The ghost propagator in Coulomb gauge

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

Watson, P.; Reinhardt, H.

2011-05-23

We present results for a numerical study of the ghost propagator in Coulomb gauge whereby lattice results for the spatial gluon propagator are used as input to solving the ghost Dyson-Schwinger equation. We show that in order to solve completely, the ghost equation must be supplemented by a boundary condition (the value of the inverse ghost propagator dressing function at zero momentum) which determines if the solution is critical (zero value for the boundary condition) or subcritical (finite value). The various solutions exhibit a characteristic behavior where all curves follow the same (critical) solution when going from high to lowmore » momenta until 'forced' to freeze out in the infrared to the value of the boundary condition. The boundary condition can be interpreted in terms of the Gribov gauge-fixing ambiguity; we also demonstrate that this is not connected to the renormalization. Further, the connection to the temporal gluon propagator and the infrared slavery picture of confinement is discussed.« less

Effects of Low Anisotropy on Generalized Ghost Dark Energy in Galileon Gravity

NASA Astrophysics Data System (ADS)

Hossienkhani, H.; Fayaz, V.; Jafari, A.; Yousefi, H.

2018-04-01

The definition of the Galileon gravity form is extended to the Brans-Dicke theory. Given, the framework of the Galileon theory, the generalized ghost dark energy model in an anisotropic universe is investigated. We study the cosmological implications of this model. In particular, we obtain the equation of state and the deceleration parameters and a differential equation governing the evolution of this dark energy in Bianchi type I model. We also probe observational constraints by using the latest observational data on the generalized ghost dark energy models as the unification of dark matter and dark energy. In order to do so, we focus on observational determinations of the Hubble expansion rate (namely, the expansion history) H(z). As a result, we show the influence of the anisotropy (although low) on the evolution of the universe in the statefinder diagrams for Galileon gravity.

Dark matter as a ghost free conformal extension of Einstein theory

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

Barvinsky, A.O., E-mail: barvin@td.lpi.ru

We discuss ghost free models of the recently suggested mimetic dark matter theory. This theory is shown to be a conformal extension of Einstein general relativity. Dark matter originates from gauging out its local Weyl invariance as an extra degree of freedom which describes a potential flow of the pressureless perfect fluid. For a positive energy density of this fluid the theory is free of ghost instabilities, which gives strong preference to stable configurations with a positive scalar curvature and trace of the matter stress tensor. Instabilities caused by caustics of the geodesic flow, inherent in this model, serve asmore » a motivation for an alternative conformal extension of Einstein theory, based on the generalized Proca vector field. A potential part of this field modifies the inflationary stage in cosmology, whereas its rotational part at the post inflationary epoch might simulate rotating flows of dark matter.« less

Cosmology with a light ghost

NASA Astrophysics Data System (ADS)

Ivanov, Mikhail M.; Tokareva, Anna A.

2016-12-01

We study the creation and evolution of cosmological perturbations in renormalizable quadratic gravity with a Weyl term. We adopt a prescription that implies the stability of the vacuum at the price of introducing a massive spin-two ghost state, leading to the loss of unitarity. The theory may still be predictive regardless the interpretation of non-unitary processes provided that their rate is negligible compared to the Universe expansion rate. This implies that the ghost is effectively stable. In such a setup, there are two scalar degrees of freedom excited during inflation. The first one is the usual curvature perturbation whose power spectrum appears to coincide with that of single-field inflation. The second one is a scalar component of the ghost encoded in the shift vector of the metric in the uniform inflaton gauge. The amplitudes of primordial tensor and vector perturbations are strongly suppressed. After inflation the ghost field starts to oscillate and its energy density shortly becomes dominant in the Universe. For all ghost masses allowed by laboratory constraints ghosts should have ``overclosed'' the Universe at temperatures higher than that of primordial nucleosynthesis. Thus, the model with the light Weyl ghost is ruled out.

Cosmology with a light ghost

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

Ivanov, Mikhail M.; Tokareva, Anna A., E-mail: mikhail.ivanov@cern.ch, E-mail: anna.tokareva@epfl.ch

2016-12-01

We study the creation and evolution of cosmological perturbations in renormalizable quadratic gravity with a Weyl term. We adopt a prescription that implies the stability of the vacuum at the price of introducing a massive spin-two ghost state, leading to the loss of unitarity. The theory may still be predictive regardless the interpretation of non-unitary processes provided that their rate is negligible compared to the Universe expansion rate. This implies that the ghost is effectively stable. In such a setup, there are two scalar degrees of freedom excited during inflation. The first one is the usual curvature perturbation whose powermore » spectrum appears to coincide with that of single-field inflation. The second one is a scalar component of the ghost encoded in the shift vector of the metric in the uniform inflaton gauge. The amplitudes of primordial tensor and vector perturbations are strongly suppressed. After inflation the ghost field starts to oscillate and its energy density shortly becomes dominant in the Universe. For all ghost masses allowed by laboratory constraints ghosts should have ''overclosed'' the Universe at temperatures higher than that of primordial nucleosynthesis. Thus, the model with the light Weyl ghost is ruled out.« less

Identification of ghost artifact using texture analysis in pediatric spinal cord diffusion tensor images.

PubMed

Alizadeh, Mahdi; Conklin, Chris J; Middleton, Devon M; Shah, Pallav; Saksena, Sona; Krisa, Laura; Finsterbusch, Jürgen; Faro, Scott H; Mulcahey, M J; Mohamed, Feroze B

2018-04-01

Ghost artifacts are a major contributor to degradation of spinal cord diffusion tensor images. A multi-stage post-processing pipeline was designed, implemented and validated to automatically remove ghost artifacts arising from reduced field of view diffusion tensor imaging (DTI) of the pediatric spinal cord. A total of 12 pediatric subjects including 7 healthy subjects (mean age=11.34years) with no evidence of spinal cord injury or pathology and 5 patients (mean age=10.96years) with cervical spinal cord injury were studied. Ghost/true cords, labeled as region of interests (ROIs), in non-diffusion weighted b0 images were segmented automatically using mathematical morphological processing. Initially, 21 texture features were extracted from each segmented ROI including 5 first-order features based on the histogram of the image (mean, variance, skewness, kurtosis and entropy) and 16s-order feature vector elements, incorporating four statistical measures (contrast, correlation, homogeneity and energy) calculated from co-occurrence matrices in directions of 0°, 45°, 90° and 135°. Next, ten features with a high value of mutual information (MI) relative to the pre-defined target class and within the features were selected as final features which were input to a trained classifier (adaptive neuro-fuzzy interface system) to separate the true cord from the ghost cord. The implemented pipeline was successfully able to separate the ghost artifacts from true cord structures. The results obtained from the classifier showed a sensitivity of 91%, specificity of 79%, and accuracy of 84% in separating the true cord from ghost artifacts. The results show that the proposed method is promising for the automatic detection of ghost cords present in DTI images of the spinal cord. This step is crucial towards development of accurate, automatic DTI spinal cord post processing pipelines. Copyright © 2017 Elsevier Inc. All rights reserved.

Metabolomics reveals the key role of oxygen metabolism in the heat susceptibility of an alpine dwelling ghost moth, Thitarodes xiaojinensis (Lepidoptera: Hepialidae).

PubMed

Zhu, Wei; Meng, Qian; Zhang, Huan; Wang, Meng-Long; Li, Xuan; Wang, Hong-Tuo; Zhou, Gui-Ling; Miao, Lin; Qin, Qi-Lian; Zhang, Ji-Hong

2018-05-23

Ghost moths inhabiting the alpine meadows of the Tibetan Plateau are cold-adapted stenothermal organisms that are susceptible to heat (dead within 7 days of 27 °C exposure). Exploring the metabolic basis of their heat susceptibility would extend our understanding of the thermal biology of alpine dwelling invertebrates. Here, gas chromatography-mass spectrometry-based metabolomics was combined with physiological and transcriptional approaches to determine the metabolic mechanisms of heat susceptibility in Thitarodes xiaojinensis larvae. The metabolomics results showed that 27 °C heat stress impaired the Krebs cycle and lipolysis in T. xiaojinensis larvae, as demonstrated by the accumulation of intermediary metabolites. In addition, carbohydrate reserves were highly and exclusively consumed, and an anaerobic product, lactate, accumulated. This evidence suggested a strong reliance on glycolysis to generate energy anaerobically. The respiration rate and enzymatic activity test results indicated a deficiency in O 2 metabolism; in addition, the Krebs cycle capacity was not lowered, and the metabolic flux through aerobic pathways was limited. These findings were further supported by the occurrence of hypoxia symptoms in midgut mitochondria (vacuolation and swelling) and increased transcription of hypoxia-induced factor 1-α. Overall, heat stress caused O 2 limitation and depressed the overall intensity of aerobic metabolism in ghost moths, and less efficient anaerobic glycolysis was activated to sustain their energy supply. After the carbohydrates became limited, the energy supply became deficient. Our study presented a comprehensive metabolic explanation for the heat susceptibility of ghost moths and revealed the relationship between O 2 metabolism and heat susceptibility in these larvae. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

QCD nature of dark energy at finite temperature: Cosmological implications

NASA Astrophysics Data System (ADS)

Azizi, K.; Katırcı, N.

2016-05-01

The Veneziano ghost field has been proposed as an alternative source of dark energy, whose energy density is consistent with the cosmological observations. In this model, the energy density of the QCD ghost field is expressed in terms of QCD degrees of freedom at zero temperature. We extend this model to finite temperature to search the model predictions from late time to early universe. We depict the variations of QCD parameters entering the calculations, dark energy density, equation of state, Hubble and deceleration parameters on temperature from zero to a critical temperature. We compare our results with the observations and theoretical predictions existing at different eras. It is found that this model safely defines the universe from quark condensation up to now and its predictions are not in tension with those of the standard cosmology. The EoS parameter of dark energy is dynamical and evolves from -1/3 in the presence of radiation to -1 at late time. The finite temperature ghost dark energy predictions on the Hubble parameter well fit to those of Λ CDM and observations at late time.

Ghost Dark Energy with Sign-changeable Interaction Term

NASA Astrophysics Data System (ADS)

Zadeh, M. Abdollahi; Sheykhi, A.; Moradpour, H.

2017-11-01

Regarding the Veneziano ghost of QCD and its generalized form, we consider a Friedmann-Robertson-Walker (FRW) universe filled by a pressureless matter and a dark energy component interacting with each other through a mutual sign-changeable interaction of positive coupling constant. Our study shows that, at the late time, for the deceleration parameter we have q → -1, while the equation of state parameter of the interacting ghost dark energy (GDE) does not cross the phantom line, namely ω D ≥ -1. We also extend our study to the generalized ghost dark energy (GGDE) model and show that, at late time, the equation of state parameter of the interacting GGDE also respects the phantom line in both flat and non-flat universes. Moreover, we find out that, unlike the non-flat universe, we have q → -1 at late time for flat FRW universe. In order to make the behavior of the underlying models more clear, the deceleration parameter q as well as the equation of state parameter w D for flat and closed universes have been plotted against the redshift parameter, z. All of the studied cases admit a transition in the expansion history of universe from a deceleration phase to an accelerated one around z ≈ 0.6.

Activation of chicken bone marrow-derived dendritic cells induced by a Salmonella Enteritidis ghost vaccine candidate.

PubMed

Kamble, N M; Jawale, C V; Lee, J H

2016-10-01

Bacterial Ghost-based vaccine development has been applied to a variety of gram-negative bacteria. Developed Salmonella Enteritidis (S. Enteritidis) ghost are promising vaccine candidates because of their immunogenic and enhanced biosafety potential. In this study, we aimed to evaluate the immunostimulatory effect of a S. Enteritidis ghost vaccine on the maturation of chicken bone marrow-derived dendritic cells (chBM-DCs) in vitro The immature chBM-DCs were stimulated with S. Enteritidis ghost vaccine candidate. The vaccine efficiently stimulated maturation events in chBM-DCs, indicated by up-regulated expression of CD40, CD80, and MHC-II molecules. Immature BM-DCs responded to stimulation with S. Enteritidis ghost by increased expression of IL-6 and IL-12p40 cytokines. Also, S. Enteritidis ghost stimulated chBM-DCs induced the significant expression of IFN-γ and IL-2 in co-cultured autologous CD4+ T cells. In conclusion, our data suggest that S. Enteritidis ghost vaccine candidate is capable of activating and interacting with chBM-DCs. The results from current study may help for rational designing of Salmonella ghost based heterologous antigen delivery platforms to dendritic cells. © 2016 Poultry Science Association Inc.

Observational viability and stability of nonlocal cosmology

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

Deser, S.; Woodard, R.P., E-mail: deser@brandeis.edu, E-mail: woodard@phys.ufl.edu

2013-11-01

We show that the nonlocal gravity models, proposed to explain current cosmic acceleration without dark energy, pass two essential tests: first, they can be defined so as not to alter the, observationally correct, general relativity predictions for gravitationally bound systems. Second, they are stable, ghost-free, with no additional excitations beyond those of general relativity. In this they differ from their, ghostful, localized versions. The systems' initial value constraints are the same as in general relativity, and our nonlocal modifications never convert the original gravitons into ghosts.

Ghost Imaging without Discord

PubMed Central

Shapiro, Jeffrey H.; Venkatraman, Dheera; Wong, Franco N. C.

2013-01-01

Ragy and Adesso argue that quantum discord is involved in the formation of a pseudothermal ghost image. We show that quantum discord plays no role in spatial light modulator ghost imaging, i.e., ghost-image formation based on structured illumination realized with laser light that has undergone spatial light modulation by the output from a pseudorandom number generator. Our analysis thus casts doubt on the degree to which quantum discord is necessary for ghost imaging. PMID:23673426

THE PROTEIN COATS OR "GHOSTS" OF COLIPHAGE T2

PubMed Central

Herriott, Roger M.; Barlow, James L.

1957-01-01

A method of preparing the protein coats or ghosts of phage T2 is described along with proof that the lytic action is a property of the ghost. An assay based on the lytic action toward host cells has been developed which permits a rapid evaluation of the number of ghosts with a reliability of ±15 per cent. The antigenic and certain physicochemical properties of the ghost have been determined. PMID:13428990

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

Yan, Guanghua, E-mail: yan@ufl.edu; Li, Jonathan; Huang, Yin

Purpose: To propose a simple model to explain the origin of ghost markers in marker-based optical tracking systems (OTS) and to develop retrospective strategies to detect and eliminate ghost markers. Methods: In marker-based OTS, ghost markers are virtual markers created due to the cross-talk between the two camera sensors, which can lead to system execution failure or inaccuracy in patient tracking. As a result, the users have to limit the number of markers and avoid certain marker configurations to reduce the chances of ghost markers. In this work, the authors propose retrospective strategies to detect and eliminate ghost markers. Themore » two camera sensors were treated as mathematical points in space. The authors identified the coplanar within limit (CWL) condition as the necessary condition for ghost marker occurrence. A simple ghost marker detection method was proposed based on the model. Ghost marker elimination was achieved through pattern matching: a ghost marker-free reference set was matched with the optical marker set observed by the OTS; unmatched optical markers were eliminated as either ghost markers or misplaced markers. The pattern matching problem was formulated as a constraint satisfaction problem (using pairwise distances as constraints) and solved with an iterative backtracking algorithm. Wildcard markers were introduced to address missing or misplaced markers. An experiment was designed to measure the sensor positions and the limit for the CWL condition. The ghost marker detection and elimination algorithms were verified with samples collected from a five-marker jig and a nine-marker anthropomorphic phantom, rotated with the treatment couch from −60° to +60°. The accuracy of the pattern matching algorithm was further validated with marker patterns from 40 patients who underwent stereotactic body radiotherapy (SBRT). For this purpose, a synthetic optical marker pattern was created for each patient by introducing ghost markers, marker position uncertainties, and marker displacement. Results: The sensor positions and the limit for the CWL condition were measured with excellent reproducibility (standard deviation ≤ 0.39 mm). The ghost marker detection algorithm had perfect detection accuracy for both the jig (1544 samples) and the anthropomorphic phantom (2045 samples). Pattern matching was successful for all samples from both phantoms as well as the 40 patient marker patterns. Conclusions: The authors proposed a simple model to explain the origin of ghost markers and identified the CWL condition as the necessary condition for ghost marker occurrence. The retrospective ghost marker detection and elimination algorithms guarantee complete ghost marker elimination while providing the users with maximum flexibility in selecting the number of markers and their configuration to meet their clinic needs.« less

Coulomb gauge ghost Dyson-Schwinger equation

NASA Astrophysics Data System (ADS)

Watson, P.; Reinhardt, H.

2010-12-01

A numerical study of the ghost Dyson-Schwinger equation in Coulomb gauge is performed and solutions for the ghost propagator found. As input, lattice results for the spatial gluon propagator are used. It is shown that in order to solve completely, the equation must be supplemented by a nonperturbative boundary condition (the value of the inverse ghost propagator dressing function at zero momentum), which determines if the solution is critical (zero value for the boundary condition) or subcritical (finite value). The various solutions exhibit a characteristic behavior where all curves follow the same (critical) solution when going from high to low momenta until forced to freeze out in the infrared to the value of the boundary condition. The renormalization is shown to be largely independent of the boundary condition. The boundary condition and the pattern of the solutions can be interpreted in terms of the Gribov gauge-fixing ambiguity. The connection to the temporal gluon propagator and the infrared slavery picture of confinement is explored.

Ghost tablet in feces.

PubMed

Iwamuro, Masaya; Morishita, Yosuke; Urata, Haruo; Okada, Hiroyuki

2017-12-01

Recently, we encountered a female patient who identified the presence of a ghost tablet in her fecal matter. Interestingly, although the patient was prescribed potassium chloride capsules, elemental composition analysis by energy-dispersive X-ray spectroscopy was unable to detect the presence of either potassium or chloride in the fecal tablet remnant.

Haunted manuscripts: ghost authorship in the medical literature.

PubMed

Ngai, Stephanie; Gold, Jennifer L; Gill, Sudeep S; Rochon, Paula A

2005-01-01

Ghost authorship occurs when an individual who contributed substantially to a manuscript is not named in the byline or acknowledgments. Ghost authors may be employed by industry to prepare clinical trial results for publication. An expert is then "hired" as author so as to lend an air of credibility and neutrality to the manuscript. Ghost authorship is difficult to detect, and most articles that have been identified as ghostwritten were revealed as such only after investigative work by lawyers, journalists, or scientists. Ghost authorship is ethically questionable in that it may be used to mask conflicts of interest with industry. As it has been demonstrated that industry sponsorship of clinical trials may be associated with outcomes favorable to industry, this is problematic. Evidence-based medicine requires that clinical decisions be based on empirical evidence published in peer-reviewed medical journals. If physicians base their decisions on dubious research data, this can have negative consequences for patients. Ghost authorship also compromises academic integrity. A "film credit" concept of authority is one solution to the problems posed by ghost authorship. Other approaches have been taken by the United Kingdom and Denmark. A solution is necessary, as the relationship between authorship and accountability must be maintained.

Comparative studies on osmosis based encapsulation of sodium diclofenac in porcine and outdated human erythrocyte ghosts.

PubMed

Bukara, Katarina; Drvenica, Ivana; Ilić, Vesna; Stančić, Ana; Mišić, Danijela; Vasić, Borislav; Gajić, Radoš; Vučetić, Dušan; Kiekens, Filip; Bugarski, Branko

2016-12-20

The objective of our study was to develop controlled drug delivery system based on erythrocyte ghosts for amphiphilic compound sodium diclofenac considering the differences between erythrocytes derived from two readily available materials - porcine slaughterhouse and outdated transfusion human blood. Starting erythrocytes, empty erythrocyte ghosts and diclofenac loaded ghosts were compared in terms of the encapsulation efficiency, drug releasing profiles, size distribution, surface charge, conductivity, surface roughness and morphology. The encapsulation of sodium diclofenac was performed by an osmosis based process - gradual hemolysis. During this process sodium diclofenac exerted mild and delayed antihemolytic effect and increased potassium efflux in porcine but not in outdated human erythrocytes. FTIR spectra revealed lack of any membrane lipid disorder and chemical reaction with sodium diclofenac in encapsulated ghosts. Outdated human erythrocyte ghosts with detected nanoscale damages and reduced ability to shrink had encapsulation efficiency of only 8%. On the other hand, porcine erythrocyte ghosts had encapsulation efficiency of 37% and relatively slow drug release rate. More preserved structure and functional properties of porcine erythrocytes related to their superior encapsulation and release performances, define them as more appropriate for the usage in sodium diclofenac encapsulation process. Copyright © 2016 Elsevier B.V. All rights reserved.

Energy Flux Positivity and Unitarity in Conformal Field Theories

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

Kulaxizi, Manuela; Parnachev, Andrei

2011-01-07

We show that in most conformal field theories the condition of the energy flux positivity, proposed by Hofman and Maldacena, is equivalent to the absence of ghosts. At finite temperature and large energy and momenta, the two-point functions of the stress energy tensor develop light like poles. The residues of the poles can be computed, as long as the only spin-two conserved current, which appears in the stress energy tensor operator-product expansion and acquires a nonvanishing expectation value at finite temperature, is the stress energy tensor. The condition for the residues to stay positive and the theory to remain ghost-freemore » is equivalent to the condition of positivity of energy flux.« less

Methods for reducing ghost rays on the Wolter-I focusing figures of the FOXSI rocket payload

NASA Astrophysics Data System (ADS)

Buitrago-Casas, Juan Camilo; Glesener, Lindsay; Christe, Steven; Ramsey, Brian; Elsner, Ronald; Courtade, Sasha; Vievering, Juliana; Subramania, Athiray; Krucker, Sam; Bale, Stuart

2017-08-01

In high energy solar astrophysics, imaging hard X-rays by direct focusing offers higher dynamic range and greater sensitivity compared to past techniques that used indirect imaging. The Focusing Optics X-ray Solar Imager (FOXSI) is a sounding rocket payload which uses seven sets of nested Wolter-I figured mirrors that, together with seven high-sensitive semiconductor detectors, observes the Sun in hard X-rays by direct focusing. The FOXSI rocket has successfully flown twice and is funded to fly a third time in summer 2018.The Wolter-I geometry consists of two consecutive mirrors, one paraboloid, and one hyperboloid, that reflect photons at grazing angles. Correctly focused X-rays reflect twice, once per mirror segment. For extended sources, like the Sun, off-axis photons at certain incident angles can reflect on only one mirror and still reach the focal plane, generating a pattern of single-bounce photons, or ‘ghost rays’ that can limit the sensitivity of the observation of focused X-rays. Understanding and cutting down the ghost rays on the FOXSI optics will maximize the instrument’s sensitivity of the solar faintest sources for future flights. We present an analysis of the FOXSI ghost rays based on ray-tracing simulations, as well as the effectiveness of different physical strategies to reduce them.

Anisotropic ghost dark energy cosmological model with hybrid expansion law

NASA Astrophysics Data System (ADS)

Mahanta, Chandra Rekha; Sarma, Nitin

2017-11-01

In this paper, we study the anisotropic Bianchi type-VI0 metric filled with dark matter and anisotropic ghost dark energy. We have solved the Einstein's field equations by considering hybrid expansion law (HEL) for the average scale factor. It is found that at later times the universe becomes spatially homogeneous, isotropic and flat. From a state finder diagnosis, it is found that our model is having similar behavior like ɅCDM model at late phase of cosmic time.

Two-wavelength ghost imaging through atmospheric turbulence.

PubMed

Shi, Dongfeng; Fan, Chengyu; Zhang, Pengfei; Shen, Hong; Zhang, Jinghui; Qiao, Chunhong; Wang, Yingjian

2013-01-28

Recent work has indicated that ghost imaging might find useful application in standoff sensing where atmospheric turbulence is a serious problem. There has been theoretical study of ghost imaging in the presence of turbulence. However, most work has addressed signal-wavelength ghost imaging. Two-wavelength ghost imaging through atmospheric turbulence is theoretically studied in this paper. Based on the extended Huygens-Fresnel integral, the analytical expressions describing atmospheric turbulence effects on the point spread function (PSF) and field of view (FOV) are derived. The computational case is also reported.

Biological amine transport in chromaffin ghosts. Coupling to the transmembrane proton and potential gradients.

PubMed

Johnson, R G; Pfister, D; Carty, S E; Scarpa, A

1979-11-10

The effect of the transmembrane proton gradient (delta pH) and potential gradient (delta psi) upon the rate and extent of amine accumulation was investigated in chromaffin ghosts. The chromaffin ghosts were formed by hypo-osmotic lysis of isolated bovine chromaffin granules and extensive dialysis in order to remove intragranular binding components and dissipate the endogenous electrochemical gradients. Upon ATP addition to suspensions of chromaffin ghosts, a transmembrane proton gradient alone, a transmembrane gradient alone, or both, could be established, depending upon the compositions of the media in which the ghosts were formed and resuspended. When chloride was present in the medium, addition of ATP resulted in the generation of a transmembrane proton gradient, acidic inside of 1 pH unit (measured by [14C]methylamine distribution), and no transmembrane potential (measured by [14C]-thiocyanate distribution). When ATP was added to chromaffin ghosts suspended in a medium in which chloride was substituted by isethionate, a transmembrane potential, inside positive, of 45 mV and no transmembrane proton gradient, was measured. In each medium, the addition of agents known to affect proton or potential gradients, respectively, exerted a predictable mechanism of action. Accumulation of [14C]epinephrine or [14C]5-hydroxytryptamine was over 1 order of magnitude greater in the presence of the transmembrane proton gradient or the transmembrane potential than in the absence of any gradient and, moreover, was related to the magnitude of the proton or potential gradient in a dose-dependent manner. When ghosts were added to a medium containing chloride and isethionate, both a delta pH and delta psi could be generated upon addition of ATP. In this preparation, the maximal rate of amine accumulation was observed. The results indicate that amine accumulation into chromaffin ghosts can occur in the presence of either a transmembrane proton gradient, or a transmembrane potential gradient, and that the maximal rate of accumulation may exist when both components of the protonmotive force are present.

Recovering a hidden polarization by ghost polarimetry.

PubMed

Janassek, Patrick; Blumenstein, Sébastien; Elsäßer, Wolfgang

2018-02-15

By exploiting polarization correlations of light from a broadband fiber-based amplified spontaneous emission source we succeed in reconstructing a hidden polarization in a ghost polarimetry experiment in close analogy to ghost imaging and ghost spectroscopy. Thereby, an original linear polarization state in the object arm of a Mach-Zehnder interferometer configuration which has been camouflaged by a subsequent depolarizer is recovered by correlating it with light from a reference beam. The variation of a linear polarizer placed inside the reference beam results in a Malus law type second-order intensity correlation with high contrast, thus measuring a ghost polarigram.

Ghost analysis visualization techniques for complex systems: examples from the NIF Final Optics Assembly

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

Beer, G K; Hendrix, J L; Rowe, J

1998-06-26

The stray light or "ghost" analysis of the National Ignition Facility's (NIP) Final Optics Assembly (FOA) has proved to be one of the most complex ghost analyses ever attempted. The NIF FOA consists of a bundle of four beam lines that: 1) provides the vacuum seal to the target chamber, 2) converts 1ω to 3ω light, 3) focuses the light on the target, 4) separates a fraction of the 3ω beam for energy diagnostics, 5) separates the three wavelengths to diffract unwanted 1ω & 2ω light away from the target, 6) provides spatial beam smoothing, and 7) provides a debrismore » barrier between the target chamber and the switchyard mirrors. The three wavelengths of light and seven optical elements with three diffractive optic surfaces generate three million ghosts through 4 th order. Approximately 24,000 of these ghosts have peak fluence exceeding 1 J/cm 2. The shear number of ghost paths requires a visualization method that allows overlapping ghosts on optics and mechanical components to be summed and then mapped to the optical and mechanical component surfaces in 3D space. This paper addresses the following aspects of the NIF Final Optics Ghost analysis: 1) materials issues for stray light mitigation, 2) limitations of current software tools (especially in modeling diffractive optics), 3) computer resource limitations affecting automated coherent raytracing, 4) folding the stray light analysis into the opto-mechanical design process, 5) analysis and visualization tools from simple hand calculations to specialized stray light analysis computer codes, and 6) attempts at visualizing these ghosts using a CAD model and another using a high end data visualization software approach.« less

Mechanism for starch granule ghost formation deduced from structural and enzyme digestion properties.

PubMed

Zhang, Bin; Dhital, Sushil; Flanagan, Bernadine M; Gidley, Michael J

2014-01-22

After heating in excess water under little or no shear, starch granules do not dissolve completely but persist as highly swollen fragile forms, commonly termed granule "ghosts". The macromolecular architecture of these ghosts has not been defined, despite their importance in determining characteristic properties of starches. In this study, amylase digestion of isolated granule ghosts from maize and potato starches is used as a probe to study the mechanism of ghost formation, through microstructural, mesoscopic, and molecular scale analyses of structure before and after digestion. Digestion profiles showed that neither integral nor surface proteins/lipids were crucial for control of either ghost digestion or integrity. On the basis of the molecular composition and conformation of enzyme-resistant fractions, it was concluded that the condensed polymeric surface structure of ghost particles is mainly composed of nonordered but entangled amylopectin (and some amylose) molecules, with limited reinforcement through partially ordered enzyme-resistant structures based on amylose (for maize starch; V-type order) or amylopectin (for potato starch; B-type order). The high level of branching and large molecular size of amylopectin is proposed to be the origin for the unusual stability of a solid structure based primarily on temporary entanglements.

Biconcave shape of human red-blood-cell ghosts relies on density differences between the rim and dimple of the ghost's plasma membrane.

PubMed

Hoffman, Joseph F

2016-12-20

The shape of the human red blood cell is known to be a biconcave disk. It is evident from a variety of theoretical work that known physical properties of the membrane, such as its bending energy and elasticity, can explain the red-blood-cell biconcave shape as well as other shapes that red blood cells assume. But these analyses do not provide information on the underlying molecular causes. This paper describes experiments that attempt to identify some of the underlying determinates of cell shape. To this end, red-blood-cell ghosts were made by hypotonic hemolysis and then reconstituted such that they were smooth spheres in hypo-osmotic solutions and smooth biconcave discs in iso-osmotic solutions. The spherical ghosts were centrifuged onto a coated coverslip upon which they adhered. When the attached spheres were changed to biconcave discs by flushing with an iso-osmotic solution, the ghosts were observed to be mainly oriented in a flat alignment on the coverslip. This was interpreted to mean that, during centrifugation, the spherical ghosts were oriented by a dense band in its equatorial plane, parallel to the centrifugal field. This appears to be evidence that the difference in the densities between the rim and the dimple regions of red blood cells and their ghosts may be responsible for their biconcave shape.

Biconcave shape of human red-blood-cell ghosts relies on density differences between the rim and dimple of the ghost's plasma membrane

PubMed Central

Hoffman, Joseph F.

2016-01-01

The shape of the human red blood cell is known to be a biconcave disk. It is evident from a variety of theoretical work that known physical properties of the membrane, such as its bending energy and elasticity, can explain the red-blood-cell biconcave shape as well as other shapes that red blood cells assume. But these analyses do not provide information on the underlying molecular causes. This paper describes experiments that attempt to identify some of the underlying determinates of cell shape. To this end, red-blood-cell ghosts were made by hypotonic hemolysis and then reconstituted such that they were smooth spheres in hypo-osmotic solutions and smooth biconcave discs in iso-osmotic solutions. The spherical ghosts were centrifuged onto a coated coverslip upon which they adhered. When the attached spheres were changed to biconcave discs by flushing with an iso-osmotic solution, the ghosts were observed to be mainly oriented in a flat alignment on the coverslip. This was interpreted to mean that, during centrifugation, the spherical ghosts were oriented by a dense band in its equatorial plane, parallel to the centrifugal field. This appears to be evidence that the difference in the densities between the rim and the dimple regions of red blood cells and their ghosts may be responsible for their biconcave shape. PMID:27930321

Gauge fields and ghosts in Rindler space

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

Zhitnitsky, Ariel R.

2010-11-15

We consider a two-dimensional Maxwell system defined on the Rindler space with metric ds{sup 2}=exp(2a{xi}){center_dot}(d{eta}{sup 2}-d{xi}{sup 2}) with the goal to study the dynamics of the ghosts. We find an extra contribution to the vacuum energy in comparison with Minkowski space-time with metric ds{sup 2}=dt{sup 2}-dx{sup 2}. This extra contribution can be traced to the unphysical degrees of freedom (in Minkowski space). The technical reason for this effect to occur is the property of Bogolubov's coefficients which mix the positive- and negative-frequency modes. The corresponding mixture cannot be avoided because the projections to positive-frequency modes with respect to Minkowski timemore » t and positive-frequency modes with respect to the Rindler observer's proper time {eta} are not equivalent. The exact cancellation of unphysical degrees of freedom which is maintained in Minkowski space cannot hold in the Rindler space. In the Becchi-Rouet-Stora-Tyutin (BRST) approach this effect manifests itself as the presence of BRST charge density in L and R parts. An inertial observer in Minkowski vacuum |0> observes a universe with no net BRST charge only as a result of cancellation between the two. However, the Rindler observers who do not ever have access to the entire space-time would see a net BRST charge. In this respect the effect resembles the Unruh effect. The effect is infrared (IR) in nature, and sensitive to the horizon and/or boundaries. We interpret the extra energy as the formation of the ''ghost condensate'' when the ghost degrees of freedom cannot propagate, but nevertheless do contribute to the vacuum energy. Exact computations in this simple two-dimensional model support the claim made in a previous paper [F. R. Urban and A. R. Zhitnitsky, Nucl. Phys. B835, 135 (2010).] that the ghost contribution might be responsible for the observed dark energy in a four-dimensional Friedmann-Lemaitre-Robertson-Walker universe.« less

A mass-conservative adaptive FAS multigrid solver for cell-centered finite difference methods on block-structured, locally-cartesian grids

NASA Astrophysics Data System (ADS)

Feng, Wenqiang; Guo, Zhenlin; Lowengrub, John S.; Wise, Steven M.

2018-01-01

We present a mass-conservative full approximation storage (FAS) multigrid solver for cell-centered finite difference methods on block-structured, locally cartesian grids. The algorithm is essentially a standard adaptive FAS (AFAS) scheme, but with a simple modification that comes in the form of a mass-conservative correction to the coarse-level force. This correction is facilitated by the creation of a zombie variable, analogous to a ghost variable, but defined on the coarse grid and lying under the fine grid refinement patch. We show that a number of different types of fine-level ghost cell interpolation strategies could be used in our framework, including low-order linear interpolation. In our approach, the smoother, prolongation, and restriction operations need never be aware of the mass conservation conditions at the coarse-fine interface. To maintain global mass conservation, we need only modify the usual FAS algorithm by correcting the coarse-level force function at points adjacent to the coarse-fine interface. We demonstrate through simulations that the solver converges geometrically, at a rate that is h-independent, and we show the generality of the solver, applying it to several nonlinear, time-dependent, and multi-dimensional problems. In several tests, we show that second-order asymptotic (h → 0) convergence is observed for the discretizations, provided that (1) at least linear interpolation of the ghost variables is employed, and (2) the mass conservation corrections are applied to the coarse-level force term.

GhostWriter-2.0: Product Reviews with Case-Based Support

NASA Astrophysics Data System (ADS)

Bridge, Derek; Healy, Paul

A lot of user-generated content on the Web takes the form of records of personal experiences. Case-Based Reasoning offers a way of helping one user to reuse another's experiences from the Web. In this paper, we present GhostWriter-2.0, a Case-Based Reasoning system that supports a user who is writing a product review. GhostWriter-2.0 makes suggestions to the user, in the form of short phrases that are mined from other reviews. The purpose of the suggestions is to prompt the user to write a more comprehensive and helpful review than she might otherwise have done. We explain how GhostWriter-2.0's case base is populated with relevant and helpful reviews from Amazon. We show how it extracts and scores phrases in these reviews to decide which to suggest to the user.We report a trial with real users, in which users made greater use of GhostWriter-2.0's suggested phrases than they did of phrases suggested by a system that used a more random form of selection.

Improved Seam-Line Searching Algorithm for UAV Image Mosaic with Optical Flow.

PubMed

Zhang, Weilong; Guo, Bingxuan; Li, Ming; Liao, Xuan; Li, Wenzhuo

2018-04-16

Ghosting and seams are two major challenges in creating unmanned aerial vehicle (UAV) image mosaic. In response to these problems, this paper proposes an improved method for UAV image seam-line searching. First, an image matching algorithm is used to extract and match the features of adjacent images, so that they can be transformed into the same coordinate system. Then, the gray scale difference, the gradient minimum, and the optical flow value of pixels in adjacent image overlapped area in a neighborhood are calculated, which can be applied to creating an energy function for seam-line searching. Based on that, an improved dynamic programming algorithm is proposed to search the optimal seam-lines to complete the UAV image mosaic. This algorithm adopts a more adaptive energy aggregation and traversal strategy, which can find a more ideal splicing path for adjacent UAV images and avoid the ground objects better. The experimental results show that the proposed method can effectively solve the problems of ghosting and seams in the panoramic UAV images.

Variable horizon in a peridynamic medium

DOE PAGES

Silling, Stewart A.; Littlewood, David J.; Seleson, Pablo

2015-12-10

Here, a notion of material homogeneity is proposed for peridynamic bodies with variable horizon but constant bulk properties. A relation is derived that scales the force state according to the position-dependent horizon while keeping the bulk properties unchanged. Using this scaling relation, if the horizon depends on position, artifacts called ghost forces may arise in a body under a homogeneous deformation. These artifacts depend on the second derivative of the horizon and can be reduced by employing a modified equilibrium equation using a new quantity called the partial stress. Bodies with piecewise constant horizon can be modeled without ghost forcesmore » by using a simpler technique called a splice. As a limiting case of zero horizon, both the partial stress and splice techniques can be used to achieve local-nonlocal coupling. Computational examples, including dynamic fracture in a one-dimensional model with local-nonlocal coupling, illustrate the methods.« less

Ghost hunting—an assessment of ghost particle detection and removal methods for tomographic-PIV

NASA Astrophysics Data System (ADS)

Elsinga, G. E.; Tokgoz, S.

2014-08-01

This paper discusses and compares several methods, which aim to remove spurious peaks, i.e. ghost particles, from the volume intensity reconstruction in tomographic-PIV. The assessment is based on numerical simulations of time-resolved tomographic-PIV experiments in linear shear flows. Within the reconstructed volumes, intensity peaks are detected and tracked over time. These peaks are associated with particles (either ghosts or actual particles) and are characterized by their peak intensity, size and track length. Peak intensity and track length are found to be effective in discriminating between most ghosts and the actual particles, although not all ghosts can be detected using only a single threshold. The size of the reconstructed particles does not reveal an important difference between ghosts and actual particles. The joint distribution of peak intensity and track length however does, under certain conditions, allow a complete separation of ghosts and actual particles. The ghosts can have either a high intensity or a long track length, but not both combined, like all the actual particles. Removing the detected ghosts from the reconstructed volume and performing additional MART iterations can decrease the particle position error at low to moderate seeding densities, but increases the position error, velocity error and tracking errors at higher densities. The observed trends in the joint distribution of peak intensity and track length are confirmed by results from a real experiment in laminar Taylor-Couette flow. This diagnostic plot allows an estimate of the number of ghosts that are indistinguishable from the actual particles.

Image quality enhancement in low-light-level ghost imaging using modified compressive sensing method

NASA Astrophysics Data System (ADS)

Shi, Xiaohui; Huang, Xianwei; Nan, Suqin; Li, Hengxing; Bai, Yanfeng; Fu, Xiquan

2018-04-01

Detector noise has a significantly negative impact on ghost imaging at low light levels, especially for existing recovery algorithm. Based on the characteristics of the additive detector noise, a method named modified compressive sensing ghost imaging is proposed to reduce the background imposed by the randomly distributed detector noise at signal path. Experimental results show that, with an appropriate choice of threshold value, modified compressive sensing ghost imaging algorithm can dramatically enhance the contrast-to-noise ratio of the object reconstruction significantly compared with traditional ghost imaging and compressive sensing ghost imaging methods. The relationship between the contrast-to-noise ratio of the reconstruction image and the intensity ratio (namely, the average signal intensity to average noise intensity ratio) for the three reconstruction algorithms are also discussed. This noise suppression imaging technique will have great applications in remote-sensing and security areas.

SPH for impact force and ricochet behavior of water-entry bodies

NASA Astrophysics Data System (ADS)

Omidvar, Pourya; Farghadani, Omid; Nikeghbali, Pooyan

The numerical modeling of fluid interaction with a bouncing body has many applications in scientific and engineering application. In this paper, the problem of water impact of a body on free-surface is investigated, where the fixed ghost boundary condition is added to the open source code SPHysics2D1 to rectify the oscillations in pressure distributions with the repulsive boundary condition. First, after introducing the methodology of SPH and the option of boundary conditions, the still water problem is simulated using two types of boundary conditions. It is shown that the fixed ghost boundary condition gives a better result for a hydrostatics pressure. Then, the dam-break problem, which is a bench mark test case in SPH, is simulated and compared with available data. In order to show the behavior of the hydrostatics forces on bodies, a fix/floating cylinder is placed on free surface looking carefully at the force and heaving profile. Finally, the impact of a body on free-surface is successfully simulated for different impact angles and velocities.

Ghost Remains After Black Hole Eruption

NASA Astrophysics Data System (ADS)

2009-05-01

NASA's Chandra X-ray Observatory has found a cosmic "ghost" lurking around a distant supermassive black hole. This is the first detection of such a high-energy apparition, and scientists think it is evidence of a huge eruption produced by the black hole. This discovery presents astronomers with a valuable opportunity to observe phenomena that occurred when the Universe was very young. The X-ray ghost, so-called because a diffuse X-ray source has remained after other radiation from the outburst has died away, is in the Chandra Deep Field-North, one of the deepest X-ray images ever taken. The source, a.k.a. HDF 130, is over 10 billion light years away and existed at a time 3 billion years after the Big Bang, when galaxies and black holes were forming at a high rate. "We'd seen this fuzzy object a few years ago, but didn't realize until now that we were seeing a ghost", said Andy Fabian of the Cambridge University in the United Kingdom. "It's not out there to haunt us, rather it's telling us something - in this case what was happening in this galaxy billions of year ago." Fabian and colleagues think the X-ray glow from HDF 130 is evidence for a powerful outburst from its central black hole in the form of jets of energetic particles traveling at almost the speed of light. When the eruption was ongoing, it produced prodigious amounts of radio and X-radiation, but after several million years, the radio signal faded from view as the electrons radiated away their energy. HDF 130 Chandra X-ray Image of HDF 130 However, less energetic electrons can still produce X-rays by interacting with the pervasive sea of photons remaining from the Big Bang - the cosmic background radiation. Collisions between these electrons and the background photons can impart enough energy to the photons to boost them into the X-ray energy band. This process produces an extended X-ray source that lasts for another 30 million years or so. "This ghost tells us about the black hole's eruption long after it has died," said co-author Scott Chapman, also of Cambridge University. "This means we don't have to catch the black holes in the act to witness the big impact they have." This is the first X-ray ghost ever seen after the demise of radio-bright jets. Astronomers have observed extensive X-ray emission with a similar origin, but only from galaxies with radio emission on large scales, signifying continued eruptions. In HDF 130, only a point source is detected in radio images, coinciding with the massive elliptical galaxy seen in its optical image. This radio source indicates the presence of a growing supermassive black hole. People Who Read This Also Read... Milky Way's Super-efficient Particle Accelerators Caught in The Act NASA Joins "Around the World in 80 Telescopes" Celebrate the International Year of Astronomy Galaxies Coming of Age in Cosmic Blobs "This result hints that the X-ray sky should be littered with such ghosts," said co-author Caitlin Casey, also of Cambridge, "especially if black hole eruptions are as common as we think they are in the early Universe." The power contained in the black hole eruption was likely to be considerable, equivalent to about a billion supernovas. The energy is dumped into the surroundings and transports and heats the gas. "Even after the ghost disappears, most of the energy from the black hole's eruption remains", said Fabian. "Because they're so powerful, these eruptions can have profound effects lasting for billions of years." The details of Chandra's data of HDF 130 helped secure its true nature. For example, in X-rays, HDF 130 has a cigar-like shape that extends for some 2.2 million light years. The linear shape of the X-ray source is consistent with the shape of radio jets and not with that of a galaxy cluster, which is expected to be circular. The energy distribution of the X-rays is also consistent with the interpretation of an X-ray ghost. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Tribology of swollen starch granule suspensions from maize and potato.

PubMed

Zhang, Bin; Selway, Nichola; Shelat, Kinnari J; Dhital, Sushil; Stokes, Jason R; Gidley, Michael J

2017-01-02

The tribological properties of suspensions of cooked swollen starch granules are characterised for systems based on maize starch and potato starch. These systems are known as granule 'ghosts' due to the release (and removal) of polymer from their structure during cooking. Maize starch ghosts are less swollen than potato starch ghosts, resulting in a higher packing concentration and greater mechanical stability. In a soft-tribological contact, maize ghost suspensions reduce friction compared to the solvent (water), generate bell-shaped tribological profiles characteristic of particle entrainment and show a marked concentration dependence, whereas potato ghost suspensions exhibit lubrication behaviour similar to water. Microscopy analysis of the samples following tribological testing suggests that this is due to the rapid break-up of potato ghosts under the shear and rolling conditions within the tribological contact. A reduction in the small deformation moduli (associated with a weak gel structure) is also observed when the potato ghost suspensions are subjected to steady shear using parallel plate rheometry; both microscopy and particle size analysis show that this is accompanied by the partial shear-induced breakage of ghost particles. This interplay between particle microstructure and the resultant rheological and lubrication dynamics of starch ghost suspensions contributes to an enhanced mechanistic understanding of textural and other functional properties of cooked starches in food and other applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Unitarity check in gravitational Higgs mechanism

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

Berezhiani, Lasha; Mirbabayi, Mehrdad

2011-03-15

The effective field theory of massive gravity has long been formulated in a generally covariant way [N. Arkani-Hamed, H. Georgi, and M. D. Schwartz, Ann. Phys. (N.Y.) 305, 96 (2003).]. Using this formalism, it has been found recently that there exists a class of massive nonlinear theories that are free of the Boulware-Deser ghosts, at least in the decoupling limit [C. de Rham and G. Gabadadze, Phys. Rev. D 82, 044020 (2010).]. In this work we study other recently proposed models that go under the name of 'gravitational Higgs theories' [A. H. Chamseddine and V. Mukhanov, J. High Energy Phys.more » 08 (2010) 011.]. We show that these models, although seemingly different from the effective field theories of massive gravity, are in fact equivalent to them. Furthermore, based on the results obtained in the effective field theory approach, we conclude that the gravitational Higgs theories need the same adjustment of the Lagrangian to avoid the ghosts. We also show the equivalence between the noncovariant mode decomposition used in the Higgs theories, and the covariant Stueckelberg parametrization adopted in the effective field theories, thus proving that the presence or absence of the ghost is independent of the parametrization used in either theory.« less

Ghost detection and removal based on super-pixel grouping in exposure fusion

NASA Astrophysics Data System (ADS)

Jiang, Shenyu; Xu, Zhihai; Li, Qi; Chen, Yueting; Feng, Huajun

2014-09-01

A novel multi-exposure images fusion method for dynamic scenes is proposed. The commonly used techniques for high dynamic range (HDR) imaging are based on the combination of multiple differently exposed images of the same scene. The drawback of these methods is that ghosting artifacts will be introduced into the final HDR image if the scene is not static. In this paper, a super-pixel grouping based method is proposed to detect the ghost in the image sequences. We introduce the zero mean normalized cross correlation (ZNCC) as a measure of similarity between a given exposure image and the reference. The calculation of ZNCC is implemented in super-pixel level, and the super-pixels which have low correlation with the reference are excluded by adjusting the weight maps for fusion. Without any prior information on camera response function or exposure settings, the proposed method generates low dynamic range (LDR) images which can be shown on conventional display devices directly with details preserving and ghost effects reduced. Experimental results show that the proposed method generates high quality images which have less ghost artifacts and provide a better visual quality than previous approaches.

Comparative study of receiver-side ghost wavefield attenuation on different marine acquisition configurations

NASA Astrophysics Data System (ADS)

Zhang, Hao; Liu, Qiancheng; Li, Hongyuan; Zhang, Yi

2018-04-01

In marine seismic exploration, the ghost energies (down-going waves), which arise from the reflection at the surface, are often treated as unwanted signals for data processing. The ghost wave fields interfere with the desired primary signals, leads to frequency notches and attenuation of low frequencies, which in turn downgrade the resolution of the recorded seismic data. There are two main categories of methods to solve the ghost or the so-called notch problem: the non-conventional acquisition configuration-based technique and a deghosting algorithm-based solution. The variable-depth streamer (VDS) acquisition solution is one of the most representative methods in the first category, which has become a popular solution for marine seismic acquisition to obtain broad data bandwidth. However, this approach is not as economic as the conventional constant depth streamer (CDS) acquisition, due to the precise control of the towing streamer. In addition, there are large quantities of conventionally-towed legacy data stored in the data library. Applying receiver deghosting to the CDS data thus becomes a more economical method. In theory, both types of data after deghosting should have the same bandwidth and S/N ratio, but in reality they are different. In this paper, we conduct a comparative study and evaluation to apply receiver deghosting to a set of real 2D marine data including both types of acquisition (CDS and VDS) corresponding to the same geology. The deghosting algorithm we employed is a self-sustained, inversion-based approach operated in the τ-p domain. This evaluation can help us to understand two questions: whether the VDS acquisition has more broadband characteristics compared to conventional CDS acquisition after deghosting, and whether we can achieve the identical or similar data quality (e.g., S/N ratio) through the proper deghosting algorithm for both types of data. The comparative results are illustrated and discussed.

Ghost Spectroscopy with Classical Thermal Light Emitted by a Superluminescent Diode

NASA Astrophysics Data System (ADS)

Janassek, Patrick; Blumenstein, Sébastien; Elsäßer, Wolfgang

2018-02-01

We propose and realize the first classical ghost-imaging (GI) experiment in the frequency or wavelength domain, thus performing ghost spectroscopy using thermal light exhibiting photon bunching. The required wavelength correlations are provided by light emitted by spectrally broadband near-infrared amplified spontaneous emission of a semiconductor-based superluminescent diode. They are characterized by wavelength-resolved intensity cross-correlation measurements utilizing two-photon-absorption interferometry. Finally, a real-world spectroscopic application of this ghost spectroscopy with a classical light scheme is demonstrated in which an absorption band of trichloromethane (chloroform) at 1214 nm is reconstructed with a spectral resolution of 10 nm as a proof-of-principle experiment. This ghost-spectroscopy work fills the gap of a hitherto missing analogy between the spatial and the spectral domain in classical GI modalities, with the expectation of contributing towards a broader dissemination of correlated photon ghost modalities, hence paving the way towards more applications which exploit the favorable advantages.

High-quality compressive ghost imaging

NASA Astrophysics Data System (ADS)

Huang, Heyan; Zhou, Cheng; Tian, Tian; Liu, Dongqi; Song, Lijun

2018-04-01

We propose a high-quality compressive ghost imaging method based on projected Landweber regularization and guided filter, which effectively reduce the undersampling noise and improve the resolution. In our scheme, the original object is reconstructed by decomposing of regularization and denoising steps instead of solving a minimization problem in compressive reconstruction process. The simulation and experimental results show that our method can obtain high ghost imaging quality in terms of PSNR and visual observation.

A Parallel Ghosting Algorithm for The Flexible Distributed Mesh Database

DOE PAGES

Mubarak, Misbah; Seol, Seegyoung; Lu, Qiukai; ...

2013-01-01

Critical to the scalability of parallel adaptive simulations are parallel control functions including load balancing, reduced inter-process communication and optimal data decomposition. In distributed meshes, many mesh-based applications frequently access neighborhood information for computational purposes which must be transmitted efficiently to avoid parallel performance degradation when the neighbors are on different processors. This article presents a parallel algorithm of creating and deleting data copies, referred to as ghost copies, which localize neighborhood data for computation purposes while minimizing inter-process communication. The key characteristics of the algorithm are: (1) It can create ghost copies of any permissible topological order in amore » 1D, 2D or 3D mesh based on selected adjacencies. (2) It exploits neighborhood communication patterns during the ghost creation process thus eliminating all-to-all communication. (3) For applications that need neighbors of neighbors, the algorithm can create n number of ghost layers up to a point where the whole partitioned mesh can be ghosted. Strong and weak scaling results are presented for the IBM BG/P and Cray XE6 architectures up to a core count of 32,768 processors. The algorithm also leads to scalable results when used in a parallel super-convergent patch recovery error estimator, an application that frequently accesses neighborhood data to carry out computation.« less

Like night and day: Reversals of thermal gradients across ghost crab burrows and their implications for thermal ecology

NASA Astrophysics Data System (ADS)

Watson, Gregory S.; Gregory, Emily A.; Johnstone, Charmaine; Berlino, Manuel; Green, David W.; Peterson, Nicola R.; Schoeman, David S.; Watson, Jolanta A.

2018-04-01

Ghost crabs, Ocypode cordimanus, inhabit relatively hostile environments subject to thermal fluctuations, including both diurnal and seasonal cycles. For many ectotherms, including ghost crabs, a major challenge is to remain cool during hot daytime temperatures. This can be achieved by adopting a fossorial lifestyle, taking advantage of thermal refuge afforded by burrows of sufficient depth. Another consideration, often overlooked, is the potential advantage associated with ready access to a thermal energy source (a "charging station") when surface temperatures are cooler. Being able to rapidly elevate body temperature during cool periods would enhance the crab's ability to maintain rate processes and carry out essential activities. We have measured ghost crab burrow temperature profiles at two times of the day with contrasting sun exposure (06:00 and 14:00), demonstrating how effective burrow depth (up to a maximum of 40 cm) provides thermal regulation below the surface of the sand (e.g., at dawn (06:00) and early afternoon (14:00) at a depth of 5 cm, temperatures (±SD) of 16.32 ± 0.96 °C and 25.04 ± 1.47 °C were recorded, respectively. Corresponding temperatures at a depth of 30 cm were 19.17 ± 0.59 °C and 19.78 ± 1.60 °C, respectively). This demonstrates that while temperature conditions at the surface vary dramatically from night to day, ghost crab burrows can maintain relatively constant temperatures at the burrow base throughout the diurnal cycle, at least during winter. As a consequence, the burrow heat signatures undergo a corresponding thermal gradient reversal between night and day, as revealed by infra-red photography. Complementing these field observations, we also determined heating and cooling times/constants for O. cordimanus in the laboratory (τ = 17.54 and 16.59 JK-1, respectively), and analysed chemical composition of their carapace (external (with β Chitin evident) and internal (predominance of α Chitin)), which is the primary thermal interface with the environment. We find that ghost crabs both gain and lose heat relatively rapidly, which likely affects the range and duration of surface activities under different thermal conditions, and renders the thermal characteristics of their burrows vital for their persistence on beaches. Finally, we speculate that the distinctly contrasting thermal signatures of ghost crab burrows in comparison to the surrounding sand could in principle be used by crabs as spatial markers for navigation and to identify holes on return from nightly excursions, being identified either by direct thermal sensing or odours rising from the burrow base as a consequence of the thermal flux.

Ghost imaging with paired x-ray photons

NASA Astrophysics Data System (ADS)

Schori, A.; Borodin, D.; Tamasaku, K.; Shwartz, S.

