of anticlastic deformation. In other words, even in pure bending of an isotropic beam, each cross section will deform in the plane. If the material of the beam above is replaced by a generally anisotropic material, then the cross sections will not only deform in the plane, but also out of plane. Hence, in general, both in-plane deformation and out-of-plane warping will exist and depend on the geometrical form and material definition of the cross sections and also on the loadings. For the purpose of explanation, an analogy is made. The geometrical forms of the bodies of each individual are unique. Hence, different sizes of clothes are needed. Finding the sizes of clothes for individuals is like determining the warping functions in beams. A new beam theory using first-order warping functions is introduced. Numerical examples will be presented for an isotropic beam with rectangular cross section. The theory can be extended for composite beams.
Fermion masses and mixing in general warped extra dimensional models
NASA Astrophysics Data System (ADS)
Frank, Mariana; Hamzaoui, Cherif; Pourtolami, Nima; Toharia, Manuel
2015-06-01
We analyze fermion masses and mixing in a general warped extra dimensional model, where all the Standard Model (SM) fields, including the Higgs, are allowed to propagate in the bulk. In this context, a slightly broken flavor symmetry imposed universally on all fermion fields, without distinction, can generate the full flavor structure of the SM, including quarks, charged leptons and neutrinos. For quarks and charged leptons, the exponential sensitivity of their wave functions to small flavor breaking effects yield hierarchical masses and mixing as it is usual in warped models with fermions in the bulk. In the neutrino sector, the exponential wave-function factors can be flavor blind and thus insensitive to the small flavor symmetry breaking effects, directly linking their masses and mixing angles to the flavor symmetric structure of the five-dimensional neutrino Yukawa couplings. The Higgs must be localized in the bulk and the model is more successful in generalized warped scenarios where the metric background solution is different than five-dimensional anti-de Sitter (AdS5 ). We study these features in two simple frameworks, flavor complimentarity and flavor democracy, which provide specific predictions and correlations between quarks and leptons, testable as more precise data in the neutrino sector becomes available.
Bubble Pulse Cancelation in the Time-Frequency Domain Using Warping Operators
NASA Astrophysics Data System (ADS)
Niu, Hai-Qiang; Zhang, Ren-He; Li, Zheng-Lin; Guo, Yong-Gang; He, Li
2013-08-01
The received shock waves produced by explosive charges are often polluted by bubble pulses in underwater acoustic experiments. A method based on warping operators is proposed to cancel the bubble pulses in the time-frequency domain. This is applied to the explosive data collected during the Yellow Sea experiment in November 2000. The original received signal is first transformed into a warped signal by warping operators. Then, the warped signal is analyzed in the time-frequency domain. Due to the different features between the shock waves and the bubble pulses in the time-frequency domain for the warped signal, the bubble pulses can be easily filtered out. Furthermore, the shock waves in the original time domain can be retrieved by the inverse warping transformation. The autocorrelation functions and the time-frequency representation show that the bubble pulses can be canceled effectively.
Evaluation of the Intel iWarp parallel processor for space flight applications
NASA Technical Reports Server (NTRS)
Hine, Butler P., III; Fong, Terrence W.
1993-01-01
The potential of a DARPA-sponsored advanced processor, the Intel iWarp, for use in future SSF Data Management Systems (DMS) upgrades is evaluated through integration into the Ames DMS testbed and applications testing. The iWarp is a distributed, parallel computing system well suited for high performance computing applications such as matrix operations and image processing. The system architecture is modular, supports systolic and message-based computation, and is capable of providing massive computational power in a low-cost, low-power package. As a consequence, the iWarp offers significant potential for advanced space-based computing. This research seeks to determine the iWarp's suitability as a processing device for space missions. In particular, the project focuses on evaluating the ease of integrating the iWarp into the SSF DMS baseline architecture and the iWarp's ability to support computationally stressing applications representative of SSF tasks.
Morgentaler, H
1989-01-01
In this lecture, Dr. Henry Morgentaler describes how he led the fight to make abortion sage and legal in Canada. In 1967, the Canadian government began exploring possible changes in the abortion law, which at that made abortion a major crime. As president of the Humanist Fellowship of Montreal, Morgentaler presented a brief to House of Commons calling for abortion on request. His appeal attracted great media attention, and soon women started coming to Morgentaler's office seeking abortions. Risking prosecution, Morgentaler agreed to perform the operations (in the process becoming the first doctor in North America to use the vacuum suction technique). His abortion practice grew rapidly. In 1969, the Canadian government made abortion legal if approved by a committee of 3 doctors and if performed in a hospital. Though an improvement over the previous law, the new abortion law still had many deficiencies, most notably: it discriminated against women in rural areas (where the only available hospitals were Catholic), and it made getting an abortion a lengthy process, making the procedure more dangerous. Still campaigning vigorously performing abortions in his Montreal clinic, Morgentaler on charges of illegal abortion by the Quebec government. For the next 6 years, Morgentaler rode a legal roller coaster -- 3 jury acquittals were overturned or disregarded -- serving 10 months in prison throughout the ordeal (the legal battle produced the so-called Morgentaler Amendment, which stipulates that court cannot substitute its own verdict for a jury verdict of not guilty). In 1976, Quebec ended its battle with Morgentaler, who in turn launched his campaign to the rest of Canada. And in 1988, the Canadian Supreme Court rescinded the abortion low, thus affirming the dignity and equality of women. PMID:12284999
Detailed study of null and timelike geodesics in the Alcubierre warp spacetime
NASA Astrophysics Data System (ADS)
Müller, Thomas; Weiskopf, Daniel
2012-02-01
The geodesic equation of the Alcubierre warp spacetime is converted into its non-affinely parametrized form for a detailed discussion of the motion of particles and the visual effects as observed by a traveller inside the warp bubble or a person looking from outside. To include gravitational lensing for point-like light sources, we present a practical approach using the Jacobi equation and the Sachs bases. Additionally, we consider the dragging and geodesic precession of particles due to the warp bubble.
Reduced warp in torsion of reticulated foam due to Cosserat elasticity: experiment
NASA Astrophysics Data System (ADS)
Lakes, Roderic S.
2016-06-01
Warp of cross sections of square section bars in torsion is reduced in Cosserat elasticity in comparison with classical elasticity. Warp is observed experimentally to be substantially reduced, by about a factor of four compared with classical elasticity, in an open-cell polymer foam for which Cosserat elastic constants were previously determined. The observed warp in the foam is consistent with a prediction based on Cosserat elasticity. Concentration of strain in the foam is therefore reduced in comparison with classical elasticity.
Generalized warping effect in the dynamic analysis of beams of arbitrary cross section
NASA Astrophysics Data System (ADS)
Dikaros, I. C.; Sapountzakis, E. J.; Argyridi, A. K.
2016-05-01
In this paper a general formulation for the nonuniform warping dynamic analysis of beams of arbitrary simply or multiply connected cross section, under arbitrary external loading and general boundary conditions is presented taking into account the effects of rotary and warping inertia. The nonuniform warping distributions are taken into account by employing four independent warping parameters multiplying a shear warping function in each direction and two torsional warping functions, respectively, which are obtained by solving the corresponding boundary value problems, formulated exploiting the longitudinal local equilibrium equation. A shear stress "correction" is also performed in order to improve the stress field arising from the employed kinematical considerations. Ten initial boundary value problems are formulated with respect to the displacement and rotation components as well as to the independent warping parameters and solved using the Analog Equation Method, a Boundary Element Method based technique in combination with an appropriate time integration scheme. The warping functions and the geometric constants including the additional ones due to warping are evaluated employing a pure BEM approach.
Surface states in a 3D topological insulator: The role of hexagonal warping and curvature
Repin, E. V.; Burmistrov, I. S.
2015-09-15
We explore a combined effect of hexagonal warping and a finite effective mass on both the tunneling density of electronic surface states and the structure of Landau levels of 3D topological insulators. We find the increasing warping to transform the square-root van Hove singularity into a logarithmic one. For moderate warping, an additional logarithmic singularity and a jump in the tunneling density of surface states appear. By combining the perturbation theory and the WKB approximation, we calculate the Landau levels in the presence of hexagonal warping. We predict that due to the degeneracy removal, the evolution of Landau levels in the magnetic field is drastically modified.
Formation of warped disks by galactic flyby encounters. I. Stellar disks
Kim, Jeonghwan H.; An, Sung-Ho; Yoon, Suk-Jin; Peirani, Sebastien; Kim, Sungsoo; Ann, Hong Bae
2014-07-01
Warped disks are almost ubiquitous among spiral galaxies. Here we revisit and test the 'flyby scenario' of warp formation, in which impulsive encounters between galaxies are responsible for warped disks. Based on N-body simulations, we investigate the morphological and kinematical evolution of the stellar component of disks when galaxies undergo flyby interactions with adjacent dark matter halos. We find that the so-called 'S'-shaped warps can be excited by flybys and sustained for even up to a few billion years, and that this scenario provides a cohesive explanation for several key observations. We show that disk warp properties are governed primarily by the following three parameters: (1) the impact parameter, i.e., the minimum distance between two halos; (2) the mass ratio between two halos; and (3) the incident angle of the flyby perturber. The warp angle is tied up with all three parameters, yet the warp lifetime is particularly sensitive to the incident angle of the perturber. Interestingly, the modeled S-shaped warps are often non-symmetric depending on the incident angle. We speculate that the puzzling U- and L-shaped warps are geometrically superimposed S-types produced by successive flybys with different incident angles, including multiple interactions with a satellite on a highly elongated orbit.
Stone, Wesley W.; Gilliom, Robert J.
2012-01-01
Watershed Regressions for Pesticides (WARP) models, previously developed for atrazine at the national scale, are improved for application to the United States (U.S.) Corn Belt region by developing region-specific models that include watershed characteristics that are influential in predicting atrazine concentration statistics within the Corn Belt. WARP models for the Corn Belt (WARP-CB) were developed for annual maximum moving-average (14-, 21-, 30-, 60-, and 90-day durations) and annual 95th-percentile atrazine concentrations in streams of the Corn Belt region. The WARP-CB models accounted for 53 to 62% of the variability in the various concentration statistics among the model-development sites. Model predictions were within a factor of 5 of the observed concentration statistic for over 90% of the model-development sites. The WARP-CB residuals and uncertainty are lower than those of the National WARP model for the same sites. Although atrazine-use intensity is the most important explanatory variable in the National WARP models, it is not a significant variable in the WARP-CB models. The WARP-CB models provide improved predictions for Corn Belt streams draining watersheds with atrazine-use intensities of 17 kg/km2 of watershed area or greater.
Nobel Lecture. Aquaporin water channels.
Agre, Peter
2004-06-01
Thank you very much. I am humbled, I am delighted; I am honored. This is every scientist's dream: to give the Nobel Lecture in Stockholm. But I would not be honest if I did not tell you that I am having a little anxiety being on this platform. I have lectured a number of times in Sweden, and I thought I would share with you some events preceding a special lecture that I gave here a few years ago. Arriving at Arlanda Airport, I waited in line at the Pass Control behind a group of businessmen in suits with briefcases. I heard the first in line asked by the control officer to state the purpose of his visit to Sweden. When the man replied "business," the officer approved and stamped his passport. One at a time, each stepped forward and was asked the same thing; each answered "business" and was approved. Eventually it was my turn, and I was dressed in rumpled clothes after spending the night in the Economy Minus section of an SAS jetliner. The officer asked me the purpose of my visit, and I said "I am here to give the von Euler Lecture at Karolinska Institute." The officer immediately looked up, stared at me, and asked, "Are you nervous?" At that point I became intensely nervous and said "Yes, I am a little nervous." The officer looked up again and stated "Well, you should be!" So if the lecturers look a little nervous, the problem is at Arlanda. PMID:16209125
Practical strategies for effective lectures.
Lenz, Peter H; McCallister, Jennifer W; Luks, Andrew M; Le, Tao T; Fessler, Henry E
2015-04-01
Lecturing is an essential teaching skill for scientists and health care professionals in pulmonary, critical care, and sleep medicine. However, few medical or scientific educators have received training in contemporary techniques or technology for large audience presentation. Interactive lecturing outperforms traditional, passive-style lecturing in educational outcomes, and is being increasingly incorporated into large group presentations. Evidence-based techniques range from the very simple, such as inserting pauses for audience discussion, to more technologically advanced approaches such as electronic audience response systems. Alternative software platforms such as Prezi can overcome some of the visual limits that the ubiquitous PowerPoint imposes on complex scientific narratives, and newer technology formats can help foster the interactive learning environment. Regardless of the technology, adherence to good principles of instructional design, multimedia learning, visualization of quantitative data, and informational public speaking can improve any lecture. The storyline must be clear, logical, and simplified compared with how it might be prepared for scientific publication. Succinct outline and summary slides can provide a roadmap for the audience. Changes of pace, and summaries or other cognitive breaks inserted every 15-20 minutes can renew attention. Graphics that emphasize clear, digestible data graphs or images over tables, and simple, focused tables over text slides, are more readily absorbed. Text slides should minimize words, using simple fonts in colors that contrast to a plain background. Adherence to these well-established principles and addition of some new approaches and technologies will yield an engaging lecture worth attending. PMID:25746051
NASA Astrophysics Data System (ADS)
2011-11-01
Often I will listen to public radio on long drives when I am alone. Recently I happened to catch a program called "Don't Lecture Me" and it really caught my attention for several reasons. First, the speakers were all notable leaders in Physics Education Research such as Joe Redish, David Hestenes, and Eric Mazur. (See this month's WebSights column.) These folks are among many who have devoted their energies to understanding how students learn physics and how teachers can design classroom instruction and interactions to best meet the needs of learners. Second, on this particular trip, I had just observed a teacher whose class was very teacher-centered as the teacher lectured most of the class period. As we discussed this later, she expressed concern that she had to cover the material and didn't feel that she could do it without lecturing.
NASA Astrophysics Data System (ADS)
Blanton, Patricia
2011-11-01
Often I will listen to public radio on long drives when I am alone. Recently I happened to catch a program called ``Don't Lecture Me'' and it really caught my attention for several reasons. First, the speakers were all notable leaders in Physics Education Research such as Joe Redish, David Hestenes, and Eric Mazur. (See this month's WebSights column.) These folks are among many who have devoted their energies to understanding how students learn physics and how teachers can design classroom instruction and interactions to best meet the needs of learners. Second, on this particular trip, I had just observed a teacher whose class was very teacher-centered as the teacher lectured most of the class period. As we discussed this later, she expressed concern that she had to cover the material and didn't feel that she could do it without lecturing.
NASA Astrophysics Data System (ADS)
Hayasaki, K.; Sohn, B. W.; Okazaki, A. T.; Jung, T.; Zhao, G.; Naito, T.
2015-07-01
We study the warping and tearing of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on an eccentric orbit. The circumbinary disk is significantly misaligned with the binary orbital plane, and is subject to the time-dependent tidal torques. In principle, such a disk is warped and precesses, and is torn into mutually misaligned rings in the region, where the tidal precession torques are stronger than the local viscous torques. We derive the tidal-warp and tearing radii of the misaligned circumbinary disks around eccentric SMBH binaries. We find that in disks with the viscosity parameter α larger than a critical value depending on the disk aspect ratio, the disk warping appears outside the tearing radius. This condition is expressed for small amplitude warps as α > √H/(3r) for H/rlesssim0.1, where H is the disk scale height. If α < √H/(3r), only the disk tearing occurs because the tidal warp radius is inside the tearing radius, where most of disk material is likely to rapidly accrete onto SMBHs. In warped and torn disks, both the tidal-warp and the tearing radii most strongly depend on the binary semi-major axis, although they also mildly depend on the other orbital and disk parameters. This strong dependence enables us to estimate the semi-major axis, once the tidal warp or tearing radius is determined observationally: for the tidal warp radius of 0.1 pc, the semi-major axis is estimated to be ~10-2 pc for 107 Msolar black hole with typical orbital and disk parameters. We also briefly discuss the possibility that central objects of observed warped maser disks in active galactic nuclei are supermassive black hole binaries.
Warped dipole completed, with a tower of Higgs bosons
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Azatov, Aleksandr; Cui, Yanou; Randall, Lisa; Son, Minho
2015-06-01
In the context of warped extra-dimensional models which address both the Planck-weak- and flavor-hierarchies of the Standard Model (SM), it has been argued that certain observables can be calculated within the 5D effective field theory only with the Higgs field propagating in the bulk of the extra dimension, just like other SM fields. The related studies also suggested an interesting form of decoupling of the heavy Kaluza-Klein (KK) fermion states in the warped 5D SM in the limit where the profile of the SM Higgs approaches the IR brane. We demonstrate that a similar phenomenon occurs when we include the mandatory KK excitations of the SM Higgs in loop diagrams giving dipole operators for SM fermions, where the earlier work only considered the SM Higgs (zero mode). In particular, in the limit of a quasi IR-localized SM Higgs, the effect from summing over KK Higgs modes is unsuppressed (yet finite), in contrast to the naive expectation that KK Higgs modes decouple as their masses become large. In this case, a wide range of KK Higgs modes have quasi-degenerate masses and enhanced couplings to fermions relative to those of the SM Higgs, which contribute to the above remarkable result. In addition, we find that the total contribution from KK Higgs modes in general can be comparable to that from the SM Higgs alone. It is also interesting that KK Higgs couplings to KK fermions of the same chirality as the corresponding SM modes have an unsuppressed overall contribution, in contrast to the result from the earlier studies involving the SM Higgs. Our studies suggest that KK Higgs bosons are generally an indispensable part of the warped 5D SM, and their phenomenology such as signals at the LHC are worth further investigation.
Performance of resin transfer molded multiaxial warp knit composites
NASA Technical Reports Server (NTRS)
Dexter, H. Benson; Hasko, Gregory H.
1993-01-01
Composite materials that are subjected to complex loads have traditionally been fabricated with multidirectionally oriented prepreg tape materials. Some of the problems associated with this type of construction include low delamination resistance, poor out-of-plane strength, and labor intensive fabrication processes. Textile reinforced composites with through-the-thickness reinforcement have the potential to solve some of these problems. Recently, a relatively new class of noncrimp fabrics designated as multiaxial warp knits have been developed to minimize some of the high cost and damage tolerance concerns. Multiple stacks of warp knit fabrics can be knitted or stitched together to reduce layup labor cost. The through-the-thickness reinforcement can provide significant improvements in damage tolerance and out-of-plane strength. Multilayer knitted/stitched preforms, in conjunction with resin transfer molding (RTM), offer potential for significant cost savings in fabrication of primary aircraft structures. The objectives of this investigation were to conduct RTM processing studies and to characterize the mechanical behavior of composites reinforced with three multiaxial warp knit fabrics. The three fabrics investigated were produced by Hexcel and Milliken in the United States, and Saerbeck in Germany. Two resin systems, British Petroleum E9O5L and 3M PR 500, were characterized for RTM processing. The performance of Hexcel and Milliken quasi-isotropic knitted fabrics are compared to conventional prepreg tape laminates. The performance of the Saerbeck fabric is compared to uniweave wing skin layups being investigated by Douglas Aircraft Company in the NASA Advanced Composites Technology (ACT) program. Tests conducted include tension, open hole tension, compression, open hole compression, and compression after impact. The effects of fabric defects, such as misaligned fibers and gaps between tows, on material performance are also discussed. Estimated material and labor
TWOS - TIME WARP OPERATING SYSTEM, VERSION 2.5.1
NASA Technical Reports Server (NTRS)
Bellenot, S. F.
1994-01-01
The Time Warp Operating System (TWOS) is a special-purpose operating system designed to support parallel discrete-event simulation. TWOS is a complete implementation of the Time Warp mechanism, a distributed protocol for virtual time synchronization based on process rollback and message annihilation. Version 2.5.1 supports simulations and other computations using both virtual time and dynamic load balancing; it does not support general time-sharing or multi-process jobs using conventional message synchronization and communication. The program utilizes the underlying operating system's resources. TWOS runs a single simulation at a time, executing it concurrently on as many processors of a distributed system as are allocated. The simulation needs only to be decomposed into objects (logical processes) that interact through time-stamped messages. TWOS provides transparent synchronization. The user does not have to add any more special logic to aid in synchronization, nor give any synchronization advice, nor even understand much about how the Time Warp mechanism works. The Time Warp Simulator (TWSIM) subdirectory contains a sequential simulation engine that is interface compatible with TWOS. This means that an application designer and programmer who wish to use TWOS can prototype code on TWSIM on a single processor and/or workstation before having to deal with the complexity of working on a distributed system. TWSIM also provides statistics about the application which may be helpful for determining the correctness of an application and for achieving good performance on TWOS. Version 2.5.1 has an updated interface that is not compatible with 2.0. The program's user manual assists the simulation programmer in the design, coding, and implementation of discrete-event simulations running on TWOS. The manual also includes a practical user's guide to the TWOS application benchmark, Colliding Pucks. TWOS supports simulations written in the C programming language. It is designed
Orientifolds of warped throats from toric Calabi-Yau singularities
NASA Astrophysics Data System (ADS)
Retolaza, Ander; Uranga, Angel
2016-07-01
We study the complex deformations of orientifolds of D3-branes at toric CY singularities, using their description in terms of dimer diagrams. We describe orientifold quotients that have fixed lines or fixed points in the dimer, and characterize the possibilities to deform them in terms of the behaviour of zig-zag paths under the orientifold symmetry. The resulting models are holographic duals to warped throats with orientifold planes. Our systematic construction provides a general class of configurations which includes models recently appeared in the context of de Sitter uplift by nilpotent goldstino or dynamical supersymmetry breaking.
Evanescent gravitons in warped anti-de Sitter space
NASA Astrophysics Data System (ADS)
Giribet, Gaston; Vásquez, Yerko
2016-01-01
Besides black holes, the phase space of three-dimensional massive gravity about warped anti-de Sitter space contains solutions that decay exponentially in time. They describe evanescent graviton configurations that, while governed by a wave equation with nonvanishing effective mass, do not carry net gravitational energy. Explicit examples of such solutions have been found in the case of topologically massive gravity; here, we generalize them to a much more general ghost-free massive deformation, with the difference being that the decay rate gets corrected due to the presence of higher-order terms.
DISK AROUND STAR MAY BE WARPED BY UNSEEN PLANET
NASA Technical Reports Server (NTRS)
2002-01-01
NASA's Hubble Space Telescope has provided strong evidence for the existence of a roughly Jupiter-sized planet orbiting the star Beta Pictoris. Detailed Hubble images of the inner region of the 200-billion mile diameter dust disk encircling the star reveal an unexpected warp. Researchers say the warp can be best explained as caused by the gravitational pull of an unseen planet. The suspected planet would dwell within a five-billion mile wide clear zone in the center of the disk. This zone has long been suspected of harboring planets that swept it clear of debris, but the Hubble discovery provides more definitive evidence that a planet is there. (Alternative theories suggest the clear zone is empty because it is too warm for ice particles to exist.) 'We were surprised to find that the innermost region of the disk is orbiting in a different plane from the rest of the disk,' says Chris Burrows (Space Telescope Science Institute, Baltimore, Maryland, and the European Space Agency) who is presenting his results at the meeting of the American Astronomical Society in San Antonio, Texas. As he analyzed Hubble images, taken in January 1995 with the Wide Field Planetary Camera 2, Burrows discovered an unusual bulge in the nearly edge-on disk, which was mirrored on the other side of the star. 'Such a warp cannot last for very long,' says Burrows. 'This means that something is still twisting the disk and keeping out of a basic flat shape.' 'The presence of the warp is strong though indirect evidence for the existence of planets in this system. If Beta Pictoris had a solar system like ours, it would produce a warp like the one we see.' Burrows concludes, 'The Beta Pictoris system seems to contain at least one planet not too dissimilar from Jupiter in size and orbit. Rocky planets like Earth might circle Beta Pictoris as well. However, there is no evidence for these yet. Any planet will be at least a billion- times fainter than the star, and presently impossible to view directly
The Alcubierre Warp Drive in Higher Dimensional Spacetime
NASA Astrophysics Data System (ADS)
White, H. G.; Davis, E. W.
2006-01-01
The canonical form of the Alcubierre warp drive metric is considered to gain insight into the mathematical mechanism triggering the effect. A parallel with the Chung-Freese spacetime metric is drawn to demonstrate that the spacetime expansion boost can be considered a 3 + 1 on-brane simplification for higher dimensional geometric effects. The implications for baryonic matter of higher dimensional spacetime, in conjunction with the Alcubierre metric, are used to illustrate an equation of state for dark energy. Finally, this combined model will then be used to outline a theoretical framework for negative pressure (an alternative to negative energy) and a conceptual lab experiment is described.
DISK AROUND STAR MAY BE WARPED BY UNSEEN PLANET
NASA Technical Reports Server (NTRS)
2002-01-01
NASA's Hubble Space Telescope has provided strong evidence for the existence of a roughly Jupiter-sized planet orbiting the star Beta Pictoris. Detailed Hubble images of the inner region of the 200-billion mile diameter dust disk encircling the star reveal an unexpected warp. Researchers say the warp can be best explained as caused by the gravitational pull of an unseen planet. The suspected planet would dwell within a five-billion mile wide clear zone in the center of the disk. This zone has long been suspected of harboring planets that swept it clear of debris, but the Hubble discovery provides more definitive evidence that a planet is there. (Alternative theories suggest the clear zone is empty because it is too warm for ice particles to exist.) 'We were surprised to find that the innermost region of the disk is orbiting in a different plane from the rest of the disk,' says Chris Burrows (Space Telescope Science Institute, Baltimore, Maryland, and the European Space Agency) who is presenting his results at the meeting of the American Astronomical Society in San Antonio, Texas. As he analyzed Hubble images, taken in January 1995 with the Wide Field Planetary Camera 2, Burrows discovered an unusual bulge in the nearly edge-on disk, which was mirrored on the other side of the star. 'Such a warp cannot last for very long,' says Burrows. 'This means that something is still twisting the disk and keeping out of a basic flat shape.' 'The presence of the warp is strong though indirect evidence for the existence of planets in this system. If Beta Pictoris had a solar system like ours, it would produce a warp like the one we see.' Burrows concludes, 'The Beta Pictoris system seems to contain at least one planet not too dissimilar from Jupiter in size and orbit. Rocky planets like Earth might circle Beta Pictoris as well. However, there is no evidence for these yet. Any planet will be at least a billion- times fainter than the star, and presently impossible to view directly
3D volume reconstruction of a mouse brain histological sections using warp filtering
Ju, Tao; Warren, Joe; Carson, James P.; Bello, Musodiq; Kakadiaris, Ioannis; Chiu, Wah; Thaller, Christina; Eichele, Gregor
2006-09-30
Sectioning tissues for optical microscopy often introduces upon the resulting sections distortions that make 3D reconstruction difficult. Here we present an automatic method for producing a smooth 3D volume from distorted 2D sections in the absence of any undistorted references. The method is based on pairwise elastic image warps between successive tissue sections, which can be computed by 2D image registration. Using a Gaussian filter, an average warp is computed for each section from the pairwise warps in a group of its neighboring sections. The average warps deform each section to match its neighboring sections, thus creating a smooth volume where corresponding features on successive sections lie close to each other. The proposed method can be used with any existing 2D image registration method for 3D reconstruction. In particular, we present a novel image warping algorithm based on dynamic programming that extends Dynamic Time Warping in 1D speech recognition to compute pairwise warps between high-resolution 2D images. The warping algorithm efficiently computes a restricted class of 2D local deformations that are characteristic between successive tissue sections. Finally, a validation framework is proposed and applied to evaluate the quality of reconstruction using both real sections and a synthetic volume.
Mechanical Analyses of Real Time Warp Yarn Tensions in Size-Free Weaving
Technology Transfer Automated Retrieval System (TEKTRAN)
A 100% cotton, size-less common warp was used to study the real-time tensions of single strands of the warp during weaving on a high-speed weaving machine. The machine was operated under almost mill-like conditions. In order to investigate the independent effects of the weaving speed and fabric cons...
Warping error analysis and reduction for depth-image-based rendering in 3DTV
NASA Astrophysics Data System (ADS)
Do, Luat; Zinger, Sveta; de With, Peter H. N.
2011-03-01
Interactive free-viewpoint selection applied to a 3D multi-view video signal is an attractive feature of the rapidly developing 3DTV media. In recent years, significant research has been done on free-viewpoint rendering algorithms which mostly have similar building blocks. In our previous work, we have analyzed the principal building blocks of most recent rendering algorithms and their contribution to the overall rendering quality. We have discovered that the first step, Warping determines the basic quality level of the complete rendering chain. In this paper, we have analyzed the warping step in more detail since it leads to ways for improvement. We have observed that the accuracy of warping is mainly determined by two factors which are sampling and rounding errors when performing pixel-based warping and quantization errors of depth maps. For each error factor, we have proposed a technique that can reduce the errors and thus increase the warping quality. Pixel-based warping errors are reduced by employing supersampling at the reference and virtual images and we decrease depth map errors by creating depth maps with more quantization levels. The new techniques are evaluated with two series of experiments using real-life and synthetic data. From these experiments, we have observed that reducing warping errors may increases the overall rendering quality and that the impact of errors due to pixel-based warping is much larger than that of errors due to depth quantization.
Revisiting Mathematics Education: China Lectures.
ERIC Educational Resources Information Center
Freudenthal, Hans
This book represents a compilation of the views and ideas of the late Hans Freudenthal, representing his last major contribution to the field of mathematics education. Rather than a presentation of new views, Freudenthal selected and streamlined old ideas, many gathered from his lectures in China, and formed a review of questions and issues in…
Teaching More by Lecturing Less
ERIC Educational Resources Information Center
Knight, Jennifer K.; Wood, William B.
2005-01-01
We carried out an experiment to determine whether student learning gains in a large, traditionally taught, upper-division lecture course in developmental biology could be increased by partially changing to a more interactive classroom format. In two successive semesters, we presented the same course syllabus using different teaching styles: in…
Interacting binaries. Lecture notes 1992.
NASA Astrophysics Data System (ADS)
Nussbaumer, H.; Orr, A.
These lecture notes represent a unique collection of information and references on current research on interacting binaries: S. N. Shore puts the emphasis on observations and their connection to relevant physics. He also discusses symbiotic stars. Cataclysmic variables are the subject of M. Livio's course, whereas E. P. J. van den Heuvel concentrates on more massive binaries and X-ray binaries.
Lectures of Fermi liquid theory
Bedell, K.S.
1993-01-01
The Fermi liquid theory was first introduced by Landau in 1956 to provide a theoretical basis for the properties of strongly correlated Fermi systems. This theory has proven to be crucial for our understanding of a broad range of materials. These include liquid [sup 3]He, [sup 3]He-[sup 4]He mixtures, simple metals, heavy-fermions, and nuclear matter to name a few. In the high temperature superconductors questions have been raised regarding the applicability of Fermi liquid theory to the normal state behavior of these materials. I will not address this issue in these lectures. My focus will be to summarize the foundations of this theory and to explore the consequences. These lectures are in part a summary of the excellent review article by Baym and Pethick and the books by Pines and Nozieres and Baym and Pethick. They include as well a summary of some articles that I have authored and co-authored. In the main body of the lectures I will not make any additional references to the books or articles. In the absence of reading the original materials, my lectures should provide the essentials of a mini-course in Fermi liquid theory.
Lectures of Fermi liquid theory
Bedell, K.S.
1993-07-01
The Fermi liquid theory was first introduced by Landau in 1956 to provide a theoretical basis for the properties of strongly correlated Fermi systems. This theory has proven to be crucial for our understanding of a broad range of materials. These include liquid {sup 3}He, {sup 3}He-{sup 4}He mixtures, simple metals, heavy-fermions, and nuclear matter to name a few. In the high temperature superconductors questions have been raised regarding the applicability of Fermi liquid theory to the normal state behavior of these materials. I will not address this issue in these lectures. My focus will be to summarize the foundations of this theory and to explore the consequences. These lectures are in part a summary of the excellent review article by Baym and Pethick and the books by Pines and Nozieres and Baym and Pethick. They include as well a summary of some articles that I have authored and co-authored. In the main body of the lectures I will not make any additional references to the books or articles. In the absence of reading the original materials, my lectures should provide the essentials of a mini-course in Fermi liquid theory.
How to Podcast Campus Lectures
ERIC Educational Resources Information Center
Read, Brock
2007-01-01
Many college classrooms these days may as well have lighted signs over their doors that read "On Air" or "Recording in Progress." A growing number of professors are recording their lectures and making them available as podcasts--regularly updated sets of audio files that students can download to their computers or MP3 players. Some campus…
Applied Fluid Mechanics. Lecture Notes.
ERIC Educational Resources Information Center
Gregg, Newton D.
This set of lecture notes is used as a supplemental text for the teaching of fluid dynamics, as one component of a thermodynamics course for engineering technologists. The major text for the course covered basic fluids concepts such as pressure, mass flow, and specific weight. The objective of this document was to present additional fluids…
Teaching More by Lecturing Less
2005-01-01
We carried out an experiment to determine whether student learning gains in a large, traditionally taught, upper-division lecture course in developmental biology could be increased by partially changing to a more interactive classroom format. In two successive semesters, we presented the same course syllabus using different teaching styles: in fall 2003, the traditional lecture format; and in spring 2004, decreased lecturing and addition of student participation and cooperative problem solving during class time, including frequent in-class assessment of understanding. We used performance on pretests and posttests, and on homework problems to estimate and compare student learning gains between the two semesters. Our results indicated significantly higher learning gains and better conceptual understanding in the more interactive course. To assess reproducibility of these effects, we repeated the interactive course in spring 2005 with similar results. Our findings parallel results of similar teaching-style comparisons made in other disciplines. On the basis of this evidence, we propose a general model for teaching large biology courses that incorporates interactive engagement and cooperative work in place of some lecturing, while retaining course content by demanding greater student responsibility for learning outside of class. PMID:16341257
A Lecturer's Optimal Time Allocation Policy.