2018-06-01

We report the experimental observation of ghost imaging with paired x-ray photons, which are generated by parametric downconversion. We use the one-to-one relation between the photon energies and the emission angles and the anticorrelation between the k -vectors of the signal and the idler photons to reconstruct the images of slits with nominally zero background levels. Further extension of our procedure can be used for the observation of various quantum phenomena at x-ray wavelengths.

Improved Seam-Line Searching Algorithm for UAV Image Mosaic with Optical Flow

PubMed Central

Zhang, Weilong; Guo, Bingxuan; Liao, Xuan; Li, Wenzhuo

2018-01-01

Ghosting and seams are two major challenges in creating unmanned aerial vehicle (UAV) image mosaic. In response to these problems, this paper proposes an improved method for UAV image seam-line searching. First, an image matching algorithm is used to extract and match the features of adjacent images, so that they can be transformed into the same coordinate system. Then, the gray scale difference, the gradient minimum, and the optical flow value of pixels in adjacent image overlapped area in a neighborhood are calculated, which can be applied to creating an energy function for seam-line searching. Based on that, an improved dynamic programming algorithm is proposed to search the optimal seam-lines to complete the UAV image mosaic. This algorithm adopts a more adaptive energy aggregation and traversal strategy, which can find a more ideal splicing path for adjacent UAV images and avoid the ground objects better. The experimental results show that the proposed method can effectively solve the problems of ghosting and seams in the panoramic UAV images. PMID:29659526

Globally Deghosting for Marine Streamer with Alternating Minimization Approach in Frequency-slowness Domain

NASA Astrophysics Data System (ADS)

Wang, C.; Zhu, Z.; Gu, H.; Liu, C.; Liu, Z.; Jiao, Z.

2017-12-01

The ghost effects of the sea surface can generate notch in marine towed-streamer data, which results in narrow bandwidth of seismic data. Currently, deghosting is widely utilized to increase the bandwidth of the seismic data or the images. However, most of the conventional deghosting algorithms havenot considered the error of streamer depth causing a biased ghost-delay time (τ) with respect to primary reflection and amplitude difference coefficient (r) between ghost and primary reflection varies with offset due to rugged seabed and target depth variation. We proposed a ghost filtering operator considering the protentional biases within the ghost-delay time (τ) and the amplitude difference coefficient (r). The up-going wavefield (u), ghost-delay time (τ) and amplitude difference coefficient (r) can be obtained by utilizing alternating minimization approach for minimizing the difference between actual wavefield and theoretical wavefield in frequency-slowness domain. The main idea is to alternatively updating u, τ and r in each iteration: we update u by least-squares when we keep τ and r constant; and we then keep u constant and optimize over τ and r with a closed-form solution which is closely related to matched filtering. The convergence of the proposed algorithm is guaranteed since we have closed-form solutions for each stage. The experiments on synthetic record confirmed the reliability of the proposed algorithm. We also demonstrate our proposed method in marine VDS shot acquisition. After migration stack processing, our ghosting method significantly increases the bandwidth of the average amplitude, amplitude energy of the medium and high frequency spectrum, improving resolution of medium and deep reflection and providing higher signal-to-noise ratio with clear break point. This research is funded by China Important National Science & Technology Specific Projects (2016ZX05026001-001).

The x-ray time of flight method for investigation of ghosting in amorphous selenium-based flat panel medical x-ray imagers.

PubMed

Rau, A W; Bakueva, L; Rowlands, J A

2005-10-01

Amorphous selenium (a-Se) based real-time flat-panel imagers (FPIs) are finding their way into the digital radiology department because they offer the practical advantages of digital x-ray imaging combined with an image quality that equals or outperforms that of conventional systems. The temporal imaging characteristics of FPIs can be affected by ghosting (i.e., radiation-induced changes of sensitivity) when the dose to the detector is high (e.g., portal imaging and mammography) or the images are acquired at a high frame rate (e.g., fluoroscopy). In this paper, the x-ray time-of-flight (TOF) method is introduced as a tool for the investigation of ghosting in a-Se photoconductor layers. The method consists of irradiating layers of a-Se with short x-ray pulses. From the current generated in the a-Se layer, ghosting is quantified and the ghosting parameters (charge carrier generation rate and carrier lifetimes and mobilities) are assessed. The x-ray TOF method is novel in that (1) x-ray sensitivity (S) and ghosting parameters can be measured simultaneously, (2) the transport of both holes and electrons can be isolated, and (3) the method is applicable to the practical a-Se layer structure with blocking contacts used in FPIs. The x-ray TOF method was applied to an analysis of ghosting in a-Se photoconductor layers under portal imaging conditions, i.e., 1 mm thick a-Se layers, biased at 5 V/ microm, were irradiated using a 6 MV LINAC x-ray beam to a total dose (ghosting dose) of 30 Gy. The initial sensitivity (S0) of the a-Se layers was 63 +/- 2 nC cm(-2) cGy(-1). It was found that S decreases to 30% of S0 after a ghosting dose of 5 Gy and to 21% after 30 Gy at which point no further change in S occurs. At an x-ray intensity of 22 Gy/s (instantaneous dose rate during a LINAC x-ray pulse), the charge carrier generation rate was 1.25 +/- 0.1 x 10(22) ehp m(-3) s(-1) and, to a first approximation, independent of the ghosting dose. However, both hole and electron transport showed a strong dependence on the ghosting dose: hole transport decreased by 61%, electron transport by up to approximately 80%. Therefore, degradation of both hole and electron transport due to the recombination of mobile charge carriers with trapped carriers (of opposite polarity) were identified as the main cause of ghosting in this study.

Reflective ghost imaging through turbulence

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

Hardy, Nicholas D.; Shapiro, Jeffrey H.

2011-12-15

Recent work has indicated that ghost imaging may have applications in standoff sensing. However, most theoretical work has addressed transmission-based ghost imaging. To be a viable remote-sensing system, the ghost imager needs to image rough-surfaced targets in reflection through long, turbulent optical paths. We develop, within a Gaussian-state framework, expressions for the spatial resolution, image contrast, and signal-to-noise ratio of such a system. We consider rough-surfaced targets that create fully developed speckle in their returns and Kolmogorov-spectrum turbulence that is uniformly distributed along all propagation paths. We address both classical and nonclassical optical sources, as well as a computational ghostmore » imager.« less

Ghost instabilities of cosmological models with vector fields nonminimally coupled to the curvature

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

Himmetoglu, Burak; Peloso, Marco; Contaldi, Carlo R.

2009-12-15

We prove that many cosmological models characterized by vectors nonminimally coupled to the curvature (such as the Turner-Widrow mechanism for the production of magnetic fields during inflation, and models of vector inflation or vector curvaton) contain ghosts. The ghosts are associated with the longitudinal vector polarization present in these models and are found from studying the sign of the eigenvalues of the kinetic matrix for the physical perturbations. Ghosts introduce two main problems: (1) they make the theories ill defined at the quantum level in the high energy/subhorizon regime (and create serious problems for finding a well-behaved UV completion), andmore » (2) they create an instability already at the linearized level. This happens because the eigenvalue corresponding to the ghost crosses zero during the cosmological evolution. At this point the linearized equations for the perturbations become singular (we show that this happens for all the models mentioned above). We explicitly solve the equations in the simplest cases of a vector without a vacuum expectation value in a Friedmann-Robertson-Walker geometry, and of a vector with a vacuum expectation value plus a cosmological constant, and we show that indeed the solutions of the linearized equations diverge when these equations become singular.« less

Scene-based nonuniformity correction with reduced ghosting using a gated LMS algorithm.

PubMed

Hardie, Russell C; Baxley, Frank; Brys, Brandon; Hytla, Patrick

2009-08-17

In this paper, we present a scene-based nouniformity correction (NUC) method using a modified adaptive least mean square (LMS) algorithm with a novel gating operation on the updates. The gating is designed to significantly reduce ghosting artifacts produced by many scene-based NUC algorithms by halting updates when temporal variation is lacking. We define the algorithm and present a number of experimental results to demonstrate the efficacy of the proposed method in comparison to several previously published methods including other LMS and constant statistics based methods. The experimental results include simulated imagery and a real infrared image sequence. We show that the proposed method significantly reduces ghosting artifacts, but has a slightly longer convergence time. (c) 2009 Optical Society of America

Numerical Treatment of Stokes Solvent Flow and Solute-Solvent Interfacial Dynamics for Nonpolar Molecules.

PubMed

Sun, Hui; Zhou, Shenggao; Moore, David K; Cheng, Li-Tien; Li, Bo

2016-05-01

We design and implement numerical methods for the incompressible Stokes solvent flow and solute-solvent interface motion for nonpolar molecules in aqueous solvent. The balance of viscous force, surface tension, and van der Waals type dispersive force leads to a traction boundary condition on the solute-solvent interface. To allow the change of solute volume, we design special numerical boundary conditions on the boundary of a computational domain through a consistency condition. We use a finite difference ghost fluid scheme to discretize the Stokes equation with such boundary conditions. The method is tested to have a second-order accuracy. We combine this ghost fluid method with the level-set method to simulate the motion of the solute-solvent interface that is governed by the solvent fluid velocity. Numerical examples show that our method can predict accurately the blow up time for a test example of curvature flow and reproduce the polymodal (e.g., dry and wet) states of hydration of some simple model molecular systems.

Numerical Treatment of Stokes Solvent Flow and Solute-Solvent Interfacial Dynamics for Nonpolar Molecules

PubMed Central

Sun, Hui; Zhou, Shenggao; Moore, David K.; Cheng, Li-Tien; Li, Bo

2015-01-01

We design and implement numerical methods for the incompressible Stokes solvent flow and solute-solvent interface motion for nonpolar molecules in aqueous solvent. The balance of viscous force, surface tension, and van der Waals type dispersive force leads to a traction boundary condition on the solute-solvent interface. To allow the change of solute volume, we design special numerical boundary conditions on the boundary of a computational domain through a consistency condition. We use a finite difference ghost fluid scheme to discretize the Stokes equation with such boundary conditions. The method is tested to have a second-order accuracy. We combine this ghost fluid method with the level-set method to simulate the motion of the solute-solvent interface that is governed by the solvent fluid velocity. Numerical examples show that our method can predict accurately the blow up time for a test example of curvature flow and reproduce the polymodal (e.g., dry and wet) states of hydration of some simple model molecular systems. PMID:27365866

Rewritable ghost floating gates by tunnelling triboelectrification for two-dimensional electronics

PubMed Central

Kim, Seongsu; Kim, Tae Yun; Lee, Kang Hyuck; Kim, Tae-Ho; Cimini, Francesco Arturo; Kim, Sung Kyun; Hinchet, Ronan; Kim, Sang-Woo; Falconi, Christian

2017-01-01

Gates can electrostatically control charges inside two-dimensional materials. However, integrating independent gates typically requires depositing and patterning suitable insulators and conductors. Moreover, after manufacturing, gates are unchangeable. Here we introduce tunnelling triboelectrification for localizing electric charges in very close proximity of two-dimensional materials. As representative materials, we use chemical vapour deposition graphene deposited on a SiO2/Si substrate. The triboelectric charges, generated by friction with a Pt-coated atomic force microscope tip and injected through defects, are trapped at the air–SiO2 interface underneath graphene and act as ghost floating gates. Tunnelling triboelectrification uniquely permits to create, modify and destroy p and n regions at will with the spatial resolution of atomic force microscopes. As a proof of concept, we draw rewritable p/n+ and p/p+ junctions with resolutions as small as 200 nm. Our results open the way to time-variant two-dimensional electronics where conductors, p and n regions can be defined on demand. PMID:28649986

Rewritable ghost floating gates by tunnelling triboelectrification for two-dimensional electronics

NASA Astrophysics Data System (ADS)

Kim, Seongsu; Kim, Tae Yun; Lee, Kang Hyuck; Kim, Tae-Ho; Cimini, Francesco Arturo; Kim, Sung Kyun; Hinchet, Ronan; Kim, Sang-Woo; Falconi, Christian

2017-06-01

Gates can electrostatically control charges inside two-dimensional materials. However, integrating independent gates typically requires depositing and patterning suitable insulators and conductors. Moreover, after manufacturing, gates are unchangeable. Here we introduce tunnelling triboelectrification for localizing electric charges in very close proximity of two-dimensional materials. As representative materials, we use chemical vapour deposition graphene deposited on a SiO2/Si substrate. The triboelectric charges, generated by friction with a Pt-coated atomic force microscope tip and injected through defects, are trapped at the air-SiO2 interface underneath graphene and act as ghost floating gates. Tunnelling triboelectrification uniquely permits to create, modify and destroy p and n regions at will with the spatial resolution of atomic force microscopes. As a proof of concept, we draw rewritable p/n+ and p/p+ junctions with resolutions as small as 200 nm. Our results open the way to time-variant two-dimensional electronics where conductors, p and n regions can be defined on demand.

UV-extending ghost inflation

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

Ivanov, Mikhail M.; Sibiryakov, Sergey, E-mail: mm.ivanov@physics.msu.ru, E-mail: sergey.sibiryakov@cern.ch

2014-05-01

We present a setup that provides a partial UV-completion of the ghost inflation model up to a scale which can be almost as high as the Planck mass. This is achieved by coupling the inflaton to the Lorentz-violating sector described by the Einstein-aether theory or its khronometric version. Compared to previous works on ghost inflation our setup allows to go beyond the study of small perturbations and include the background dynamics in a unified framework. In the specific regime when the expansion of the Universe is dominated by the kinetic energy of the inflaton we find that the model predictsmore » rather high tensor-to-scalar ratio r ∼ 0.02÷0.2 and non-Gaussianity of equilateral type with f{sub NL} in the range from -50 to -5.« less

Latest results from the GreenHouse gas Observations of the Stratosphere and Troposphere (GHOST) airborne shortwave infrared spectrometer

NASA Astrophysics Data System (ADS)

Humpage, Neil; Boesch, Hartmut; Palmer, Paul; Vick, Andy

2017-04-01

GHOST is a novel, compact shortwave infrared grating spectrometer, designed for remote sensing of tropospheric columns of greenhouse gases (GHGs) from an airborne platform. GHOST observes solar radiation at medium to high spectral resolution which has been reflected by the surface, using similar methods to those used by polar orbiting satellites such as the JAXA GOSAT mission, the NASA OCO-2 mission and the forthcoming Copernicus Sentinel 5-Precursor. By using an original design comprising optical fibre inputs along with a single diffraction grating and detector array, GHOST is able to observe CO2 absorption bands centred around 1.61 μm and 2.06 μm (the same wavelength regions used by OCO-2 and GOSAT) whilst simultaneously measuring CH4 absorption at 1.65 μm (also observed by GOSAT), and both CH4 and CO at 2.30 μm (to be observed by Sentinel 5-P once launched later in 2017). The overlapping spectral ranges and comparable spectral resolutions mean that GHOST has unique potential for providing validation opportunities for these platforms, particularly over the ocean where ground-based validation measurements are not available. Here we present the latest results from the spectral analysis, using an optimal estimation based retrieval method, of CO2 and CH4 from GHOST flight spectra for the 1.6 μm band which utilise recently updated laboratory calibration measurements. GHOST took part in two science flights on board the NASA Global Hawk unmanned aerial vehicle based at the Armstrong Flight Research Centre in Edwards, California, in March 2015. These flights involved long approximately north-south transects over the eastern Pacific Ocean. In addition to observing spatial trends in GHG column concentrations over a regional scale, the second of these flights (on 10th March) allows inter-comparisons of GHOST retrievals with observations from OCO-2 and GOSAT, which both passed directly over the Global Hawk during clear sky conditions. We will show results from these flights together with an analysis of measurements from the laboratory to assess the instrument performance, and demonstrate the suitability of GHOST for model evaluation and for the validation of column-averaged GHG concentrations measured from space.

Head-on collision of ultrarelativistic particles in ghost-free theories of gravity

NASA Astrophysics Data System (ADS)

Frolov, Valeri P.; Zelnikov, Andrei

2016-03-01

We study linearized equations of a ghost-free gravity in four- and higher-dimensional spacetimes. We consider versions of such a theory where the nonlocal modification of the □ operator has the form □exp [(-□/μ2)N] , where N =1 or N =2 n . We first obtain the Newtonian gravitational potential for a point mass for such models and demonstrate that it is finite and regular in any number of spatial dimensions d ≥3 . The second result of the paper is calculation of the gravitational field of an ultrarelativistic particle in such theories. And finally, we study a head-on collision of two ultrarelativistic particles. We formulated conditions of the apparent horizon formation and showed that there exists a mass gap for mini-black-hole production in the ghost-free theory of gravity. In the case when the center-of-mass energy is sufficient for the formation of the apparent horizon, the latter has two branches, the outer and the inner ones. When the energy increases the outer horizon tends to the Schwarzschild-Tangherlini limit, while the inner horizon becomes closer to r =0 .

Towards construction of ghost-free higher derivative gravity from bigravity

NASA Astrophysics Data System (ADS)

Akagi, Satoshi

2018-06-01

In this paper, the ghost-freeness of the higher derivative theory proposed by Hassan et al. in [Universe 1, 92 (2015), 10.3390/universe1020092] is investigated. Hassan et al. believed the ghost-freeness of the higher derivative theory based on the analysis in the linear approximation. However, in order to obtain the complete correspondence, we have to analyze the model without any approximations. In this paper, we analyze the two-scalar model proposed in [Universe 1, 92 (2015), 10.3390/universe1020092] with arbitrary nonderivative interaction terms. In any order with respect to perturbative parameters, we prove that we can eliminate the ghost for the model with any nonderivative interaction terms.

On the generalized wormhole in the Eddington-inspired Born-Infeld gravity

NASA Astrophysics Data System (ADS)

Tamang, Amarjit; Potapov, Alexander A.; Lukmanova, Regina; Izmailov, Ramil; Nandi, Kamal K.

2015-12-01

In this paper, we wish to investigate certain observable effects in the recently obtained wormhole solution of the Eddington-inspired Born-Infeld (EiBI) theory, which generalizes the zero-mass Ellis-Bronnikov wormhole of general relativity. The solutions of EiBI theory contain an extra parameter κ having the inverse dimension of the cosmological constant Λ, and which is expected to modify various general relativistic observables such as the masses of wormhole mouths, tidal forces and light deflection. A remarkable result is that a non-zero κ could prevent the tidal forces in the geodesic orthonormal frame from becoming arbitrarily large near a small throat radius ({r}0˜ 0) contrary to what happens near a small Schwarzschild horizon radius (M˜ 0). The role of κ in the flare-out and energy conditions is also analyzed, which reveals that the energy conditions are violated. We show that the exotic matter in the EiBI wormhole cannot be interpreted as a phantom (ω =\\frac{{p}{{r}}}{ρ }\\lt -1) or ghost field ϕ of general relativity due to the fact that both ρ and p r are negative for all κ.

Nonlinear Errors Resulting from Ghost Reflection and Its Coupling with Optical Mixing in Heterodyne Laser Interferometers

PubMed Central

Fu, Haijin; Wang, Yue; Tan, Jiubin; Fan, Zhigang

2018-01-01

Even after the Heydemann correction, residual nonlinear errors, ranging from hundreds of picometers to several nanometers, are still found in heterodyne laser interferometers. This is a crucial factor impeding the realization of picometer level metrology, but its source and mechanism have barely been investigated. To study this problem, a novel nonlinear model based on optical mixing and coupling with ghost reflection is proposed and then verified by experiments. After intense investigation of this new model’s influence, results indicate that new additional high-order and negative-order nonlinear harmonics, arising from ghost reflection and its coupling with optical mixing, have only a negligible contribution to the overall nonlinear error. In real applications, any effect on the Lissajous trajectory might be invisible due to the small ghost reflectance. However, even a tiny ghost reflection can significantly worsen the effectiveness of the Heydemann correction, or even make this correction completely ineffective, i.e., compensation makes the error larger rather than smaller. Moreover, the residual nonlinear error after correction is dominated only by ghost reflectance. PMID:29498685

Water transport by the bacterial channel alpha-hemolysin

NASA Technical Reports Server (NTRS)

Paula, S.; Akeson, M.; Deamer, D.

1999-01-01

This study is an investigation of the ability of the bacterial channel alpha-hemolysin to facilitate water permeation across biological membranes. alpha-Hemolysin channels were incorporated into rabbit erythrocyte ghosts at varying concentrations, and water permeation was induced by mixing the ghosts with hypertonic sucrose solutions. The resulting volume decrease of the ghosts was followed by time-resolved optical absorption at pH 5, 6, and 7. The average single-channel permeability coefficient of alpha-hemolysin for water ranged between 1.3x10-12 cm/s and 1.5x10-12 cm/s, depending on pH. The slightly increased single-channel permeability coefficient at lower pH-values was attributed to an increase in the effective pore size. The activation energy of water transport through the channel was low (Ea=5.4 kcal/mol), suggesting that the properties of water inside the alpha-hemolysin channel resemble those of bulk water. This conclusion was supported by calculations based on macroscopic hydrodynamic laws of laminar water flow. Using the known three-dimensional structure of the channel, the calculations accurately predicted the rate of water flow through the channel. The latter finding also indicated that water permeation data can provide a good estimate of the pore size for large channels.

Self-accelerating warped braneworlds

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

Carena, Marcela; Lykken, Joseph; Santiago, Jose

2007-01-15

Braneworld models with induced gravity have the potential to replace dark energy as the explanation for the current accelerating expansion of the Universe. The original model of Dvali, Gabadadze, and Porrati (DGP) demonstrated the existence of a 'self-accelerating' branch of background solutions, but suffered from the presence of ghosts. We present a new large class of braneworld models which generalize the DGP model. Our models have negative curvature in the bulk, allow a second brane, and have general brane tensions and localized curvature terms. We exhibit three different kinds of ghosts, associated to the graviton zero mode, the radion, andmore » the longitudinal components of massive graviton modes. The latter two species occur in the DGP model, for negative and positive brane tension, respectively. In our models, we find that the two kinds of DGP ghosts are tightly correlated with each other, but are not always linked to the feature of self-acceleration. Our models are a promising laboratory for understanding the origins and physical meaning of braneworld ghosts, and perhaps for eliminating them altogether.« less

Self-accelerating Warped Braneworlds

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

Carena, Marcela; Lykken, Joseph; /Fermilab

2006-11-01

Braneworld models with induced gravity have the potential to replace dark energy as the explanation for the current accelerating expansion of the Universe. The original model of Dvali, Gabadadze and Porrati (DGP) demonstrated the existence of a ''self-accelerating'' branch of background solutions, but suffered from the presence of ghosts. We present a new large class of braneworld models which generalize the DGP model. Our models have negative curvature in the bulk, allow a second brane, and have general brane tensions and localized curvature terms. We exhibit three different kinds of ghosts, associated to the graviton zero mode, the radion, andmore » the longitudinal components of massive graviton modes. The latter two species occur in the DGP model, for negative and positive brane tension respectively. In our models, we find that the two kinds of DGP ghosts are tightly correlated with each other, but are not always linked to the feature of self-acceleration. Our models are a promising laboratory for understanding the origins and physical meaning of braneworld ghosts, and perhaps for eliminating them altogether.« less

The x-ray time of flight method for investigation of ghosting in amorphous selenium-based flat panel medical x-ray imagers

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

Rau, A.W.; Bakueva, L.; Rowlands, J.A.

2005-10-15

Amorphous selenium (a-Se) based real-time flat-panel imagers (FPIs) are finding their way into the digital radiology department because they offer the practical advantages of digital x-ray imaging combined with an image quality that equals or outperforms that of conventional systems. The temporal imaging characteristics of FPIs can be affected by ghosting (i.e., radiation-induced changes of sensitivity) when the dose to the detector is high (e.g., portal imaging and mammography) or the images are acquired at a high frame rate (e.g., fluoroscopy). In this paper, the x-ray time-of-flight (TOF) method is introduced as a tool for the investigation of ghosting inmore » a-Se photoconductor layers. The method consists of irradiating layers of a-Se with short x-ray pulses. From the current generated in the a-Se layer, ghosting is quantified and the ghosting parameters (charge carrier generation rate and carrier lifetimes and mobilities) are assessed. The x-ray TOF method is novel in that (1) x-ray sensitivity (S) and ghosting parameters can be measured simultaneously (2) the transport of both holes and electrons can be isolated, and (3) the method is applicable to the practical a-Se layer structure with blocking contacts used in FPIs. The x-ray TOF method was applied to an analysis of ghosting in a-Se photoconductor layers under portal imaging conditions, i.e., 1 mm thick a-Se layers, biased at 5 V/{mu}m, were irradiated using a 6 MV LINAC x-ray beam to a total dose (ghosting dose) of 30 Gy. The initial sensitivity (S{sub 0}) of the a-Se layers was 63{+-}2 nC cm{sup -2} cGy{sup -1}. It was found that S decreases to 30% of S{sub 0} after a ghosting dose of 5 Gy and to 21% after 30 Gy at which point no further change in S occurs. At an x-ray intensity of 22 Gy/s (instantaneous dose rate during a LINAC x-ray pulse), the charge carrier generation rate was 1.25{+-}0.1x10{sup 22} ehp m{sup -3} s{sup -1} and, to a first approximation, independent of the ghosting dose. However, both hole and electron transport showed a strong dependence on the ghosting dose: hole transport decreased by 61%, electron transport by up to {approx}80%. Therefore, degradation of both hole and electron transport due to the recombination of mobile charge carriers with trapped carriers (of opposite polarity) were identified as the main cause of ghosting in this study.« less

Adaptive compressive ghost imaging based on wavelet trees and sparse representation.

PubMed

Yu, Wen-Kai; Li, Ming-Fei; Yao, Xu-Ri; Liu, Xue-Feng; Wu, Ling-An; Zhai, Guang-Jie

2014-03-24

Compressed sensing is a theory which can reconstruct an image almost perfectly with only a few measurements by finding its sparsest representation. However, the computation time consumed for large images may be a few hours or more. In this work, we both theoretically and experimentally demonstrate a method that combines the advantages of both adaptive computational ghost imaging and compressed sensing, which we call adaptive compressive ghost imaging, whereby both the reconstruction time and measurements required for any image size can be significantly reduced. The technique can be used to improve the performance of all computational ghost imaging protocols, especially when measuring ultra-weak or noisy signals, and can be extended to imaging applications at any wavelength.

Phased array ghost elimination.

PubMed

Kellman, Peter; McVeigh, Elliot R

2006-05-01

Parallel imaging may be applied to cancel ghosts caused by a variety of distortion mechanisms, including distortions such as off-resonance or local flow, which are space variant. Phased array combining coefficients may be calculated that null ghost artifacts at known locations based on a constrained optimization, which optimizes SNR subject to the nulling constraint. The resultant phased array ghost elimination (PAGE) technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation is applied to full field-of-view (FOV) images. The phased array method for ghost elimination may result in greater flexibility in designing acquisition strategies. For example, in multi-shot EPI applications ghosts are typically mitigated by the use of an interleaved phase encode acquisition order. An alternative strategy is to use a sequential, non-interleaved phase encode order and cancel the resultant ghosts using PAGE parallel imaging. Cancellation of ghosts by means of phased array processing makes sequential, non-interleaved phase encode acquisition order practical, and permits a reduction in repetition time, TR, by eliminating the need for echo-shifting. Sequential, non-interleaved phase encode order has benefits of reduced distortion due to off-resonance, in-plane flow and EPI delay misalignment. Furthermore, the use of EPI with PAGE has inherent fat-water separation and has been used to provide off-resonance correction using a technique referred to as lipid elimination with an echo-shifting N/2-ghost acquisition (LEENA), and may further generalized using the multi-point Dixon method. Other applications of PAGE include cancelling ghosts which arise due to amplitude or phase variation during the approach to steady state. Parallel imaging requires estimates of the complex coil sensitivities. In vivo estimates may be derived by temporally varying the phase encode ordering to obtain a full k-space dataset in a scheme similar to the autocalibrating TSENSE method. This scheme is a generalization of the UNFOLD method used for removing aliasing in undersampled acquisitions. The more general scheme may be used to modulate each EPI ghost image to a separate temporal frequency as described in this paper. Copyright (c) 2006 John Wiley & Sons, Ltd.

Phased array ghost elimination

PubMed Central

Kellman, Peter; McVeigh, Elliot R.

2007-01-01

Parallel imaging may be applied to cancel ghosts caused by a variety of distortion mechanisms, including distortions such as off-resonance or local flow, which are space variant. Phased array combining coefficients may be calculated that null ghost artifacts at known locations based on a constrained optimization, which optimizes SNR subject to the nulling constraint. The resultant phased array ghost elimination (PAGE) technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation is applied to full field-of-view (FOV) images. The phased array method for ghost elimination may result in greater flexibility in designing acquisition strategies. For example, in multi-shot EPI applications ghosts are typically mitigated by the use of an interleaved phase encode acquisition order. An alternative strategy is to use a sequential, non-interleaved phase encode order and cancel the resultant ghosts using PAGE parallel imaging. Cancellation of ghosts by means of phased array processing makes sequential, non-interleaved phase encode acquisition order practical, and permits a reduction in repetition time, TR, by eliminating the need for echo-shifting. Sequential, non-interleaved phase encode order has benefits of reduced distortion due to off-resonance, in-plane flow and EPI delay misalignment. Furthermore, the use of EPI with PAGE has inherent fat-water separation and has been used to provide off-resonance correction using a technique referred to as lipid elimination with an echo-shifting N/2-ghost acquisition (LEENA), and may further generalized using the multi-point Dixon method. Other applications of PAGE include cancelling ghosts which arise due to amplitude or phase variation during the approach to steady state. Parallel imaging requires estimates of the complex coil sensitivities. In vivo estimates may be derived by temporally varying the phase encode ordering to obtain a full k-space dataset in a scheme similar to the autocalibrating TSENSE method. This scheme is a generalization of the UNFOLD method used for removing aliasing in undersampled acquisitions. The more general scheme may be used to modulate each EPI ghost image to a separate temporal frequency as described in this paper. PMID:16705636

Automatic correction of echo-planar imaging (EPI) ghosting artifacts in real-time interactive cardiac MRI using sensitivity encoding.

PubMed

Kim, Yoon-Chul; Nielsen, Jon-Fredrik; Nayak, Krishna S

2008-01-01

To develop a method that automatically corrects ghosting artifacts due to echo-misalignment in interleaved gradient-echo echo-planar imaging (EPI) in arbitrary oblique or double-oblique scan planes. An automatic ghosting correction technique was developed based on an alternating EPI acquisition and the phased-array ghost elimination (PAGE) reconstruction method. The direction of k-space traversal is alternated at every temporal frame, enabling lower temporal-resolution ghost-free coil sensitivity maps to be dynamically estimated. The proposed method was compared with conventional one-dimensional (1D) phase correction in axial, oblique, and double-oblique scan planes in phantom and cardiac in vivo studies. The proposed method was also used in conjunction with two-fold acceleration. The proposed method with nonaccelerated acquisition provided excellent suppression of ghosting artifacts in all scan planes, and was substantially more effective than conventional 1D phase correction in oblique and double-oblique scan planes. The feasibility of real-time reconstruction using the proposed technique was demonstrated in a scan protocol with 3.1-mm spatial and 60-msec temporal resolution. The proposed technique with nonaccelerated acquisition provides excellent ghost suppression in arbitrary scan orientations without a calibration scan, and can be useful for real-time interactive imaging, in which scan planes are frequently changed with arbitrary oblique orientations.

Relevance of Web Documents:Ghosts Consensus Method.

ERIC Educational Resources Information Center

Gorbunov, Andrey L.

2002-01-01

Discusses how to improve the quality of Internet search systems and introduces the Ghosts Consensus Method which is free from the drawbacks of digital democracy algorithms and is based on linear programming tasks. Highlights include vector space models; determining relevant documents; and enriching query terms. (LRW)

Evaluation of high frequency ghost cavitation emissions for two different seismic air-gun arrays using numerical modelling

NASA Astrophysics Data System (ADS)

Khodabandeloo, Babak; Landrø, Martin

2017-04-01

Sound is deployed by marine mammals for variety of vital purposes such as finding food, communication, echolocation, etc. On the other hand human activities generate underwater noise. One major type of acoustic source is marine seismic acquisition which is carried out to image layers beneath the seabed exploiting reflected acoustic and elastic waves. Air-gun arrays are the most common and efficient marine seismic sources. Field measurements using broad band hydrophones have revealed that acoustic energies emitted by air-gun arrays contains frequencies from a few Hz up to tens of kHz. Frequencies below 200 Hz benefit seismic imaging and the rest is normally considered as wasted energy. On the other hand, the high frequency range (above 200 Hz) overlaps with hearing curves of many marine mammals and especially toothed whales and may have an impact on their behavior. A phenomenon called ghost cavitation is recently recognized to be responsible for a major part of these high frequencies (> 5 kHz). Acoustic pressure waves of individual air guns reflected from sea surface can cause the hydrostatic pressure to drop towards zero close to the source array. In these regions there is a high probability for water vapor cavity growth and subsequent collapse. We have simulated ghost cavitation cloud using numerical modelling and the results are validated by comparing with field measurements. The model is used to compare the amount of high frequency noise due to ghost cavitation for two different air gun arrays. Both of the arrays have three subarrays but the array distance for the one with 2730 in3 air volume is 6 meters and for the slightly bigger array (3250 in3 in air volume) the subarrays are separated by 8 meters. Simulation results indicate that the second array, despite larger subarray distance, generates stronger ghost cavitation signal.

FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS): Experimental Investigation of Quality of Lensless Ghost Imaging with Pseudo-Thermal Light

NASA Astrophysics Data System (ADS)

Shen, Xia; Bai, Yan-Feng; Qin, Tao; Han, Shen-Sheng

2008-11-01

Factors influencing the quality of lensless ghost imaging are investigated. According to the experimental results, we find that the imaging quality is determined by the number of independent sub light sources on the imaging plane of the reference arm. A qualitative picture based on advanced wave optics is presented to explain the physics behind the experimental phenomena. The present results will be helpful to provide a basis for improving the quality of ghost imaging systems in future works.

Ghost illness in a north Indian village.

PubMed

Freed, R S; Freed, S A

1990-01-01

The substantial number of ghost possessions that came to our attention during fieldwork in a North Indian village in 1977-78 led to a thorough study of ghost beliefs as part of a holistic study of village life. Ghosts are not phantoms floating on the periphery of village life, the concern only of children and the credulous. Rather, the study shows that ghosts are linked with basic Hindu beliefs, village lore, ancient curing practices and theories, the diagnosis of illness and treatment of disease, individual stress and anxiety, and family, lineage, and village histories. Ghost possession, a subsidiary and dramatic form of ghost illness, is behavior in which the ghost speaks from its victim who undergoes a range of alternate states. Unpredictable events and heightened personal stress generally precede episodes of ghost possession. Cases of ghost illness and ghost possession include children and adults of both sexes and a range of ages. Our data contradict the village stereotype that only women suffer from ghost possession. Villagers have recourse to both traditional remedies and Western biomedicine to treat ghost illness.

Ghost Dark Energy with Non-Linear Interaction Term

NASA Astrophysics Data System (ADS)

Ebrahimi, E.

2016-06-01

Here we investigate ghost dark energy (GDE) in the presence of a non-linear interaction term between dark matter and dark energy. To this end we take into account a general form for the interaction term. Then we discuss about different features of three choices of the non-linear interacting GDE. In all cases we obtain equation of state parameter, w D = p/ ρ, the deceleration parameter and evolution equation of the dark energy density parameter (Ω D ). We find that in one case, w D cross the phantom line ( w D < -1). However in two other classes w D can not cross the phantom divide. The coincidence problem can be solved in these models completely and there exist good agreement between the models and observational values of w D , q. We study squared sound speed {vs2}, and find that for one case of non-linear interaction term {vs2} can achieves positive values at late time of evolution.

Ensemble density variational methods with self- and ghost-interaction-corrected functionals

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

Pastorczak, Ewa; Pernal, Katarzyna, E-mail: pernalk@gmail.com

2014-05-14

Ensemble density functional theory (DFT) offers a way of predicting excited-states energies of atomic and molecular systems without referring to a density response function. Despite a significant theoretical work, practical applications of the proposed approximations have been scarce and they do not allow for a fair judgement of the potential usefulness of ensemble DFT with available functionals. In the paper, we investigate two forms of ensemble density functionals formulated within ensemble DFT framework: the Gross, Oliveira, and Kohn (GOK) functional proposed by Gross et al. [Phys. Rev. A 37, 2809 (1988)] alongside the orbital-dependent eDFT form of the functional introducedmore » by Nagy [J. Phys. B 34, 2363 (2001)] (the acronym eDFT proposed in analogy to eHF – ensemble Hartree-Fock method). Local and semi-local ground-state density functionals are employed in both approaches. Approximate ensemble density functionals contain not only spurious self-interaction but also the so-called ghost-interaction which has no counterpart in the ground-state DFT. We propose how to correct the GOK functional for both kinds of interactions in approximations that go beyond the exact-exchange functional. Numerical applications lead to a conclusion that functionals free of the ghost-interaction by construction, i.e., eDFT, yield much more reliable results than approximate self- and ghost-interaction-corrected GOK functional. Additionally, local density functional corrected for self-interaction employed in the eDFT framework yields excitations energies of the accuracy comparable to that of the uncorrected semi-local eDFT functional.« less

Optical image transformation and encryption by phase-retrieval-based double random-phase encoding and compressive ghost imaging

NASA Astrophysics Data System (ADS)

Yuan, Sheng; Yang, Yangrui; Liu, Xuemei; Zhou, Xin; Wei, Zhenzhuo

2018-01-01

An optical image transformation and encryption scheme is proposed based on double random-phase encoding (DRPE) and compressive ghost imaging (CGI) techniques. In this scheme, a secret image is first transformed into a binary image with the phase-retrieval-based DRPE technique, and then encoded by a series of random amplitude patterns according to the ghost imaging (GI) principle. Compressive sensing, corrosion and expansion operations are implemented to retrieve the secret image in the decryption process. This encryption scheme takes the advantage of complementary capabilities offered by the phase-retrieval-based DRPE and GI-based encryption techniques. That is the phase-retrieval-based DRPE is used to overcome the blurring defect of the decrypted image in the GI-based encryption, and the CGI not only reduces the data amount of the ciphertext, but also enhances the security of DRPE. Computer simulation results are presented to verify the performance of the proposed encryption scheme.

Conditions for the cosmological viability of the most general scalar-tensor theories and their applications to extended Galileon dark energy models

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

Felice, Antonio De; Tsujikawa, Shinji, E-mail: antoniod@nu.ac.th, E-mail: shinji@rs.kagu.tus.ac.jp

2012-02-01

In the Horndeski's most general scalar-tensor theories with second-order field equations, we derive the conditions for the avoidance of ghosts and Laplacian instabilities associated with scalar, tensor, and vector perturbations in the presence of two perfect fluids on the flat Friedmann-Lemaître-Robertson-Walker (FLRW) background. Our general results are useful for the construction of theoretically consistent models of dark energy. We apply our formulas to extended Galileon models in which a tracker solution with an equation of state smaller than -1 is present. We clarify the allowed parameter space in which the ghosts and Laplacian instabilities are absent and we numerically confirmmore » that such models are indeed cosmologically viable.« less

Approach for removing ghost-images in remote field eddy current testing of ferromagnetic pipes

NASA Astrophysics Data System (ADS)

Luo, Q. W.; Shi, Y. B.; Wang, Z. G.; Zhang, W.; Zhang, Y.

2016-10-01

In the non-destructive testing of ferromagnetic pipes based on remote field eddy currents, an array of sensing coils is often used to detect local defects. While testing, the image that is obtained by sensing coils exhibits a ghost-image, which originates from both the transmitter and sensing coils passing over the same defects in pipes. Ghost-images are caused by transmitters and lead to undesirable assessments of defects. In order to remove ghost-images, two pickup coils are coaxially set to each other in remote field. Due to the time delay between differential signals tested by the two pickup coils, a Wiener deconvolution filter is used to identify the artificial peaks that lead to ghost-images. Because the sensing coils and two pickup coils all receive the same signal from one transmitter, they all contain the same artificial peaks. By subtracting the artificial peak values obtained by the two pickup coils from the imaging data, the ghost-image caused by the transmitter is eliminated. Finally, a relatively highly accurate image of local defects is obtained by these sensing coils. With proposed method, there is no need to subtract the average value of the sensing coils, and it is sensitive to ringed defects.

Approach for removing ghost-images in remote field eddy current testing of ferromagnetic pipes.

PubMed

Luo, Q W; Shi, Y B; Wang, Z G; Zhang, W; Zhang, Y

2016-10-01

In the non-destructive testing of ferromagnetic pipes based on remote field eddy currents, an array of sensing coils is often used to detect local defects. While testing, the image that is obtained by sensing coils exhibits a ghost-image, which originates from both the transmitter and sensing coils passing over the same defects in pipes. Ghost-images are caused by transmitters and lead to undesirable assessments of defects. In order to remove ghost-images, two pickup coils are coaxially set to each other in remote field. Due to the time delay between differential signals tested by the two pickup coils, a Wiener deconvolution filter is used to identify the artificial peaks that lead to ghost-images. Because the sensing coils and two pickup coils all receive the same signal from one transmitter, they all contain the same artificial peaks. By subtracting the artificial peak values obtained by the two pickup coils from the imaging data, the ghost-image caused by the transmitter is eliminated. Finally, a relatively highly accurate image of local defects is obtained by these sensing coils. With proposed method, there is no need to subtract the average value of the sensing coils, and it is sensitive to ringed defects.

The Ghosts of the School Curriculum: Past, Present and Future

ERIC Educational Resources Information Center

Kenway, Jane

2008-01-01

Ghosts haunt the school curriculum. Charles Dickens' "A Christmas Carol" provides a starting point for thinking about these curriculum ghosts. In the Preface, he states that he has "endeavoured in this Ghostly little book, to raise the Ghost of an Idea". In this article, the author seeks to raise the ghost of an idea, and to…

Evaluating imaging quality between different ghost imaging systems based on the coherent-mode representation

NASA Astrophysics Data System (ADS)

Shen, Qian; Bai, Yanfeng; Shi, Xiaohui; Nan, Suqin; Qu, Lijie; Li, Hengxing; Fu, Xiquan

2017-07-01

The difference in imaging quality between different ghost imaging schemes is studied by using coherent-mode representation of partially coherent fields. It is shown that the difference mainly relies on the distribution changes of the decomposition coefficients of the object imaged when the light source is fixed. For a new-designed imaging scheme, we only need to give the distribution of the decomposition coefficients and compare them with that of the existing imaging system, thus one can predict imaging quality. By choosing several typical ghost imaging systems, we theoretically and experimentally verify our results.

The nature of multiphoton fluorescence from red blood cells

NASA Astrophysics Data System (ADS)

Saytashev, Ilyas; Murphy, Michael; Osseiran, Sam; Spence, Dana M.; Evans, Conor L.; Dantus, Marcos

2016-03-01

We report on the nature of multiphoton excited fluorescence observed from human erythrocytes (red blood cells RBC's) and their "ghosts" following 800nm sub-15 fs excitation. The detected optical signal is assigned as two-photon excited fluorescence from hemoglobin. Our findings are supported by wavelength-resolved fluorescence lifetime decay measurements using time-correlated single photon counting system from RBC's, their ghosts as well as in vitro samples of various fluorophores including riboflavin, NADH, NAD(P)H, hemoglobin. We find that low-energy and short-duration pulses allow two-photon imaging of RBC's, but longer more intense pulses lead to their destruction.

High-performance compression and double cryptography based on compressive ghost imaging with the fast Fourier transform

NASA Astrophysics Data System (ADS)

Leihong, Zhang; Zilan, Pan; Luying, Wu; Xiuhua, Ma

2016-11-01

To solve the problem that large images can hardly be retrieved for stringent hardware restrictions and the security level is low, a method based on compressive ghost imaging (CGI) with Fast Fourier Transform (FFT) is proposed, named FFT-CGI. Initially, the information is encrypted by the sender with FFT, and the FFT-coded image is encrypted by the system of CGI with a secret key. Then the receiver decrypts the image with the aid of compressive sensing (CS) and FFT. Simulation results are given to verify the feasibility, security, and compression of the proposed encryption scheme. The experiment suggests the method can improve the quality of large images compared with conventional ghost imaging and achieve the imaging for large-sized images, further the amount of data transmitted largely reduced because of the combination of compressive sensing and FFT, and improve the security level of ghost images through ciphertext-only attack (COA), chosen-plaintext attack (CPA), and noise attack. This technique can be immediately applied to encryption and data storage with the advantages of high security, fast transmission, and high quality of reconstructed information.

Study on the key technology of optical encryption based on compressive ghost imaging with double random-phase encoding

NASA Astrophysics Data System (ADS)

Zhang, Leihong; Pan, Zilan; Liang, Dong; Ma, Xiuhua; Zhang, Dawei

2015-12-01

An optical encryption method based on compressive ghost imaging (CGI) with double random-phase encoding (DRPE), named DRPE-CGI, is proposed. The information is first encrypted by the sender with DRPE, the DRPE-coded image is encrypted by the system of computational ghost imaging with a secret key. The key of N random-phase vectors is generated by the sender and will be shared with the receiver who is the authorized user. The receiver decrypts the DRPE-coded image with the key, with the aid of CGI and a compressive sensing technique, and then reconstructs the original information by the technique of DRPE-decoding. The experiments suggest that cryptanalysts cannot get any useful information about the original image even if they eavesdrop 60% of the key at a given time, so the security of DRPE-CGI is higher than that of the security of conventional ghost imaging. Furthermore, this method can reduce 40% of the information quantity compared with ghost imaging while the qualities of reconstructing the information are the same. It can also improve the quality of the reconstructed plaintext information compared with DRPE-GI with the same sampling times. This technique can be immediately applied to encryption and data storage with the advantages of high security, fast transmission, and high quality of reconstructed information.

Multiple-image encryption via lifting wavelet transform and XOR operation based on compressive ghost imaging scheme

NASA Astrophysics Data System (ADS)

Li, Xianye; Meng, Xiangfeng; Yang, Xiulun; Wang, Yurong; Yin, Yongkai; Peng, Xiang; He, Wenqi; Dong, Guoyan; Chen, Hongyi

2018-03-01

A multiple-image encryption method via lifting wavelet transform (LWT) and XOR operation is proposed, which is based on a row scanning compressive ghost imaging scheme. In the encryption process, the scrambling operation is implemented for the sparse images transformed by LWT, then the XOR operation is performed on the scrambled images, and the resulting XOR images are compressed in the row scanning compressive ghost imaging, through which the ciphertext images can be detected by bucket detector arrays. During decryption, the participant who possesses his/her correct key-group, can successfully reconstruct the corresponding plaintext image by measurement key regeneration, compression algorithm reconstruction, XOR operation, sparse images recovery, and inverse LWT (iLWT). Theoretical analysis and numerical simulations validate the feasibility of the proposed method.

Why do gelatinized starch granules not dissolve completely? Roles for amylose, protein, and lipid in granule "ghost" integrity.

PubMed

Debet, Martine R; Gidley, Michael J

2007-06-13

After gelatinization in water, starch granules persist in swollen hydrated forms known as ghosts. Three potential mechanisms for ghost formation are tested. Proteins and lipids on the granule surface are found to be a determinant of ghost robustness, but not ghost formation. Proteins inside pre-made maize or wheat starch ghosts are degraded extensively by proteases without any apparent change in ghost properties, making an internal protein cross-linking mechanism unlikely. Waxy maize mutants with a range of amylose contents have ghost integrities that correlate with (low) apparent amylose levels. It is hypothesized that ghost formation is due to cross-linking of polysaccharide chains within swollen granules, most likely involving double helices formed from polymer chains that become free to move following heat-induced granule swelling. The size and robustness of granule ghosts is proposed to be determined by the relative rates of swelling and cross-linking, modulated by surface non-polysaccharide components.

Defocusing effects of lensless ghost imaging and ghost diffraction with partially coherent sources

NASA Astrophysics Data System (ADS)

Zhou, Shuang-Xi; Sheng, Wei; Bi, Yu-Bo; Luo, Chun-Ling

2018-04-01

The defocusing effect is inevitable and degrades the image quality in the conventional optical imaging process significantly due to the close confinement of the imaging lens. Based on classical optical coherent theory and linear algebra, we develop a unified formula to describe the defocusing effects of both lensless ghost imaging (LGI) and lensless ghost diffraction (LGD) systems with a partially coherent source. Numerical examples are given to illustrate the influence of defocusing length on the quality of LGI and LGD. We find that the defocusing effects of the test and reference paths in the LGI or LGD systems are entirely different, while the LGD system is more robust against defocusing than the LGI system. Specifically, we find that the imaging process for LGD systems can be viewed as pinhole imaging, which may find applications in ultra-short-wave band imaging without imaging lenses, e.g. x-ray diffraction and γ-ray imaging.

Ghost-Story Telling: Keeping It Appropriate.

ERIC Educational Resources Information Center

Weintraub, Jeff

1996-01-01

Guidelines for telling ghost stories at camp involve considering children's fears at different ages, telling age appropriate stories, determining appropriate times for telling ghost stories, and minimizing fear when a child becomes frightened by a ghost story. Includes tips on the selection, preparation, and presentation of ghost stories. (LP)

Ghost-tree: creating hybrid-gene phylogenetic trees for diversity analyses.

PubMed

Fouquier, Jennifer; Rideout, Jai Ram; Bolyen, Evan; Chase, John; Shiffer, Arron; McDonald, Daniel; Knight, Rob; Caporaso, J Gregory; Kelley, Scott T

2016-02-24

Fungi play critical roles in many ecosystems, cause serious diseases in plants and animals, and pose significant threats to human health and structural integrity problems in built environments. While most fungal diversity remains unknown, the development of PCR primers for the internal transcribed spacer (ITS) combined with next-generation sequencing has substantially improved our ability to profile fungal microbial diversity. Although the high sequence variability in the ITS region facilitates more accurate species identification, it also makes multiple sequence alignment and phylogenetic analysis unreliable across evolutionarily distant fungi because the sequences are hard to align accurately. To address this issue, we created ghost-tree, a bioinformatics tool that integrates sequence data from two genetic markers into a single phylogenetic tree that can be used for diversity analyses. Our approach starts with a "foundation" phylogeny based on one genetic marker whose sequences can be aligned across organisms spanning divergent taxonomic groups (e.g., fungal families). Then, "extension" phylogenies are built for more closely related organisms (e.g., fungal species or strains) using a second more rapidly evolving genetic marker. These smaller phylogenies are then grafted onto the foundation tree by mapping taxonomic names such that each corresponding foundation-tree tip would branch into its new "extension tree" child. We applied ghost-tree to graft fungal extension phylogenies derived from ITS sequences onto a foundation phylogeny derived from fungal 18S sequences. Our analysis of simulated and real fungal ITS data sets found that phylogenetic distances between fungal communities computed using ghost-tree phylogenies explained significantly more variance than non-phylogenetic distances. The phylogenetic metrics also improved our ability to distinguish small differences (effect sizes) between microbial communities, though results were similar to non-phylogenetic methods for larger effect sizes. The Silva/UNITE-based ghost tree presented here can be easily integrated into existing fungal analysis pipelines to enhance the resolution of fungal community differences and improve understanding of these communities in built environments. The ghost-tree software package can also be used to develop phylogenetic trees for other marker gene sets that afford different taxonomic resolution, or for bridging genome trees with amplicon trees. ghost-tree is pip-installable. All source code, documentation, and test code are available under the BSD license at https://github.com/JTFouquier/ghost-tree .

GHOST: global hepatitis outbreak and surveillance technology.

PubMed

Longmire, Atkinson G; Sims, Seth; Rytsareva, Inna; Campo, David S; Skums, Pavel; Dimitrova, Zoya; Ramachandran, Sumathi; Medrzycki, Magdalena; Thai, Hong; Ganova-Raeva, Lilia; Lin, Yulin; Punkova, Lili T; Sue, Amanda; Mirabito, Massimo; Wang, Silver; Tracy, Robin; Bolet, Victor; Sukalac, Thom; Lynberg, Chris; Khudyakov, Yury

2017-12-06

Hepatitis C is a major public health problem in the United States and worldwide. Outbreaks of hepatitis C virus (HCV) infections associated with unsafe injection practices, drug diversion, and other exposures to blood are difficult to detect and investigate. Effective HCV outbreak investigation requires comprehensive surveillance and robust case investigation. We previously developed and validated a methodology for the rapid and cost-effective identification of HCV transmission clusters. Global Hepatitis Outbreak and Surveillance Technology (GHOST) is a cloud-based system enabling users, regardless of computational expertise, to analyze and visualize transmission clusters in an independent, accurate and reproducible way. We present and explore performance of several GHOST implemented algorithms using next-generation sequencing data experimentally obtained from hypervariable region 1 of genetically related and unrelated HCV strains. GHOST processes data from an entire MiSeq run in approximately 3 h. A panel of seven specimens was used for preparation of six repeats of MiSeq libraries. Testing sequence data from these libraries by GHOST showed a consistent transmission linkage detection, testifying to high reproducibility of the system. Lack of linkage among genetically unrelated HCV strains and constant detection of genetic linkage between HCV strains from known transmission pairs and from follow-up specimens at different levels of MiSeq-read sampling indicate high specificity and sensitivity of GHOST in accurate detection of HCV transmission. GHOST enables automatic extraction of timely and relevant public health information suitable for guiding effective intervention measures. It is designed as a virtual diagnostic system intended for use in molecular surveillance and outbreak investigations rather than in research. The system produces accurate and reproducible information on HCV transmission clusters for all users, irrespective of their level of bioinformatics expertise. Improvement in molecular detection capacity will contribute to increasing the rate of transmission detection, thus providing opportunity for rapid, accurate and effective response to outbreaks of hepatitis C. Although GHOST was originally developed for hepatitis C surveillance, its modular structure is readily applicable to other infectious diseases. Worldwide availability of GHOST for the detection of HCV transmissions will foster deeper involvement of public health researchers and practitioners in hepatitis C outbreak investigation.

Optical image encryption via high-quality computational ghost imaging using iterative phase retrieval

NASA Astrophysics Data System (ADS)

Liansheng, Sui; Yin, Cheng; Bing, Li; Ailing, Tian; Krishna Asundi, Anand

2018-07-01

A novel computational ghost imaging scheme based on specially designed phase-only masks, which can be efficiently applied to encrypt an original image into a series of measured intensities, is proposed in this paper. First, a Hadamard matrix with a certain order is generated, where the number of elements in each row is equal to the size of the original image to be encrypted. Each row of the matrix is rearranged into the corresponding 2D pattern. Then, each pattern is encoded into the phase-only masks by making use of an iterative phase retrieval algorithm. These specially designed masks can be wholly or partially used in the process of computational ghost imaging to reconstruct the original information with high quality. When a significantly small number of phase-only masks are used to record the measured intensities in a single-pixel bucket detector, the information can be authenticated without clear visualization by calculating the nonlinear correlation map between the original image and its reconstruction. The results illustrate the feasibility and effectiveness of the proposed computational ghost imaging mechanism, which will provide an effective alternative for enriching the related research on the computational ghost imaging technique.