ERIC Educational Resources Information Center
Epstein, Gil S.; Spiegel, Uriel
1996-01-01
Lecturers are responsible for guiding their students outside the classroom. However, many students who can solve their problems independently often still seek lecturers' guidance, resulting in negative externalities. This paper examines the lecturer's attempts to minimize the negative effects of unnecessary guidance, focusing on the optimal time…
Experiences in Personal Lecture Video Capture
ERIC Educational Resources Information Center
Chandra, Surendar
2011-01-01
The ability of lecture videos to capture the different modalities of a class interaction make them a good review tool. Multimedia capable devices are ubiquitous among contemporary students. Many lecturers are leveraging this popularity by distributing videos of lectures. They depend on the university to provide the video capture infrastructure.…
Investigating Quality of Undergraduate Mathematics Lectures
ERIC Educational Resources Information Center
Bergsten, Christer
2007-01-01
The notion of quality in undergraduate mathematics lectures is examined by using theoretical notions and research results from the literature and empirical data from a case study on lecturing on limits of functions. A systemic triangular model is found to catch critical quality aspects of a mathematics lecture, consisting of mathematical…
Interactive Lecture Discourse for University EFL Students
ERIC Educational Resources Information Center
Morell, Teresa
2004-01-01
Interactive lectures play an important role in improving comprehension and in enhancing communicative competence in the English language for EFL university students taking content lecture courses. This article considers the interactive discourse in lectures of the English Studies Department at the University of Alicante, Spain. It describes an…
Stone, Wesley W.; Gilliom, Robert J.
2011-01-01
The 95-percent prediction intervals are well within a factor of 10 above and below the predicted concentration statistic. WARP-CB model predictions were within a factor of 5 of the observed concentration statistic for over 90 percent of the model-development sites. The WARP-CB residuals and uncertainty are lower than those of the National WARP model for the same sites. The WARP-CB models provide improved predictions of the probability of exceeding a specified criterion or benchmark for Corn Belt streams draining watersheds with high atrazine use intensities; however, National WARP models should be used for Corn Belt streams where atrazine use intensities are less than 17 kg/km2 of watershed area.
Adverse effects of template-based warping on spatial fMRI analysis
NASA Astrophysics Data System (ADS)
Ng, Bernard; Abugharbieh, Rafeef; McKeown, Martin J.
2009-02-01
Conventional voxel-based group analysis of functional magnetic resonance imaging (fMRI) data typically requires warping each subject's brain images onto a common template to create an assumed voxel correspondence. The implicit assumption is that aligning the anatomical structures would correspondingly align the functional regions of the subjects. However, due to anatomical and functional inter-subject variability, mis-registration often occurs. Moreover, wholebrain warping is likely to distort the spatial patterns of activation, which have been shown to be important markers of task-related activation. To reduce the amount of mis-registration and distortions, warping at the brain region level has recently been proposed. In this paper, we investigate the effects of both whole-brain and region-level warping on the spatial patterns of activation statistics within certain regions of interests (ROIs). We have chosen to examine the bilateral thalami and cerebellar hemispheres during a bulb-squeezing experiment, as these regions are expected to incur taskrelated activation changes. Furthermore, the appreciable size difference between the thalamus and cerebellum allows for exploring the effects of warping on various ROI sizes. By applying our recently proposed 3D moment-based invariant spatial features to characterize the spatial pattern of fMRI activation statistics, we demonstrate that whole-brain warping generally reduced discriminability of task-related activation differences. Applying the same spatial analysis to ROIs warped at the region level showed some improvements over whole-brain warping, but warp-free analysis resulted in the best performance. We hence suggest that spatial analysis of fMRI data that includes spatial warping to a common space must be interpreted with caution.
Stone, Wesley W.; Crawford, Charles G.; Gilliom, Robert J.
2013-01-01
Watershed Regressions for Pesticides for multiple pesticides (WARP-MP) are statistical models developed to predict concentration statistics for a wide range of pesticides in unmonitored streams. The WARP-MP models use the national atrazine WARP models in conjunction with an adjustment factor for each additional pesticide. The WARP-MP models perform best for pesticides with application timing and methods similar to those used with atrazine. For other pesticides, WARP-MP models tend to overpredict concentration statistics for the model development sites. For WARP and WARP-MP, the less-than-ideal sampling frequency for the model development sites leads to underestimation of the shorter-duration concentration; hence, the WARP models tend to underpredict 4- and 21-d maximum moving-average concentrations, with median errors ranging from 9 to 38% As a result of this sampling bias, pesticides that performed well with the model development sites are expected to have predictions that are biased low for these shorter-duration concentration statistics. The overprediction by WARP-MP apparent for some of the pesticides is variably offset by underestimation of the model development concentration statistics. Of the 112 pesticides used in the WARP-MP application to stream segments nationwide, 25 were predicted to have concentration statistics with a 50% or greater probability of exceeding one or more aquatic life benchmarks in one or more stream segments. Geographically, many of the modeled streams in the Corn Belt Region were predicted to have one or more pesticides that exceeded an aquatic life benchmark during 2009, indicating the potential vulnerability of streams in this region.
Particle Motion and Perturbed Dynamical System in Warped Product Spacetimes
NASA Astrophysics Data System (ADS)
Bhattacharya, Pinaki; Guha, Sarbari
2016-07-01
In this paper we have used the dynamical systems analysis to study the dynamics of a five-dimensional universe in the form of a warped product spacetime with a spacelike dynamic extra dimension. We have decomposed the geodesic equations to get the motion along the extra dimension and have studied the associated dynamical system when the cross-diagonal element of the Einstein tensor vanishes, and also when it is non-vanishing. Introducing the concept of an energy function along the phase path in terms of the extra-dimensional coordinate, we have examined how the energy function depends on the warp factor. The energy function serves as a measure of the amount of perturbation of geodesic paths along the extra dimension in the region close to the brane. Then we studied the geodesic motion under a conventional metric perturbation in the form of homothetic motion and conformal motion and examined the nature of critical points for a Mashhoon-Wesson-type metric, for timelike and null geodesics when the cross-diagonal term of the Einstein tensor vanishes. Finally we investigated the motion for null and timelike geodesics under the condition when the cross-diagonal element of the Einstein tensor is non-vanishing and examined the effects of perturbation on the critical points of the dynamical system.
Time warp operating system version 2.7 internals manual
NASA Technical Reports Server (NTRS)
1992-01-01
The Time Warp Operating System (TWOS) is an implementation of the Time Warp synchronization method proposed by David Jefferson. In addition, it serves as an actual platform for running discrete event simulations. The code comprising TWOS can be divided into several different sections. TWOS typically relies on an existing operating system to furnish some very basic services. This existing operating system is referred to as the Base OS. The existing operating system varies depending on the hardware TWOS is running on. It is Unix on the Sun workstations, Chrysalis or Mach on the Butterfly, and Mercury on the Mark 3 Hypercube. The base OS could be an entirely new operating system, written to meet the special needs of TWOS, but, to this point, existing systems have been used instead. The base OS's used for TWOS on various platforms are not discussed in detail in this manual, as they are well covered in their own manuals. Appendix G discusses the interface between one such OS, Mach, and TWOS.
Emission Line Profiles of Warped Disks in a Kerr Spacetime
NASA Astrophysics Data System (ADS)
Yang, X. L.; Wang, J. C.
2013-11-01
The computations of emission line profiles of a warped disk around a Kerr black hole are discussed in this paper, which can be divided into two parts. In the first part, the geodesic motion in a Kerr spacetime and its equations with integral forms are presented. The equations are solved with the Weierstrass' elliptic functions and integrals. Making use of the elliptic functions, the Boyer-Lindquist (B-L) coordinates and the affine parameter σ are expressed semi-analytically as the functions of the parameter p. Then a code named ynogk (Yunnan Observatory Geodesic Kerr) is introduced based on the above discussions to calculate the null geodesics fast in a Kerr spacetime. In the second part of the paper, as an application of ynogk, the emission line profiles of a warped disk are investigated in detail. Here the structure model of the disk is specified according to the results of Bardeen and Petterson in 1975, and the line profiles are computed with the ray-tracing method. Finally, the discussions and conclusions of the computing results are presented, which indicate that the line profiles are dependent mainly on the inclination and azimuthal angles of the observer and the index of emissivity, and have the three-horn even multiple-horn structures comparing to those of a standard thin accretion disk.
Warped conformal field theory as lower spin gravity
NASA Astrophysics Data System (ADS)
Hofman, Diego M.; Rollier, Blaise
2015-08-01
Two dimensional Warped Conformal Field Theories (WCFTs) may represent the simplest examples of field theories without Lorentz invariance that can be described holographically. As such they constitute a natural window into holography in non-AdS space-times, including the near horizon geometry of generic extremal black holes. It is shown in this paper that WCFTs posses a type of boost symmetry. Using this insight, we discuss how to couple these theories to background geometry. This geometry is not Riemannian. We call it Warped Geometry and it turns out to be a variant of a Newton-Cartan structure with additional scaling symmetries. With this formalism the equivalent of Weyl invariance in these theories is presented and we write two explicit examples of WCFTs. These are free fermionic theories. Lastly we present a systematic description of the holographic duals of WCFTs. It is argued that the minimal setup is not Einstein gravity but an SL (2, R) × U (1) Chern-Simons Theory, which we call Lower Spin Gravity. This point of view makes manifest the definition of boundary for these non-AdS geometries. This case represents the first step towards understanding a fully invariant formalism for WN field theories and their holographic duals.
Dynamics of warped flux compactifications with backreacting antibranes
NASA Astrophysics Data System (ADS)
Junghans, Daniel
2014-06-01
We revisit the effective low-energy dynamics of the volume modulus in warped flux compactifications with anti-D3-branes in order to analyze the prospects for metastable de Sitter vacua and brane inflation along the lines of KKLT/KKLMMT. At the level of the ten-dimensional supergravity solution, antibranes in flux backgrounds with opposite charge are known to source singular terms in the energy densities of the bulk fluxes, which led to a debate on the consistency of such constructions in string theory. A straightforward yet nontrivial check of the singular solution is to verify that its dimensional reduction in the large-volume limit reproduces the four-dimensional low-energy dynamics expected from known results where the antibranes are treated as a probe. Taking into account the antibrane backreaction in the effective scalar potential, we find that both the volume scaling and the coefficient of the antibrane uplift term are in exact agreement with the probe potential if the singular fluxes satisfy a certain near-brane boundary condition. This condition can be tested explicitly and may thus help to decide whether flux singularities should be interpreted as pathological or benign features of flux compactifications with antibranes. Throughout the paper, we also comment on a number of subtleties related to the proper definition of warped effective field theory with antibranes.
Survival of scalar zero modes in warped extra dimensions
George, Damien P.
2011-05-15
Models with an extra dimension generally contain background scalar fields in a nontrivial configuration, whose stability must be ensured. With gravity present, the extra dimension is warped by the scalars, and the spin-0 degrees of freedom in the metric mix with the scalar perturbations. Where possible, we formally solve the coupled Schroedinger equations for the zero modes of these spin-0 perturbations. When specializing to the case of two scalars with a potential generated by a superpotential, we are able to fully solve the system. We show how these zero modes can be used to construct a solution matrix, whose eigenvalues tell whether a normalizable zero mode exists, and how many negative mass modes exist. These facts are crucial in determining stability of the corresponding background configuration. We provide examples of the general analysis for domain-wall models of an infinite extra dimension and domain-wall soft-wall models. For five-dimensional models with two scalars constructed using a superpotential, we show that a normalizable zero mode survives, even in the presence of warped gravity. Such models, which are widely used in the literature, are therefore phenomenologically unacceptable.
Point-based warping with optimized weighting factors of displacement vectors
NASA Astrophysics Data System (ADS)
Pielot, Ranier; Scholz, Michael; Obermayer, Klaus; Gundelfinger, Eckart D.; Hess, Andreas
2000-06-01
The accurate comparison of inter-individual 3D image brain datasets requires non-affine transformation techniques (warping) to reduce geometric variations. Constrained by the biological prerequisites we use in this study a landmark-based warping method with weighted sums of displacement vectors, which is enhanced by an optimization process. Furthermore, we investigate fast automatic procedures for determining landmarks to improve the practicability of 3D warping. This combined approach was tested on 3D autoradiographs of Gerbil brains. The autoradiographs were obtained after injecting a non-metabolized radioactive glucose derivative into the Gerbil thereby visualizing neuronal activity in the brain. Afterwards the brain was processed with standard autoradiographical methods. The landmark-generator computes corresponding reference points simultaneously within a given number of datasets by Monte-Carlo-techniques. The warping function is a distance weighted exponential function with a landmark- specific weighting factor. These weighting factors are optimized by a computational evolution strategy. The warping quality is quantified by several coefficients (correlation coefficient, overlap-index, and registration error). The described approach combines a highly suitable procedure to automatically detect landmarks in autoradiographical brain images and an enhanced point-based warping technique, optimizing the local weighting factors. This optimization process significantly improves the similarity between the warped and the target dataset.
TASI 2006 Lectures on Leptogenesis
Chen, Mu-Chun; /Fermilab /UC, Irvine
2007-03-01
The origin of the asymmetry between matter and anti-matter of the Universe has been one of the great challenges in particle physics and cosmology. Leptogenesis as a mechanism for generating the cosmological baryon asymmetry of the Universe has gained significant interests ever since the advent of the evidence of non-zero neutrino masses. In these lectures presented at TASI 2006, I review various realizations of leptogenesis and allude to recent developments in this subject.
Three Lectures on Hadron Physics
NASA Astrophysics Data System (ADS)
Roberts, Craig D.
2016-04-01
These lectures explain that comparisons between experiment and theory can expose the impact of running couplings and masses on hadron observables and thereby aid materially in charting the momentum dependence of the interaction that underlies strong-interaction dynamics. The series begins with a primer on continuum QCD, which introduces some of the basic ideas necessary in order to understand the use of Schwinger functions as a nonperturbative tool in hadron physics. It continues with a discussion of confinement and dynamical symmetry breaking (DCSB) in the Standard Model, and the impact of these phenomena on our understanding of condensates, the parton structure of hadrons, and the pion electromagnetic form factor. The final lecture treats the problem of grand unification; namely, the contemporary use of Schwinger functions as a symmetry-preserving tool for the unified explanation and prediction of the properties of both mesons and baryons. It reveals that DCSB drives the formation of diquark clusters in baryons and sketches a picture of baryons as bound-states with Borromean character. Planned experiments are capable of validating the perspectives outlined in these lectures.
Geometric finiteness, holography and quasinormal modes for the warped AdS3 black hole
NASA Astrophysics Data System (ADS)
Gupta, Kumar S.; Harikumar, E.; Sen, Siddhartha; Sivakumar, M.
2010-08-01
We show that there exists a precise kinematical notion of holography for the Euclidean warped AdS3 black hole. This follows from the fact that the Euclidean warped AdS3 black hole spacetime is a geometrically finite hyperbolic manifold. For such manifolds a theorem of Sullivan provides a one-to-one correspondence between the hyperbolic structure in the bulk and the conformal structure of its boundary. Using this theorem we obtain the holographic quasinormal modes for the warped AdS3 black hole.
Warped AdS3 , dS3 , and flows from N =(0 ,2 ) SCFTs
NASA Astrophysics Data System (ADS)
O'Colgáin, Eoin
2015-05-01
We present the general form of all timelike supersymmetric solutions to three-dimensional U (1 )3 gauged supergravity, a known consistent truncation of string theory. We uncover a rich vacuum structure, including an infinite class of new timelike-warped AdS3 (Gödel) and timelike-warped dS3 critical points. We outline the construction of supersymmetric flows, driven by irrelevant scalar operators in the SCFT, which interpolate between critical points. For flows from AdS3 to Gödel, the natural candidate for the central charge decreases along the flow. Flows to timelike-warped dS3 exhibit topology change.
Warped AdS3/dipole-CFT duality
NASA Astrophysics Data System (ADS)
Song, Wei; Strominger, Andrew
2012-05-01
String theory contains solutions with {{SL}}( {{2},{R}} ){{R}} × {{U}}{( {1} )_L} -invariant warped AdS3 (WAdS3) factors arising as continuous deformations of ordinary AdS3 factors. We propose that some of these are holographically dual to the IR limits of nonlocal dipole-deformed 2D D-brane gauge theories, referred to as "dipole CFTs". Neither the bulk nor boundary theories are currently well-understood, and consequences of the proposed duality for both sides is investigated. The bulk entropy-area law suggests that dipole CFTs have (at large N) a high-energy density of states which does not depend on the deformation parameter. Putting the boundary theory on a spatial circle leads to closed timelike curves in the bulk, suggesting a relation of the latter to dipole-type nonlocality.
Supersymmetric warped AdS in extended topologically massive supergravity
NASA Astrophysics Data System (ADS)
Deger, N. S.; Kaya, A.; Samtleben, H.; Sezgin, E.
2014-07-01
We determine the most general form of off-shell N=(1,1) supergravity field configurations in three dimensions by requiring that at least one off-shell Killing spinor exists. We then impose the field equations of the topologically massive off-shell supergravity and find a class of solutions whose properties crucially depend on the norm of the auxiliary vector field. These are spacelike-squashed and timelike-stretched AdS3 for the spacelike and timelike norms, respectively. At the transition point where the norm vanishes, the solution is null warped AdS3. This occurs when the coefficient of the Lorentz-Chern-Simons term is related to the AdS radius by μℓ=2. We find that the spacelike-squashed AdS3 can be modded out by a suitable discrete subgroup of the isometry group, yielding an extremal black hole solution which avoids closed timelike curves.
B-Factory Signals for a Warped Extra Dimension
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Perez, Gilad; Soni, Amarjit
2004-11-01
We study predictions for B physics in a class of warped extra dimension models recently introduced, where few (˜3) TeV Kaluza-Klein masses are consistent with electroweak data due to custodial symmetry. As in the standard model (SM), flavor violations arise due to the heavy top quark leading to striking signals: (i)New physics contributions to ΔF=2 transitions are comparable to the SM, so the success of the SM unitarity triangle fit is a “coincidence.” Thus, clean extractions of unitarity angles are likely to be affected, in addition to O(1) deviation from the SM prediction in Bs mixing. (ii)O(1) deviation from various SM predictions for B→Xsl+l-. (iii)Large mixing-induced CP asymmetry in radiative B decays. Also, the neutron electric dipole moment is roughly 20 times larger than the current bound so that this framework has a “CP problem.”
B-Factory Signals for a Warped Extra Dimension
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh
2005-04-01
I will discuss flavor physics in a warped (curved) extra dimension. In this model, the profiles of fermions in the extra dimension explain hierarchies in fermion masses. Moreover, there is an analog of GIM mechanism with first and second generations resulting in suppressed contributions to flavor changing neutral currents. Just as in the SM, the GIM mechanism is violated by inclusion of the heavy top quark, in turn, leading to striking signals at B-factories such as O(1) effects in semileptonic and radiative B decays and Bsmixing. Remarkably, this model can be interpreted as dual to a 4D composite Higgs model. Thus, the upshot is that a 4D strongly interacting Higgs sector can solve flavor puzzle with suppressed flavor-violation and be tested at B factories.
Warping and interactions of vortices in exciton-polariton condensates
NASA Astrophysics Data System (ADS)
Toledo-Solano, M.; Mora-Ramos, M. E.; Figueroa, A.; Rubo, Y. G.
2014-01-01
We investigate the properties of the vortex singularities in two-component exciton-polariton condensates in semiconductor microcavities in the presence of transverse-electric-transverse-magnetic (TE-TM) splitting of the lower polariton branch. This splitting does not change qualitatively the basic (lemon and star) geometry of half-quantum vortices (HQVs), but results in warping of both the polarization field and the supercurrent streamlines around these entities. The TE-TM splitting has a pronounced effect on the HQV energies and interactions, as well as on the properties of integer vortices, especially on the energy of the hedgehog polarization vortex. The energy of this vortex can become smaller than the energies of HQVs. This leads to modification of the Berezinskii-Kosterlitz-Thouless transition from the proliferation of half-vortices to the proliferation of hedgehog-based vortex molecules.
Near-horizon geometry and warped conformal symmetry
NASA Astrophysics Data System (ADS)
Afshar, Hamid; Detournay, Stéphane; Grumiller, Daniel; Oblak, Blagoje
2016-03-01
We provide boundary conditions for three-dimensional gravity including boosted Rindler spacetimes, representing the near-horizon geometry of non-extremal black holes or flat space cosmologies. These boundary conditions force us to make some unusual choices, like integrating the canonical boundary currents over retarded time and periodically identifying the latter. The asymptotic symmetry algebra turns out to be a Witt algebra plus a twisted u(1) current algebra with vanishing level, corresponding to a twisted warped CFT that is qualitatively different from the ones studied so far in the literature. We show that this symmetry algebra is related to BMS by a twisted Sugawara construction and exhibit relevant features of our theory, including matching micro- and macroscopic calculations of the entropy of zero-mode solutions. We confirm this match in a generalization to boosted Rindler-AdS. Finally, we show how Rindler entropy emerges in a suitable limit.
Signals of Warped Extra Dimensions at the LHC
Osland, P.; Pankov, A. A.; Tsytrinov, A. V.; Paver, N.
2010-12-22
We discuss the signatures of the spin-2 graviton excitations predicted by the Randall-Sundrum model with one warped extra dimension, in dilepton and diphoton production at LHC. By using a specific angular analysis, we assess the ranges in mass and coupling constant where such gravitons can be discriminated against competitor spin-1 and spin-0 objects, that potentially could manifest themselves in these processes with the same mass and rate of events. Depending on the value of the coupling constant to quarks and leptons, the numerical results indicate graviton identification mass ranges up to 1.1-2.4 TeV and 1.6-3.2 TeV for LHC nominal energy of 14 TeV and time-integrated luminosity of 10 and 100fb{sup -1}, respectively.
Higgs boson production and decay in 5D warped models
NASA Astrophysics Data System (ADS)
Frank, Mariana; Pourtolami, Nima; Toharia, Manuel
2016-03-01
We calculate the production and decay rates of the Higgs boson at the LHC in the context of general five-dimensional warped scenarios with a spacetime background modified from the usual AdS5 , with Standard Model (SM) fields propagating in the bulk. We extend previous work by considering the full flavor structure of the SM, and thus including all possible flavor effects coming from mixings with heavy fermions. We proceed in three different ways, first by only including two complete Kaluza-Klein (KK) levels (15 ×15 fermion mass matrices), then including three complete KK levels (21 ×21 fermion mass matrices) and finally we compare with the effect of including the infinite (full) KK towers. We present numerical results for the Higgs production cross section via gluon fusion and Higgs decay branching fractions in both the modified metric scenario and in the usual Randall-Sundrum metric scenario.
Agitating mass transfer with a warped disc's shadow
NASA Astrophysics Data System (ADS)
Cambier, H.
2015-10-01
For compact objects fed by Roche lobe overflow, accretion-generated X-rays irradiating the donor star can alter gas flow towards the Lagrange point thus varying mass transfer. The latest work specific to this topic consists of simple yet insightful two-dimensional hydrodynamics simulations stressing the role of global flow. To explore how a time-varying disc shadow affects mass transfer, I generalize the geometry, employ a robust hydrodynamics solver, and use phase space analysis near the nozzle to include coriolis lift there. Without even exposing the nozzle, a warped disc's shadow can drive mass transfer cycles by shifting the equatorial edges of the irradiation patches in turns: drawing in denser ambient gas before sweeping it into the nozzle. Other important effects remain missing in two-dimensional models, which I discuss along with prospects for more detailed yet efficient models.
SPACE WARPS - I. Crowdsourcing the discovery of gravitational lenses
NASA Astrophysics Data System (ADS)
Marshall, Philip J.; Verma, Aprajita; More, Anupreeta; Davis, Christopher P.; More, Surhud; Kapadia, Amit; Parrish, Michael; Snyder, Chris; Wilcox, Julianne; Baeten, Elisabeth; Macmillan, Christine; Cornen, Claude; Baumer, Michael; Simpson, Edwin; Lintott, Chris J.; Miller, David; Paget, Edward; Simpson, Robert; Smith, Arfon M.; Küng, Rafael; Saha, Prasenjit; Collett, Thomas E.
2016-01-01
We describe SPACE WARPS, a novel gravitational lens discovery service that yields samples of high purity and completeness through crowdsourced visual inspection. Carefully produced colour composite images are displayed to volunteers via a web-based classification interface, which records their estimates of the positions of candidate lensed features. Images of simulated lenses, as well as real images which lack lenses, are inserted into the image stream at random intervals; this training set is used to give the volunteers instantaneous feedback on their performance, as well as to calibrate a model of the system that provides dynamical updates to the probability that a classified image contains a lens. Low-probability systems are retired from the site periodically, concentrating the sample towards a set of lens candidates. Having divided 160 deg2 of Canada-France-Hawaii Telescope Legacy Survey imaging into some 430 000 overlapping 82 by 82 arcsec tiles and displaying them on the site, we were joined by around 37 000 volunteers who contributed 11 million image classifications over the course of eight months. This stage 1 search reduced the sample to 3381 images containing candidates; these were then refined in stage 2 to yield a sample that we expect to be over 90 per cent complete and 30 per cent pure, based on our analysis of the volunteers performance on training images. We comment on the scalability of the SPACE WARPS system to the wide field survey era, based on our projection that searches of 105 images could be performed by a crowd of 105 volunteers in 6 d.
LHC signals for warped electroweak charged gauge bosons
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Gopalakrishna, Shrihari; Han, Tao; Huang, Gui-Yu; Soni, Amarjit
2009-10-01
We study signals at the LHC for the Kaluza-Klein (KK) excitations of electroweak charged gauge bosons in the framework of the standard model (SM) fields propagating in the bulk of a warped extra dimension. Such a scenario can solve both the Planck-weak and flavor hierarchy problems of the SM. There are two such charged states in this scenario with couplings to light quarks and leptons being suppressed relative to those in the SM, whereas the couplings to top/bottom quarks are enhanced, similar to the case of electroweak neutral gauge bosons previously studied. However, unlike the case of electroweak neutral gauge bosons, there is no irreducible QCD background (including pollution from possibly degenerate KK gluons) for decays to top+bottom final states so that this channel is useful for the discovery of the charged states. Moreover, decays of electroweak charged gauge bosons to longitudinal W, Z and Higgs are enhanced just as for the neutral bosons. However, unlike for the neutral gauge bosons, the purely leptonic (and hence clean) decay mode of the WZ is fully reconstructible so that the ratio of the signal to the SM (electroweak) background can potentially be enhanced by restricting to the resonance region more efficiently. We show that such final states can give sensitivity to 2(3) TeV masses with an integrated luminosity of 100(300)fb-1. We emphasize that improvements in discriminating a QCD jet from a highly boosted hadronically decaying W, and a highly boosted top jet from a bottom jet will enhance the reach for these KK particles, and that the signals we study for the warped extra dimensional model might actually be applicable also to a wider class of nonsupersymmetric models of electroweak symmetry breaking.
Electrocardiographic textbooks based on template hearts warped using ultrasonic images.
Arthur, R Martin; Trobaugh, Jason W
2012-09-01
Advances in technology make the application of sophisticated approaches to assessing electrical condition of the heart practical. Estimates of cardiac electrical features inferred from body-surface electrocardiographic (ECG) maps are now routinely found in a clinical setting, but errors in those inverse solutions are especially sensitive to the accuracy of heart model geometry and placement within the torso. The use of a template heart model allows for accurate generation of individualized heart models and also permits effective comparison of inferred electrical features among multiple subjects. A collection of features mapped onto a common template forms a textbook of anatomically specific ECG variability. Our template warping process to individualize heart models based on a template heart uses ultrasonic images of the heart from a conventional, phased-array system. We chose ultrasound because it is nonionizing, less expensive, and more convenient than MR or CT imaging. To find the orientation and position in the torso model of each image, we calibrated the ultrasound probe by imaging a custom phantom consisting of multiple N-fiducials and computing a transformation between ultrasound coordinates and measurements of the torso surface. The template heart was warped using a mapping of corresponding landmarks identified on both the template and the ultrasonic images. Accuracy of the method is limited by patient movement, tracking error, and image analysis. We tested our approach on one normal control and one obese diabetic patient using the mixed-boundary-value inverse method and compared results from both on the template heart. We believe that our novel textbook approach using anatomically specific heart and torso models will facilitate the identification of electrophysiological biomarkers of cardiac dysfunction. Because the necessary data can be acquired and analyzed within about 30 min, this framework has the potential for becoming a routine clinical procedure
Nonlinear spatial warping for between-subjects pedobarographic image registration.
Pataky, T C; Keijsers, N L W; Goulermas, J Y; Crompton, R H
2009-04-01
Foot size and shape vary between individuals and the foot adopts arbitrary stance phase postures, so traditional pedobarographic analyses regionalize foot pressure images to afford homologous data comparison. An alternative approach that does not require explicit anatomical labelling and that is used widely in other functional imaging domains is to register images such that homologous structures optimally overlap and then to compare images directly at the pixel level. Image registration represents the preprocessing cornerstone of such pixel-level techniques, so its performance warrants independent attention. The purpose of this study was to evaluate the performance of four between-subjects warping registration algorithms including: Principal Axes (PA), four-parameter Optimal Scaling (OS4), eight-parameter Optimal Projective (OP8), and locally affine Nonlinear (NL). Fifteen subjects performed 10 trials of self-paced walking, and their peak pressure images were registered within-subjects using an optimal rigid body transformation. The resulting mean images were then registered between-subjects using all four methods in all 210 (15x14) subject combinations. All registration methods improved alignment, and each method performed qualitatively well for certain image pairs. However, only the NL consistently performed satisfactorily because of disproportionate anatomical variation in toe lengths and rearfoot/forefoot width, for example. Using three independent image (dis)similarity metrics, MANOVA confirmed that the NL method yielded superior registration performance (p<0.001). These data demonstrate that nonlinear spatial warping is necessary for robust between-subject pedobarographic image registration and, by extension, robust homologous data comparison at the pixel level. PMID:19112023
Simulations of the Galactic Centre Stellar Discs In a Warped Disc Origin Scenario
NASA Astrophysics Data System (ADS)
Ulubay-Siddiki, A.; Bartko, H.
2012-07-01
The Galactic Center (GC) hosts a population of young stars some of which seem to form a system of mutually inclined warped discs. While the presence of young stars in the close vicinity of the massive black hole is already problematic, their orbital configuration makes the situation even more puzzling. We present a possible warped disc origin scenario for these stars, which assumes an initially flat accretion disc which develops a warp through Pringle instability, or Bardeen-Petterson Effect. By working out the critical radii and the time scales involved, we argue that disc warping is plausible for GC parameters. We construct time evolution models for such discs considering the discs' self-gravity, and the torques exerted by the surrounding old star cluster. Our simulations suggest that the best agreement for a purely self-gravitating model is obtained for a disc-to-black hole mass ratio of Md/Mbh ~ 0.001.
Asymptotically warped anti-de Sitter spacetimes in topologically massive gravity
NASA Astrophysics Data System (ADS)
Henneaux, Marc; Martínez, Cristián; Troncoso, Ricardo
2011-12-01
Asymptotically warped AdS spacetimes in topologically massive gravity with negative cosmological constant are considered in the case of spacelike stretched warping, where black holes have been shown to exist. We provide a set of asymptotic conditions that accommodate solutions in which the local degree of freedom (the “massive graviton”) is switched on. An exact solution with this property is explicitly exhibited and possesses a slower falloff than the warped AdS black hole. The boundary conditions are invariant under the semidirect product of the Virasoro algebra with a u(1) current algebra. We show that the canonical generators are integrable and finite. When the graviton is not excited, our analysis is compared and contrasted with earlier results obtained through the covariant approach to conserved charges. In particular, we find agreement with the conserved charges of the warped AdS black holes as well as with the central charges in the algebra.
Linear and non-linear theory of a parametric instability of hydrodynamic warps in Keplerian discs
NASA Astrophysics Data System (ADS)
Gammie, Charles F.; Goodman, Jeremy; Ogilvie, Gordon I.
2000-11-01
We consider the stability of warping modes in Keplerian discs. We find them to be parametrically unstable using two lines of attack, one based on three-mode couplings and the other on Floquet theory. We confirm the existence of the instability and investigate its non-linear development in three dimensions, via numerical experiment. The most rapidly growing non-axisymmetric disturbances are the most nearly axisymmetric (low-m) ones. Finally, we offer a simple, somewhat speculative model for the interaction of the parametric instability with the warp. We apply this model to the masing disc in NGC 4258 and show that, provided the warp is not forced too strongly, parametric instability can fix the amplitude of the warp.
X-ray spectropolarimetric signature of a warped disk around a stellar-mass black hole
NASA Astrophysics Data System (ADS)
Cheng, Yifan; Liu, Dan; Nampalliwar, Sourabh; Bambi, Cosimo
2016-06-01
Black holes (BHs) in x-ray binaries are often assumed to be rotating perpendicular to the plane of the accretion disk and parallel to the orbital plane of the binary. While the Bardeen–Petterson effect forces the inner part of the accretion disk to be aligned with the equatorial plane of a spinning BH, the disk may be warped such that the inclination angle of the outer part is different from that of the inner part. In this paper, we identify a possible observational signature of a warped accretion disk in the spectrum of the polarization degree of the continuum. Such a signature would provide direct evidence for the presence of a warped disk and, potentially, even a measure of the warp radius, which, in turn, could be used to infer the viscosity parameter of the disk.