Beam-induced and cosmic-ray backgrounds observed in the ATLAS detector during the LHC 2012 proton-proton running period

NASA Astrophysics Data System (ADS)

Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.; Abeloos, B.; Aben, R.; Abolins, M.; AbouZeid, O. S.; Abraham, N. L.; Abramowicz, H.; Abreu, H.; Abreu, R.; Abulaiti, Y.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Adelman, J.; Adomeit, S.; Adye, T.; Affolder, A. A.; Agatonovic-Jovin, T.; Agricola, J.; Aguilar-Saavedra, J. A.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Akerstedt, H.; Åkesson, T. P. A.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albrand, S.; Alconada Verzini, M. J.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexopoulos, T.; Alhroob, M.; Aliev, M.; Alimonti, G.; Alison, J.; Alkire, S. P.; Allbrooke, B. M. M.; Allen, B. W.; Allport, P. P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Alvarez Gonzalez, B.; Álvarez Piqueras, D.; Alviggi, M. G.; Amadio, B. T.; Amako, K.; Amaral Coutinho, Y.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amorim, A.; Amoroso, S.; Amram, N.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anders, J. K.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Angelidakis, S.; Angelozzi, I.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antonelli, M.; Antonov, A.; Antos, J.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Arabidze, G.; Arai, Y.; Araque, J. P.; Arce, A. T. H.; Arduh, F. A.; Arduini, G.; Arguin, J.-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Armitage, L. J.; Arnaez, O.; Arnold, H.; Arratia, M.; Arslan, O.; Artamonov, A.; Artoni, G.; Artz, S.; Asai, S.; Asbah, N.; Ashkenazi, A.; Åsman, B.; Asquith, L.; Assamagan, K.; Astalos, R.; Atkinson, M.; Atlay, N. B.; Augsten, K.; Avolio, G.; Axen, B.; Ayoub, M. K.; Azuelos, G.; Baak, M. A.; Baas, A. E.; Baca, M. J.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Bagiacchi, P.; Bagnaia, P.; Bai, Y.; Baines, J. T.; Baker, O. K.; Baldin, E. M.; Balek, P.; Balestri, T.; Balli, F.; Balunas, W. K.; Banas, E.; Banerjee, Sw.; Bannoura, A. A. E.; Barak, L.; Barberio, E. L.; Barberis, D.; Barbero, M.; Barillari, T.; Barklow, T.; Barlow, N.; Barnes, S. L.; Barnett, B. M.; Barnett, R. M.; Barnovska, Z.; Baroncelli, A.; Barone, G.; Barr, A. J.; Barranco Navarro, L.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Bartoldus, R.; Barton, A. E.; Bartos, P.; Basalaev, A.; Bassalat, A.; Basye, A.; Bates, R. L.; Batista, S. J.; Batley, J. R.; Battaglia, M.; Bauce, M.; Bauer, F.; Bawa, H. S.; Beacham, J. B.; Beattie, M. D.; Beau, T.; Beauchemin, P. H.; Bechtle, P.; Beck, H. P.; Becker, K.; Becker, M.; Beckingham, M.; Becot, C.; Beddall, A. J.; Beddall, A.; Bednyakov, V. A.; Bedognetti, M.; Bee, C. P.; Beemster, L. J.; Beermann, T. A.; Begel, M.; Behr, J. K.; Belanger-Champagne, C.; Bell, A. S.; Bella, G.; Bellagamba, L.; Bellerive, A.; Bellomo, M.; Belotskiy, K.; Beltramello, O.; Belyaev, N. L.; Benary, O.; Benchekroun, D.; Bender, M.; Bendtz, K.; Benekos, N.; Benhammou, Y.; Benhar Noccioli, E.; Benitez, J.; Benitez Garcia, J. A.; Benjamin, D. P.; Bensinger, J. R.; Bentvelsen, S.; Beresford, L.; Beretta, M.; Berge, D.; Bergeaas Kuutmann, E.; Berger, N.; Berghaus, F.; Beringer, J.; Berlendis, S.; Bernard, N. R.; Bernius, C.; Bernlochner, F. U.; Berry, T.; Berta, P.; Bertella, C.; Bertoli, G.; Bertolucci, F.; Bertram, I. A.; Bertsche, C.; Bertsche, D.; Besjes, G. J.; Bessidskaia Bylund, O.; Bessner, M.; Besson, N.; Betancourt, C.; Bethke, S.; Bevan, A. J.; Bhimji, W.; Bianchi, R. M.; Bianchini, L.; Bianco, M.; Biebel, O.; Biedermann, D.; Bielski, R.; Biesuz, N. V.; Biglietti, M.; Bilbao De Mendizabal, J.; Bilokon, H.; Bindi, M.; Binet, S.; Bingul, A.; Bini, C.; Biondi, S.; Bjergaard, D. M.; Black, C. W.; Black, J. E.; Black, K. M.; Blackburn, D.; Blair, R. E.; Blanchard, J.-B.; Blanco, J. E.; Blazek, T.; Bloch, I.; Blocker, C.; Blum, W.; Blumenschein, U.; Blunier, S.; Bobbink, G. J.; Bobrovnikov, V. S.; Bocchetta, S. S.; Bocci, A.; Bock, C.; Boehler, M.; Boerner, D.; Bogaerts, J. A.; Bogavac, D.; Bogdanchikov, A. G.; Bohm, C.; Boisvert, V.; Bold, T.; Boldea, V.; Boldyrev, A. S.; Bomben, M.; Bona, M.; Boonekamp, M.; Borisov, A.; Borissov, G.; Bortfeldt, J.; Bortoletto, D.; Bortolotto, V.; Bos, K.; Boscherini, D.; Bosman, M.; Bossio Sola, J. D.; Boudreau, J.; Bouffard, J.; Bouhova-Thacker, E. V.; Boumediene, D.; Bourdarios, C.; Boutle, S. K.; Boveia, A.; Boyd, J.; Boyko, I. R.; Bracinik, J.; Brandt, A.; Brandt, G.; Brandt, O.; Bratzler, U.; Brau, B.; Brau, J. E.; Braun, H. M.; Breaden Madden, W. D.; Brendlinger, K.; Brennan, A. J.; Brenner, L.; Brenner, R.; Bressler, S.; Bristow, T. M.; Britton, D.; Britzger, D.; Brochu, F. M.; Brock, I.; Brock, R.; Brooijmans, G.; Brooks, T.; Brooks, W. K.; Brosamer, J.; Brost, E.; Broughton, J. H.; Bruce, R.; Bruckman de Renstrom, P. A.; Bruncko, D.; Bruneliere, R.; Bruni, A.; Bruni, G.; Brunt, BH; Bruschi, M.; Bruscino, N.; Bryant, P.; Bryngemark, L.; Buanes, T.; Buat, Q.; Buchholz, P.; Buckley, A. G.; Budagov, I. A.; Buehrer, F.; Bugge, M. K.; Bulekov, O.; Bullock, D.; Burckhart, H.; Burdin, S.; Burgard, C. D.; Burghgrave, B.; Burka, K.; Burke, S.; Burmeister, I.; Busato, E.; Büscher, D.; Büscher, V.; Bussey, P.; Butler, J. M.; Butt, A. I.; Buttar, C. M.; Butterworth, J. M.; Butti, P.; Buttinger, W.; Buzatu, A.; Buzykaev, A. R.; Cabrera Urbán, S.; Caforio, D.; Cairo, V. M.; Cakir, O.; Calace, N.; Calafiura, P.; Calandri, A.; Calderini, G.; Calfayan, P.; Caloba, L. P.; Calvet, D.; Calvet, S.; Calvet, T. P.; Camacho Toro, R.; Camarda, S.; Camarri, P.; Cameron, D.; Caminal Armadans, R.; Camincher, C.; Campana, S.; Campanelli, M.; Campoverde, A.; Canale, V.; Canepa, A.; Cano Bret, M.; Cantero, J.; Cantrill, R.; Cao, T.; Capeans Garrido, M. D. M.; Caprini, I.; Caprini, M.; Capua, M.; Caputo, R.; Carbone, R. M.; Cardarelli, R.; Cardillo, F.; Carli, T.; Carlino, G.; Carminati, L.; Caron, S.; Carquin, E.; Carrillo-Montoya, G. D.; Carter, J. R.; Carvalho, J.; Casadei, D.; Casado, M. P.; Casolino, M.; Casper, D. W.; Castaneda-Miranda, E.; Castelli, A.; Castillo Gimenez, V.; Castro, N. F.; Catinaccio, A.; Catmore, J. R.; Cattai, A.; Caudron, J.; Cavaliere, V.; Cavallaro, E.; Cavalli, D.; Cavalli-Sforza, M.; Cavasinni, V.; Ceradini, F.; Cerda Alberich, L.; Cerio, B. C.; Cerqueira, A. S.; Cerri, A.; Cerrito, L.; Cerutti, F.; Cerv, M.; Cervelli, A.; Cetin, S. A.; Chafaq, A.; Chakraborty, D.; Chalupkova, I.; Chan, S. K.; Chan, Y. L.; Chang, P.; Chapman, J. D.; Charlton, D. G.; Chatterjee, A.; Chau, C. C.; Chavez Barajas, C. A.; Che, S.; Cheatham, S.; Chegwidden, A.; Chekanov, S.; Chekulaev, S. V.; Chelkov, G. A.; Chelstowska, M. A.; Chen, C.; Chen, H.; Chen, K.; Chen, S.; Chen, S.; Chen, X.; Chen, Y.; Cheng, H. C.; Cheng, H. J.; Cheng, Y.; Cheplakov, A.; Cheremushkina, E.; Cherkaoui El Moursli, R.; Chernyatin, V.; Cheu, E.; Chevalier, L.; Chiarella, V.; Chiarelli, G.; Chiodini, G.; Chisholm, A. S.; Chitan, A.; Chizhov, M. V.; Choi, K.; Chomont, A. R.; Chouridou, S.; Chow, B. K. B.; Christodoulou, V.; Chromek-Burckhart, D.; Chudoba, J.; Chuinard, A. J.; Chwastowski, J. J.; Chytka, L.; Ciapetti, G.; Ciftci, A. K.; Cinca, D.; Cindro, V.; Cioara, I. A.; Ciocio, A.; Cirotto, F.; Citron, Z. H.; Ciubancan, M.; Clark, A.; Clark, B. L.; Clark, M. R.; Clark, P. J.; Clarke, R. N.; Clement, C.; Coadou, Y.; Cobal, M.; Coccaro, A.; Cochran, J.; Coffey, L.; Colasurdo, L.; Cole, B.; Cole, S.; Colijn, A. P.; Collot, J.; Colombo, T.; Compostella, G.; Conde Muiño, P.; Coniavitis, E.; Connell, S. H.; Connelly, I. A.; Consorti, V.; Constantinescu, S.; Conta, C.; Conti, G.; Conventi, F.; Cooke, M.; Cooper, B. D.; Cooper-Sarkar, A. M.; Cornelissen, T.; Corradi, M.; Corriveau, F.; Corso-Radu, A.; Cortes-Gonzalez, A.; Cortiana, G.; Costa, G.; Costa, M. J.; Costanzo, D.; Cottin, G.; Cowan, G.; Cox, B. E.; Cranmer, K.; Crawley, S. J.; Cree, G.; Crépé-Renaudin, S.; Crescioli, F.; Cribbs, W. A.; Crispin Ortuzar, M.; Cristinziani, M.; Croft, V.; Crosetti, G.; Cuhadar Donszelmann, T.; Cummings, J.; Curatolo, M.; Cúth, J.; Cuthbert, C.; Czirr, H.; Czodrowski, P.; D'Auria, S.; D'Onofrio, M.; Da Cunha Sargedas De Sousa, M. J.; Da Via, C.; Dabrowski, W.; Dai, T.; Dale, O.; Dallaire, F.; Dallapiccola, C.; Dam, M.; Dandoy, J. R.; Dang, N. P.; Daniells, A. C.; Dann, N. S.; Danninger, M.; Dano Hoffmann, M.; Dao, V.; Darbo, G.; Darmora, S.; Dassoulas, J.; Dattagupta, A.; Davey, W.; David, C.; Davidek, T.; Davies, M.; Davison, P.; Davygora, Y.; Dawe, E.; Dawson, I.; Daya-Ishmukhametova, R. K.; De, K.; de Asmundis, R.; De Benedetti, A.; De Castro, S.; De Cecco, S.; De Groot, N.; de Jong, P.; De la Torre, H.; De Lorenzi, F.; De Pedis, D.; De Salvo, A.; De Sanctis, U.; De Santo, A.; De Vivie De Regie, J. B.; Dearnaley, W. J.; Debbe, R.; Debenedetti, C.; Dedovich, D. V.; Deigaard, I.; Del Peso, J.; Del Prete, T.; Delgove, D.; Deliot, F.; Delitzsch, C. 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G.; Zhu, H.; Zhu, J.; Zhu, Y.; Zhuang, X.; Zhukov, K.; Zibell, A.; Zieminska, D.; Zimine, N. I.; Zimmermann, C.; Zimmermann, S.; Zinonos, Z.; Zinser, M.; Ziolkowski, M.; Živković, L.; Zobernig, G.; Zoccoli, A.; zur Nedden, M.; Zurzolo, G.; Zwalinski, L.

2016-05-01

This paper discusses various observations on beam-induced and cosmic-ray backgrounds in the ATLAS detector during the LHC 2012 proton-proton run. Building on published results based on 2011 data, the correlations between background and residual pressure of the beam vacuum are revisited. Ghost charge evolution over 2012 and its role for backgrounds are evaluated. New methods to monitor ghost charge with beam-gas rates are presented and observations of LHC abort gap population by ghost charge are discussed in detail. Fake jets from colliding bunches and from ghost charge are analysed with improved methods, showing that ghost charge in individual radio-frequency buckets of the LHC can be resolved. Some results of two short periods of dedicated cosmic-ray background data-taking are shown; in particular cosmic-ray muon induced fake jet rates are compared to Monte Carlo simulations and to the fake jet rates from beam background. A thorough analysis of a particular LHC fill, where abnormally high background was observed, is presented. Correlations between backgrounds and beam intensity losses in special fills with very high β* are studied.

Ghost shrimps (Decapoda: Axiidea: Callianassidae) as producers of an Upper Miocene trace fossil association from sublittoral deposits of Lake Pannon (Vienna Basin, Slovakia)

PubMed Central

Hyžný, Matúš; Šimo, Vladimír; Starek, Dušan

2015-01-01

Numerous trace fossils are described from the Late Miocene sediments of the Bzenec Formation exposed at the Gbely section (the Vienna Basin, Slovakia). During deposition of the sediments the area was part of the large, long-lived brackish to freshwater Lake Pannon. Most of the trace fossils are attributed herein to Egbellichnus jordidegiberti igen et ispec. nov. and are interpreted as burrows produced by decapod crustaceans, specifically by a ghost shrimp of the family Callianassidae. This interpretation is based on two independent lines of evidence: environmental requirements of large bioturbators and the burrow morphology itself. The new ichnotaxon is distinguished from other related ichnotaxa by a combination of typically inclined (roughly at an angle of 45°) cylindrical burrows, absence of lining, and tunnels making loops or bends at approximately right angles. The burrow systems at Gbely document the survival of ghost shrimp long after the closure of all seaways and the origin of Lake Pannon. As today, no ghost shrimp are known from long-lived brackish lakes. Egbellichnus from Gbely is the only, although indirect, record of ghost shrimp from a brackish lake environment reported so far. PMID:26089575

Beam-induced and cosmic-ray backgrounds observed in the ATLAS detector during the LHC 2012 proton-proton running period

DOE PAGES

Aad, G.; Abbott, B.; Abdallah, J.; ...

2016-05-20

This paper discusses various observations on beam-induced and cosmic-ray backgrounds in the ATLAS detector during the LHC 2012 proton-proton run. Building on published results based on 2011 data, the correlations between background and residual pressure of the beam vacuum are revisited. Ghost charge evolution over 2012 and its role for backgrounds are evaluated. New methods to monitor ghost charge with beam-gas rates are presented and observations of LHC abort gap population by ghost charge are discussed in detail. Fake jets from colliding bunches and from ghost charge are analysed with improved methods, showing that ghost charge in individual radio-frequency bucketsmore » of the LHC can be resolved. Some results of two short periods of dedicated cosmic-ray background data-taking are shown; in particular cosmic-ray muon induced fake jet rates are compared to Monte Carlo simulations and to the fake jet rates from beam background. A thorough analysis of a particular LHC fill, where abnormally high background was observed, is presented. Correlations between backgrounds and beam intensity losses in special fills with very high β* are studied.« less

Holographic self-tuning of the cosmological constant

NASA Astrophysics Data System (ADS)

Charmousis, Christos; Kiritsis, Elias; Nitti, Francesco

2017-09-01

We propose a brane-world setup based on gauge/gravity duality in which the four-dimensional cosmological constant is set to zero by a dynamical self-adjustment mechanism. The bulk contains Einstein gravity and a scalar field. We study holographic RG flow solutions, with the standard model brane separating an infinite volume UV region and an IR region of finite volume. For generic values of the brane vacuum energy, regular solutions exist such that the four-dimensional brane is flat. Its position in the bulk is determined dynamically by the junction conditions. Analysis of linear fluctuations shows that a regime of 4-dimensional gravity is possible at large distances, due to the presence of an induced gravity term. The graviton acquires an effective mass, and a five-dimensional regime may exist at large and/or small scales. We show that, for a broad choice of potentials, flat-brane solutions are manifestly stable and free of ghosts. We compute the scalar contribution to the force between brane-localized sources and show that, in certain models, the vDVZ discontinuity is absent and the effective interaction at short distances is mediated by two transverse graviton helicities.

Receiver deghosting in the t-x domain based on super-Gaussianity

NASA Astrophysics Data System (ADS)

Lu, Wenkai; Xu, Ziqiang; Fang, Zhongyu; Wang, Ruiliang; Yan, Chengzhi

2017-01-01

Deghosting methods in the time-space (t-x) domain have attracted a lot of attention because of their flexibility for various source/receiver configurations. Based on the well-known knowledge that the seismic signal has a super-Gaussian distribution, we present a Super-Gaussianity based Receiver Deghosting (SRD) method in the t-x domain. In our method, we denote the upgoing wave and its ghost (downgoing wave) as a single seismic signal, and express the relationship between the upgoing wave and its ghost using two ghost parameters: the sea surface reflection coefficient and the time-shift between the upgoing wave and its ghost. For a single seismic signal, we estimate these two parameters by maximizing the super-Gaussianity of the deghosted output, which is achieved by a 2D grid search method using an adaptively predefined discrete solution space. Since usually a large number of seismic signals are mixed together in a seismic trace, in the proposed method we divide the seismic trace into overlapping frames using a sliding time window with a step of one time sample, and consider each frame as a replacement for a single seismic signal. For a 2D seismic gather, we obtain two 2D maps of the ghost parameters. By assuming that these two parameters vary slowly in the t-x domain, we apply a 2D average filter to these maps, to improve their reliability further. Finally, these deghosted outputs are merged to form the final deghosted result. To demonstrate the flexibility of the proposed method for arbitrary variable depths of the receivers, we apply it to several synthetic and field seismic datasets acquired by variable depth streamer.

Entangled spins and ghost-spins

NASA Astrophysics Data System (ADS)

Jatkar, Dileep P.; Narayan, K.

2017-09-01

We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple quantum mechanical toy models for theories containing negative norm states. We define a single ghost-spin as in [20] as a 2-state spin variable with an indefinite inner product in the state space. We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves), the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part. However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general. For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space where positive norm states always lead to positive entanglement entropy after tracing over the ghost-spins. With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.

Generalized ghost pilgrim dark energy in F(T,TG) cosmology

NASA Astrophysics Data System (ADS)

Sharif, M.; Nazir, Kanwal

2016-07-01

This paper is devoted to study the generalized ghost pilgrim dark energy (PDE) model in F(T,TG) gravity with flat Friedmann-Robertson-Walker (FRW) universe. In this scenario, we reconstruct F(T,TG) models and evaluate the corresponding equation of state (EoS) parameter for different choices of the scale factors. We assume power-law scale factor, scale factor for unification of two phases, intermediate and bouncing scale factor. We study the behavior of reconstructed models and EoS parameters graphically. It is found that all the reconstructed models show decreasing behavior for PDE parameter u = -2. On the other hand, the EoS parameter indicates transition from dust-like matter to phantom era for all choices of the scale factor except intermediate for which this is less than - 1. We conclude that all the results are in agreement with PDE phenomenon.

Deep learning approaches for detection and removal of ghosting artifacts in MR spectroscopy.

PubMed

Kyathanahally, Sreenath P; Döring, André; Kreis, Roland

2018-09-01

To make use of deep learning (DL) methods to detect and remove ghosting artifacts in clinical magnetic resonance spectra of human brain. Deep learning algorithms, including fully connected neural networks, deep-convolutional neural networks, and stacked what-where auto encoders, were implemented to detect and correct MR spectra containing spurious echo ghost signals. The DL methods were trained on a huge database of simulated spectra with and without ghosting artifacts that represent complex variations of ghost-ridden spectra, transformed to time-frequency spectrograms. The trained model was tested on simulated and in vivo spectra. The preliminary results for ghost detection are very promising, reaching almost 100% accuracy, and the DL ghost removal methods show potential in simulated and in vivo spectra, but need further refinement and quantitative testing. Ghosting artifacts in spectroscopy are problematic, as they superimpose with metabolites and lead to inaccurate quantification. Detection and removal of ghosting artifacts using traditional machine learning approaches with feature extraction/selection is difficult, as ghosts appear at different frequencies. Here, we show that DL methods perform extremely well for ghost detection if the spectra are treated as images in the form of time-frequency representations. Further optimization for in vivo spectra will hopefully confirm their "ghostbusting" capacity. Magn Reson Med 80:851-863, 2018. © 2018 International Society for Magnetic Resonance in Medicine. © 2018 International Society for Magnetic Resonance in Medicine.

Pseudo color ghost coding imaging with pseudo thermal light

NASA Astrophysics Data System (ADS)

Duan, De-yang; Xia, Yun-jie

2018-04-01

We present a new pseudo color imaging scheme named pseudo color ghost coding imaging based on ghost imaging but with multiwavelength source modulated by a spatial light modulator. Compared with conventional pseudo color imaging where there is no nondegenerate wavelength spatial correlations resulting in extra monochromatic images, the degenerate wavelength and nondegenerate wavelength spatial correlations between the idle beam and signal beam can be obtained simultaneously. This scheme can obtain more colorful image with higher quality than that in conventional pseudo color coding techniques. More importantly, a significant advantage of the scheme compared to the conventional pseudo color coding imaging techniques is the image with different colors can be obtained without changing the light source and spatial filter.

An Adaptive Deghosting Method in Neural Network-Based Infrared Detectors Nonuniformity Correction

PubMed Central

Li, Yiyang; Jin, Weiqi; Zhu, Jin; Zhang, Xu; Li, Shuo

2018-01-01

The problems of the neural network-based nonuniformity correction algorithm for infrared focal plane arrays mainly concern slow convergence speed and ghosting artifacts. In general, the more stringent the inhibition of ghosting, the slower the convergence speed. The factors that affect these two problems are the estimated desired image and the learning rate. In this paper, we propose a learning rate rule that combines adaptive threshold edge detection and a temporal gate. Through the noise estimation algorithm, the adaptive spatial threshold is related to the residual nonuniformity noise in the corrected image. The proposed learning rate is used to effectively and stably suppress ghosting artifacts without slowing down the convergence speed. The performance of the proposed technique was thoroughly studied with infrared image sequences with both simulated nonuniformity and real nonuniformity. The results show that the deghosting performance of the proposed method is superior to that of other neural network-based nonuniformity correction algorithms and that the convergence speed is equivalent to the tested deghosting methods. PMID:29342857

An Adaptive Deghosting Method in Neural Network-Based Infrared Detectors Nonuniformity Correction.

PubMed

Li, Yiyang; Jin, Weiqi; Zhu, Jin; Zhang, Xu; Li, Shuo

2018-01-13

The problems of the neural network-based nonuniformity correction algorithm for infrared focal plane arrays mainly concern slow convergence speed and ghosting artifacts. In general, the more stringent the inhibition of ghosting, the slower the convergence speed. The factors that affect these two problems are the estimated desired image and the learning rate. In this paper, we propose a learning rate rule that combines adaptive threshold edge detection and a temporal gate. Through the noise estimation algorithm, the adaptive spatial threshold is related to the residual nonuniformity noise in the corrected image. The proposed learning rate is used to effectively and stably suppress ghosting artifacts without slowing down the convergence speed. The performance of the proposed technique was thoroughly studied with infrared image sequences with both simulated nonuniformity and real nonuniformity. The results show that the deghosting performance of the proposed method is superior to that of other neural network-based nonuniformity correction algorithms and that the convergence speed is equivalent to the tested deghosting methods.

Intensity-enhanced MART for tomographic PIV

NASA Astrophysics Data System (ADS)

Wang, HongPing; Gao, Qi; Wei, RunJie; Wang, JinJun

2016-05-01

A novel technique to shrink the elongated particles and suppress the ghost particles in particle reconstruction of tomographic particle image velocimetry is presented. This method, named as intensity-enhanced multiplicative algebraic reconstruction technique (IntE-MART), utilizes an inverse diffusion function and an intensity suppressing factor to improve the quality of particle reconstruction and consequently the precision of velocimetry. A numerical assessment about vortex ring motion with and without image noise is performed to evaluate the new algorithm in terms of reconstruction, particle elongation and velocimetry. The simulation is performed at seven different seeding densities. The comparison of spatial filter MART and IntE-MART on the probability density function of particle peak intensity suggests that one of the local minima of the distribution can be used to separate the ghosts and actual particles. Thus, ghost removal based on IntE-MART is also introduced. To verify the application of IntE-MART, a real plate turbulent boundary layer experiment is performed. The result indicates that ghost reduction can increase the accuracy of RMS of velocity field.

High-resolution computational ghost imaging and ghost diffraction through turbulence via a beam-shaping method

NASA Astrophysics Data System (ADS)

Luo, Chun-Ling; Zhuo, Ling-Qing

2017-01-01

Imaging through atmospheric turbulence is a topic with a long history and grand challenges still exist in the remote sensing and astro observation fields. In this letter, we try to propose a simple scheme to improve the resolution of imaging through turbulence based on the computational ghost imaging (CGI) and computational ghost diffraction (CGD) setup via the laser beam shaping techniques. A unified theory of CGI and CGD through turbulence with the multi-Gaussian shaped incoherent source is developed, and numerical examples are given to see clearly the effects of the system parameters to CGI and CGD. Our results show that the atmospheric effect to the CGI and CGD system is closely related to the propagation distance between the source and the object. In addition, by properly increasing the beam order of the multi-Gaussian source, we can improve the resolution of CGI and CGD through turbulence relative to the commonly used Gaussian source. Therefore our results may find applications in remote sensing and astro observation.

Single-pixel computational ghost imaging with helicity-dependent metasurface hologram.

PubMed

Liu, Hong-Chao; Yang, Biao; Guo, Qinghua; Shi, Jinhui; Guan, Chunying; Zheng, Guoxing; Mühlenbernd, Holger; Li, Guixin; Zentgraf, Thomas; Zhang, Shuang

2017-09-01

Different optical imaging techniques are based on different characteristics of light. By controlling the abrupt phase discontinuities with different polarized incident light, a metasurface can host a phase-only and helicity-dependent hologram. In contrast, ghost imaging (GI) is an indirect imaging modality to retrieve the object information from the correlation of the light intensity fluctuations. We report single-pixel computational GI with a high-efficiency reflective metasurface in both simulations and experiments. Playing a fascinating role in switching the GI target with different polarized light, the metasurface hologram generates helicity-dependent reconstructed ghost images and successfully introduces an additional security lock in a proposed optical encryption scheme based on the GI. The robustness of our encryption scheme is further verified with the vulnerability test. Building the first bridge between the metasurface hologram and the GI, our work paves the way to integrate their applications in the fields of optical communications, imaging technology, and security.

Single-pixel computational ghost imaging with helicity-dependent metasurface hologram

PubMed Central

Liu, Hong-Chao; Yang, Biao; Guo, Qinghua; Shi, Jinhui; Guan, Chunying; Zheng, Guoxing; Mühlenbernd, Holger; Li, Guixin; Zentgraf, Thomas; Zhang, Shuang

2017-01-01

Different optical imaging techniques are based on different characteristics of light. By controlling the abrupt phase discontinuities with different polarized incident light, a metasurface can host a phase-only and helicity-dependent hologram. In contrast, ghost imaging (GI) is an indirect imaging modality to retrieve the object information from the correlation of the light intensity fluctuations. We report single-pixel computational GI with a high-efficiency reflective metasurface in both simulations and experiments. Playing a fascinating role in switching the GI target with different polarized light, the metasurface hologram generates helicity-dependent reconstructed ghost images and successfully introduces an additional security lock in a proposed optical encryption scheme based on the GI. The robustness of our encryption scheme is further verified with the vulnerability test. Building the first bridge between the metasurface hologram and the GI, our work paves the way to integrate their applications in the fields of optical communications, imaging technology, and security. PMID:28913433

Dipolar dark matter with massive bigravity

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

Blanchet, Luc; Heisenberg, Lavinia; Department of Physics & The Oskar Klein Centre, AlbaNova University Centre,Roslagstullsbacken 21, 10691 Stockholm

2015-12-14

Massive gravity theories have been developed as viable IR modifications of gravity motivated by dark energy and the problem of the cosmological constant. On the other hand, modified gravity and modified dark matter theories were developed with the aim of solving the problems of standard cold dark matter at galactic scales. Here we propose to adapt the framework of ghost-free massive bigravity theories to reformulate the problem of dark matter at galactic scales. We investigate a promising alternative to dark matter called dipolar dark matter (DDM) in which two different species of dark matter are separately coupled to the twomore » metrics of bigravity and are linked together by an internal vector field. We show that this model successfully reproduces the phenomenology of dark matter at galactic scales (i.e. MOND) as a result of a mechanism of gravitational polarisation. The model is safe in the gravitational sector, but because of the particular couplings of the matter fields and vector field to the metrics, a ghost in the decoupling limit is present in the dark matter sector. However, it might be possible to push the mass of the ghost beyond the strong coupling scale by an appropriate choice of the parameters of the model. Crucial questions to address in future work are the exact mass of the ghost, and the cosmological implications of the model.« less

Dipolar dark matter with massive bigravity

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

Blanchet, Luc; Heisenberg, Lavinia, E-mail: blanchet@iap.fr, E-mail: laviniah@kth.se

2015-12-01

Massive gravity theories have been developed as viable IR modifications of gravity motivated by dark energy and the problem of the cosmological constant. On the other hand, modified gravity and modified dark matter theories were developed with the aim of solving the problems of standard cold dark matter at galactic scales. Here we propose to adapt the framework of ghost-free massive bigravity theories to reformulate the problem of dark matter at galactic scales. We investigate a promising alternative to dark matter called dipolar dark matter (DDM) in which two different species of dark matter are separately coupled to the twomore » metrics of bigravity and are linked together by an internal vector field. We show that this model successfully reproduces the phenomenology of dark matter at galactic scales (i.e. MOND) as a result of a mechanism of gravitational polarisation. The model is safe in the gravitational sector, but because of the particular couplings of the matter fields and vector field to the metrics, a ghost in the decoupling limit is present in the dark matter sector. However, it might be possible to push the mass of the ghost beyond the strong coupling scale by an appropriate choice of the parameters of the model. Crucial questions to address in future work are the exact mass of the ghost, and the cosmological implications of the model.« less

"Walking with a Ghost": Arts-Based Research, Music Videos, and the Re-Performing Body

ERIC Educational Resources Information Center

Taylor, Pamela G.; Wilder, Shannon O.; Helms, Kathryn R.

2007-01-01

In folk-rock duo Tegan and Sara's 2004 music video "Walking with a Ghost," two women face one another, mirrored images in black and white. One is dressed in black--grunge shirt, pants and boots, while the other stands barefoot in a simple white dress. The black-clad figure removes three red paper hearts from her twin's chest, leaving crimson…

Confronting the Ghost of Stalin: Euro-Atlantic Efforts to Secure Georgia

DTIC Science & Technology

2007-12-01

power. In evaluating the causes and results of international regimes, Stephen Krasner listed power and self-interest among values and principles as... internal processes of these larger democracies. Through transnational and transgovernmental coalitions, as well as emphasis on shared community values ...Force Academy, 1993 M.S. in International Relations, Troy State University, 2005 Submitted in partial fulfillment of the requirements for the

Gauge fixing in higher-derivative gravity

NASA Astrophysics Data System (ADS)

Bartoli, A.; Julve, J.; Sánchez, E. J.

1999-07-01

Linearized 4-derivative gravity with a general gauge-fixing term is considered. By a Legendre transform and a suitable diagonalization procedure it is cast into a second-order equivalent form where the nature of the physical degrees of freedom, the gauge ghosts, the Weyl ghosts and the intriguing `third ghosts', characteristic to higher-derivative theories, is made explicit. The symmetries of the theory and the structure of the compensating Faddeev-Popov ghost sector exhibit non-trivial peculiarities. The unitarity breaking negative-norm Weyl ghosts, already present in the diff-invariant theory, are out of the reach of the ghost cancellation BRST mechanism.

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

Lee, Kyongwoon

Microstructural characteristics of the CGHAZ (coarse grained heat affected zone) made of the 2.25Cr-1Mo-V-Ti material for the thermal power plant boiler tube were discussed using the technique of tint etching. To conduct the micro structural characterization, the sample on which CGHAZ was produced by using a high temperature thermal cycle simulator, Gleeble 3500 equipment was used for comparative analyses using the existing Nital etching (ASTM E407-74) and the alkaline etching (ASTM E40785). The latter was used to observe a specific phase. For the microstructure on which the alkaline etching was experimented, the shape of a black strip (Ghost microstructure) inmore » a few microns was observed, which was not observed from the Nital etching. It was found from the phase identifications based EPMA, EBSD and TEM experiments that the image of the black strip in a few microns represented the alpha phase in which C, Cr and Mo became segregated. In addition, it was verified that austenite and M{sub 23}C{sub 6} phase were present around the segregated zone. Based on such results, the mechanism by which the image of the black strip in a few microns was formed at the CGHAZ. In this study, we have investigated the mechanism of the appeared black strip in the CGHAZ. - Highlights: •Ghost microstructure was observed which was not observed from the nital etching. •Ghost microstructure has high concentrations of carbon and molybdenum than matrix. •Schematic illustration proposed of why Ghost microstructure was generated. •Ghost microstructure caused by partial dissolution of M{sub 23}C{sub 6} precipitation.« less

Theoretical scheme of thermal-light many-ghost imaging by Nth-order intensity correlation

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

Liu Yingchuan; College of Mathematics and Physics, University of South China, Hengyang 421001; Kuang Leman

2011-05-15

In this paper, we propose a theoretical scheme of many-ghost imaging in terms of Nth-order correlated thermal light. We obtain the Gaussian thin lens equations in the many-ghost imaging protocol. We show that it is possible to produce N-1 ghost images of an object at different places in a nonlocal fashion by means of a higher order correlated imaging process with an Nth-order correlated thermal source and correlation measurements. We investigate the visibility of the ghost images in the scheme and obtain the upper bounds of the visibility for the Nth-order correlated thermal-light ghost imaging. It is found that themore » visibility of the ghost images can be dramatically enhanced when the order of correlation becomes larger. It is pointed out that the many-ghost imaging phenomenon is an observable physical effect induced by higher order coherence or higher order correlations of optical fields.« less

Influence of some DNA-alkylating drugs on thermal stability, acid and osmotic resistance of the membrane of whole human erythrocytes and their ghosts.

PubMed

Ivanov, I T; Gadjeva, V

2000-09-01

Human erythrocytes and their resealed ghosts were alkylated under identical conditions using three groups of alkylating antitumor agents: mustards, triazenes and chloroethyl nitrosoureas. Osmotic fragility, acid resistance and thermal stability of membranes were changed only in alkylated ghosts in proportion to the concentration of the alkylating agent. All the alkylating agents decreased acid resistance in ghosts. The clinically used drugs sarcolysine, dacarbazine and lomustine all decreased osmotic fragility and thermal stability of ghost membranes depending on their lipophilicity. DM-COOH did not decrease osmotic fragility and thermal stability of ghost membranes, while NEM increased thermal stability of membranes. The preliminary but not subsequent treatment of ghosts with DM-COOH fully abolished the alkylation-induced thermal labilization of ghost membrane proteins while NEM had a partial effect only. The present study gives direct evidence that alkylating agents, having a high therapeutic activity against malignant growth, bind covalently to proteins of cellular membranes.

Ghosting reduction method for color anaglyphs

NASA Astrophysics Data System (ADS)

Chang, An Jin; Kim, Hye Jin; Choi, Jae Wan; Yu, Ki Yun

2008-02-01

Anaglyph is the simplest and the most economical method for 3D visualization. However, anaglyph has several drawbacks such as loss of color or visual discomfort, e.g., region merging and the ghosting effect. In particular, the ghosting effect, which is caused by green penetrating to the left eye, brings on a slight headache, dizziness and vertigo. Therefore, ghosting effects have to be reduced to improve the visual quality and make viewing of the anaglyph comfortable. Since red lightness is increased by penetration by green, the lightness of the red band has to be compensated for. In this paper, a simple deghosting method is proposed using the red lightness difference of the left and right images. We detected a ghosting area with the criterion, which was calculated from the statistics of the difference image, and then the red lightness of the anaglyph was changed to be brighter or darker according to the degree of the difference. The amount of change of red lightness was determined empirically. These adjustments simultaneously reduced the ghosting effect and preserved the color lightness within the non-ghosting area. The proposed deghosting method works well, and the goal of this paper was to detect the ghosting area automatically and to reduce the ghosting.

Not a Humbug: the evolution of patient-centred medical decision-making.

PubMed

Trump, Benjamin D; Linkov, Faina; Edwards, Robert P; Linkov, Igor

2015-12-01

This 'Christmas Issue'-type paper uses the framework of 'A Christmas Carol' to tell about the evolution of decision-making in evidence-based medicine (EBM). The Ghost of the Past represents paternalistic medicine, the Ghost of the Present symbolises EBM, while the Ghost of the Future serves as a patient-centred system where research data and tools of decision science are jointly used to make optimal medical decisions for individual patients. We argue that this shift towards a patient-centred approach to EBM and medical care is the next step in the evolution of medical decision-making, which would help to empower patients with the capability to make educated decisions throughout the course of their medical treatment.

Disturbance facilitates the coexistence of antagonistic ecosystem engineers in California estuaries.

PubMed

Castorani, Max C N; Hovel, Kevin A; Williams, Susan L; Baskett, Marissa L

2014-08-01

Ecological theory predicts that interactions between antagonistic ecosystem engineers can lead to local competitive exclusion, but disturbance can facilitate broader coexistence. However, few empirical studies have tested the potential for disturbance to mediate competition between engineers. We examined the capacity for disturbance and habitat modification to explain the disjunct distributions of two benthic ecosystem engineers, eelgrass Zostera marina and the burrowing ghost shrimp Neotrypaea californiensis, in two California estuaries. Sediment sampling in eelgrass and ghost shrimp patches revealed that ghost shrimp change benthic biogeochemistry over small scales (centimeters) but not patch scales (meters to tens of meters), suggesting a limited capacity for sediment modification to explain species distributions. To determine the relative competitive abilities of engineers, we conducted reciprocal transplantations of ghost shrimp and eelgrass. Local ghost shrimp densities declined rapidly following the addition of eelgrass, and transplanted eelgrass expanded laterally into the surrounding ghost shrimp-dominated areas. When transplanted into eelgrass patches, ghost shrimp failed to persist. Ghost shrimp were also displaced from plots with structural mimics of eelgrass rhizomes and roots, suggesting that autogenic habitat modification by eelgrass is an important mechanism determining ghost shrimp distributions. However, ghost shrimp were able to rapidly colonize experimental disturbances to eelgrass patch edges, which are common in shallow estuaries. We conclude that coexistence in this system is maintained by spatiotemporally asynchronous disturbances and a competition-colonization trade-off: eelgrass is a competitively superior ecosystem engineer, but benthic disturbances permit the coexistence of ghost shrimp at the landscape scale by modulating the availability of space.

Study on the algorithm of computational ghost imaging based on discrete fourier transform measurement matrix

NASA Astrophysics Data System (ADS)

Zhang, Leihong; Liang, Dong; Li, Bei; Kang, Yi; Pan, Zilan; Zhang, Dawei; Gao, Xiumin; Ma, Xiuhua

2016-07-01

On the basis of analyzing the cosine light field with determined analytic expression and the pseudo-inverse method, the object is illuminated by a presetting light field with a determined discrete Fourier transform measurement matrix, and the object image is reconstructed by the pseudo-inverse method. The analytic expression of the algorithm of computational ghost imaging based on discrete Fourier transform measurement matrix is deduced theoretically, and compared with the algorithm of compressive computational ghost imaging based on random measurement matrix. The reconstruction process and the reconstruction error are analyzed. On this basis, the simulation is done to verify the theoretical analysis. When the sampling measurement number is similar to the number of object pixel, the rank of discrete Fourier transform matrix is the same as the one of the random measurement matrix, the PSNR of the reconstruction image of FGI algorithm and PGI algorithm are similar, the reconstruction error of the traditional CGI algorithm is lower than that of reconstruction image based on FGI algorithm and PGI algorithm. As the decreasing of the number of sampling measurement, the PSNR of reconstruction image based on FGI algorithm decreases slowly, and the PSNR of reconstruction image based on PGI algorithm and CGI algorithm decreases sharply. The reconstruction time of FGI algorithm is lower than that of other algorithms and is not affected by the number of sampling measurement. The FGI algorithm can effectively filter out the random white noise through a low-pass filter and realize the reconstruction denoising which has a higher denoising capability than that of the CGI algorithm. The FGI algorithm can improve the reconstruction accuracy and the reconstruction speed of computational ghost imaging.

Combining extrapolation with ghost interaction correction in range-separated ensemble density functional theory for excited states

NASA Astrophysics Data System (ADS)

Alam, Md. Mehboob; Deur, Killian; Knecht, Stefan; Fromager, Emmanuel

2017-11-01

The extrapolation technique of Savin [J. Chem. Phys. 140, 18A509 (2014)], which was initially applied to range-separated ground-state-density-functional Hamiltonians, is adapted in this work to ghost-interaction-corrected (GIC) range-separated ensemble density-functional theory (eDFT) for excited states. While standard extrapolations rely on energies that decay as μ-2 in the large range-separation-parameter μ limit, we show analytically that (approximate) range-separated GIC ensemble energies converge more rapidly (as μ-3) towards their pure wavefunction theory values (μ → +∞ limit), thus requiring a different extrapolation correction. The purpose of such a correction is to further improve on the convergence and, consequently, to obtain more accurate excitation energies for a finite (and, in practice, relatively small) μ value. As a proof of concept, we apply the extrapolation method to He and small molecular systems (viz., H2, HeH+, and LiH), thus considering different types of excitations such as Rydberg, charge transfer, and double excitations. Potential energy profiles of the first three and four singlet Σ+ excitation energies in HeH+ and H2, respectively, are studied with a particular focus on avoided crossings for the latter. Finally, the extraction of individual state energies from the ensemble energy is discussed in the context of range-separated eDFT, as a perspective.

Late-time cosmic acceleration: ABCD of dark energy and modified theories of gravity

NASA Astrophysics Data System (ADS)

Sami, M.; Myrzakulov, R.

2016-10-01

We briefly review the problems and prospects of the standard lore of dark energy. We have shown that scalar fields, in principle, cannot address the cosmological constant problem. Indeed, a fundamental scalar field is faced with a similar problem dubbed naturalness. In order to keep the discussion pedagogical, aimed at a wider audience, we have avoided technical complications in several places and resorted to heuristic arguments based on physical perceptions. We presented underlying ideas of modified theories based upon chameleon mechanism and Vainshtein screening. We have given a lucid illustration of recently investigated ghost-free nonlinear massive gravity. Again, we have sacrificed rigor and confined to the basic ideas that led to the formulation of the theory. The review ends with a brief discussion on the difficulties of the theory applied to cosmology.

Comparison of the signal-to-noise characteristics of quantum versus thermal ghost imaging

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

O'Sullivan, Malcolm N.; Chan, Kam Wai Clifford; Boyd, Robert W.

2010-11-15

We present a theoretical comparison of the signal-to-noise characteristics of quantum versus thermal ghost imaging. We first calculate the signal-to-noise ratio of each process in terms of its controllable experimental conditions. We show that a key distinction is that a thermal ghost image always resides on top of a large background; the fluctuations in this background constitutes an intrinsic noise source for thermal ghost imaging. In contrast, there is a negligible intrinsic background to a quantum ghost image. However, for practical reasons involving achievable illumination levels, acquisition times for thermal ghost images are often much shorter than those for quantummore » ghost images. We provide quantitative predictions for the conditions under which each process provides superior performance. Our conclusion is that each process can provide useful functionality, although under complementary conditions.« less

Dynamic image reconstruction: MR movies from motion ghosts.

PubMed

Xiang, Q S; Henkelman, R M

1992-01-01

It has been previously shown that an image with motion ghost artifacts can be decomposed into a ghost mask superimposed over a ghost-free image. The present study demonstrates that the ghost components carry useful dynamic information and should not be discarded. Specifically, ghosts of different orders indicate the intensity and phase of the corresponding harmonics contained in the quasi-periodically varying spin-density distribution. A summation of the ghosts weighted by appropriate temporal phase factors can give a time-dependent dynamic image that is a movie of the object motion. This dynamic image reconstruction technique does not necessarily require monitoring of the motion and thus is easy to implement and operate. It also has a shorter imaging time than point-by-point imaging of temporal variation, because the periodic motion is more efficiently sampled with a limited number of harmonics recorded in the motion ghosts. This technique was tested in both moving phantoms and volunteers. It is believed to be useful for dynamic imaging of time-varying anatomic structures, such as in the cardiovascular system.

Membrane perturbations of erythrocyte ghosts by spectrin release.

PubMed

Yamaguchi, Takeo; Ozaki, Shinnosuke; Shimomura, Taiji; Terada, Shigeyuki

2007-05-01

The cytoskeleton plays an important role in the stability and function of the membrane. Spectrin release from erythrocyte ghosts makes the membrane more fragile. However, the detail of membrane fragility has remained unclear. In the present study, the effects of incubation temperatures and polyamines on the membrane structure of ghosts under hypotonic conditions have been examined. Upon exposure of ghosts to a hypotonic buffer at 0-37 degrees C, reduction of ghost volume, spectrin release and decrease of band 3-cytoskeleton interactions were clearly observed above 30 degrees C. However, such changes were completely inhibited by spermine and spermidine. Interestingly, conformational changes of spectrin induced at 37 degrees C or 49 degrees C were not suppressed by both polyamines. Flow cytometry of fluorescein isothiocyanate-labelled ghosts exposed to 37 degrees C demonstrated the two peaks corresponding to ghosts with normal spectrin content and decreased one. Taken together, these results indicate that the degree of spectrin release from the membrane under hypotonic conditions is not same in all ghosts, and that polyamines inhibit the spectrin release followed by changes in the membrane structure, but not conformational changes of spectrin.

Salmonella enterica Serovar Enteritidis Ghosts Carrying the Escherichia coli Heat-Labile Enterotoxin B Subunit Are Capable of Inducing Enhanced Protective Immune Responses

PubMed Central

Jawale, Chetan V.

2014-01-01

The Escherichia coli heat-labile enterotoxin B subunit (LTB) is a potent vaccine adjuvant. Salmonella enterica serovar Enteritidis ghosts carrying LTB (S. Enteritidis-LTB ghosts) were genetically constructed using a novel plasmid, pJHL187-LTB, designed for the coexpression of the LTB and E lysis proteins. S. Enteritidis-LTB ghosts were characterized using scanning electron microscopy to visualize their transmembrane tunnel structures. The expression of LTB in S. Enteritidis-LTB ghost preparations was confirmed by immunoblot and enzyme-linked immunosorbent assays. The parenteral adjuvant activity of LTB was demonstrated by immunizing chickens with either S. Enteritidis-LTB ghosts or S. Enteritidis ghosts. Chickens were intramuscularly primed at 5 weeks of age and subsequently boosted at 8 weeks of age. In total, 60 chickens were equally divided into three groups (n = 20 for each): group A, nonvaccinated control; group B, immunized with S. Enteritidis-LTB ghosts; and group C, immunized with S. Enteritidis ghosts. Compared with the nonimmunized chickens (group A), the immunized chickens (groups B and C) exhibited increased titers of plasma IgG and intestinal secretory IgA antibodies. The CD3+ CD4+ subpopulation of T cells was also significantly increased in both immunized groups. Among the immunized chickens, those in group B exhibited significantly increased titers of specific plasma IgG and intestinal secretory IgA (sIgA) antibodies compared with those in group C, indicating the immunomodulatory effects of the LTB adjuvant. Furthermore, both immunized groups exhibited decreased bacterial loads in their feces and internal organs. These results indicate that parenteral immunization with S. Enteritidis-LTB ghosts can stimulate superior induction of systemic and mucosal immune responses compared to immunization with S. Enteritidis ghosts alone, thus conferring efficient protection against salmonellosis. PMID:24671556

Pepper's Ghost

NASA Astrophysics Data System (ADS)

Greenslade, Thomas B.

2011-09-01

Without applications of physics such as counter-weighted sets and backdrops, inclined planes, stage lighting instruments, and other mechanisms for deus ex machina, dramatic productions would revert to the words only—fine for Shakespeare and Becket, but not good for audiences who are accustomed to experiencing plays with the eye as well as the ear. Pepper's Ghost is a 19th-century stage illusion, based on basic optical principles, that can find its way into your introductory classroom.

Minimising back reflections from the common path objective in a fundus camera

NASA Astrophysics Data System (ADS)

Swat, A.

2016-11-01

Eliminating back reflections is critical in the design of a fundus camera with internal illuminating system. As there is very little light reflected from the retina, even excellent antireflective coatings are not sufficient suppression of ghost reflections, therefore the number of surfaces in the common optics in illuminating and imaging paths shall be minimised. Typically a single aspheric objective is used. In the paper an alternative approach, an objective with all spherical surfaces, is presented. As more surfaces are required, more sophisticated method is needed to get rid of back reflections. Typically back reflections analysis, comprise treating subsequent objective surfaces as mirrors, and reflections from the objective surfaces are traced back through the imaging path. This approach can be applied in both sequential and nonsequential ray tracing. It is good enough for system check but not very suitable for early optimisation process in the optical system design phase. There are also available standard ghost control merit function operands in the sequential ray-trace, for example in Zemax system, but these don't allow back ray-trace in an alternative optical path, illumination vs. imaging. What is proposed in the paper, is a complete method to incorporate ghost reflected energy into the raytracing system merit function for sequential mode which is more efficient in optimisation process. Although developed for the purpose of specific case of fundus camera, the method might be utilised in a wider range of applications where ghost control is critical.

50 CFR 697.21 - Gear identification and marking, escape vent, maximum trap size, and ghost panel requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... vent, maximum trap size, and ghost panel requirements. 697.21 Section 697.21 Wildlife and Fisheries... identification and marking, escape vent, maximum trap size, and ghost panel requirements. (a) Gear identification... Administrator finds to be consistent with paragraph (c) of this section. (d) Ghost panel. (1) Lobster traps not...

50 CFR 697.21 - Gear identification and marking, escape vent, maximum trap size, and ghost panel requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... vent, maximum trap size, and ghost panel requirements. 697.21 Section 697.21 Wildlife and Fisheries... identification and marking, escape vent, maximum trap size, and ghost panel requirements. (a) Gear identification... Administrator finds to be consistent with paragraph (c) of this section. (d) Ghost panel. (1) Lobster traps not...

50 CFR 697.21 - Gear identification and marking, escape vent, maximum trap size, and ghost panel requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... vent, maximum trap size, and ghost panel requirements. 697.21 Section 697.21 Wildlife and Fisheries... identification and marking, escape vent, maximum trap size, and ghost panel requirements. (a) Gear identification... Administrator finds to be consistent with paragraph (c) of this section. (d) Ghost panel. (1) Lobster traps not...

Information retrieval based on single-pixel optical imaging with quick-response code

NASA Astrophysics Data System (ADS)

Xiao, Yin; Chen, Wen

2018-04-01

Quick-response (QR) code technique is combined with ghost imaging (GI) to recover original information with high quality. An image is first transformed into a QR code. Then the QR code is treated as an input image in the input plane of a ghost imaging setup. After measurements, traditional correlation algorithm of ghost imaging is utilized to reconstruct an image (QR code form) with low quality. With this low-quality image as an initial guess, a Gerchberg-Saxton-like algorithm is used to improve its contrast, which is actually a post processing. Taking advantage of high error correction capability of QR code, original information can be recovered with high quality. Compared to the previous method, our method can obtain a high-quality image with comparatively fewer measurements, which means that the time-consuming postprocessing procedure can be avoided to some extent. In addition, for conventional ghost imaging, the larger the image size is, the more measurements are needed. However, for our method, images with different sizes can be converted into QR code with the same small size by using a QR generator. Hence, for the larger-size images, the time required to recover original information with high quality will be dramatically reduced. Our method makes it easy to recover a color image in a ghost imaging setup, because it is not necessary to divide the color image into three channels and respectively recover them.

Pulse-compression ghost imaging lidar via coherent detection.

PubMed

Deng, Chenjin; Gong, Wenlin; Han, Shensheng

2016-11-14

Ghost imaging (GI) lidar, as a novel remote sensing technique, has been receiving increasing interest in recent years. By combining pulse-compression technique and coherent detection with GI, we propose a new lidar system called pulse-compression GI lidar. Our analytical results, which are backed up by numerical simulations, demonstrate that pulse-compression GI lidar can obtain the target's spatial intensity distribution, range and moving velocity. Compared with conventional pulsed GI lidar system, pulse-compression GI lidar, without decreasing the range resolution, is easy to obtain high single pulse energy with the use of a long pulse, and the mechanism of coherent detection can eliminate the influence of the stray light, which is helpful to improve the detection sensitivity and detection range.

Optical image hiding based on computational ghost imaging

NASA Astrophysics Data System (ADS)

Wang, Le; Zhao, Shengmei; Cheng, Weiwen; Gong, Longyan; Chen, Hanwu

2016-05-01

Imaging hiding schemes play important roles in now big data times. They provide copyright protections of digital images. In the paper, we propose a novel image hiding scheme based on computational ghost imaging to have strong robustness and high security. The watermark is encrypted with the configuration of a computational ghost imaging system, and the random speckle patterns compose a secret key. Least significant bit algorithm is adopted to embed the watermark and both the second-order correlation algorithm and the compressed sensing (CS) algorithm are used to extract the watermark. The experimental and simulation results show that the authorized users can get the watermark with the secret key. The watermark image could not be retrieved when the eavesdropping ratio is less than 45% with the second-order correlation algorithm, whereas it is less than 20% with the TVAL3 CS reconstructed algorithm. In addition, the proposed scheme is robust against the 'salt and pepper' noise and image cropping degradations.

Optical image encryption scheme with multiple light paths based on compressive ghost imaging

NASA Astrophysics Data System (ADS)

Zhu, Jinan; Yang, Xiulun; Meng, Xiangfeng; Wang, Yurong; Yin, Yongkai; Sun, Xiaowen; Dong, Guoyan

2018-02-01

An optical image encryption method with multiple light paths is proposed based on compressive ghost imaging. In the encryption process, M random phase-only masks (POMs) are generated by means of logistic map algorithm, and these masks are then uploaded to the spatial light modulator (SLM). The collimated laser light is divided into several beams by beam splitters as it passes through the SLM, and the light beams illuminate the secret images, which are converted into sparse images by discrete wavelet transform beforehand. Thus, the secret images are simultaneously encrypted into intensity vectors by ghost imaging. The distances between the SLM and secret images vary and can be used as the main keys with original POM and the logistic map algorithm coefficient in the decryption process. In the proposed method, the storage space can be significantly decreased and the security of the system can be improved. The feasibility, security and robustness of the method are further analysed through computer simulations.

Calibration artefacts in radio interferometry - II. Ghost patterns for irregular arrays

NASA Astrophysics Data System (ADS)

Wijnholds, S. J.; Grobler, T. L.; Smirnov, O. M.

2016-04-01

Calibration artefacts, like the self-calibration bias, usually emerge when data are calibrated using an incomplete sky model. In the first paper of this series, in which we analysed calibration artefacts in data from the Westerbork Synthesis Radio Telescope, we showed that these artefacts take the form of spurious positive and negative sources, which we refer to as ghosts or ghost sources. We also developed a mathematical framework with which we could predict the ghost pattern of an east-west interferometer for a simple two-source test case. In this paper, we extend our analysis to more general array layouts. This provides us with a useful method for the analysis of ghosts that we refer to as extrapolation. Combining extrapolation with a perturbation analysis, we are able to (1) analyse the ghost pattern for a two-source test case with one modelled and one unmodelled source for an arbitrary array layout, (2) explain why some ghosts are brighter than others, (3) define a taxonomy allowing us to classify the different ghosts, (4) derive closed form expressions for the fluxes and positions of the brightest ghosts, and (5) explain the strange two-peak structure with which some ghosts manifest during imaging. We illustrate our mathematical predictions using simulations of the KAT-7 (seven-dish Karoo Array Telescope) array. These results show the explanatory power of our mathematical model. The insights gained in this paper provide a solid foundation to study calibration artefacts in arbitrary, I.e. more complicated than the two-source example discussed here, incomplete sky models or full synthesis observations including direction-dependent effects.

Information Security Scheme Based on Computational Temporal Ghost Imaging.

PubMed

Jiang, Shan; Wang, Yurong; Long, Tao; Meng, Xiangfeng; Yang, Xiulun; Shu, Rong; Sun, Baoqing

2017-08-09

An information security scheme based on computational temporal ghost imaging is proposed. A sequence of independent 2D random binary patterns are used as encryption key to multiply with the 1D data stream. The cipher text is obtained by summing the weighted encryption key. The decryption process can be realized by correlation measurement between the encrypted information and the encryption key. Due to the instinct high-level randomness of the key, the security of this method is greatly guaranteed. The feasibility of this method and robustness against both occlusion and additional noise attacks are discussed with simulation, respectively.

Ghost imaging of phase objects with classical incoherent light

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

Shirai, Tomohiro; Setaelae, Tero; Friberg, Ari T.

2011-10-15

We describe an optical setup for performing spatial Fourier filtering in ghost imaging with classical incoherent light. This is achieved by a modification of the conventional geometry for lensless ghost imaging. It is shown on the basis of classical coherence theory that with this technique one can realize what we call phase-contrast ghost imaging to visualize pure phase objects.

High visibility temporal ghost imaging with classical light

NASA Astrophysics Data System (ADS)

Liu, Jianbin; Wang, Jingjing; Chen, Hui; Zheng, Huaibin; Liu, Yanyan; Zhou, Yu; Li, Fu-li; Xu, Zhuo

2018-03-01

High visibility temporal ghost imaging with classical light is possible when superbunching pseudothermal light is employed. In the numerical simulation, the visibility of temporal ghost imaging with pseudothermal light, equaling (4 . 7 ± 0 . 2)%, can be increased to (75 ± 8)% in the same scheme with superbunching pseudothermal light. The reasons for that the retrieved images are different for superbunching pseudothermal light with different values of degree of second-order coherence are discussed in detail. It is concluded that high visibility and high quality temporal ghost image can be obtained by collecting sufficient number of data points. The results are helpful to understand the difference between ghost imaging with classical light and entangled photon pairs. The superbunching pseudothermal light can be employed to improve the image quality in ghost imaging applications.

Artifact Suppression in Imaging of Myocardial Infarction Using B1-Weighted Phased-Array Combined Phase-Sensitive Inversion Recovery

PubMed Central

Kellman, Peter; Dyke, Christopher K.; Aletras, Anthony H.; McVeigh, Elliot R.; Arai, Andrew E.

2007-01-01

Regions of the body with long T1, such as cerebrospinal fluid (CSF), may create ghost artifacts on gadolinium-hyperenhanced images of myocardial infarction when inversion recovery (IR) sequences are used with a segmented acquisition. Oscillations in the transient approach to steady state for regions with long T1 may cause ghosts, with the number of ghosts being equal to the number of segments. B1-weighted phased-array combining provides an inherent degree of ghost artifact suppression because the ghost artifact is weighted less than the desired signal intensity by the coil sensitivity profiles. Example images are shown that illustrate the suppression of CSF ghost artifacts by the use of B1-weighted phased-array combining of multiple receiver coils. PMID:14755669

Examining Perceived Distance and Personal Authenticity as Mediators of the Effects of Ghost-Tweeting on Parasocial Interaction.

PubMed

Cohen, Elizabeth L; Tyler, William J

2016-05-01

A number of high-profile public figures hire ghost-tweeters to post to their social media accounts on their behalf, but no research has examined how this social media practice can affect followers' feelings of connection to the public figures. College students (n = 132) participated in an online experiment to examine the effect of ghost-tweeting practices on parasocial interaction (PSI) with social media figures. Tweet authorship (use of a ghost-tweeter or not) was manipulated. Ghost-tweeting resulted in reduced PSI. Perceptions of distance, but not personal authenticity mediated this effect. However, authenticity and distance did serially mediate the relationship between ghost-tweeting and PSI. These findings shed light on the process of PSI with celebrities and other media figures on social network sites.

Suppressing ghost beams: Backlink options for LISA

NASA Astrophysics Data System (ADS)

Isleif, K.-S.; Gerberding, O.; Penkert, D.; Fitzsimons, E.; Ward, H.; Robertson, D.; Livas, J.; Mueller, G.; Reiche, J.; Heinzel, G.; Danzmann, K.

2017-05-01

In this article we discuss possible design options for the optical phase reference system, the so called backlink, between two moving optical benches in a LISA satellite. The candidates are based on two approaches: Fiber backlinks, with additional features like mode cleaning cavities and Faraday isolators, and free beam backlinks with angle compensation techniques. We will indicate dedicated ghost beam mitigation strategies for the design options and we will point out critical aspects in case of an implementation in LISA.

Ostrogradsky in theories with multiple fields

NASA Astrophysics Data System (ADS)

de Rham, Claudia; Matas, Andrew

2016-06-01

We review how the (absence of) Ostrogradsky instability manifests itself in theories with multiple fields. It has recently been appreciated that when multiple fields are present, the existence of higher derivatives may not automatically imply the existence of ghosts. We discuss the connection with gravitational theories like massive gravity and beyond Horndeski which manifest higher derivatives in some formulations and yet are free of Ostrogradsky ghost. We also examine an interesting new class of Extended Scalar-Tensor Theories of gravity which has been recently proposed. We show that for a subclass of these theories, the tensor modes are either not dynamical or are infinitely strongly coupled. Among the remaining theories for which the tensor modes are well-defined one counts one new model that is not field-redefinable to Horndeski via a conformal and disformal transformation but that does require the vacuum to break Lorentz invariance. We discuss the implications for the effective field theory of dark energy and the stability of the theory. In particular we find that if we restrict ourselves to the Extended Scalar-Tensor class of theories for which the tensors are well-behaved and the scalar is free from gradient or ghost instabilities on FLRW then we recover Horndeski up to field redefinitions.

An improved non-uniformity correction algorithm and its hardware implementation on FPGA

NASA Astrophysics Data System (ADS)

Rong, Shenghui; Zhou, Huixin; Wen, Zhigang; Qin, Hanlin; Qian, Kun; Cheng, Kuanhong

2017-09-01

The Non-uniformity of Infrared Focal Plane Arrays (IRFPA) severely degrades the infrared image quality. An effective non-uniformity correction (NUC) algorithm is necessary for an IRFPA imaging and application system. However traditional scene-based NUC algorithm suffers the image blurring and artificial ghosting. In addition, few effective hardware platforms have been proposed to implement corresponding NUC algorithms. Thus, this paper proposed an improved neural-network based NUC algorithm by the guided image filter and the projection-based motion detection algorithm. First, the guided image filter is utilized to achieve the accurate desired image to decrease the artificial ghosting. Then a projection-based moving detection algorithm is utilized to determine whether the correction coefficients should be updated or not. In this way the problem of image blurring can be overcome. At last, an FPGA-based hardware design is introduced to realize the proposed NUC algorithm. A real and a simulated infrared image sequences are utilized to verify the performance of the proposed algorithm. Experimental results indicated that the proposed NUC algorithm can effectively eliminate the fix pattern noise with less image blurring and artificial ghosting. The proposed hardware design takes less logic elements in FPGA and spends less clock cycles to process one frame of image.

Oscillatory attractors: a new cosmological phase

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

Bains, Jasdeep S.; Hertzberg, Mark P.; Wilczek, Frank, E-mail: bains@physics.harvard.edu, E-mail: mark.hertzberg@tufts.edu, E-mail: wilczek@mit.edu

2017-05-01

In expanding FRW spacetimes, it is usually the case that homogeneous scalar fields redshift and their amplitudes approach limiting values: Hubble friction usually ensures that the field relaxes to its minimum energy configuration, which is usually a static configuration. Here we discover a class of relativistic scalar field models in which the attractor behavior is the field oscillating indefinitely, with finite amplitude, in an expanding FRW spacetime, despite the presence of Hubble friction. This is an example of spontaneous breaking of time translation symmetry. We find that the effective equation of state of the field has average value ( wmore » )=−1, implying that the field itself could drive an inflationary or dark energy dominated phase. This behavior is reminiscent of ghost condensate models, but in the new models, unlike in the ghost condensate models, the energy-momentum tensor is time dependent, so that these new models embody a more definitive breaking of time translation symmetry. We explore (quantum) fluctuations around the homogeneous background solution, and find that low k -modes can be stable, while high k -modes are typically unstable. We discuss possible interpretations and implications of that instability.« less

An improved algorithm to reduce noise in high-order thermal ghost imaging.

PubMed

Chen, Xi-Hao; Wu, Shuang-Shuang; Wu, Wei; Guo, Wang-Yuan; Meng, Shao-Ying; Sun, Zhi-Bin; Zhai, Guang-Jie; Li, Ming-Fei; Wu, Ling-An

2014-09-01

A modified Nth-order correlation function is derived that can effectively remove the noise background encountered in high-order thermal light ghost imaging (GI). Based on this, the quality of the reconstructed images in an Nth-order lensless GI setup has been greatly enhanced compared to former high-order schemes for the same sampling number. In addition, the dependence of the visibility and signal-to-noise ratio for different high-order images on the sampling number has been measured and compared.

Growing Up with Ghosts

ERIC Educational Resources Information Center

Shafer, Susan

1976-01-01

A study of 34 third grade working class children of various ethnic backgrounds attempted to discover children's conceptions of ghosts. Children were exposed to information about ghosts and asked many "simple" and "wild" questions to elicit their conceptions. (MS)

Ghost circles in lattice Aubry-Mather theory

NASA Astrophysics Data System (ADS)

Mramor, Blaz; Rink, Bob

Monotone lattice recurrence relations such as the Frenkel-Kontorova lattice, arise in Hamiltonian lattice mechanics, as models for ferromagnetism and as discretization of elliptic PDEs. Mathematically, they are a multi-dimensional counterpart of monotone twist maps. Such recurrence relations often admit a variational structure, so that the solutions x:Z→R are the stationary points of a formal action function W(x). Given any rotation vector ω∈R, classical Aubry-Mather theory establishes the existence of a large collection of solutions of ∇W(x)=0 of rotation vector ω. For irrational ω, this is the well-known Aubry-Mather set. It consists of global minimizers and it may have gaps. In this paper, we study the parabolic gradient flow {dx}/{dt}=-∇W(x) and we will prove that every Aubry-Mather set can be interpolated by a continuous gradient-flow invariant family, the so-called 'ghost circle'. The existence of these ghost circles is known in dimension d=1, for rational rotation vectors and Morse action functions. The main technical result of this paper is therefore a compactness theorem for lattice ghost circles, based on a parabolic Harnack inequality for the gradient flow. This implies the existence of lattice ghost circles of arbitrary rotation vectors and for arbitrary actions. As a consequence, we can give a simple proof of the fact that when an Aubry-Mather set has a gap, then this gap must be filled with minimizers, or contain a non-minimizing solution.

The cosmology of interacting spin-2 fields

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

Tamanini, Nicola; Saridakis, Emmanuel N.; Koivisto, Tomi S., E-mail: n.tamanini.11@ucl.ac.uk, E-mail: Emmanuel_Saridakis@baylor.edu, E-mail: t.s.koivisto@astro.uio.no

2014-02-01

We investigate the cosmology of interacting spin-2 particles, formulating the multi-gravitational theory in terms of vierbeins and without imposing any Deser-van Nieuwen-huizen-like constraint. The resulting multi-vierbein theory represents a wider class of gravitational theories if compared to the corresponding multi-metric models. Moreover, as opposed to its metric counterpart which in general seems to contain ghosts, it has already been proved to be ghost-free. We outline a discussion about the possible matter couplings and we focus on the study of cosmological scenarios in the case of three and four interacting vierbeins. We find rich behavior, including de Sitter solutions with anmore » effective cosmological constant arising from the multi-vierbein interaction, dark-energy solutions and nonsingular bouncing behavior.« less

Modified QCD ghost f(T,TG) gravity

NASA Astrophysics Data System (ADS)

Jawad, Abdul; Rani, Shamaila; Chattopadhyay, Surajit

2015-12-01

In this paper, we explore the reconstruction scenario of modified QCD ghost dark energy model and newly proposed f(T,TG) gravity in flat FRW universe. We consider the well-known assumption of scale factor, i.e., power law form. We construct the f(T,TG) model and discuss its cosmological consequences through various cosmological parameters such as equation of state parameter, squared speed of sound and ω_{DE}-ω '_{DE}. The equation of state parameter provides the quintom-like behavior of the universe. The squared speed of sound exhibits the stability of model in the later time. Also, ω_{DE}- ω '_{DE} corresponds to freezing as well as thawing regions. It is also interesting to remark here that the results of equation of state parameter and w_{DE}-w'_{DE} coincide with the observational data.

Stability, ghost, and strong coupling in nonrelativistic general covariant theory of gravity with {lambda}{ne}1

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

Huang Yongqing; Wang Anzhong

2011-05-15

In this paper, we investigate three important issues: stability, ghost, and strong coupling, in the Horava-Melby-Thompson setup of the Horava-Lifshitz theory with {lambda}{ne}1, generalized recently by da Silva. We first develop the general linear scalar perturbations of the Friedmann-Robertson-Walker (FRW) universe with arbitrary spatial curvature and find that an immediate by-product of the setup is that, in all the inflationary models described by a scalar field, the FRW universe is necessarily flat. Applying them to the case of the Minkowski background, we find that it is stable, and, similar to the case {lambda}=1, the spin-0 graviton is eliminated. The vectormore » perturbations vanish identically in the Minkowski background. Thus, similar to general relativity, a free gravitational field in this setup is completely described by a spin-2 massless graviton, even with {lambda}{ne}1. We also study the ghost problem in the FRW background and find explicitly the ghost-free conditions. To study the strong coupling problem, we consider two different kinds of spacetimes, all with the presence of matter: one is cosmological, and the other is static. We find that the coupling becomes strong for a process with energy higher than M{sub pl}|c{sub {psi}|}{sup 5/2} in the flat FRW background and M{sub pl}|c{sub {psi}|}{sup 3} in a static weak gravitational field, where |c{sub {psi}|{identical_to}}|(1-{lambda})/(3{lambda}-1)|{sup 1/2}.« less

Quantum ghost imaging through turbulence

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

Dixon, P. Ben; Howland, Gregory A.; Howell, John C.

2011-05-15

We investigate the effect of turbulence on quantum ghost imaging. We use entangled photons and demonstrate that for a specific experimental configuration the effect of turbulence can be greatly diminished. By decoupling the entangled photon source from the ghost-imaging central image plane, we are able to dramatically increase the ghost-image quality. When imaging a test pattern through turbulence, this method increases the imaged pattern visibility from V=0.15{+-}0.04 to 0.42{+-}0.04.

Low-momentum ghost dressing function and the gluon mass

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

Boucaud, Ph.; Leroy, J. P.; Le Yaouanc, A.

2010-09-01

We study the low-momentum ghost propagator Dyson-Schwinger equation in the Landau gauge, assuming for the truncation a constant ghost-gluon vertex, as it is extensively done, and a simple model for a massive gluon propagator. Then, regular Dyson-Schwinger equation solutions (the zero-momentum ghost dressing function not diverging) appear to emerge, and we show the ghost propagator to be described by an asymptotic expression reliable up to the order O(q{sup 2}). That expression, depending on the gluon mass and the zero-momentum Taylor-scheme effective charge, is proven to fit pretty well some low-momentum ghost propagator data [I. L. Bogolubsky, E. M. Ilgenfritz, M.more » Muller-Preussker, and A. Sternbeck, Phys. Lett. B 676, 69 (2009); Proc. Sci., LAT2007 (2007) 290] from big-volume lattice simulations where the so-called ''simulated annealing algorithm'' is applied to fix the Landau gauge.« less

Are the dressed gluon and ghost propagators in the Landau gauge presently determined in the confinement regime of QCD?

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

Pennington, M. R.; Wilson, D. J.

2011-11-01

The gluon and ghost propagators in Landau gauge QCD are investigated using the Schwinger-Dyson equation approach. Working in Euclidean spacetime, we solve for these propagators using a selection of vertex inputs, initially for the ghost equation alone and then for both propagators simultaneously. The results are shown to be highly sensitive to the choices of vertices. We favor the infrared finite ghost solution from studying the ghost equation alone where we argue for a specific unique solution. In order to solve this simultaneously with the gluon using a dressed-one-loop truncation, we find that a nontrivial full ghost-gluon vertex is requiredmore » in the vanishing gluon momentum limit. The self-consistent solutions we obtain correspond to having a masslike term in the gluon propagator dressing, in agreement with similar studies supporting the long-held proposal of Cornwall.« less

Secret shared multiple-image encryption based on row scanning compressive ghost imaging and phase retrieval in the Fresnel domain

NASA Astrophysics Data System (ADS)

Li, Xianye; Meng, Xiangfeng; Wang, Yurong; Yang, Xiulun; Yin, Yongkai; Peng, Xiang; He, Wenqi; Dong, Guoyan; Chen, Hongyi

2017-09-01

A multiple-image encryption method is proposed that is based on row scanning compressive ghost imaging, (t, n) threshold secret sharing, and phase retrieval in the Fresnel domain. In the encryption process, after wavelet transform and Arnold transform of the target image, the ciphertext matrix can be first detected using a bucket detector. Based on a (t, n) threshold secret sharing algorithm, the measurement key used in the row scanning compressive ghost imaging can be decomposed and shared into two pairs of sub-keys, which are then reconstructed using two phase-only mask (POM) keys with fixed pixel values, placed in the input plane and transform plane 2 of the phase retrieval scheme, respectively; and the other POM key in the transform plane 1 can be generated and updated by the iterative encoding of each plaintext image. In each iteration, the target image acts as the input amplitude constraint in the input plane. During decryption, each plaintext image possessing all the correct keys can be successfully decrypted by measurement key regeneration, compression algorithm reconstruction, inverse wavelet transformation, and Fresnel transformation. Theoretical analysis and numerical simulations both verify the feasibility of the proposed method.

Ghosts: Gateway to Organizational Transformation.

ERIC Educational Resources Information Center

Weitzel, Tim; Had, Gary

2001-01-01

"Ghosts" are elements that influence an organization's view of itself, its ways of working, and its culturally specific attitudes; they exert an indirect influence over everything that happens within an organization. Successful organizational change requires identifying and integrating these ghosts. (JOW)

Ghost imaging via optical parametric amplification

NASA Astrophysics Data System (ADS)

Li, Hong-Guo; Zhang, De-Jian; Xu, De-Qin; Zhao, Qiu-Li; Wang, Sen; Wang, Hai-Bo; Xiong, Jun; Wang, Kaige

2015-10-01

We investigate theoretically and experimentally thermal light ghost imaging where the light transmitted through the object as the seed light is amplified by an optical parametric amplifier (OPA). In conventional lens imaging systems with OPA, the spectral bandwidth of OPA dominates the image resolution. Theoretically, we prove that in ghost imaging via optical parametric amplification (GIOPA) the bandwidth of OPA will not affect the image resolution. The experimental results show that for weak seed light the image quality in GIOPA is better than that of conventional ghost imaging. Our work may be valuable in remote sensing with ghost imaging technique, where the light passed through the object is weak after a long-distance propagation.

The enhanced immune responses induced by Salmonella enteritidis ghosts loaded with Neisseria gonorrhoeae porB against Salmonella in mice.

PubMed

Jiao, Hongmei; Yang, Hui; Zhao, Dan; He, Li; Chen, Jin; Li, Guocai

2016-11-01

Human health has been seriously endangered by highly prevalent salmonellosis and multidrug-resistant Salmonella strains. Current vaccines suffer from variable immune-protective effects, so more effective ones are needed to control Salmonella infection : Bacterial ghosts have been produced by the expression of lysis gene E from bacteriophage PhiX174 and can be filled with considerable exogenous substances such as DNA or drugs as a novel platform. In this study, Salmonella enteritidis (SE) ghosts were developed and loaded with Neisseria gonorrhoeae porin B (porB) to construct a novel inactive vaccine. Our new studies show that SE ghosts loaded with porB displayed increased production of pro-inflammatory cytokines (IL-1β, IL-6, IL-10 and IL-12p70) in bone marrow-derived dendritic cells (BMDCs), and elicited significantly higher specific systemic and mucosal immune responses to Salmonella than SE ghosts alone. In addition, the novel porB-loaded ghosts conferred higher protective effects on virulent Salmonella challenge. For the first time, we demonstrate that N. gonorrhoeae porB, as a novel adjuvant, can increase the immunogenicity of SE ghosts. Our studies suggested that Salmonella enteritidis ghosts loaded with Neisseria gonorrhoeae porin B might be a useful mucosal Salmonella vaccine candidate for practical use in the future. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

A pseudospectra-based approach to non-normal stability of embedded boundary methods

NASA Astrophysics Data System (ADS)

Rapaka, Narsimha; Samtaney, Ravi

2017-11-01

We present non-normal linear stability of embedded boundary (EB) methods employing pseudospectra and resolvent norms. Stability of the discrete linear wave equation is characterized in terms of the normalized distance of the EB to the nearest ghost node (α) in one and two dimensions. An important objective is that the CFL condition based on the Cartesian grid spacing remains unaffected by the EB. We consider various discretization methods including both central and upwind-biased schemes. Stability is guaranteed when α <=αmax ranges between 0.5 and 0.77 depending on the discretization scheme. Also, the stability characteristics remain the same in both one and two dimensions. Sharper limits on the sufficient conditions for stability are obtained based on the pseudospectral radius (the Kreiss constant) than the restrictive limits based on the usual singular value decomposition analysis. We present a simple and robust reclassification scheme for the ghost cells (``hybrid ghost cells'') to ensure Lax stability of the discrete systems. This has been tested successfully for both low and high order discretization schemes with transient growth of at most O (1). Moreover, we present a stable, fourth order EB reconstruction scheme. Supported by the KAUST Office of Competitive Research Funds under Award No. URF/1/1394-01.

Ghost artifact cancellation using phased array processing.

PubMed

Kellman, P; McVeigh, E R

2001-08-01

In this article, a method for phased array combining is formulated which may be used to cancel ghosts caused by a variety of distortion mechanisms, including space variant distortions such as local flow or off-resonance. This method is based on a constrained optimization, which optimizes SNR subject to the constraint of nulling ghost artifacts at known locations. The resultant technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation it is applied to full field-of-view (FOV) images. The method is applied to multishot EPI with noninterleaved phase encode acquisition. A number of benefits, as compared to the conventional interleaved approach, are reduced distortion due to off-resonance, in-plane flow, and EPI delay misalignment, as well as eliminating the need for echo-shifting. Experimental results demonstrate the cancellation for both phantom as well as cardiac imaging examples.

Ghost Artifact Cancellation Using Phased Array Processing

PubMed Central

Kellman, Peter; McVeigh, Elliot R.

2007-01-01

In this article, a method for phased array combining is formulated which may be used to cancel ghosts caused by a variety of distortion mechanisms, including space variant distortions such as local flow or off-resonance. This method is based on a constrained optimization, which optimizes SNR subject to the constraint of nulling ghost artifacts at known locations. The resultant technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation it is applied to full field-of-view (FOV) images. The method is applied to multishot EPI with noninterleaved phase encode acquisition. A number of benefits, as compared to the conventional interleaved approach, are reduced distortion due to off-resonance, in-plane flow, and EPI delay misalignment, as well as eliminating the need for echo-shifting. Experimental results demonstrate the cancellation for both phantom as well as cardiac imaging examples. PMID:11477638

Long-distance thermal temporal ghost imaging over optical fibers

NASA Astrophysics Data System (ADS)

Yao, Xin; Zhang, Wei; Li, Hao; You, Lixing; Wang, Zhen; Huang, Yidong

2018-02-01

A thermal ghost imaging scheme between two distant parties is proposed and experimentally demonstrated over long-distance optical fibers. In the scheme, the weak thermal light is split into two paths. Photons in one path are spatially diffused according to their frequencies by a spatial dispersion component, then illuminate the object and record its spatial transmission information. Photons in the other path are temporally diffused by a temporal dispersion component. By the coincidence measurement between photons of two paths, the object can be imaged in a way of ghost imaging, based on the frequency correlation between photons in the two paths. In the experiment, the weak thermal light source is prepared by the spontaneous four-wave mixing in a silicon waveguide. The temporal dispersion is introduced by single mode fibers of 50 km, which also could be looked as a fiber link. Experimental results show that this scheme can be realized over long-distance optical fibers.

Multishot cartesian turbo spin-echo diffusion imaging using iterative POCSMUSE Reconstruction.

PubMed

Zhang, Zhe; Zhang, Bing; Li, Ming; Liang, Xue; Chen, Xiaodong; Liu, Renyuan; Zhang, Xin; Guo, Hua

2017-07-01

To report a diffusion imaging technique insensitive to off-resonance artifacts and motion-induced ghost artifacts using multishot Cartesian turbo spin-echo (TSE) acquisition and iterative POCS-based reconstruction of multiplexed sensitivity encoded magnetic resonance imaging (MRI) (POCSMUSE) for phase correction. Phase insensitive diffusion preparation was used to deal with the violation of the Carr-Purcell-Meiboom-Gill (CPMG) conditions of TSE diffusion-weighted imaging (DWI), followed by a multishot Cartesian TSE readout for data acquisition. An iterative diffusion phase correction method, iterative POCSMUSE, was developed and implemented to eliminate the ghost artifacts in multishot TSE DWI. The in vivo human brain diffusion images (from one healthy volunteer and 10 patients) using multishot Cartesian TSE were acquired at 3T and reconstructed using iterative POCSMUSE, and compared with single-shot and multishot echo-planar imaging (EPI) results. These images were evaluated by two radiologists using visual scores (considering both image quality and distortion levels) from 1 to 5. The proposed iterative POCSMUSE reconstruction was able to correct the ghost artifacts in multishot DWI. The ghost-to-signal ratio of TSE DWI using iterative POCSMUSE (0.0174 ± 0.0024) was significantly (P < 0.0005) smaller than using POCSMUSE (0.0253 ± 0.0040). The image scores of multishot TSE DWI were significantly higher than single-shot (P = 0.004 and 0.006 from two reviewers) and multishot (P = 0.008 and 0.004 from two reviewers) EPI-based methods. The proposed multishot Cartesian TSE DWI using iterative POCSMUSE reconstruction can provide high-quality diffusion images insensitive to motion-induced ghost artifacts and off-resonance related artifacts such as chemical shifts and susceptibility-induced image distortions. 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:167-174. © 2016 International Society for Magnetic Resonance in Medicine.

Ghost Authorship in Industry-Initiated Randomised Trials

PubMed Central

Gøtzsche, Peter C; Hróbjartsson, Asbjørn; Johansen, Helle Krogh; Haahr, Mette T; Altman, Douglas G; Chan, An-Wen

2007-01-01

Background Ghost authorship, the failure to name, as an author, an individual who has made substantial contributions to an article, may result in lack of accountability. The prevalence and nature of ghost authorship in industry-initiated randomised trials is not known. Methods and Findings We conducted a cohort study comparing protocols and corresponding publications for industry-initiated trials approved by the Scientific-Ethical Committees for Copenhagen and Frederiksberg in 1994–1995. We defined ghost authorship as present if individuals who wrote the trial protocol, performed the statistical analyses, or wrote the manuscript, were not listed as authors of the publication, or as members of a study group or writing committee, or in an acknowledgment. We identified 44 industry-initiated trials. We did not find any trial protocol or publication that stated explicitly that the clinical study report or the manuscript was to be written or was written by the clinical investigators, and none of the protocols stated that clinical investigators were to be involved with data analysis. We found evidence of ghost authorship for 33 trials (75%; 95% confidence interval 60%–87%). The prevalence of ghost authorship was increased to 91% (40 of 44 articles; 95% confidence interval 78%–98%) when we included cases where a person qualifying for authorship was acknowledged rather than appearing as an author. In 31 trials, the ghost authors we identified were statisticians. It is likely that we have overlooked some ghost authors, as we had very limited information to identify the possible omission of other individuals who would have qualified as authors. Conclusions Ghost authorship in industry-initiated trials is very common. Its prevalence could be considerably reduced, and transparency improved, if existing guidelines were followed, and if protocols were publicly available. PMID:17227134

Ghost authorship in industry-initiated randomised trials.

PubMed

Gøtzsche, Peter C; Hróbjartsson, Asbjørn; Johansen, Helle Krogh; Haahr, Mette T; Altman, Douglas G; Chan, An-Wen

2007-01-01

Ghost authorship, the failure to name, as an author, an individual who has made substantial contributions to an article, may result in lack of accountability. The prevalence and nature of ghost authorship in industry-initiated randomised trials is not known. We conducted a cohort study comparing protocols and corresponding publications for industry-initiated trials approved by the Scientific-Ethical Committees for Copenhagen and Frederiksberg in 1994-1995. We defined ghost authorship as present if individuals who wrote the trial protocol, performed the statistical analyses, or wrote the manuscript, were not listed as authors of the publication, or as members of a study group or writing committee, or in an acknowledgment. We identified 44 industry-initiated trials. We did not find any trial protocol or publication that stated explicitly that the clinical study report or the manuscript was to be written or was written by the clinical investigators, and none of the protocols stated that clinical investigators were to be involved with data analysis. We found evidence of ghost authorship for 33 trials (75%; 95% confidence interval 60%-87%). The prevalence of ghost authorship was increased to 91% (40 of 44 articles; 95% confidence interval 78%-98%) when we included cases where a person qualifying for authorship was acknowledged rather than appearing as an author. In 31 trials, the ghost authors we identified were statisticians. It is likely that we have overlooked some ghost authors, as we had very limited information to identify the possible omission of other individuals who would have qualified as authors. Ghost authorship in industry-initiated trials is very common. Its prevalence could be considerably reduced, and transparency improved, if existing guidelines were followed, and if protocols were publicly available.

Construction of a Salmonella Gallinarum ghost as a novel inactivated vaccine candidate and its protective efficacy against fowl typhoid in chickens

PubMed Central

2012-01-01

In order to develop a novel, safe and immunogenic fowl typhoid (FT) vaccine candidate, a Salmonella Gallinarum ghost with controlled expression of the bacteriophage PhiX174 lysis gene E was constructed using pMMP99 plasmid in this study. The formation of the Salmonella Gallinarum ghost with tunnel formation and loss of cytoplasmic contents was observed by scanning electron microscopy and transmission electron microscopy. No viable cells were detectable 24 h after the induction of gene E expression by an increase in temperature from 37 °C to 42 °C. The safety and protective efficacy of the Salmonella Gallinarum ghost vaccine was tested in chickens that were divided into four groups: group A (non-immunized control), group B (orally immunized), group C (subcutaneously immunized) and group D (intramuscularly immunized). The birds were immunized at day 7 of age. None of the immunized animals showed any adverse reactions such as abnormal behavior, mortality, or signs of FT such as anorexia, depression, or diarrhea. These birds were subsequently challenged with a virulent Salmonella Gallinarum strain at 3 weeks post-immunization (wpi). Significant protection against the virulent challenge was observed in all immunized groups based on mortality and post-mortem lesions compared to the non-immunized control group. In addition, immunization with the Salmonella Gallinarum ghosts induced significantly high systemic IgG response in all immunized groups. Among the groups, orally-vaccinated group B showed significantly higher levels of secreted IgA. A potent antigen-specific lymphocyte activation response along with significantly increased percentages of CD4+ and CD8+ T lymphocytes found in all immunized groups clearly indicate the induction of cellular immune responses. Overall, these findings suggest that the newly constructed Salmonella Gallinarum ghost appears to be a safe, highly immunogenic, and efficient non-living bacterial vaccine candidate that protects against FT. PMID:22620989

Holy Gargoyles! Art Curriculum That Works

ERIC Educational Resources Information Center

Healy, John W.

2005-01-01

The subject of gargoyles is engaging for children. Creating their own gargoyles is a journey to a place of fantasy and imagination. Ghosts, goblins, creatures of the night--this is the stuff for which students have a limitless reserve of energy. What more appropriate time than Halloween to share with them the history of these functional--and…

Single-shot thermal ghost imaging using wavelength-division multiplexing

NASA Astrophysics Data System (ADS)

Deng, Chao; Suo, Jinli; Wang, Yuwang; Zhang, Zhili; Dai, Qionghai

2018-01-01

Ghost imaging (GI) is an emerging technique that reconstructs the target scene from its correlated measurements with a sequence of patterns. Restricted by the multi-shot principle, GI usually requires long acquisition time and is limited in observation of dynamic scenes. To handle this problem, this paper proposes a single-shot thermal ghost imaging scheme via a wavelength-division multiplexing technique. Specifically, we generate thousands of correlated patterns simultaneously by modulating a broadband light source with a wavelength dependent diffuser. These patterns carry the scene's spatial information and then the correlated photons are coupled into a spectrometer for the final reconstruction. This technique increases the speed of ghost imaging and promotes the applications in dynamic ghost imaging with high scalability and compatibility.

Ghost of Mirach Rears its Spooky Head

NASA Image and Video Library

2008-10-31

The Ghost of Mirach galaxy is shown in visible light on the left, and in ultraviolet as seen by NASA Galaxy Evolution Explorer on the right. The fields of view are identical in both pictures, with the Ghost of Mirach -— a galaxy called NGC 404.

American Stories of Cultural Haunting: Tales of Heirs and Ethnographers.

ERIC Educational Resources Information Center

Brogan, Kathleen

1995-01-01

Discusses the ghosts and haunting in recent American fiction. Considers the similarity of function of ghosts in contemporary ethnic American literatures. Identifies a specific kind of ghost story, a "cultural haunting," that has recently emerged in large numbers in ethnic American literature. (HB)

Hydraulic activities by ghost shrimp Neotrypaea californiensis induce oxic-anoxic oscillations in sediments

EPA Science Inventory

We applied porewater pressure sensing, time-lapse photography and planar optode imaging of oxygen to investigate hydraulic behaviors of the Thalassinidean ghost shrimp Neotrypaea californiensis and the associated dynamics of oxygen in and around their burrows. Ghost shrimp were h...

Evidence of marine debris usage by the ghost crab Ocypode quadrata (Fabricius, 1787).

PubMed

Costa, Leonardo Lopes; Rangel, Danilo Freitas; Zalmon, Ilana Rosental

2018-03-01

Sandy beaches are sites of marine debris stranding, but the interaction of beach biota with waste is poorly studied. The objective of this study was to investigate whether the ghost crab Ocypode quadrata selects marine debris by types using a non-destructive method on sandy beaches of Southeastern Brazil. We found marine debris in 7% of 1696 surveyed burrows, and the ghost crabs selectivity was mainly by soft plastic (30%), straw (11%), rope (6%) and foam (4%). Burrows with marine debris showed higher occupation rate (~68%) compared to burrows without debris (~28%), indicating that these materials may increase the capacity of ghost crabs to memorize their burrows placement (homing). The percentage of marine debris was not always related to their amount in the drift line, but ghost crabs used more debris near urbanized areas. Future studies should test whether ghost crabs are using marine debris for feeding, homing or other mechanisms. Copyright © 2018 Elsevier Ltd. All rights reserved.

GHOST balloons around Antarctica

NASA Technical Reports Server (NTRS)

Stearns, Charles R.

1988-01-01

The GHOST balloon position as a function of time data shows that the atmospheric circulation around the Antarctic Continent at the 100 mb and 200 mb levels is complex. The GHOST balloons supposedly follow the horizontal trajectory of the air at the balloon level. The position of GHOST balloon 98Q for a three month period in 1968 is shown. The balloon moved to within 2 deg of the South Pole on 1 October 1968 and then by 9 December 1968 was 35 deg from the South Pole and close to its position on 1 September 1968. The balloon generally moved from west to east but on two occasions moved in the opposite direction for a few days. The latitude of GHOST balloons 98Q and 149Z which was at 200 mb is given. Both balloons tended to get closer to the South Pole in September and October. Other GHOST balloons at the same pressure and time period may not indicate similar behavior.

The Investigation of Ghost Fluid Method for Simulating the Compressible Two-Medium Flow

NASA Astrophysics Data System (ADS)

Lu, Hai Tian; Zhao, Ning; Wang, Donghong

2016-06-01

In this paper, we investigate the conservation error of the two-dimensional compressible two-medium flow simulated by the front tracking method. As the improved versions of the original ghost fluid method, the modified ghost fluid method and the real ghost fluid method are selected to define the interface boundary conditions, respectively, to show different effects on the conservation error. A Riemann problem is constructed along the normal direction of the interface in the front tracking method, with the goal of obtaining an efficient procedure to track the explicit sharp interface precisely. The corresponding Riemann solutions are also used directly in these improved ghost fluid methods. Extensive numerical examples including the sod tube and the shock-bubble interaction are tested to calculate the conservation error. It is found that these two ghost fluid methods have distinctive performances for different initial conditions of the flow field, and the related conclusions are made to suggest the best choice for the combination.

Nonparametric Determination of Redshift Evolution Index of Dark Energy

NASA Astrophysics Data System (ADS)

Ziaeepour, Houri

We propose a nonparametric method to determine the sign of γ — the redshift evolution index of dark energy. This is important for distinguishing between positive energy models, a cosmological constant, and what is generally called ghost models. Our method is based on geometrical properties and is more tolerant to uncertainties of other cosmological parameters than fitting methods in what concerns the sign of γ. The same parametrization can also be used for determining γ and its redshift dependence by fitting. We apply this method to SNLS supernovae and to gold sample of re-analyzed supernovae data from Riess et al. Both datasets show strong indication of a negative γ. If this result is confirmed by more extended and precise data, many of the dark energy models, including simple cosmological constant, standard quintessence models without interaction between quintessence scalar field(s) and matter, and scaling models are ruled out. We have also applied this method to Gurzadyan-Xue models with varying fundamental constants to demonstrate the possibility of using it to test other cosmologies.

Do massive compact objects without event horizon exist in infinite derivative gravity?

NASA Astrophysics Data System (ADS)

Koshelev, Alexey S.; Mazumdar, Anupam

2017-10-01

Einstein's general theory of relativity is plagued by cosmological and black-hole type singularities Recently, it has been shown that infinite derivative, ghost free, gravity can yield nonsingular cosmological and mini-black hole solutions. In particular, the theory possesses a mass-gap determined by the scale of new physics. This paper provides a plausible argument, not a no-go theorem, based on the Area-law of gravitational entropy that within infinite derivative, ghost free, gravity nonsingular compact objects in the static limit need not have horizons.

Method and apparatus for distinguishing actual sparse events from sparse event false alarms

DOEpatents

Spalding, Richard E.; Grotbeck, Carter L.

2000-01-01

Remote sensing method and apparatus wherein sparse optical events are distinguished from false events. "Ghost" images of actual optical phenomena are generated using an optical beam splitter and optics configured to direct split beams to a single sensor or segmented sensor. True optical signals are distinguished from false signals or noise based on whether the ghost image is presence or absent. The invention obviates the need for dual sensor systems to effect a false target detection capability, thus significantly reducing system complexity and cost.

Ghost Children: Invisible Middle Level Students

ERIC Educational Resources Information Center

Matteson, Shirley M.

2014-01-01

For this study, 119 middle level teacher candidates identified, observed, and documented their interactions with middle school "ghost children" as part of their field placement activities. About two thirds of the 124 ghost children identified for this study were male. The teacher candidates documented additional characteristics of ghost…

Hunting The Ghost Gun: An Analysis Of The U.S. Army Infantry Rifle

DTIC Science & Technology

2016-03-01

NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA JOINT APPLIED PROJECT HUNTING THE GHOST GUN : AN ANALYSIS OF THE U.S. ARMY......LEFT BLANK iii Approved for public release; distribution is unlimited HUNTING THE GHOST GUN : AN ANALYSIS OF THE U.S. ARMY INFANTRY

Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air Injection Testing and Tracer Testing in the Northern Ghost Dance Fault, YUCCA Mountain, Nevada, November 1996 to August 1998

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

Lecain, G.D.; Anna, L.O.; Fahy, M.F.

1998-08-01

Geothermal logging, air and core-water chemistry sampling, air-injection testing, and tracer testing were done in the northern Ghost Dance Fault at Yucca Mountain, Nevada, from November 1996 to August 1998. The study was done by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy. The fault-testing drill room and test boreholes were located in the crystal-poor, middle nonlithophysal zone of the Topopah Spring Tuff, a tuff deposit of Miocene age. The drill room is located off the Yucca Mountain underground Exploratory Studies Facility at about 230 meters below ground surface. Borehole geothermal logging identified a temperature decreasemore » of 0.1 degree Celsius near the Ghost Dance Fault. The temperature decrease could indicate movement of cooler air or water, or both, down the fault, or it may be due to drilling-induced evaporative or adiabatic cooling. In-situ pneumatic pressure monitoring indicated that barometric pressure changes were transmitted from the ground surface to depth through the Ghost Dance Fault. Values of carbon dioxide and delta carbon-13 from gas samples indicated that air from the underground drill room had penetrated the tuff, supporting the concept of a well-developed fracture system. Uncorrected carbon-14-age estimates from gas samples ranged from 2,400 to 4,500 years. Tritium levels in borehole core water indicated that the fault may have been a conduit for the transport of water from the ground surface to depth during the last 100 years.« less

Ostrogradsky in theories with multiple fields

DOE PAGES

de Rham, Claudia; Matas, Andrew

2016-06-23

We review how the (absence of) Ostrogradsky instability manifests itself in theories with multiple fields. It has recently been appreciated that when multiple fields are present, the existence of higher derivatives may not automatically imply the existence of ghosts. We discuss the connection with gravitational theories like massive gravity and beyond Horndeski which manifest higher derivatives in some formulations and yet are free of Ostrogradsky ghost. We also examine an interesting new class of Extended Scalar-Tensor Theories of gravity which has been recently proposed. We show that for a subclass of these theories, the tensor modes are either not dynamicalmore » or are infinitely strongly coupled. Among the remaining theories for which the tensor modes are well-defined one counts one new model that is not field-redefinable to Horndeski via a conformal and disformal transformation but that does require the vacuum to break Lorentz invariance. We discuss the implications for the effective field theory of dark energy and the stability of the theory. In particular we find that if we restrict ourselves to the Extended Scalar-Tensor class of theories for which the tensors are well-behaved and the scalar is free from gradient or ghost instabilities on FLRW then we recover Horndeski up to field redefinitions.« less

Ostrogradsky in theories with multiple fields

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

de Rham, Claudia; Matas, Andrew

We review how the (absence of) Ostrogradsky instability manifests itself in theories with multiple fields. It has recently been appreciated that when multiple fields are present, the existence of higher derivatives may not automatically imply the existence of ghosts. We discuss the connection with gravitational theories like massive gravity and beyond Horndeski which manifest higher derivatives in some formulations and yet are free of Ostrogradsky ghost. We also examine an interesting new class of Extended Scalar-Tensor Theories of gravity which has been recently proposed. We show that for a subclass of these theories, the tensor modes are either not dynamicalmore » or are infinitely strongly coupled. Among the remaining theories for which the tensor modes are well-defined one counts one new model that is not field-redefinable to Horndeski via a conformal and disformal transformation but that does require the vacuum to break Lorentz invariance. We discuss the implications for the effective field theory of dark energy and the stability of the theory. In particular we find that if we restrict ourselves to the Extended Scalar-Tensor class of theories for which the tensors are well-behaved and the scalar is free from gradient or ghost instabilities on FLRW then we recover Horndeski up to field redefinitions.« less

76 FR 76812 - Requested Administrative Waiver of the Coastwise Trade Laws: Vessel BARBARY GHOST; Invitation for...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-08

... DEPARTMENT OF TRANSPORTATION Maritime Administration [Docket No. MARAD 2011 0148] Requested Administrative Waiver of the Coastwise Trade Laws: Vessel BARBARY GHOST; Invitation for Public Comments AGENCY... BARBARY GHOST is: Intended Commercial Use Of Vessel: ``Sightseeing tours in the San Francisco Bay for a...

Nonquadratic gauge fixing and ghosts for gauge theories on the hypersphere

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

Brandt, F. T.; McKeon, D. G. C.; Department of Mathematics and Computer Science, Algoma University, Sault St. Marie, Ontario P6A 2G4

2011-10-15

It has been suggested that using a gauge fixing Lagrangian that is not quadratic in a gauge fixing condition is most appropriate for gauge theories formulated on a hypersphere. We reexamine the appropriate ghost action that is to be associated with gauge fixing, applying a technique that has been used for ensuring that the propagator for a massless spin-two field is transverse and traceless. It is shown that this nonquadratic gauge fixing Lagrangian leads to two pair of complex Fermionic ghosts and two Bosonic real ghosts.

Broadband seismic : case study modeling and data processing

NASA Astrophysics Data System (ADS)

Cahyaningtyas, M. B.; Bahar, A.

2018-03-01

Seismic data with wide range of frequency is needed due to its close relation to resolution and the depth of the target. Low frequency provides deeper penetration for the imaging of deep target. In addition, the wider the frequency bandwidth, the sharper the wavelet. Sharp wavelet is responsible for high-resolution imaging and is very helpful to resolve thin bed. As a result, the demand for broadband seismic data is rising and it spurs the technology development of broadband seismic in oil and gas industry. An obstacle that is frequently found on marine seismic data is the existence of ghost that affects the frequency bandwidth contained on the seismic data. Ghost alters bandwidth to bandlimited. To reduce ghost effect and to acquire broadband seismic data, lots of attempts are used, both on the acquisition and on the processing of seismic data. One of the acquisition technique applied is the multi-level streamer, where some streamers are towed on some levels of depth. Multi-level streamer will yield data with varied ghost notch shown on frequency domain. If the ghost notches are not overlapping, the summation of multi-level streamer data will reduce the ghost effect. The result of the multi-level streamer data processing shows that reduction of ghost notch on frequency domain indeed takes place.

Publication ethics and the ghost management of medical publication.

PubMed

Sismondo, Sergio; Doucet, Mathieu

2010-07-01

It is by now no secret that some scientific articles are ghost authored - that is, written by someone other than the person whose name appears at the top of the article. Ghost authorship, however, is only one sort of ghosting. In this article, we present evidence that pharmaceutical companies engage in the ghost management of the scientific literature, by controlling or shaping several crucial steps in the research, writing, and publication of scientific articles. Ghost management allows the pharmaceutical industry to shape the literature in ways that serve its interests. This article aims to reinforce and expand publication ethics as an important area of concern for bioethics. Since ghost-managed research is primarily undertaken in the interests of marketing, large quantities of medical research violate not just publication norms but also research ethics. Much of this research involves human subjects, and yet is performed not primarily to increase knowledge for broad human benefit, but to disseminate results in the service of profits. Those who sponsor, manage, conduct, and publish such research therefore behave unethically, since they put patients at risk without justification. This leads us to a strong conclusion: if medical journals want to ensure that the research they publish is ethically sound, they should not publish articles that are commercially sponsored.

GPS-Based Reduced Dynamic Orbit Determination Using Accelerometer Data

NASA Technical Reports Server (NTRS)

VanHelleputte, Tom; Visser, Pieter

2007-01-01

Currently two gravity field satellite missions, CHAMP and GRACE, are equipped with high sensitivity electrostatic accelerometers, measuring the non-conservative forces acting on the spacecraft in three orthogonal directions. During the gravity field recovery these measurements help to separate gravitational and non-gravitational contributions in the observed orbit perturbations. For precise orbit determination purposes all these missions have a dual-frequency GPS receiver on board. The reduced dynamic technique combines the dense and accurate GPS observations with physical models of the forces acting on the spacecraft, complemented by empirical accelerations, which are stochastic parameters adjusted in the orbit determination process. When the spacecraft carries an accelerometer, these measured accelerations can be used to replace the models of the non-conservative forces, such as air drag and solar radiation pressure. This approach is implemented in a batch least-squares estimator of the GPS High Precision Orbit Determination Software Tools (GHOST), developed at DLR/GSOC and DEOS. It is extensively tested with data of the CHAMP and GRACE satellites. As accelerometer observations typically can be affected by an unknown scale factor and bias in each measurement direction, they require calibration during processing. Therefore the estimated state vector is augmented with six parameters: a scale and bias factor for the three axes. In order to converge efficiently to a good solution, reasonable a priori values for the bias factor are necessary. These are calculated by combining the mean value of the accelerometer observations with the mean value of the non-conservative force models and empirical accelerations, estimated when using these models. When replacing the non-conservative force models with accelerometer observations and still estimating empirical accelerations, a good orbit precision is achieved. 100 days of GRACE B data processing results in a mean orbit fit of a few centimeters with respect to high-quality JPL reference orbits. This shows a slightly better consistency compared to the case when using force models. A purely dynamic orbit, without estimating empirical accelerations thus only adjusting six state parameters and the bias and scale factors, gives an orbit fit for the GRACE B test case below the decimeter level. The in orbit calibrated accelerometer observations can be used to validate the modelled accelerations and estimated empirical accelerations computed with the GHOST tools. In along track direction they show the best resemblance, with a mean correlation coefficient of 93% for the same period. In radial and normal direction the correlation is smaller. During days of high solar activity the benefit of using accelerometer observations is clearly visible. The observations during these days show fluctuations which the modelled and empirical accelerations can not follow.

Classically Stable Nonsingular Cosmological Bounces

NASA Astrophysics Data System (ADS)

Ijjas, Anna; Steinhardt, Paul J.

2016-09-01

One of the fundamental questions of theoretical cosmology is whether the Universe can undergo a nonsingular bounce, i.e., smoothly transit from a period of contraction to a period of expansion through violation of the null energy condition (NEC) at energies well below the Planck scale and at finite values of the scale factor such that the entire evolution remains classical. A common claim has been that a nonsingular bounce either leads to ghost or gradient instabilities or a cosmological singularity. In this Letter, we consider a well-motivated class of theories based on the cubic Galileon action and present a procedure for explicitly constructing examples of a nonsingular cosmological bounce without encountering any pathologies and maintaining a subluminal sound speed for comoving curvature modes throughout the NEC violating phase. We also discuss the relation between our procedure and earlier work.

A robust mass spectrometry method for rapid profiling of erythrocyte ghost membrane proteomes.

PubMed

Fye, Haddy K S; Mrosso, Paul; Bruce, Lesley; Thézénas, Marie-Laëtitia; Davis, Simon; Fischer, Roman; Rwegasira, Gration L; Makani, Julie; Kessler, Benedikt M

2018-01-01

Red blood cell (RBC) physiology is directly linked to many human disorders associated with low tissue oxygen levels or anemia including chronic obstructive pulmonary disease, congenital heart disease, sleep apnea and sickle cell anemia. Parasites such as Plasmodium spp. and phylum Apicomplexa directly target RBCs, and surface molecules within the RBC membrane are critical for pathogen interactions. Proteomics of RBC membrane 'ghost' fractions has therefore been of considerable interest, but protocols described to date are either suboptimal or too extensive to be applicable to a larger set of clinical cohorts. Here, we describe an optimised erythrocyte isolation protocol from blood, tested for various storage conditions and explored using different fractionation conditions for isolating ghost RBC membranes. Liquid chromatography mass spectrometry (LC-MS) analysis on a Q-Exactive Orbitrap instrument was used to profile proteins isolated from the comparative conditions. Data analysis was run on the MASCOT and MaxQuant platforms to assess their scope and diversity. The results obtained demonstrate a robust method for membrane enrichment enabling consistent MS based characterisation of > 900 RBC membrane proteins in single LC-MS/MS analyses. Non-detergent based membrane solubilisation methods using the tissue and supernatant fractions of isolated ghost membranes are shown to offer effective haemoglobin removal as well as diverse recovery including erythrocyte membrane proteins of high and low abundance. The methods described in this manuscript propose a medium to high throughput framework for membrane proteome profiling by LC-MS of potential applicability to larger clinical cohorts in a variety of disease contexts.

GHOSTS I: A new faint very isolated dwarf galaxy at D = 12 ± 2 Mpc

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

Monachesi, Antonela; Bell, Eric F.; Radburn-Smith, David J.

2014-01-10

We report the discovery of a new faint dwarf galaxy, GHOSTS I, using HST/ACS data from one of our GHOSTS (Galaxy Halos, Outer disks, Substructure, Thick disk, and Star clusters) fields. Its detected individual stars populate an approximately 1 mag range of its luminosity function (LF). Using synthetic color-magnitude diagrams (CMDs) to compare with the galaxy's CMD, we find that the colors and magnitudes of GHOSTS I's individual stars are most consistent with being young helium-burning and asymptotic giant branch stars at a distance of ∼12 ± 2 Mpc. Morphologically, GHOSTS I appears to be actively forming stars, so wemore » tentatively classify it as a dwarf irregular (dIrr) galaxy, although future Hubble Space Telescope (HST) observations deep enough to resolve a larger magnitude range in its LF are required to make a more secure classification. GHOSTS I's absolute magnitude is M{sub V}∼−9.85{sub −0.33}{sup +0.40}, making it one of the least luminous dIrr galaxies known, and its metallicity is lower than [Fe/H] = –1.5 dex. The half-light radius of GHOSTS I is 226 ± 38 pc and its ellipticity is 0.47 ± 0.07, similar to Milky Way and M31 dwarf satellites at comparable luminosity. There are no luminous massive galaxies or galaxy clusters within ∼4 Mpc from GHOSTS I that could be considered as its host, making it a very isolated dwarf galaxy in the local universe.« less

Effects of ghost shrimp on zinc and cadmium in sediments from Tampa Bay, FL

USGS Publications Warehouse

Klerks, P.L.; Felder, D.L.; Strasser, K.; Swarzenski, P.W.