Null geodesics in the Alcubierre warp-drive spacetime: the view from the bridge
NASA Astrophysics Data System (ADS)
Clark, Chad; Hiscock, William A.; Larson, Shane L.
1999-12-01
The null geodesic equations in the Alcubierre warp-drive spacetime are numerically integrated to determine the angular deflection and redshift of photons which propagate through the distortion of the `warp-drive' bubble to reach an observer at the origin of the warp effect. We find that for a starship with an effective warp speed exceeding the speed of light, stars in the forward hemisphere will appear closer to the direction of motion than they would to an observer at rest. This aberration is qualitatively similar to that caused by special relativity. Behind the starship, a conical region forms from within which no signal can reach the starship, an effective `horizon'. Conversely, there is also a horizon-like structure in a conical region in front of the starship, into which the starship cannot send a signal. These causal structures are somewhat analogous to the Mach cones associated with supersonic fluid flow.
Stone, Wesley W.; Gilliom, Robert J.
2009-01-01
Regression models for predicting atrazine concentrations in streams were updated by incorporating refined annual atrazine-use estimates and by adding an explanatory variable representing annual precipitation characteristics. The updated Watershed Regressions for Pesticides (WARP) models enable improved predictions of specific pesticide-concentration statistics for unmonitored streams. for unmonitored streams. Separate WARP regression models were derived for selected percentiles (5th, 10th, 15th, 25th, 50th, 75th, 85th, 90th and 95th), annual mean, annual maximum, and annual maximum moving-average (21-, 60-, and 90-day durations) concentration statistics. Development of the regression models involved the same model-development data, model-validation data, and regression methods as those used in the original development of WARP. The original WARP models were based on atrazine-use estimates from either 1992 or 1997. This update of the WARP models incorporates annual atrazine-use estimates. In addition, annual precipitation data were evaluated as potential explanatory variables. as potential explanatory variables. The updated WARP models include the same five explanatory variables and transformations that were used in the original WARP models, including the new annual atrazine-use data. The models also include a sixth explanatory variable, total precipitation during May and June of the year of sampling. The updated WARP models account for as much as 82 percent of the variability in the concentration statistics among the 112 sites used for model development, whereas previous WARP models accounted for no more than 77 percent. Concentration statistics predicted by the 95th percentile, annual mean, annual maximum and annual maximum moving-average concentration models were within a factor of 10 of the observed concentration statistics for most of the model development and validation sites. Overall, performance of the models for the development and validation sites supports
Lecture Notes on Multigrid Methods
Vassilevski, P S
2010-06-28
The Lecture Notes are primarily based on a sequence of lectures given by the author while been a Fulbright scholar at 'St. Kliment Ohridski' University of Sofia, Sofia, Bulgaria during the winter semester of 2009-2010 academic year. The notes are somewhat expanded version of the actual one semester class he taught there. The material covered is slightly modified and adapted version of similar topics covered in the author's monograph 'Multilevel Block-Factorization Preconditioners' published in 2008 by Springer. The author tried to keep the notes as self-contained as possible. That is why the lecture notes begin with some basic introductory matrix-vector linear algebra, numerical PDEs (finite element) facts emphasizing the relations between functions in finite dimensional spaces and their coefficient vectors and respective norms. Then, some additional facts on the implementation of finite elements based on relation tables using the popular compressed sparse row (CSR) format are given. Also, typical condition number estimates of stiffness and mass matrices, the global matrix assembly from local element matrices are given as well. Finally, some basic introductory facts about stationary iterative methods, such as Gauss-Seidel and its symmetrized version are presented. The introductory material ends up with the smoothing property of the classical iterative methods and the main definition of two-grid iterative methods. From here on, the second part of the notes begins which deals with the various aspects of the principal TG and the numerous versions of the MG cycles. At the end, in part III, we briefly introduce algebraic versions of MG referred to as AMG, focusing on classes of AMG specialized for finite element matrices.
Improving Lecture Quality through Training in Public Speaking
ERIC Educational Resources Information Center
Mowbray, Robert; Perry, Laura B.
2015-01-01
Lecturing is a common instructional format but poor lecturing skills can detract from students' learning experiences and outcomes. As lecturing is essentially a form of public communication, training in public speaking may improve lecture quality. Twelve university lecturers in Malaysia participated in a six-week public speaking skills…
The Nobel Prize Economics Lectures as a Teaching Tool.
ERIC Educational Resources Information Center
Zahka, William J.
1990-01-01
Proposes using some of the 26 Nobel Prize lectures as teaching tools in economics courses. Notes lectures are reprinted in economic journals. Lists titles of lectures from 1969 to 1988; identifies level of difficulty; and categorizes the lectures by subject field. Outlines George Stigler's 1982 Nobel lecture and gives suggestions for teaching. (NL)
Henry Norris Russell's Toronto Lectures
NASA Astrophysics Data System (ADS)
Devorkin, D. H.
1996-12-01
In February 1924, at the invitation of C. A. Chant, Russell presented a set of 14 public lectures on the state of astronomy and astrophysics. Designed to be inspirational, they also reveal Russell's contemporary views on the state of astrophysics as well as his sense of proper practice in astronomy. During his visit, Russell was interviewed by local reporters who asked his opinion about building a large observatory, one of Chant's major projects. What Russell had to say about such ventures did not please Chant one bit.
NASA Technical Reports Server (NTRS)
Jefferson, David; Beckman, Brian
1986-01-01
This paper describes the concept of virtual time and its implementation in the Time Warp Operating System at the Jet Propulsion Laboratory. Virtual time is a distributed synchronization paradigm that is appropriate for distributed simulation, database concurrency control, real time systems, and coordination of replicated processes. The Time Warp Operating System is targeted toward the distributed simulation application and runs on a 32-node JPL Mark II Hypercube.
Issues in Lecturing in a Second Language: Lecturer's Behaviour and Students' Perceptions
ERIC Educational Resources Information Center
Miller, Lindsay
2007-01-01
This article explores how Hong Kong Chinese engineering students with low English language proficiency manage to cope with their lectures given in English. An ethnographic case study approach was used with multiple sources of data triangulated to provide a picture of the lecture event from both the students' and the lecturer's perspectives. One of…
ERIC Educational Resources Information Center
Williams, W. Larry; Weil, Timothy M.; Porter, James C. K.
2012-01-01
Guided notes were employed in two undergraduate Psychology courses involving 71 students. The study design utilized an alternating treatments format to compare Traditional Lectures with Guided Notes lectures. In one of the two courses, tests were administered after each class lecture, whereas the same type of test was administered at the beginning…
Why do students miss lectures? A study of lecture attendance amongst students of health science.
Bati, A Hilal; Mandiracioglu, Aliye; Orgun, Fatma; Govsa, Figen
2013-06-01
In the domain of health sciences, attendance by students at lectures is more critical. Lecture attendance is an issue which has been widely neglected. This study aims to determine those factors which affect the lecture attendance. The research data was collected by means of a questionnaire during the second semester of the academic year 2010-2011 from second-year students of the Faculties of Medicine, Pharmacy, Dentistry and Nursing. Together with demographic data, the questionnaire includes a Likert-type scale aiming to determine the factors influencing attendance at lectures. 663 participated in this study on a voluntary basis from Medical, Dentistry, Pharmacy and Nursing Faculties. Raising attainment levels, being able to take their own lecture notes, learning which aspects of the lecture content were being emphasized, and the opportunity to ask questions were amongst the chief reasons for attending lectures. It appears that the factors preventing students from attending lectures are mainly individual. Amongst the most frequently cited causes of non-attendance, sleeplessness, ill health and the inefficiency of lectures in overcrowded halls are emphasized. In the totals and sub-dimensions of the Lecture Attendance Scale, Medical Faculty students have average scores higher than those of students at other faculties. The vital nature of professional expertise and its applications, health sciences students' attendance at lectures carries greater importance. It is important to strengthen the mentoring system with regard to individual and external factors, which have been implicated as having a substantial influence on lecture attendance by students. PMID:22863210
Lecture Is Not a Dirty Word: How to Use Active Lecture to Increase Student Engagement
ERIC Educational Resources Information Center
Gregory, Jess L.
2013-01-01
Lecture is a much maligned classroom method of instruction. Like any other technique employed by educators, there are both effective and ineffective ways to deliver content through a lecture format. Respecting that the college learner has changed, active lecturing strategies maximize student learning of course content, engaging both modern…
Theoretical analysis of warping operators for non-ideal shallow water waveguides.
Niu, Haiqiang; Zhang, Renhe; Li, Zhenglin
2014-07-01
Signals propagating in waveguides can be decomposed into normal modes that exhibit dispersive characteristics. Based on the dispersion analysis, the warping transformation can be used to improve the modal separability. Different from the warping transformation defined using an ideal waveguide model, an improved warping operator is presented in this paper based on the beam-displacement ray-mode (BDRM) theory, which can be adapted to low-frequency signals in a general shallow water waveguide. For the sake of obtaining the warping operators for the general waveguides, the dispersion formula is first derived. The approximate dispersion relation can be achieved with adequate degree of accuracy for the waveguides with depth-dependent sound speed profiles (SSPs) and acoustic bottoms. Performance and accuracy of the derived formulas for the dispersion curves are evaluated by comparing with the numerical results. The derived warping operators are applied to simulations, which show that the non-linear dispersion structures can be well compensated by the proposed warping operators. PMID:24993195
On the characterization of the Galactic warp in the Gaia era
NASA Astrophysics Data System (ADS)
Abedi, H.; Figueras, F.; Aguilar, L.; Mateu, C.; Romero-Gomez, M.; Lopez-Corredoira, M.; Garzon Lopez, F.
2014-07-01
We explore the possibility of detecting and characterising the warp of the stellar disc of our Galaxy using the synthetic Gaia data and the UCAC4 proper motion catalogue. We develop a new kinematic model for the galactic warp. We generate random realisations of test particles which evolve in a realistic Galactic potential warped adiabatically to various final configurations. The Gaia selection function, its errors model and a realistic 3D extinction map are applied to mimic three tracer populations: OB, A and Red Clump stars. A family of Great Circle Cell Counts (GC3) methods is used. They are ideally suited to find the tilt and twist of a collection of rings, which allow us to detect and measure the warp parameters. Moreover, We look for the kinematic signature of the warp in the μb proper motions of stars as a function of galactic longitude. Using the UCAC4 proper motions, we do not obtain a similar trend as the one we expect from our warp model. We explore a possible source of this discrepancy in terms of systematics caused by a residual spin of the Hipparcos celestial reference frame (HCRF) with respect to the extra-galactic inertial one.
Lectures on Geophysical Fluid Dynamics
NASA Astrophysics Data System (ADS)
Samelson, Roger M.
The fluid kaleidoscope of the Earth's ocean and atmosphere churns and sparkles with jets, gyres, eddies, waves, streams, and cyclones. These vast circulations, essential elements of the physical environment that support human life, are given a special character by the Earth's rotation and by their confinement to a shallow surficial layer, thin relative to the solid Earth in roughly the same proportion as an apple skin is to an apple. Geophysical fluid dynamics exploits this special character to develop a unified theoretical approach to the physics of the ocean and atmosphere.With Lectures on Geophysical Fluid Dynamics, Rick Salmon has added an insightful and provocative volume to the handful of authoritative texts currently available on the subject. The book is intended for first-year graduate students, but advanced students and researchers also will find it useful. It is divided into seven chapters, the first four of these adapted from course lectures. The book is well written and presents a fresh and stimulating perspective that complements existing texts. It would serve equally well either as the main text for a core graduate curriculum or as a supplementary resource for students and teachers seeking new approaches to both classical and contemporary problems. A lively set of footnotes contains many references to very recent work. The printing is attractive, the binding is of high quality, and typographical errors are few.
The Warped Plane of the Classical Kuiper Belt
NASA Astrophysics Data System (ADS)
Chiang, Eugene; Choi, Hyomin
2008-07-01
By numerically integrating the orbits of the giant planets and of test particles over a period of four billion years, we follow the evolution of the location of the midplane of the Kuiper belt. The Classical Kuiper belt conforms to a warped sheet that precesses with a 1.9 Myr period. The present-day location of the Kuiper belt plane can be computed using linear secular perturbation theory: the local normal to the plane is given by the theory's forced inclination vector, which is specific to every semimajor axis. The Kuiper belt plane does not coincide with the invariable plane, but deviates from it by up to a few degrees in stable zones. For example, at a semimajor axis of 38 AU, the local Kuiper belt plane has an inclination of 1.9 degrees and a longitude of ascending node of 149.9 degrees when referred to the mean ecliptic and equinox of J2000. At a semimajor axis of 43 AU, the local plane has an inclination of 1.9 degrees and a nodal longitude of 78.3 degrees. Only at infinite semimajor axis does the Kuiper belt plane merge with the invariable plane, whose inclination is 1.6 degrees and nodal longitude is 107.7 degrees. A Classical Kuiper belt object keeps its inclination relative to the Kuiper belt plane nearly constant, even while the plane departs from the trajectory predicted by linear theory. The constancy of relative inclination reflects the undamped amplitude of free oscillation; that is, the homogeneous solution to the forced harmonic oscillator equation retains constant amplitude, even while the inhomogeneous solution cannot be written down accurately because the planetary forcing terms are chaotic. Current observations of Classical Kuiper belt objects are consistent with the plane being warped by the giant planets alone, but the sample size will need to increase by a few times before confirmation exceeds 3σ in confidence. In principle, differences between the theoretically expected plane and the observed plane could be used to infer as yet unseen
HUBBLE PHOTOGRAPHS WARPED GALAXY AS CAMERA PASSES MILESTONE
NASA Technical Reports Server (NTRS)
2002-01-01
NASA's Hubble Space Telescope has captured an image of an unusual edge-on galaxy, revealing remarkable details of its warped dusty disk and showing how colliding galaxies spawn the formation of new generations of stars. The dust and spiral arms of normal spiral galaxies, like our own Milky Way, appear flat when viewed edge-on. This month's Hubble Heritage image of ESO 510-G13 shows a galaxy that, by contrast, has an unusual twisted disk structure, first seen in ground-based photographs obtained at the European Southern Observatory (ESO) in Chile. ESO 510-G13 lies in the southern constellation Hydra, roughly 150 million light-years from Earth. Details of the structure of ESO 510-G13 are visible because the interstellar dust clouds that trace its disk are silhouetted from behind by light from the galaxy's bright, smooth central bulge. The strong warping of the disk indicates that ESO 510-G13 has recently undergone a collision with a nearby galaxy and is in the process of swallowing it. Gravitational forces distort the structures of the galaxies as their stars, gas, and dust merge together in a process that takes millions of years. Eventually the disturbances will die out, and ESO 510-G13 will become a normal-appearing single galaxy. In the outer regions of ESO 510-G13, especially on the right-hand side of the image, we see that the twisted disk contains not only dark dust, but also bright clouds of blue stars. This shows that hot, young stars are being formed in the disk. Astronomers believe that the formation of new stars may be triggered by collisions between galaxies, as their interstellar clouds smash together and are compressed. The Heritage Team used Hubble's Wide Field Planetary Camera 2 (WFPC2) to observe ESO 510-G13 in April 2001. Pictures obtained through blue, green, and red filters were combined to make this color-composite image, which emphasizes the contrast between the dusty spiral arms, the bright bulge, and the blue star-forming regions. During the
Cosmology at the Beach Lecture: Wayne Hu
Wayne Hu
2010-01-08
Wayne Hu lectures on Secondary Anisotropy in the CMB. The lecture is the first in a series of 3 he delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.
Large Lecture Format: Some Lessons Learned.
ERIC Educational Resources Information Center
Kryder, LeeAnne G.
2002-01-01
Shares some surprising results from a business communication program's recent experiment in using a large lecture format to teach an upper-division business communication course: approximately 90-95% of the students liked the large lecture format, and the quality of their communication deliverables was as good as that produced by students who took…
Team Teaching: An Alternative to Lecture Fatigue.
ERIC Educational Resources Information Center
Quinn, Sandra L.; Kanter, Sanford B.
1984-01-01
More than an interdisciplinary format employing lecturers from different disciplines, team teaching is an approach which involves true team work between two qualified instructors who, together, make presentations to an audience. The instructional advantages of team teaching include: (1) the elimination of lecture-style instruction in favor of a…
The Humanity of English. 1972 Distinguished Lectures.
ERIC Educational Resources Information Center
National Council of Teachers of English, Urbana, IL.
This is a collection of lectures by distinguished members of the English profession who were invited to lecture to schools located far from large urban and cultural centers. Included are papers by: John H. Fisher, "Truth Versus Beauty: An Inquiry into the Function of Language and Literature in an Articulate Society"; Walter Loban, "The Green…
Parker Lecturers Gather at Joint Assembly
NASA Astrophysics Data System (ADS)
Crooker, Nancy
2008-08-01
Present and past Parker Lecturers, who are Bowie Lecturers of AGU's Space Physics and Aeronomy (SPA) section, gathered at the Joint Assembly in Fort Lauderdale, Fla., on the occasion of the fiftieth anniversary of the publication of Eugene Parker's famous paper predicting the existence of the supersonic solar wind (see Figure 1).
Man and His Environment. Octagon Lectures 1969.
ERIC Educational Resources Information Center
Appleyard, R. T., Ed.
Utilizing the theme "Man and His Environment," the Octagon Lectures of 1969 were presented at the University of Western Australia, Nedlands, Western Australia. Problems arising from the imbalance between the ancient forces of nature and the new forces of human culture were dealt with by the lecturers. They revealed that the most important…
The Art of the Lecture Revisited.
ERIC Educational Resources Information Center
Journal of Chemical Education, 1983
1983-01-01
Lecturing hints, periodic table, mechanistic approach to predicting inorganic reaction products for substitution reactions, reaction rates, spectroscopy, and entropy role change in establishing position of equilibrium for vaporization of water and synthesis of ammonia were topics of lectures presented at the Seventh Biennial Conference on Chemical…
Cosmology at the Beach Lecture: Wayne Hu
Wayne Hu
2009-03-02
Wayne Hu lectures on Secondary Anisotropy in the CMB. The lecture is the first in a series of 3 he delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.
THE OVERHEAD PROJECTOR IN THE PHYSICS LECTURE.
ERIC Educational Resources Information Center
EPPENSTEIN, WALTER
SOME SUCCESSFUL APPLICATIONS OF OVERHEAD PROJECTORS IN THE PHYSICS LECTURE HALL AT RENSSELAER POLYTECHNIC INSTITUTE ARE DESCRIBED--(1) PRODUCTION AND USE OF TRANSPARENCIES, (2) THE OVERHEAD PROJECTOR IN THE DEMONSTRATION LECTURE, (3) BREAD-BOARD FOR ELECTRICAL CONNECTIONS, AND (4) AN X-Y PLOTTER FOR THE OVERHEAD PROJECTOR. (MS)
Digital lecture recording: a cautionary tale.
Johnston, Amy N B; Massa, Helen; Burne, Thomas H J
2013-01-01
Increasing application of information technology including web-based lectures and live-lecture recording appears to have many advantages for undergraduate nursing education. These include greater flexibility, opportunity for students to review content on demand and the improved academic management of increasing class sizes without significant increase in physical infrastructure. This study performed a quasi-experimental comparison between two groups of nursing students undertaking their first anatomy and physiology course, where one group was also provided access to streaming of recorded copies of the live lectures and the other did not. For the course in which recorded lectures were available student feedback indicated overwhelming support for such provision with 96% of students having accessed recorded lectures. There was only a weak relationship between access of recorded lectures and overall performance in the course. Interestingly, the nursing students who had access to the recorded lectures demonstrated significantly poorer overall academic performance (P < 0.001). Although this study did not specifically control for student demographics or other academic input, the data suggests that provision of recorded lectures requires improved and applied time management practices by students and caution on the part of the academic staff involved. PMID:22889680
NASA Astrophysics Data System (ADS)
Dudley, J. M.; Kwan, A. M.
1996-06-01
The subject of quantum electrodynamics (QED) was the subject of QED—The Strange Theory of Light and Matter, the popular book by Richard Feynman which was published by Princeton University Press in 1985. On p. 1, Feynman makes passing reference to the fact that the book is based on a series of general lectures on QED which were, however, first delivered in New Zealand. At Auckland University, these lectures were delivered in 1979, as the Sir Douglas Robb lectures, and videotapes of the lectures are held by the Auckland University Physics Department. We have carried out a detailed examination of these videotapes, and we discuss here the major differences between the original Auckland lectures and the published version. We use selected quotations from the lectures to show that the original lectures provide additional insight into Feynman's character, and have great educational value.
Higgs phenomenology in warped extra dimensions with a fourth generation
Frank, Mariana; Korutlu, Beste; Toharia, Manuel
2011-10-01
We study a warped extra-dimension scenario where the standard model fields lie in the bulk, with the addition of a fourth family of fermions. We concentrate on the flavor structure of the Higgs couplings with fermions in the flavor anarchy ansatz. Even without a fourth family, these couplings will be generically misaligned with respect to the standard model fermion mass matrices. The presence of the fourth family typically enhances the misalignment effects and we show that one should expect them to be highly nonsymmetrical in the (34) intergenerational mixing. The radiative corrections from the new fermions and their flavor-violating couplings to the Higgs affect negligibly known experimental precision measurements such as the oblique parameters and Z{yields}bb or Z{yields}{mu}{sup +}{mu}{sup -}. On the other hand, {Delta}F=1, 2 processes, mediated by tree-level Higgs exchange, as well as radiative corrections to b{yields}s{gamma} and {mu}{yields}e{gamma} put some generic pressure on the allowed size of the flavor-violating couplings. But more importantly, these couplings will alter the Higgs decay patterns as well as those of the new fermions, and produce very interesting new signals associated to Higgs phenomenology in high energy colliders. These signals might become very important indirect signals for these type of models as they would be present even when the KK mass scale is high and no heavy KK particle is discovered.
Higgs phenomenology in warped extra dimensions with a fourth generation
NASA Astrophysics Data System (ADS)
Frank, Mariana; Korutlu, Beste; Toharia, Manuel
2011-10-01
We study a warped extra-dimension scenario where the standard model fields lie in the bulk, with the addition of a fourth family of fermions. We concentrate on the flavor structure of the Higgs couplings with fermions in the flavor anarchy ansatz. Even without a fourth family, these couplings will be generically misaligned with respect to the standard model fermion mass matrices. The presence of the fourth family typically enhances the misalignment effects and we show that one should expect them to be highly nonsymmetrical in the (34) intergenerational mixing. The radiative corrections from the new fermions and their flavor-violating couplings to the Higgs affect negligibly known experimental precision measurements such as the oblique parameters and Z→bb¯ or Z→μ+μ-. On the other hand, ΔF=1, 2 processes, mediated by tree-level Higgs exchange, as well as radiative corrections to b→sγ and μ→eγ put some generic pressure on the allowed size of the flavor-violating couplings. But more importantly, these couplings will alter the Higgs decay patterns as well as those of the new fermions, and produce very interesting new signals associated to Higgs phenomenology in high energy colliders. These signals might become very important indirect signals for these type of models as they would be present even when the KK mass scale is high and no heavy KK particle is discovered.
Axion monodromy inflation with warped KK-modes
NASA Astrophysics Data System (ADS)
Hebecker, Arthur; Moritz, Jakob; Westphal, Alexander; Witkowski, Lukas T.
2016-03-01
We present a particularly simple model of axion monodromy inflation: Our axion is the lowest-lying KK-mode of the RR-2-form-potential C2 in the standard Klebanov-Strassler throat. One can think of this inflaton candidate as being defined by the integral of C2 over the S2 cycle of the throat. It obtains an exponentially small mass from the IR-region in which the S2 shrinks to zero size. Crucially, the S2 cycle has to be shared between two throats, such that the second locus where the S2 shrinks is also in a warped region. Well-known problems like the potentially dangerous back-reaction of brane/antibrane pairs and explicit supersymmetry breaking are not present in our scenario. The inflaton back-reaction on the geometry turns out to be controlled by the string coupling gs. We hope that our setting is simple enough for many critical consistency issues of large-field inflation in string theory to be addressed at a quantitative level.
Generalized Gravitational Entropy for Warped Anti-de Sitter Space
NASA Astrophysics Data System (ADS)
Song, Wei; Wen, Qiang; Xu, Jianfei
2016-07-01
For spacetimes that are not asymptotic to anti-de Sitter (non AAdS) space, we adapt the Lewkowycz-Maldacena procedure to find the holographic entanglement entropy. The key observation, which to our knowledge is not very well appreciated, is that asymptotic boundary conditions play an essential role on extending the replica trick to the bulk. For non AAdS, we expect the following three main modifications: (1) the expansion near the special surface has to be compatible with the asymptotic expansion; (2) periodic conditions are imposed to coordinates on the phase space with diagonalized symplectic structure, not to all fields appearing in the action; (3) evaluating the entanglement functional using the boundary term method amounts to evaluating the presymplectic structure at the special surface, where some additional exact form may contribute. An explicit calculation is carried out for three-dimensional warped anti-de Sitter spacetime (WAdS3 ) in a consistent truncation of string theory, the so-called S -dual dipole theory. It turns out that the generalized gravitational entropy in WAdS3 is captured by the least action of a charged particle in WAdS3 space, or equivalently, by the geodesic length in an auxiliary AdS3 . Consequently, the bulk calculation agrees with the CFT results, providing another piece of evidence for the WAdS3/CFT2 correspondence.
Warped Supersymmetric Unification with Non-Unified Superparticle Spectrum
Nomura, Yasunori; Tucker-Smith, David; Tweedie, Brock
2004-03-16
We present a new supersymmetric extension of the standard model. The model is constructed in warped space, with a unified bulk symmetry broken by boundary conditions on both the Planck and TeV branes. In the supersymmetric limit, the massless spectrum contains exotic colored particles along with the particle content of the minimal supersymmetric standard model (MSSM). Nevertheless, the model still reproduces the MSSM prediction for gauge coupling unification and does not suffer from a proton decay problem. The exotic states acquire masses from supersymmetry breaking, making the model completely viable, but thereis still the possibility that these states will be detected at the LHC. The lightest of these states is most likely A_5^XY, the fifth component of the gauge field associated with the broken unified symmetry. Because supersymmetry is broken on the SU(5)-violating TeV brane, the gaugino masses generated at the TeV scale are completely independent of one another. We explore some of the unusual features that the superparticle spectrum might have as a consequence.
Warped gravitons at the CERN LHC and beyond
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Davoudiasl, Hooman; Perez, Gilad; Soni, Amarjit
2007-08-01
We study the production and decay of Kaluza-Klein (KK) gravitons at the CERN Large Hadron Collider (LHC), in the framework of a warped extra dimension in which the standard model (SM) fields propagate. Such a scenario can provide solutions to both the Planck-weak hierarchy problem and the flavor puzzle of the SM. In this scenario, the production via qq¯ annihilation and decays to the conventional photon and lepton channels are highly suppressed. However, we show that graviton production via gluon fusion followed by decay to longitudinal Z/W can be significant; vector boson fusion is found to be a subdominant production mode. In particular, the golden ZZ decay mode offers a distinctive 4-lepton signal that could lead to the observation at the LHC with 300fb-1 (SLHC with 3ab-1) of a KK graviton with a mass up to ˜2 (˜3) TeV for the ratio of the AdS5 curvature to the Planck scale modestly above unity. We argue that (contrary to the lore) such a size of the curvature scale can still be within the regime of validity of the framework. Upgrades beyond the SLHC luminosity are required to discover gravitons heavier than ˜4TeV, as favored by the electroweak and flavor precision tests in the simplest such models.
Time-warp invariant pattern detection with bursting neurons
NASA Astrophysics Data System (ADS)
Gollisch, Tim
2008-01-01
Sound patterns are defined by the temporal relations of their constituents, individual acoustic cues. Auditory systems need to extract these temporal relations to detect or classify sounds. In various cases, ranging from human speech to communication signals of grasshoppers, this pattern detection has been found to display invariance to temporal stretching or compression of the sound signal ('linear time-warp invariance'). In this work, a four-neuron network model is introduced, designed to solve such a detection task for the example of grasshopper courtship songs. As an essential ingredient, the network contains neurons with intrinsic bursting dynamics, which allow them to encode durations between acoustic events in short, rapid sequences of spikes. As shown by analytical calculations and computer simulations, these neuronal dynamics result in a powerful mechanism for temporal integration. Finally, the network reads out the encoded temporal information by detecting equal activity of two such bursting neurons. This leads to the recognition of rhythmic patterns independent of temporal stretching or compression.
Overview of WARP: A particle code for heavy ion fusion
NASA Astrophysics Data System (ADS)
Friedman, Alex; Grote, David P.; Callahan, Debra A.; Langdon, A. Bruce; Haber, Irving
1993-02-01
The beams in a heavy ion beam driven inertial fusion (HIF) accelerator must be focused onto small spots at the fusion target, and so preservation of beam quality is crucial. The nonlinear self-fields of these space-charge-dominated beams can lead to emittance growth; thus, a self-consistent field description is necessary. We have developed a multi-dimensional discrete-particle simulation code, WARP, and are using it to study the behavior of HIF beams. The code's 3D package combines features of an accelerator code and a particle-in-cell plasma simulation, and can efficiently track beams through many lattice elements and around bends. We have used the code to understand the physics of aggressive drift-compression in the MBE-4 experiment at Lawrence Berkeley Laboratory (LBL). We have applied it to LBL's planned ILSE experiments, to various 'recirculator' configurations, and to the study of equilibria and equilibration processes. Applications of the 3D package to ESQ injectors, and of the r, z package to longitudinal stability in driver beams, are discussed in related papers.
Overview of WARP, a particle code for heavy ion fusion
NASA Astrophysics Data System (ADS)
Friedman, Alex; Grote, David P.; Callahan, Debra A.; Langdon, A. Bruce; Haber, Irving
1993-12-01
The beams in a Heavy Ion beam driven inertial Fusion (HIF) accelerator must be focused onto small spots at the fusion target, and so preservation of beam quality is crucial. The nonlinear self-fields of these space-charge-dominated beams can lead to emittance growth; thus a self-consistent field description is necessary. We have developed a multi-dimensional discrete-particle simulation code, WARP, and are using it to study the behavior of HIF beams. The code's 3d package combines features of an accelerator code and a particle-in-cell plasma simulation, and can efficiently track beams through many lattice elements and around bends. We have used the code to understand the physics of aggressive drift-compression in the MBE-4 experiment at Lawrence Berkeley Laboratory (LBL). We have applied it to LBL's planned ILSE experiments, to various ``recirculator'' configurations, and to the study of equilibria and equilibration processes. Applications of the 3d package to ESQ injectors, and of the r, z package to longitudinal stability in driver beams, are discussed in related papers.
Overview of WARP, a particle code for Heavy Ion Fusion
Friedman, A.; Grote, D.P.; Callahan, D.A.; Langdon, A.B.; Haber, I.
1993-02-22
The beams in a Heavy Ion beam driven inertial Fusion (HIF) accelerator must be focused onto small spots at the fusion target, and so preservation of beam quality is crucial. The nonlinear self-fields of these space-charge-dominated beams can lead to emittance growth; thus a self-consistent field description is necessary. We have developed a multi-dimensional discrete-particle simulation code, WARP, and are using it to study the behavior of HIF beams. The code`s 3d package combines features of an accelerator code and a particle-in-cell plasma simulation, and can efficiently track beams through many lattice elements and around bends. We have used the code to understand the physics of aggressive drift-compression in the MBE-4 experiment at Lawrence Berkeley Laboratory (LBL). We have applied it to LBL`s planned ILSE experiments, to various ``recirculator`` configurations, and to the study of equilibria and equilibration processes. Applications of the 3d package to ESQ injectors, and of the r, z package to longitudinal stability in driver beams, are discussed in related papers.
Warped gravitons at the CERN LHC and beyond
Agashe, Kaustubh; Davoudiasl, Hooman; Soni, Amarjit; Perez, Gilad
2007-08-01
We study the production and decay of Kaluza-Klein (KK) gravitons at the CERN Large Hadron Collider (LHC), in the framework of a warped extra dimension in which the standard model (SM) fields propagate. Such a scenario can provide solutions to both the Planck-weak hierarchy problem and the flavor puzzle of the SM. In this scenario, the production via qq annihilation and decays to the conventional photon and lepton channels are highly suppressed. However, we show that graviton production via gluon fusion followed by decay to longitudinal Z/W can be significant; vector boson fusion is found to be a subdominant production mode. In particular, the golden ZZ decay mode offers a distinctive 4-lepton signal that could lead to the observation at the LHC with 300 fb{sup -1} (SLHC with 3 ab{sup -1}) of a KK graviton with a mass up to {approx}2 ({approx}3) TeV for the ratio of the AdS{sub 5} curvature to the Planck scale modestly above unity. We argue that (contrary to the lore) such a size of the curvature scale can still be within the regime of validity of the framework. Upgrades beyond the SLHC luminosity are required to discover gravitons heavier than {approx}4 TeV, as favored by the electroweak and flavor precision tests in the simplest such models.
Generalized Gravitational Entropy for Warped Anti-de Sitter Space.
Song, Wei; Wen, Qiang; Xu, Jianfei
2016-07-01
For spacetimes that are not asymptotic to anti-de Sitter (non AAdS) space, we adapt the Lewkowycz-Maldacena procedure to find the holographic entanglement entropy. The key observation, which to our knowledge is not very well appreciated, is that asymptotic boundary conditions play an essential role on extending the replica trick to the bulk. For non AAdS, we expect the following three main modifications: (1) the expansion near the special surface has to be compatible with the asymptotic expansion; (2) periodic conditions are imposed to coordinates on the phase space with diagonalized symplectic structure, not to all fields appearing in the action; (3) evaluating the entanglement functional using the boundary term method amounts to evaluating the presymplectic structure at the special surface, where some additional exact form may contribute. An explicit calculation is carried out for three-dimensional warped anti-de Sitter spacetime (WAdS_{3}) in a consistent truncation of string theory, the so-called S-dual dipole theory. It turns out that the generalized gravitational entropy in WAdS_{3} is captured by the least action of a charged particle in WAdS_{3} space, or equivalently, by the geodesic length in an auxiliary AdS_{3}. Consequently, the bulk calculation agrees with the CFT results, providing another piece of evidence for the WAdS_{3}/CFT_{2} correspondence. PMID:27419559
Ultravisible warped model from flavor triviality and improved naturalness
Delaunay, Cedric; Gedalia, Oram; Lee, Seung J.; Perez, Gilad; Ponton, Eduardo
2011-06-01
A warped extra-dimensional model, where the standard model Yukawa hierarchy is set by UV physics, is shown to have a sweet spot of parameters with improved experimental visibility and possibly naturalness. Upon marginalizing over all the model parameters, a Kaluza-Klein scale of 2.1 TeV can be obtained at 2{sigma} (95.4% C.L.) without conflicting with electroweak precision measurements. Fitting all relevant parameters simultaneously can relax this bound to 1.7 TeV. In this bulk version of the Rattazzi-Zaffaroni shining model, flavor violation is also highly suppressed, yielding a bound of 2.4 TeV. Nontrivial flavor physics at the LHC in the form of flavor gauge bosons is predicted. The model is also characterized by a depletion of the third-generation couplings--as predicted by the general minimal flavor violation framework--which can be tested via flavor precision measurements. In particular, sizable CP violation in {Delta}B=2 transitions can be obtained, and there is a natural region where B{sub s} mixing is predicted to be larger than B{sub d} mixing, as favored by recent Tevatron data. Unlike other proposals, the new contributions are not linked to Higgs or any scalar exchange processes.
Weaving and bonding method to prevent warp and fill distortion
NASA Technical Reports Server (NTRS)
Farley, Gary L. (Inventor)
1997-01-01
A method to prevent fiber distortion in textile materials employed in a modified weaving process. In a first embodiment, a tacifier in powder form is applied to the yarn and melted while on the fabric. Cool air is then supplied after the tacifier has melted to expedite the solidification of the tacifier. In a second embodiment, a solution form of a tacifier is used by dissolving the tacifier into a solvent that has a high evaporation rate. The solution is then sprayed onto the fabric or fill yarn as each fill yarn is inserted into a shed of the fabric. A third embodiment applies the tacifier in a liquid form that has not been dissolved in a solvent. That is, the tacifier is melted and is sprayed as a liquid onto the fabric or fill yarn as it is being extracted from a fill yarn spool prior to the fill yarn being inserted into the shed of the fabric. A fourth embodiment employs adhesive yarns contained as an integral part of the warp or fill yarn. Additional tacifier material is not required because a matrix is used as the tacifier. The matrix is then locally melted using heating elements on clamping bars or take-up rollers, is cooled, if necessary, and solidified.
B-factory signals for a warped extra dimension
Agashe, Kaustubh; Perez, Gilad; Soni, Amarjit
2004-08-24
We study predictions for B-physics in a class of models, recently introduced, with a non-supersymmetric warped extra dimension. In these models few ({approx} 3) TeV Kaluza-Klein masses are consistent with electroweak data due to bulk custodial symmetry. Furthermore, there is an analog of GIM mechanism which is violated by the heavy top quark (just as in SM) leading to striking signals at B-factories: (1) New Physics (NP) contributions to {Delta}F = 2 transitions are comparable to SM. This implies that, within this NP framework, the success of the SM unitarity triangle fit is a ''coincidence''. Thus, clean extractions of unitarity angles via e.g. B {yields} {pi}{pi}, {rho}{pi}, {rho}{rho}, DK are likely to be affected, in addition to O(1) deviation from SM prediction in Bs mixing. (2) O(1) deviation from SM predictions for B {yields} X{sub s}{ell}{sup +}{ell}{sup -} in rate as well as in forward-backward and direct CP asymmetry. (3) Large mixing-induced CP asymmetry in radiative B decays, wherein the SM unambiguously predicts very small asymmetries. Also, with KK masses 3 TeV or less, and with anarchic Yukawa masses, contributions to electric dipole moments of the neutron are roughly 20 times larger than the current experimental bound so that this framework has a ''CP problem''.
Wobbling and Precessing Jets from Warped Disks in Binary Systems
NASA Astrophysics Data System (ADS)
Sheikhnezami, Somayeh; Fendt, Christian
2015-12-01
We present results of the first ever three-dimensional (3D) magnetohydrodynamic (MHD) simulations of the accretion-ejection structure. We investigate the 3D evolution of jets launched symmetrically from single stars but also jets from warped disks in binary systems. We have applied various model setups and tested them by simulating a stable and bipolar symmetric 3D structure from a single star-disk-jet system. Our reference simulation maintains a good axial symmetry and also a bipolar symmetry for more than 500 rotations of the inner disk, confirming the quality of our model setup. We have then implemented a 3D gravitational potential (Roche potential) due by a companion star and run a variety of simulations with different binary separations and mass ratios. These simulations show typical 3D deviations from axial symmetry, such as jet bending outside the Roche lobe or spiral arms forming in the accretion disk. In order to find indications of precession effects, we have also run an exemplary parameter setup, essentially governed by a small binary separation of only ≃200 inner disk radii. This simulation shows a strong indication that we observe the onset of a jet precession caused by the wobbling of the jet-launching disk. We estimate the opening angle of the precession cone defined by the lateral motion of the jet axis to be about 4° after about 5000 dynamical time steps.
Dynamic Time Warping for coda wave interferometry studies
NASA Astrophysics Data System (ADS)
Mikesell, D.; Malcolm, A. E.; Haney, M. M.; Yang, D.
2014-12-01
Accurate time-shift estimation between arrivals in two seismic traces before and after a small velocity change is crucial for estimating the location and amplitude of the velocity change. Windowed crosscorrelation and trace stretching are two time-domain techniques commonly used to estimate local time shifts between multiply scattered coda signals. These methods can both fail when the induced changes in the scattered wavefield are not simple time shifts. Cycle skipping is an example of one such obstacle. A common approach to mitigate such problems is to choose only part of the coda to analyze. In the work presented here, we implement Dynamic Time Warping (DTW) to search for the time shift at each time sample that globally minimizes the misfit between two seismic traces. We show that DTW is considerably less susceptible to errors in time-shift estimates caused by cycle skipping or disappearance of coda phases due to changes in the physical scattering properties. Our approach provides a new tool to estimate small time shifts in coda and has wide application across many disciplines of seismic monitoring and imaging.
Conserved charges in timelike warped AdS3 spaces
NASA Astrophysics Data System (ADS)
Donnay, L.; Fernández-Melgarejo, J. J.; Giribet, G.; Goya, A.; Lavia, E.
2015-06-01
We consider the timelike version of warped anti-de Sitter space (WAdS), which corresponds to the three-dimensional section of the Gödel solution of four-dimensional cosmological Einstein equations. This geometry presents closed timelike curves (CTCs), which are inherited from its four-dimensional embedding. In three dimensions, this type of solution can be supported without matter provided the graviton acquires mass. Here, among the different ways to consistently give mass to the graviton in three dimensions, we consider the parity-even model known as new massive gravity (NMG). In the bulk of timelike WAdS3 space, we introduce defects that, from the three-dimensional point of view, represent spinning massive particlelike objects. For this type of source, we investigate the definition of quasilocal gravitational energy as seen from infinity, far beyond the region where the CTCs appear. We also consider the covariant formalism applied to NMG to compute the mass and the angular momentum of spinning particlelike defects and compare the result with the one obtained by means of the quasilocal stress tensor. We apply these methods to special limits in which the WAdS3 solutions coincide with locally AdS3 and locally AdS2×R spaces. Finally, we make some comments about the asymptotic symmetry algebra of asymptotically WAdS3 spaces in NMG.
A Defect Localization Procedure Based on Warped Lamb Waves
NASA Astrophysics Data System (ADS)
De Marchi, L.; Marzani, A.; Caporale, S.; Speciale, N.
Passive defect location procedures based on ultrasonic guided waves are widely used for structural health monitoring purposes of plate-like structures. Approaches based on the measured time-of-flight delay of propagating waves recorded at different locations are generally adopted. In these approaches, uncertainties are due to the fixed speed assumed for the incoming waves to convert their time delay in distances. These distances are next used to solve a triangulation scheme that leads to the defect location. In this paper, this inconvenient is avoided by processing the time transient measurements acquired at the different locations with a "Warped Frequency Transform" (WFT) that is capable to reveal the distance travelled by dispersive waves. In fact, by means of the WFT the recorded time waveform is converted into the incipient pulse at a distance from the origin which is proportional to the distance travelled by a mode within the signal, thus fully compensating its dispersive effect. Then, the processed time waveforms recorded from simple sensors can be used for locating defects by means of classical triangulation procedures.
Faster-Than-Light Space Warps, Status and Next Steps
NASA Astrophysics Data System (ADS)
Davis, E. W.
Implementation of faster-than-light (FTL) interstellar travel via traversable wormholes or warp drives requires the engineering of spacetime into very specialized local geometries. The analysis of these via Einstein's General Theory of Relativity demonstrates that such geometries require the use of ``exotic'' matter. One can appeal to quantum field theory to find both natural and phenomenological sources of exotic matter. Such quantum fields are disturbed by the curved spacetime geometry they produce, so their energy-momentum tensor can be used to probe the back-reaction of the field effects upon the dynamics of the FTL spacetime, which has implications on the construction and control of FTL spacetimes. Also, the production, detection, and deployment of natural exotic quantum fields are seen to be key technical challenges in which basic first steps can be taken to experimentally probe their properties. FTL spacetimes also possess features that challenge the notions of momentum conservation and causality. The status of these important issues is addressed in this report, and recommended next steps for further theoretical investigations are identified in an effort to clear up a number of technical uncertainties in order to progress the present state-of-the-art in FTL spacetime physics.
Radiation-driven warping of circumbinary disks around eccentric young star binaries
Hayasaki, Kimitake; Sohn, Bong Won; Jung, Taehyun; Zhao, Guangyao; Okazaki, Atsuo T.; Naito, Tsuguya
2014-12-10
We study a warping instability of a geometrically thin, non-self-gravitating, circumbinary disk around young binary stars on an eccentric orbit. Such a disk is subject to both the tidal torques due to a time-dependent binary potential and the radiative torques due to radiation emitted from each star. The tilt angle between the circumbinary disk plane and the binary orbital plane is assumed to be very small. We find that there is a radius within/beyond which the circumbinary disk is unstable to radiation-driven warping, depending on the disk density and temperature gradient indices. This marginally stable warping radius is very sensitive to viscosity parameters, a fiducial disk radius and the temperature measured there, the stellar luminosity, and the disk surface density at a radius where the disk changes from optically thick to thin for the irradiation from the central stars. On the other hand, it is insensitive to the orbital eccentricity and binary irradiation parameter, which is a function of the binary mass ratio and luminosity of each star. Since the tidal torques can suppress the warping in the inner part of the circumbinary disk, the disk starts to be warped in the outer part. While the circumbinary disks are most likely to be subject to the radiation-driven warping on an AU to kilo-AU scale for binaries with young massive stars more luminous than 10{sup 4} L {sub ☉}, the radiation-driven warping does not work for those around young binaries with the luminosity comparable to the solar luminosity.
Radiation-driven Warping of Circumbinary Disks around Eccentric Young Star Binaries
NASA Astrophysics Data System (ADS)
Hayasaki, Kimitake; Sohn, Bong Won; Okazaki, Atsuo T.; Jung, Taehyun; Zhao, Guangyao; Naito, Tsuguya
2014-12-01
We study a warping instability of a geometrically thin, non-self-gravitating, circumbinary disk around young binary stars on an eccentric orbit. Such a disk is subject to both the tidal torques due to a time-dependent binary potential and the radiative torques due to radiation emitted from each star. The tilt angle between the circumbinary disk plane and the binary orbital plane is assumed to be very small. We find that there is a radius within/beyond which the circumbinary disk is unstable to radiation-driven warping, depending on the disk density and temperature gradient indices. This marginally stable warping radius is very sensitive to viscosity parameters, a fiducial disk radius and the temperature measured there, the stellar luminosity, and the disk surface density at a radius where the disk changes from optically thick to thin for the irradiation from the central stars. On the other hand, it is insensitive to the orbital eccentricity and binary irradiation parameter, which is a function of the binary mass ratio and luminosity of each star. Since the tidal torques can suppress the warping in the inner part of the circumbinary disk, the disk starts to be warped in the outer part. While the circumbinary disks are most likely to be subject to the radiation-driven warping on an AU to kilo-AU scale for binaries with young massive stars more luminous than 104 L ⊙, the radiation-driven warping does not work for those around young binaries with the luminosity comparable to the solar luminosity.
THE LINDA CRANE MEMORIAL LECTUR
2011-01-01
At 90 years of age, the APTA may be facing some of the greatest national and global challenges of its history. Membership has grown from 238 in 1921 to over 70,000 in 2011, but the expansion of the APTA may be restrictive to individual participation. A leadership gap appears imminent in practice and education. Fostering every member to understand the APTA and its great work is essential to ensuring a profession that lives its core values and meets societal needs. The Linda Crane Memorial Lecture in 2011 celebrated a vision of the APTA's 100th birthday with every member serving as a “professional centenarian” who stewards the organization to continued greatness. PMID:21637394
Lecture notes for criticality safety
Fullwood, R.
1992-03-01
These lecture notes for criticality safety are prepared for the training of Department of Energy supervisory, project management, and administrative staff. Technical training and basic mathematics are assumed. The notes are designed for a two-day course, taught by two lecturers. Video tapes may be used at the options of the instructors. The notes provide all the materials that are necessary but outside reading will assist in the fullest understanding. The course begins with a nuclear physics overview. The reader is led from the macroscopic world into the microscopic world of atoms and the elementary particles that constitute atoms. The particles, their masses and sizes and properties associated with radioactive decay and fission are introduced along with Einstein`s mass-energy equivalence. Radioactive decay, nuclear reactions, radiation penetration, shielding and health-effects are discussed to understand protection in case of a criticality accident. Fission, the fission products, particles and energy released are presented to appreciate the dangers of criticality. Nuclear cross sections are introduced to understand the effectiveness of slow neutrons to produce fission. Chain reactors are presented as an economy; effective use of the neutrons from fission leads to more fission resulting in a power reactor or a criticality excursion. The six-factor formula is presented for managing the neutron budget. This leads to concepts of material and geometric buckling which are used in simple calculations to assure safety from criticality. Experimental measurements and computer code calculations of criticality are discussed. To emphasize the reality, historical criticality accidents are presented in a table with major ones discussed to provide lessons-learned. Finally, standards, NRC guides and regulations, and DOE orders relating to criticality protection are presented.
Lecture notes for criticality safety
Fullwood, R.
1992-03-01
These lecture notes for criticality safety are prepared for the training of Department of Energy supervisory, project management, and administrative staff. Technical training and basic mathematics are assumed. The notes are designed for a two-day course, taught by two lecturers. Video tapes may be used at the options of the instructors. The notes provide all the materials that are necessary but outside reading will assist in the fullest understanding. The course begins with a nuclear physics overview. The reader is led from the macroscopic world into the microscopic world of atoms and the elementary particles that constitute atoms. The particles, their masses and sizes and properties associated with radioactive decay and fission are introduced along with Einstein's mass-energy equivalence. Radioactive decay, nuclear reactions, radiation penetration, shielding and health-effects are discussed to understand protection in case of a criticality accident. Fission, the fission products, particles and energy released are presented to appreciate the dangers of criticality. Nuclear cross sections are introduced to understand the effectiveness of slow neutrons to produce fission. Chain reactors are presented as an economy; effective use of the neutrons from fission leads to more fission resulting in a power reactor or a criticality excursion. The six-factor formula is presented for managing the neutron budget. This leads to concepts of material and geometric buckling which are used in simple calculations to assure safety from criticality. Experimental measurements and computer code calculations of criticality are discussed. To emphasize the reality, historical criticality accidents are presented in a table with major ones discussed to provide lessons-learned. Finally, standards, NRC guides and regulations, and DOE orders relating to criticality protection are presented.
Reis, Shmuel
2016-04-01
Luder shows that there is a lack of correlation between lecture attendance in medical school and examination performance, and thus draws attention to a discourse concerning the place of lectures and lecture attendance enforcement in 2015 and beyond. The paper addresses 4 questions: First, what is the current place of the traditional lecture in the education of medical students? Second, are there alternatives to this format of teaching? Third, what are the educational consequences of mandating lecture attendance; and fourth, should there be such enforcement? The author discusses these questions and concludes that lectures should be used sparingly, after a careful evaluation that they have an added value over learning away from the classroom. Furthermore, that there are clear guidelines on how to make the traditional lecture enhanced and educationally effective, as well as alternatives such as the "flipped classroom", e-learning and more to lectures. In addition, that lectures frequently drive learning negatively and enforcing attendance in Israel entails serious unintended consequences such as a need to monitor attendance, and a host of disciplinary adverse reactions. Finally, that besides lecture efficiency and economy (when having added value) one reason to consider compulsory attendance, may be when poor attendance negatively influences teachers morale. PMID:27323539
Engagement of students with lectures in biochemistry and pharmacology.
Davis, Elizabeth Ann; Hodgson, Yvonne; Macaulay, Janet Olwyn
2012-01-01
Academic staff at universities have become concerned about the decrease in student attendance at lectures and the implication of this on student achievement and learning. Few studies have measured actual lecture attendance in a coherent or comprehensive way. The aim of this study was to measure actual lecture attendance of students over two year levels enrolled in two separate science disciplines, biochemistry and pharmacology. The study further sought to determine the factors that influence lecture attendance. Attendance at lectures in four units of study was monitored over a 12-week semester. Attendance at lectures decreased over the semester and was lower at early morning lectures (8 A.M.; 9 A.M.). A questionnaire surveying students about their preparation for lectures, their compensation for missed lectures and the factors influencing their nonattendance was administered at the end of the semester. Students reported that the major factors influencing their attendance at lectures related to timetable issues and the quality of lecturing. If students missed lectures, the majority read the lecture notes and listened to the online recordings. The availability of online recordings of lectures was not a major influence on attendance at lectures. In three of the four units studied there was no correlation between self-reported lecture attendance and exam performance. The results of the study indicate that universities should dedicate more resources to timetabling and to supporting staff to improve the quality of their lectures. PMID:22987551
NASA Astrophysics Data System (ADS)
More, Anupreeta; Verma, Aprajita; Marshall, Philip J.; More, Surhud; Baeten, Elisabeth; Wilcox, Julianne; Macmillan, Christine; Cornen, Claude; Kapadia, Amit; Parrish, Michael; Snyder, Chris; Davis, Christopher P.; Gavazzi, Raphael; Lintott, Chris J.; Simpson, Robert; Miller, David; Smith, Arfon M.; Paget, Edward; Saha, Prasenjit; Küng, Rafael; Collett, Thomas E.
2016-01-01
We report the discovery of 29 promising (and 59 total) new lens candidates from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) based on about 11 million classifications performed by citizen scientists as part of the first SPACE WARPS lens search. The goal of the blind lens search was to identify lens candidates missed by robots (the RINGFINDER on galaxy scales and ARCFINDER on group/cluster scales) which had been previously used to mine the CFHTLS for lenses. We compare some properties of the samples detected by these algorithms to the SPACE WARPS sample and find them to be broadly similar. The image separation distribution calculated from the SPACE WARPS sample shows that previous constraints on the average density profile of lens galaxies are robust. SPACE WARPS recovers about 65 per cent of known lenses, while the new candidates show a richer variety compared to those found by the two robots. This detection rate could be increased to 80 per cent by only using classifications performed by expert volunteers (albeit at the cost of a lower purity), indicating that the training and performance calibration of the citizen scientists is very important for the success of SPACE WARPS. In this work we present the SIMCT pipeline, used for generating in situ a sample of realistic simulated lensed images. This training sample, along with the false positives identified during the search, has a legacy value for testing future lens-finding algorithms. We make the pipeline and the training set publicly available.
Evaluation and application of 3D lung warping and registration model using HRCT images
NASA Astrophysics Data System (ADS)
Fan, Li; Chen, Chang W.; Reinhardt, Joseph M.; Hoffman, Eric A.
2001-05-01
Image-based study of structure-function relationships is a challenging problem in that the structure or region of interest may vary in position and shape on images captured over time. Such variation may be caused by the change in body posture or the motion of breathing and heart beating. Therefore, the structure or region of interest should be registered before any further regional study can be carried out. In this paper, we propose a novel approach to study the structure-function relationship of ventilation using a previously developed 3D lung warping and registration model. First, we evaluate the effectiveness of the lung warping and registration model using a set of criteria, including apparent lung motion patterns and ground truths. Then, we study the ventilation by integrating the warping model with air content calibration. The warping model is applied to three CT lung data sets, obtained under volume control of FRC, 40% and 75% vital capacity (VC). Dense displacement fields are obtained to represent deformation between different lung volume steps. For any specific region of interest, we first register it between images over time using the dense displacement, and then estimate the corresponding regional inspired air content. Assessments include change of regional volume during inspiration, change of regional air content, and the distribution of regional ventilation. This is the first time that 3D warping of lung images is applied to assess clinically significant pulmonary functions.
Experimental Investigation About Stamping Behaviour of 3D Warp Interlock Composite Preforms
NASA Astrophysics Data System (ADS)
Dufour, Clément; Wang, Peng; Boussu, François; Soulat, Damien
2014-10-01
Forming of continuous fibre reinforcements and thermoplastic resin commingled prepregs can be performed at room temperature due to its similar textile structure. The "cool" forming stage is better controlled and more economical. The increase of temperature and the resin consolidation phases after the forming can be carried out under the isothermal condition thanks to a closed system. It can avoid the manufacturing defects easily experienced in the non-isothermal thermoforming, in particular the wrinkling [1]. Glass/Polypropylene commingled yarns have been woven inside different three-dimensional (3D) warp interlock fabrics and then formed using a double-curved shape stamping tool. The present study investigates the in-plane and through-thickness behaviour of the 3D warp interlock fibrous reinforcements during forming with a hemispherical punch. Experimental data allow analysing the forming behaviour in the warp and weft directions and on the influence of warp interlock architectures. The results point out that the layer to layer warp interlock preform has a better stamping behaviour, in particular no forming defects and good homogeneity in thickness.
Theory of Band Warping and its Effects on Thermoelectronic Transport Properties
NASA Astrophysics Data System (ADS)
Mecholsky, Nicholas; Resca, Lorenzo; Pegg, Ian; Fornari, Marco
2015-03-01
Transport properties of materials depend upon features of band structures near extrema in the BZ. Such features are generally described in terms of quadratic expansions and effective masses. Such expansions, however, are permissible only under strict conditions that are sometimes violated by materials. Suggestive terms such as ``band warping'' have been used to refer to such situations and ad hoc methods have been developed to treat them. We develop a generally applicable theory, based on radial expansions, and a corresponding definition of angular effective mass which also accounts for effects of band non-parabolicity and anisotropy. Further, we develop precise procedures to evaluate band warping quantitatively and as an example we analyze the warping features of valence bands in silicon using first-principles calculations and we compare those with semi-empirical models. We use our theory to generalize derivations of transport coefficients for cases of either single or multiple electronic bands, with either quadratically expansible or warped energy surfaces. We introduce the transport-equivalent ellipsoid and illustrate the drastic effects that band warping can induce on thermoelectric properties using multi-band models. Vitreous State Laboratory and Samsung's GRO program.
Probing the presence of planets in transition discs' cavities via warps: the case of TW Hya
NASA Astrophysics Data System (ADS)
Facchini, Stefano; Ricci, Luca; Lodato, Giuseppe
2014-08-01
We are entering the era in which observations of protoplanetary disc's properties can indirectly probe the presence of massive planets or low-mass stellar companions interacting with the disc. In particular, the detection of warped discs can provide important clues to the properties of the star-disc system. In this paper, we show how observations of warped discs can be used to infer the dynamical properties of the systems. We concentrate on circumbinary discs, where the mass of the secondary can be planetary. First, we provide some simple relations that link the amplitude of the warp in the linear regime to the parameters of the system. Secondly, we apply our method to the case of TW Hya, a transition disc for which a warp has been proposed based on spectroscopic observations. Assuming values for the disc and stellar parameters from observations, we conclude that, in order for a warp induced by a planetary companion to be detectable, the planet mass should be large (Mp ≈ 10-14MJ) and the disc should be viscous (α ≈ 0.15-0.25). We also apply our model to LkCa 15 and T Cha, where a substellar companion has been detected within the central cavity of the transition discs.
Alignment of Quasar Polarizations on Large Scales Explained by Warped Cosmic Strings
NASA Astrophysics Data System (ADS)
Slagter, Reinoud Jan
The recently discovered alignment of quasar polarizations on very large scales could possibly explained by considering cosmic strings on a warped five dimensional spacetime. Compact objects, such as cosmic strings, could have tremendous mass in the bulk, while their warped manifestations in the brane can be consistent with general relativity in 4D. The self-gravitating cosmic string induces gravitational wavelike disturbances which could have effects felt on the brane, i.e., the massive effective 4D modes (Kaluza-Klein modes) of the perturbative 5D graviton. This effect is amplified by the time dependent part of the warp factor. Due to this warp factor, disturbances don't fade away during the expansion of the universe. From a non-linear perturbation analysis it is found that the effective Einstein 4D equations on an axially symmetric spacetime, contain a "back-reaction" term on the righthand side caused by the projected 5D Weyl tensor and can act as a dark energy term. The propagation equations to first order for the metric components and scalar-gauge fields contain $\\varphi$-dependent terms, so the approximate wave solutions are no longer axially symmetric. The disturbances, amplified by the warp factor, can possess extremal values for fixed polar angles. This could explain the two preferred polarization vectors mod $(\\varphi, 90^o)$.
Killing tensors, warped products and the orthogonal separation of the Hamilton-Jacobi equation
Rajaratnam, Krishan McLenaghan, Raymond G.
2014-01-15
We study Killing tensors in the context of warped products and apply the results to the problem of orthogonal separation of the Hamilton-Jacobi equation. This work is motivated primarily by the case of spaces of constant curvature where warped products are abundant. We first characterize Killing tensors which have a natural algebraic decomposition in warped products. We then apply this result to show how one can obtain the Killing-Stäckel space (KS-space) for separable coordinate systems decomposable in warped products. This result in combination with Benenti's theory for constructing the KS-space of certain special separable coordinates can be used to obtain the KS-space for all orthogonal separable coordinates found by Kalnins and Miller in Riemannian spaces of constant curvature. Next we characterize when a natural Hamiltonian is separable in coordinates decomposable in a warped product by showing that the conditions originally given by Benenti can be reduced. Finally, we use this characterization and concircular tensors (a special type of torsionless conformal Killing tensor) to develop a general algorithm to determine when a natural Hamiltonian is separable in a special class of separable coordinates which include all orthogonal separable coordinates in spaces of constant curvature.
A sinogram warping strategy for pre-reconstruction 4D PET optimization.
Gianoli, Chiara; Riboldi, Marco; Fontana, Giulia; Kurz, Christopher; Parodi, Katia; Baroni, Guido
2016-03-01
A novel strategy for 4D PET optimization in the sinogram domain is proposed, aiming at motion model application before image reconstruction ("sinogram warping" strategy). Compared to state-of-the-art 4D-MLEM reconstruction, the proposed strategy is able to optimize the image SNR, avoiding iterative direct and inverse warping procedures, which are typical of the 4D-MLEM algorithm. A full-count statistics sinogram of the motion-compensated 4D PET reference phase is generated by warping the sinograms corresponding to the different PET phases. This is achieved relying on a motion model expressed in the sinogram domain. The strategy was tested on the anthropomorphic 4D PET-CT NCAT phantom in comparison with the 4D-MLEM algorithm, with particular reference to robustness to PET-CT co-registrations artefacts. The MLEM reconstruction of the warped sinogram according to the proposed strategy exhibited better accuracy (up to +40.90 % with respect to the ideal value), whereas images reconstructed according to the 4D-MLEM reconstruction resulted in less noisy (down to -26.90 % with respect to the ideal value) but more blurred. The sinogram warping strategy demonstrates advantages with respect to 4D-MLEM algorithm. These advantages are paid back by introducing approximation of the deformation field, and further efforts are required to mitigate the impact of such an approximation in clinical 4D PET reconstruction. PMID:26126871
CERN LHC signals for warped electroweak neutral gauge bosons
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Davoudiasl, Hooman; Gopalakrishna, Shrihari; Han, Tao; Huang, Gui-Yu; Perez, Gilad; Si, Zong-Guo; Soni, Amarjit
2007-12-01
We study signals at the Large Hadron Collider (LHC) for Kaluza-Klein (KK) excitations of the electroweak gauge bosons in the framework with the standard model (SM) gauge and fermion fields propagating in a warped extra dimension. Such a framework addresses both the Planck-weak and flavor hierarchy problems of the SM. Unlike the often studied Z' cases, in this framework, there are three neutral gauge bosons due to the underlying SU(2)L×SU(2)R×U(1)X gauge group in the bulk. Furthermore, couplings of these KK states to light quarks and leptons are suppressed, whereas those to top and bottom quarks are enhanced compared to the SM gauge couplings. Therefore, the production of light quark and lepton states is suppressed relative to other beyond the SM constructions, and the fermionic decays of these states are dominated by the top and bottom quarks, which are, though, overwhelmed by KK gluons dominantly decaying into them. However, as we emphasize in this paper, decays of these states to longitudinal W, Z and Higgs are also enhanced similarly to the case of top and bottom quarks. We show that the W, Z and Higgs final states can give significant sensitivity at the LHC to ˜2(3)TeV KK scale with an integrated luminosity of ˜100fb-1 (˜1ab-1). Since current theoretical framework(s) favor KK masses ≳3TeV, a luminosity upgrade of LHC is likely to be crucial in observing these states.
Ring Dynamics at Saturn: Wakes, Resonances, Warps and Orbital Migration
NASA Astrophysics Data System (ADS)
Nicholson, Philip D.; Hedman, M. M.; Tiscareno, M. S.; Burns, J. A.; French, R. G.; French, R. G.; Marouf, E. A.; Colwell, J. E.
2012-01-01
In addition to their incomparable beauty in a small telescope, the rings of Saturn have long provided astronomers with a nearby laboratory for developing and testing theories of disk dynamics. After seven years of successful operations, the Cassini orbiter has greatly increased our knowledge of this system, and revealed many new and unexpected phenomena. Ring thicknesses of as little as 5-10 meters are inferred from particle velocity dispersions and from the ubiquitous `self-gravity wakes'. The latter are close cousins of the trailing structures seen in simulations of self-gravitating stellar disks in the 1980s. Two of the 15 or so narrow gaps in the rings are maintained by km-size embedded moonlets; the others remain unexplained though several have edges defined by Lindblad resonances with larger, external satellites. Many gap and ringlet edges are noncircular, exhibiting a surprisingly wide range of perturbations which seem to reflect multiple `normal modes' excited within the rings. Images taken near the Saturnian equinox in mid-2009 under conditions of grazing solar illumination reveal a spiral-shaped warp which extends all the way across the C and D rings. Models of this structure strongly suggest that it is due to an impact on the rings of a cloud of interplanetary debris in September 1983, perhaps due to a disrupted comet like Shoemaker-Levy 9. Although even Cassini is unable to image individual ring particles, the highest resolution images of the A ring show intriguing structures known as `propellers' which appear to be the gravitational signature of large embedded objects, perhaps 100 m in size. Long-term tracking of the largest propellers shows clear evidence for non-keplerian motion, possibly akin to the orbital migration predicted for protoplanets embedded in circumstellar disks.
The Impact of Online Lecture Recordings on Student Performance
ERIC Educational Resources Information Center
Williams, Andrew; Birch, Elisa; Hancock, Phil
2012-01-01
The use of online lecture recordings as a supplement to physical lectures is an increasingly popular tool at many universities. This paper combines survey data with student record data for students in a "Microeconomics Principles" class to examine the relative effects of lecture attendance and online lecture recordings. The main finding is that…
Michael Faraday: Prince of lecturers in Victorian England
NASA Astrophysics Data System (ADS)
Lan, Boon Leong; Lim, Jeanette B. S.
2001-01-01
In this note, we focus on Faraday as a lecturer/teacher. We trace his development as a lecturer/teacher and highlight his approaches in popular-science lecturing and in teaching chemistry to military cadets. We appraise his success and conclude with an account of his poignant last lecture.