2007-01-01

This study investigated the effects that ghost shrimp have on the distribution of metals in sediment. We measured levels of HNO3-extractable zinc and cadmium in surface sediment, in ghost shrimp burrow walls and in sediment ejected by the ghost shrimp from their burrows, at five sandy intertidal sites in Tampa Bay. Ghost shrimp densities and their rate of sediment ejection were also quantified, as were sediment organic content and silt + clay content. Densities of ghost shrimp (Sergio trilobata and Lepidophthalmus louisianensis) averaged 33/m2 at our sites, and they ejected sediment at an average rate of 28 g/burrow/day. Levels of both Zn and Cd were significantly higher in burrow walls than in surface sediments. Sediment ejected by the shrimp from their burrows had elevated levels of Zn (relative to surface sediments) at one of the sites. Sediment organic content and silt + clay content were higher in burrow-wall sediments than in ejected sediment, which in turn tended to have values above those of surface sediments. Differences in levels of HNO3-extractable Zn and Cd among sediment types may be a consequence of these sediments differing in other physiochemical characteristics, though the differences in metal levels remained statistically significant for some sites after correcting for differences in organic content and silt + clay content. We conclude that the presence of ghost shrimp burrows contributes to spatial heterogeneity of sedimentary metal levels, while the ghost shrimp bioturbation results in a significant flux of metals to the sediment surface and is expected to decrease heterogeneity of metal levels in sedimentary depth profiles.

Elimination of 'ghost'-effect-related systematic error in metrology of X-ray optics with a long trace profiler

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

Yashchuk, Valeriy V.; Irick, Steve C.; MacDowell, Alastair A.

2005-04-28

A data acquisition technique and relevant program for suppression of one of the systematic effects, namely the ''ghost'' effect, of a second generation long trace profiler (LTP) is described. The ''ghost'' effect arises when there is an unavoidable cross-contamination of the LTP sample and reference signals into one another, leading to a systematic perturbation in the recorded interference patterns and, therefore, a systematic variation of the measured slope trace. Perturbations of about 1-2 {micro}rad have been observed with a cylindrically shaped X-ray mirror. Even stronger ''ghost'' effects show up in an LTP measurement with a mirror having a toroidal surfacemore » figure. The developed technique employs separate measurement of the ''ghost''-effect-related interference patterns in the sample and the reference arms and then subtraction of the ''ghost'' patterns from the sample and the reference interference patterns. The procedure preserves the advantage of simultaneously measuring the sample and reference signals. The effectiveness of the technique is illustrated with LTP metrology of a variety of X-ray mirrors.« less

Modulation of erythrocyte membrane mechanical stability by 2,3-diphosphoglycerate in the neonatal poikilocytosis/elliptocytosis syndrome.

PubMed Central

Mentzer, W C; Iarocci, T A; Mohandas, N; Lane, P A; Smith, B; Lazerson, J; Hays, T

1987-01-01

To explain the transient anemia and poikilocytosis seen during infancy in hereditary elliptocytosis (HE), we resealed erythrocyte (RBC) ghosts from affected children or their elliptocytic parents with 2,3-diphosphoglycerate (DPG) (0-8 mM), a compound that dissociates membrane skeletons, then measured ghost mechanical stability in the ektacytometer. Without added 2,3-DPG, ghost mechanical stability was subnormal in infantile poikilocytosis (IP) and HE but was even more abnormal in hereditary pyropoikilocytosis (HPP). Addition of 2,3-DPG (2.55 mM) to IP or HE ghosts, decreased their stability to that of HPP ghosts (without 2,3-DPG). Nonphysiological 2,3-DPG levels (6-8 mM) were required to elicit a similar effect in normal ghosts. The data suggest that free 2,3-DPG, present in neonatal RBC as a consequence of diminished binding to HbF, may render HE susceptible to in vivo fragmentation. The developmental switch from fetal to adult hemoglobin, by diminishing available free 2,3-DPG, may explain the abatement of poikilocytosis and hemolytic anemia that accompanies maturation. Images PMID:3818955

Biophysical Characterization of Copolymer-Protected Gene Vectors (COPROGs)

PubMed Central

Hönig, Daniel; DeRouchey, Jason; Jungmann, Ralf; Koch, Christian; Plank, Christian; Rädler, Joachim O.

2010-01-01

A copolymer-protected gene vector (COPROG) is a three component gene delivery system consisting of a preformed DNA and branched polyethylenimine (bPEI) complex subsequently modified by the addition of a copolymer (P6YE5C) incorporating both poly(ethylene glycol) (PEG) and anionic peptides. Using fluorescence correlation spectroscopy (FCS) and atomic force microscopy (AFM), we characterized and compared the self-assembly of bPEI/DNA particles and COPROG complexes. In low salt buffer, both bPEI/DNA and COPROG formulations form stable nanoparticles with hydrodynamic radii between 60–120 nm. COPROG particles, as compared to bPEI/DNA, show greatly improved particle stability to both physiological salt as well as low pH conditions. Binding stoichiometry of the three-component COPROG system was investigated by dual-color fluorescence cross-correlation spectroscopy (FCCS). It was found that a significant fraction of P6YE5C copolymer aggregates with excess bPEI forming bPEI/P6YE5C “ghost complexes” with no DNA inside. The ratio of ghost particles to COPROG complexes is about 4:1. In addition we find a large fraction of excess P6YE5C copolymer, which remains unbound in solution. We observe a 2–4 fold enhanced reporter gene expression with COPROG formulations at various equivalents as compared to bPEI-DNA alone. We believe that both complex stabilization as well as the capture of excess bPEI into ghost particles induced by the copolymer is responsible for the improvement in gene expression. PMID:20672861

Systematics, phylogeny, and taphonomy of ghost shrimps (Decapoda): a perspective from the fossil record

PubMed Central

Klompmaker, Adiël A.

2016-01-01

Ghost shrimps of Callianassidae and Ctenochelidae are soft-bodied, usually heterochelous decapods representing major bioturbators of muddy and sandy (sub)marine substrates. Ghost shrimps have a robust fossil record spanning from the Early Cretaceous (~ 133 Ma) to the Holocene and their remains are present in most assemblages of Cenozoic decapod crustaceans. Their taxonomic interpretation is in flux, mainly because the generic assignment is hindered by their insufficient preservation and disagreement in the biological classification. Furthermore, numerous taxa are incorrectly classified within the catch-all taxon Callianassa. To show the historical patterns in describing fossil ghost shrimps and to evaluate taphonomic aspects influencing the attribution of ghost shrimp remains to higher level taxa, a database of all fossil species treated at some time as belonging to the group has been compiled: 250 / 274 species are considered valid ghost shrimp taxa herein. More than half of these taxa (160 species, 58.4%) are known only from distal cheliped elements, i.e., dactylus and / or propodus, due to the more calcified cuticle locally. Rarely, ghost shrimps are preserved in situ in burrows or in direct association with them, and several previously unpublished occurrences are reported herein. For generic assignment, fossil material should be compared to living species because many of them have modern relatives. Heterochely, intraspecific variation, ontogenetic changes and sexual dimorphism are all factors that have to be taken into account when working with fossil ghost shrimps. Distal elements are usually more variable than proximal ones. Preliminary results suggest that the ghost shrimp clade emerged not before the Hauterivian (~ 133 Ma). The divergence of Ctenochelidae and Paracalliacinae is estimated to occur within the interval of Hauterivian to Albian (133–100 Ma). Callichirinae and Eucalliacinae likely diverged later during the Late Cretaceous (100–66 Ma), whereas Callianassinae did not appear before the Eocene (56 Ma). PMID:27499814

Gravitational lensing and ghost images in the regular Bardeen no-horizon spacetimes

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

Schee, Jan; Stuchlík, Zdeněk, E-mail: jan.schee@fpf.slu.cz, E-mail: zdenek.stuchlik@fpf.slu.cz

We study deflection of light rays and gravitational lensing in the regular Bardeen no-horizon spacetimes. Flatness of these spacetimes in the central region implies existence of interesting optical effects related to photons crossing the gravitational field of the no-horizon spacetimes with low impact parameters. These effects occur due to existence of a critical impact parameter giving maximal deflection of light rays in the Bardeen no-horizon spacetimes. We give the critical impact parameter in dependence on the specific charge of the spacetimes, and discuss 'ghost' direct and indirect images of Keplerian discs, generated by photons with low impact parameters. The ghostmore » direct images can occur only for large inclination angles of distant observers, while ghost indirect images can occur also for small inclination angles. We determine the range of the frequency shift of photons generating the ghost images and determine distribution of the frequency shift across these images. We compare them to those of the standard direct images of the Keplerian discs. The difference of the ranges of the frequency shift on the ghost and direct images could serve as a quantitative measure of the Bardeen no-horizon spacetimes. The regions of the Keplerian discs giving the ghost images are determined in dependence on the specific charge of the no-horizon spacetimes. For comparison we construct direct and indirect (ordinary and ghost) images of Keplerian discs around Reissner-Nördström naked singularities demonstrating a clear qualitative difference to the ghost direct images in the regular Bardeen no-horizon spacetimes. The optical effects related to the low impact parameter photons thus give clear signature of the regular Bardeen no-horizon spacetimes, as no similar phenomena could occur in the black hole or naked singularity spacetimes. Similar direct ghost images have to occur in any regular no-horizon spacetimes having nearly flat central region.« less

Pretangles and neurofibrillary changes: similarities and differences between AD and CBD based on molecular and morphological evolution.

PubMed

Uchihara, Toshiki

2014-12-01

Pretangles are cytoplasmic tau immunoreactivity in neurons without apparent formation of fibrillary structures. In Alzheimer disease, such tau deposition is considered to represent a premature state prior to fibril formation (AD-pretangles), later to form neurofibrillary tangles and finally ghost tangles. This morphological evolution from pretangles to ghost tangles is in parallel with their profile shift from four repeat (4R) tau-positive pretangles to three repeat (3R) tau-positive ghost tangles with both positive neurofibrillary tangles in between. This complementary shift of tau profile from 4R to 3R suggests that these tau epitopes are represented interchangeably along tangle evolution. Similar tau immunoreactivity without fibril formation is also observed in corticobasal degeneration (CBD-pretangles). CBD-pretangles and AD-pretangles share: (i) selective 4R tau immunoreactivity without involvement of 3R tau; and (ii) argyrophilia with Gallyas silver impregnation. However, CBD-pretangles neither evolve into ghost tangles nor exhibit 3R tau immunoreactivity even at the advanced stage. Because electron microscopic studies on these pretangles are quite limited, it remains to be clarified whether such differences in later evolution are related to their primary ultrastructures, potentially distinct between AD and CBD. As double staining for 3R and 4R tau clarified complementary shift from 4R to 3R tau along evolution from pretangles to ghost tangles, double immunoelectron microscopy, if possible, may clarify similar profile shifts in relation to each tau fibril at the ultrastructural dimension. This will provide a unique viewpoint on how molecular (epitope) representations are related to pathogenesis of fibrillary components. © 2014 Japanese Society of Neuropathology.

Wormhole solutions in f(R) gravity satisfying energy conditions

NASA Astrophysics Data System (ADS)

Mazharimousavi, S. Habib; Halilsoy, M.

2016-10-01

Without reference to exotic sources construction of viable wormholes in Einstein’s general relativity remained ever a myth. With the advent of modified theories, however, specifically the f(R) theory, new hopes arose for the possibility of such objects. From this token, we construct traversable wormholes in f(R) theory supported by a fluid source which respects at least the weak energy conditions. We provide an example (Example 1) of asymptotically flat wormhole in f(R) gravity without ghosts.

Variational method for lattice spectroscopy with ghosts

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

Burch, Tommy; Hagen, Christian; Gattringer, Christof

2006-01-01

We discuss the variational method used in lattice spectroscopy calculations. In particular we address the role of ghost contributions which appear in quenched or partially quenched simulations and have a nonstandard euclidean time dependence. We show that the ghosts can be separated from the physical states. Our result is illustrated with numerical data for the scalar meson.

Visions of Inflation in World History: Ghost Story III

ERIC Educational Resources Information Center

Niederjohn, M. Scott; Schug, Mark C.; Wood, William C.

2013-01-01

This article represents the third in a "ghost story" series by the same authors. Readers may recall that Mr. Bernanke was "visited" by the ghosts of Adam Smith and John Maynard Keynes in the March/April 2010 issue of "Social Education" as these two famous economists debated the economic recovery (see EJ878912). Mr.…

Polarization-multiplexing ghost imaging

NASA Astrophysics Data System (ADS)

Dongfeng, Shi; Jiamin, Zhang; Jian, Huang; Yingjian, Wang; Kee, Yuan; Kaifa, Cao; Chenbo, Xie; Dong, Liu; Wenyue, Zhu

2018-03-01

A novel technique for polarization-multiplexing ghost imaging is proposed to simultaneously obtain multiple polarimetric information by a single detector. Here, polarization-division multiplexing speckles are employed for object illumination. The light reflected from the objects is detected by a single-pixel detector. An iterative reconstruction method is used to restore the fused image containing the different polarimetric information by using the weighted sum of the multiplexed speckles based on the correlation coefficients obtained from the detected intensities. Next, clear images of the different polarimetric information are recovered by demultiplexing the fused image. The results clearly demonstrate that the proposed method is effective.

Edge detection based on computational ghost imaging with structured illuminations

NASA Astrophysics Data System (ADS)

Yuan, Sheng; Xiang, Dong; Liu, Xuemei; Zhou, Xin; Bing, Pibin

2018-03-01

Edge detection is one of the most important tools to recognize the features of an object. In this paper, we propose an optical edge detection method based on computational ghost imaging (CGI) with structured illuminations which are generated by an interference system. The structured intensity patterns are designed to make the edge of an object be directly imaged from detected data in CGI. This edge detection method can extract the boundaries for both binary and grayscale objects in any direction at one time. We also numerically test the influence of distance deviations in the interference system on edge extraction, i.e., the tolerance of the optical edge detection system to distance deviation. Hopefully, it may provide a guideline for scholars to build an experimental system.

Optical identity authentication technique based on compressive ghost imaging with QR code

NASA Astrophysics Data System (ADS)

Wenjie, Zhan; Leihong, Zhang; Xi, Zeng; Yi, Kang

2018-04-01

With the rapid development of computer technology, information security has attracted more and more attention. It is not only related to the information and property security of individuals and enterprises, but also to the security and social stability of a country. Identity authentication is the first line of defense in information security. In authentication systems, response time and security are the most important factors. An optical authentication technology based on compressive ghost imaging with QR codes is proposed in this paper. The scheme can be authenticated with a small number of samples. Therefore, the response time of the algorithm is short. At the same time, the algorithm can resist certain noise attacks, so it offers good security.

Comparative seed germination and seedling development of the ghost orchid, Dendrophylax lindenii (Orchidaceae), and molecular identification of its mycorrhizal fungus from South Florida

PubMed Central

Hoang, Nguyen H.; Kane, Michael E.; Radcliffe, Ellen N.; Zettler, Lawrence W.; Richardson, Larry W.

2017-01-01

Background and Aims The endangered leafless ghost orchid, Dendrophylax lindenii, one of the most renowned orchids in the world, is difficult to grow under artificial conditions. Published information on asymbiotic and symbiotic (co-culture with a mycobiont) seed germination, seedling anatomy and developmental morphology of this leafless orchid is completely lacking. This information is critical for the development of efficient procedures for ghost orchid production for successful reintroduction. Methods Ghost orchid seedling early development stages were morphologically and anatomically defined to compare germination, embryo and protocorm maturation and seedling development during asymbiotic and symbiotic culture with one of two mycorrhizal strains (Dlin-379 and Dlin-394) isolated from ghost orchid roots in situ. Key Results Seeds symbiotically germinated at higher rates when cultured with fungal strain Dlin-394 than with strain Dlin-379 or asymbiotically on P723 medium during a 10-week culture period. Fungal pelotons were observed in protocorm cells co-cultured with strain Dlin-394 but not Dlin-379. Some 2-year-old seedlings produced multinode inflorescences in vitro. Production of keikis from inflorescence nodes indicated the capacity for clonal production in the ghost orchid. Conclusions Ghost orchid embryo and seedling development were characterized into seven stages. Fungal strain Dlin-394 was confirmed as a possible ghost orchid germination mycobiont, which significantly promoted seed germination and seedling development. Internal transcribed spacer sequencing data confirmed that Dlin-394 belongs within the genus Ceratobasidium. These results offer the opportunity to examine the benefits of using a mycobiont to enhance in vitro germination and possibly ex vitro acclimatization and sustainability following outplanting. PMID:28025292

Comparative seed germination and seedling development of the ghost orchid, Dendrophylax lindenii (Orchidaceae), and molecular identification of its mycorrhizal fungus from South Florida.

PubMed

Hoang, Nguyen H; Kane, Michael E; Radcliffe, Ellen N; Zettler, Lawrence W; Richardson, Larry W

2017-02-01

The endangered leafless ghost orchid, Dendrophylax lindenii, one of the most renowned orchids in the world, is difficult to grow under artificial conditions. Published information on asymbiotic and symbiotic (co-culture with a mycobiont) seed germination, seedling anatomy and developmental morphology of this leafless orchid is completely lacking. This information is critical for the development of efficient procedures for ghost orchid production for successful reintroduction. Ghost orchid seedling early development stages were morphologically and anatomically defined to compare germination, embryo and protocorm maturation and seedling development during asymbiotic and symbiotic culture with one of two mycorrhizal strains (Dlin-379 and Dlin-394) isolated from ghost orchid roots in situ KEY RESULTS: Seeds symbiotically germinated at higher rates when cultured with fungal strain Dlin-394 than with strain Dlin-379 or asymbiotically on P723 medium during a 10-week culture period. Fungal pelotons were observed in protocorm cells co-cultured with strain Dlin-394 but not Dlin-379. Some 2-year-old seedlings produced multinode inflorescences in vitro Production of keikis from inflorescence nodes indicated the capacity for clonal production in the ghost orchid. Ghost orchid embryo and seedling development were characterized into seven stages. Fungal strain Dlin-394 was confirmed as a possible ghost orchid germination mycobiont, which significantly promoted seed germination and seedling development. Internal transcribed spacer sequencing data confirmed that Dlin-394 belongs within the genus Ceratobasidium These results offer the opportunity to examine the benefits of using a mycobiont to enhance in vitro germination and possibly ex vitro acclimatization and sustainability following outplanting. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company.

High Speed Computational Ghost Imaging via Spatial Sweeping

NASA Astrophysics Data System (ADS)

Wang, Yuwang; Liu, Yang; Suo, Jinli; Situ, Guohai; Qiao, Chang; Dai, Qionghai

2017-03-01

Computational ghost imaging (CGI) achieves single-pixel imaging by using a Spatial Light Modulator (SLM) to generate structured illuminations for spatially resolved information encoding. The imaging speed of CGI is limited by the modulation frequency of available SLMs, and sets back its practical applications. This paper proposes to bypass this limitation by trading off SLM’s redundant spatial resolution for multiplication of the modulation frequency. Specifically, a pair of galvanic mirrors sweeping across the high resolution SLM multiply the modulation frequency within the spatial resolution gap between SLM and the final reconstruction. A proof-of-principle setup with two middle end galvanic mirrors achieves ghost imaging as fast as 42 Hz at 80 × 80-pixel resolution, 5 times faster than state-of-the-arts, and holds potential for one magnitude further multiplication by hardware upgrading. Our approach brings a significant improvement in the imaging speed of ghost imaging and pushes ghost imaging towards practical applications.

Repressed ghosts and dissociated vampires in the enacted dimension of psychoanalytic treatment.

PubMed

Katz, Gil

2015-04-01

One of the most evocative uses of the metaphor of a ghost in psychoanalytic writing was crafted by Hans Loewald in "On the Therapeutic Action of Psycho-Analysis" (1960). In this seminal work, Loewald likened the process of psychoanalytic change to that of transforming psychic ghosts into ancestors. In the present paper, the author supplements the metaphor of ghosts that haunt with the metaphor of vampires that menace, and links these two alien experiences to two psychological processes: repression and dissociation. Descriptions of ghosts and vampires in folklore, and the ways they are experienced in analytic treatment, are followed by an explication of the enacted dimension of analytic process-the arena of treatment in which all demons are inevitably revivified, "recognized," and ultimately laid to rest. The paper includes a clinical illustration of a dissociated vampire: a Holocaust trauma transmitted across three generations of survivors. © 2015 The Psychoanalytic Quarterly, Inc.

Ghost dark matter

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

Furukawa, Tomonori; Yokoyama, Shuichiro; Ichiki, Kiyotomo

2010-05-01

We revisit ghost dark matter, the possibility that ghost condensation may serve as an alternative to dark matter. In particular, we investigate the Friedmann-Robertson-Walker (FRW) background evolution and the large-scale structure (LSS) in the ΛGDM universe, i.e. a late-time universe dominated by a cosmological constant and ghost dark matter. The FRW background of the ΛGDM universe is indistinguishable from that of the standard ΛCDM universe if M∼>1eV, where M is the scale of spontaneous Lorentz breaking. From the LSS we find a stronger bound: M∼>10eV. For smaller M, ghost dark matter would have non-negligible sound speed after the matter-radiation equality,more » and thus the matter power spectrum would significantly differ from observation. These bounds are compatible with the phenomenological upper bound M∼<100GeV known in the literature.« less

A review of ghost gear entanglement amongst marine mammals, reptiles and elasmobranchs.

PubMed

Stelfox, Martin; Hudgins, Jillian; Sweet, Michael

2016-10-15

This review focuses on the effect that ghost gear entanglement has on marine megafauna, namely mammals, reptiles and elasmobranchs. A total of 76 publications and other sources of grey literature were assessed, and these highlighted that over 5400 individuals from 40 different species were recorded as entangled in, or associated with, ghost gear. Interestingly, there appeared to be a deficit of research in the Indian, Southern, and Arctic Oceans; and so, we recommend that future studies focus efforts on these areas. Furthermore, studies assessing the effects of ghost gear on elasmobranchs, manatees, and dugongs should also be prioritised, as these groups were underrepresented in the current literature. The development of regional databases, capable of recording entanglement incidences following a minimum global set of criteria, would be a logical next step in order to analyse the effect that ghost gear has on megafauna populations worldwide. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Cosmological perturbations of a perfect fluid and noncommutative variables

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

De Felice, Antonio; Gerard, Jean-Marc; Suyama, Teruaki

2010-03-15

We describe the linear cosmological perturbations of a perfect fluid at the level of an action, providing thus an alternative to the standard approach based only on the equations of motion. This action is suited not only to perfect fluids with a barotropic equation of state, but also to those for which the pressure depends on two thermodynamical variables. By quantizing the system we find that (1) some perturbation fields exhibit a noncommutativity quite analogous to the one observed for a charged particle moving in a strong magnetic field, (2) local curvature and pressure perturbations cannot be measured simultaneously, (3)more » ghosts appear if the null energy condition is violated.« less

Computational Ghost Imaging for Remote Sensing

NASA Technical Reports Server (NTRS)

Erkmen, Baris I.

2012-01-01

This work relates to the generic problem of remote active imaging; that is, a source illuminates a target of interest and a receiver collects the scattered light off the target to obtain an image. Conventional imaging systems consist of an imaging lens and a high-resolution detector array [e.g., a CCD (charge coupled device) array] to register the image. However, conventional imaging systems for remote sensing require high-quality optics and need to support large detector arrays and associated electronics. This results in suboptimal size, weight, and power consumption. Computational ghost imaging (CGI) is a computational alternative to this traditional imaging concept that has a very simple receiver structure. In CGI, the transmitter illuminates the target with a modulated light source. A single-pixel (bucket) detector collects the scattered light. Then, via computation (i.e., postprocessing), the receiver can reconstruct the image using the knowledge of the modulation that was projected onto the target by the transmitter. This way, one can construct a very simple receiver that, in principle, requires no lens to image a target. Ghost imaging is a transverse imaging modality that has been receiving much attention owing to a rich interconnection of novel physical characteristics and novel signal processing algorithms suitable for active computational imaging. The original ghost imaging experiments consisted of two correlated optical beams traversing distinct paths and impinging on two spatially-separated photodetectors: one beam interacts with the target and then illuminates on a single-pixel (bucket) detector that provides no spatial resolution, whereas the other beam traverses an independent path and impinges on a high-resolution camera without any interaction with the target. The term ghost imaging was coined soon after the initial experiments were reported, to emphasize the fact that by cross-correlating two photocurrents, one generates an image of the target. In CGI, the measurement obtained from the reference arm (with the high-resolution detector) is replaced by a computational derivation of the measurement-plane intensity profile of the reference-arm beam. The algorithms applied to computational ghost imaging have diversified beyond simple correlation measurements, and now include modern reconstruction algorithms based on compressive sensing.

The Ghost in the Touchscreen: Social Scaffolds Promote Learning by Toddlers

ERIC Educational Resources Information Center

Zimmermann, Laura; Moser, Alecia; Lee, Herietta; Gerhardstein, Peter; Barr, Rachel

2017-01-01

This study examined the effect of a "ghost" demonstration on toddlers' imitation. In the "ghost" condition, virtual pieces moved to make a fish or boat puzzle. Fifty-two 2.5- and 3-year-olds were tested on a touchscreen (no transfer) or with 3D pieces (transfer); children tested with 3D pieces scored above a no demonstration…

Lorentz violation and Faddeev-Popov ghosts

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

Altschul, B.

2006-02-15

We consider how Lorentz-violating interactions in the Faddeev-Popov ghost sector will affect scalar QED. The behavior depends sensitively on whether the gauge symmetry is spontaneously broken. If the symmetry is not broken, Lorentz violations in the ghost sector are unphysical, but if there is spontaneous breaking, radiative corrections will induce Lorentz-violating and gauge-dependent terms in other sectors of the theory.

50 CFR 648.144 - Gear restrictions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... spacing may be adjusted pursuant to the procedures in § 648.140. (3) Ghost panel. Black sea bass traps or pots must contain a ghost panel affixed to the trap or pot with degradable fasteners and hinges. The opening to be covered by the ghost panel must measure at least 3.0 inches (7.62 cm) by 6.0 inches (15.24...

How Do We Think about Death?--A Cultural Glance of Superstitious Ideas from Chinese and Western Ghost Festivals

ERIC Educational Resources Information Center

Zhang, Wenli

2009-01-01

Superstitious ideas are always in people's life in spite of scientific and technological advancement. Hungry Ghost Festival in China, Halloween in some western countries and Day of the Dead in Mexico are three religious festivals which are observed every year. They reveal people's idea about ghosts and spirits after death. They also include…

Pedagogies of Hauntology in History Education: Learning to Live with the Ghosts of Disappeared Victims of War and Dictatorship

ERIC Educational Resources Information Center

Zembylas, Michalinos

2013-01-01

Michalinos Zembylas examines how history education can be reconceived in terms of Jacques Derrida's notion of "hauntology," that is, as an ongoing conversation with the "ghost"--in the case of this essay, the ghosts of disappeared victims of war and dictatorship. Here, Zembylas uses hauntology as both metaphor and pedagogical methodology for…

Harry Potter and the Ghost Teacher: Resurrecting the Lost Art of Lecturing

ERIC Educational Resources Information Center

McDaniel, Kathryn N.

2010-01-01

A significant image of classroom lectures is the one presented in J. K. Rowling's "Harry Potter" series. At Harry's Hogwarts School of Witchcraft and Wizardry, the most torturous class is easily History of Magic, which is, incidentally, the only class in the school taught by a ghost. Being taught by a ghost could be quite exciting: not so in…

Ghost-Free Theory with Third-Order Time Derivatives

NASA Astrophysics Data System (ADS)

Motohashi, Hayato; Suyama, Teruaki; Yamaguchi, Masahide

2018-06-01

As the first step to extend our understanding of higher-derivative theories, within the framework of analytic mechanics of point particles, we construct a ghost-free theory involving third-order time derivatives in Lagrangian. While eliminating linear momentum terms in the Hamiltonian is necessary and sufficient to kill the ghosts associated with higher derivatives for Lagrangian with at most second-order derivatives, we find that this is necessary but not sufficient for the Lagrangian with higher than second-order derivatives. We clarify a set of ghost-free conditions under which we show that the Hamiltonian is bounded, and that equations of motion are reducible into a second-order system.

Ghosts in the self-accelerating DGP branch with Gauss–Bonnet effect

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

Liu, Yen-Wei; Izumi, Keisuke; Bouhmadi-López, Mariam

2015-06-01

The Dvali–Gabadadze–Porrati brane-world model provides a possible approach to address the late-time cosmic acceleration. However, it has subsequently been pointed out that a ghost instability will arise on the self-accelerating branch. Here, we carefully investigate whether this ghost problem could be possibly cured by introducing the Gauss–Bonnet term in the five-dimensional bulk action, a natural generalization to the Dvali–Gabadadze–Porrati model. Our analysis is carried out for a background where a de Sitter brane is embedded in an anti–de Sitter bulk. Our result shows that the ghost excitations cannot be avoided even in this modified model.

Ghost imaging with bucket detection and point detection

NASA Astrophysics Data System (ADS)

Zhang, De-Jian; Yin, Rao; Wang, Tong-Biao; Liao, Qing-Hua; Li, Hong-Guo; Liao, Qinghong; Liu, Jiang-Tao

2018-04-01

We experimentally investigate ghost imaging with bucket detection and point detection in which three types of illuminating sources are applied: (a) pseudo-thermal light source; (b) amplitude modulated true thermal light source; (c) amplitude modulated laser source. Experimental results show that the quality of ghost images reconstructed with true thermal light or laser beam is insensitive to the usage of bucket or point detector, however, the quality of ghost images reconstructed with pseudo-thermal light in bucket detector case is better than that in point detector case. Our theoretical analysis shows that the reason for this is due to the first order transverse coherence of the illuminating source.

Ghosting in anaglyphic stereoscopic images

NASA Astrophysics Data System (ADS)

Woods, Andrew J.; Rourke, Tegan

2004-05-01

Anaglyphic 3D images are an easy way of displaying stereoscopic 3D images on a wide range of display types, e.g. CRT, LCD, print, etc. While the anaglyphic 3D image method is cheap and accessible, its use requires a compromise in stereoscopic image quality. A common problem with anaglyphic 3D images is ghosting. Ghosting (or crosstalk) is the leaking of an image to one eye, when it is intended exclusively for the other eye. Ghosting degrades the ability of the observer to fuse the stereoscopic image and hence the quality of the 3D image is reduced. Ghosting is present in various levels with most stereoscopic displays, however it is often particularly evident with anaglyphic 3D images. This paper describes a project whose aim was to characterize the presence of ghosting in anaglyphic 3D images due to spectral issues. The spectral response curves of several different display types and several different brands of anaglyph glasses were measured using a spectroradiometer or spectrophotometer. A mathematical model was then developed to predict the amount of crosstalk in anaglyphic 3D images when different combinations of displays and glasses are used, and therefore predict the best type of anaglyph glasses for use with a particular display type.

Cryptanalysis and security enhancement of optical cryptography based on computational ghost imaging

NASA Astrophysics Data System (ADS)

Yuan, Sheng; Yao, Jianbin; Liu, Xuemei; Zhou, Xin; Li, Zhongyang

2016-04-01

Optical cryptography based on computational ghost imaging (CGI) has attracted much attention of researchers because it encrypts plaintext into a random intensity vector rather than complexed-valued function. This promising feature of the CGI-based cryptography reduces the amount of data to be transmitted and stored and therefore brings convenience in practice. However, we find that this cryptography is vulnerable to chosen-plaintext attack because of the linear relationship between the input and output of the encryption system, and three feasible strategies are proposed to break it in this paper. Even though a large number of plaintexts need to be chosen in these attack methods, it means that this cryptography still exists security risks. To avoid these attacks, a security enhancement method utilizing an invertible matrix modulation is further discussed and the feasibility is verified by numerical simulations.

Derivation of energy-based base shear force coefficient considering hysteretic behavior and P-delta effects

NASA Astrophysics Data System (ADS)

Ucar, Taner; Merter, Onur

2018-01-01

A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom (MDOF) system is approximated by using the modal energy-decomposition. Energy-based base shear coefficients are verified by means of both pushover analysis and nonlinear time history (NLTH) analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation.

Ghost-Free APT Analysis of Perturbative QCD Observables

NASA Astrophysics Data System (ADS)

Shirkov, Dmitry V.

The review of the essence and of application of recently devised ghost-free Analytic Perturbation Theory (APT) is presented. First, we discuss the main intrinsic problem of perturbative QCD - ghost singularities and with the resume of its resolving within the APT. By examples for diverse energy and momentum transfer values we show the property of better convergence for the APT modified QCD expansion. It is shown that in the APT analysis the three-loop contribution (sim alpha_s^3) is numerically inessential. This gives raise a hope for practical solution of the well-known problem of non-satisfactory convergence of QFT perturbation series due to its asymptotic nature. Our next result is that a usual perturbative analysis of time-like events is not adequate at sleq 2 GeV2. In particular, this relates to tau decay. Then, for the "high" (f=5) region it is shown that the common NLO, NLLA perturbation approximation widely used there (at 10 GeV lesssimsqrt{s}lesssim 170 GeV) yields a systematic theoretic negative error of a couple per cent level for the bar {alpha}_s^2 values. This results in a conclusion that the bar α_s(M^2_Z) value averaged over the f=5 data appreciably differs < bar {alpha}_s(M^2_Z)rangle_{f=5} simeq 0.124 from the currently popular "world average" (=0.118 ).

Ghostbusters in f ( R) supergravity

NASA Astrophysics Data System (ADS)

Fujimori, Toshiaki; Nitta, Muneto; Ohashi, Keisuke; Yamada, Yusuke

2018-05-01

f ( R) supergravity is known to contain a ghost mode associated with higher-derivative terms if it contains R n with n greater than two. We remove the ghost in f ( R) supergravity by introducing auxiliary gauge field to absorb the ghost. We dub this method as the ghostbuster mechanism [1]. We show that the mechanism removes the ghost super-multiplet but also terms including R n with n ≥ 3, after integrating out auxiliary degrees of freedom. For pure supergravity case, there appears an instability in the resultant scalar potential. We then show that the instability of the scalar potential can be cured by introducing matter couplings in such a way that the system has a stable potential.

Chandra Finds Ghosts Of Eruption In Galaxy Cluster

NASA Astrophysics Data System (ADS)

2002-01-01

"Ghostly" relics of an ancient eruption that tore through a cluster of galaxies were recently uncovered by NASA's Chandra X-ray Observatory. The discovery implies that galaxy clusters are the sites of enormously energetic and recurring explosions, and may provide an explanation why galaxy clusters behave like giant cosmic magnets. "Chandra's image revealed vast regions in the galaxy cluster Abell 2597 that contain almost no X-ray or radio emission. We call them ghost cavities," said Brian McNamara of Ohio University in Athens today during a press conference at the American Astronomical Society meeting in Washington. "They appear to be remnants of an old explosion where the radio emission has faded away over millions of years." The ghost cavities were likely created by extremely powerful explosions, due to material falling toward a black hole millions of times more massive than the Sun. As the matter swirled around the black hole, located in a galaxy near the center of the cluster, it generated enormous electromagnetic fields that expelled material from the vicinity of the black hole at high speeds. This explosive activity in Abell 2597 created jets of highly energetic particles that cleared out voids in the hot gas. Because they are lighter than the surrounding material, the cavities will eventually push their way to the edge of the cluster, just as air bubbles in water make their way to the surface. Researchers also found evidence that this explosion was not a one-time event. "We detected a small, bright radio source near the center of the cluster that indicates a new explosion has occurred recently," said team member Michael Wise of the Massachusetts Institute of Technology in Cambridge, "so the cycle of eruption is apparently continuing." Though dim, the ghost cavities are not completely empty. They contain a mixture of very hot gas, high-energy particles and magnetic fields -- otherwise the cavities would have collapsed under the pressure of the surrounding hot gas. "Ghost cavities may be the vessels that transport magnetic fields generated in a disk surrounding a giant black hole to the cluster gas that is spread over a region a billion times larger," said McNamara. If dozens of these cavities were created over the life of the cluster, they could explain the surprisingly strong magnetic field of the multimillion-degree gas that pervades the cluster. Galaxy clusters are the largest known gravitationally bound structures in the universe. Hundreds of galaxies swarm in giant reservoirs of multimillion-degree gas that radiates most of its energy in X-rays. Over the course of billions of years some of the gas should cool and sink toward a galaxy in the center of the cluster where it could trigger an outburst in the vicinity of the central massive black hole. Chandra observed Abell 2597 on July 28, 2000,for 40,000 seconds with the Advanced CCD Imaging Spectrometer (ACIS) instrument. Pennsylvania State University, University Park, and MIT developed the instrument for NASA. In addition to a group of astronomers from the Space Telescope Science Institute, Baltimore, and the University of Virginia, Charlottesville, the team included: Paul Nulsen, University of Wollagong, Australia; Larry David, Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.; Chris Carilli, National Radio Astronomy Observatory, Socorro, N.M.; and Craig Sarazin, University of Virginia. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program, and TRW, Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Mass.

Study of distributed fiber-optic laser-ultrasound generation based on ghost-mode of tilted fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Tian, Jiajun; Zhang, Qi; Han, Ming

2013-05-01

Fiber-optic ultrasonic transducers are an important component of an active ultrasonic testing system for structural health monitoring. Fiber-optic transducers have several advantages such as small size, light weight, and immunity to electromagnetic interference that make them much more attractive than the current available piezoelectric transducers, especially as embedded and permanent transducers in active ultrasonic testing for structural health monitoring. In this paper, a distributed fiber-optic laser-ultrasound generation based on the ghost-mode of tilted fiber Bragg gratings is studied. The influences of the laser power and laser pulse duration on the laser-ultrasound generation are investigated. The results of this paper are helpful to understand the working principle of this laser-ultrasound method and improve the ultrasonic generation efficiency.

An elastic dimpling instability with Kosterlitz-Thouless character and a precursor role in creasing

NASA Astrophysics Data System (ADS)

Engstrom, Tyler; Paulsen, Joseph; Schwarz, Jennifer

Creasing instability, also known as sulcification, occurs in a variety of quasi-2d elastic systems subject to compressive plane strain, and has been proposed as a mechanism of brain folding. While the dynamics of pre-existing creases can be understood in terms of crack propagation, a detailed critical phenomena picture of the instability is lacking. We show that surface dimpling is an equilibrium phase transition, and can be described in a language of quasi-particle excitations conceptualized as ``ghost fibers'' within the shear lag model. Tension-compression pairs (dipoles) of ghost fibers are energetically favorable at low strains, and the pairs unbind at a critical compressive plane strain, analogously to vortices in the Kosterlitz-Thouless transition. This dimpling transition bears strong resemblance to the creasing instability. We argue that zero-length creases are ghost fibers, which are a special case of ``ghost slabs''. Critical strain of a ghost slab increases linearly with its length, and is independent of both shear modulus and system thickness.

On non-primitively divergent vertices of Yang-Mills theory

NASA Astrophysics Data System (ADS)

Huber, Markus Q.

2017-11-01

Two correlation functions of Yang-Mills beyond the primitively divergent ones, the two-ghost-two-gluon and the four-ghost vertices, are calculated and their influence on lower vertices is examined. Their full (transverse) tensor structure is taken into account. As input, a solution of the full two-point equations - including two-loop terms - is used that respects the resummed perturbative ultraviolet behavior. A clear hierarchy is found with regard to the color structure that reduces the number of relevant dressing functions. The impact of the two-ghost-two-gluon vertex on the three-gluon vertex is negligible, which is explained by the fact that all non-small dressing functions drop out due to their color factors. Only in the ghost-gluon vertex a small net effect below 2% is seen. The four-ghost vertex is found to be extremely small in general. Since these two four-point functions do not enter into the propagator equations, these findings establish their small overall effect on lower correlation functions.

Frustrated Magnetism in Low-Dimensional Lattices

NASA Astrophysics Data System (ADS)

Tovar, Mayra

2011-12-01

In this dissertation we present the results of a theoretical investigation of spin models on two-dimensional and quasi one-dimensional lattices, all unified under the concept of quantum frustrated antiferromagnetism, and all discussing various aspects of the antiferromagnetic Heisenberg model on the kagome lattice. In the Introduction (Chapter 1), we discuss at some length such concepts as frustration and superexchange, among others, which are of common relevance in the rest of the chapters. In Chapter 2, we study the effect of Dzyaloshinskii-Moriya (DM) interactions on the zero-temperature magnetic susceptibility of systems whose low energy can be described by short-range valence bond states. Our work shows that this treatment is consistent with the experimentally observed non-vanishing susceptibility---in the specified temperature limit---of the spin-1/2 kagome antiferromagnetic compound ZnCu3(OH)6Cl2, also known as herbertsmithite. Although the objective of this work is explaining the aforementioned characteristic of the experimental system, our methods are more general and we apply them to the checkerboard and Shastry-Sutherland lattices as well. In Chapter 3, we discuss our findings in the study of ghost-mediated domain wall interactions in the diamondback ladder. These domain walls are the the spin excitations---the kinks and the antikinks---separating the ground states along one chain of the ladder. While as individual entities an antikink is energy costly and a kink energy free, our study finds that both interact via the ghosts that they produce in the opposite side of the ladder from where they are located. Through the study of these ghosts, we find that domain walls proliferate in the system above a critical value of the system's coupling constants. It is this proliferation that makes their treatment as free, non-interacting particles impossible, so we study here their interactions both quantitatively and qualitatively, in a region where the latter are yet not very strong, namely below the critical point. Based on the calculated two-body interaction potential, domain walls interact attractively (repulsively) when separated at even (odd) distances, with a strength that decays as 1/sp, where s is their separation and p<1. We also consider higher-order interactions. In the last chapter, Chapter 4, we present our study of the spin-1 kagome Heisenberg antiferromagnet. Our approach is to first consider an SU(2)-symmetric parent Hamiltonian with known ground states on the S=1 kagome lattice, in which nearest-neighbor Heisenberg interactions are already present. We then enhance these interactions by an additional Heisenberg term added perturbatively in order to move the system closer to a pure Heisenberg antiferromagnet. The results of this enhancement is obtaining a description of the system in terms of an effective Hamiltonian, namely a transverse field Ising AF on the triangular lattice. Based on the particular values of this effective Hamiltonian, our system is found to be in the order-by-disorder phase.

Scene-based nonuniformity correction using local constant statistics.

PubMed

Zhang, Chao; Zhao, Wenyi

2008-06-01

In scene-based nonuniformity correction, the statistical approach assumes all possible values of the true-scene pixel are seen at each pixel location. This global-constant-statistics assumption does not distinguish fixed pattern noise from spatial variations in the average image. This often causes the "ghosting" artifacts in the corrected images since the existing spatial variations are treated as noises. We introduce a new statistical method to reduce the ghosting artifacts. Our method proposes a local-constant statistics that assumes that the temporal signal distribution is not constant at each pixel but is locally true. This considers statistically a constant distribution in a local region around each pixel but uneven distribution in a larger scale. Under the assumption that the fixed pattern noise concentrates in a higher spatial-frequency domain than the distribution variation, we apply a wavelet method to the gain and offset image of the noise and separate out the pattern noise from the spatial variations in the temporal distribution of the scene. We compare the results to the global-constant-statistics method using a clean sequence with large artificial pattern noises. We also apply the method to a challenging CCD video sequence and a LWIR sequence to show how effective it is in reducing noise and the ghosting artifacts.

High performance optical encryption based on computational ghost imaging with QR code and compressive sensing technique

NASA Astrophysics Data System (ADS)

Zhao, Shengmei; Wang, Le; Liang, Wenqiang; Cheng, Weiwen; Gong, Longyan

2015-10-01

In this paper, we propose a high performance optical encryption (OE) scheme based on computational ghost imaging (GI) with QR code and compressive sensing (CS) technique, named QR-CGI-OE scheme. N random phase screens, generated by Alice, is a secret key and be shared with its authorized user, Bob. The information is first encoded by Alice with QR code, and the QR-coded image is then encrypted with the aid of computational ghost imaging optical system. Here, measurement results from the GI optical system's bucket detector are the encrypted information and be transmitted to Bob. With the key, Bob decrypts the encrypted information to obtain the QR-coded image with GI and CS techniques, and further recovers the information by QR decoding. The experimental and numerical simulated results show that the authorized users can recover completely the original image, whereas the eavesdroppers can not acquire any information about the image even the eavesdropping ratio (ER) is up to 60% at the given measurement times. For the proposed scheme, the number of bits sent from Alice to Bob are reduced considerably and the robustness is enhanced significantly. Meantime, the measurement times in GI system is reduced and the quality of the reconstructed QR-coded image is improved.

Evidence of ghost suppression in gluon mass scale dynamics

NASA Astrophysics Data System (ADS)

Aguilar, A. C.; Binosi, D.; Figueiredo, C. T.; Papavassiliou, J.

2018-03-01

In this work we study the impact that the ghost sector of pure Yang-Mills theories may have on the generation of a dynamical gauge boson mass scale, which hinges on the appearance of massless poles in the fundamental vertices of the theory, and the subsequent realization of the well-known Schwinger mechanism. The process responsible for the formation of such structures is itself dynamical in nature, and is governed by a set of Bethe-Salpeter type of integral equations. While in previous studies the presence of massless poles was assumed to be exclusively associated with the background-gauge three-gluon vertex, in the present analysis we allow them to appear also in the corresponding ghost-gluon vertex. The full analysis of the resulting Bethe-Salpeter system reveals that the contribution of the poles associated with the ghost-gluon vertex are particularly suppressed, their sole discernible effect being a slight modification in the running of the gluon mass scale, for momenta larger than a few GeV. In addition, we examine the behavior of the (background-gauge) ghost-gluon vertex in the limit of vanishing ghost momentum, and derive the corresponding version of Taylor's theorem. These considerations, together with a suitable Ansatz, permit us the full reconstruction of the pole sector of the two vertices involved.

A Value Chain Analysis of ghost nets in the Arafura Sea: identifying trans-boundary stakeholders, intervention points and livelihood trade-offs.

PubMed

Butler, J R A; Gunn, R; Berry, H L; Wagey, G A; Hardesty, B D; Wilcox, C

2013-07-15

Lost or discarded fishing nets are a significant component of marine debris which has trans-boundary impacts in large marine ecosystems. Such 'ghost nets' cause the by-catch of marine fauna and require retrieval from coastlines where they wash up. Identifying the causes of discarded nets and feasible intervention points requires analysis of a complex value chain and the stakeholders within it, yet no studies have attempted this. In this paper we combine Value Chain Analysis, commonly applied to understand value-adding for a commodity, with elements of Life Cycle Assessment and social network analysis to examine the drivers, stakeholders, economic, environmental and social costs and benefits in the life of a trawl net. We use the Arafura Sea as a case study, which is shared by Indonesia, Papua New Guinea and Australia, and is the focus of a Trans-boundary Diagnostic Assessment (TDA) within the Arafura-Timor Seas Ecosystem Action program (ATSEA). We follow a trawl net through four sub-systems: manufacture of webbing in South Korea, fishing and loss by an Indonesian vessel, retrieval as ghost net on the northern Australian coastline by Indigenous rangers, and disposal or re-cycling as 'GhostNet Art' by Indigenous artists. Primary stakeholders along the value chain incur economic and social benefits, and economic and environmental costs. There is an anomaly in the chain between Indonesian fishermen and Indigenous rangers, artists and communities due to the lack of market linkages between these primary stakeholders. The first 'nexus of influence' where reductions in net losses and environmental costs can be achieved is through interactions between GhostNets Australia, the World Wide Fund for Nature and the Australian Government, which can influence Indonesian fishery management institutions and fishing crews. The second nexus is via the international art market which by publicising GhostNet Art can raise awareness amongst fish consumers about the impacts of ghost nets, and hence influence Indonesian fishing companies. GhostNets Australia is a key bridging organisation in the network, linking stakeholders across scales and sub-systems. Feasible preventative interventions are discussed to rectify the anomaly in the value chain. The importance of GhostNets Australia and ATSEA in the evolving adaptive co-management and trans-boundary governance of fisheries is highlighted. However, the prevention of ghost nets will result in trade-offs in benefits for the livelihoods of primary stakeholders. The utility of the method for analysing marine debris in TDAs, and ATSEA in particular, is discussed. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Ghost beams and the energy spectra of anomalous positrons

NASA Astrophysics Data System (ADS)

Fox, J. D.; Kemper, K. W.; Cottle, P. D.

1995-05-01

It is suggested that nuclear reactions induced by medium mass projectiles, with {A}/{q} close to that of the primary beam, could explain the anomalous positron-electron peaks observed in sub-barrier collisions of very heavy nuclei. The reactions result in prominent γ-rays which convert to e +e - pairs in material near the target. Possible experiments to examine this hypothesis are suggested.

Environmental Assessment for Developing Renewable Energy Enhanced Use Lease Facilities at Robins Air Force Base

DTIC Science & Technology

2013-12-15

Blufftown is underlain by igneous and metamorphic rocks which are equivalent to those of the Georgia Piedmont. Potable and process waters are produced...Final Environmental Assessment for Developing Renewable Energy Enhanced Use Lease Facilities at Robins Air Force Base...TITLE AND SUBTITLE Final Environmental Assessment for Developing Renewable Energy Enhanced Use Lease Facilities at Robins Air Force Base 5a. CONTRACT

Environmental Assessment for Developing Renewable Energy Enhanced Use Lease Facilities at Robins Air Force Base

DTIC Science & Technology

2013-12-15

underlain by igneous and metamorphic rocks which are equivalent to those of the Georgia Piedmont. Potable and process waters are produced from the...Final Environmental Assessment for Developing Renewable Energy Enhanced Use Lease Facilities at Robins Air Force Base...RENEWABLE ENERGY ENHANCED USE LEASE FACILITIES AT ROBINS AIR FORCE BASE In accordance with the National Environmental Policy Act (NEPA) of 1969 (42 U.S

Quantum Field Energy Sensor based on the Casimir Effect

NASA Astrophysics Data System (ADS)

Ludwig, Thorsten

The Casimir effect converts vacuum fluctuations into a measurable force. Some new energy technologies aim to utilize these vacuum fluctuations in commonly used forms of energy like electricity or mechanical motion. In order to study these energy technologies it is helpful to have sensors for the energy density of vacuum fluctuations. In today's scientific instrumentation and scanning microscope technologies there are several common methods to measure sub-nano Newton forces. While the commercial atomic force microscopes (AFM) mostly work with silicon cantilevers, there are a large number of reports on the use of quartz tuning forks to get high-resolution force measurements or to create new force sensors. Both methods have certain advantages and disadvantages over the other. In this report the two methods are described and compared towards their usability for Casimir force measurements. Furthermore a design for a quantum field energy sensor based on the Casimir force measurement will be described. In addition some general considerations on extracting energy from vacuum fluctuations will be given.

A novel semiconductor-based, fully incoherent amplified spontaneous emission light source for ghost imaging

PubMed Central

Hartmann, Sébastien; Elsäßer, Wolfgang

2017-01-01

Initially, ghost imaging (GI) was demonstrated with entangled light from parametric down conversion. Later, classical light sources were introduced with the development of thermal light GI concepts. State-of-the-art classical GI light sources rely either on complex combinations of coherent light with spatially randomizing optical elements or on incoherent lamps with monochromating optics, however suffering strong losses of efficiency and directionality. Here, a broad-area superluminescent diode is proposed as a new light source for classical ghost imaging. The coherence behavior of this spectrally broadband emitting opto-electronic light source is investigated in detail. An interferometric two-photon detection technique is exploited in order to resolve the ultra-short correlation timescales. We thereby quantify the coherence time, the photon statistics as well as the number of spatial modes unveiling a complete incoherent light behavior. With a one-dimensional proof-of-principle GI experiment, we introduce these compact emitters to the field which could be beneficial for high-speed GI systems as well as for long range GI sensing in future applications. PMID:28150737

Ghost imaging based on Pearson correlation coefficients

NASA Astrophysics Data System (ADS)

Yu, Wen-Kai; Yao, Xu-Ri; Liu, Xue-Feng; Li, Long-Zhen; Zhai, Guang-Jie

2015-05-01

Correspondence imaging is a new modality of ghost imaging, which can retrieve a positive/negative image by simple conditional averaging of the reference frames that correspond to relatively large/small values of the total intensity measured at the bucket detector. Here we propose and experimentally demonstrate a more rigorous and general approach in which a ghost image is retrieved by calculating a Pearson correlation coefficient between the bucket detector intensity and the brightness at a given pixel of the reference frames, and at the next pixel, and so on. Furthermore, we theoretically provide a statistical interpretation of these two imaging phenomena, and explain how the error depends on the sample size and what kind of distribution the error obeys. According to our analysis, the image signal-to-noise ratio can be greatly improved and the sampling number reduced by means of our new method. Project supported by the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 2013YQ030595) and the National High Technology Research and Development Program of China (Grant No. 2013AA122902).

Novel Numerical Algorithms for Sensing, Discrimination, and Control

DTIC Science & Technology

1990-03-09

Boas87], and Cross WVD (XWVD) [Boas89]. A modified XWVD is especially useful because it minimizes the number of cross terms or ghosts that corrupt...between real events. If the signal strength is high, then these ghosts may even hide or cover useful returns. We do know that the cross terms can be...modified XWVD is especially useful because it minimizes the number of cross terms or ghosts that corrupt spin rate identification. Autoregressive

Living with ghosts in Lorentz invariant theories

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

Garriga, Jaume; Vilenkin, Alexander, E-mail: jaume.garriga@ub.edu, E-mail: vilenkin@cosmos.phy.tufts.edu

2013-01-01

We argue that theories with ghosts may have a long lived vacuum state even if all interactions are Lorentz preserving. In space-time dimension D = 2, we consider the tree level decay rate of the vacuum into ghosts and ordinary particles mediated by non-derivative interactions, showing that this is finite and logarithmically growing in time. For D > 2, the decay rate is divergent unless we assume that the interaction between ordinary matter and the ghost sector is soft in the UV, so that it can be described in terms of non-local form factors rather than point-like vertices. We providemore » an example of a nonlocal gravitational-strength interaction between the two sectors, which appears to satisfy all observational constraints.« less

On the uniqueness of the non-minimal matter coupling in massive gravity and bigravity

DOE PAGES

Huang, Qing-Guo; Ribeiro, Raquel H.; Xing, Yu-Hang; ...

2015-07-03

In de Rham–Gabadadze–Tolley (dRGT) massive gravity and bi-gravity, a non-minimal matter coupling involving both metrics generically reintroduces the Boulware–Deser (BD) ghost. A non-minimal matter coupling via a simple, yet specific composite metric has been proposed, which eliminates the BD ghost below the strong coupling scale. Working explicitly in the metric formulation and for arbitrary spacetime dimensions, we show that this composite metric is the unique consistent non-minimal matter coupling below the strong coupling scale, which emerges out of two diagnostics, namely, the absence of Ostrogradski ghosts in the decoupling limit and the absence of the BD ghost from matter quantummore » loop corrections.« less

Evaluation of the "Lose Your Excuse" public service advertising campaign for tweens to save energy.

PubMed

Bertrand, Jane T; Goldman, Patty; Zhivan, Natalia; Agyeman, Yaw; Barber, Erin

2011-10-01

This study evaluates the 2008-2009 "Lose your Excuse" public service advertising (PSA) campaign on energy efficiency targeting 8- to 12-year-olds, intended to increase knowledge, foster proactive attitudes, and change energy usage behaviors. Baseline and two follow-up surveys were conducted with online samples representative of the national population of households with kids with online access. Almost half (47%) of the tweens recognized at least one ad from the campaign. Ad recognition was positively associated with knowledge, proactive attitudes, and energy-saving behavior. Propensity score analysis confirmed a small but measurable and statistically significant effect on energy-saving behavior. The discussion section compares these results to public health campaigns in terms of ghost awareness, reach, and effect size.