Educational Effect of Online Lecture using Streaming Technology
NASA Astrophysics Data System (ADS)
Akiyama, Hidenori; Teramoto, Akemi; Kozono, Kazutake
A conventional lecture on Laser Engineering had been done in a lecture room till 1999. A content using on-demand streaming method was made for an online lecture of Laser Engineering in 2000. The figures and equations used on the conventional lecture and the voice recorded for the online lecture were converted to the real media. Then an online lecture has been provided to students by using a Helix Universal Server. The trial of the online lecture was done only for the students who wanted to take the online lecture course in 2000. The online lectures have been recognized as the credits for graduation by the change of a law since 2001. About 100 students have registered the online lecture of Laser Engineering every year since 2001. Here, three years' questionnaire surveys of the online lecture are summarized, and results of examinations on the conventional lecture for two years and on the online lecture for three years are compared. It is recognized for the lecture of Laser Engineering that the educational effect of the online lecture is comparable to or better than that of the conventional lecture.
Factors Shaping Mathematics Lecturers' Service Teaching in Different Departments
ERIC Educational Resources Information Center
Bingolbali, E.; Ozmantar, M. F.
2009-01-01
In this article we focus on university lecturers' approaches to the service teaching and factors that influence their approaches. We present data obtained from the interviews with 19 mathematics and three physics lecturers along with the observations of two mathematics lecturers' calculus courses. The findings show that lecturers' approaches to…
The Feasibility of Using Taped Lectures to Replace Class Attendance.
ERIC Educational Resources Information Center
Menne, John W.; And Others
The students in an introductory college psychology course were given the option of attending live lectures (control group) or listening to audio-taped lectures (experimental group). Each experimental subject was issued a tape recorder, a set of lecture tapes, and a schedule of lecture topics as presented to the control group. Conducted in the fall…
WARP: Weight Associative Rule Processor. A dedicated VLSI fuzzy logic megacell
NASA Technical Reports Server (NTRS)
Pagni, A.; Poluzzi, R.; Rizzotto, G. G.
1992-01-01
During the last five years Fuzzy Logic has gained enormous popularity in the academic and industrial worlds. The success of this new methodology has led the microelectronics industry to create a new class of machines, called Fuzzy Machines, to overcome the limitations of traditional computing systems when utilized as Fuzzy Systems. This paper gives an overview of the methods by which Fuzzy Logic data structures are represented in the machines (each with its own advantages and inefficiencies). Next, the paper introduces WARP (Weight Associative Rule Processor) which is a dedicated VLSI megacell allowing the realization of a fuzzy controller suitable for a wide range of applications. WARP represents an innovative approach to VLSI Fuzzy controllers by utilizing different types of data structures for characterizing the membership functions during the various stages of the Fuzzy processing. WARP dedicated architecture has been designed in order to achieve high performance by exploiting the computational advantages offered by the different data representations.
NASA Technical Reports Server (NTRS)
Subrahmanyam, K. B.; Kaza, K. R. V.
1985-01-01
Theoretical natural frequencies of the first three modes of torsional vibration of pretwisted, rotating cantilever beams are determined for various thickness and aspect ratios. Conclusions concerning individual and collective effects of warping, pretwist, tension-torsion coupling and tennis racket effect (twist-rotational coupling) terms on the natural frequencies are drawn from numerical results obtained by using a finite difference procedure with first order central differences. The relative importance of structural warping, inertial warping, pretwist, tension-torsion and twist-rotational coupling terms is discussed for various rotational speeds. The accuracy of results obtained by using the finite difference approach is verified by a comparison with the exact solution for specialized simple cases of the equation of motion used in this paper.
Effective Hamiltonian for surface states of topological insulator thin films with hexagonal warping
NASA Astrophysics Data System (ADS)
Siu, Zhuo Bin; Tan, Seng Ghee; Jalil, Mansoor B. A.
2016-05-01
The effective Hamiltonian of the surface states on semi-infinite slabs of the topological insulators (TI) Bi2Te3 and Bi2Se3 require the addition of a cubic momentum hexagonal warping term on top of the usual Dirac fermion Hamiltonian in order to reproduce the experimentally measured constant energy contours at intermediate values of Fermi energy. In this work, we derive the effective Hamiltonian for the surface states of a Bi2Se3 thin film incorporating the corresponding hexagonal warping terms. We then calculate the dispersion relation of the effective Hamiltonian and show that the hexagonal warping leads distorts the equal energy contours from the circular cross sections of the Dirac cones.
Design of a reading test for low-vision image warping
NASA Astrophysics Data System (ADS)
Loshin, David S.; Wensveen, Janice; Juday, Richard D.; Barton, R. Shane
1993-08-01
NASA and the University of Houston College of Optometry are examining the efficacy of image warping as a possible prosthesis for at least two forms of low vision -- maculopathy and retinitis pigmentosa. Before incurring the expense of reducing the concept to practice, one would wish to have confidence that a worthwhile improvement in visual function would result. NASA's Programmable Remapper (PR) can warp an input image onto arbitrary geometric coordinate systems at full video rate, and it has recently been upgraded to accept computer- generated video text. We have integrated the Remapper with an SRI eye tracker to simulate visual malfunction in normal observers. A reading performance test has been developed to determine if the proposed warpings yield an increase in visual function; i.e., reading speed. We describe the preliminary experimental results of this reading test with a simulated central field defect with and without remapped images.
The Origin of Warped, Precessing Accretion Disks in X-ray Binaries
NASA Technical Reports Server (NTRS)
Maloney, Philip R.; Begelman, Mitchell C.
1997-01-01
The radiation-driven warping instability discovered by Pringle holds considerable promise as the mechanism responsible for producing warped, precessing accretion disks in X-ray binaries. This instability is an inherently global mode of the disk, thereby avoiding the difficulties with earlier models for the precession. Here we follow up on earlier work to study the linear behavior of the instability in the specific context of a binary system. We treat the influence of the companion as an orbit-averaged quadrupole torque on the disk. The presence of this external torque allows the existence of solutions in which the direction of precession of the warp is retrograde with respect to disk rotation, in addition to the prograde solutions that exist in the absence of external torques.
Promoting Interactivity in Physics Lecture Classes.
ERIC Educational Resources Information Center
Meltzer, David E.; Manivannan, Kandiah
1996-01-01
Presents techniques aimed at promoting a higher level of student-faculty interaction and active student participation in the learning process in introductory physics lecture classes. Discusses group problem solving, the use of flash cards, and assessment. (JRH)
Charles Ichoku Maniac Lecture, July 25, 2016
NASA climate scientist Charles Ichoku presented a Maniac lecture entitled, "Reminiscences of a scientist's journey from Nawfia to NASA." Born in a small town in Nigeria, Charles traced his captivat...
Making lectures memorable: A cognitive perspective.
Afzal, Azam; Babar, Shazia
2016-08-01
Lectures have been a cornerstone of medical education since the introduction of a discipline based curricular model more than two hundred years ago. Recently this instructional strategy has come under criticism because of its reliance on passive learning. There are still many medical schools that cover content predominantly through lectures due to its feasibility. With the introduction of the flipped classrooms, lectures have been given a new lease of life. Improving cognitive imprinting during lectures would enhance retrieval and promote long term storage. Simplifying the content reduces the cognitive load of the information being received and makes it more meaningful hence more memorable. To make learning memorable, rehearsal should be built into the sessions. With the exponential increase in online learning, the need for online learning technologies will require a generation of a large amount of asynchronous video content which should ideally be truly meaningful and memorable, and inspirational to our students. PMID:27524541
Teaching Principles of Economics Without Lectures
ERIC Educational Resources Information Center
McConnell, Campbell R.; Lamphear, Charles
1969-01-01
Presents important evidence thatstudents taking principles of economics with lectures, and those taking the course on a lectureless basis performed equally well on an intensive battery of objective examinations." (Editor)
Lectures on probability and statistics
Yost, G.P.
1984-09-01
These notes are based on a set of statistics lectures delivered at Imperial College to the first-year postgraduate students in High Energy Physics. They are designed for the professional experimental scientist. We begin with the fundamentals of probability theory, in which one makes statements about the set of possible outcomes of an experiment, based upon a complete a priori understanding of the experiment. For example, in a roll of a set of (fair) dice, one understands a priori that any given side of each die is equally likely to turn up. From that, we can calculate the probability of any specified outcome. We finish with the inverse problem, statistics. Here, one begins with a set of actual data (e.g., the outcomes of a number of rolls of the dice), and attempts to make inferences about the state of nature which gave those data (e.g., the likelihood of seeing any given side of any given die turn up). This is a much more difficult problem, of course, and one's solutions often turn out to be unsatisfactory in one respect or another.
The WARPS Survey - VIII. Evolution of the galaxy cluster X-ray Luminosity Function
NASA Astrophysics Data System (ADS)
Koens, L. A.; Maughan, B. J.; Jones, L. R.; Ebeling, H.; Horner, D. J.; Perlman, E. S.; Phillipps, S.; Scharf, C. A.
2013-11-01
We present measurements of the galaxy cluster X-ray Luminosity Function (XLF) from the Wide Angle ROSAT Pointed Survey (WARPS) and quantify its evolution. WARPS is a serendipitous survey of the central region of ROSAT pointed observations and was carried out in two phases (WARPS-I and WARPS-II). The results here are based on a final sample of 124 clusters, complete above a flux limit of 6.5 × 10-14 erg cm-2 s-1, with members out to redshift z ˜ 1.05, and a sky coverage of 70.9 deg2. We find significant evidence for negative evolution of the XLF, which complements the majority of X-ray cluster surveys. To quantify the suggested evolution, we perform a maximum likelihood analysis and conclude that the evolution is driven by a decreasing number density of high-luminosity clusters with redshift, while the bulk of the cluster population remains nearly unchanged out to redshift z ≈ 1.1, as expected in a low-density universe. The results are found to be insensitive to a variety of sources of systematic uncertainty that affect the measurement of the XLF and determination of the survey selection function. We perform a Bayesian analysis of the XLF to fully account for uncertainties in the local XLF on the measured evolution, and find that the detected evolution remains significant at the 95 per cent level. We observe a significant excess of clusters in the WARPS at 0.1 < z < 0.3 and LX ≈ 2 × 1043 erg s-1 compared with the reference low-redshift XLF, or our Bayesian fit to the WARPS data. We find that the excess cannot be explained by sample variance, or Eddington bias, and is unlikely to be due to problems with the survey selection function.
A peculiar lecture by Ettore Majorana
NASA Astrophysics Data System (ADS)
Esposito, S.
2006-09-01
We give, for the first time, the English translation of a manuscript by Ettore Majorana, which probably corresponds to the text for a seminar lecture delivered at the University of Naples in 1938, where he lectured on theoretical physics. Some passages reveal a physical interpretation of quantum mechanics which anticipates for several years the Feynman approach in terms of path integrals, independent of the underlying mathematical formulation.
Authoring Software to Make Online Lecture Contents
NASA Astrophysics Data System (ADS)
Kozono, Kazutake; Teramoto, Akemi; Akiyama, Hidenori
An authoring software for online lecture contents has been developed. Various multimedia such as HTML, SMIL and Real System are integrated in this software, which is named EzClassMaker. Professors who are not familiar to the information technology can make the online lecture content including the sound and movies, and place the content on Leaning Management System by using this software. Only the microcomputer with this software and a microphone (or a movie camera) is requested to make the content.
Theory of band warping and its effects on thermoelectronic transport properties
NASA Astrophysics Data System (ADS)
Mecholsky, Nicholas A.; Resca, Lorenzo; Pegg, Ian L.; Fornari, Marco
2014-04-01
Optical and transport properties of materials depend heavily upon features of electronic band structures in proximity of energy extrema in the Brillouin zone (BZ). Such features are generally described in terms of multidimensional quadratic expansions and corresponding definitions of effective masses. Multidimensional quadratic expansions, however, are permissible only under strict conditions that are typically violated when energy bands become degenerate at extrema in the BZ. Even for energy bands that are nondegenerate at critical points in the BZ there are instances in which multidimensional quadratic expansions cannot be correctly performed. Suggestive terms such as "band warping," "fluted energy surfaces," or "corrugated energy surfaces" have been used to refer to such situations and ad hoc methods have been developed to treat them. While numerical calculations may reflect such features, a complete theory of band warping has not hitherto been developed. We define band warping as referring to band structures that do not admit second-order differentiability at critical points in k space and we develop a generally applicable theory, based on radial expansions, and a corresponding definition of angular effective mass. Our theory also accounts for effects of band nonparabolicity and anisotropy, which hitherto have not been precisely distinguished from, if not utterly confused with, band warping. Based on our theory, we develop precise procedures to evaluate band warping quantitatively. As a benchmark demonstration, we analyze the warping features of valence bands in silicon using first-principles calculations and we compare those with previous semiempirical models. As an application of major significance to thermoelectricity, we use our theory and angular effective masses to generalize derivations of tensorial transport coefficients for cases of either single or multiple electronic bands, with either quadratically expansible or warped energy surfaces. From that
Killing-Yano forms and Killing tensors on a warped space
NASA Astrophysics Data System (ADS)
Krtouš, Pavel; KubizÅák, David; Kolář, Ivan
2016-01-01
We formulate several criteria under which the symmetries associated with the Killing and Killing-Yano tensors on the base space can be lifted to the symmetries of the full warped geometry. The procedure is explicitly illustrated on several examples, providing new prototypes of spacetimes admitting such tensors. In particular, we study a warped product of two Kerr-NUT-(A)dS spacetimes and show that it gives rise to a new class of highly symmetric vacuum (with a cosmological constant) black hole solutions that inherit many of the properties of the Kerr-NUT-(A)dS geometry.
Warped AdS3 black holes in higher derivative gravity theories
NASA Astrophysics Data System (ADS)
Detournay, Stéphane; Douxchamps, Laure-Anne; Ng, Gim Seng; Zwikel, Céline
2016-06-01
We consider warped AdS3 black holes in generic higher derivatives gravity theories in 2+1 dimensions. The asymptotic symmetry group of the phase space containing these black holes is the semi-direct product of a centrally extended Virasoro algebra and an affine u(1) Kac-Moody algebra. Previous works have shown that in some specific theories, the entropy of these black holes agrees with a Cardy-like entropy formula derived for warped conformal field theories. In this paper, we show that this entropy matching continues to hold for the most general higher derivative theories of gravity. We also discuss the existence of phase transitions.
An arc-length warping algorithm for gesture recognition using quaternion representation.
Cifuentes, Jenny; Pham, Minh Tu; Moreau, Richard; Prieto, Flavio; Boulanger, Pierre
2013-01-01
This paper presents a new algorithm, called Dynamic Arc-Length Warping algorithm (DALW) for hand gesture recognition based on the orientation data. In this algorithm, after calculating the quaternion for each orientation measurement, we use DALW algorithm to obtain a similarity measure between different trajectories. We present the benefits of using quaternion alongside the implementation of Dynamic Arc Length Warping to present an optimized tool for gesture recognition.We show the advantages of this approach compared with other techniques. This tool can be used to distinguish similar and different gestures. An experimental validation is carried out to classify a series of simple human gestures. PMID:24111168
Torsional stresses in box beams with cross sections partially restrained against warping
NASA Technical Reports Server (NTRS)
Ebner, Hans
1934-01-01
The present report gives a method for computing the torsion of boxes with thin shear-resistant or simply tension-resistant walls under any torsional load, support and dimension. The final stress condition is developed from that of a principal system with unconstrained sectional warping corresponding to Bredt's formula and an additional stress condition due to constrained cross-sectional warping. This is computed by means of the deflection condition of the principal system from a statically indeterminate calculation. Conformably, the torsional rigidity of the final system is derived from that of the principal system with unconstrained sectional buckling.
NASA Astrophysics Data System (ADS)
Jiang, Jin-Wu
2016-06-01
We investigate the strain engineering and the edge effect for mechanical properties in graphene nanoribbons. The free edges of the graphene nanoribbons are warped due to compressive edge stresses. There is a structural transformation for the free edges from the three-dimensional warping configuration to the two-dimensional planar structure at the critical strain ɛc = 0.7%, at which the applied mechanical stress is equal to the intrinsic compressive edge stress. This structural transformation leads to step-like changes in several mechanical properties studied in the present work, including the Young's modulus, the Poisson's ratio, the quality factor of nanomechanical resonators, and the phonon edge mode.
Induced inflation from a 5D purely kinetic scalar field formalism on warped product spaces
NASA Astrophysics Data System (ADS)
Madriz Aguilar, J. E.
2008-01-01
Considering a separable and purely kinetic 5D scalar field we investigate the induction of 4D scalar potentials on a 4D constant foliation on the class of 5D warped product space-times. We obtain a quantum confinement of the inflaton modes given naturally from the model for at least a class of warping factors. We can recover a 4D inflationary scenario where the inflationary potential is geometrically induced from 5D and the effective equation of state in 4D that includes the effect of the inflaton field and the induced matter is Peff≃-ρeff.
Moens, Vince
2014-06-08
The purpose of this guide is to help successive students handle WARP. It outlines the installation of WARP on personal computers as well as super-computers and clusters. It furthermore teaches the reader how to handle the WARP environment and run basic scripts. Lastly it outlines how to execute the current Hollow Electron Beam Lens scripts.
ERIC Educational Resources Information Center
Mertens, Robert; Ketterl, Markus; Vornberger, Oliver
2007-01-01
Lecture recordings can be a powerful addition to traditional lectures and they can even serve as a main content source in a number of didactic scenarios. If users can quickly locate relevant passages in a recording, the recording combines the ease of search that comes with electronic text based media with the authenticity and wealth of information…
ERIC Educational Resources Information Center
White, Brian T.
2009-01-01
This paper address three questions apropos of those posed by Kadel (2006) in the context of a large introductory-level undergraduate science lecture course. These questions include how podcasting is used by professors and students, whether podcasting decreases lecture attendance, and if particular podcasting options are effective teaching tools.…
Students' Preferences for Types of Video Lectures: Lecture Capture vs. Screencasting Recordings
ERIC Educational Resources Information Center
Sadik, Alaa
2015-01-01
The use of online videos as a supplement to traditional lectures or as a way to reach students at remote sites has become increasingly popular in higher education. Faculty and university technology centers have focused on approaches to recording and distributing online video lectures over the last ten years. Regardless of learning outcomes, the…
Memory for a Lecture: Effects of Notes, Lecture Rate, and Informational Density
ERIC Educational Resources Information Center
Aiken, Edwin G.; And Others
1975-01-01
Examines the retention of a lecture by college students. Emphasis is on note taking procedures, information density and speech rate. Retention was measured 48 hours after lecture and was found to be superior when note taking was separated from listening and speech was at normal rate. (Author/DEP)
The AWM-SIAM Sonia Kovalesvky Lecture - 3 part Lecture Series
Lenhart, Suzanne; Lewis, Jennifer
2003-06-03
The Association for Women in Mathematics (AWM) in cooperation with the Society for Industrial and Applied Mathematics (SIAM) and with funding from the Department of Energy initiated a new lecture series. The purpose of the lecture series is to increase the visibility of women who have made significant contributions in applied or computational mathematics. The AWM-SIAM Sonia Kovalevsky Lecture is presented at the SIAM Annual Meeting which is a national conference. The lecturer is a woman who has made distinguished contributions in applied or computational mathematics. The lecturer is determined by the Selection Committee which consists of two members of AWM and two members of SIAM, appointed by the presidents of these organizations. The committee may solicit nominations from other members of the scientific and engineering community. The lectureship may be awarded to any woman in the scientific or engineering community.
Electronic voting to encourage interactive lectures: a randomised trial
2007-01-01
Background Electronic Voting Systems have been used for education in a variety of disciplines. Outcomes from these studies have been mixed. Because results from these studies have been mixed, we examined whether an EVS system could enhance a lecture's effect on educational outcomes. Methods A cohort of 127 Year 5 medical students at the University of Adelaide was stratified by gender, residency status and academic record then randomised into 2 groups of 64 and 63 students. Each group received consecutive 40-minute lectures on two clinical topics. One group received the EVS for both topics. The other group received traditional teaching only. Evaluation was undertaken with two, 15-question multiple-choice questionnaires (MCQ) assessing knowledge and problem solving and undertaken as a written paper immediately before and after the lectures and repeated online 8–12 weeks later. Standardised institutional student questionnaires were completed for each lecture and independent observers assessed student behaviour during the lectures. Lecturer's opinions were assessed by a questionnaire developed for this study. Results Two-thirds of students randomised to EVS and 59% of students randomised to traditional lectures attended. One-half of the students in the EVS group and 41% in the traditional group completed all questionnaires. There was no difference in MCQ scores between EVS and traditional lectures (p = 0.785). The cervical cancer lectures showed higher student ranking in favour of EVS in all parameters. The breast cancer lectures showed higher ranking in favour of traditional lectures in 5 of 7 parameters (p < 0.001). The observed higher-order lecturer-students interactions were increased in the EVS lecture for one lecturer and reduced for the other. Both lecturers felt that the EVS lectures were difficult to prepare, that they were able to keep to time in the traditional lectures, that the educational value of both lecture styles was similar, and that they were
Explicit constructivism: a missing link in ineffective lectures?
Prakash, E S
2010-06-01
This study tested the possibility that interactive lectures explicitly based on activating learners' prior knowledge and driven by a series of logical questions might enhance the effectiveness of lectures. A class of 54 students doing the respiratory system course in the second year of the Bachelor of Medicine and Bachelor of Surgery program in my university was randomized to two groups to receive one of two types of lectures, "typical" lectures (n = 28, 18 women and 10 men) or "constructivist" lectures (n = 26, 19 women and 7 men), on the same topic: the regulation of respiration. Student pretest scores in the two groups were comparable (P > 0.1). Students that received the constructivist lectures did much better in the posttest conducted immediately after the lectures (6.8 +/- 3.4 for constructivist lectures vs. 4.2 +/- 2.3 for typical lectures, means +/- SD, P = 0.004). Although both types of lectures were well received, students that received the constructivist lectures appeared to have been more satisfied with their learning experience. However, on a posttest conducted 4 mo later, scores obtained by students in the two groups were not any different (6.9 +/- 3 for constructivist lectures vs. 6.9 +/- 3.7 for typical lectures, P = 0.94). This study adds to the increasing body of evidence that there is a case for the use of interactive lectures that make the construction of knowledge and understanding explicit, easy, and enjoyable to learners. PMID:20522904
2D warp-and-woof interwoven networks constructed by helical chains with different chirality.
Feng, Yuhua; Guo, Yang; OuYang, Yan; Liu, Zhanquan; Liao, Daizheng; Cheng, Peng; Yan, Shiping; Jiang, Zonghui
2007-09-21
Two unprecedented 2D entangled layers of warp-and-woof threads interwoven by left- and right-handed helical chains, {[Mn(salen)Au(CN)2]4(H2O)}n (salen = N,N'-ethylenebis(salicylideneaminato)) and {Mn(acacen)Ag(CN)2}n (acacen = N,N'-ethylenebis(acetylacetonylideneiminate)) 2, have been synthesized and characterized. PMID:17728880
NASA Astrophysics Data System (ADS)
Cofie, Emmanuel
1993-04-01
A finite element stiffness matrix technique for analyzing thin-walled open isotropic sections subjected to torsional loading is considered in this paper. Such beam sections are widely used for structural components and stiffeners in aerospace and civil engineering applications. The torsional stiffness term in a stiffness matrix for a 12 degree-of-freedom (d.o.f.) beam element called a 'warping superelement' is developed using the differential equation derived by Vlasov. This stiffness matrix term which implicitly includes the effects of warping, is used in the region of the beam where warping is considered critical. The length of this region, which determines the length of the superelement, depends on the geometrical and mechanical properties of the section. Elements outside of this region are considered as conventional Euler-Bernoulli beam elements (with St. Venant torsion). Numerical examples of several thin-walled beams with different torsional restraints are presented. Results obtained using the proposed superelement procedure are compared with theoretical results based on Vlasov, St. Venant, and 2-D finite element analysis. The results indicate good agreement with the Vlasov, and 2-D finite element analysis results, which account for warping.
Effect of perturbative hexagonal warping on quantum capacitance in ultra-thin topological insulators
NASA Astrophysics Data System (ADS)
Menon, Anirudha; Chowdhury, Debashree; Basu, Banasri
2016-04-01
Ultra-thin 3D topological insulators provide a stage to study the surface physics of such materials by minimizing the bulk contribution. Further, the experimentally verified snowflake like structure of the Fermi surface leads to a hexagonal warping term, and this shows it to be a perturbation in the presence of a magnetic field. We find that there are corrections to both energy dispersion and eigenstates which in turn alter the density of states in the presence of a magnetic field. Both the quantum capacitance and the Hall coefficient are evaluated analytically and it is shown here that we recover their established forms along with small corrections which preserve the object of treating hexagonal warping perturbatively. In our approach, the established Hall conductivity expression develops several minute correction terms and thus its behavior remains largely unaffected due to warping. The zero-temperature quantum capacitance exhibits Shubnikov-de Haas oscillations with reduced frequencies, with a lowered average capacitance with increased warping of the Fermi surface, while maintaining the usual amplitudes.
Koh, Yeong Jun; Lee, Chulwoo; Kim, Chang-Su
2015-12-01
We propose a video stabilization algorithm, which extracts a guaranteed number of reliable feature trajectories for robust mesh grid warping. We first estimate feature trajectories through a video sequence and transform the feature positions into rolling-free smoothed positions. When the number of the estimated trajectories is insufficient, we generate virtual trajectories by augmenting incomplete trajectories using a low-rank matrix completion scheme. Next, we detect feature points on a large moving object and exclude them so as to stabilize camera movements, rather than object movements. With the selected feature points, we set a mesh grid on each frame and warp each grid cell by moving the original feature positions to the smoothed ones. For robust warping, we formulate a cost function based on the reliability weights of each feature point and each grid cell. The cost function consists of a data term, a structure-preserving term, and a regularization term. By minimizing the cost function, we determine the robust mesh grid warping and achieve the stabilization. Experimental results demonstrate that the proposed algorithm reconstructs videos more stably than the conventional algorithms. PMID:26394425
NASA Technical Reports Server (NTRS)
Springer, P.
1993-01-01
This paper discusses the method in which the Cascade-Correlation algorithm was parallelized in such a way that it could be run using the Time Warp Operating System (TWOS). TWOS is a special purpose operating system designed to run parellel discrete event simulations with maximum efficiency on parallel or distributed computers.
Characterizing the Galactic warp with Gaia - I. The tilted ring model with a twist
NASA Astrophysics Data System (ADS)
Abedi, Hoda; Mateu, Cecilia; Aguilar, Luis A.; Figueras, Francesca; Romero-Gómez, Mercè
2014-08-01
We explore the possibility of detecting and characterizing the warp of the stellar disc of our Galaxy using synthetic Gaia data. The availability of proper motions and, for the brightest stars radial velocities, adds a new dimension to this study. A family of Great Circle Cell Counts methods is used. They are ideally suited to find the tilt and twist of a collection of rings, which allow us to detect and measure the warp parameters. To test them, we use random realizations of test particles which evolve in a realistic Galactic potential warped adiabatically to various final configurations. In some cases a twist is introduced additionally. The Gaia selection function, its errors model and a realistic 3D extinction map are applied to mimic three tracer populations: OB, A and red clump stars. We show how the use of kinematics improves the accuracy in the recovery of the warp parameters. The OB stars are demonstrated to be the best tracers determining the tilt angle with accuracy better than ˜0.5 up to Galactocentric distance of ˜16 kpc. Using data with good astrometric quality, the same accuracy is obtained for A-type stars up to ˜13 kpc and for red clump up to the expected stellar cut-off. Using OB stars the twist angle is recovered to within <3° for all distances.
The Web-Lecture - a viable alternative to the traditional lecture format?
NASA Astrophysics Data System (ADS)
Meibom, S.
2004-12-01
Educational research shows that students learn best in an environment with emphasis on teamwork, problem-solving, and hands-on experience. Still professors spend the majority of their time with students in the traditional lecture-hall setting where the combination of large classes and limited time prevents sufficient student-teacher interaction to foster an active learning environment. Can modern computer technology be used to provide "lecture-type" information to students via the World Wide Web? If so, will that help professors make better and/or different use of their scheduled time with the students? Answering these questions was the main motivation for the Extra-Solar Planet Project. The Extra-Solar Planet Project was designed to test the effectiveness of a lecture available to the student on the World Wide Web (Web-Lecture) and to engage the students in an active learning environment were their use the information presented in the Web-Lecture. The topic of the Web-Lecture was detection of extra-solar planets and the project was implemented into an introductory astronomy course at University of Wisconsin Madison in the spring of 2004. The Web-Lecture was designed to give an interactive presentation of synchronized video, audio and lecture notes. It was created using the eTEACH software developed at the University of Wisconsin Madison School of Engineering. In my talk, I will describe the project, show excerpts of the Web-Lecture, and present assessments of student learning and results of student evaluations of the web-lecture format.
Interactive lectures: Clickers or personal devices?
Morrell, Lesley J; Joyce, Domino A
2015-01-01
Audience response systems ('clickers') are frequently used to promote participation in large lecture classes, and evidence suggests that they convey a number of benefits to students, including improved academic performance and student satisfaction. The limitations of these systems (such as limited access and cost) can be overcome using students' personal electronic devices, such as mobile phones, tablets and laptops together with text message, web- or app-based polling systems. Using questionnaires, we compare student perceptions of clicker and smartphone based polling systems. We find that students prefer interactive lectures generally, but those that used their own device preferred those lectures over lectures using clickers. However, device users were more likely to report using their devices for other purposes (checking email, social media etc.) when they were available to answer polling questions. These students did not feel that this distracted them from the lecture, instead, concerns over the use of smartphones centred around increased battery usage and inclusivity for students without access to suitable technology. Our results suggest that students generally preferred to use their own devices over clickers, and that this may be a sensible way to overcome some of the limitations associated with clickers, although issues surrounding levels of distraction and the implications for retention and recall of information need further investigation. PMID:26594327
Interactive lectures: Clickers or personal devices?
Morrell, Lesley J.; Joyce, Domino A.
2015-01-01
Audience response systems (‘clickers’) are frequently used to promote participation in large lecture classes, and evidence suggests that they convey a number of benefits to students, including improved academic performance and student satisfaction. The limitations of these systems (such as limited access and cost) can be overcome using students’ personal electronic devices, such as mobile phones, tablets and laptops together with text message, web- or app-based polling systems. Using questionnaires, we compare student perceptions of clicker and smartphone based polling systems. We find that students prefer interactive lectures generally, but those that used their own device preferred those lectures over lectures using clickers. However, device users were more likely to report using their devices for other purposes (checking email, social media etc.) when they were available to answer polling questions. These students did not feel that this distracted them from the lecture, instead, concerns over the use of smartphones centred around increased battery usage and inclusivity for students without access to suitable technology. Our results suggest that students generally preferred to use their own devices over clickers, and that this may be a sensible way to overcome some of the limitations associated with clickers, although issues surrounding levels of distraction and the implications for retention and recall of information need further investigation. PMID:26594327
Li, Zhi-Yun; Zhao, Bo; Krasnopolsky, Ruben; Shang, Hsien
2014-10-01
The formation of rotationally supported protostellar disks is suppressed in ideal MHD in non-turbulent cores with aligned magnetic fields and rotation axes. A promising way to resolve this so-called 'magnetic braking catastrophe' is through turbulence. The reason for the turbulence-enabled disk formation is usually attributed to the turbulence-induced magnetic reconnection, which is thought to reduce the magnetic flux accumulated in the disk-forming region. We advance an alternative interpretation, based on magnetic decoupling-triggered reconnection of severely pinched field lines close to the central protostar and turbulence-induced warping of the pseudodisk of Galli and Shu. Such reconnection weakens the central split magnetic monopole that lies at the heart of the magnetic braking catastrophe under flux freezing. We show, through idealized numerical experiments, that the pseudodisk can be strongly warped, but not completely destroyed, by a subsonic or sonic turbulence. The warping decreases the rates of angular momentum removal from the pseudodisk by both magnetic torque and outflow, making it easier to form a rotationally supported disk. More importantly, the warping of the pseudodisk out of the disk-forming, equatorial plane greatly reduces the amount of magnetic flux threading the circumstellar, disk-forming region, further promoting disk formation. The beneficial effects of pseudodisk warping can also be achieved by a misalignment between the magnetic field and rotation axis. These two mechanisms of disk formation, enabled by turbulence and field-rotation misalignment respectively, are thus unified. We find that the disks formed in turbulent magnetized cores are rather thick and significantly magnetized. Implications of these findings, particularly for the thick young disk inferred in L1527, are briefly discussed.
NASA Astrophysics Data System (ADS)
Li, Zhi-Yun; Krasnopolsky, Ruben; Shang, Hsien; Zhao, Bo
2014-10-01
The formation of rotationally supported protostellar disks is suppressed in ideal MHD in non-turbulent cores with aligned magnetic fields and rotation axes. A promising way to resolve this so-called "magnetic braking catastrophe" is through turbulence. The reason for the turbulence-enabled disk formation is usually attributed to the turbulence-induced magnetic reconnection, which is thought to reduce the magnetic flux accumulated in the disk-forming region. We advance an alternative interpretation, based on magnetic decoupling-triggered reconnection of severely pinched field lines close to the central protostar and turbulence-induced warping of the pseudodisk of Galli and Shu. Such reconnection weakens the central split magnetic monopole that lies at the heart of the magnetic braking catastrophe under flux freezing. We show, through idealized numerical experiments, that the pseudodisk can be strongly warped, but not completely destroyed, by a subsonic or sonic turbulence. The warping decreases the rates of angular momentum removal from the pseudodisk by both magnetic torque and outflow, making it easier to form a rotationally supported disk. More importantly, the warping of the pseudodisk out of the disk-forming, equatorial plane greatly reduces the amount of magnetic flux threading the circumstellar, disk-forming region, further promoting disk formation. The beneficial effects of pseudodisk warping can also be achieved by a misalignment between the magnetic field and rotation axis. These two mechanisms of disk formation, enabled by turbulence and field-rotation misalignment respectively, are thus unified. We find that the disks formed in turbulent magnetized cores are rather thick and significantly magnetized. Implications of these findings, particularly for the thick young disk inferred in L1527, are briefly discussed.
Application of Out-of-Plane Warping to Control Rotor Blade Twist
NASA Technical Reports Server (NTRS)
VanWeddingen, Yannick; Bauchau, Olivier; Kottapalli, Sesi; Ozbay, Serkan; Mehrotra, Yogesh
2012-01-01
The goal of this ongoing study is to develop and demonstrate the feasibility of a blade actuation system to dynamically change the twist, and/or the camber, of an airfoil section and, consequently, alter the in-flight aerodynamic loading on the blade for efficient flight control. The required analytical and finite element tools are under development to enable an accurate and comprehensive aeroelastic assessment of the current Full-Blade Warping and 3D Warping Actuated Trailing Edge Flap concepts. The feasibility of the current concepts for swashplateless rotors and higher harmonic blade control is also being investigated. In particular, the aim is to complete the following objectives, some of which have been completed (as noted below) and others that are currently ongoing: i) Develop a Vlasov finite element model and validate against the ABAQUS shell models (completed). ii) Implement the 3D warping actuation concept within the comprehensive analysis code DYMORE. iii) Perform preliminary aeroelastic simulations of blades using DYMORE with 3D warping actuation: a) Investigate the blade behavior under 1 per/rev actuation. Determine whether sufficient twist can be generated and sustained to achieve primary blade control. b) Investigate the behavior of a trailing edge flap configuration under higher harmonic excitations. Determine how much twist can be obtained at the harmonics 2-5 per/rev. iv) Determine actuator specifications such as the power required, load and displacements, and identify the stress and strain distributions in the actuated blades. In general, the completion of Item ii) above will give an additional research capability in rotorcraft dynamics analyses, i.e., the capability to calculate the rotor blade twist due to warping, something that is not currently available in any of the existing comprehensive rotorcraft analyses.
The newly-found Rheticus lectures.
NASA Astrophysics Data System (ADS)
Kraai, J.
This article discusses a hitherto unknown set of lectures presumably given by Georg Joachim Rheticus, and taken down by several students in Wittenberg. These lectures offer considerable insight into Rheticus' teaching activities shortly before the publication of De Revolutionibus (1543). The most salient aspects of this newly-found text may be summarized as follows: a) Rheticus was known among the students in Wittenberg as Joachimus Heliopolitanus, i.e. Joachim of the City of the Sun - a clear reference to Rheticus' stay in Frauenburg with Copernicus, b) Rheticus returned from his stay with Copernicus to Wittenberg for a short period of time in 1540 to fulfill his professorial obligations, and c) we have 155 folio pages which document Rheticus' introductory lectures on astronomy.
Quasinormal modes of self-dual warped AdS3 black hole in topological massive gravity
NASA Astrophysics Data System (ADS)
Li, Ran; Ren, Ji-Rong
2011-03-01
We consider the scalar, vector and spinor field perturbations in the background of self-dual warped AdS3 black hole of topological massive gravity. The corresponding exact expressions for quasinormal modes are obtained by analytically solving the perturbation equations and imposing the vanishing Dirichlet boundary condition at asymptotic infinity. It is expected that the quasinormal modes agree with the poles of retarded Green’s functions of the CFT dual to self-dual warped AdS3 black hole. Our results provide a quantitative test of the warped AdS/CFT correspondence.
Vay, J.-L.; Furman, M.A.; Azevedo, A.W.; Cohen, R.H.; Friedman, A.; Grote, D.P.; Stoltz, P.H.
2004-04-19
We have integrated the electron-cloud code POSINST [1] with WARP [2]--a 3-D parallel Particle-In-Cell accelerator code developed for Heavy Ion Inertial Fusion--so that the two can interoperate. Both codes are run in the same process, communicate through a Python interpreter (already used in WARP), and share certain key arrays (so far, particle positions and velocities). Currently, POSINST provides primary and secondary sources of electrons, beam bunch kicks, a particle mover, and diagnostics. WARP provides the field solvers and diagnostics. Secondary emission routines are provided by the Tech-X package CMEE.
On performing concepts during science lectures
NASA Astrophysics Data System (ADS)
Pozzer-Ardenghi, Lilian; Roth, Wolff-Michael
2007-01-01
When lecturing, teachers make use of both verbal and nonverbal communication. What is called teaching, therefore, involves not only the words and sentences a teacher utters and writes on the board during a lesson, but also all the hands/arms gestures, body movements, and facial expressions a teacher performs in the classroom. All of these communicative modalities constitute resources that are made available to students for making sense of and learning from lectures. Yet in the literature on teaching science, these other means of communication are little investigated and understood - and, correspondingly, they are undertheorized. The purpose of this position paper is to argue for a different view of concepts in lectures: they are performed simultaneously drawing on and producing multiple resources that are different expressions of the same holistic meaning unit. To support our point, we provide examples from a database of 26 lectures in a 12th-grade biology class, where the human body was the main topic of study. We analyze how different types of resources - including verbal and nonverbal discourse and various material artifacts - interact during lectures. We provide evidence for the unified production of these various sense-making resources during teaching to constitute a meaning unit, and we emphasize particularly the use of gestures and body orientations inside this meaning unit. We suggest that proper analyses of meaning units need to take into account not only language and diagrams but also a lecturer's pointing and depicting gestures, body positions, and the relationships between these different modalities. Scientific knowledge (conceptions) exists in the concurrent display of all sense-making resources, which we, following Vygotsky, understand as forming a unit (identity) of nonidentical entities.
Intrinsic deficiencies of lectures as a teaching method.
Pale, Predrag
2013-06-01
Lectures were, still are and seem to remain a dominant form of teaching, despite an increased research and use of other methods of teaching and leverage of technology aimed at improving teaching results and efficiency. Learning, as the result of a lecture, greatly depends on the subject, the competence and abilities of the lecturer as well as on other transient causes. However, lectures also have some intrinsic deficiencies as a teaching method pertinent to their very nature. In order to fully understand the teaching value of lectures and their role and proper use in educational systems, their deficiencies have been studied in a theoretical analysis from the perspective of cognitive learning theories. Fifteen deficiencies have been identified and clustered in three categories based on root causes of deficiencies: synchronicity problems, time constraint and individual student abilities, needs and knowledge. These findings can be used to adjust expected learning outcomes of lectures, to properly (re)design lecture content and process and to design other learning and teaching activities that would compensate and complement lectures. Recommendations are given on replacing and amending lectures with other instructional methods, amending lectures in the course of delivery with additional content and tools and complementing lectures after delivery with content, tools and activities. Suggestions on the use of information technology that could substitute, reduce or eliminate at least some of the deficiencies are made. Lecture captures seem to be valuable supplement for live lectures compensating in all three categories of deficiencies. Suggestions and directions for further research are given. PMID:23941004
Revitalizing Ernst Mach's Popular Scientific Lectures
NASA Astrophysics Data System (ADS)
Euler, Manfred
2007-06-01
Compared to Ernst Mach's influence on the conceptual development of physics, his efforts to popularize science and his reflections on science literacy are known to a much lesser degree. The approach and the impact of Mach's popular scientific lectures are discussed in view of today's problems of understanding science. The key issues of Mach's popular scientific lectures, reconsidered in the light of contemporary science, still hold a high potential in fascinating a general audience. Moreover, Mach's grand theme, the relation of the physical to the psychical, is suited to contribute to a dialogue between different knowledge cultures, e.g. science and humanities.
The McAndrews Leadership Lecture: Origins
Hamm, Anthony W.; Burkhart, Lori A.
2015-01-01
Objective This article describes the origins and rationale for the McAndrews Leadership Lecture and explains why the American Chiropractic Association honors George and Jerome McAndrews. Discussion George and Jerome McAndrews’ backgrounds demonstrate their leadership contributions to the chiropractic profession. Jerome McAndrews, a chiropractor, held substantial leadership roles in the chiropractic profession. George McAndrews, a lawyer, administered a permanent injunction forbidding the American Medical Association’s restraint of trade toward the chiropractic profession. Conclusion The American Chiropractic Association has established the McAndrews Leadership Lecture to honor their contributions to the chiropractic profession. PMID:26770176
NASA Astrophysics Data System (ADS)
Kapon, S.; Ganiel, U.; Eylon, B.
2009-09-01
Many large scientific projects and scientific centres incorporate some kind of outreach programme. Almost all of these outreach programmes include public scientific lectures delivered by practising scientists. In this article, we examine such lectures from the perspectives of: (i) lecturers (7) who are practising scientists acknowledged to be good public lecturers and (ii) audiences composed of high-school students (169) and high-school physics teachers (80) who attended these lectures. We identify and discuss the main goals as expressed by the lecturers and the audiences, and the correspondence between these goals. We also discuss how the lecturers' goals impact on the design of their lectures and examine how the lecture affects audiences with different attitudes towards (and interests in) physics. Our findings suggest that the goals of the participating lecturers and the expectations of their audiences were highly congruent. Both believe that a good public scientific lecture must successfully communicate state-of-the-art scientific knowledge to the public, while inspiring interest in and appreciation of science. Our findings also suggest that exemplary public scientific lectures incorporate content, structure and explanatory means that explicitly adhere to the lecturers' goals. We identify and list several design principles.
ERIC Educational Resources Information Center
Gray, Howard R., Comp.; And Others
The following lectures are presented in this publication: (1) "The Dynamics of Recreation" (Betty Van der Smissen); (2) "Recreation Prospects" (Edith L. Ball); (3) "A View of the Past--A Bridge to the Future" (Allen V. Sapora); (4) "Coming to Grips with the New Leisure" (Richard G. Kraus); (5) "The Mild Blue Yonder--Changing Lifestyles and…
Short and Sweet: Technology Shrinks the Lecture
ERIC Educational Resources Information Center
Young, Jeffrey R.
2008-01-01
Many professors who have ventured into online education are finding that shorter, modular clips are a more successful teaching approach than traditional 50-minute lectures. The author cites educators from several institutions who have adapted smaller, 15-20 minute instructional units originally developed for online courses, to their face-to-face…
Movement and Character. Lecture, London, 1946
ERIC Educational Resources Information Center
Montesorri, Maria
2013-01-01
Dr. Montessori's words from the 1946 London Lectures describe principles of intelligence and character, the work of the hand, and movement with a purpose as being integral to self-construction. The perfection of movement is spiritual, says Dr. Montessori. Repetition of practical life exercises are exercises in movement with the dignity of human…
Teaching Introductory Astronomy Using Lecture-Tutorials
NASA Astrophysics Data System (ADS)
Adams, Jeffrey P.; Bailey, Janelle M.; Prather, Edward E.; Slater, Timothy F.
Contemporary science education reforms suggest that teacher-centered lectures are ineffective when compared to student-centered active learning approaches. Funded by the U.S. National Science Foundation this project has developed a series of innovative classroom instructional materials for the introductory science survey course for non-science and pre-service education majors as well as secondary school astronomy courses. The materials package called Lecture-Tutorials for Introductory Astronomy is a self-contained classroom-ready product for use with collaborative student learning groups. The materials are designed specifically to be easily integrated into the conventional lecture course. As such this product directly addresses the needs of busy faculty and heavily-loaded teaching faculty for effective student-centered classroom-ready materials that do not require a drastic course revision for implementation. Each activity requires no equipment and takes 10 to 15 minutes of class time. Students are asked to reason about difficult concepts in astronomy while working in pairs and to discuss their ideas openly. The 30 Lecture-Tutorials for Introductory Astronomy are based upon educational research on student misconceptions demonstrated effective instructional strategies and extensive pilot and field-testing. Funding for the project was made available by NSF CCLI #9952232 and NSF Geosciences Education #9907755.
Physics Meets Biology (LBNL Summer Lecture Series)
Chu, Steve
2006-07-01
Summer Lecture Series 2006: If scientists could take advantage of the awesomely complex and beautiful functioning of biologys natural molecular machines, their potential for application in many disciplines would be incalculable. Nobel Laureate and Director of the Lawrence Berkeley National Laboratory Steve Chu explores Possible solutions to global warming and its consequences.
Decorum in the Large Lecture Class
ERIC Educational Resources Information Center
Druger, Marvin
2008-01-01
Anyone who has taught a lecture to a large group of students has probably experienced undesirable student behaviors. The author, who has taught an introductory college biology course at Syracuse University for 45 years, relates that an important part of his teaching philosophy is that everyone should learn from everything that they do, and…
Using Tablet Technology for University Lectures
ERIC Educational Resources Information Center
Chester, Victoria
2008-01-01
Tablet PCs provide numerous benefits over traditional electronically projected lectures that use software such as PowerPoint. Flexibility and spontaneity can be achieved by editing or creating notes in real-time. The input pen or stylus is a very useful tool, especially for courses that involve the extensive use of equations or mathematical…
Music during Lectures: Will Students Learn Better?
ERIC Educational Resources Information Center
Dosseville, Fabrice; Laborde, Sylvain; Scelles, Nicolas
2012-01-01
We investigated the influence of music during learning on the academic performance of undergraduate students, and more particularly the influence of affects induced by music. Altogether 249 students were involved in the study, divided into a control group and an experimental group. Both groups attended the same videotaped lecture, with the…
Knowledge, Power, and Freud's Clark Conference Lectures.
ERIC Educational Resources Information Center
Cooper, Martha; Makay, John J.
1988-01-01
Examines Freud's Clark Conference Lectures in which he offers a case in point of the intersection among knowledge, power, and discourse. Argues that Freud's rhetorical action constituted the "new" knowledge of psychoanalysis, while simultaneously forging relationships between the scientific and medical communities that endowed the psychoanalyst…
How Lecturers See Their Teaching Objectives.
ERIC Educational Resources Information Center
de Winter Hebron, C. C.
The results of a project to determine how English polytechnic lecturers see their teaching objectives are presented. Development of a behaviorally referenced student feedback questionnaire and the theory behind behavioral referencing are described. The definitions of teaching and learning are explored and the relationship between teaching and…
Lecturing Style Teaching and Student Performance
ERIC Educational Resources Information Center
Van Klaveren, Chris
2011-01-01
Teachers in the Netherlands tend to spend less time in front of the class, and often adopt a more personal approach. This allows them to better adjust their lecturing style to the needs of the individual student with the aim of increasing student performance. However, a more personal approach is also more time consuming and potentially reduces the…
Creativity and the Curriculum. Inaugural Professorial Lecture
ERIC Educational Resources Information Center
Wyse, Dominic
2014-01-01
Creativity is regarded by many as a vital aspect of the human world, and creative endeavours are seen as a central element of society. Hence student creativity is regarded as a desirable outcome of education. This inaugural professorial lecture examines the place of creativity in education and in national curricula. Beginning with examples of…
Lecture vs. Laboratory Instruction in Agricultural Mechanics.
ERIC Educational Resources Information Center
Oomes, Fred W.; Jurshak, Steve
1978-01-01
The effects of lecture versus laboratory method of teaching on the achievement of forty-six students enrolled in a unit on soil and water management (surveying) were studied. Results indicated no significant differences between groups as measured by cognitive and motor skill tests. (JH)
The Sessional Lecturer as Migrant Labourer.
ERIC Educational Resources Information Center
Mysyk, Avis
2001-01-01
Based on personal ethnographic experience of "becoming the phenomenon" of migrant laborer in Canada's postsecondary education system, critically examines three anthropological perspectives--the neoclassical, the historical structuralist, and the neo-Marxist--on labor migration. Argues that both migrant laborers and sessional lecturers have become…
Lecturers' Views on Ghana's Undergraduate Mathematics Education
ERIC Educational Resources Information Center
Assuah, Charles; Ayebo, Abraham
2015-01-01
This paper synthesizes the views of 6 university lecturers on Ghana's undergraduate mathematics education. These views were expressed during a mathematics workshop sensitization program on the "contribution of undergraduate mathematics education to the Ghanaian economy." The data consisting of open-ended questions followed by…
Mathematics Lecturing in the Digital Age
ERIC Educational Resources Information Center
Trenholm, Sven; Alcock, Lara; Robinson, Carol L.
2012-01-01
In this article, we consider the transformation of tertiary mathematics lecture practice. We undertake a focused examination of the related research with two goals in mind. First, we document this research, reviewing the findings of key studies and noting that reflective pieces on individual practice as well as surveys are more prevalent than…
The Colloqution Module: Remedy for Somnifacient Lectures.
ERIC Educational Resources Information Center
Pultorak, Robert W.
1985-01-01
A "colloqution module" (an instructional unit/strategy used in a conversation) consists of a reading assignment and a series of questions/activities. The strategy is suggested as an alternative to the lecture method. A sample module on insecticides (together with design information and advantages/disadvantages) is included. (DH)
On Performing Concepts during Science Lectures
ERIC Educational Resources Information Center
Pozzer-Ardenghi, Lilian; Roth, Wolff-Michael
2007-01-01
When lecturing, teachers make use of both verbal and nonverbal communication. What is called teaching, therefore, involves not only the words and sentences a teacher utters and writes on the board during a lesson, but also all the hands/arms gestures, body movements, and facial expressions a teacher "performs" in the classroom. All of these…
Physics Meets Biology (LBNL Summer Lecture Series)
Chu, Steve [Director, LBNL
2011-04-28
Summer Lecture Series 2006: If scientists could take advantage of the awesomely complex and beautiful functioning of biologys natural molecular machines, their potential for application in many disciplines would be incalculable. Nobel Laureate and Director of the Lawrence Berkeley National Laboratory Steve Chu explores Possible solutions to global warming and its consequences.
Movement and Learning in Lecture Classrooms
ERIC Educational Resources Information Center
Patterson, Michala Paige
2011-01-01
This mixed methods research utilized Action Based Learning Theory on a population of undergraduate college-aged students to determine if movement breaks in a predominately lecture-style college class affected a student's ability to demonstrate learning. Four professors from various disciplines, each teaching two sections of the same…
Enabling a Comprehensive Teaching Strategy: Video Lectures
ERIC Educational Resources Information Center
Brecht, H. David; Ogilby, Suzanne M.
2008-01-01
This study empirically tests the feasibility and effectiveness of video lectures as a form of video instruction that enables a comprehensive teaching strategy used throughout a traditional classroom course. It examines student use patterns and the videos' effects on student learning, using qualitative and nonparametric statistical analyses of…
Lecture on Female Masturbation Harassed Him, Male Student Says.
ERIC Educational Resources Information Center
Wilson, Robin
1995-01-01
A male student in a California State University-Sacramento psychology lecture on female masturbation has filed a sexual harassment complaint, claiming the lecture violated institutional policy by creating an intimidating, hostile, and offensive learning environment. He felt the lecture was inappropriately graphic and political in intent. (MSE)
Lecture Capture in Engineering Classes: Bridging Gaps and Enhancing Learning
ERIC Educational Resources Information Center
Al Nashash, Hasan; Gunn, Cindy
2013-01-01
This paper explores the use of lecture capture in Engineering classes to provide students with the opportunity to enhance their understanding of the course content. Students were asked to provide feedback on what they perceive the benefits and the drawbacks of lecture capture to be. The results show that the students consider lecture capture an…
Lecturing: Omitted or Overlooked? Some Options for a New Orientation.
ERIC Educational Resources Information Center
Weaver, Richard L., II; Michel, Thomas A.
No teaching method is more widely used and yet more strongly criticized than the lecture. Yet, an examination of more than 40 basic public speaking textbooks reveals that lecturing is seldom mentioned. There are, perhaps, several reasons for this omission. For example, authors of textbooks might feel that (1) material on lecturing duplicates their…
The "Work" of Lecturing in High School Chemistry
ERIC Educational Resources Information Center
Hwang, SungWon; Roth, Wolff-Michael
2013-01-01
Lecturing is an important aspect of the culture of science education. Perhaps because of the negative associations constructivist educators make with lecturing, little research has been done concerning the generally invisible aspects of the (embodied, lived) "work" that is required. Traditional research on science lectures focuses on…
Taxonomy of Lecture Note-Taking Skills and Subskills
ERIC Educational Resources Information Center
Al-Musalli, Alaa M.
2015-01-01
Note taking (NT) in lectures is as active a skill as listening, which stimulates it, and as challenging as writing, which is the end product. Literature on lecture NT misses an integration of the processes involved in listening with those in NT. In this article, a taxonomy is proposed of lecture NT skills and subskills based on a similar list…
Learning with E-Lectures: The Meaning of Learning Strategies
ERIC Educational Resources Information Center
Jadin, Tanja; Gruber, Astrid; Batinic, Bernad
2009-01-01
Video-based e-lectures offer interactive learning and more vivid and personalized forms of self-regulated learning. Participants (N = 28) learned from either a video-based e-lecture with synchronized written transcript of oral presentation (multimodal) or an e-lecture without the transcript (unimodal presentation). Learners could be classified as…
Student Use of Mobile Devices in University Lectures
ERIC Educational Resources Information Center
Roberts, Neil; Rees, Michael
2014-01-01
Mobile devices are increasingly used by students in university lectures. This has resulted in controversy and the banning of mobile devices in some lectures. Although there has been some research into how students use laptop computers in lectures, there has been little investigation into the wider use of mobile devices. This study was designed to…
Lecturers' Experience of Using Social Media in Higher Education Courses
ERIC Educational Resources Information Center
Seechaliao, Thapanee
2015-01-01
This research paper presents lecturers' experience of using social media in higher education courses. The research methodology used a survey approach. The research instrument was a questionnaire about lecturers' experience of using social media in higher education courses. Thirty-one lecturers completed the questionnaire. The data were scored by…
The Lecture as a Transmedial Pedagogical Form: A Historical Analysis
ERIC Educational Resources Information Center
Friesen, Norm
2011-01-01
The lecture has been much maligned as a pedagogical form, yet it persists and even flourishes today in the form of the podcast, the TED talk, and the "smart" lecture hall. This article examines the lecture as a pedagogical genre, as "a site where differences between media are negotiated" (Franzel) as these media coevolve. This examination shows…
Mathematics Lectures as Narratives: Insights from Network Graph Methodology
ERIC Educational Resources Information Center
Weinberg, Aaron; Wiesner, Emilie; Fukawa-Connelly, Tim
2016-01-01
Although lecture is the traditional method of university mathematics instruction, there has been little empirical research that describes the general structure of lectures. In this paper, we adapt ideas from narrative analysis and apply them to an upper-level mathematics lecture. We develop a framework that enables us to conceptualize the lecture…
Annual Advances in Cancer Prevention Lecture | Division of Cancer Prevention
2016 Keynote Lecture Polyvalent Vaccines Targeting Oncogenic Driver Pathways A special keynote lecture became part of the NCI Summer Curriculum in Cancer Prevention in 2000. This lecture will be held on Thursday, July 21, 2016 at 1:30pm at Masur Auditorium, Building 10, NIH Main Campus, Bethesda, MD. This year’s keynote speaker is Dr. Mary L. (Nora) Disis, MD. |
Engagement of Students with Lectures in Biochemistry and Pharmacology
ERIC Educational Resources Information Center
Davis, Elizabeth Ann; Hodgson, Yvonne; Macaulay, Janet Olwyn
2012-01-01
Academic staff at universities have become concerned about the decrease in student attendance at lectures and the implication of this on student achievement and learning. Few studies have measured actual lecture attendance in a coherent or comprehensive way. The aim of this study was to measure actual lecture attendance of students over two year…
Annual Advances in Cancer Prevention Lecture | Division of Cancer Prevention
2015 Keynote Lecture HPV Vaccination: Preventing More with Less A special keynote lecture became part of the NCI summer Curriculum in Cancer Prevention in 2000. This lecture will be held on Thursday, July 23, 2015 at 3:00pm at Masur Auditorium, Building 10, NIH Main Campus, Bethesda, MD. This year’s keynote speaker is Dr. Douglas Lowy, NCI Acting Director. |
Dawson, Rebekah I.; Murray-Clay, Ruth A.; Fabrycky, Daniel C.
2011-12-10
The vertical warp in the debris disk {beta} Pictoris-an inclined inner disk extending into a flat outer disk-has long been interpreted as the signpost of a planet on an inclined orbit. Direct images spanning 2004-2010 have revealed {beta} Pictoris b, a planet with a mass and orbital distance consistent with this picture. However, it was recently reported that the orbit of planet b is aligned with the flat outer disk, not the inclined inner disk, and thus lacks the inclination to warp the disk. We explore three scenarios for reconciling the apparent misalignment of the directly imaged planet {beta} Pictoris b with the warped inner disk of {beta} Pictoris: observational uncertainty, an additional planet, and damping of planet b's inclination. We find that, at the extremes of the uncertainties, the orbit of {beta} Pictoris b has the inclination necessary to produce the observed warp. We also find that if planet b were aligned with the flat outer disk, it would prevent another planet from creating a warp with the observed properties; therefore planet b itself must be responsible for the warp. Finally, planet b's inclination could have been damped by dynamical friction and still produce the observed disk morphology, but the feasibility of damping depends on disk properties and the presence of other planets. More precise observations of the orbit of planet b and the position angle of the outer disk will allow us to distinguish between the first and third scenarios.
Warp of the ionized gas layer in the outer Galaxy, traced by recombination line observations
NASA Astrophysics Data System (ADS)
Azcárate, I. N.; Cersosimo, J. C.
We report results of H166α recombination line observations from the outer Galaxy in both the Northern and Southern Galactic Plane. The Southern observations were made with the 30 m antenna of the Instituto Argentino de Radioastronomía in Villa Elisa, Buenos Aires, Argentina, and the Northern ones ( more sensitive, high quality observations, performed with an ``state of the art'' receiver) with the 43 m antenna of the National Radio Astronomy Observatory, in Green Bank, West Virginia, USA. >From the two sets of observations we obtain evidence of the warp of the low-density ionized gas layer, traced by the H166α emission in the outer Milky Way, towards positive galactic latitudes in the Northern and towards negative latitudes in the Southern Galaxy. The warp of this tracer qualitatively agrees with that of the HI.
Near-infrared imaging polarimetry of LkCa 15: A possible warped inner disk†
NASA Astrophysics Data System (ADS)
Oh, Daehyeon; Hashimoto, Jun; Tamura, Motohide; Wisniewski, John; Akiyama, Eiji; Currie, Thayne; Mayama, Satoshi; Takami, Michihiro; Thalmann, Christian; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph C.; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Henning, Thomas; Hodapp, Klaus W.; Ishii, Miki; Iye, Masanori; Janson, Markus; Kandori, Ryo; Knapp, Gillian R.; Kuzuhara, Masayuki; Kwon, Jungmi; Matsuo, Taro; Mcelwain, Michael W.; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takahashi, Yasuhiro H.; Takato, Naruhisa; Terada, Hiroshi; Turner, Edwin L.; Watanabe, Makoto; Yamada, Toru; Takami, Hideki; Usuda, Tomonori
2016-04-01
We present high-contrast H-band polarized intensity images of the transitional disk around the young solar-like star LkCa 15. By utilizing Subaru/HiCIAO for polarimetric differential imaging, the angular resolution and the inner working angle reach 0{^''.}07 and r = 0{^''.}1, respectively. We obtained a clearly resolved gap (width ≲ 27 au) at ˜48 au from the central star. This gap is consistent with images reported in previous studies. We also confirmed the existence of a bright inner disk with a misaligned position angle of 13° ± 4° with respect to that of the outer disk, i.e., the inner disk is possibly warped. The large gap and the warped inner disk both point to the existence of a multiple planetary system with a mass of ≲ 1 MJup.
Stability of warped AdS3 black holes in topologically massive gravity under scalar perturbations
NASA Astrophysics Data System (ADS)
Ferreira, Hugo R. C.
2013-06-01
We demonstrate that the warped AdS3 black hole solutions of topologically massive gravity are classically stable against massive scalar field perturbations by analyzing the quasinormal and bound state modes of the scalar field. In particular, it is found that although classical superradiance is present it does not give rise to superradiant instabilities. The stability is shown to persist even when the black hole is enclosed by a stationary mirror with Dirichlet boundary conditions. This is a surprising result in view of the similarity between the causal structure of the warped AdS3 black hole and the Kerr spacetime in 3+1 dimensions. This work provides the foundations for the study of quantum field theory in this spacetime.
Report Initial Work on Developing Plasma Modeling Capability in WARP for NDCX Experiments
Friedman, A; Cohen, R H; Grote, D P; Vay, J
2007-12-14
This milestone has been accomplished. The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) has developed and implemented an initial beam-in-plasma implicit modeling capability in Warp; has carried out tests validating the behavior of the models employed; has compared the results of electrostatic and electromagnetic models when applied to beam expansion in an NDCX-I relevant regime; has compared Warp and LSP results on a problem relevant to NDCX-I; has modeled wave excitation by a rigid beam propagating through plasma; and has implemented and begun testing a more advanced implicit method that correctly captures electron drift motion even when timesteps too large to resolve the electron gyro-period are employed. The HIFS-VNL is well on its way toward having a state-of-the-art source-to-target simulation capability that will enable more effective support of ongoing experiments in the NDCX series and allow more confident planning for future ones.
WARP-10; A numerical simulation model for the cylindrical reconnection launcher
Widner, M.M. )
1991-01-01
In this paper a fully self-consistent computer simulation code called WARP-10, used for modelling the Reconnection Launcher, is described. WARP-10 has been compared with various experiments with good agreement for performance and heating. Simulations predict that it is possible to obtain nearly uniform acceleration with high efficiency and low armature heating. There does not appear to be an armature heating limit to velocity provided the armature mass can be sufficiently large. Simulation results are presented which show it is possible to obtain conditions needed for Earth-to-Orbit (ETO) launch applications (4.15 km/s and a 850 kg launch mass). This 3100-stage launcher has an efficiency of 47.2% and a final ohmic energy/kinetic energy - .00146. The mode of launcher operation is similar to a traveling wave induction launcher and is produced by properly timed and tuned discrete stages. Further optimization and much higher velocities appear possible.
Method and apparatus for sizing and separating warp yarns using acoustical energy
Sheen, Shuh-Haw; Chien, Hual-Te; Raptis, Apostolos C.; Kupperman, David S.
1998-01-01
A slashing process for preparing warp yarns for weaving operations including the steps of sizing and/or desizing the yarns in an acoustic resonance box and separating the yarns with a leasing apparatus comprised of a set of acoustically agitated lease rods. The sizing step includes immersing the yarns in a size solution contained in an acoustic resonance box. Acoustic transducers are positioned against the exterior of the box for generating an acoustic pressure field within the size solution. Ultrasonic waves that result from the acoustic pressure field continuously agitate the size solution to effect greater mixing and more uniform application and penetration of the size onto the yarns. The sized yarns are then separated by passing the warp yarns over and under lease rods. Electroacoustic transducers generate acoustic waves along the longitudinal axis of the lease rods, creating a shearing motion on the surface of the rods for splitting the yarns.
Warped Self-Gravitating U(1) Gauge Cosmic Strings in 5D
NASA Astrophysics Data System (ADS)
Slagter, Reinoud J.
2015-01-01
We present a U(1) gauge cosmic string solution on a warped 5-dimensional space time, where we solved the effective 4-dimensional equations modified by the projection of the Weyl tensor on the brane together with the junction and boundary conditions. Where the mass per unit length of the string in the bulk can be of order of the Planck scale, in the brane it will be warped down to unobservable GUT scale. It turns out that the induced 4-dimensional space time does not show asymptotic conical behavior as in the 4D counterpart model. So there is no angle deficit and the space time seems to be unphysical at finite distance from the core of the string. This could explain the absence of observational evidence of the lensing effect cosmic strings would produce and could have consequences for the (2+1)-dimensional related models.
Method and apparatus for sizing and separating warp yarns using acoustical energy
Sheen, S.H.; Chien, H.T.; Raptis, A.C.; Kupperman, D.S.
1998-05-19
A slashing process is disclosed for preparing warp yarns for weaving operations including the steps of sizing and/or desizing the yarns in an acoustic resonance box and separating the yarns with a leasing apparatus comprised of a set of acoustically agitated lease rods. The sizing step includes immersing the yarns in a size solution contained in an acoustic resonance box. Acoustic transducers are positioned against the exterior of the box for generating an acoustic pressure field within the size solution. Ultrasonic waves that result from the acoustic pressure field continuously agitate the size solution to effect greater mixing and more uniform application and penetration of the size onto the yarns. The sized yarns are then separated by passing the warp yarns over and under lease rods. Electroacoustic transducers generate acoustic waves along the longitudinal axis of the lease rods, creating a shearing motion on the surface of the rods for splitting the yarns. 2 figs.
ERIC Educational Resources Information Center
Kapon, S.; Ganiel, U.; Eylon, B.
2009-01-01
Many large scientific projects and scientific centres incorporate some kind of outreach programme. Almost all of these outreach programmes include public scientific lectures delivered by practising scientists. In this article, we examine such lectures from the perspectives of: (i) lecturers (7) who are practising scientists acknowledged to be good…
About the automated pattern creation of 3D jacquard double needle bed warp knitted structures
NASA Astrophysics Data System (ADS)
Renkens, W.; Kyosev, Y.