Tsunami and ghost stories in Thailand: exploring the psychology of ghosts and religious rituals within the context of Thai Buddhism.

PubMed

Sorajjakool, Siroj

2007-01-01

The post-tsunami ghost phenomena in Thailand may be understood, in Jungian terms, as an expression of the autonomous complex of the collective psyche resulting from traumatic loss. Religious rituals, as in the context of Thai Buddhism, provide an alternative method of dealing with grief, and hence they affirm the place of religious practices in the overall psychological well-being of people from various cultural backgrounds.

Dark energy scenario consistent with GW170817 in theories beyond Horndeski gravity

NASA Astrophysics Data System (ADS)

Kase, Ryotaro; Tsujikawa, Shinji

2018-05-01

The Gleyzes-Langlois-Piazza-Vernizzi (GLPV) theories up to quartic order are the general scheme of scalar-tensor theories allowing the possibility for realizing the tensor propagation speed ct equivalent to 1 on the isotropic cosmological background. We propose a dark energy model in which the late-time cosmic acceleration occurs by a simple k-essence Lagrangian analogous to the ghost condensate with cubic and quartic Galileons in the framework of GLPV theories. We show that a wide variety of the variation of the dark energy equation of state wDE including the entry to the region wDE<-1 can be realized without violating conditions for the absence of ghosts and Laplacian instabilities. The approach to the tracker equation of state wDE=-2 during the matter era, which is disfavored by observational data, can be avoided by the existence of a quadratic k-essence Lagrangian X2. We study the evolution of nonrelativistic matter perturbations for the model ct2=1 and show that the two quantities μ and Σ , which are related to the Newtonian and weak lensing gravitational potentials respectively, are practically equivalent to each other, such that μ ≃Σ >1 . For the case in which the deviation of wDE from -1 is significant at a later cosmological epoch, the values of μ and Σ tend to be larger at low redshifts. We also find that our dark energy model can be consistent with the bounds on the deviation parameter αH from Horndeski theories arising from the modification of gravitational law inside massive objects.

Stray light calibration of the Dawn Framing Camera

NASA Astrophysics Data System (ADS)

Kovacs, Gabor; Sierks, Holger; Nathues, Andreas; Richards, Michael; Gutierrez-Marques, Pablo

2013-10-01

Sensitive imaging systems with high dynamic range onboard spacecrafts are susceptible to ghost and stray-light effects. During the design phase, the Dawn Framing Camera was laid out and optimized to minimize those unwanted, parasitic effects. However, the requirement of low distortion to the optical design and use of a front-lit focal plane array induced an additional stray light component. This paper presents the ground-based and in-flight procedures characterizing the stray-light artifacts. The in-flight test used the Sun as the stray light source, at different angles of incidence. The spacecraft was commanded to point predefined solar elongation positions, and long exposure images were recorded. The PSNIT function was calculated by the known illumination and the ground based calibration information. In the ground based calibration, several extended and point sources were used with long exposure times in dedicated imaging setups. The tests revealed that the major contribution to the stray light is coming from the ghost reflections between the focal plan array and the band pass interference filters. Various laboratory experiments and computer modeling simulations were carried out to quantify the amount of this effect, including the analysis of the diffractive reflection pattern generated by the imaging sensor. The accurate characterization of the detector reflection pattern is the key to successfully predict the intensity distribution of the ghost image. Based on the results, and the properties of the optical system, a novel correction method is applied in the image processing pipeline. The effect of this correction procedure is also demonstrated with the first images of asteroid Vesta.

Photoluminescence and gain/absorption spectra of a driven-dissipative electron-hole-photon condensate

NASA Astrophysics Data System (ADS)

Hanai, Ryo; Littlewood, Peter B.; Ohashi, Yoji

2018-06-01

We investigate theoretically nonequilibrium effects on photoluminescence and gain/absorption spectra of a driven-dissipative exciton-polariton condensate, by employing the combined Hartree-Fock-Bogoliubov theory with the generalized random phase approximation extended to the Keldysh formalism. Our calculated photoluminescence spectra is in semiquantitative agreement with experiments, where features such as a blue shift of the emission from the condensate, the appearance of the dispersionless feature of a diffusive Goldstone mode, and the suppression of the dispersive profile of the mode are obtained. We show that the nonequilibrium nature of the exciton-polariton condensate strongly suppresses the visibility of the Bogoliubov dispersion in the negative energy branch (ghost branch) in photoluminescence spectra. We also show that the trace of this branch can be captured as a hole burning effect in gain/absorption spectra. Our results indicate that the nonequilibrium nature of the exciton-polariton condensate strongly reduces quantum depletion, while a scattering channel to the ghost branch is still present.

Nonsingular bouncing cosmology: Consistency of the effective description

NASA Astrophysics Data System (ADS)

Koehn, Michael; Lehners, Jean-Luc; Ovrut, Burt

2016-05-01

We explicitly confirm that spatially flat nonsingular bouncing cosmologies make sense as effective theories. The presence of a nonsingular bounce in a spatially flat universe implies a temporary violation of the null energy condition, which can be achieved through a phase of ghost condensation. We calculate the scale of strong coupling and demonstrate that the ghost-condensate bounce remains trustworthy throughout, and that all perturbation modes within the regime of validity of the effective description remain under control. For this purpose we require the perturbed action up to third order in perturbations, which we calculate in both flat and co-moving gauge—since these two gauges allow us to highlight different physical aspects. Our conclusion is that there exist healthy descriptions of nonsingular bouncing cosmologies providing a viable resolution of the big-bang singularities in cosmological models. Our results also suggest a variant of ekpyrotic cosmology, in which entropy perturbations are generated during the contracting phase, but are only converted into curvature perturbations after the bounce.

Nonuniformity correction for an infrared focal plane array based on diamond search block matching.

PubMed

Sheng-Hui, Rong; Hui-Xin, Zhou; Han-Lin, Qin; Rui, Lai; Kun, Qian

2016-05-01

In scene-based nonuniformity correction algorithms, artificial ghosting and image blurring degrade the correction quality severely. In this paper, an improved algorithm based on the diamond search block matching algorithm and the adaptive learning rate is proposed. First, accurate transform pairs between two adjacent frames are estimated by the diamond search block matching algorithm. Then, based on the error between the corresponding transform pairs, the gradient descent algorithm is applied to update correction parameters. During the process of gradient descent, the local standard deviation and a threshold are utilized to control the learning rate to avoid the accumulation of matching error. Finally, the nonuniformity correction would be realized by a linear model with updated correction parameters. The performance of the proposed algorithm is thoroughly studied with four real infrared image sequences. Experimental results indicate that the proposed algorithm can reduce the nonuniformity with less ghosting artifacts in moving areas and can also overcome the problem of image blurring in static areas.

Sealed reticulocyte ghosts. An experimental model for the study of Fe2+ transport.

PubMed

Núñez, M T; Escobar, A; Ahumada, A; Gonzalez-Sepulveda, M

1992-06-05

Sealed right-side-out reticulocyte ghosts transported and accumulated iron offered as 59Fe(2+)-ascorbate (Km = 1.1 microM). The uptake of iron by ghosts presented the characteristics of a transporter-mediated process: it responded to osmotic challenge, the rate of transport increased when iron was present in the opposing side, and the transport rate showed the temperature dependence typical of membrane-mediated processes. The transport of iron was dependent on an associated influx of Cl- in order to keep electroneutrality. Other transition metals, such as Cu2+, Zn2+, and Co2+, inhibited the transport of Fe2+. The overall characteristics of the system make reticulocyte sealed ghosts a very useful model in determining the basic mechanisms of membrane iron transport.

Phased array ghost elimination (PAGE) for segmented SSFP imaging with interrupted steady-state.

PubMed

Kellman, Peter; Guttman, Michael A; Herzka, Daniel A; McVeigh, Elliot R

2002-12-01

Steady-state free precession (SSFP) has recently proven to be valuable for cardiac imaging due to its high signal-to-noise ratio and blood-myocardium contrast. Data acquired using ECG-triggered, segmented sequences during the approach to steady-state, or return to steady-state after interruption, may have ghost artifacts due to periodic k-space distortion. Schemes involving several preparatory RF pulses have been proposed to restore steady-state, but these consume imaging time during early systole. Alternatively, the phased-array ghost elimination (PAGE) method may be used to remove ghost artifacts from the first several frames. PAGE was demonstrated for cardiac cine SSFP imaging with interrupted steady-state using a simple alpha/2 magnetization preparation and storage scheme and a spatial tagging preparation.

Matter coupling in partially constrained vielbein formulation of massive gravity

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

Felice, Antonio De; Mukohyama, Shinji; Gümrükçüoğlu, A. Emir

2016-01-01

We consider a linear effective vielbein matter coupling without introducing the Boulware-Deser ghost in ghost-free massive gravity. This is achieved in the partially constrained vielbein formulation. We first introduce the formalism and prove the absence of ghost at all scales. As next we investigate the cosmological application of this coupling in this new formulation. We show that even if the background evolution accords with the metric formulation, the perturbations display important different features in the partially constrained vielbein formulation. We study the cosmological perturbations of the two branches of solutions separately. The tensor perturbations coincide with those in the metricmore » formulation. Concerning the vector and scalar perturbations, the requirement of absence of ghost and gradient instabilities yields slightly different allowed parameter space.« less

Matter coupling in partially constrained vielbein formulation of massive gravity

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

Felice, Antonio De; Gümrükçüoğlu, A. Emir; Heisenberg, Lavinia

2016-01-04

We consider a linear effective vielbein matter coupling without introducing the Boulware-Deser ghost in ghost-free massive gravity. This is achieved in the partially constrained vielbein formulation. We first introduce the formalism and prove the absence of ghost at all scales. As next we investigate the cosmological application of this coupling in this new formulation. We show that even if the background evolution accords with the metric formulation, the perturbations display important different features in the partially constrained vielbein formulation. We study the cosmological perturbations of the two branches of solutions separately. The tensor perturbations coincide with those in the metricmore » formulation. Concerning the vector and scalar perturbations, the requirement of absence of ghost and gradient instabilities yields slightly different allowed parameter space.« less

Entangled-photon compressive ghost imaging

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

Zerom, Petros; Chan, Kam Wai Clifford; Howell, John C.

2011-12-15

We have experimentally demonstrated high-resolution compressive ghost imaging at the single-photon level using entangled photons produced by a spontaneous parametric down-conversion source and using single-pixel detectors. For a given mean-squared error, the number of photons needed to reconstruct a two-dimensional image is found to be much smaller than that in quantum ghost imaging experiments employing a raster scan. This procedure not only shortens the data acquisition time, but also suggests a more economical use of photons for low-light-level and quantum image formation.

Ghost imaging for three-dimensional optical security

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

Chen, Wen, E-mail: elechenw@nus.edu.sg; Chen, Xudong

2013-11-25

Ghost imaging has become increasingly popular in quantum and optical application fields. Here, we report three-dimensional (3D) optical security using ghost imaging. The series of random phase-only masks are sparsified, which are further converted into particle-like distributions placed in 3D space. We show that either an optical or digital approach can be employed for the encoding. The results illustrate that a larger key space can be generated due to the application of 3D space compared with previous works.

Role of RhAG and AQP1 in NH3 and CO2 gas transport in red cell ghosts: a stopped-flow analysis.

PubMed

Ripoche, P; Goossens, D; Devuyst, O; Gane, P; Colin, Y; Verkman, A S; Cartron, J-P

2006-01-01

To clarify the potential role Rh/RhAG and AQP1 proteins in erythrocyte gas transport, NH3 and CO2 transport was measured in erythrocyte ghost membrane vesicles from rare human variants (Rh(null), CO(null),) and knockout mice (homozygous AQP1-/-, Rh-/- and Rhag-/-) exhibiting well-characterized protein defects. Transport was measured from intracellular pH (pHi) changes in a stopped-flow fluorimeter. NH3 transport was measured in chloride-free conditions with ghosts exposed to 20 mM inwardly directed gradients of gluconate salts of ammonium, hydrazine and methylammonium at 15 degrees C. Alkalinization rates of control samples were 6.5+/-0.3, 4.03+/-0.17, 0.95+/-0.08 s(-1) for each solute, respectively, but were significantly reduced for Rh(null) and CO(null) samples that are deficient in RhAG and AQP1 proteins, respectively. Alkalinization rates of Rh(null) ghosts were about 60%, 83% and 94% lower than that in control ghosts, respectively, for each solute. In CO(null) ghosts, the lack of AQP1 resulted in about 30% reduction of the alkalinization rates as compared to controls, but the transport selectivity of RhAG for the three solutes was preserved. Similar observations were made with ghosts from KO mice Rhag-/- and AQP1-/-. These results confirm the major contribution of RhAG/Rhag in the NH3 conductance of erythrocytes and suggest that the reduction of transport rates in the absence of AQP1 would be better explained by a direct or indirect effect on RhAG/Rhag-mediated transport. When ghosts were preloaded with carbonic anhydrase and exposed to a 25 mM CO2/HCO3- gradient at 6 degrees C, an extremely rapid kinetics of acidification corresponding to CO2 influx was observed. The rate constants were not significantly different between controls and human variants (125+/-6 s(-1)), or between wild-type and KO mice, suggesting no major role of RhAG or AQP1 in CO2 transport, at least in our experimental conditions.

Giant wormholes in ghost-free bigravity theory

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

Sushkov, Sergey V.; Volkov, Mikhail S., E-mail: sergey_sushkov@mail.ru, E-mail: volkov@lmpt.univ-tours.fr

2015-06-01

We study Lorentzian wormholes in the ghost-free bigravity theory described by two metrics, g and f. Wormholes can exist if only the null energy condition is violated, which happens naturally in the bigravity theory since the graviton energy-momentum tensors do not apriori fulfill any energy conditions. As a result, the field equations admit solutions describing wormholes whose throat size is typically of the order of the inverse graviton mass. Hence, they are as large as the universe, so that in principle we might all live in a giant wormhole. The wormholes can be of two different types that we callmore » W1 and W2. The W1 wormholes interpolate between the AdS spaces and have Killing horizons shielding the throat. The Fierz-Pauli graviton mass for these solutions becomes imaginary in the AdS zone, hence the gravitons behave as tachyons, but since the Breitenlohner-Freedman bound is fulfilled, there should be no tachyon instability. For the W2 wormholes the g-geometry is globally regular and in the far field zone it becomes the AdS up to subleading terms, its throat can be traversed by timelike geodesics, while the f-geometry has a completely different structure and is not geodesically complete. There is no evidence of tachyons for these solutions, although a detailed stability analysis remains an open issue. It is possible that the solutions may admit a holographic interpretation.« less

Giant wormholes in ghost-free bigravity theory

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

Sushkov, Sergey V.; Volkov, Mikhail S.; Laboratoire de Mathématiques et Physique Théorique CNRS-UMR 7350, Université de Tours, Parc de Grandmont, 37200 Tours

2015-06-09

We study Lorentzian wormholes in the ghost-free bigravity theory described by two metrics, g and f. Wormholes can exist if only the null energy condition is violated, which happens naturally in the bigravity theory since the graviton energy-momentum tensors do not apriori fulfill any energy conditions. As a result, the field equations admit solutions describing wormholes whose throat size is typically of the order of the inverse graviton mass. Hence, they are as large as the universe, so that in principle we might all live in a giant wormhole. The wormholes can be of two different types that we callmore » W1 and W2. The W1 wormholes interpolate between the AdS spaces and have Killing horizons shielding the throat. The Fierz-Pauli graviton mass for these solutions becomes imaginary in the AdS zone, hence the gravitons behave as tachyons, but since the Breitenlohner-Freedman bound is fulfilled, there should be no tachyon instability. For the W2 wormholes the g-geometry is globally regular and in the far field zone it becomes the AdS up to subleading terms, its throat can be traversed by timelike geodesics, while the f-geometry has a completely different structure and is not geodesically complete. There is no evidence of tachyons for these solutions, although a detailed stability analysis remains an open issue. It is possible that the solutions may admit a holographic interpretation.« less

Supporting Foreign Language Vocabulary Learning through Kinect-Based Gaming

ERIC Educational Resources Information Center

Urun, Mehmet Faith; Aksoy, Hasan; Comez, Rasim

2017-01-01

This study aimed to explore the effectiveness of a Kinect-based game called Tom Clancy's Ghost Recon: Future Soldier to investigate possible contributions of game-based learning in a virtual language classroom at a state university in Ankara, Turkey. A quasi-experimental design where the treatment group (N= 26) was subjected to kinect-based…

Multi-exposure high dynamic range image synthesis with camera shake correction

NASA Astrophysics Data System (ADS)

Li, Xudong; Chen, Yongfu; Jiang, Hongzhi; Zhao, Huijie

2017-10-01

Machine vision plays an important part in industrial online inspection. Owing to the nonuniform illuminance conditions and variable working distances, the captured image tends to be over-exposed or under-exposed. As a result, when processing the image such as crack inspection, the algorithm complexity and computing time increase. Multiexposure high dynamic range (HDR) image synthesis is used to improve the quality of the captured image, whose dynamic range is limited. Inevitably, camera shake will result in ghost effect, which blurs the synthesis image to some extent. However, existed exposure fusion algorithms assume that the input images are either perfectly aligned or captured in the same scene. These assumptions limit the application. At present, widely used registration based on Scale Invariant Feature Transform (SIFT) is usually time consuming. In order to rapidly obtain a high quality HDR image without ghost effect, we come up with an efficient Low Dynamic Range (LDR) images capturing approach and propose a registration method based on ORiented Brief (ORB) and histogram equalization which can eliminate the illumination differences between the LDR images. The fusion is performed after alignment. The experiment results demonstrate that the proposed method is robust to illumination changes and local geometric distortion. Comparing with other exposure fusion methods, our method is more efficient and can produce HDR images without ghost effect by registering and fusing four multi-exposure images.

Light pollution affects nesting behavior of loggerhead turtles and predation risk of nests and hatchlings.

PubMed

Silva, Elton; Marco, Adolfo; da Graça, Jesemine; Pérez, Héctor; Abella, Elena; Patino-Martinez, Juan; Martins, Samir; Almeida, Corrine

2017-08-01

The introduction of artificial light into wildlife habitats is a rapidly expanding aspect of global change, which has many negative impacts on a wide range of taxa. In this experimental study, which took place on a beach located on the island of Boa Vista (Cabo Verde), three types of artificial light were tested on nesting loggerhead sea turtles as well as on ghost crabs, which intensively predate on nests and hatchlings, to determine the effects they would produce on the behavior of both species. Over the course of 36days, female loggerheads and ghost crabs were studied under yellow, orange and red lights, with observations also being made on dark nights that served as a control treatment. During this period, the frequencies of nesting attempts, the time taken by turtles to complete each phase of the nesting process, and ghost crab abundance and behaviors were carefully recorded. 1146 loggerhead nesting attempts were observed and recorded during the experiments, and results showed a decrease in nesting attempts of at least 20% when artificial lighting was present. A significant decline in successful attempts was also observed within the central sections of the beach, which corresponded to those that received more light. This artificial lighting significantly increased the time that turtles spent on the nesting process and forced them to do more extensive beach crawls. Despite this, the presence of light had no apparent effect on the final selection of the nesting site. Yellow and orange lights significantly disrupted the sea finding behavior and turtles were often unable to orient themselves seaward under these color lights. Disoriented turtles were observed crawling in circuitous paths in front of the light source for several minutes. In addition, artificial lights had the potential to increase the number of ghost crabs present within the illuminated stretches of the beach. However, only yellow lighting produced a significant change on aggressive and prey searching behaviors. These changes in abundance and behavior could cause a greater predation on loggerhead turtle nests. Red light had no significant impact on the behavior of either species. It should be a priority to enforce preventive measures and light mitigation strategies to ensure the conservation of important loggerhead rookeries. Copyright © 2017 Elsevier B.V. All rights reserved.

Detail view of door surround, note bracket & ghost of ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail view of door surround, note bracket & ghost of (former) arched opening in the brickwork beside it - Leonard Mackall House, 1686 Thirty-Fourth Street, Northwest, Washington, District of Columbia, DC

MEAM interatomic force calculation subroutine for LAMMPS

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

Stukowski, A.

2010-10-25

Interatomic force and energy calculation subroutine tobe used with the molecular dynamics simulation code LAMMPS (Ref a.). The code evaluates the total energy and atomic forces (energy gradient) according to cubic spine-based variant (Ref b.) of the Modified Embedded Atom Method (MEAM).

50 CFR 648.125 - Possession limit.

Code of Federal Regulations, 2011 CFR

2011-10-01

... retention device designed to prevent loss of the ghost panel after the degradable materials have failed is permitted provided the device does not impair the egress design function of the ghost panel by obstructing...

50 CFR 648.125 - Scup gear restrictions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... a single non-degradable retention device designed to prevent loss of the ghost panel after the... of the ghost panel by obstructing the opening or by preventing the panel from opening at such time...

50 CFR 648.125 - Scup gear restrictions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... retention device designed to prevent loss of the ghost panel after the degradable materials have failed is permitted provided the device does not impair the egress design function of the ghost panel by obstructing...

50 CFR 648.125 - Scup gear restrictions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... retention device designed to prevent loss of the ghost panel after the degradable materials have failed is permitted provided the device does not impair the egress design function of the ghost panel by obstructing...

Ghost cells in pilomatrixoma, craniopharyngioma, and calcifying cystic odontogenic tumor: histological, immunohistochemical, and ultrastructural study.

PubMed

Rumayor, Alicia; Carlos, Román; Kirsch, Hernán Molina; de Andrade, Bruno A Benevenuto; Romañach, Mario J; de Almeida, Oslei Paes

2015-04-01

Pilomatrixoma, craniopharyngioma, and calcifying cystic odontogenic tumor are the main entities presenting ghost cells as an important histological feature, in spite their quite different clinical presentation; it seems that they share a common pathway in the formation of these cells. The aim of this study is to examine and compare the characteristics of ghost and other cells that form these lesions. Forty-three cases including 21 pilomatrixomas, 14 craniopharyngiomas, and eight calcifying cystic odontogenic tumors were evaluated by immunohistochemistry for cytokeratins, CD138, β-catenin, D2-40, Glut-1, FAS, CD10 and also by scanning electron microscopy. The CKs, CD138, β-catenin, Glut-1, FAS, and CD10 were more often expressed by transitional cells of craniopharyngioma and calcifying cystic odontogenic tumor, compared with pilomatrixoma. Basaloid cells of pilomatrixoma showed strong positivity for CD138 and CD10. Differences on expression pattern were identified in transitional and basal cells, as ghost cells were negative for most antibodies used, except by low expression for cytokeratins. By scanning electron microscopy, the morphology of ghost cells were similar in their fibrillar cytoplasm, but their pattern varied from sheets in pilomatrixoma to small clusters in craniopharyngioma and calcifying cystic odontogenic tumor. Mechanisms involved in formation of ghost cells are unknown, but probably they follow different pathways as protein expression in the basal/transitional cells was not uniform in the three tumors studied. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The viewpoint-specific failure of modern 3D displays in laparoscopic surgery.

PubMed

Sakata, Shinichiro; Grove, Philip M; Hill, Andrew; Watson, Marcus O; Stevenson, Andrew R L

2016-11-01

Surgeons conventionally assume the optimal viewing position during 3D laparoscopic surgery and may not be aware of the potential hazards to team members positioned across different suboptimal viewing positions. The first aim of this study was to map the viewing positions within a standard operating theatre where individuals may experience visual ghosting (i.e. double vision images) from crosstalk. The second aim was to characterize the standard viewing positions adopted by instrument nurses and surgical assistants during laparoscopic pelvic surgery and report the associated levels of visual ghosting and discomfort. In experiment 1, 15 participants viewed a laparoscopic 3D display from 176 different viewing positions around the screen. In experiment 2, 12 participants (randomly assigned to four clinically relevant viewing positions) viewed laparoscopic suturing in a simulation laboratory. In both experiments, we measured the intensity of visual ghosting. In experiment 2, participants also completed the Simulator Sickness Questionnaire. We mapped locations within the dimensions of a standard operating theatre at which visual ghosting may result during 3D laparoscopy. Head height relative to the bottom of the image and large horizontal eccentricities away from the surface normal were important contributors to high levels of visual ghosting. Conventional viewing positions adopted by instrument nurses yielded high levels of visual ghosting and severe discomfort. The conventional viewing positions adopted by surgical team members during laparoscopic pelvic operations are suboptimal for viewing 3D laparoscopic displays, and even short periods of viewing can yield high levels of discomfort.

Parasites (Isopoda: Epicaridea and Nematoda) from ghost and mud shrimp (Decapoda: Axiidea and Gebiidea) with descriptions of a new genus and a new species of bopyrid isopod and clarification of Pseudione Kossmann, 1881.

PubMed

Boyko, Christopher B; Williams, Jason D; Shields, Jeffrey D

2017-12-18

Ghost and mud shrimps in Axiidea and Gebiidea are hosts to parasitic epicaridean isopods, including species in Bopyridae and Ionidae. These isopods can reach high prevalence levels on their mud shrimp hosts and may strongly influence host ecology and biology. Currently, 54 species of bopyrids and eight species of ionids are known to parasitize ghost and mud shrimps. We present new taxonomic data on three species of ionids and ten species of bopyrids (nine previously described and one new to science), as well as on an undescribed species of nematode from an axiidean host. New locality and host records are given for all species. Our analysis of new material and review of museum specimens includes the description of the new species Acrobelione halimedae n. sp. from Austinogebia spinfrons (Haswell, 1881). We also provide an improved definition for the genus Pseudione Kossmann, 1881, based on morphological characters found in both sexes, and resolution of the type species, P. callianassae Kossmann, 1881. In our revision of Pseudione we erect a new genus, Robinione, and placed two species therein: R. overstreeti (Adkison Heard, 1995) and R. brattstroemi (Stuardo, Vega Cespedes, 1986). In addition, two other species are removed from Pseudione: P. compressa (Shiino, 1964) is moved to Ionella Bonnier, 1900, and P. panopei Pearse, 1947 is considered a synonym of Progebiophilus upogebiae (Hay, 1917). Bopyrid isopods represent a large, diverse taxon and our findings help clarify the taxonomy of those species found on ghost and mud shrimps.

Diffuse X-ray emission from the Dumbbell Nebula?

NASA Technical Reports Server (NTRS)

Chu, You-Hua; Kwitter, Karen B.; Kaler, James B.

1993-01-01

We have analyzed ROSAT Position Sensitive Proportional Counter pointed observations of the Dumbbell Nebula and find that the previously reported 'extended' X-ray emission is an instrumental electronic ghost image at the softest energy band. At slightly higher energy bands, the image of the Dumbbell is not very different from that of the white dwarf HZ43. We conclude that the X-ray emission of the Dumbbell Nebula comes from its central star. A blackbody model is fitted to the spectrum and the best-fit temperature of not greater than 136,000 +/- 10,000 K is in excellent agreement with the Zanstra temperatures.

Calcium pump kinetics determined in single erythrocyte ghosts by microphotolysis and confocal imaging.

PubMed

Kubitscheck, U; Pratsch, L; Passow, H; Peters, R

1995-07-01

The activity of the plasma membrane calcium pump was measured in single cells. Human red blood cell ghosts were loaded with a fluorescent calcium indicator and either caged calcium and ATP (protocol A) or caged ATP and calcium (protocol B). In a suitably modified laser scanning microscope either calcium or ATP were released by a short UV light pulse. The time-dependent fluorescence intensity of the calcium indicator was then followed in single ghosts by repetitive confocal imaging. The fluorescence intensity was converted into calcium concentration, which in turn was used to derive the kinetic parameters of the calcium pump, the Michaelis-Menten constant Km, and the maximal transport rate vmax. Km and vmax values derived in this manner were 24 +/- 14 microM and 1.0 +/- 0.6 microM/(ghost s) for protocol A, and 4 +/- 3 microM and 1.0 +/- 0.6 microM/(ghost s) for protocol B, respectively. The difference between A and B is presumably caused by calmodulin, which is inactive in the experiments with protocol A. The possibilities to extend the new method to living nucleus-containing cells transiently transfected with mutants of the plasma membrane calcium pump are discussed.

Suppressing Ghost Diffraction in E-Beam-Written Gratings

NASA Technical Reports Server (NTRS)

Wilson, Daniel; Backlund, Johan

2009-01-01

A modified scheme for electron-beam (E-beam) writing used in the fabrication of convex or concave diffraction gratings makes it possible to suppress the ghost diffraction heretofore exhibited by such gratings. Ghost diffraction is a spurious component of diffraction caused by a spurious component of grating periodicity as described below. The ghost diffraction orders appear between the main diffraction orders and are typically more intense than is the diffuse scattering from the grating. At such high intensity, ghost diffraction is the dominant source of degradation of grating performance. The pattern of a convex or concave grating is established by electron-beam writing in a resist material coating a substrate that has the desired convex or concave shape. Unfortunately, as a result of the characteristics of electrostatic deflectors used to control the electron beam, it is possible to expose only a small field - typically between 0.5 and 1.0 mm wide - at a given fixed position of the electron gun relative to the substrate. To make a grating larger than the field size, it is necessary to move the substrate to make it possible to write fields centered at different positions, so that the larger area is synthesized by "stitching" the exposed fields.

Ghost imaging with atoms

NASA Astrophysics Data System (ADS)

Khakimov, R. I.; Henson, B. M.; Shin, D. K.; Hodgman, S. S.; Dall, R. G.; Baldwin, K. G. H.; Truscott, A. G.

2016-12-01

Ghost imaging is a counter-intuitive phenomenon—first realized in quantum optics—that enables the image of a two-dimensional object (mask) to be reconstructed using the spatio-temporal properties of a beam of particles with which it never interacts. Typically, two beams of correlated photons are used: one passes through the mask to a single-pixel (bucket) detector while the spatial profile of the other is measured by a high-resolution (multi-pixel) detector. The second beam never interacts with the mask. Neither detector can reconstruct the mask independently, but temporal cross-correlation between the two beams can be used to recover a ‘ghost’ image. Here we report the realization of ghost imaging using massive particles instead of photons. In our experiment, the two beams are formed by correlated pairs of ultracold, metastable helium atoms, which originate from s-wave scattering of two colliding Bose-Einstein condensates. We use higher-order Kapitza-Dirac scattering to generate a large number of correlated atom pairs, enabling the creation of a clear ghost image with submillimetre resolution. Future extensions of our technique could lead to the realization of ghost interference, and enable tests of Einstein-Podolsky-Rosen entanglement and Bell’s inequalities with atoms.

Referenceless one-dimensional Nyquist ghost correction in multicoil single-shot spatiotemporally encoded MRI.

PubMed

Chen, Ying; Liao, Yupeng; Yuan, Lisha; Liu, Hui; Yun, Seong Dae; Shah, Nadim Joni; Chen, Zhong; Zhong, Jianhui

2017-04-01

Single-shot spatiotemporally encoded (SPEN) MRI is a novel fast imaging method capable of retaining the time efficiency of single-shot echo planar imaging (EPI) but with distortion artifacts significantly reduced. Akin to EPI, the phase inconsistencies between mismatched even and odd echoes also result in the so-called Nyquist ghosts. However, the characteristic of the SPEN signals provides the possibility of obtaining ghost-free images directly from even and odd echoes respectively, without acquiring additional reference scans. In this paper, a theoretical analysis of the Nyquist ghosts manifested in single-shot SPEN MRI is presented, a one-dimensional correction scheme is put forward capable of maintaining definition of image features without blurring when the phase inconsistency along SPEN encoding direction is negligible, and a technique is introduced for convenient and robust correction of data from multi-channel receiver coils. The effectiveness of the proposed processing pipeline is validated by a series of experiments conducted on simulation data, in vivo rats and healthy human brains. The robustness of the method is further verified by implementing distortion correction on ghost corrected data. Copyright © 2016. Published by Elsevier Inc.

Mapping of hemoglobin in erythrocytes and erythrocyte ghosts using two photon excitation fluorescence microscopy

NASA Astrophysics Data System (ADS)

Bukara, Katarina; Jovanić, Svetlana; Drvenica, Ivana T.; Stančić, Ana; Ilić, Vesna; Rabasović, Mihailo D.; Pantelić, Dejan; Jelenković, Branislav; Bugarski, Branko; Krmpot, Aleksandar J.

2017-02-01

The present study describes utilization of two photon excitation fluorescence (2PE) microscopy for visualization of the hemoglobin in human and porcine erythrocytes and their empty membranes (i.e., ghosts). High-quality, label- and fixation-free visualization of hemoglobin was achieved at excitation wavelength 730 nm by detecting visible autofluorescence. Localization in the suspension and spatial distribution (i.e., mapping) of residual hemoglobin in erythrocyte ghosts has been resolved by 2PE. Prior to the 2PE mapping, the presence of residual hemoglobin in the bulk suspension of erythrocyte ghosts was confirmed by cyanmethemoglobin assay. 2PE analysis revealed that the distribution of hemoglobin in intact erythrocytes follows the cells' shape. Two types of erythrocytes, human and porcine, characterized with discocyte and echinocyte morphology, respectively, showed significant differences in hemoglobin distribution. The 2PE images have revealed that despite an extensive washing out procedure after gradual hypotonic hemolysis, a certain amount of hemoglobin localized on the intracellular side always remains bound to the membrane and cannot be eliminated. The obtained results open the possibility to use 2PE microscopy to examine hemoglobin distribution in erythrocytes and estimate the purity level of erythrocyte ghosts in biotechnological processes.

Mean and Fluctuating Force Distribution in a Random Array of Spheres

NASA Astrophysics Data System (ADS)

Akiki, Georges; Jackson, Thomas; Balachandar, Sivaramakrishnan

2015-11-01

This study presents a numerical study of the force distribution within a cluster of mono-disperse spherical particles. A direct forcing immersed boundary method is used to calculate the forces on individual particles for a volume fraction range of [0.1, 0.4] and a Reynolds number range of [10, 625]. The overall drag is compared to several drag laws found in the literature. As for the fluctuation of the hydrodynamic streamwise force among individual particles, it is shown to have a normal distribution with a standard deviation that varies with the volume fraction only. The standard deviation remains approximately 25% of the mean streamwise force on a single sphere. The force distribution shows a good correlation between the location of two to three nearest upstream and downstream neighbors and the magnitude of the forces. A detailed analysis of the pressure and shear forces contributions calculated on a ghost sphere in the vicinity of a single particle in a uniform flow reveals a mapping of those contributions. The combination of the mapping and number of nearest neighbors leads to a first order correction of the force distribution within a cluster which can be used in Lagrangian-Eulerian techniques. We also explore the possibility of a binary force model that systematically accounts for the effect of the nearest neighbors. This work was supported by the National Science Foundation (NSF OISE-0968313) under Partnership for International Research and Education (PIRE) in Multiphase Flows at the University of Florida.

57. Historic American Buildings Survey From Motion Picture 'Ghost of ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

57. Historic American Buildings Survey From Motion Picture 'Ghost of Romance' Date of Photo: August 4, 1920 CONVENTS - Mission San Carlos Borromeo, Rio Road & Lausen Drive, Carmel-by-the-Sea, Monterey County, CA

Chiral Bosonization of Superconformal Ghosts

NASA Technical Reports Server (NTRS)

Shi, Deheng; Shen, Yang; Liu, Jinling; Xiong, Yongjian

1996-01-01

We explain the difference of the Hilbert space of the superconformal ghosts (beta,gamma) system from that of its bosonized fields phi and chi. We calculate the chiral correlation functions of phi, chi fields by inserting appropriate projectors.

The Chern-Simons Current in Systems of DNA-RNA Transcriptions

NASA Astrophysics Data System (ADS)

Capozziello, Salvatore; Pincak, Richard; Kanjamapornkul, Kabin; Saridakis, Emmanuel N.

2018-04-01

A Chern-Simons current, coming from ghost and anti-ghost fields of supersymmetry theory, can be used to define a spectrum of gene expression in new time series data where a spinor field, as alternative representation of a gene, is adopted instead of using the standard alphabet sequence of bases $A, T, C, G, U$. After a general discussion on the use of supersymmetry in biological systems, we give examples of the use of supersymmetry for living organism, discuss the codon and anti-codon ghost fields and develop an algebraic construction for the trash DNA, the DNA area which does not seem active in biological systems. As a general result, all hidden states of codon can be computed by Chern-Simons 3 forms. Finally, we plot a time series of genetic variations of viral glycoprotein gene and host T-cell receptor gene by using a gene tensor correlation network related to the Chern-Simons current. An empirical analysis of genetic shift, in host cell receptor genes with separated cluster of gene and genetic drift in viral gene, is obtained by using a tensor correlation plot over time series data derived as the empirical mode decomposition of Chern-Simons current.

Predator Diet and Trophic Position Modified with Altered Habitat Morphology

PubMed Central

Tewfik, Alexander; Bell, Susan S.; McCann, Kevin S.; Morrow, Kristina

2016-01-01

Empirical patterns that emerge from an examination of food webs over gradients of environmental variation can help to predict the implications of anthropogenic disturbance on ecosystems. This “dynamic food web approach” is rarely applied at the coastal margin where aquatic and terrestrial systems are coupled and human development activities are often concentrated. We propose a simple model of ghost crab (Ocypode quadrata) feeding that predicts changing dominant prey (Emerita talpoida, Talorchestia sp., Donax variablis) along a gradient of beach morphology and test this model using a suite of 16 beaches along the Florida, USA coast. Assessment of beaches included quantification of morphological features (width, sediments, slope), macrophyte wrack, macro-invertebrate prey and active ghost crab burrows. Stable isotope analysis of carbon (13C/12C) and nitrogen (15N/14N) and the SIAR mixing model were used to determine dietary composition of ghost crabs at each beach. The variation in habitat conditions displayed with increasing beach width was accompanied by quantifiable shifts in ghost crab diet and trophic position. Patterns of ghost crab diet were consistent with differences recorded across the beach width gradient with respect to the availability of preferred micro-habitats of principal macro-invertebrate prey. Values obtained for trophic position also suggests that the generalist ghost crab assembles and augments its diet in fundamentally different ways as habitat morphology varies across a highly dynamic ecosystem. Our results offer support for a functional response in the trophic architecture of a common food web compartment (ghost crabs, macro-invertebrate prey) across well-known beach morphologies. More importantly, our “dynamic food web approach” serves as a basis for evaluating how globally wide-spread sandy beach ecosystems should respond to a variety of anthropogenic impacts including beach grooming, beach re-nourishment, introduction of non-native or feral predators and human traffic on beaches. PMID:26824766

Orthogonal polynomial projectors for the Projector Augmented Wave (PAW) formalism.

NASA Astrophysics Data System (ADS)

Holzwarth, N. A. W.; Matthews, G. E.; Tackett, A. R.; Dunning, R. B.

1998-03-01

The PAW method for density functional electronic structure calculations developed by Blöchl(Phys. Rev. B 50), 17953 (1994) and also used by our group(Phys. Rev. B 55), 2005 (1997) has numerical advantages of a pseudopotential technique while retaining the physics of an all-electron formalism. We describe a new method for generating the necessary set of atom-centered projector and basis functions, based on choosing the projector functions from a set of orthogonal polynomials multiplied by a localizing weight factor. Numerical benefits of the new scheme result from having direct control of the shape of the projector functions and from the use of a simple repulsive local potential term to eliminate ``ghost state" problems, which can haunt calculations of this kind. We demonstrate the method by calculating the cohesive energies of CaF2 and Mo and the density of states of CaMoO4 which shows detailed agreement with LAPW results over a 66 eV range of energy including upper core, valence, and conduction band states.

f(T,T) gravity and cosmology

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

Harko, Tiberiu; Lobo, Francisco S.N.; Otalora, G.

2014-12-01

We present an extension of f(T) gravity, allowing for a general coupling of the torsion scalar T with the trace of the matter energy-momentum tensor T. The resulting f(T,T) theory is a new modified gravity, since it is different from all the existing torsion or curvature based constructions. Applied to a cosmological framework, it leads to interesting phenomenology. In particular, one can obtain a unified description of the initial inflationary phase, the subsequent non-accelerating, matter-dominated expansion, and then the transition to a late-time accelerating phase. Additionally, the effective dark energy sector can be quintessence or phantom-like, or exhibit the phantom-dividemore » crossing during the evolution. Moreover, in the far future the universe results either to a de Sitter exponential expansion, or to eternal power-law accelerated expansions. Finally, a detailed study of the scalar perturbations at the linear level reveals that f(T,T) cosmology can be free of ghosts and instabilities for a wide class of ansatzes and model parameters.« less

Parallax-Robust Surveillance Video Stitching

PubMed Central

He, Botao; Yu, Shaohua

2015-01-01

This paper presents a parallax-robust video stitching technique for timely synchronized surveillance video. An efficient two-stage video stitching procedure is proposed in this paper to build wide Field-of-View (FOV) videos for surveillance applications. In the stitching model calculation stage, we develop a layered warping algorithm to align the background scenes, which is location-dependent and turned out to be more robust to parallax than the traditional global projective warping methods. On the selective seam updating stage, we propose a change-detection based optimal seam selection approach to avert ghosting and artifacts caused by moving foregrounds. Experimental results demonstrate that our procedure can efficiently stitch multi-view videos into a wide FOV video output without ghosting and noticeable seams. PMID:26712756

Multistage Force Amplification of Piezoelectric Stacks

NASA Technical Reports Server (NTRS)

Xu, Tian-Bing (Inventor); Siochi, Emilie J. (Inventor); Zuo, Lei (Inventor); Jiang, Xiaoning (Inventor); Kang, Jin Ho (Inventor)

2015-01-01

Embodiments of the disclosure include an apparatus and methods for using a piezoelectric device, that includes an outer flextensional casing, a first cell and a last cell serially coupled to each other and coupled to the outer flextensional casing such that each cell having a flextensional cell structure and each cell receives an input force and provides an output force that is amplified based on the input force. The apparatus further includes a piezoelectric stack coupled to each cell such that the piezoelectric stack of each cell provides piezoelectric energy based on the output force for each cell. Further, the last cell receives an input force that is the output force from the first cell and the last cell provides an output apparatus force In addition, the piezoelectric energy harvested is based on the output apparatus force. Moreover, the apparatus provides displacement based on the output apparatus force.

Multispectral computational ghost imaging with multiplexed illumination

NASA Astrophysics Data System (ADS)

Huang, Jian; Shi, Dongfeng

2017-07-01

Computational ghost imaging has attracted wide attention from researchers in many fields over the last two decades. Multispectral imaging as one application of computational ghost imaging possesses spatial and spectral resolving abilities, and is very useful for surveying scenes and extracting detailed information. Existing multispectral imagers mostly utilize narrow band filters or dispersive optical devices to separate light of different wavelengths, and then use multiple bucket detectors or an array detector to record them separately. Here, we propose a novel multispectral ghost imaging method that uses one single bucket detector with multiplexed illumination to produce a colored image. The multiplexed illumination patterns are produced by three binary encoded matrices (corresponding to the red, green and blue colored information, respectively) and random patterns. The results of the simulation and experiment have verified that our method can be effective in recovering the colored object. Multispectral images are produced simultaneously by one single-pixel detector, which significantly reduces the amount of data acquisition.

Medical Ghost-Writing

PubMed Central

Langdon-Neuner, Elise

2008-01-01

Any assistance an author receives with writing a scientific article that is not acknowledged in the article is described as ghost-writing. Articles ghost-written by medical writers engaged by pharmaceutical companies who have a vested interest in the content have caused concern after scandals revealed misleading content in some articles. A key criterion of authorship in medical journals is final approval of the article submitted for publication. Authors are responsible for the content of their articles and for acknowledging any assistance they receive. Action taken by some journals and medical writer associations to encourage acknowledgement is an uphill task in the light of disinterest from the pharmaceutical industry and ignorance or similar lack of interest by those who agree to be named authors. However, acknowledgment alone is not sufficient to resolve medical ghost-writing; issues of how the acknowledgement is formulated, permission to acknowledge and access to raw data also need to be tackled. PMID:22013363

Polarizable Force Field for DNA Based on the Classical Drude Oscillator: I. Refinement Using Quantum Mechanical Base Stacking and Conformational Energetics.

PubMed

Lemkul, Justin A; MacKerell, Alexander D

2017-05-09

Empirical force fields seek to relate the configuration of a set of atoms to its energy, thus yielding the forces governing its dynamics, using classical physics rather than more expensive quantum mechanical calculations that are computationally intractable for large systems. Most force fields used to simulate biomolecular systems use fixed atomic partial charges, neglecting the influence of electronic polarization, instead making use of a mean-field approximation that may not be transferable across environments. Recent hardware and software developments make polarizable simulations feasible, and to this end, polarizable force fields represent the next generation of molecular dynamics simulation technology. In this work, we describe the refinement of a polarizable force field for DNA based on the classical Drude oscillator model by targeting quantum mechanical interaction energies and conformational energy profiles of model compounds necessary to build a complete DNA force field. The parametrization strategy employed in the present work seeks to correct weak base stacking in A- and B-DNA and the unwinding of Z-DNA observed in the previous version of the force field, called Drude-2013. Refinement of base nonbonded terms and reparametrization of dihedral terms in the glycosidic linkage, deoxyribofuranose rings, and important backbone torsions resulted in improved agreement with quantum mechanical potential energy surfaces. Notably, we expand on previous efforts by explicitly including Z-DNA conformational energetics in the refinement.

Halloween Is Coming: Ghostly Themes in the English Classroom.

ERIC Educational Resources Information Center

Mitchell, Diana; Broderick, Vincent J.

1997-01-01

Describes how an English teacher uses ghost stories in his classroom to further students' interest in and understanding of epics. Presents a short unit in which all the class work focuses on scary kinds of things. (SR)

A dummy cell immersed boundary method for incompressible turbulence simulations over dirty geometries

NASA Astrophysics Data System (ADS)

Onishi, Keiji; Tsubokura, Makoto

2016-11-01

A methodology to eliminate the manual work required for correcting the surface imperfections of computer-aided-design (CAD) data, will be proposed. Such a technique is indispensable for CFD analysis of industrial applications involving complex geometries. The CAD geometry is degenerated into cell-oriented values based on Cartesian grid. This enables the parallel pre-processing as well as the ability to handle 'dirty' CAD data that has gaps, overlaps, or sharp edges without necessitating any fixes. An arbitrary boundary representation is used with a dummy-cell technique based on immersed boundary (IB) method. To model the IB, a forcing term is directly imposed at arbitrary ghost cells by linear interpolation of the momentum. The mass conservation is satisfied in the approximate domain that covers fluid region except the wall including cells. Attempts to Satisfy mass conservation in the wall containing cells leads to pressure oscillations near the IB. The consequence of this approximation will be discussed through fundamental study of an LES based channel flow simulation, and high Reynolds number flow around a sphere. And, an analysis comparing our results with wind tunnel experiments of flow around a full-vehicle geometry will also be presented.

Ghostly Remnant of an Explosive Past

NASA Image and Video Library

2007-03-07

This enhanced image from the far-ultraviolet detector on NASA Galaxy Evolution shows a ghostly shell of ionized gas around Z Camelopardalis, a binary, or double-star system featuring a collapsed, dead star known as a white dwarf, and a companion star.

Acausality of massive gravity.

PubMed

Deser, S; Waldron, A

2013-03-15

We show, by analyzing its characteristics, that the ghost-free, 5 degree of freedom, Wess-Zumino massive gravity model admits superluminal shock wave solutions and thus is acausal. Ironically, this pathology arises from the very constraint that removes the (sixth) Boulware-Deser ghost mode.

Ghost-free, finite, fourth-order D = 3 gravity.

PubMed

Deser, S

2009-09-04

Canonical analysis of a recently proposed linear + quadratic curvature gravity model in D = 3 establishes its pure, irreducibly fourth derivative, quadratic curvature limit as both ghost-free and power-counting UV finite, thereby maximally violating standard folklore. This limit is representative of a generic class whose kinetic terms are conformally invariant in any dimension, but it is unique in simultaneously avoiding the transverse-traceless graviton ghosts plaguing D > 3 quadratic actions as well as double pole propagators in its other variables. While the two-term model is also unitary, its additional mode's second-derivative nature forfeits finiteness.

Virasoro algebra in the KN algebra; Bosonic string with fermionic ghosts on Riemann surfaces

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

Koibuchi, H.

1991-10-10

In this paper the bosonic string model with fermionic ghosts is considered in the framework of the KN algebra. The authors' attentions are paid to representations of KN algebra and a Clifford algebra of the ghosts. The authors show that a Virasoro-like algebra is obtained from KN algebra when KN algebra has certain antilinear anti-involution, and that it is isomorphic to the usual Virasoro algebra. The authors show that there is an expected relation between a central charge of this Virasoro-like algebra and an anomaly of the combined system.

The ``Ghost Shell'': Discovery of the Forward Shock from Colliding Winds about Eta Carinae

NASA Astrophysics Data System (ADS)

Dorland, B. N.; Currie, D. G.; Kaufer, A.; Bacciotti, F.

2003-01-01

We report on the newly discovered ``Ghost Shell'' around eta Carinae. We have detected a high-velocity ( ~ - 850 km /s), spatially extended, narrow emission feature lying in front of the southeast lobe of eta Carinae's homunculus. This feature has the speed of a high-velocity shock but the spectrum of a low-velocity shock. We propose that the Ghost Shell is the forward shock between the fast stellar wind of the great eruption of 1842 and the older, slow, massive wind. This discovery is described in more detail in Currie, Dorland, & Kaufer (2002).

External location of sites on pig erythrocyte membranes that bind nitrobenzylthioinosine

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

Agbanyo, F.R.; Cass, C.E.; Paterson, A.R.

1988-03-01

Nucleoside transport in erythrocytes of various species is inhibited by the binding of nitrobenzylthioinosine (NBMPR) to high affinity sites associated with nucleoside transport elements of the plasma membrane. The present study examined binding of (/sup 3/H)NBMPR to unsealed ghosts and to sealed right-side-out vesicles (ROVs) and inside-out vesicles (IOVs) prepared from pig erythrocytes. Kd values for NBMPR dissociation from the ligand-site complex in unsealed ghosts, ROVs and IOVs were similar (1.6-2.4 nM), and Bmax values (mean +/- SD) were, respectively, 22.2 +/- 5.5, 25.8 +/- 6.4, and 37.3 +/- 4.0 molecules/fg of protein, reflecting differences in the protein content ofmore » the membrane preparations. When temperatures were decreased from 22 degrees to 4 degrees, NBMPR binding to erythrocyte membrane preparations was reduced in IOVs relative to that in unsealed ghosts and ROVs. At 22 degrees, the association of NBMPR molecules with IOVs was slower than with ROVs and unsealed ghosts, differences that were virtually eliminated by permeabilization of the membrane preparations with saponin. Thus, the binding sites were more accessible to external NBMPR in sealed ROVs and unsealed ghosts than in sealed IOVs, indicating that the NBMPR sites are located on the extracellular aspect of the membrane.« less

Phase-Sensitive Coherence and the Classical-Quantum Boundary in Ghost Imaging

NASA Technical Reports Server (NTRS)

Erkmen, Baris I.; Hardy, Nicholas D.; Venkatraman, Dheera; Wong, Franco N. C.; Shapiro, Jeffrey H.

2011-01-01

The theory of partial coherence has a long and storied history in classical statistical optics. the vast majority of this work addresses fields that are statistically stationary in time, hence their complex envelopes only have phase-insensitive correlations. The quantum optics of squeezed-state generation, however, depends on nonlinear interactions producing baseband field operators with phase-insensitive and phase-sensitive correlations. Utilizing quantum light to enhance imaging has been a topic of considerable current interest, much of it involving biphotons, i.e., streams of entangled-photon pairs. Biphotons have been employed for quantum versions of optical coherence tomography, ghost imaging, holography, and lithography. However, their seemingly quantum features have been mimicked with classical-sate light, questioning wherein lies the classical-quantum boundary. We have shown, for the case of Gaussian-state light, that this boundary is intimately connected to the theory of phase-sensitive partial coherence. Here we present that theory, contrasting it with the familiar case of phase-insensitive partial coherence, and use it to elucidate the classical-quantum boundary of ghost imaging. We show, both theoretically and experimentally, that classical phase-sensitive light produces ghost imaging most closely mimicking those obtained in biphotons, and we derived the spatial resolution, image contrast, and signal-to-noise ratio of a standoff-sensing ghost imager, taking into account target-induced speckle.

The effect of EDTA, cations, and various buffers on the morphology of erythrocyte membranes: an electron-microscopic study.

PubMed

Pinteric, L; Manery, J F; Chaudry, I H; Madapallimattam, G

1975-05-01

Membranes of human erythrocytes were prepared by stepwise osmotic hemolysis in Ca2+-free solutions. Examination with the electron microscope after negative staining showed some short, conelike protuberances on the surface of about 20 percent of the ghosts, while 80 percent were round, intact spheres. After Ca2+ treatment, all membranes were round and intact. After exposure to ethylenediaminetetraacetic acid (EDTA) (1.0 mM, pH 7.4), the entire ghost surface was covered with long, thin extrusions called stromalytic forms (about 460 per cell). Their sizes, shapes, and fine structure are described. Exposure to ionic calcium (1.4 times 10-minus 4M) abolished the EDTA-induced stromalytic forms. A second exposure to EDTA reversed this Ca2+ effect. ATP, like EDTA, produced stromalytic forms. EDTA-induced stromalytic forms were also abolished by Zn2+, La3+, and Nd3+ at concentrations of 1-5 times 10-minus 4 M. Mg2+ at 10-minus 2 M was ineffective. Ghosts were prepared by graded lysis in various buffers. Those prepared in phosphate were the most stable and provided consistent EDTA effects and Ca2+ reversal. Ghosts in Tris-HCl showed breakdown unless salt was added. Moderately satisfactory ghosts were also obtained in Hepes-NaOH buffer and salt.

Supersymmetric Galileons

DOE PAGES

Khoury, Justin; Lehners, Jean -Luc; Ovrut, Burt A.

2011-08-15

Galileon theories are of considerable interest since they allow for stable violations of the null energy condition. Since such violations could have occurred during a high-energy regime in the history of our universe, we are motivated to study supersymmetric extensions of these theories. This is carried out in this paper, where we construct generic classes of N = 1 supersymmetric Galileon Lagrangians. They are shown to admit non-equivalent stress-energy tensors and, hence, vacua manifesting differing conditions for violating the null energy condition. The temporal and spatial fluctuations of all component fields of the supermultiplet are analyzed and shown to bemore » stable on a large number of such backgrounds. In the process, we uncover a surprising connection between conformal Galileon and ghost condensate theories, allowing for a deeper understanding of both types of theories.« less

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

Mörtsell, E., E-mail: edvard@fysik.su.se

The bimetric generalization of general relativity has been proven to be able to give an accelerated background expansion consistent with observations. Apart from the energy densities coupling to one or both of the metrics, the expansion will depend on the cosmological constant contribution to each of them, as well as the three parameters describing the interaction between the two metrics. Even for fixed values of these parameters can several possible solutions, so called branches, exist. Different branches can give similar background expansion histories for the observable metric, but may have different properties regarding, for example, the existence of ghosts andmore » the rate of structure growth. In this paper, we outline a method to find viable solution branches for arbitrary parameter values. We show how possible expansion histories in bimetric gravity can be inferred qualitatively, by picturing the ratio of the scale factors of the two metrics as the spatial coordinate of a particle rolling along a frictionless track. A particularly interesting example discussed is a specific set of parameter values, where a cosmological dark matter background is mimicked without introducing ghost modes into the theory.« less

Cosmological histories in bimetric gravity: a graphical approach

NASA Astrophysics Data System (ADS)

Mörtsell, E.