2016-07-01
Three dimensional structures can be produced on jacquard warp knitting machines with double needle bed. This work presents theoretical considerations about the modelling and simulation of these structures. After that a method is described, how to obtain production parameters from the simulation data. The analysis demonstrates, that the automated pattern creation of 3D structures is not always possible and not all mathematical solutions of the problem can be knittable.
NASA Astrophysics Data System (ADS)
Quillen, Alice C.
2016-05-01
Sub-structures such as warps and streams in the vertical distribution of gas and dust can manifest as spiral shaped structures, twists in the velocity field, vertical streaming motions, X-shapes, and quasiperiodic dips in light curves. I will review and contrast physical mechanisms for lifting material out of the mid-plane in galactic and circumstellar disks including instabilities, resonant mechanisms and tidal excitations.
Dirac and scalar particles tunnelling from topological massive warped-AdS3 black hole
NASA Astrophysics Data System (ADS)
Gecim, G.; Sucu, Y.
2015-06-01
We investigate the Dirac and scalar particles tunnelling as a radiation of Warped AdS3 black holes in Topological Massive Gravity. Using Hamilton-Jacobi method, we discuss tunnelling probability and Hawking temperature of the spin-1/2 and spin-0 particles for the black hole. We observe the tunnelling probability and Hawking temperature to be same for the spin-1/2 and spin-0. We show that the tunnelling process may occur, for both Dirac and scalar particles.
BOOK REVIEW: Feynman Lectures on Gravitation
NASA Astrophysics Data System (ADS)
Feynman, Richard P.; Morinigo, Fernando B.; Wagner, William G.
2003-05-01
In the early 1960s Feynman lectured to physics undergraduates and, with the assistance of his colleagues Leighton and Sands, produced the three-volume classic Feynman Lectures in Physics. These lectures were delivered in the mornings. In the afternoons Feynman was giving postgraduate lectures on gravitation. This book is based on notes compiled by two students on that course: Morinigo and Wagner. Their notes were checked and approved by Feynman and were available at Caltech. They have now been edited by Brian Hatfield and made more widely available. The book has a substantial preface by John Preskill and Kip Thorne, and an introduction entitled 'Quantum Gravity' by Brian Hatfield. You should read these before going on to the lectures themselves. Preskill and Thorne identify three categories of potential readers of this book. 1. Those with a postgraduate training in theoretical physics. 2. 'Readers with a solid undergraduate training in physics'. 3. 'Admirers of Feynman who do not have a strong physics background'. The title of the book is perhaps misleading: readers in category 2 who think that this book is an extension of the Feynman Lectures in Physics may be disappointed. It is not: it is a book aimed mainly at those in category 1. If you want to get to grips with gravitation (and general relativity) then you need to read an introductory text first e.g. General Relativity by I R Kenyon (Oxford: Oxford University Press) or A Unified Grand Tour of Theoretical Physics by Ian D Lawrie (Bristol: IoP). But there is no Royal Road. As pointed out in the preface and in the introduction, the book represents Feynman's thinking about gravitation some 40 years ago: the lecture course was part of his attempts to understand the subject himself, and for readers in all three categories it is this that makes the book one of interest: the opportunity to observe how a great physicist attempts to tackle some of the hardest challenges of physics. However, the book was written 40
Robotti, Elisa; Marengo, Emilio; Demartini, Marco
2016-01-01
Hierarchical grid transformation is a powerful hierarchical approach to 2-D map warping, able to model both global and local deformations. The algorithm can be stopped when a desired degree of accuracy in the images alignment is obtained. The deformed image is warped and aligned to the target image using a grid where the number of nodes increases in each step of the algorithm. The numerical optimization of the position of the nodes of the grid can be efficiently solved by genetic algorithms, ensuring the achievement of the optimal position of the nodes with a low computational cost with respect to other methods. Here, the optimization of the position of the nodes is carried out by GENOCOP (genetic algorithm for numerical optimization of constrained problems), refined by the following conjugate gradient optimization step. The modeling of the warped space is then achieved by a spline model where some constraints are introduced in the choice of the nodes that are moved. The whole procedure can be intended as an evolutionary method that models the deformation of the gel map at different levels of detail. PMID:26611415
Strong Field Effects on Emission Line Profiles: Kerr Black Holes and Warped Accretion Disks
NASA Astrophysics Data System (ADS)
Wang, Yan; Li, Xiang-Dong
2012-01-01
If an accretion disk around a black hole is illuminated by hard X-rays from non-thermal coronae, fluorescent iron lines will be emitted from the inner region of the accretion disk. The emission line profiles will show a variety of strong field effects, which may be used as a probe of the spin parameter of the black hole and the structure of the accretion disk. In this paper, we generalize the previous relativistic line profile models by including both the black hole spinning effects and the non-axisymmetries of warped accretion disks. Our results show different features from the conventional calculations for either a flat disk around a Kerr black hole or a warped disk around a Schwarzschild black hole by presenting, at the same time, multiple peaks, rather long red tails, and time variations of line profiles with the precession of the disk. We show disk images as seen by a distant observer, which are distorted by the strong gravity. Although we are primarily concerned with the iron K-shell lines in this paper, the calculation is general and is valid for any emission lines produced from a warped accretion disk around a black hole.
Strong Field Effects On Emission Line Profiles: Kerr Black Holes And Warped Accretion Disks
NASA Astrophysics Data System (ADS)
Wang, Yan; Li, X.
2012-01-01
If an accretion disk around a black hole is illuminated by hard X-rays from non-thermal coronae, fluorescent iron lines will be emitted from the inner region of the accretion disk. The emission line profiles will show a variety of strong field effects, which may be used as a probe of the spin parameter of the black hole and the structure of the accretion disk. In this paper we generalize the previous relativistic line profile models by including both the black hole spinning effects and the non-axisymmetry of warped accretion disks. Our results show different features from the conventional calculations for either a flat disk around a Kerr black hole or a warped disk around a Schwarzschild black hole by presenting, at the same time, multiple peaks, rather long red tails and time variations of line profiles with the precession of the disk. We show disk images as seen by a distant observer, which are distorted by the strong gravity. Although we are primarily concerned with the iron K-shell lines in this paper, the calculation is general and is valid for any emission lines produced from a warped accretion disk around a black hole. This work was supported by the Natural Science Foundation of China (under grant number 10873008), and the National Basic Research Program of China (973 Program 2009CB824800).
STRONG FIELD EFFECTS ON EMISSION LINE PROFILES: KERR BLACK HOLES AND WARPED ACCRETION DISKS
Wang Yan; Li Xiangdong
2012-01-10
If an accretion disk around a black hole is illuminated by hard X-rays from non-thermal coronae, fluorescent iron lines will be emitted from the inner region of the accretion disk. The emission line profiles will show a variety of strong field effects, which may be used as a probe of the spin parameter of the black hole and the structure of the accretion disk. In this paper, we generalize the previous relativistic line profile models by including both the black hole spinning effects and the non-axisymmetries of warped accretion disks. Our results show different features from the conventional calculations for either a flat disk around a Kerr black hole or a warped disk around a Schwarzschild black hole by presenting, at the same time, multiple peaks, rather long red tails, and time variations of line profiles with the precession of the disk. We show disk images as seen by a distant observer, which are distorted by the strong gravity. Although we are primarily concerned with the iron K-shell lines in this paper, the calculation is general and is valid for any emission lines produced from a warped accretion disk around a black hole.
Preliminary design concepts for command and control modeling using Time Warp/hypercube
NASA Astrophysics Data System (ADS)
Laskowski, S. J.; Nugent, R. O.; Sokol, L. M.
1985-08-01
The objective of this task was to develop and evaluate preliminary design concepts for modeling command and control (C2) on the hypercube parallel processing computer architecture using the associated Time Warp operating system. MITRE performed this task in support of the Army Model Improvement Program (AMIP) Management Office (AMMO) systems research and planning efforts required as part of the development of a new family of Army models. Command and control can be thought of as large complex system of facilities, equipment, communications, procedures, and personnel through which command and control of forces and resources is exercised in performing the missions and functions assigned to them. Modeling C2 provides a means of analyzing the process and the effects of alternative doctrine, tactics, and C2 systems. The size and complexity of the command and control decision process make it difficult to model; simulation is one means of making the modeling problem tractable. The objective of this effort was to develop and evaluate design concepts for modeling command and control on the hypercube parallel processing computer architecture using the associated Time Warp operating system. In particular, the evaluation was to be responsive to two basic questions: Can Time Warp on a hypercub e architecture be used in conjunction with object-oriented techniques to significantly speed up the processing time associated with command and control modeling?
Effective Hamiltonian for surface states of Bi2Te3 nanocylinders with hexagonal warping
NASA Astrophysics Data System (ADS)
Siu, Zhuo Bin; Jalil, Mansoor B. A.; Ghee Tan, Seng
2016-06-01
The three-dimensional topological insulator \\text{B}{{\\text{i}}2}\\text{T}{{\\text{e}}3} differs from other topological insulators in the \\text{B}{{\\text{i}}2}\\text{S}{{\\text{e}}3} family in that the effective Hamiltonian of its surface states on a flat semi-infinite slab requires the addition of a cubic momentum hexagonal warping term in order to reproduce the experimentally measured constant energy contours. In this work, we derive the appropriate effective Hamiltonian for the surface states of a \\text{B}{{\\text{i}}2}\\text{T}{{\\text{e}}3} cylinder incorporating the corresponding hexagonal warping terms in a cylindrical geometry. We show that at the energy range where the surface states dominate, the effective Hamiltonian adequately reproduces the dispersion relation obtained from a full four-band Hamiltonian which describes both the bulk and surface states. As an example application of our effective Hamiltonian, we study the transmission between two collinear \\text{B}{{\\text{i}}2}\\text{T}{{\\text{e}}3} cylinders magnetized in different directions perpendicular to their axes. We show that the hexagonal warping term results in a transmission profile between the cylinders which may be of utility in a multiple state magnetic memory bit.
Kaluza-Klein graviton phenomenology for warped compactifications, and the 750 GeV diphoton excess
NASA Astrophysics Data System (ADS)
Giddings, Steven B.; Zhang, Hao
2016-06-01
A generic prediction of scenarios with extra dimensions accessible in TeV-scale collisions is the existence of Kaluza-Klein excitations of the graviton. For a broad class of strongly warped scenarios one expects to initially find an isolated resonance, whose phenomenology in the simplest cases is described by a simplified model with two parameters, its mass, and a constant Λ with units of mass parametrizing its coupling to the Standard Model stress tensor. These parameters are in turn determined by the geometrical configuration of the warped compactification. We explore the possibility that the 750 GeV excess recently seen in 13 TeV data at ATLAS and CMS could be such a warped Kaluza-Klein graviton, and find a best-fit value Λ ≈60 TeV . We find that while there is some tension between this interpretation and data from 8 TeV and from the dilepton channel at 13 TeV, it is not strongly excluded. However, in the simplest scenarios of this kind, such a signal should soon become apparent in both diphoton and dilepton channels.
Adaptive space warping to enhance passive haptics in an arthroscopy surgical simulator.
Spillmann, Jonas; Tuchschmid, Stefan; Harders, Matthias
2013-04-01
Passive haptics, also known as tactile augmentation, denotes the use of a physical counterpart to a virtual environment to provide tactile feedback. Employing passive haptics can result in more realistic touch sensations than those from active force feedback, especially for rigid contacts. However, changes in the virtual environment would necessitate modifications of the physical counterparts. In recent work space warping has been proposed as one solution to overcome this limitation. In this technique virtual space is distorted such that a variety of virtual models can be mapped onto one single physical object. In this paper, we propose as an extension adaptive space warping; we show how this technique can be employed in a mixed-reality surgical training simulator in order to map different virtual patients onto one physical anatomical model. We developed methods to warp different organ geometries onto one physical mock-up, to handle different mechanical behaviors of the virtual patients, and to allow interactive modifications of the virtual structures, while the physical counterparts remain unchanged. Various practical examples underline the wide applicability of our approach. To the best of our knowledge this is the first practical usage of such a technique in the specific context of interactive medical training. PMID:23428447
Motion estimation and compensation based on region-constrained warping prediction
NASA Astrophysics Data System (ADS)
Chang, Dong-Il; Sung, Joon H.; Kim, Jeong K.; Lee, ChoongWoong
1998-01-01
The visually annoying artifacts resulting form block matching algorithm (BMA), blocky artifacts, become noticeable in applications for low bit rates. Warping prediction (WP) based schemes can remove the blocky artifacts of BMA successfully, but they also produce severe prediction errors around the boundaries of moving objects. Since the errors around the boundaries of objects are visually sensitive, they may sometimes look more annoying than blocky artifacts. The lack of ability of modeling motion discontinuities is the major reason of the errors from WP. Motion discontinuities usually exist in practical video sequences, so that it is required to develop a more reliable motion estimation and usually exist in practical video sequences, so that it is required to develop a more reliable motion estimation and compensation scheme for low bit rate applications. In this paper, we propose a new WP scheme, named region constrained warping prediction (RCWP), which places motion discontinuities according to the segmentation results. In RCWP, there is mutual dependency between estimated motion field and segmentation mask. Because of the mutual dependency, an iterative refinement process is also introduced. Experimental results have shown that the proposed algorithm can provide much better subjective and objective performance than the BMA and the conventional warping prediction.
Ida Mann Lecture 2007: Planet eye.
McMenamin, Paul G
2008-10-01
The concept for this lecture arose as a consequence of the invitation from the College to give the 'Ida Mann Lecture' arriving recently after I had enjoyed the beautiful David Attenborough series 'Planet Earth' on television. It struck me as not too fanciful an idea at the time to make an analogy between 'Planet Earth' and the eye and thus the idea of giving an Attenborough-like tour of the ocular microenvironments and making the analogy between various immune cells in the eye and wildlife on planet Earth was born. I could only hope that in some small measure my presentation would inspire and educate an audience of ophthalmologists on the amazing world of ocular immune cells in the way that David Attenborough enraptures millions of television viewers with his beautiful series. PMID:18983543
Lectures series in computational fluid dynamics
NASA Technical Reports Server (NTRS)
Thompson, Kevin W.
1987-01-01
The lecture notes cover the basic principles of computational fluid dynamics (CFD). They are oriented more toward practical applications than theory, and are intended to serve as a unified source for basic material in the CFD field as well as an introduction to more specialized topics in artificial viscosity and boundary conditions. Each chapter in the test is associated with a videotaped lecture. The basic properties of conservation laws, wave equations, and shock waves are described. The duality of the conservation law and wave representations is investigated, and shock waves are examined in some detail. Finite difference techniques are introduced for the solution of wave equations and conservation laws. Stability analysis for finite difference approximations are presented. A consistent description of artificial viscosity methods are provided. Finally, the problem of nonreflecting boundary conditions are treated.
Lecture 4: transmission lines and capacitors
Butcher, R.R.
1980-01-01
The topic of this lecture is pulse forming networks. The first item of discussion will be transmission lines because they are so prevalent, even if only in the form of coaxial cable. From there the subject will proceed to pulse-forming networks: the practical problems encountered with them, their advantages, and disadvantages. Capacitors will be our final topic, as they are the limiting factor in lumped transmission elements.
1995 Edward teller lecture. Patience and optimism
NASA Astrophysics Data System (ADS)
Miley, George H.
1996-05-01
Remarks made in the author's acceptance lecture for the 1995 Edward Teller Medal are presented and expanded. Topics covered include research on nuclear-pumped lasers, the first direct e-beam-pumped laser, direct energy conversion and advanced fuel fusion, plus recent work on inertial electrostatic confinement. ``Patience'' and ``optimism'' are viewed as essential elements needed by scientists following the ``zig-zag'' path to fusion energy production.
Aeroelasticity - Frontiers and beyond /von Karman Lecture/
NASA Technical Reports Server (NTRS)
Garrick, I. E.
1976-01-01
The lecture aims at giving a broad survey of the current reaches of aeroelasticity with some narrower views for the specialist. After a short historical review of concepts for orientation, several topics are briefly presented. These touch on current flight vehicles having special points of aeroelastic interest; recent developments in the active control of aeroelastic response including control of flutter; remarks on the unsteady aerodynamics of arbitrary configurations; problems of the space shuttle related to aeroelasticity; and aeroelastic response in flight.
TASI 2008 Lectures on Dark Matter
Hooper, Dan; /Fermilab /Chicago U., Astron. Astrophys. Ctr.
2009-01-01
Based on lectures given at the 2008 Theoretical Advanced Study Institute (TASI), I review here some aspects of the phenomenology of particle dark matter, including the process of thermal freeze-out in the early universe, and the direct and indirect detection of WIMPs. I also describe some of the most popular particle candidates for dark matter and summarize the current status of the quest to discover dark matter's particle identity.
Exploring how nurse lecturers maintain clinical credibility.
Fisher, Melanie T
2005-01-01
The role of the nurse lecturer is changing. There is growing pressure from the government and professionals alike to recruit nurse teachers who posses both practical and recent experience of nursing [Department of Health, 1999. Making a Difference: Strengthening the Nursing, Midwifery and Health Visiting Contribution to Health and Health Care. DOH, London; UKCC, 2000. Standards for the Preparation of Teachers of Nursing, Midwifery and Health Visiting. UKCC, London]. Whilst much of the literature available suggests a growing concern amongst practitioners, students and nurse educationalists themselves about the importance of being ;clinically credible', what is not clear is how tangible it is to maintain currency and clinical credibility. In addition, the term ;clinical credibility' is in itself ill-defined. An exploratory study was undertaken within one higher education institution which sought to seek the views of nurse lecturers. The principles of ethnography were applied to this research. The sample included six of the most recently appointed nurse lecturers within one academic faculty who taught predominantly on pre-registration programmes. Data from individual and focus group interviews was analysed using a thematic content analysis approach. The findings are discussed which embrace the concepts of: working ;hands on' in the clinical area, clinical currency, transferability of skills, clinical visibility and role development. Recommendations for the development of professional practice are offered. PMID:19038175
The (Embodied) Performance of Physics Concepts in Lectures
NASA Astrophysics Data System (ADS)
Hwang, Sungwon; Roth, Wolff-Michael
2011-08-01
Lectures are often thought of in terms of information transfer: students (do not) "get" or "construct meaning of" what physics professors (lecturers) say and the notes they put on the chalkboard (overhead). But this information transfer view does not explain, for example, why students have a clear sense of understanding while they sit in a lecture and their subsequent experiences of failure to understand their own lecture notes or textbooks while preparing for an exam. Based on a decade of studies on the embodied nature of science lectures, the purpose of this article is to articulate and exemplify a different way of understanding physics lectures. We exhibit how there is more to lectures than the talk plus notes. This informational "more" may explain (part of) the gap between students' participative understanding that exists in the situation where they sit in the lecture on the one hand and the one where they study for an exam from their lecture notes on the other. Our results suggest that in lectures, concepts are heterogeneous performances in which meaning is synonymous with the synergistic and irreducible transactions of many different communicative modes, including gestures, body movements, body positions, prosody, and so forth.
The Trieste Lecture of John Stewart Bell
NASA Astrophysics Data System (ADS)
Bassi, Angelo; Carlo Ghirardi, Gian
2007-03-01
Delivered at Trieste on the occasion of the 25th Anniversary of the International Centre for Theoretical Physics, 2 November 1989 The video of this lecture is available here. Please see the PDF for the transcript of the lecture. General remarks by Angelo Bassi and GianCarlo Ghirardi During the autumn of 1989 the International Centre for Theoretical Physics, Trieste, celebrated the 25th anniversary of its creation. Among the many prestigious speakers, who delivered extremely interesting lectures on that occasion, was the late John Stewart Bell. All lectures have been recorded on tape. We succeeded in getting a copy of John's lecture. In the lecture, many of the arguments that John had lucidly stressed in his writings appear once more, but there are also extremely interesting new remarks which, to our knowledge, have not been presented elsewhere. In particular he decided, as pointed out by the very choice of the title of his lecture, to call attention to the fact that the theory presents two types of difficulties, which Dirac classified as first and second class. The former are those connected with the so-called macro-objectification problem, the latter with the divergences characterizing relativistic quantum field theories. Bell describes the precise position of Dirac on these problems and he stresses appropriately how, contrary to Dirac's hopes, the steps which have led to a partial overcoming of the second class difficulties have not helped in any way whatsoever to overcome those of the first class. He then proceeds to analyse the origin and development of the Dynamical Reduction Program and draws attention to the problems that still affect it, in particular that of a consistent relativistic generalization. When the two meetings Are there quantum jumps? and On the present status of Quantum Mechanics were organized in Trieste and Losinj (Croatia), on 5 10 September 2005, it occurred to us that this lecture, which has never been published, might represent an
The Trieste Lecture of John Stewart Bell
NASA Astrophysics Data System (ADS)
Bassi, Angelo; Carlo Ghirardi, Gian
2007-03-01
Delivered at Trieste on the occasion of the 25th Anniversary of the International Centre for Theoretical Physics, 2 November 1989 The video of this lecture is available here. Please see the PDF for the transcript of the lecture. General remarks by Angelo Bassi and GianCarlo Ghirardi During the autumn of 1989 the International Centre for Theoretical Physics, Trieste, celebrated the 25th anniversary of its creation. Among the many prestigious speakers, who delivered extremely interesting lectures on that occasion, was the late John Stewart Bell. All lectures have been recorded on tape. We succeeded in getting a copy of John's lecture. In the lecture, many of the arguments that John had lucidly stressed in his writings appear once more, but there are also extremely interesting new remarks which, to our knowledge, have not been presented elsewhere. In particular he decided, as pointed out by the very choice of the title of his lecture, to call attention to the fact that the theory presents two types of difficulties, which Dirac classified as first and second class. The former are those connected with the so-called macro-objectification problem, the latter with the divergences characterizing relativistic quantum field theories. Bell describes the precise position of Dirac on these problems and he stresses appropriately how, contrary to Dirac's hopes, the steps which have led to a partial overcoming of the second class difficulties have not helped in any way whatsoever to overcome those of the first class. He then proceeds to analyse the origin and development of the Dynamical Reduction Program and draws attention to the problems that still affect it, in particular that of a consistent relativistic generalization. When the two meetings Are there quantum jumps? and On the present status of Quantum Mechanics were organized in Trieste and Losinj (Croatia), on 5 10 September 2005, it occurred to us that this lecture, which has never been published, might represent an
NASA Astrophysics Data System (ADS)
Bergmann, Ryan
Graphics processing units, or GPUs, have gradually increased in computational power from the small, job-specific boards of the early 1990s to the programmable powerhouses of today. Compared to more common central processing units, or CPUs, GPUs have a higher aggregate memory bandwidth, much higher floating-point operations per second (FLOPS), and lower energy consumption per FLOP. Because one of the main obstacles in exascale computing is power consumption, many new supercomputing platforms are gaining much of their computational capacity by incorporating GPUs into their compute nodes. Since CPU-optimized parallel algorithms are not directly portable to GPU architectures (or at least not without losing substantial performance), transport codes need to be rewritten to execute efficiently on GPUs. Unless this is done, reactor simulations cannot take full advantage of these new supercomputers. WARP, which can stand for ``Weaving All the Random Particles,'' is a three-dimensional (3D) continuous energy Monte Carlo neutron transport code developed in this work as to efficiently implement a continuous energy Monte Carlo neutron transport algorithm on a GPU. WARP accelerates Monte Carlo simulations while preserving the benefits of using the Monte Carlo Method, namely, very few physical and geometrical simplifications. WARP is able to calculate multiplication factors, flux tallies, and fission source distributions for time-independent problems, and can run in both criticality or fixed source modes. WARP can transport neutrons in unrestricted arrangements of parallelepipeds, hexagonal prisms, cylinders, and spheres. WARP uses an event-based algorithm, but with some important differences. Moving data is expensive, so WARP uses a remapping vector of pointer/index pairs to direct GPU threads to the data they need to access. The remapping vector is sorted by reaction type after every transport iteration using a high-efficiency parallel radix sort, which serves to keep the
Anatomic standardization: Linear scaling and nonlinear warping of functional brain images
Minoshima, S.; Koeppe, R.A.; Frey, K.A.
1994-09-01
An automated method was proposed for anatomic standardization of PET scans in three dimensions, which enabled objective intersubject and cross-group comparisons of functional brain images. The method involved linear scaling to correct for individual brain size and nonlinear warping to minimize regional anatomic variations among subjects. In the linear-scaling step, the anteroposterior length and width of the brain were measured on the PET images, and the brain height was estimated by a contour-matching procedure using the midsagittal plane. In the nonlinear warping step, individual gray matter locations were matched with those of a standard brain by maximizing correlation coefficients of regional profile curves determined between predefined stretching centers (predominantly in white matter) and the gray matter landmarks. The accuracy of the brain height estimation was compared with skull x-ray estimations, showing comparable accuracy and better reproducibility. Linear-scaling and nonlinear warping methods were validated using ({sup 18}F)fluorodeoxyglucose and ({sup 15}O)water images. Regional anatomic variability on the glucose images was reduced markedly. The statistical significance of activation foci in paired water images was improved in both vibratory and visual activation paradigms. A group versus group comparison following the proposed anatomic standardization revealed highly significant glucose metabolic alterations in the brains of patients with Alzheimer`s disease compared with those of a normal control group. These results suggested that the method is well suited to both research and clinical settings and can facilitate pixel-by-pixel comparisons of PET images. 26 refs., 9 figs., 1 tab.
Wang Shijun; Yao Jianhua; Liu Jiamin; Petrick, Nicholas; Van Uitert, Robert L.; Periaswamy, Senthil; Summers, Ronald M.
2009-12-15
Purpose: In computed tomographic colonography (CTC), a patient will be scanned twice--Once supine and once prone--to improve the sensitivity for polyp detection. To assist radiologists in CTC reading, in this paper we propose an automated method for colon registration from supine and prone CTC scans. Methods: We propose a new colon centerline registration method for prone and supine CTC scans using correlation optimized warping (COW) and canonical correlation analysis (CCA) based on the anatomical structure of the colon. Four anatomical salient points on the colon are first automatically distinguished. Then correlation optimized warping is applied to the segments defined by the anatomical landmarks to improve the global registration based on local correlation of segments. The COW method was modified by embedding canonical correlation analysis to allow multiple features along the colon centerline to be used in our implementation. Results: We tested the COW algorithm on a CTC data set of 39 patients with 39 polyps (19 training and 20 test cases) to verify the effectiveness of the proposed COW registration method. Experimental results on the test set show that the COW method significantly reduces the average estimation error in a polyp location between supine and prone scans by 67.6%, from 46.27{+-}52.97 to 14.98 mm{+-}11.41 mm, compared to the normalized distance along the colon centerline algorithm (p<0.01). Conclusions: The proposed COW algorithm is more accurate for the colon centerline registration compared to the normalized distance along the colon centerline method and the dynamic time warping method. Comparison results showed that the feature combination of z-coordinate and curvature achieved lowest registration error compared to the other feature combinations used by COW. The proposed method is tolerant to centerline errors because anatomical landmarks help prevent the propagation of errors across the entire colon centerline.
Man's impact on the troposphere: Lectures in tropospheric chemistry
NASA Technical Reports Server (NTRS)
Levine, J. S. (Editor); Schryer, D. R. (Editor)
1978-01-01
Lectures covering a broad spectrum of current research in tropospheric chemistry with particular emphasis on the interaction of measurements, modeling, and understanding of fundamental processes are presented.
Effects of lecture information density on medical student achievement.
Russell, I J; Hendricson, W D; Herbert, R J
1984-11-01
With the virtual explosion of biomedical information, the medical educator regularly faces a quandary regarding how much to include in the medical curriculum. Opinions differ regarding how much of the available information on a particular topic should be presented in a medical school lecture. To understand better the effect of lecture information density on learning by medical students, one of the authors gave a basic clinical lecture only or clinical lectures with varying amounts of semirelated information. Tests which measured only retention of the basic material were given before lecture attendance, immediately after the lecture, and 15 days later. The results indicated that increasing the information density of a lecture reduced retention of the basic information. The memory loss apparently was due to information presented late in the lecture displacing facts learned by the students earlier in the same hour. The data suggest that lectures to medical students are more effective aids to learning when the information density is limited to a few main points that are "essential to know." PMID:6492106
Using Photo Story Lectures in an Online Astronomy Class
NASA Astrophysics Data System (ADS)
Caffey, James F.
2008-05-01
Photo Story is a free program from Microsoft that was designed to allow people to make videos from photos and add a voice narration to it. I use Photo Story to create video lectures in my online Astronomy class at Drury University in Springfield, Missouri. I take power point slides from my publisher, turn them into JPEG files, and add my voice over them to create the video lecture. Students at a distance say the lectures make them feel like they are back in the classroom. I will present several lectures.
The work of lecturing in high school chemistry
NASA Astrophysics Data System (ADS)
Hwang, SungWon; Roth, Wolff-Michael
2013-09-01
Lecturing is an important aspect of the culture of science education. Perhaps because of the negative associations constructivist educators make with lecturing, little research has been done concerning the generally invisible aspects of the (embodied, lived) work that is required. Traditional research on science lectures focuses on ideas and (mental) concepts that somehow are "gotten across"; and it is interested in identifying verbal content and visual representations science teachers provide. The purpose of this study is to explicitly describe and theorize the living work of lecturing that produces in a societal arena everything from which students can learn. We use two case studies from the chemistry lectures in a tenth-grade Singapore classroom to exemplify the central role of the performative aspects of lecturing. We articulate and exemplify assertions that (a) corporeal performances differentiate and coordinate the contents of lecturing with its pitch, rhythm, and speech volume, and thereby orient students to specific discourse features of chemistry; and (b) corporeal performances differentiate and coordinate layers of talk with prosody, gestures, and body orientation, and thereby make analogies available to students. We conclude that what is visible in lectures (e.g., scientific discourse, analogies) is always the outcome of the (generally unattended to) corporeal labor including gestures, body orientation, and prosodic features (e.g., shifts in pitch) and that this outcome | labor pair constitutes an appropriate unit of understanding lecturing as societal phenomenon.
Automatic Camera Control System for a Distant Lecture with Videoing a Normal Classroom.
ERIC Educational Resources Information Center
Suganuma, Akira; Nishigori, Shuichiro
The growth of a communication network technology enables students to take part in a distant lecture. Although many lectures are conducted in universities by using Web contents, normal lectures using a blackboard are still held. The latter style lecture is good for a teacher's dynamic explanation. A way to modify it for a distant lecture is to…
Cough Recognition Based on Mel Frequency Cepstral Coefficients and Dynamic Time Warping
NASA Astrophysics Data System (ADS)
Zhu, Chunmei; Liu, Baojun; Li, Ping
Cough recognition provides important clinical information for the treatment of many respiratory diseases, but the assessment of cough frequency over a long period of time remains unsatisfied for either clinical or research purpose. In this paper, according to the advantage of dynamic time warping (DTW) and the characteristic of cough recognition, an attempt is made to adapt DTW as the recognition algorithm for cough recognition. The process of cough recognition based on mel frequency cepstral coefficients (MFCC) and DTW is introduced. Experiment results of testing samples from 3 subjects show that acceptable performances of cough recognition are obtained by DTW with a small training set.
NASA Astrophysics Data System (ADS)
Chen, Liang; Chang, Kai
We use a variation of the Lifshitz formula to calculate the anisotropic Casimir energy density between two topological insulators in the vacuum. We find that the hexagonal warping effect can induce a Casimir torque between the two topological insulators, Tc ~ sin (6 θ) with twisted angle θ. The maximal Casimir torque at θ = π / 12 is estimated to be ~10-19 N . m / rad for Bi2Te3 on the [111] surface when the distance between the two topological insulators is about 20 nm and the surface areas are taken to be ~ 1 cm2 .
Wave-like warp propagation in circumbinary discs - I. Analytic theory and numerical simulations
NASA Astrophysics Data System (ADS)
Facchini, Stefano; Lodato, Giuseppe; Price, Daniel J.
2013-08-01
In this paper we analyse the propagation of warps in protostellar circumbinary discs. We use these systems as a test environment in which to study warp propagation in the bending-wave regime, with the addition of an external torque due to the binary gravitational potential. In particular, we want to test the linear regime, for which an analytic theory has been developed. In order to do so, we first compute analytically the steady-state shape of an inviscid disc subject to the binary torques. The steady-state tilt is a monotonically increasing function of radius, but misalignment is found at the disc inner edge. In the absence of viscosity, the disc does not present any twist. Then, we compare the time-dependent evolution of the warped disc calculated via the known linearized equations both with the analytic solutions and with full 3D numerical simulations. The simulations have been performed with the PHANTOM smoothed particle hydrodynamics (SPH) code using two million particles. We find a good agreement both in the tilt and in the phase evolution for small inclinations, even at very low viscosities. Moreover, we have verified that the linearized equations are able to reproduce the diffusive behaviour when α > H/R, where α is the disc viscosity parameter. Finally, we have used the 3D simulations to explore the non-linear regime. We observe a strongly non-linear behaviour, which leads to the breaking of the disc. Then, the inner disc starts precessing with its own precessional frequency. This behaviour has already been observed with numerical simulations in accretion discs around spinning black holes. The evolution of circumstellar accretion discs strongly depends on the warp evolution. Therefore, the issue explored in this paper could be of fundamental importance in order to understand the evolution of accretion discs in crowded environments, when the gravitational interaction with other stars is highly likely, and in multiple systems. Moreover, the evolution of
On lateral buckling of end-loaded cantilevers, including the effect of warping stiffness
NASA Astrophysics Data System (ADS)
Reissner, E.; Reissner, J. E.; Wan, F. Y. M.