2017-02-01

The bimetric generalization of general relativity has been proven to be able to give an accelerated background expansion consistent with observations. Apart from the energy densities coupling to one or both of the metrics, the expansion will depend on the cosmological constant contribution to each of them, as well as the three parameters describing the interaction between the two metrics. Even for fixed values of these parameters can several possible solutions, so called branches, exist. Different branches can give similar background expansion histories for the observable metric, but may have different properties regarding, for example, the existence of ghosts and the rate of structure growth. In this paper, we outline a method to find viable solution branches for arbitrary parameter values. We show how possible expansion histories in bimetric gravity can be inferred qualitatively, by picturing the ratio of the scale factors of the two metrics as the spatial coordinate of a particle rolling along a frictionless track. A particularly interesting example discussed is a specific set of parameter values, where a cosmological dark matter background is mimicked without introducing ghost modes into the theory.

NASA Satellite Scares Up An Eerie Image of Haunted Lakes and Ghost Ships

NASA Image and Video Library

2011-10-29

NASA Terra satellite presents this false color view of portions of Wisconsin and Michigan, including Devil Lake, Druid Lake, Ghost Lake, Spider Lake, and Witches Lake in Wisconsin; and Bat Lake, Corpse Pond and Witch Lake in Michigan.

AXAF-I ghost ray study: On orbit case

NASA Technical Reports Server (NTRS)

Gaetz, T. J.

1993-01-01

The problem of baffles for control of singly reflected (and nonreflected) ghost rays is considered. The theory of baffle design for Wolter Type I grazing incidence optics is reviewed, and a set of sample baffle parameters is obtained subject to the assumptions of nominal mirror figures and perfect manufacture and alignment of baffles. It is found that baffles forward of the optics (in the thermal precollimator) and between the mirror elements (at the CAP) are sufficient to allow the simultaneous ghost image and vignetting requirements to be satisfied for HRMA shells P1H1, P3H3, and P4H4. However, these baffles are not sufficient for the innermost shell P6H6; at best the requirements are slightly violated and there is no margin for tolerances. The addition of a baffle interior to the P6 space at an axial station about one third of the way forward from the aft end of the paraboloid will allow the ghost ray and vignetting requirements to be met. The minimum ghost ray angles and the vignetting angles are sensitive functions of the baffle positions and radii; tolerances of considerably better than 1 mm will be required. The sensitivities are coupled and correlated; further investigations should be undertaken in order to obtain baffle parameters which, combined with likely achievable tolerances, will minimize the risk of the vignetting/ghost ray requirements not being met. The lightweight carbon-epoxy composite used for thermal baffles has insufficient X-ray opacity to be a suitable material for construction of the controlling X-ray baffles; further study is needed to determine an appropriate material and to investigate its thermal and mechanical implications.

Evaluation of immunogenicity and protective efficacy of adjuvanted Salmonella Typhimurium ghost vaccine against salmonellosis in chickens.

PubMed

Jawale, Chetan V; Lee, John Hwa

2016-09-01

Salmonella Typhimurium, a non-host-adapted Gram-negative intracellular pathogen, is capable of infecting a variety of animal hosts and humans. This study utilized the prime-booster immunization strategy using Salmonella Typhimurium-LTB (S. Typhimurium-LTB) ghost with the aim of inducing a robust immune response for the prevention of avian salmonellosis. In addition, the effect of Montanide(TM) ISA 70VG adjuvant on S. Typhimurium-LTB ghost vaccination was investigated. A total of 75 chickens were divided into three groups (n=25) for intramuscular immunization: group A (non-immunized control injected with sterile PBS), group B (immunized with S. Typhimurium-LTB ghost), and group C (immunized with S. Typhimurium-LTB ghost plus Montanide(TM) ISA70VG adjuvant). Compared with group A, the immunized chickens (groups B and C) exhibited increased titers of antigen specific plasma IgG and intestinal secretory IgA antibodies. In addition, group C showed enhanced induction of the humoral immune response compared to group B. The populations of splenic CD3+CD4+ and CD3+CD8+ T-cells increased significantly in both immunized groups. In addition, increased mRNA expression of the Th1 cytokines, IFN-γ, and IL-2 were observed in S. Typhimurium antigen-stimulated peripheral blood mononuclear cells from groups B and C chickens. Chickens from both vaccinated groups showed significant protection against virulent S. Typhimurium oral challenge compared to non-vaccinated chickens and a lower challenge strain count was recovered from the internal organs of group C. Injection of S. Typhimurium-LTB ghost with or without Montanide(TM) ISA70VG adjuvant is capable of inducing protective immunity against the virulent S. Typhimurium infection in chickens.

High frame-rate computational ghost imaging system using an optical fiber phased array and a low-pixel APD array.

PubMed

Liu, Chunbo; Chen, Jingqiu; Liu, Jiaxin; Han, Xiang'e

2018-04-16

To obtain a high imaging frame rate, a computational ghost imaging system scheme is proposed based on optical fiber phased array (OFPA). Through high-speed electro-optic modulators, the randomly modulated OFPA can provide much faster speckle projection, which can be precomputed according to the geometry of the fiber array and the known phases for modulation. Receiving the signal light with a low-pixel APD array can effectively decrease the requirement on sampling quantity and computation complexity owing to the reduced data dimensionality while avoiding the image aliasing due to the spatial periodicity of the speckles. The results of analysis and simulation show that the frame rate of the proposed imaging system can be significantly improved compared with traditional systems.

Reducing uncertainties in energy dissipation measurements in atomic force spectroscopy of molecular networks and cell-adhesion studies.

PubMed

Biswas, Soma; Leitao, Samuel; Theillaud, Quentin; Erickson, Blake W; Fantner, Georg E

2018-06-20

Atomic force microscope (AFM) based single molecule force spectroscopy (SMFS) is a valuable tool in biophysics to investigate the ligand-receptor interactions, cell adhesion and cell mechanics. However, the force spectroscopy data analysis needs to be done carefully to extract the required quantitative parameters correctly. Especially the large number of molecules, commonly involved in complex networks formation; leads to very complicated force spectroscopy curves. One therefore, generally characterizes the total dissipated energy over a whole pulling cycle, as it is difficult to decompose the complex force curves into individual single molecule events. However, calculating the energy dissipation directly from the transformed force spectroscopy curves can lead to a significant over-estimation of the dissipated energy during a pulling experiment. The over-estimation of dissipated energy arises from the finite stiffness of the cantilever used for AFM based SMFS. Although this error can be significant, it is generally not compensated for. This can lead to significant misinterpretation of the energy dissipation (up to the order of 30%). In this paper, we show how in complex SMFS the excess dissipated energy caused by the stiffness of the cantilever can be identified and corrected using a high throughput algorithm. This algorithm is then applied to experimental results from molecular networks and cell-adhesion measurements to quantify the improvement in the estimation of the total energy dissipation.

Witches, Ghosts, and Other Apparitions (Rainbow Teachers, Rainbow Students).

ERIC Educational Resources Information Center

Cruz, MaryCarmen; Duff, Ogle Burks

1996-01-01

Describes a number of ghost stories from American cultures, all of which, despite their different origins, seek to stimulate horror, escapism, and fantastic pleasure. Suggests that the stories may be used to improve reading and writing and incorporate "rainbow" themes in the classroom. (TB)

SU(3) Landau gauge gluon and ghost propagators using the logarithmic lattice gluon field definition

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

Ilgenfritz, Ernst-Michael; Humboldt-Universitaet zu Berlin, Institut fuer Physik, 12489 Berlin; Menz, Christoph

2011-03-01

We study the Landau gauge gluon and ghost propagators of SU(3) gauge theory, employing the logarithmic definition for the lattice gluon fields and implementing the corresponding form of the Faddeev-Popov matrix. This is necessary in order to consistently compare lattice data for the bare propagators with that of higher-loop numerical stochastic perturbation theory. In this paper we provide such a comparison, and introduce what is needed for an efficient lattice study. When comparing our data for the logarithmic definition to that of the standard lattice Landau gauge we clearly see the propagators to be multiplicatively related. The data of themore » associated ghost-gluon coupling matches up almost completely. For the explored lattice spacings and sizes discretization artifacts, finite size, and Gribov-copy effects are small. At weak coupling and large momentum, the bare propagators and the ghost-gluon coupling are seen to be approached by those of higher-order numerical stochastic perturbation theory.« less

A self-synchronized high speed computational ghost imaging system: A leap towards dynamic capturing

NASA Astrophysics Data System (ADS)

Suo, Jinli; Bian, Liheng; Xiao, Yudong; Wang, Yongjin; Zhang, Lei; Dai, Qionghai

2015-11-01

High quality computational ghost imaging needs to acquire a large number of correlated measurements between the to-be-imaged scene and different reference patterns, thus ultra-high speed data acquisition is of crucial importance in real applications. To raise the acquisition efficiency, this paper reports a high speed computational ghost imaging system using a 20 kHz spatial light modulator together with a 2 MHz photodiode. Technically, the synchronization between such high frequency illumination and bucket detector needs nanosecond trigger precision, so the development of synchronization module is quite challenging. To handle this problem, we propose a simple and effective computational self-synchronization scheme by building a general mathematical model and introducing a high precision synchronization technique. The resulted efficiency is around 14 times faster than state-of-the-arts, and takes an important step towards ghost imaging of dynamic scenes. Besides, the proposed scheme is a general approach with high flexibility for readily incorporating other illuminators and detectors.

Sulfur and iron accumulation in three marine-archaeological shipwrecks in the Baltic Sea: The Ghost, the Crown and the Sword

NASA Astrophysics Data System (ADS)

Fors, Yvonne; Grudd, Håkan; Rindby, Anders; Jalilehvand, Farideh; Sandström, Magnus; Cato, Ingemar; Bornmalm, Lennart

2014-02-01

Sulfur and iron concentrations in wood from three 17th century shipwrecks in the Baltic Sea, the Ghost wreck, the Crown and the Sword, were obtained by X-ray fluorescence (XRF) scanning. In near anaerobic environments symbiotic microorganisms degrade waterlogged wood, reduce sulfate and promote accumulation of low-valent sulfur compounds, as previously found for the famous wrecks of the Vasa and Mary Rose. Sulfur K-edge X-ray absorption near-edge structure (XANES) analyses of Ghost wreck wood show that organic thiols and disulfides dominate, together with elemental sulfur probably generated by sulfur-oxidizing Beggiatoa bacteria. Iron sulfides were not detected, consistent with the relatively low iron concentration in the wood. In a museum climate with high atmospheric humidity oxidation processes, especially of iron sulfides formed in the presence of corroding iron, may induce post-conservation wood degradation. Subject to more general confirmation by further analyses no severe conservation concerns are expected for the Ghost wreck wood.

Schwinger-Keldysh superspace in quantum mechanics

NASA Astrophysics Data System (ADS)

Geracie, Michael; Haehl, Felix M.; Loganayagam, R.; Narayan, Prithvi; Ramirez, David M.; Rangamani, Mukund

2018-05-01

We examine, in a quantum mechanical setting, the Hilbert space representation of the Becchi, Rouet, Stora, and Tyutin (BRST) symmetry associated with Schwinger-Keldysh path integrals. This structure had been postulated to encode important constraints on influence functionals in coarse-grained systems with dissipation, or in open quantum systems. Operationally, this entails uplifting the standard Schwinger-Keldysh two-copy formalism into superspace by appending BRST ghost degrees of freedom. These statements were previously argued at the level of the correlation functions. We provide herein a complementary perspective by working out the Hilbert space structure explicitly. Our analysis clarifies two crucial issues not evident in earlier works: first, certain background ghost insertions necessary to reproduce the correct Schwinger-Keldysh correlators arise naturally, and, second, the Schwinger-Keldysh difference operators are systematically dressed by the ghost bilinears, which turn out to be necessary to give rise to a consistent operator algebra. We also elaborate on the structure of the final state (which is BRST closed) and the future boundary condition of the ghost fields.

Understanding Nanocalcification: A Role Suggested for Crystal Ghosts

PubMed Central

Bonucci, Ermanno

2014-01-01

The present survey deals with the initial stage of the calcification process in bone and other hard tissues, with special reference to the organic-inorganic relationship and the transformation that the early inorganic particles undergo as the process moves towards completion. Electron microscope studies clearly exclude the possibility that these particles might be crystalline structures, as often believed, by showing that they are, instead, organic-inorganic hybrids, each comprising a filamentous organic component (the crystal ghost) made up of acidic proteins. The hypothesis is suggested that the crystal ghosts bind and stabilize amorphous calcium phosphate and that their subsequent degradation allows the calcium phosphate, once released, to acquire a hydroxyapatite, crystal-like organization. A conclusive view of the mechanism of biological calcification cannot yet be proposed; even so, however, the role of crystal ghosts as a template of the structures usually called “crystallites” is a concept that has gathered increasing support and can no longer be disregarded. PMID:25056630

Ghost and guest authors: you can't always trust who you read.

PubMed

Schofferman, Jerome; Wetzel, F Todd; Bono, Christopher

2015-03-01

Clinicians and educators rely on the published medical information. They trust that original research and narrative or systematic reviews are reliable and the authorship is transparent, but this is not always the case. Disclosure of conflicts of interest by authors is required by most journals, disclosure will not detect ghost or guest authorship. Ghosting or guesting is of more than academic interests because it can directly or indirectly affect patient care. Therefore it is important for readers to be aware of this issue, and to be alert to suggestions that particular works may be at increased risk for ghost or guest authors. It is important to take a proactive stance against these practices. Industry, universities, research centers, and professional medical associations should be clear and unequivocal in condeming these practices. Processes need to be in place to investigate and, if need be, deal with violations. Clearly, we must all participate in this endeavor for professional, ethical, and most importantly, best patient care reasons.

The importance of witnessed agency in chimpanzee social learning of tool use☆

PubMed Central

Hopper, Lydia M.; Lambeth, Susan P.; Schapiro, Steven J.; Whiten, Andrew

2015-01-01

Social learning refers to individuals learning from others, including information gained through indirect social influences, such as the results of others’ actions and changes in the physical environment. One method to determine the relative influence of these varieties of information is the ‘ghost display’, in which no model is involved, but subjects can watch the results that a model would produce. Previous research has shown mixed success by chimpanzees (Pan troglodytes) learning from ghost displays, with some studies suggesting learning only in relatively simple tasks. To explore whether the failure of chimpanzees to learn from a ghost display may be due to neophobia when tested singly or a requirement for more detailed information for complex tasks, we presented ghost displays of a tool-use task to chimpanzees in their home social groups. Previous tests have revealed that chimpanzees are unable to easily solve this tool-use task asocially, or learn from ghost displays when tested singly, but can learn after observing conspecifics in a group setting. In the present study, despite being tested in a group situation, chimpanzees still showed no success in solving the task via trial-and-error learning, in a baseline condition, nor in learning the task from the ghost display. Simply being in the presence of their group mates and being shown the affordances of the task was not sufficient to encourage learning. Following this, in an escalating series of tests, we examined the chimpanzees’ ability to learn from a demonstration by models with agency: (1) a human; (2) video footage of a chimpanzee; (3) a live chimpanzee model. In the first two of these ‘social’ conditions, subjects showed limited success. By the end of the final open diffusion phase, which was run to determine whether this new behavior would be transmitted among the group after seeing a successful chimpanzee use the task, 83% of chimpanzees were now successful. This confirmed a marked overall effect of observing animate conspecific modeling, in contrast to the ghost condition. This article is part of a Special Issue entitled: insert SI title. PMID:25444770

The importance of witnessed agency in chimpanzee social learning of tool use.

PubMed

Hopper, Lydia M; Lambeth, Susan P; Schapiro, Steven J; Whiten, Andrew

2015-03-01

Social learning refers to individuals learning from others, including information gained through indirect social influences, such as the results of others' actions and changes in the physical environment. One method to determine the relative influence of these varieties of information is the 'ghost display', in which no model is involved, but subjects can watch the results that a model would produce. Previous research has shown mixed success by chimpanzees (Pan troglodytes) learning from ghost displays, with some studies suggesting learning only in relatively simple tasks. To explore whether the failure of chimpanzees to learn from a ghost display may be due to neophobia when tested singly or a requirement for more detailed information for complex tasks, we presented ghost displays of a tool-use task to chimpanzees in their home social groups. Previous tests have revealed that chimpanzees are unable to easily solve this tool-use task asocially, or learn from ghost displays when tested singly, but can learn after observing conspecifics in a group setting. In the present study, despite being tested in a group situation, chimpanzees still showed no success in solving the task via trial-and-error learning, in a baseline condition, nor in learning the task from the ghost display. Simply being in the presence of their group mates and being shown the affordances of the task was not sufficient to encourage learning. Following this, in an escalating series of tests, we examined the chimpanzees' ability to learn from a demonstration by models with agency: (1) a human; (2) video footage of a chimpanzee; (3) a live chimpanzee model. In the first two of these 'social' conditions, subjects showed limited success. By the end of the final open diffusion phase, which was run to determine whether this new behavior would be transmitted among the group after seeing a successful chimpanzee use the task, 83% of chimpanzees were now successful. This confirmed a marked overall effect of observing animate conspecific modeling, in contrast to the ghost condition. This article is part of a Special Issue entitled: insert SI title. Copyright © 2014 Elsevier B.V. All rights reserved.

Structural and mechanical heterogeneity of the erythrocyte membrane reveals hallmarks of membrane stability.

PubMed

Picas, Laura; Rico, Félix; Deforet, Maxime; Scheuring, Simon

2013-02-26

The erythrocyte membrane, a metabolically regulated active structure that comprises lipid molecules, junctional complexes, and the spectrin network, enables the cell to undergo large passive deformations when passing through the microvascular system. Here we use atomic force microscopy (AFM) imaging and quantitative mechanical mapping at nanometer resolution to correlate structure and mechanics of key components of the erythrocyte membrane, crucial for cell integrity and function. Our data reveal structural and mechanical heterogeneity modulated by the metabolic state at unprecedented nanometer resolution. ATP-depletion, reducing skeletal junction phosphorylation in RBC cells, leads to membrane stiffening. Analysis of ghosts and shear-force opened erythrocytes show that, in the absence of cytosolic kinases, spectrin phosphorylation results in membrane stiffening at the extracellular face and a reduced junction remodeling in response to loading forces. Topography and mechanical mapping of single components at the cytoplasmic face reveal that, surprisingly, spectrin phosphorylation by ATP softens individual filaments. Our findings suggest that, besides the mechanical signature of each component, the RBC membrane mechanics is regulated by the metabolic state and the assembly of its structural elements.

Dose-response characteristics of an amorphous silicon EPID.

PubMed

Winkler, Peter; Hefner, Alfred; Georg, Dietmar

2005-10-01

Electronic portal imaging devices (EPIDs) were originally developed for the purpose of patient setup verification. Nowadays, they are increasingly used as dosimeters (e.g., for IMRT verification and linac-specific QA). A prerequisite for any clinical dosimetric application is a detailed understanding of the detector's dose-response behavior. The aim of this study is to investigate the dosimetric properties of an amorphous silicon EPID (Elekta IVIEWGT) with respect to three photon beam qualities: 6, 10, and 25 MV. The EPID showed an excellent temporal stability on short term as well as on long term scales. The stability throughout the day was strongly influenced by warming up, which took several hours and affected EPID response by 2.5%. Ghosting effects increased the sensitivity of the EPID. They became more pronounced with decreasing time intervals between two exposures as well as with increasing dose. Due to ghosting, changes in pixel sensitivity amounted up to 16% (locally) for the 25 MV photon beam. It was observed that the response characteristics of our EPID depended on dose as well as on dose rate. Doubling the dose rate increased the EPID sensitivity by 1.5%. This behavior was successfully attributed to a dose per frame effect, i.e., a nonlinear relationship between the EPID signal and the dose which was delivered to the panel between two successive readouts. The sensitivity was found to vary up to 10% in the range of 1 to 1000 monitor units. This variation was governed by two independent effects. For low doses, the EPID signal was reduced due to the linac's changing dose rate during startup. Furthermore, the detector reading was influenced by intrabeam variations of EPID sensitivity, namely, an increase of detector response during uniform exposure. For the beam qualities which were used, the response characteristics of the EPID did not depend on energy. Differences in relative dose-response curves resulted from energy dependent temporal output characteristics of the accelerator. If ghosting is prevented from affecting the results and all dose-response effects are properly corrected for, the EPID signal becomes independent of dose rate, dose, and exposure time.

Ghostly Halos in Dwarf Galaxies: a probe of star formation in the Early Universe

NASA Astrophysics Data System (ADS)

Kang, Hoyoung; Ricotti, Massimo

2016-01-01

We carry out numerical simulations to characterize the size, stellar mass, and stellar mass surface density of extended stellar halos in dwarf galaxies as a function of dark matter halo mass. We expect that for galaxies smaller than a critical value, these ghostly halos will not exist because the smaller galactic subunits that build it up, do not form any stars. The detection of ghostly halos around isolated dwarf galaxies is a sensitive test of the efficiency of star formation in the first galaxies and of whether ultra-faint dwarf satellites of the Milky Way are fossils of the first galaxies.

Ghost free systems with coexisting bosons and fermions

NASA Astrophysics Data System (ADS)

Kimura, Rampei; Sakakihara, Yuki; Yamaguchi, Masahide

2017-08-01

We study the coexistence system of both bosonic and fermionic degrees of freedom. Even if a Lagrangian does not include higher derivatives, fermionic ghosts exist. For a Lagrangian with up to first derivatives, we find the fermionic ghost free condition in Hamiltonian analysis, which is found to be the same as requiring that the equations of motion of fermions be first order in Lagrangian formulation. When fermionic degrees of freedom are present, the uniqueness of time evolution is not guaranteed a priori because of the Grassmann property. We confirm that the additional condition, which is introduced to close Hamiltonian analysis, also ensures the uniqueness of the time evolution of the system.

Exorcising the Ostrogradsky ghost in coupled systems

NASA Astrophysics Data System (ADS)

Klein, Remko; Roest, Diederik

2016-07-01

The Ostrogradsky theorem implies that higher-derivative terms of a single mechanical variable are either trivial or lead to additional, ghost-like degrees of freedom. In this letter we systematically investigate how the introduction of additional variables can remedy this situation. Employing a Lagrangian analysis, we identify conditions on the La-grangian to ensure the existence of primary and secondary constraints that together imply the absence of Ostrogradsky ghosts. We also show the implications of these conditions for the structure of the equations of motion as well as possible redefinitions of the variables. We discuss applications to analogous higher-derivative field theories such as multi-Galileons and beyond Horndeski.

Interlayer Crosstalk Reduction by Controlling Backward Reflectivity in Multilayer Optical Discs

NASA Astrophysics Data System (ADS)

Ushiyama, Junko; Miyauchi, Yasushi; Shintani, Toshimichi; Sugiyama, Toshinori; Miyamoto, Harukazu; Kurokawa, Takahiro

2008-05-01

A method is proposed to reduce interlayer crosstalk in multilayer optical discs by controlling backward reflectivity of information layers, which can lead to wider tolerances of disc fabrication accuracy. Reduction of the backward reflectivity reduces the signal from the ghost spot even if thicknesses of spacer layers are equal. Experimental results showed that the ratio of the signals obtained by the readout spot and the ghost spot is less by about one order for a disc with controlled backward reflectivity than for a conventional disc. A rough estimate of the crosstalk caused by the ghost spot agrees qualitatively with the experimental results.

Chasing the ghost particle: The long and winding road toward the detection of solar neutrinos

NASA Astrophysics Data System (ADS)

Leone, Matteo; Robotti, Nadia

2015-10-01

One of the great achievements of neutrino physics was the discovery of solar neutrinos in 1968 through the Homestake underground experiment. This experiment exploited a radiochemical method based on the chlorine-argon process of inverse beta decay suggested by Bruno Pontecorvo in 1946 during his work in the classified Canadian nuclear project. In this paper, we study the emergence of the method. We focus on the role played by the problematic status of the neutrino and its antiparticle in its field of application and the influence exerted by the contemporary models of energy production in the sun. We also provide evidence that a first germ of this radiochemical method, in the form of a chlorine-sulfur process, was suggested in a paper published by Richard Crane in late 1930s.

The Day the Children Found a Ghost.

ERIC Educational Resources Information Center

Kapur, Madhavi

1993-01-01

The headmistress of an English school in India explains how a group of eight year olds responded to finding a "ghost" in a tree in the school courtyard. First-hand observation, exploration, and hard evidence led students to a more objective interpretation of the elusive tree spirit. (MLH)

Ambient betatron motion and its excitation by ``ghost lines'' in Tevatron

DOE PAGES

Shiltsev, Vladimir; Stancari, Giulio; Valishev, Alexander

2011-08-02

Transverse betatron motion of the Tevatron proton beam is measured and analysed. It is shown that the motion is coherent and excited by external sources of unknown origins. The observations of the time varying “ghost lines“ in the betatron spectra are reported.

2. Building 22 south elevation oblique. Ghost of Building 22A ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. Building 22 south elevation oblique. Ghost of Building 22A visible on south elevation. South elevation of Building 22A in foreground. View looking NW. - John & James Dobson Carpet Mill (West Parcel), Building No. 22, 4041-4055 Ridge Avenue, Philadelphia, Philadelphia County, PA

Training 101: Four Ghosts and Two Heads.

ERIC Educational Resources Information Center

Petrini, Catherine M., Ed.; And Others

1993-01-01

Laus and Champagne offer clues for identifying training room "ghosts" (participants' past experiences, histories, demands, and needs) and describe how to get rid of them. Plutschak and Luke discuss the benefits of team training and suggest five rules to heed when training by the buddy system. (JOW)

Nucleon-deuteron scattering with the JISP16 potential

NASA Astrophysics Data System (ADS)

Skibiński, R.; Golak, J.; Topolnicki, K.; Witała, H.; Volkotrub, Yu.; Kamada, H.; Shirokov, A. M.; Okamoto, R.; Suzuki, K.; Vary, J. P.

2018-01-01

The nucleon-nucleon J -matrix inverse scattering potential JISP16 is applied to elastic nucleon-deuteron scattering and the deuteron breakup process at the laboratory nucleon energies up to 135 MeV. The formalism of the Faddeev equations is used to obtain three-nucleon scattering states. We compare predictions based on the JISP16 force with data and with results based on various two-body interactions, including the CD Bonn, the Argonne AV18, the chiral force with the semilocal regularization at the fifth order of the chiral expansion and with low-momentum interactions obtained from the CD Bonn force as well as with the predictions from the combination of the AV18 NN interaction and the Urbana IX 3 N force. JISP16 provides a satisfactory description of some observables at low energies but strong deviations from data as well as from standard and chiral potential predictions with increasing energy. However, there are also polarization observables at low energies for which the JISP16 predictions differ from those based on the other forces by a factor of two. The reason for such a behavior can be traced back to the P -wave components of the JISP16 force. At higher energies the deviations can be enhanced by an interference with higher partial waves and by the properties of the JISP16 deuteron wave function. In addition, we compare the energy and angular dependence of predictions based on the JISP16 force with the results of the low-momentum interactions obtained with different values of the momentum cutoff parameter. We found that such low-momentum forces can be employed to interpret the nucleon-deuteron elastic scattering data only below some specific energy which depends on the cutoff parameter. Since JISP16 is defined in a finite oscillator basis, it has properties similar to low momentum interactions and its application to the description of nucleon-deuteron scattering data is limited to a low momentum transfer region.

de Sitter limit analysis for dark energy and modified gravity models

NASA Astrophysics Data System (ADS)

De Felice, Antonio; Frusciante, Noemi; Papadomanolakis, Georgios

2017-07-01

The effective field theory of dark energy and modified gravity is supposed to well describe, at low energies, the behavior of the gravity modifications due to one extra scalar degree of freedom. The usual curvature perturbation is very useful when studying the conditions for the avoidance of ghost instabilities as well as the positivity of the squared speeds of propagation for both the scalar and tensor modes, or the Stückelberg field performs perfectly when investigating the evolution of linear perturbations. We show that the viable parameter space identified by requiring no-ghost instabilities and positive squared speeds of propagation does not change by performing a field redefinition, while the requirement of the avoidance of tachyonic instability might instead be different. Therefore, we find it interesting to associate to the general modified gravity theory described in the effective field theory framework, a perturbation field which will inherit all of the properties of the theory. In the present paper we address the following questions: (1) how can we define such a field? and (2) what is the mass of such a field as the background approaches a final de Sitter state? We define a gauge-invariant quantity which identifies the density of the dark energy perturbation field valid for any background. We derive the mass associated to the gauge-invariant dark energy field on a de Sitter background, which we retain to be still a good approximation also at very low redshift (z ≃0 ). On this background we also investigate the value of the speed of propagation and we find that there exist classes of theories which admit a nonvanishing speed of propagation, even in the Horndeski model, for which a zero speed of sound has previously been found in the literature. We finally apply our results to specific well-known models.

Ghost crab populations respond to changing morphodynamic and habitat properties on sandy beaches

NASA Astrophysics Data System (ADS)

Lucrezi, Serena

2015-01-01

The morphodynamic state and habitat properties of microtidal sandy beaches largely account for variations in macrofauna structure. In ecological theory, the habitat harshness hypothesis and the habitat safety hypothesis explain variations in macrofauna populations of the intertidal and supratidal zones of sandy beaches. The former hypothesis states that intertidal macrofauna should increase from reflective to dissipative beaches. The latter hypothesis supports the idea that supratidal species are more successful on reflective beaches, given their relative independence from the swash. However, trends in abundance of supratidal species, particularly crustaceans, have been unclear and further investigation is therefore needed. This study tested the two hypotheses on the largest invertebrate intertidal-to-supratidal crustacean on sandy beaches, namely the ghost crab (genus Ocypode). Variations in ghost crab burrow density, abundance, size and across-shore distribution were measured on four warm-temperate microtidal sandy beaches in KwaZulu-Natal, South Africa. Burrow numbers increased with beach morphodynamic state, while average burrow size decreased. The steepest, narrowest and most inundation-prone beach represented the least hospitable environment for the ghost crabs. The results that are reported here tend to support the habitat harshness hypothesis. However, the relevance of i) individual physical variables, ii) tidal action, and iii) the ecology of various species, in shaping ghost crab population dynamics, is also discussed. The results contribute to the knowledge regarding population dynamics of intertidal and supratidal crustaceans across beach types.

Cutoff for extensions of massive gravity and bi-gravity

NASA Astrophysics Data System (ADS)

Matas, Andrew

2016-04-01

Recently there has been interest in extending ghost-free massive gravity, bi-gravity, and multi-gravity by including non-standard kinetic terms and matter couplings. We first review recent proposals for this class of extensions, emphasizing how modifications of the kinetic and potential structure of the graviton and modifications of the coupling to matter are related. We then generalize existing no-go arguments in the metric language to the vielbein language in second-order form. We give an ADM argument to show that the most promising extensions to the kinetic term and matter coupling contain a Boulware-Deser ghost. However, as recently emphasized, we may still be able to view these extensions as effective field theories below some cutoff scale. To address this possibility, we show that there is a decoupling limit where a ghost appears for a wide class of matter couplings and kinetic terms. In particular, we show that there is a decoupling limit where the linear effective vielbein matter coupling contains a ghost. Using the insight we gain from this decoupling limit analysis, we place an upper bound on the cutoff for the linear effective vielbein coupling. This result can be generalized to new kinetic interactions in the vielbein language in second-order form. Combined with recent results, this provides a strong uniqueness argument on the form of ghost-free massive gravity, bi-gravity, and multi-gravity.

Deformation associated with ghost craters and basins in volcanic smooth plains on Mercury: Strain analysis and implications for plains evolution

NASA Astrophysics Data System (ADS)

Klimczak, Christian; Watters, Thomas R.; Ernst, Carolyn M.; Freed, Andrew M.; Byrne, Paul K.; Solomon, Sean C.; Blair, David M.; Head, James W.

2012-09-01

Since its insertion into orbit about Mercury in March 2011, the MESSENGER spacecraft has imaged most previously unseen regions of the planet in unprecedented detail, revealing extensive regions of contiguous smooth plains at high northern latitudes and surrounding the Caloris basin. These smooth plains, thought to be emplaced by flood volcanism, are populated with several hundred ghost craters and basins, nearly to completely buried impact features having rims for which the surface expressions are now primarily rings of deformational landforms. Associated with some ghost craters are interior groups of graben displaying mostly polygonal patterns. The origin of these graben is not yet fully understood, but comparison with numerical models suggests that the majority of such features are the result of stresses from local thermal contraction. In this paper, we highlight a previously unreported category of ghost craters, quantify extensional strains across graben-bearing ghost craters, and make use of graben geometries to gain insights into the subsurface geology of smooth plains areas. In particular, the style and mechanisms of graben development imply that flooding of impact craters and basins led to substantial pooling of lavas, to thicknesses of ˜1.5 km. In addition, surface strains derived from groups of graben are generally in agreement with theoretically and numerically derived strains for thermal contraction.

GreenHouse Observations of the Stratosphere and Troposphere (GHOST): a novel shortwave infrared spectrometer developed for the Global Hawk unmanned aerial vehicle

NASA Astrophysics Data System (ADS)

Humpage, Neil; Bösch, Hartmut; Palmer, Paul I.; Parr-Burman, Phil M.; Vick, Andrew J. A.; Bezawada, Naidu N.; Black, Martin; Born, Andrew J.; Pearson, David; Strachan, Jonathan; Wells, Martyn

2014-10-01

The tropospheric distribution of greenhouse gases (GHGs) depends on surface flux variations, atmospheric chemistry and transport processes over a range of spatial and temporal scales. Accurate and precise atmospheric concentration observations of GHGs can be used to infer surface flux estimates, though their interpretation relies on unbiased atmospheric transport models. GHOST is a novel, compact shortwave infrared spectrometer which will observe tropospheric columns of CO2, CO, CH4 and H2O (along with the HDO/H2O ratio) during deployment on board the NASA Global Hawk unmanned aerial vehicle. The primary science objectives of GHOST are to: 1) test atmospheric transport models; 2) evaluate satellite observations of GHG column observations over oceans; and 3) complement in-situ tropopause transition layer observations from other Global Hawk instruments. GHOST comprises a target acquisition module (TAM), a fibre slicer and feed system, and a multiple order spectrograph. The TAM is programmed to direct solar radiation reflected by the ocean surface into a fibre optic bundle. Incoming light is then split into four spectral bands, selected to optimise remote observations of GHGs. The design uses a single grating and detector for all four spectral bands. We summarise the GHOST concept and its objectives, and describe the instrument design and proposed deployment aboard the Global Hawk platform.

Positive-negative corresponding normalized ghost imaging based on an adaptive threshold

NASA Astrophysics Data System (ADS)

Li, G. L.; Zhao, Y.; Yang, Z. H.; Liu, X.

2016-11-01

Ghost imaging (GI) technology has attracted increasing attention as a new imaging technique in recent years. However, the signal-to-noise ratio (SNR) of GI with pseudo-thermal light needs to be improved before it meets engineering application demands. We therefore propose a new scheme called positive-negative correspondence normalized GI based on an adaptive threshold (PCNGI-AT) to achieve a good performance with less amount of data. In this work, we use both the advantages of normalized GI (NGI) and positive-negative correspondence GI (P-NCGI). The correctness and feasibility of the scheme were proved in theory before we designed an adaptive threshold selection method, in which the parameter of object signal selection conditions is replaced by the normalizing value. The simulation and experimental results reveal that the SNR of the proposed scheme is better than that of time-correspondence differential GI (TCDGI), avoiding the calculation of the matrix of correlation and reducing the amount of data used. The method proposed will make GI far more practical in engineering applications.

23 CFR Appendix A to Part 1313 - Tamper Resistant Driver's License

Code of Federal Regulations, 2010 CFR

2010-04-01

...) Block graphics. (15) Security fonts and graphics with known hidden flaws. (16) Card stock, layer with colors. (17) Micro-graphics. (18) Retroflective security logos. (19) Machine readable technologies such... permit that has one or more of the following security features: (1) Ghost image. (2) Ghost graphic. (3...

Symplectic Quantization of a Reducible Theory

NASA Astrophysics Data System (ADS)

Barcelos-Neto, J.; Silva, M. B. D.

We use the symplectic formalism to quantize the Abelian antisymmetric tensor gauge field. It is related to a reducible theory in the sense that all of its constraints are not independent. A procedure like ghost-of-ghost of the BFV method has to be used, but in terms of Lagrange multipliers.

Strong population genetic structure and larval dispersal capability of the burrowing ghost shrimp (Neotrypaea californiensis)

EPA Science Inventory

The burrowing ghost shrimp, Neotrypaea californiensis, is a vital member of the estuarine benthic community. Dense populations of shrimp are found in the major estuaries of Washington and Oregon. Our study determines the genetic structure of shrimp populations in order to gain ...

What Not to Wear: Exposing the G(host) in Art Education

ERIC Educational Resources Information Center

Robinson-Cseke, Maria

2012-01-01

Two films, "Ghost World" and "Art School Confidential," serve as backdrops for an examination of art education, revealing identity conflicts among artist, student, and teacher. This article addresses ideas of uniqueness, uniformity, professionalism, and nakedness through the concept of personal dress. This critical discussion explores the…

Wormhole solutions with a complex ghost scalar field and their instability

NASA Astrophysics Data System (ADS)

Dzhunushaliev, Vladimir; Folomeev, Vladimir; Kleihaus, Burkhard; Kunz, Jutta

2018-01-01

We study compact configurations with a nontrivial wormholelike spacetime topology supported by a complex ghost scalar field with a quartic self-interaction. For this case, we obtain regular asymptotically flat equilibrium solutions possessing reflection symmetry. We then show their instability with respect to linear radial perturbations.

Evaluation of Two Numerical Wave Models with Inlet Physical Model

DTIC Science & Technology

2005-07-01

GHOST in inlets and near structures compared slightly better with measurements. DOI: 10.1061/~ASCE!0733-950X~2005!131:4~149! CE Database subject headings...full directional spectrum. GHOST represents wave diffraction by implementing a formulation of the Eikonal equation ~Rivero et al. 1997a, b!, whereas

Correlation-based motion vector processing with adaptive interpolation scheme for motion-compensated frame interpolation.

PubMed

Huang, Ai-Mei; Nguyen, Truong

2009-04-01

In this paper, we address the problems of unreliable motion vectors that cause visual artifacts but cannot be detected by high residual energy or bidirectional prediction difference in motion-compensated frame interpolation. A correlation-based motion vector processing method is proposed to detect and correct those unreliable motion vectors by explicitly considering motion vector correlation in the motion vector reliability classification, motion vector correction, and frame interpolation stages. Since our method gradually corrects unreliable motion vectors based on their reliability, we can effectively discover the areas where no motion is reliable to be used, such as occlusions and deformed structures. We also propose an adaptive frame interpolation scheme for the occlusion areas based on the analysis of their surrounding motion distribution. As a result, the interpolated frames using the proposed scheme have clearer structure edges and ghost artifacts are also greatly reduced. Experimental results show that our interpolated results have better visual quality than other methods. In addition, the proposed scheme is robust even for those video sequences that contain multiple and fast motions.

Morphological changes of the red blood cells treated with metal oxide nanoparticles.

PubMed

Kozelskaya, A I; Panin, A V; Khlusov, I A; Mokrushnikov, P V; Zaitsev, B N; Kuzmenko, D I; Vasyukov, G Yu

2016-12-01

The toxic effect of Al 2 O 3 , SiО 2 and ZrО 2 nanoparticles on red blood cells of Wistar rats was studied in vitro using the atomic force microscopy and the fluorescence analysis. Transformation of discocytes into echinocytes and spherocytes caused by the metal oxide nanoparticles was revealed. It was shown that only extremely high concentration of the nanoparticles (2mg/ml) allows correct estimating of their effect on the cell morphology. Besides, it was found out that the microviscosity changes of red blood cell membranes treated with nanoparticles began long before morphological modifications of the cells. On the contrary, the negatively charged ZrO 2 and SiO 2 nanoparticles did not affect ghost microviscosity up to concentrations of 1μg/ml and 0.1mg/ml, correspondingly. In its turn, the positively charged Al 2 O 3 nanoparticles induced structural changes in the lipid bilayer of the red blood cells already at a concentration of 0.05μg/ml. A decrease in microviscosity of the erythrocyte ghosts treated with Al 2 O 3 and SiO 2 nanoparticles was shown. It was detected that the interaction of ZrO 2 nanoparticles with the cells led to an increase in the membrane microviscosity and cracking of swollen erythrocytes. Copyright © 2016 Elsevier B.V. All rights reserved.

Defense Energy Support Center Fact Book: Providing Energy Solutions Worldwide

DTIC Science & Technology

2010-04-20

2011.through.fiscal. 2017 .. • Merging.System.Analysis.and.Program. Development.Oil.and.GAS.with.EBS.in.fiscal.2010...Wright.Patterson.Air.Force.Base,.OH Rock.Island.Arsenal,.IL Red.River.Army.Depot,. Texarkana ,.TX Malmstrom.Air.Force.Base,.MT Sub-Bituminous Coal: Ft..Wainwright,.AK

Inelastic black hole scattering from charged scalar amplitudes

NASA Astrophysics Data System (ADS)

Luna, Andrés; Nicholson, Isobel; O'Connell, Donal; White, Chris D.

2018-03-01

We explain how the lowest-order classical gravitational radiation produced during the inelastic scattering of two Schwarzschild black holes in General Relativity can be obtained from a tree scattering amplitude in gauge theory coupled to scalar fields. The gauge calculation is related to gravity through the double copy. We remove unwanted scalar forces which can occur in the double copy by introducing a massless scalar in the gauge theory, which is treated as a ghost in the link to gravity. We hope these methods are a step towards a direct application of the double copy at higher orders in classical perturbation theory, with the potential to greatly streamline gravity calculations for phenomenological applications.

Gravitational waves in ghost free bimetric gravity

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

Mohseni, Morteza, E-mail: m-mohseni@pnu.ac.ir

2012-11-01

We obtain a set of exact gravitational wave solutions for the ghost free bimetric theory of gravity. With a flat reference metric, the theory admits the vacuum Brinkmann plane wave solution for suitable choices of the coefficients of different terms in the interaction potential. An exact gravitational wave solution corresponding to a massive scalar mode is also admitted for arbitrary choice of the coefficients with the reference metric being proportional to the spacetime metric. The proportionality factor and the speed of the wave are calculated in terms of the parameters of the theory. We also show that a F(R) extensionmore » of the theory admits similar solutions but in general is plagued with ghost instabilities.« less

A unifying framework for ghost-free Lorentz-invariant Lagrangian field theories

NASA Astrophysics Data System (ADS)

Li, Wenliang

2018-04-01

We propose a framework for Lorentz-invariant Lagrangian field theories where Ostrogradsky's scalar ghosts could be absent. A key ingredient is the generalized Kronecker delta. The general Lagrangians are reformulated in the language of differential forms. The absence of higher order equations of motion for the scalar modes stems from the basic fact that every exact form is closed. The well-established Lagrangian theories for spin-0, spin-1, p-form, spin-2 fields have natural formulations in this framework. We also propose novel building blocks for Lagrangian field theories. Some of them are novel nonlinear derivative terms for spin-2 fields. It is nontrivial that Ostrogradsky's scalar ghosts are absent in these fully nonlinear theories.

Simple and Intelligible Language

ERIC Educational Resources Information Center

Blaisdell, Bob

2010-01-01

Some of the students in this author's developmental writing class are, to their own surprise, brilliant storytellers. They simply trust the tale, not the teller. If they tell a ghost story, they do not pretend, for instance, to believe in ghosts or zombies or duppies; they actually do. And so when they write faithfully, the reader sees what they…

Ghosts, Meaning, and Faith: After-Death Communications in Bereavement Narratives

ERIC Educational Resources Information Center

Kwilecki, Susan

2011-01-01

After-death communications (ADCs) are reported encounters with a deceased loved one, a contemporary type of ghost experience heralded as therapeutic in coping with bereavement. Pertinent literature generally illustrates the healing power of ADCs with brief, self-contained episodes. The functions of ADCs over the course of grief need exploration.…

Teen Girls' Resistance and the Disappearing Social in "Ghost World."

ERIC Educational Resources Information Center

Giroux, Henry A.

2002-01-01

Examines "Ghost World," a Hollywood film about youth, friendship, alienation, and survival, critically investigating how popular representations of youth signal a particular crisis of the social through a discourse of privatization, which fails to locate youth and problems they face within the related geographies of the social and political. The…

Ghost Hunting as a Means to Illustrate Scientific Methodology and Enhance Critical Thinking

ERIC Educational Resources Information Center

Rockwell, Steven C.

2012-01-01

The increasing popularity of television shows featuring paranormal investigations has led to a renewed enthusiasm in ghost hunting activities, and belief in the paranormal in general. These shows typically feature a group of investigators who, while claiming to utilize proper scientifically correct methodologies, violate many core scientific…

Relativistic harmonic oscillator revisited

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

Bars, Itzhak

2009-02-15

The familiar Fock space commonly used to describe the relativistic harmonic oscillator, for example, as part of string theory, is insufficient to describe all the states of the relativistic oscillator. We find that there are three different vacua leading to three disconnected Fock sectors, all constructed with the same creation-annihilation operators. These have different spacetime geometric properties as well as different algebraic symmetry properties or different quantum numbers. Two of these Fock spaces include negative norm ghosts (as in string theory), while the third one is completely free of ghosts. We discuss a gauge symmetry in a worldline theory approachmore » that supplies appropriate constraints to remove all the ghosts from all Fock sectors of the single oscillator. The resulting ghost-free quantum spectrum in d+1 dimensions is then classified in unitary representations of the Lorentz group SO(d,1). Moreover, all states of the single oscillator put together make up a single infinite dimensional unitary representation of a hidden global symmetry SU(d,1), whose Casimir eigenvalues are computed. Possible applications of these new results in string theory and other areas of physics and mathematics are briefly mentioned.« less

Ghost cell odontogenic carcinoma: A rare case report and review of literature.

PubMed

Martos-Fernández, Míriam; Alberola-Ferranti, Margarita; Hueto-Madrid, Juan Antonio; Bescós-Atín, Coro

2014-12-01

Ghost cell odontogenic carcinoma is a rare condition characterized by ameloblastic-like islands of epithelial cells with aberrant keratinitation in the form of Ghost cell with varying amounts of dysplastic dentina. We report a case of a 70 year-old woman with a rapid onset of painful swelling right maxillary tumor. Magnetic resonance showed a huge tumor dependent on the right half of the right hard palate with invasion of the pterygoid process and focally to the second branch of the trigeminal. Radiological stage was T4N0. The patient underwent a right subtotal maxillectomy with clear margins. Adjuvant radiotherapy was given. The patient was free of residual or recurrent disease 12 months after surgery. The tumor was 3,9cm in diameter. It was spongy and whitish gray. Microscopically the tumor was arranged in nets and trabeculae, occasionally forming palisade. Tumoral cells had clear cytoplasm with vesicular nuclei. There was atipia and mitosi with vascular and perineural invasion. The excised tumor was diagnosed as a GCOC. Ghost cell carcinoma is a rare odontogenic carcinoma. Its course is unpredictable, ranging from locally invasive tumors of slow growth to highly aggressive and infiltrative ones. Wide surgical excision with clean margins is the treatment of choice although its combination with postoperative radiation therapy, with or without chemotherapy, remains controversial. Key words:Ameloblastic carcinoma, calcifying odontogenic cyst, Ghost cell carcinoma, keratinizing epithelial odontogenic cyst, maxillary tumor, odontogenic carcinoma.

'Ghost of Mirach' Rears its Spooky Head

NASA Technical Reports Server (NTRS)

2008-01-01

[figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Visible/DSS Click on image for larger version Ultraviolet/GALEX Click on image for larger version Poster Version Click on image for larger version

The 'Ghost of Mirach' galaxy is shown in visible light on the left, and in ultraviolet as seen by NASA's Galaxy Evolution Explorer on the right. The fields of view are identical in both pictures, with the Ghost of Mirach a galaxy called NGC 404 seen as the whitish spot in the center of the images. Mirach is a red giant star that looms large in visible light. Because NGC 404 is lost in the glare of this star, it was nicknamed the Ghost of Mirach.

But when the galaxy is viewed in ultraviolet light, it comes to 'life,' revealing a never-before-seen ring. This ring, seen in blue in the picture on the right, contains new stars a surprise considering that the galaxy was previously thought to be, essentially, dead.

The field of view spans 55,000 light years across. The Ghost of Mirach is located 11 million light-years from Earth. The star Mirach is very close in comparison it is only 200 light-years away and is visible with the naked eye.

The visible data come from the Digitized Sky Survey of the Space Telescope Science Institute in Baltimore, Md.

Ambient beam motion and its excitation by ghost lines in the Tevatron

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

Shiltsev, V.; /Fermilab

2011-03-01

Transverse betatron motion of the Tevatron proton beam is measured and analyzed. It is shown that the motion is coherent and excited by external sources of unknown origins. Observations of the time-varying 'ghost lines' in the betatron spectrum are reported. The direct measurement of the rms betatron oscillations amplitude estimates it at about 110 nm at {beta}{sub y} {approx} 900 m. Correspondingly, at the amplitudes at the average beta function location with {beta}{sub y} {approx} 50 m is about 25 nm. Given that such direct measurements with clearly observable betatron peak were not repeatedly reproducible, one can conclude that wellmore » know 'ghost lines' are the reason for that - as they are come and go without any obvious regularity. Our analysis of these 'ghost lines' shows that (a) besides slow motion across frequencies, they also exhibit oscillatory movements with period varying from 15-20 min to few hours; (b) for the stores analysed, the lines add about factor of 2 to average - over colliding store duration - Schottky power in the betatron bands. The latter allows to estimate that they contribute about half to the previously determined the rms normalized emittance growth rate of some 0.06 {pi} mm mrad/hr. The Tevatron 'ghost lines' look very similar to infamous 'humps' recently observed in the LHC. Those 'humps' are unwanted oscillations seen repeatedly in the LHC beams (mostly in the vertical plane) and also believed to be caused by external excitations.« less

Ghost fringe removal techniques using Lissajous data presentation

DOE PAGES

Erskine, David J.; Eggert, J. H.; Celliers, P. M.; ...

2016-03-14

A VISAR (Velocity Interferometer System for Any Reflector) is a Dopplervelocity interferometer which is an important optical diagnostic in shockwave experiments at the national laboratories, used to measureequation of state(EOS) of materials under extreme conditions. Unwanted reflection of laser light from target windows can produce an additional component to the VISAR fringe record that can distort and obscure the true velocity signal. When accurately removing this so-called ghost artifact component is essential for achieving high accuracy EOSmeasurements, especially when the true light signal is only weakly reflected from the shock front. Independent of the choice of algorithm for processing themore » raw data into a complex fringe signal, we have found it beneficial to plot this signal as a Lissajous and seek the proper center of this path, even under time varying intensity which can shift the perceived center. Moreover, the ghost contribution is then solved by a simple translation in the complex plane that recenters the Lissajous path. For continuous velocity histories, we find that plotting the fringe magnitude vs nonfringing intensity and optimizing linearity is an invaluable tool for determining accurate ghost offsets. For discontinuous velocity histories, we have developed graphically inspired methods which relate the results of two VISARs having different velocity per fringe proportionalities or assumptions of constant fringe magnitude to find the ghost offset. The technique can also remove window reflection artifacts in generic interferometers, such as in the metrology of surfaces.« less

Agile Thermal Management STT-RX. Towards High Energy Density, High Conductivity Thermal Energy Storage Composites (PREPRINT)

DTIC Science & Technology

2011-12-01

management system. This paper describes recent development of salt hydrate-based TES composites at the Air Force Research Laboratory. Salt hydrates are...composites. 15. SUBJECT TERMS thermal energy storage, composite, salt hydrate, graphic foam 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...part of a thermal management system. This paper describes recent development of salt hydrate-based TES composites at the Air Force Research

The energy spectrum in a barotropic atmosphere

NASA Astrophysics Data System (ADS)

Kurgansky, M. V.

2008-03-01

In a forced-dissipative barotropic model of the atmosphere on a spherical planet, by following mathematical techniques in (Thompson, P. D.: The equilibrium energy spectrum of randomly forced two-dimensional turbulence, Journal of the Atmospheric Sciences, 30, 1593-1598, 1973) but applying them in a novel context of the discrete spectrum on a rotating sphere, the "minus 2" energy spectrum for wavenumbers much greater than a characteristic wavenumber of the baroclinic forcing has been obtained if the forcing is taken in the simplest and most fundamental form. Some observation-based atmospheric kinetic energy spectra, with their slopes lying between "minus 2" and "minus 3" laws, are discussed from the perspective of the deduced "minus 2" energy spectrum.

Inflation with a Weyl term, or ghosts at work

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

Deruelle, Nathalie; Youssef, Ahmed; Sasaki, Misao

2011-03-01

In order to assess the role of ghosts in cosmology, we study the evolution of linear cosmological perturbations during inflation when a Weyl term is added to the action. Our main results are that vector perturbations can no longer be ignored and that scalar modes diverge in the newtonian gauge but remain bounded in the comoving slicing.

Perturbative Yang-Mills theory without Faddeev-Popov ghost fields

NASA Astrophysics Data System (ADS)

Huffel, Helmuth; Markovic, Danijel

2018-05-01

A modified Faddeev-Popov path integral density for the quantization of Yang-Mills theory in the Feynman gauge is discussed, where contributions of the Faddeev-Popov ghost fields are replaced by multi-point gauge field interactions. An explicit calculation to O (g2) shows the equivalence of the usual Faddeev-Popov scheme and its modified version.

Prebifurcation periodic ghost orbits in semiclassical quantization

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

Kus, M.; Haake, F.; Delande, D.

1993-10-04

Classical periodic orbits are stationary-phase points in path integral representations of quantum propagators. We show that complex solutions of the stationary-phase equation, not corresponding to real classical periodic orbits, give additional contributions to the propagator which can be important, especially near bifurcations. We reveal the existence and relevance of such periodic ghost orbits for a kicked top.

Deformations of vector-scalar models

NASA Astrophysics Data System (ADS)

Barnich, Glenn; Boulanger, Nicolas; Henneaux, Marc; Julia, Bernard; Lekeu, Victor; Ranjbar, Arash

2018-02-01

Abelian vector fields non-minimally coupled to uncharged scalar fields arise in many contexts. We investigate here through algebraic methods their consistent deformations ("gaugings"), i.e., the deformations that preserve the number (but not necessarily the form or the algebra) of the gauge symmetries. Infinitesimal consistent deformations are given by the BRST cohomology classes at ghost number zero. We parametrize explicitly these classes in terms of various types of global symmetries and corresponding Noether currents through the characteristic cohomology related to antifields and equations of motion. The analysis applies to all ghost numbers and not just ghost number zero. We also provide a systematic discussion of the linear and quadratic constraints on these parameters that follow from higher-order consistency. Our work is relevant to the gaugings of extended supergravities.

Toll-like receptor variation in the bottlenecked population of the Seychelles warbler: computer simulations see the 'ghost of selection past' and quantify the 'drift debt'.