1987-06-01
We investigate the numerical consequences of the presence of certain non-linear terms in the expressions for the components of transverse shearing strain which occur in the derivation of one-dimensional equations for small finite deflections of straight beams from three-dimensional finite elasticity through use of the principle of minimum potential energy. While particular emphasis is placed on the effect of warping stiffness, the paper also includes results of interest in connection with the classical Michell-Prandtl-analysis of lateral buckling of endloaded cantilevers. Comprehensive numerical results are obtained for the entire range of the relevant dimensionless parameters, using power series, asymptotic expansion and modern numerical methods procedures.
3 users abandon plastic rooftop-sprinkler systems: say sun warps and cracks pipes
Galvin, C.
1982-05-03
Cold temperature and exposure to the sun have cracked and warped plastic piping used for rooftop sprinklers and caused some users to remove the systems they hoped would reduce cooling costs. Manufacturers of the polyvinyl chloride (PVC) pipe, however, claim the cracking was due to improper draining. Copper tubing can be used, but at a 20 to 50% increase in cost. Chemical treatment to repel ultraviolet rays must be used on PVC piping to withstand sunlight. Several users report their experiences with rooftop sprinkling systems. (DCK)
Time-dependent gravitating solitons in five-dimensional warped space-times
Giovannini, Massimo
2007-12-15
Time-dependent soliton solutions are explicitly derived in a five-dimensional theory endowed with one (warped) extra dimension. Some of the obtained geometries, everywhere well defined and technically regular, smoothly interpolate between two five-dimensional anti-de Sitter space-times for a fixed value of the conformal time coordinate. Time-dependent solutions containing both topological and nontopological sectors are also obtained. Supplementary degrees of freedom can be also included and, in this case, the resulting multisoliton solutions may describe time-dependent kink-antikink system000.
LETTER TO THE EDITOR: Quantum effects in the Alcubierre warp-drive spacetime
NASA Astrophysics Data System (ADS)
Hiscock, William A.
1997-11-01
The expectation value of the stress - energy tensor of a free conformally invariant scalar field is computed in a two-dimensional reduction of the Alcubierre `warp-drive' spacetime. Unless the spacetime is in the Hartle - Hawking state at an appropriate temperature, the stress - energy diverges on past and future event horizons which form when the apparent velocity of the spaceship exceeds the speed of light. The likelihood of the spacetime being in this state, whether due to natural evolution or the application of technology, is briefly discussed.
Radiative corrections to the lightest neutral Higgs mass in warped supersymmetry
Bhattacharyya, Gautam; Ray, Tirtha Sankar
2008-10-01
We compute radiative correction to the lightest neutral Higgs mass (m{sub h}) induced by the Kaluza-Klein (KK) towers of fermions and sfermions in a minimal supersymmetric scenario embeded in a 5-dimensional warped space. The Higgs is confined to the TeV brane. The KK spectra of matter supermultiplets is tied to the explanation of the fermion mass hierarchy problem. We demonstrate that for a reasonable choice of extra-dimensional parameters, the KK-induced radiative correction can enhance the upper limit on m{sub h} by as much as 100 GeV beyond the 4d limit of 135 GeV.
Modeling laser-driven electron acceleration using WARP with Fourier decomposition
NASA Astrophysics Data System (ADS)
Lee, P.; Audet, T. L.; Lehe, R.; Vay, J.-L.; Maynard, G.; Cros, B.
2016-09-01
WARP is used with the recent implementation of the Fourier decomposition algorithm to model laser-driven electron acceleration in plasmas. Simulations were carried out to analyze the experimental results obtained on ionization-induced injection in a gas cell. The simulated results are in good agreement with the experimental ones, confirming the ability of the code to take into account the physics of electron injection and reduce calculation time. We present a detailed analysis of the laser propagation, the plasma wave generation and the electron beam dynamics.
Graphene: materials in the Flatland (Nobel lecture).
Novoselov, Kostya S
2011-07-25
Much like the world described in Abbott's "Flatland", graphene is a two-dimensional object. And, as "Flatland" is "A Romance of Many Dimensions", graphene is much more than just a flat crystal. It possesses a number of unusual properties which are often unique or superior to those in other materials. In this brief lecture I would like to explain the reason for my (and many other people's) fascination with this material, and invite the reader to share some of the excitement I've experienced while researching it. PMID:21732505
Nobel Lecture: Graphene: Materials in the Flatland
NASA Astrophysics Data System (ADS)
Novoselov, K. S.
2011-07-01
Much like the world described in Abbott’s Flatland, graphene is a two-dimensional object. And, as “Flatland” is “a romance of many dimensions,” graphene is much more than just a flat crystal. It possesses a number of unusual properties which are often unique or superior to those in other materials. In this brief lecture I would like to explain the reason for my (and many other people’s) fascination with this material, and invite the reader to share some of the excitement I’ve experienced while researching it.
NASA Astrophysics Data System (ADS)
Quigg, Chris
2002-04-01
A public lecture is an invitation to conversation, and it is also a performance. A lively conversation---especially when one person does most of the talking---requires that you have something to say. A memorable performance requires assiduous preparation. I will touch on a number of important elements: preparing the scene and eliminating barriers between you and the audience ... engaging your listeners with a narrative arc ... the uses of the minute particular ... tension and resolution, surprise and drama ... experiments and demonstrations, specimens and souvenirs ... showing yourself, and your passion.
[Information technologies in clinical cytology (a lecture)].
Shabalova, I P; Dzhangirova, T V; Kasoian, K T
2010-07-01
The lecture is devoted to the urgent problem that is to increase the quality of cytological diagnosis, by diminishing the subjectivism factor via introduction of up-to-date computer information technologies into a cytologist's practice. Its main lines from the standardization of cytological specimen preparation to the registration of a cytologist's opinion and the assessment of the specialist's work quality at the laboratories that successfully use the capacities of the current information systems are described. Information technology capabilities to improve the interpretation of the cellular composition of cytological specimens are detailed. PMID:20799410
1995 Edward teller lecture. Patience and optimism
Miley, G.H.
1996-05-01
Remarks made in the author{close_quote}s acceptance lecture for the 1995 Edward Teller Medal are presented and expanded. Topics covered include research on nuclear-pumped lasers, the first direct e-beam-pumped laser, direct energy conversion and advanced fuel fusion, plus recent work on inertial electrostatic confinement. {open_quote}{open_quote}Patience{close_quote}{close_quote} and {open_quote}{open_quote}optimism{close_quote}{close_quote} are viewed as essential elements needed by scientists following the {open_quote}{open_quote}zig-zag{close_quote}{close_quote} path to fusion energy production. {copyright} {ital 1996 American Institute of Physics.}
NASA Astrophysics Data System (ADS)
Fedorova , E.; Vasylenko, A.; Hnatyk, B. I.; Zhdanov, V. I.
2016-02-01
We analyze the X-ray properties of the Compton-thick Seyfert 1.9 radio quiet AGN in NGC 1194 using INTEGRAL (ISGRI), XMM-Newton (EPIC), Swift (BAT and XRT), and Suzaku (XIS) observations. There is a set of Fe-K lines in the NGC 1194 spectrum with complex relativistic profiles that can be considered as a sign of either a warped Bardeen-Petterson accretion disk or double black hole. We compare our results on NGC 1194 with two other megamaser warped disk candidates, NGC 1068 and NGC 4258, to trace out the other properties which can be typical for AGNs with warped accretion disks. To finally confirm or disprove the double black-hole hypotheses, further observations of the iron lines and their evolution of their shape with time are necessary. Based on obsrvations made with INTEGRAL, XMM-Newton, Swift, Suzaku.
Buckley, Christopher D
2012-01-01
The warp ikat method of making decorated textiles is one of the most geographically widespread in southeast Asia, being used by Austronesian peoples in Indonesia, Malaysia and the Philippines, and Daic peoples on the Asian mainland. In this study a dataset consisting of the decorative characters of 36 of these warp ikat weaving traditions is investigated using Bayesian and Neighbornet techniques, and the results are used to construct a phylogenetic tree and taxonomy for warp ikat weaving in southeast Asia. The results and analysis show that these diverse traditions have a common ancestor amongst neolithic cultures the Asian mainland, and parallels exist between the patterns of textile weaving descent and linguistic phylogeny for the Austronesian group. Ancestral state analysis is used to reconstruct some of the features of the ancestral weaving tradition. The widely held theory that weaving motifs originated in the late Bronze Age Dong-Son culture is shown to be inconsistent with the data. PMID:23272211
Buckley, Christopher D.
2012-01-01
The warp ikat method of making decorated textiles is one of the most geographically widespread in southeast Asia, being used by Austronesian peoples in Indonesia, Malaysia and the Philippines, and Daic peoples on the Asian mainland. In this study a dataset consisting of the decorative characters of 36 of these warp ikat weaving traditions is investigated using Bayesian and Neighbornet techniques, and the results are used to construct a phylogenetic tree and taxonomy for warp ikat weaving in southeast Asia. The results and analysis show that these diverse traditions have a common ancestor amongst neolithic cultures the Asian mainland, and parallels exist between the patterns of textile weaving descent and linguistic phylogeny for the Austronesian group. Ancestral state analysis is used to reconstruct some of the features of the ancestral weaving tradition. The widely held theory that weaving motifs originated in the late Bronze Age Dong-Son culture is shown to be inconsistent with the data. PMID:23272211
The effect of tooling design parameters on web-warping in the flexible roll forming of UHSS
Jiao, Jingsi; Weiss, Matthias; Rolfe, Bernard; Mendiguren, Joseba; Galdos, Lander
2013-12-16
To reduce weight and improve passenger safety there is an increased need in the automotive industry to use Ultra High Strength Steels (UHSS) for structural and crash components. However, the application of UHSS is restricted by their limited formability and the difficulty of forming them in conventional processes. An alternative method of manufacturing structural auto body parts from UHSS is the flexible roll forming process which can accommodate materials with high strength and limited ductility in the production of complex and weight-optimised components. However, one major concern in the flexible roll forming is web-warping, which is the height deviation of the profile web area. This paper investigates, using a numerical model, the effect on web-warping with respect to various forming methods. The results demonstrate that different forming methods lead to different amount of web-warping in terms of forming the product with identical geometry.
NASA Technical Reports Server (NTRS)
Vanderspiegel, Jan
1994-01-01
This report surveys different technologies and approaches to realize sensors for image warping. The goal is to study the feasibility, technical aspects, and limitations of making an electronic camera with special geometries which implements certain transformations for image warping. This work was inspired by the research done by Dr. Juday at NASA Johnson Space Center on image warping. The study has looked into different solid-state technologies to fabricate image sensors. It is found that among the available technologies, CMOS is preferred over CCD technology. CMOS provides more flexibility to design different functions into the sensor, is more widely available, and is a lower cost solution. By using an architecture with row and column decoders one has the added flexibility of addressing the pixels at random, or read out only part of the image.
ERIC Educational Resources Information Center
Sun, Yu-Chih; Yang, Hui-Chi
2012-01-01
Open source lectures not only provide knowledge-seekers with convenient ways to obtain knowledge and information, they also serve as potential language learning resources that provide extensive language input and repeated exposure to vocabulary within specific topics or disciplines. This current study aims to examine the relationship between…
Hadjianastasis, Marios; Nightingale, Karl P
2016-02-01
Lecture capture or 'podcasting' technology offers a new and engaging format of learning materials that can be used to increase the flexibility and interactivity of learning and teaching environments. Here we discuss different ways that these recordings can be incorporated into STEM discipline teaching, and the impact this can have on students' learning. PMID:26764422
Introductory Lectures on D-Branes
NASA Astrophysics Data System (ADS)
Vancea, Ion Vasile
2002-11-01
This is a pedagogical introduction to D-branes, addressed to graduate students in field theory and particle physics and to other beginners in string theory. I am not going to review the most recent results since there are already many good papers on web devoted to that. Instead, I will present some old techniques in some detail in order to show how some basic properties of strings and branes as the massless spectrum of string, the effective action of D-branes and their tension can be computed using QFT techniques. Also, I will present shortly the boundary state description of D-branes. The details are exposed for bosonic branes since I do not assume any previous knowledge of supersymmetry which is not a requirement for this school. However, for completeness and to provide basic notions for other lectures, I will discuss the some properties of supersymmetric branes. The present lectures were delivered at Jorge André Swieca School on Particle and Fields, 2001, Campos do Jordão, Brazil.
Lecture capturing assisted teaching and learning experience
NASA Astrophysics Data System (ADS)
Chen, Li
2015-03-01
When it comes to learning, a deep understanding of the material and a broadband of knowledge are equally important. However, provided limited amount of semester time, instructors often find themselves struggling to reach both aspects at the same time and are often forced to make a choice between the two. On one hand, we would like to spend much time to train our students, with demonstrations, step by step guidance and practice, to develop strong critical thinking skills and problem-solving skills. On the other hand, we also would like to cover a wide range of content topics to broaden our students' understanding. In this presentation, we propose a working scheme that may assist to achieve these two goals at the same time without sacrificing either one. With the help of recorded and pre-recorded lectures and other class materials, it allows instructors to spend more class time to focus on developing critical thinking skills and problem-solving skills, and to apply and connect principle knowledge with real life phenomena. It also allows our students to digest the material at a pace they are comfortable with by watching the recorded lectures over and over. Students now have something as a backup to refer to when they have random mistakes and/or missing spots on their notes, and hence take more ownership of their learning. Advanced technology have offered flexibility of how/when the content can be delivered, and have been assisting towards better teaching and learning strategies.
There is more to training than lecture
Mayfield, N.E.; Bahrt, W.A.
1991-02-01
This presentation describes information that is useful in correlating on-the-job training with developing and delivering classroom training, which enhances the learning process. Greater emphasis is being placed on classroom training versus self-study in all facets of industry. The outcome is that classroom instruction is all-too-often delivered through direct lecture. This is probably the least effective method of providing quality training. Enhancements to the classroom learning environment are necessary--such as well-planned viewgraphs, flip charts, posters, mockups, videos, demonstration activities, an on-the-job training. Without this emphasis, all too often, classroom instruction is no more effective than self-study. Most classroom training lacks demonstration activities and/or on-the-job training interfaces. Remember what Confucius said: When I hear I forget, when I see I remember, when I do I understand.'' Therefore, it makes sense to involve students through demonstration activities and/or on-the-job training as an integral part of lesson design. We need to make a conscious effort to ensure trainees understand the instructions that are necessary to perform job functions. This requires, in many cases, a diversion from past practices. We must become innovative and involve the trainees in practical activities to avoid the dismal effects of the straight lecture format. 1 ref., 2 figs.
Mars Observer Lecture: Mars Orbit Insertion
NASA Technical Reports Server (NTRS)
Dodd, Suzanne R. (Personal Name)
1993-01-01
The Mars Observer mission spacecraft was primarily designed for exploring Mars and the Martian environment. The Mars Observer was launched on September 25, 1992. The spacecraft was lost in the vicinity of Mars on August 21, 1993 when the spacecraft began its maneuvering sequence for Martian orbital insertion. This videotape shows a lecture by Suzanne R. Dodd, the Mission Planning Team Chief for the Mars Observer Project. Ms Dodd begins with a brief overview of the mission and the timeline from the launch to orbital insertion. Ms Dodd then reviews slides showing the trajectory of the spacecraft on its trip to Mars. Slides of the spacecraft being constructed are also shown. She then discusses the Mars orbit insertion and the events that will occur to move the spacecraft from the capture orbit into a mapping orbit. During the trip to Mars, scientists at JPL had devised a new strategy, called Power In that would allow for an earlier insertion into the mapping orbit. The talk summarizes this strategy, showing on a slide the planned transition orbits. There are shots of the Martian moon, Phobos, taken from the Viking spacecraft, as Ms Dodd explains that the trajectory will allow the orbiter to make new observations of that moon. She also explains the required steps to prepare for mapping after the spacecraft has achieved the mapping orbit around Mars. The lecture ends with a picture of Mars from the Observer on its approach to the planet.
NASA Astrophysics Data System (ADS)
Li, Yan-Rong; Wang, Jian-Min; Cheng, Cheng; Qiu, Jie
2015-05-01
Warped accretion disks have attracted intense attention because of their critical role in shaping the spin of supermassive massive black holes (SMBHs) through the Bardeen-Petterson effect, a general relativistic effect that leads to final alignments or anti-alignments between black holes and warped accretion disks. We study such alignment processes by explicitly taking into account the finite sizes of accretion disks and the episodic lifetimes of active galactic nuclei (AGNs) that delineate the duration of gas fueling onto accretion disks. We employ an approximate global model to simulate the evolution of accretion disks, allowing us to determine the gravitomagnetic torque that drives the alignments in a simple way. We then track down the evolutionary paths for mass and spin of black holes both in a single activity episode and over a series of episodes. Given with randomly and isotropically oriented gas fueling over episodes, we calculate the spin evolution with different episodic lifetimes and find that it is quite sensitive to the lifetimes. We therefore propose that the spin distribution of SMBHs can place constraints on the episodic lifetimes of AGNs and vice versa. The applications of our results on the observed spin distributions of SMBHs and the observed episodic lifetimes of AGNs are discussed, although both measurements at present are too ambiguous for us to draw a firm conclusion. Our prescription can be easily incorporated into semi-analytic models for black hole growth and spin evolution.
Chilton, Sven H.
2008-04-15
The WARP code is a robust electrostatic particle-in-cell simulation package used to model charged particle beams with strong space-charge forces. A fundamental operation associated with seeding detailed simulations of a beam transport channel is to generate initial conditions where the beam distribution is matched to the structure of a periodic focusing lattice. This is done by solving for periodic, matched solutions to a coupled set of ODEs called the Kapchinskij-Vladimirskij (KV) envelope equations, which describe the evolution of low-order beam moments subject to applied lattice focusing, space-charge defocusing, and thermal defocusing forces. Recently, an iterative numerical method was developed (Lund, Chilton, and Lee, Efficient computation of matched solutions to the KV envelope equations for periodic focusing lattices, Physical Review Special Topics-Accelerators and Beams 9, 064201 2006) to generate matching conditions in a highly flexible, convergent, and fail-safe manner. This method is extended and implemented in the WARP code as a Python package to vastly ease the setup of detailed simulations. In particular, the Python package accommodates any linear applied lattice focusing functions without skew coupling, and a more general set of beam parameter specifications than its predecessor. Lattice strength iteration tools were added to facilitate the implementation of problems with specific applied focusing strengths.
Chilton, Sven H.
2008-03-01
The WARP code is a robust electrostatic particle-in-cell simulation package used to model charged particle beams with strong space-charge forces. A fundamental operation associated with seeding detailed simulations of a beam transport channel is to generate initial conditions where the beam distribution is matched to the structure of a periodic focusing lattice. This is done by solving for periodic, matched solutions to a coupled set of ODEs called the Kapchinskij-Vladimirskij (KV) envelope equations, which describe the evolution of low-order beam moments subject to applied lattice focusing, space-charge defocusing, and thermal defocusing forces. Recently, an iterative numerical method was developed (Lund, Chilton, and Lee, Efficient computation of matched solutions to the KV envelope equations for periodic focusing lattices, Physical Review Special Topics-Accelerators and Beams 9, 064201 2006) to generate matching conditions in a highly flexible, convergent, and fail-safe manner. This method is extended and implemented in the WARP code as a Python package to vastly ease the setup of detailed simulations. In particular, the Python package accommodates any linear applied lattice focusing functions without skew coupling, and a more general set of beam parameter specifications than its predecessor. Lattice strength iteration tools were added to facilitate the implementation of problems with specific applied focusing strengths.
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh; Servant, Géraldine
2005-02-01
In the past year, a new non-supersymmetric framework for electroweak symmetry breaking (with or without Higgs) involving SU(2)L × SU(2)R × U(1)B-L in higher dimensional warped geometry has been suggested. In this work, we embed this gauge structure into a GUT such as SO(10) or Pati Salam. We showed recently (in hep-ph/0403143) that in a warped GUT, a stable Kaluza Klein fermion can arise as a consequence of imposing proton stability. Here, we specify a complete realistic model where this particle is a weakly interacting right-handed neutrino, and present a detailed study of this new dark matter candidate, providing relic density and detection predictions. We discuss phenomenological aspects associated with the existence of other light ({\\lesssim }\\mathrm {TeV} ) KK fermions (related to the neutrino), whose lightness is a direct consequence of the top quark's heaviness. The AdS/CFT interpretation of this construction is also presented. Most of our qualitative results do not depend on the nature of the breaking of the electroweak symmetry provided that it happens near the TeV brane.
Novel methods in the Particle-In-Cell accelerator Code-Framework Warp
Vay, J-L; Grote, D. P.; Cohen, R. H.; Friedman, A.
2012-12-26
The Particle-In-Cell (PIC) Code-Framework Warp is being developed by the Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) to guide the development of accelerators that can deliver beams suitable for high-energy density experiments and implosion of inertial fusion capsules. It is also applied in various areas outside the Heavy Ion Fusion program to the study and design of existing and next-generation high-energy accelerators, including the study of electron cloud effects and laser wakefield acceleration for example. This study presents an overview of Warp's capabilities, summarizing recent original numerical methods that were developed by the HIFS-VNL (including PIC with adaptive mesh refinement, a large-timestep 'drift-Lorentz' mover for arbitrarily magnetized species, a relativistic Lorentz invariant leapfrog particle pusher, simulations in Lorentz-boosted frames, an electromagnetic solver with tunable numerical dispersion and efficient stride-based digital filtering), with special emphasis on the description of the mesh refinement capability. In addition, selected examples of the applications of the methods to the abovementioned fields are given.
A nonlinear theory for spinning anisotropic beams using restrained warping functions
NASA Technical Reports Server (NTRS)
Ie, C. A.; Kosmatka, J. B.
1993-01-01
A geometrically nonlinear theory is developed for spinning anisotropic beams having arbitrary cross sections. An assumed displacement field is developed using the standard 3D kinematics relations to describe the global beam behavior supplemented with an additional field that represents the local deformation within the cross section and warping out of the cross section plane. It is assumed that the magnitude of this additional field is directly proportional to the local stress resultants. In order to take into account the effects of boundary conditions, a restraining function is introduced. This function plays the role of reducing the amount of free warping deformation throughout the field due to the restraint of the cross section(s) at the end(s) of the beam, e.g., in the case of a cantilever beam. Using a developed ordering scheme, the nonlinear strains are calculated to the third order. The FEM is developed using the weak form variational formulation. Preliminary interesting numerical results have been obtained that indicate the role of the restraining function in the case of a cantilever beam with circular cross section. These results are for the cases of a tip displacement (static) and free vibration studies for both isotropic and anisotropic materials with varied fiber orientations.
Scalar field localization on 3-branes placed at a warped resolved conifold
Silva, J. E. G.; Almeida, C. A. S.
2011-10-15
We have studied the localization of a scalar field on a 3-brane embedded in a six-dimensional warped bulk of the form M{sub 4}xC{sub 2}, where M{sub 4} is a 3-brane and C{sub 2} is a 2-cycle of a six-dimensional resolved conifold C{sub 6} over a T{sup 1,1} space. Since the resolved conifold is singularity-free in r=0 depending on a resolution parameter a, we have analyzed the behavior of the localization of a scalar field when we vary the resolution parameter. On one hand, this enables us to study the effects that a singularity has on the field. On the other hand we can use the resolution parameter as a fine-tuning between the bulk Planck mass and 3-brane Planck mass and so it opens a new perspective to extend the hierarchy problem. Using a linear and a nonlinear warp factor, we have found that the massive and massless modes are trapped to the brane even in the singular cone (a{ne}0). We have also compared the results obtained in this geometry and those obtained in other six-dimensional models, such as stringlike geometry and cigarlike universe geometry.
Gravitational backreaction of anti-D branes in the warped compactification
NASA Astrophysics Data System (ADS)
Koyama, Kayoko; Koyama, Kazuya
2005-09-01
We derive a low-energy effective theory for gravity with anti-D branes, which are essential to get de Sitter solutions in the type IIB string-warped compactification, by taking account of gravitational backreactions of anti-D branes. In order to see the effects of the self-gravity of anti-D branes, a simplified model is studied where a five-dimensional anti-de Sitter (AdS) spacetime is realized by the bulk cosmological constant and the 5-form flux, and anti-D branes are coupled to the 5-form field by Chern Simon terms. The AdS spacetime is truncated by introducing UV and IR cut-off branes like the Randall Sundrum model. We derive an effective theory for gravity on the UV brane and reproduce the familiar result that the tensions of the anti-D branes give potentials suppressed by the fourth power of the warp factor at the location of the anti-D branes. However, in this simplified model, the potential energy never inflates the UV brane, although the anti-D branes are inflating. The UV brane is dominated by dark radiation coming from the projection of the five-dimensional Weyl tensor, unless the moduli fields for the anti-D branes are stabilized. We comment on the possibility of avoiding this problem in a realistic string theory compactification.
A Geometry-Driven Optical Flow Warping for Spatial Normalization of Cortical Surfaces
Tosun, Duygu; Prince, Jerry L.
2008-01-01
Spatial normalization is frequently used to map data to a standard coordinate system by removing inter-subject morphological differences, thereby allowing for group analysis to be carried out. The work presented in this paper is motivated by the need for an automated cortical surface normalization technique that will automatically identify homologous cortical landmarks and map them to the same coordinates on a standard manifold. The geometry of a cortical surface is analyzed using two shape measures that distinguish the sulcal and gyral regions in a multi-scale framework. A multichannel optical flow warping procedure aligns these shape measures between a reference brain and a subject brain, creating the desired normalization. The partial differential equation that carries out the warping is implemented in a Euclidean framework in order to facilitate a multi-resolution strategy, thereby permitting large deformations between the two surfaces. The technique is demonstrated by aligning 33 normal cortical surfaces and showing both improved structural alignment in manually labeled sulci and improved functional alignment in positron emission tomography data mapped to the surfaces. A quantitative comparison between our proposed surface-based spatial normalization method and a leading volumetric spatial normalization method is included to show that the surface-based spatial normalization performs better in matching homologous cortical anatomies. PMID:19033090
Lecture versus DVD and Attitude Change toward Female Masturbation
ERIC Educational Resources Information Center
Keels, Megan; Lee, Zoey; Knox, David; Wilson, Ken
2013-01-01
Four-hundred and ninety eight female undergraduate students at a large southeastern university participated in a study to assess how lecture versus DVD format affected attitude change towards female masturbation. All groups were given a pre and post test to assess masturbatory attitudes. Group 1 experienced a masturbation lecture. Group 2…
Powerpoint and Pedagogy: Maintaining Student Interest in University Lectures
ERIC Educational Resources Information Center
Clark, Jennifer
2008-01-01
This author discusses the relationship between the use of presentation software and the maintenance of student interest in university lectures. The evidence of surveyed university students suggests that PowerPoint, used as a presentation tool in university lectures, is pedagogically effective only while it provides variety and stimulates interest…
The Virtual Lecture Hall: Utilisation, Effectiveness and Student Perceptions
ERIC Educational Resources Information Center
Cramer, Kenneth M.; Collins, Kandice R.; Snider, Don; Fawcett, Graham
2007-01-01
We presently introduce the Virtual Lecture Hall (VLH), an instructional computer-based platform for delivering Microsoft PowerPoint slides threaded with audio clips for later review. There were 839 male and female university students enrolled in an introductory psychology class who had access to review class lectures via the VLH. This tool was…
Curriculum Orientation of Lecturers in Teacher Training College in Malaysia
ERIC Educational Resources Information Center
Salleh, Halimatussaadiah; Hamdan, Abdul Rahim; Yahya, Fauziah; Jantan, Hafsah
2015-01-01
Curriculum development in teacher training college can be facilitated by indentifying the lecturers curriculum orientation. This study focuses on curriculum orientation of lecturer in Teacher Training Colleges (TTC) in Malaysia. Data were collected through questionnaire survey using the Curriculum Orientation Inventory, an instrument developed by…
Next-Generation Educational Technology versus the Lecture.
ERIC Educational Resources Information Center
Foreman, Joel
2003-01-01
Addresses concerns related to the replacement of large lecture courses by immersive digital environments with similarities to advanced videogames. Explains why the large lecture format deserves replacement, reviews the field of game-based learning, and illustrates the approach in the example of an introductory psychology class. (SLD)
Group Assessments: Dilemmas Facing Lecturers in Multicultural Tertiary Classrooms
ERIC Educational Resources Information Center
Strauss, Pat; U, Alice
2007-01-01
"Group is good, and group is good for curing all social ills" was the cynical observation of one of the lecturers in this study. Her comment reflects the uneasiness of lecturers at tertiary institutions with the notion that the educational advantages of group assessments far outweigh the disadvantages, and that such an approach promotes the…
Student Perception of Topic Difficulty: Lecture Capture in Higher Education
ERIC Educational Resources Information Center
McCunn, Patrick; Newton, Genevieve
2015-01-01
Perception of topic difficulty is a likely predictor of lecture capture video use, as student perception of difficulty has been shown to affect a variety of outcomes in academic settings. This study measured the relationship between perceived difficulty and the use of lecture capture technology in a second year biochemistry course while…
Lecturer's Gender and Their Valuation of Student Evaluation of Teaching
ERIC Educational Resources Information Center
Atek, Engku Suhaimi Engku; Salim, Hishamuddin; Halim, Zulazhan Ab.; Jusoh, Zailani; Yusuf, Mohd Ali Mohd
2015-01-01
Student evaluation of teaching (SET) is carried out every semester at Malaysian universities and lecturers are evaluated based on student ratings. But very little is researched about what lecturers actually think about SET and whether it serves any meaningful purpose at all. This quantitative study involving six public universities on the East…
The Lectures Are Recorded, so Why Go to Class?
ERIC Educational Resources Information Center
Young, Jeffrey R.
2008-01-01
When video recordings of Ravi Janardan's computer-science course at the University of Minnesota-Twin Cities first went online, the students loved it. Instead of dragging themselves out of bed for the 8 a.m. lectures, many started skipping classes and watching the recordings instead. Recording lectures is becoming more and more common, and many…
"Just Remember This": Lexicogrammatical Relevance Markers in Lectures
ERIC Educational Resources Information Center
Deroey, Katrien L. B.; Taverniers, Miriam
2012-01-01
This paper presents a comprehensive overview of lexicogrammatical devices which highlight important or relevant points in lectures. Despite the established usefulness of discourse organizational cues for lecture comprehension and note-taking, very little is known about the marking of relevance in this genre. The current overview of…
Reflections on the Lecture: Outmoded Medium or Instrument of Inspiration?
ERIC Educational Resources Information Center
Jones, Steve E.
2007-01-01
The traditional, didactic lecture is under attack from diverse quarters. With its origins rooted in the emergence of orality, the lecture now stands as only one of a plethora of educational communication tools, and has been subject to criticism particularly by constructivists for failing to deliver deep and effective learning experiences. This…
Explicit Constructivism: A Missing Link in Ineffective Lectures?
ERIC Educational Resources Information Center
Prakash, E. S.
2010-01-01
This study tested the possibility that interactive lectures explicitly based on activating learners' prior knowledge and driven by a series of logical questions might enhance the effectiveness of lectures. A class of 54 students doing the respiratory system course in the second year of the Bachelor of Medicine and Bachelor of Surgery program in my…
Lecture Recording: Structural and Symbolic Information vs. Flexibility of Presentation
ERIC Educational Resources Information Center
Stolzenberg, Daniel; Pforte, Stefan
2007-01-01
Rapid eLearning is an ongoing trend which enables flexible and cost-effective creation of learning materials. Especially, lecture recording has turned out to be a lightweight method particularly suited for existing lectures and blended learning strategies. In order to not only sequentially play back but offer full fledged navigation, search and…
Level of Perceived Stress Among Lectures in Nigerian Universities
ERIC Educational Resources Information Center
Ofoegbu, Felicia; Nwadiani, Mon
2006-01-01
The purpose of the study was to provide empirical evidence on the level of stress among lecturers in Nigerian universities. On the whole eight universities were used for the study. A sample of 228 (123 male and 105 female) lecturers was selected according to the variables of age, sex, marital status, experience, domicile, areas of specialization,…
More Professors Could Share Lectures Online: But Should They?
ERIC Educational Resources Information Center
Young, Jeffrey R.
2010-01-01
In this article, the author discusses the issues surrounding the production of lecture videos by professors and administrators which are free to the world. Professors across the country are now wrestling with this issue. More and more colleges have installed microphones or cameras in lecture halls and bought easy-to-use software to get lecture…
45 CFR 73.735-706 - Teaching, lecturing, and speechmaking.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 45 Public Welfare 1 2010-10-01 2010-10-01 false Teaching, lecturing, and speechmaking. 73.735-706 Section 73.735-706 Public Welfare DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL ADMINISTRATION STANDARDS OF CONDUCT Outside Activities § 73.735-706 Teaching, lecturing, and speechmaking. (a) Employees are encouraged to engage in teaching...
Role of Physics Lecture Demonstrations in Conceptual Learning
ERIC Educational Resources Information Center
Miller, Kelly; Lasry, Nathaniel; Chu, Kelvin; Mazur, Eric
2013-01-01
Previous research suggests that students; prior knowledge can interfere with how they observe and remember lecture demonstrations. We measured students' prior knowledge in introductory mechanics and electricity and magnetism at two large universities. Students were then asked to predict the outcome of lecture demonstrations. We compare…