PubMed

Gilroy, D L; Phillips, K P; Richardson, D S; van Oosterhout, C

2017-07-01

Balancing selection can maintain immunogenetic variation within host populations, but detecting its signal in a postbottlenecked population is challenging due to the potentially overriding effects of drift. Toll-like receptor genes (TLRs) play a fundamental role in vertebrate immune defence and are predicted to be under balancing selection. We previously characterized variation at TLR loci in the Seychelles warbler (Acrocephalus sechellensis), an endemic passerine that has undergone a historical bottleneck. Five of seven TLR loci were polymorphic, which is in sharp contrast to the low genomewide variation observed. However, standard population genetic statistical methods failed to detect a contemporary signature of selection at any TLR locus. We examined whether the observed TLR polymorphism could be explained by neutral evolution, simulating the population's demography in the software DIYABC. This showed that the posterior distributions of mutation rates had to be unrealistically high to explain the observed genetic variation. We then conducted simulations with an agent-based model using typical values for the mutation rate, which indicated that weak balancing selection has acted on the three TLR genes. The model was able to detect evidence of past selection elevating TLR polymorphism in the prebottleneck populations, but was unable to discern any effects of balancing selection in the contemporary population. Our results show drift is the overriding evolutionary force that has shaped TLR variation in the contemporary Seychelles warbler population, and the observed TLR polymorphisms might be merely the 'ghost of selection past'. Forecast models predict immunogenetic variation in this species will continue to be eroded in the absence of contemporary balancing selection. Such 'drift debt' occurs when a gene pool has not yet reached its new equilibrium level of polymorphism, and this loss could be an important threat to many recently bottlenecked populations. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

Reassignment of scattered emission photons in multifocal multiphoton microscopy.

PubMed

Cha, Jae Won; Singh, Vijay Raj; Kim, Ki Hean; Subramanian, Jaichandar; Peng, Qiwen; Yu, Hanry; Nedivi, Elly; So, Peter T C

2014-06-05

Multifocal multiphoton microscopy (MMM) achieves fast imaging by simultaneously scanning multiple foci across different regions of specimen. The use of imaging detectors in MMM, such as CCD or CMOS, results in degradation of image signal-to-noise-ratio (SNR) due to the scattering of emitted photons. SNR can be partly recovered using multianode photomultiplier tubes (MAPMT). In this design, however, emission photons scattered to neighbor anodes are encoded by the foci scan location resulting in ghost images. The crosstalk between different anodes is currently measured a priori, which is cumbersome as it depends specimen properties. Here, we present the photon reassignment method for MMM, established based on the maximum likelihood (ML) estimation, for quantification of crosstalk between the anodes of MAPMT without a priori measurement. The method provides the reassignment of the photons generated by the ghost images to the original spatial location thus increases the SNR of the final reconstructed image.

Magneto-optical imaging technique for hostile environments: The ghost imaging approach

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

Meda, A.; Caprile, A.; Avella, A.

2015-06-29

In this paper, we develop an approach to magneto optical imaging (MOI), applying a ghost imaging (GI) protocol to perform Faraday microscopy. MOI is of the utmost importance for the investigation of magnetic properties of material samples, through Weiss domains shape, dimension and dynamics analysis. Nevertheless, in some extreme conditions such as cryogenic temperatures or high magnetic field applications, there exists a lack of domain images due to the difficulty in creating an efficient imaging system in such environments. Here, we present an innovative MOI technique that separates the imaging optical path from the one illuminating the object. The techniquemore » is based on thermal light GI and exploits correlations between light beams to retrieve the image of magnetic domains. As a proof of principle, the proposed technique is applied to the Faraday magneto-optical observation of the remanence domain structure of an yttrium iron garnet sample.« less

On the curious spectrum of duality invariant higher-derivative gravity

NASA Astrophysics Data System (ADS)

Hohm, Olaf; Naseer, Usman; Zwiebach, Barton

2016-08-01

We analyze the spectrum of the exactly duality and gauge invariant higher-derivative double field theory. While this theory is based on a chiral CFT and does not correspond to a standard string theory, our analysis illuminates a number of issues central in string theory. The full quadratic action is rewritten as a two-derivative theory with additional fields. This allows for a simple analysis of the spectrum, which contains two massive spin-2 ghosts and massive scalars, in addition to the massless fields. Moreover, in this formulation, the massless or tensionless limit α ' → ∞ is non-singular and leads to an enhanced gauge symmetry. We show that the massive modes can be integrated out exactly at the quadratic level, leading to an infinite series of higher-derivative corrections. Finally, we present a ghost-free massive extension of linearized double field theory, which employs a novel mass term for the dilaton and metric.

Ghost Images in Helioseismic Holography? Toy Models in a Uniform Medium

NASA Astrophysics Data System (ADS)

Yang, Dan

2018-02-01

Helioseismic holography is a powerful technique used to probe the solar interior based on estimations of the 3D wavefield. The Porter-Bojarski holography, which is a well-established method used in acoustics to recover sources and scatterers in 3D, is also an estimation of the wavefield, and hence it has the potential of being applied to helioseismology. Here we present a proof-of-concept study, where we compare helioseismic holography and Porter-Bojarski holography under the assumption that the waves propagate in a homogeneous medium. We consider the problem of locating a point source of wave excitation inside a sphere. Under these assumptions, we find that the two imaging methods have the same capability of locating the source, with the exception that helioseismic holography suffers from "ghost images" ( i.e. artificial peaks away from the source location). We conclude that Porter-Bojarski holography may improve the method currently used in helioseismology.

Quantum corrections to the generalized Proca theory via a matter field

NASA Astrophysics Data System (ADS)

Amado, André; Haghani, Zahra; Mohammadi, Azadeh; Shahidi, Shahab

2017-09-01

We study the quantum corrections to the generalized Proca theory via matter loops. We consider two types of interactions, linear and nonlinear in the vector field. Calculating the one-loop correction to the vector field propagator, three- and four-point functions, we show that the non-linear interactions are harmless, although they renormalize the theory. The linear matter-vector field interactions introduce ghost degrees of freedom to the generalized Proca theory. Treating the theory as an effective theory, we calculate the energy scale up to which the theory remains healthy.

Potential Second-Harmonic Ghost Bands in Fourier Transform Infrared (FT-IR) Difference Spectroscopy of Proteins.

PubMed

Ito, Shota; Kandori, Hideki; Lorenz-Fonfria, Victor A

2018-06-01

Fourier transform infrared (FT-IR) difference absorption spectroscopy is a common method for studying the structural and dynamical aspects behind protein function. In particular, the 2800-1800 cm -1 spectral range has been used to obtain information about internal (deuterated) water molecules, as well as site-specific details about cysteine residues and chemically modified and artificial amino acids. Here, we report on the presence of ghost bands in cryogenic light-induced FT-IR difference spectra of the protein bacteriorhodopsin. The presence of these ghost bands can be particularly problematic in the 2800-1900 cm -1 region, showing intensities similar to O-D vibrations from water molecules. We demonstrate that they arise from second harmonics from genuine chromophore bands located in the 1400-850 cm -1 region, generated by double-modulation artifacts caused from reflections of the IR beam at the sample and at the cryostat windows back to the interferometer (inter-reflections). The second-harmonic ghost bands can be physically removed by placing an optical filter of suitable cutoff in the beam path, but at the cost of losing part of the multiplexing advantage of FT-IR spectroscopy. We explored alternatives to the use of optical filters. Tilting the cryostat windows was effective in reducing the intensity of the second harmonic artifacts but tilting the sample windows was not, presumably by their close proximity to the focal point of the IR beam. We also introduce a simple numerical post-processing approach that can partially, but not fully, correct for second-harmonic ghost bands in FT-IR difference spectra.

Ontogenetic changes in biochemical composition during larval and early postlarval development of Lepidophthalmus louisianensis, a ghost shrimp with abbreviated development

EPA Science Inventory

Larvae of the ghost shrimp, Lepidophthalmus louisianensis, were mass-reared under laboratory conditions (28|C; 20o/ooS) from hatching to the decapodid (D) stage. Iatroscan lipid class analysis revealed that polar lipids (Zoea I: 77.4|1.7%; Zoea II: 77.5|2.1%; Decapodid: 80.0|1.7%...

The Contribution of the Holy Ghost Congregation to the Educational Development of Nigeria: Historical and Contemporary Reflections

ERIC Educational Resources Information Center

Amadi, Anthony

2016-01-01

This article is a historical narrative about the contribution the Holy Ghost Congregation made in the educational development of Nigeria. It is narrative because it highlights the events and the work of the early Spiritan missionaries that brought education and its benefits to Nigerians. It is pedagogic because it describes the methods these Holy…

Telling Ghost Stories with the Voice of an Ogre: Deleuze, Identity, and Disruptive Pedagogies

ERIC Educational Resources Information Center

Beighton, Christian

2017-01-01

French philosopher Gilles Deleuze (1925-95) was something of a cult figure among his university students in the 1970s and 1980s, "telling ghost stories with the voice of an ogre" (Jaeglé, 2005:10). More recently, academic interest in the educational possibilities of his work has grown considerably in Anglophone countries. Perhaps texts…

Geophysical expression of the Ghost Dance fault, Yucca Mountain, Nevada

USGS Publications Warehouse

Ponce, D.A.; Langenheim, V.E.; ,

1995-01-01

Gravity and ground magnetic data collected along surveyed traverses across Antler and Live Yucca Ridges, on the eastern flank of Yucca Mountain, Nevada, reveal small-scale faulting associated with the Ghost Dance and possibly other faults. These studies are part of an effort to evaluate faulting in the vicinity of a potential nuclear waste repository at Yucca Mountain.

More on ghosts in the Dvali-Gabadaze-Porrati model

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

Gorbunov, Dmitry; Sibiryakov, Sergei; Koyama, Kazuya

2006-02-15

It is shown by an explicit calculation that the excitations about the self-accelerating cosmological solution of the Dvali-Gabadaze-Porrati model contain a ghost mode. This raises serious doubts about viability of this solution. Our analysis reveals the similarity between the quadratic theory for the perturbations around the self-accelerating universe and an Abelian gauge model with two Stueckelberg fields.

Final Environmental Assessment for Test Area D-84 Waterside Redevelopment

DTIC Science & Technology

2012-09-01

typically adapted for life in saturated soil conditions (U.S. Army, 1987). Wetlands are the most productive ecosystems in the world (Mitsch and...such as amphipods, Jancelets, polychaetes, gastropods , ghost shrimp, isopods, molluscs and/or crustaceans, within estuarine and marine habitats and...lancelets, polychaetes, gastropods , ghost shrimp, isopods, mollusks, and/or crustaceans within estuarine and marine habitats and substrates for subadult

Geophysical expression of the Ghost Dance Fault, Yucca Mountain, Nevada

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

Ponce, D.A.; Langenheim, V.E.

1995-12-01

Gravity and ground magnetic data collected along surveyed traverses across Antler and Live Yucca Ridges, on the eastern flank of Yucca Mountain, Nevada, reveal small-scale faulting associated with the Ghost Dance and possibly other faults. These studies are part of an effort to evaluate faulting in the vicinity of a potential nuclear waste repository at Yucca Mountain.

Extinction risk of Ipomopsis sancti-spiritus in Holy Ghost Canyon with and without management intervention

Treesearch

Joyce Maschinski

2001-01-01

Small populations are threatened with deterministic and stochastic events that can drive the number of individuals below a critical threshold for survival. Long-term studies allow us to increase our understanding of processes required for their conservation. In the past 7 years, the population of the federally endangered Holy Ghost ipomopsis (Ipomopsis sancti-spiritus...

Numerically Stable Fluid-Structure Interactions Between Compressible Flow and Solid Structures

DTIC Science & Technology

2011-01-28

normal component VrN = ~Vr · ~N and its tangential component ~ VrT = ~Vr − VrN ~N . In order to remain continuous with the effective velocity of the...the interface and thus we can use it directly, giving the final ghost cell velocity ~Vg = VgN ~N + ~ VrT . Once ghost cells are filled, explicit body

Ghost image in enhanced self-heterodyne synthetic aperture imaging ladar

NASA Astrophysics Data System (ADS)

Zhang, Guo; Sun, Jianfeng; Zhou, Yu; Lu, Zhiyong; Li, Guangyuan; Xu, Mengmeng; Zhang, Bo; Lao, Chenzhe; He, Hongyu

2018-03-01

The enhanced self-heterodyne synthetic aperture imaging ladar (SAIL) self-heterodynes two polarization-orthogonal echo signals to eliminate the phase disturbance caused by atmospheric turbulence and mechanical trembling, uses heterodyne receiver instead of self-heterodyne receiver to improve signal-to-noise ratio. The principle and structure of the enhanced self-heterodyne SAIL are presented. The imaging process of enhanced self-heterodyne SAIL for distributed target is also analyzed. In enhanced self-heterodyne SAIL, the phases of two orthogonal-polarization beams are modulated by four cylindrical lenses in transmitter to improve resolutions in orthogonal direction and travel direction, which will generate ghost image. The generation process of ghost image in enhanced self-heterodyne SAIL is mathematically detailed, and a method of eliminating ghost image is also presented, which is significant for far-distance imaging. A number of experiments of enhanced self-heterodyne SAIL for distributed target are presented, these experimental results verify the theoretical analysis of enhanced self-heterodyne SAIL. The enhanced self-heterodyne SAIL has the capability to eliminate the influence from the atmospheric turbulence and mechanical trembling, has high advantage in detecting weak signals, and has promising application for far-distance ladar imaging.

A specter of coexistence: Is centrifugal community organization haunted by the ghost of competition?

USGS Publications Warehouse

Wasserberg, Gideon; Kotler, B.P.; Morris, D.W.; Abramsky, Z.

2006-01-01

In a centrifugally organized community species prefer the same habitat (called "core") but differ in their secondary habitat preferences. The first model of centrifugal community organization (CCO) predicted that optimally foraging, symmetrically competing species would share use of the core habitat at all density combinations. But one might also assume that the competition in the core habitat is asymmetrical, that is, that one of the species (the dominant) has a behavioral advantage therein. In this study, we asked how should habitat use evolve in a centrifugally organized community if its species compete asymmetrically in the core habitat? To address this question we developed an "isoleg model". The model predicts that in a centrifugally organized community, asymmetric competition promotes the use of the core habitat exclusively by the dominant species at most points in the state space. The separation of the core habitat use by the species ("the ghost of competition past") may be either complete or partial ("partial ghost"), and behavior at the stable competitive equilibrium between the species could determine whether coexistence should occur at the "complete-" or the "partial ghost" regions. This version of CCO should be a common feature of competitive systems.

Hands-On Science Mysteries for Grades 3-6: Standards-Based Inquiry Investigations

ERIC Educational Resources Information Center

Taris, James Robert; Taris, Louis James

2006-01-01

In "Hands-On Science Mysteries for Grades 3-6," the authors connect science to real-world situations by investigating actual mysteries and phenomena, such as the strange heads on Easter Island, the ghost ship "Mary Celeste," and the "Dancing Stones" of Death Valley. The labs are designed to encourage the development…

HAMLET. LITERATURE CURRICULUM VI, TEACHER AND STUDENT VERSIONS.

ERIC Educational Resources Information Center

KITZHABER, ALBERT R.

THIS CULMINATING UNIT OF THE 12TH-GRADE OREGON LITERATURE CURRICULUM IS BASED UPON ONE WORK, "HAMLET." THE TEACHER VERSION INCLUDES DISCUSSIONS OF (1) THE RELEVANCE OF HAMLET'S CHARACTER TO MODERN TIMES, (2) THE PROBLEMS IN THE CHARACTERIZATIONS OF THE GHOST, CLAUDIUS, AND HAMLET, (3) THE PLAY'S THREE-PHASE STRUCTURE, (4) THE PLAY'S…

Background history and cosmic perturbations for a general system of self-conserved dynamical dark energy and matter

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

Gómez-Valent, Adrià; Karimkhani, Elahe; Solà, Joan, E-mail: adriagova@ecm.ub.edu, E-mail: e.karimkhani91@basu.ac.ir, E-mail: sola@ecm.ub.edu

We determine the Hubble expansion and the general cosmic perturbation equations for a general system consisting of self-conserved matter, ρ{sub m}, and self-conserved dark energy (DE), ρ{sub D}. While at the background level the two components are non-interacting, they do interact at the perturbations level. We show that the coupled system of matter and DE perturbations can be transformed into a single, third order, matter perturbation equation, which reduces to the (derivative of the) standard one in the case that the DE is just a cosmological constant. As a nontrivial application we analyze a class of dynamical models whose DEmore » density ρ{sub D}(H) consists of a constant term, C{sub 0}, and a series of powers of the Hubble rate. These models were previously analyzed from the point of view of dynamical vacuum models, but here we treat them as self-conserved DE models with a dynamical equation of state. We fit them to the wealth of expansion history and linear structure formation data and compare their fit quality with that of the concordance ΛCDM model. Those with C{sub 0}=0 include the so-called ''entropic-force'' and ''QCD-ghost'' DE models, as well as the pure linear model ρ{sub D}∼H, all of which appear strongly disfavored. The models with C{sub 0}≠0 , in contrast, emerge as promising dynamical DE candidates whose phenomenological performance is highly competitive with the rigid Λ-term inherent to the ΛCDM.« less

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

Jazayeri, Sadra; Mukohyama, Shinji; Kavli Institute for the Physics and Mathematics of the Universe

In the setup of ghost condensation model the generalized second law of black hole thermodynamics can be respected under a radiatively stable assumption that couplings between the field responsible for ghost condensate and matter fields such as those in the Standard Model are suppressed by the Planck scale. Since not only black holes but also cosmology are expected to play important roles towards our better understanding of gravity, we consider a cosmological setup to test the theory of ghost condensation. In particular we shall show that the de Sitter entropy bound proposed by Arkani-Hamed, et al. is satisfied if ghostmore » inflation happened in the early epoch of our universe and if there remains a tiny positive cosmological constant in the future infinity. We then propose a notion of cosmological Page time after inflation.« less

Gravity and magnetic investigations of the Ghost Dance and Solitario Canyon faults, Yucca Mountain, Nevada

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

Ponce, D.A.; Langenheim, V.E.

1995-12-31

Ground magnetic and gravity data collected along traverses across the Ghost Dance and Solitario Canyon faults on the eastern and western flanks, respectively, of Yucca Mountain in southwest Nevada are interpreted. These data were collected as part of an effort to evaluate faulting in the vicinity of a potential nuclear waste repository at Yucca Mountain. Gravity and magnetic data and models along traverses across the Ghost Dance and Solitario Canyon faults show prominent anomalies associated with known faults and reveal a number of possible concealed faults beneath the eastern flank of Yucca Mountain. The central part of the eastern flankmore » of Yucca Mountain is characterized by several small amplitude anomalies that probably reflect small scale faulting.« less

Fluctuations, ghosts, and the cosmological constant

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

Hirayama, T.; Holdom, B.

2004-12-15

For a large region of parameter space involving the cosmological constant and mass parameters, we discuss fluctuating spacetime solutions that are effectively Minkowskian on large time and distance scales. Rapid, small amplitude oscillations in the scale factor have a frequency determined by the size of a negative cosmological constant. A field with modes of negative energy is required. If it is gravity that induces a coupling between the ghostlike and normal fields, we find that this results in stochastic rather than unstable behavior. The negative energy modes may also permit the existence of Lorentz invariant fluctuating solutions of finite energymore » density. Finally we consider higher derivative gravity theories and find oscillating metric solutions in these theories without the addition of other fields.« less

Fluid Expulsion, Habitability, and the Search for Life on Mars

NASA Technical Reports Server (NTRS)

Oehler, Dorothy Z.; Allen, Carlton C.

2012-01-01

Habitability assessments are critical for identifying settings in which potential biosignatures could exist in quantities large enough to be detected by rovers. Habitability depends on 1) the potential for long-lived liquid water, 2) conditions affording protection from surface processes destructive to organic biomolecules, and 3) a source of renewing nutrients and energy. Of these criteria, the latter is often overlooked. Here we present an analysis of a large "ghost" crater in northern Chryse Planitia [1] that appears to have satisfied each of these requirements, with several processes providing potential sources of nutrient/energy renewal [1-2]. This analysis can serve as a model for identifying other localities that could provide similarly favorable settings in which to seek evidence of life on Mars.

Accuracy Test of the OPLS-AA Force Field for Calculating Free Energies of Mixing and Comparison with PAC-MAC

PubMed Central

2017-01-01

We have calculated the excess free energy of mixing of 1053 binary mixtures with the OPLS-AA force field using two different methods: thermodynamic integration (TI) of molecular dynamics simulations and the Pair Configuration to Molecular Activity Coefficient (PAC-MAC) method. PAC-MAC is a force field based quasi-chemical method for predicting miscibility properties of various binary mixtures. The TI calculations yield a root mean squared error (RMSE) compared to experimental data of 0.132 kBT (0.37 kJ/mol). PAC-MAC shows a RMSE of 0.151 kBT with a calculation speed being potentially 1.0 × 104 times greater than TI. OPLS-AA force field parameters are optimized using PAC-MAC based on vapor–liquid equilibrium data, instead of enthalpies of vaporization or densities. The RMSE of PAC-MAC is reduced to 0.099 kBT by optimizing 50 force field parameters. The resulting OPLS-PM force field has a comparable accuracy as the OPLS-AA force field in the calculation of mixing free energies using TI. PMID:28418655

Design and experimental analysis of broadband energy harvesting from vortex-induced vibrations

NASA Astrophysics Data System (ADS)

Zhang, L. B.; Abdelkefi, A.; Dai, H. L.; Naseer, R.; Wang, L.

2017-11-01

In this paper, an operable strategy to enhance the output power of piezoelectric energy harvesting from vortex-induced vibration (VIV) using nonlinear magnetic forces is proposed for the first time. Two introduced small magnets with a repulsive force are, respectively, attached on a lower support and the bottom of a circular cylinder which is subjected to a uniform wind speed. Experiments show that the natural frequency of the VIV-based energy harvester is significantly changed by varying the relative position of the two magnets and hence the synchronization region is shifted. It is observed that the proposed energy harvester displays a softening behavior due to the impact of nonlinear magnetic forces, which greatly increases the performance of the VIV-based energy harvesting system, showing a wider synchronization region and a higher level of the harvested power by 138% and 29%, respectively, compared to the classical configuration. This proposed design can provide the groundwork to promote the output power of conventional VIV-based piezoelectric generators, further enabling to realize self-powered systems.

Optimized Free Energies from Bidirectional Single-Molecule Force Spectroscopy

NASA Astrophysics Data System (ADS)

Minh, David D. L.; Adib, Artur B.

2008-05-01

An optimized method for estimating path-ensemble averages using data from processes driven in opposite directions is presented. Based on this estimator, bidirectional expressions for reconstructing free energies and potentials of mean force from single-molecule force spectroscopy—valid for biasing potentials of arbitrary stiffness—are developed. Numerical simulations on a model potential indicate that these methods perform better than unidirectional strategies.

Geothermal studies at Kirtland Air Force Base, Albuquerque, New Mexico

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

Riddle, L.; Grant, B.

Due to an effort by government installations to discontinue use of natural gas, alternative energy sources are being investigated at Kirtland Air Force Base, Albuquerque, New Mexico. New Mexico has geologic characteristics favorable for geothermal energy utilization. Local heat flow and geochemical studies indicate a normal subsurface temperature regime. The alluvial deposits, however, extend to great depths where hot fluids, heated by the normal geothermal gradient, could be encountered. Two potential models for tapping geothermal energy are presented: the basin model and the fault model.

Multiloop ghost vertices and the determination of the multiloop measure

NASA Astrophysics Data System (ADS)

West, P.

1988-04-01

Using the group-theoretic approach to string theory, the multiloop vertices previously computed are extended to include ghost oscillators. In accord with the approach, we show how demanding that zero-norm physical states decouple leads to a set of first-order differential equations which uniquely determine the multiloop measure. Permanent address: Mathematics Department, Kings College, Strand, London WC2R 2LS, UK.

Education as Seance: Specters, Spirits, and the Expansion of Memory

ERIC Educational Resources Information Center

Ruitenberg, Claudia

2009-01-01

In this essay I propose that education be conceived as seance: a place where ghosts are summoned in order that we may come to (speaking) terms with them. Against the backdrop of my own summoning of the ghosts haunting my childhood visits to a nearby castle, I draw on the work of Jacques Derrida to provide a theoretical rationale for the importance…

An A/r/tographic Inquiry of a Silenced First Nation Ancestry, Hauntology, G(hosts) and Art(works): An Exhibition Catalogue

ERIC Educational Resources Information Center

Cloutier, Geneviève

2016-01-01

As a hauntological artist, I deconstruct my silenced First Nation Wolastoqiyik (Maliseet) ancestry and look towards the intergenerational narratives of my grandmother, mother, and I. Employing the methodology of a/r/tography, the intersection of autobiography and art-making, I utilize diverse art forms to find that g(hosts) reside amongst spaces…

Gravity and magnetic data across the Ghost Dance Fault in WT-2 Wash, Yucca Mountain, Nevada

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

Oliver, H.W.; Sikora, R.F.

1994-12-31

Detailed gravity and ground magnetic data were obtained in September 1993 along a 4,650 ft-long profile across the Ghost Dance Fault system in WT-2 Wash. Gravity stations were established every 150 feet along the profile. Total-field magnetic measurements made initially every 50 ft along the profile, then remade every 20 ft through the fault zone. These new data are part of a geologic and geophysical study of the Ghost Dance Fault (GDF) which includes detailed geologic mapping, seismic reflection, and some drilling including geologic and geophysical logging. The Ghost Dance Fault is the only through-going fault that has been identifiedmore » within the potential repository for high-level radioactive waste at Yucca Mountain, Nevada. Preliminary gravity results show a distinct decrease of 0.1 to 0.2 mGal over a 600-ft-wide zone to the east of and including the mapped fault. The gravity decrease probably marks a zone of brecciation. Another fault-offset located about 2,000 ft to the east of the GDF was detected by seismic reflection data and is also marked by a distinct gravity low. The ground magnetic data show a 200-ft-wide magnetic low of about 400 nT centered about 100 ft east of the Ghost Dance Fault. The magnetic low probably marks a zone of brecciation within the normally polarized Topopah Spring Tuff, the top of which is about 170 ft below the surface, and which is known from drilling to extend to a depth of about 1,700 ft. Three-component magnetometer logging in drill hole WT-2 located about 2,700 ft east of the Ghost Dance Fault shows that the Topopah Spring Tuff is strongly polarized magnetically in this area, so that fault brecciation of a vertical zone within the Tuff could provide an average negative magnetic contrast of the 4 Am{sup {minus}1} needed to produce the 400 nT low observed at the surface.« less

Temporal performance of amorphous selenium mammography detectors

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

Zhao Bo; Zhao Wei

2005-01-01

We investigated temporal performance of amorphous selenium (a-Se) detectors specifically designed for mammographic imaging. Our goal is to quantify the inherent lag and ghosting of a-Se photoconductor as a function of imaging conditions. Two small area electroded a-Se samples, one positively and the other negatively biased on the entrance side of x rays, were used in the experiments. The study of lag and ghosting was performed by delivering a number of raw exposures as experienced in screening mammography to the samples at different electric field strength E{sub Se} while measuring the current through the a-Se sample. Ghosting at different operationalmore » conditions was quantified as the percentage x-ray sensitivity (x-ray generated photocurrent measured from the sample) reduction compared to before irradiation. Lag was determined by measuring the residual current of a-Se at a given time after the end of each x-ray exposure. Both lag and ghosting were measured as a function of E{sub Se} and cumulative exposure. The values of E{sub Se} used in our experiments ranged from 1 to 20 V/{mu}m. It was found that ghosting increases with exposure and decreases with E{sub Se} for both samples because of the dominant effect of recombination between trapped electrons and x-ray generated holes. Lag on the other hand has different dependence on E{sub Se} and cumulative exposure. At E{sub Se}{<=}10 V/{mu}m, the first frame lag for both samples changed slowly with cumulative exposure, with a range of 0.2%-1.7% for the positively biased sample and 0.5%-8% for the negatively biased sample. Overall the positively biased sample has better temporal performance than the negatively biased sample due to the lower density of trapped electrons. The impact of time interval between exposures on the temporal performance was also investigated. Recovery of ghosting with longer time interval was observed, which was attributed to the neutralization of trapped electrons by injected holes through dark current.« less

Effective gravitational couplings for cosmological perturbations in generalized Proca theories

NASA Astrophysics Data System (ADS)

De Felice, Antonio; Heisenberg, Lavinia; Kase, Ryotaro; Mukohyama, Shinji; Tsujikawa, Shinji; Zhang, Ying-li

2016-08-01

We consider the finite interactions of the generalized Proca theory including the sixth-order Lagrangian and derive the full linear perturbation equations of motion on the flat Friedmann-Lemaître-Robertson-Walker background in the presence of a matter perfect fluid. By construction, the propagating degrees of freedom (besides the matter perfect fluid) are two transverse vector perturbations, one longitudinal scalar, and two tensor polarizations. The Lagrangians associated with intrinsic vector modes neither affect the background equations of motion nor the second-order action of tensor perturbations, but they do give rise to nontrivial modifications to the no-ghost condition of vector perturbations and to the propagation speeds of vector and scalar perturbations. We derive the effective gravitational coupling Geff with matter density perturbations under a quasistatic approximation on scales deep inside the sound horizon. We find that the existence of intrinsic vector modes allows a possibility for reducing Geff. In fact, within the parameter space, Geff can be even smaller than the Newton gravitational constant G at the late cosmological epoch, with a peculiar phantom dark energy equation of state (without ghosts). The modifications to the slip parameter η and the evolution of the growth rate f σ8 are discussed as well. Thus, dark energy models in the framework of generalized Proca theories can be observationally distinguished from the Λ CDM model according to both cosmic growth and expansion history. Furthermore, we study the evolution of vector perturbations and show that outside the vector sound horizon the perturbations are nearly frozen and start to decay with oscillations after the horizon entry.

Nonlinear analysis for dual-frequency concurrent energy harvesting

NASA Astrophysics Data System (ADS)

Yan, Zhimiao; Lei, Hong; Tan, Ting; Sun, Weipeng; Huang, Wenhu

2018-05-01

The dual-frequency responses of the hybrid energy harvester undergoing the base excitation and galloping were analyzed numerically. In this work, an approximate dual-frequency analytical method is proposed for the nonlinear analysis of such a system. To obtain the approximate analytical solutions of the full coupled distributed-parameter model, the forcing interactions is first neglected. Then, the electromechanical decoupled governing equation is developed using the equivalent structure method. The hybrid mechanical response is finally separated to be the self-excited and forced responses for deriving the analytical solutions, which are confirmed by the numerical simulations of the full coupled model. The forced response has great impacts on the self-excited response. The boundary of Hopf bifurcation is analytically determined by the onset wind speed to galloping, which is linearly increased by the electrical damping. Quenching phenomenon appears when the increasing base excitation suppresses the galloping. The theoretical quenching boundary depends on the forced mode velocity. The quenching region increases with the base acceleration and electrical damping, but decreases with the wind speed. Superior to the base-excitation-alone case, the existence of the aerodynamic force protects the hybrid energy harvester at resonance from damages caused by the excessive large displacement. From the view of the harvested power, the hybrid system surpasses the base-excitation-alone system or the galloping-alone system. This study advances our knowledge on intrinsic nonlinear dynamics of the dual-frequency energy harvesting system by taking advantage of the analytical solutions.

Ghost busting: PT-symmetric interpretation of the Lee model

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

Bender, Carl M.; Brandt, Sebastian F.; Chen, J.-H.

2005-01-15

The Lee model was introduced in the 1950s as an elementary quantum field theory in which mass, wave function, and charge renormalization could be carried out exactly. In early studies of this model it was found that there is a critical value of g{sup 2}, the square of the renormalized coupling constant, above which g{sub 0}{sup 2}, the square of the unrenormalized coupling constant, is negative. Thus, for g{sup 2} larger than this critical value, the Hamiltonian of the Lee model becomes non-Hermitian. It was also discovered that in this non-Hermitian regime a new state appears whose norm is negative.more » This state is called a ghost state. It has always been assumed that in this ghost regime the Lee model is an unacceptable quantum theory because unitarity appears to be violated. However, in this regime while the Hamiltonian is not Hermitian, it does possess PT symmetry. It has recently been discovered that a non-Hermitian Hamiltonian having PT symmetry may define a quantum theory that is unitary. The proof of unitarity requires the construction of a new time-independent operator called C. In terms of C one can define a new inner product with respect to which the norms of the states in the Hilbert space are positive. Furthermore, it has been shown that time evolution in such a theory is unitary. In this paper the C operator for the Lee model in the ghost regime is constructed in the V/N{theta} sector. It is then shown that the ghost state has a positive norm and that the Lee model is an acceptable unitary quantum field theory for all values of g{sup 2}.« less

Honorary and ghost authorship in nursing publications.

PubMed

Kennedy, Maureen Shawn; Barnsteiner, Jane; Daly, John

2014-11-01

The purposes of this study were to (a) assess the prevalence of articles with honorary authors and ghost authors in 10 leading peer-reviewed nursing journals between 2010 to 2012; (b) compare the results to prevalence reported by authors of articles published in high-impact medical journals; and (c) assess the experiences of editors in the International Academy of Nursing Editors with honorary and guest authorship. Corresponding authors of articles published in 10 nursing journals between 2010 and 2012 were invited to complete an online survey about the contributions of coauthors to see if the International Committee of Medical Journal Editors () criteria for authorship were met. Additionally, members of the International Academy of Nursing Editors were invited to complete an online survey about their experiences in identifying honorary or ghost authors in articles submitted for publication. The prevalence of articles published in 10 nursing journals with honorary authors was 42%, and the prevalence of ghost authorship was 27.6%. This is a greater prevalence than what has been reported among medical journals. Qualitative data yielded five themes: lack of awareness around the rules for authorship; acknowledged need for debate, discussion, and promotion of ethical practice; knowingly tolerating, and sometimes deliberately promoting, transgressions in practice; power relations and expectations; and avoiding scrutiny. Among the 60 respondents to the editor survey, 22 (36.7%) reported identifying honorary authors and 13 (21.7%) reported ghost authors among papers submitted to their publications. Inappropriate authorship is a significant problem among scholarly nursing publications. If nursing scholarship is to maintain integrity and be considered trustworthy, and if publications are to be a factor in professional advancement, editors, nursing leaders, and faculty need to disseminate and adhere to ethical authorship practices. © 2014 Sigma Theta Tau International.

Four-Photon Imaging with Thermal Light

NASA Astrophysics Data System (ADS)

Wen, Feng; Xue, Xinxin; Zhang, Xun; Yuan, Chenzhi; Sun, Jia; Song, Jianping; Zhang, Yanpeng

2014-10-01

In a near-field four-photon correlation measurement, ghost imaging with classical incoherent light is investigated. By applying the Klyshko advanced-wave picture, we consider the properties of four-photon spatial correlation and find that the fourth-order spatial correlation function can be decomposed into multiple lower-order correlation functions. On the basis of the spatial correlation properties, a proof-of-principle four-photon ghost imaging is proposed, and the effect of each part in a fourth-order correlation function on imaging is also analyzed. In addition, the similarities and differences among ghost imaging by fourth-, second-, and third-order correlations are also discussed. It is shown that the contrast and visibility of fourth-order correlated imaging are improved significantly, while the resolution is unchanged. Such studies can be very useful in better understanding multi photon interference and multi-channel correlation imaging.

Tackling higher derivative ghosts with the Euclidean path integral

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

Fontanini, Michele; Department of Physics, Syracuse University, Syracuse, New York 13244; Trodden, Mark

2011-05-15

An alternative to the effective field theory approach to treat ghosts in higher derivative theories is to attempt to integrate them out via the Euclidean path integral formalism. It has been suggested that this method could provide a consistent framework within which we might tolerate the ghost degrees of freedom that plague, among other theories, the higher derivative gravity models that have been proposed to explain cosmic acceleration. We consider the extension of this idea to treating a class of terms with order six derivatives, and find that for a general term the Euclidean path integral approach works in themore » most trivial background, Minkowski. Moreover we see that even in de Sitter background, despite some difficulties, it is possible to define a probability distribution for tensorial perturbations of the metric.« less

Running coupling constant from lattice studies of gluon and ghost propagators

NASA Astrophysics Data System (ADS)

Cucchieri, A.; Mendes, T.

2004-12-01

We present a numerical study of the running coupling constant in four-dimensional pure-SU(2) lattice gauge theory. The running coupling is evaluated by fitting data for the gluon and ghost propagators in minimal Landau gauge. Following Refs. [1, 2], the fitting formulae are obtained by a simultaneous integration of the β function and of a function coinciding with the anomalous dimension of the propagator in the momentum subtraction scheme. We consider these formulae at three and four loops. The fitting method works well, especially for the ghost case, for which statistical error and hyper-cubic effects are very small. Our present result for ΛMS is 200-40+60 MeV, where the error is purely systematic. We are currently extending this analysis to five loops in order to reduce this systematic error.

Cosmological perturbations through a non-singular ghost-condensate/Galileon bounce

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

Battarra, Lorenzo; Koehn, Michael; Lehners, Jean-Luc

2014-07-01

We study the propagation of super-horizon cosmological perturbations in a non-singular bounce spacetime. The model we consider combines a ghost condensate with a Galileon term in order to induce a ghost-free bounce. Our calculation is performed in harmonic gauge, which ensures that the linearized equations of motion remain well-defined and non-singular throughout. We find that, despite the fact that near the bounce the speed of sound becomes imaginary, super-horizon curvature perturbations remain essentially constant across the bounce. In fact, we show that there is a time close to the bounce where curvature perturbations of all wavelengths are required to bemore » momentarily exactly constant. We relate our calculations to those performed in other gauges, and comment on the relation to previous results in the literature.« less

Covariantized vector Galileons

NASA Astrophysics Data System (ADS)

Hull, Matthew; Koyama, Kazuya; Tasinato, Gianmassimo

2016-03-01

Vector Galileons are ghost-free systems containing higher derivative interactions of vector fields. They break the vector gauge symmetry, and the dynamics of the longitudinal vector polarizations acquire a Galileon symmetry in an appropriate decoupling limit in Minkowski space. Using an Arnowitt-Deser-Misner approach, we carefully reconsider the coupling with gravity of vector Galileons, with the aim of studying the necessary conditions to avoid the propagation of ghosts. We develop arguments that put on a more solid footing the results previously obtained in the literature. Moreover, working in analogy with the scalar counterpart, we find indications for the existence of a "beyond Horndeski" theory involving vector degrees of freedom that avoids the propagation of ghosts thanks to secondary constraints. In addition, we analyze a Higgs mechanism for generating vector Galileons through spontaneous symmetry breaking, and we present its consistent covariantization.

Cosmology in bimetric theory with an effective composite coupling to matter

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

Gümrükçüoğlu, A. Emir; Heisenberg, Lavinia; Mukohyama, Shinji

We study the cosmology of bimetric theory with a composite matter coupling. We find two possible branches of background evolution. We investigate the question of stability of cosmological perturbations. For the tensor and vector perturbations, we derive conditions on the absence of ghost and gradient instabilities. For the scalar modes, we obtain conditions for avoiding ghost degrees. In the first branch, we find that one of the scalar modes becomes a ghost at the late stages of the evolution. Conversely, this problem can be avoided in the second branch. However, we also find that the constraint for the second branchmore » prevents the doubly coupled matter fields from being the standard ingredients of cosmology. We thus conclude that a realistic and stable cosmological model requires additional minimally coupled matter fields.« less

The Ghosts of Higher Education Reform: On the Organisational Processes Surrounding Policy Borrowing

ERIC Educational Resources Information Center

Brøgger, Katja

2014-01-01

The Bologna Process is one of the most extensive examples of policy borrowing processes. Based on qualitative data, this article argues in favour of studying part of this process as "global smallness", centring on the organisational effects of the implementation of a globalised curriculum. Through Derrida's notion on hauntology,…

Periodic diffraction correlation imaging without a beam-splitter.

PubMed

Li, Hu; Chen, Zhipeng; Xiong, Jin; Zeng, Guihua

2012-01-30

In this paper, we proposed and demonstrated a new correlation imaging mechanism based on the periodic diffraction effect. In this effect, a periodic intensity pattern is generated at the output surface of a periodic point source array. This novel correlation imaging mechanism can realize super-resolution imaging, Nth-order ghost imaging without a beam-splitter and correlation microscopy.

Symplectic Quantization of a Vector-Tensor Gauge Theory with Topological Coupling

NASA Astrophysics Data System (ADS)

Barcelos-Neto, J.; Silva, M. B. D.

We use the symplectic formalism to quantize a gauge theory where vectors and tensors fields are coupled in a topological way. This is an example of reducible theory and a procedure like of ghosts-of-ghosts of the BFV method is applied but in terms of Lagrange multipliers. Our final results are in agreement with the ones found in the literature by using the Dirac method.

BRST Formalism for Systems with Higher Order Derivatives of Gauge Parameters

NASA Astrophysics Data System (ADS)

Nirov, Kh. S.

For a wide class of mechanical systems, invariant under gauge transformations with arbitrary higher order time derivatives of gauge parameters, the equivalence of Lagrangian and Hamiltonian BRST formalisms is proved. It is shown that the Ostrogradsky formalism establishes the natural rules to relate the BFV ghost canonical pairs with the ghosts and antighosts introduced by the Lagrangian approach. Explicit relation between corresponding gauge-fixing terms is obtained.

Neutrinos: Nature's Ghosts?

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

Lincoln, Don

2013-06-18

Dr. Don Lincoln introduces one of the most fascinating inhabitants of the subatomic realm: the neutrino. Neutrinos are ghosts of the microworld, almost not interacting at all. In this video, he describes some of their properties and how they were discovered. Studies of neutrinos are expected to be performed at many laboratories across the world and to form one of the cornerstones of the Fermilab research program for the next decade or more.

Cascading gravity is ghost free

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

Rham, Claudia de; Khoury, Justin; Tolley, Andrew J.

2010-06-15

We perform a full perturbative stability analysis of the 6D cascading gravity model in the presence of 3-brane tension. We demonstrate that for sufficiently large tension on the (flat) 3-brane, there are no ghosts at the perturbative level, consistent with results that had previously only been obtained in a specific 5D decoupling limit. These results establish the cascading gravity framework as a consistent infrared modification of gravity.

Neutrinos: Nature's Ghosts?

ScienceCinema

Lincoln, Don

2018-06-07

Dr. Don Lincoln introduces one of the most fascinating inhabitants of the subatomic realm: the neutrino. Neutrinos are ghosts of the microworld, almost not interacting at all. In this video, he describes some of their properties and how they were discovered. Studies of neutrinos are expected to be performed at many laboratories across the world and to form one of the cornerstones of the Fermilab research program for the next decade or more.

Australia Ama Ata Aidoo's Diagnose and Representation of the Dilemma of the African American Diaspora in Her Play "Dilemma of a Ghost"

ERIC Educational Resources Information Center

Al-Khafaji, Ammar Shamil Kadhim

2018-01-01

The research investigates in details about the influence of cultural differences in Postcolonial Ghana as presented in Ama Ata Aidoo's "Dilemma of a Ghost". The play centers on the cross cultural marriage of young couple; Ato Yawson, a Ghanaian who recently completed his studies in the United States and returns home, and Eulali, his…

The modified gap excess ratio (GER*) and the stratigraphic congruence of dinosaur phylogenies.

PubMed

Wills, Matthew A; Barrett, Paul M; Heathcote, Julia F

2008-12-01

Palaeontologists routinely map their cladograms onto what is known of the fossil record. Where sister taxa first appear as fossils at different times, a ghost range is inferred to bridge the gap between these dates. Some measure of the total extent of ghost ranges across the tree underlies several indices of cladistic/stratigraphic congruence. We investigate this congruence for 19 independent, published cladograms of major dinosaur groups and report exceptional agreement between the phylogenetic and stratigraphic patterns, evidenced by sums of ghost ranges near the theoretical minima. This implies that both phylogenetic and stratigraphic data reflect faithfully the evolutionary history of dinosaurs, at least for the taxa included in this study. We formally propose modifications to an existing index of congruence (the gap excess ratio; GER), designed to remove a bias in the range of values possible with trees of different shapes. We also propose a more informative index of congruence--GER*--that takes account of the underlying distribution of sums of ghost ranges possible when permuting stratigraphic range data across the tree. Finally, we incorporate data on the range of possible first occurrence dates into our estimates of congruence, extending a procedure originally implemented with the modified Manhattan stratigraphic measure and GER to our new indices. Most dinosaur data sets maintain extremely high congruence despite such modifications.

A New Ghost Cell/Level Set Method for Moving Boundary Problems: Application to Tumor Growth

PubMed Central

Macklin, Paul

2011-01-01

In this paper, we present a ghost cell/level set method for the evolution of interfaces whose normal velocity depend upon the solutions of linear and nonlinear quasi-steady reaction-diffusion equations with curvature-dependent boundary conditions. Our technique includes a ghost cell method that accurately discretizes normal derivative jump boundary conditions without smearing jumps in the tangential derivative; a new iterative method for solving linear and nonlinear quasi-steady reaction-diffusion equations; an adaptive discretization to compute the curvature and normal vectors; and a new discrete approximation to the Heaviside function. We present numerical examples that demonstrate better than 1.5-order convergence for problems where traditional ghost cell methods either fail to converge or attain at best sub-linear accuracy. We apply our techniques to a model of tumor growth in complex, heterogeneous tissues that consists of a nonlinear nutrient equation and a pressure equation with geometry-dependent jump boundary conditions. We simulate the growth of glioblastoma (an aggressive brain tumor) into a large, 1 cm square of brain tissue that includes heterogeneous nutrient delivery and varied biomechanical characteristics (white matter, gray matter, cerebrospinal fluid, and bone), and we observe growth morphologies that are highly dependent upon the variations of the tissue characteristics—an effect observed in real tumor growth. PMID:21331304

Ghost features in Doppler-broadened spectra of rovibrational transitions in trapped HD+ ions

NASA Astrophysics Data System (ADS)

Patra, Sayan; Koelemeij, J. C. J.

2017-02-01

Doppler broadening plays an important role in laser rovibrational spectroscopy of trapped deuterated molecular hydrogen ions (HD+), even at the millikelvin temperatures achieved through sympathetic cooling by laser-cooled beryllium ions. Recently, Biesheuvel et al. (2016) presented a theoretical lineshape model for such transitions which not only considers linestrengths and Doppler broadening, but also the finite sample size and population redistribution by blackbody radiation, which are important in view of the long storage and probe times achievable in ion traps. Here, we employ the rate equation model developed by Biesheuvel et al. to theoretically study the Doppler-broadened hyperfine structure of the (v, L) : (0, 3) → (4, 2) rovibrational transition in HD+ at 1442 nm. We observe prominent yet hitherto unrecognized ghost features in the simulated spectrum, whose positions depend on the Doppler width, transition rates, and saturation levels of the hyperfine components addressed by the laser. We explain the origin and behavior of such features, and we provide a simple quantitative guideline to assess whether ghost features may appear. As such ghost features may be common to saturated Doppler-broadened spectra of rotational and vibrational transitions in trapped ions composed of partly overlapping lines, our work illustrates the necessity to use lineshape models that take into account all the relevant physics.

Polymer quantization, stability and higher-order time derivative terms

NASA Astrophysics Data System (ADS)

Cumsille, Patricio; Reyes, Carlos M.; Ossandon, Sebastian; Reyes, Camilo

2016-03-01

The possibility that fundamental discreteness implicit in a quantum gravity theory may act as a natural regulator for ultraviolet singularities arising in quantum field theory has been intensively studied. Here, along the same expectations, we investigate whether a nonstandard representation called polymer representation can smooth away the large amount of negative energy that afflicts the Hamiltonians of higher-order time derivative theories, rendering the theory unstable when interactions come into play. We focus on the fourth-order Pais-Uhlenbeck model which can be reexpressed as the sum of two decoupled harmonic oscillators one producing positive energy and the other negative energy. As expected, the Schrödinger quantization of such model leads to the stability problem or to negative norm states called ghosts. Within the framework of polymer quantization we show the existence of new regions where the Hamiltonian can be defined well bounded from below.

Influence of lubrication forces in direct numerical simulations of particle-laden flows

NASA Astrophysics Data System (ADS)

Maitri, Rohit; Peters, Frank; Padding, Johan; Kuipers, Hans

2016-11-01

Accurate numerical representation of particle-laden flows is important for fundamental understanding and optimizing the complex processes such as proppant transport in fracking. Liquid-solid flows are fundamentally different from gas-solid flows because of lower density ratios (solid to fluid) and non-negligible lubrication forces. In this interface resolved model, fluid-solid coupling is achieved by incorporating the no-slip boundary condition implicitly at particle's surfaces by means of an efficient second order ghost-cell immersed boundary method. A fixed Eulerian grid is used for solving the Navier-Stokes equations and the particle-particle interactions are implemented using the soft sphere collision and sub-grid scale lubrication model. Due to the range of influence of lubrication force on a smaller scale than the grid size, it is important to implement the lubrication model accurately. In this work, different implementations of the lubrication model on particle dynamics are studied for various flow conditions. The effect of a particle surface roughness on lubrication force and the particle transport is also investigated. This study is aimed at developing a validated methodology to incorporate lubrication models in direct numerical simulation of particle laden flows. This research is supported from Grant 13CSER014 of the Foundation for Fundamental Research on Matter (FOM), which is part of the Netherlands Organisation for Scientific Research (NWO).

Spiral Imaging in fMRI

PubMed Central

Glover, Gary H.

2011-01-01

T2*-weighted Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) requires efficient acquisition methods in order to fully sample the brain in a several second time period. The most widely used approach is Echo Planar Imaging (EPI), which utilizes a Cartesian trajectory to cover k-space. This trajectory is subject to ghosts from off-resonance and gradient imperfections and is intrinsically sensitive to cardiac-induced pulsatile motion from substantial first- and higher order moments of the gradient waveform near the k-space origin. In addition, only the readout direction gradient contributes significant energy to the trajectory. By contrast, the Spiral method samples k-space with an Archimedean or similar trajectory that begins at the k-space center and spirals to the edge (Spiral-out), or its reverse, ending at the origin (Spiral-in). Spiral methods have reduced sensitivity to motion, shorter readout times, improved signal recovery in most frontal and parietal brain regions, and exhibit blurring artifacts instead of ghosts or geometric distortion. Methods combining Spiral-in and Spiral-out trajectories have further advantages in terms of diminished susceptibility-induced signal dropout and increased BOLD signal. In measurements of temporal signal to noise ratio measured in 8 subjects, Spiral-in/out exhibited significant increases over EPI in voxel volumes recovered in frontal and whole brain regions (18% and 10%, respectively). PMID:22036995

On the stability conditions for theories of modified gravity in the presence of matter fields

NASA Astrophysics Data System (ADS)

De Felice, Antonio; Frusciante, Noemi; Papadomanolakis, Georgios

2017-03-01

We present a thorough stability analysis of modified gravity theories in the presence of matter fields. We use the Effective Field Theory framework for Dark Energy and Modified Gravity to retain a general approach for the gravity sector and a Sorkin-Schutz action for the matter one. Then, we work out the proper viability conditions to guarantee in the scalar sector the absence of ghosts, gradient and tachyonic instabilities. The absence of ghosts can be achieved by demanding a positive kinetic matrix, while the lack of a gradient instability is ensured by imposing a positive speed of propagation for all the scalar modes. In case of tachyonic instability, the mass eigenvalues have been studied and we work out the appropriate expressions. For the latter, an instability occurs only when the negative mass eigenvalue is much larger, in absolute value, than the Hubble parameter. We discuss the results for the minimally coupled quintessence model showing for a particular set of parameters two typical behaviours which in turn lead to a stable and an unstable configuration. Moreover, we find that the speeds of propagation of the scalar modes strongly depend on matter densities, for the beyond Horndeski theories. Our findings can be directly employed when testing modified gravity theories as they allow to identify the correct viability space.

Energy-harvesting laser phosphor display and its design considerations

NASA Astrophysics Data System (ADS)

Fujieda, Ichiro; Itaya, Shunsuke; Ohta, Masamichi; Hirai, Yuuki; Kohmoto, Takamasa

2017-04-01

One can convert a luminescent solar concentrator to a display by projecting intensity-modulated light on it. We fabricated a 95 mm×95 mm×10 mm screen by sandwiching a thin coumarin 6 layer with two acrylic plates. We removed the light source in a commercial projector and fed a blue laser beam into its optics. It displayed monochrome images on the screen clearly. A photodiode covered a 10 mm×10 mm region on the edge surface of the screen. As we pulsed the laser, the photodiode output varied synchronously. Its output indicates that a fully covered version would harvest up to 71% of the incoming laser power. However, a ghost image was noticeable when we displayed a high-contrast still image. We address two aspects in design considerations. First, tiling small modules will reduce the thickness of a large-area projection system and alleviate its self-absorption loss. For seamless tiling, we can attach output couplers to the surface of the transparent plate and extract photoluminescence (PL) photons in each module. Second, the origin of the ghost image is the PL photons reflected at the plate-air interface inside the screen. Thinning the transparent plate facing the projector will eliminate such an optical cross talk.

Phase-resolved fluid dynamic forces of a flapping foil energy harvester based on PIV measurements

NASA Astrophysics Data System (ADS)

Liburdy, James

2017-11-01

Two-dimensional particle image velocimetry measurements are performed in a wind tunnel to evaluate the spatial and temporal fluid dynamic forces acting on a flapping foil operating in the energy harvesting regime. Experiments are conducted at reduced frequencies (k = fc/U) of 0.05 - 0.2, pitching angle of, and heaving amplitude of A / c = 0.6. The phase-averaged pressure field is obtained by integrating the pressure Poisson equation. Fluid dynamic forces are then obtained through the integral momentum equation. Results are compared with a simple force model based on the concept of flow impulse. These results help to show the detailed force distributions, their transient nature and aide in understanding the impact of the fluid flow structures that contribute to the power production.

Cosmic acceleration and the helicity-0 graviton

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

Rham, Claudia de; Heisenberg, Lavinia; Gabadadze, Gregory

2011-05-15

We explore cosmology in the decoupling limit of a nonlinear covariant extension of Fierz-Pauli massive gravity obtained recently in arXiv:1007.0443. In this limit the theory is a scalar-tensor model of a unique form defined by symmetries. We find that it admits a self-accelerated solution, with the Hubble parameter set by the graviton mass. The negative pressure causing the acceleration is due to a condensate of the helicity-0 component of the massive graviton, and the background evolution, in the approximation used, is indistinguishable from the {Lambda}CDM model. Fluctuations about the self-accelerated background are stable for a certain range of parameters involved.more » Most surprisingly, the fluctuation of the helicity-0 field above its background decouples from an arbitrary source in the linearized theory. We also show how massive gravity can remarkably screen an arbitrarily large cosmological constant in the decoupling limit, while evading issues with ghosts. The obtained static solution is stable against small perturbations, suggesting that the degravitation of the vacuum energy is possible in the full theory. Interestingly, however, this mechanism postpones the Vainshtein effect to shorter distance scales. Hence, fifth force measurements severely constrain the value of the cosmological constant that can be neutralized, making this scheme phenomenologically not viable for solving the old cosmological constant problem. We briefly speculate on a possible way out of this issue.« less

Ghost vertices for the bosonic string using the group-theoretic approach to string theory

NASA Astrophysics Data System (ADS)

Freeman, M. D.; West, P.

1988-04-01

The N-string tree-level scattering vertices for the bosonic string are extended to include anticommuting (ghost) oscillators. These vertices behave correctly under the action of the BRST charge Q and reproduce the known results for the scattering of physical states. This work is an application of the group-theoretic approach to string theory. Permanent address: Mathematics Department, King's College, Strand, London WC2R 2LS, UK.

The ghost of Helioth and his stereoscope: the return of a phantom.

PubMed

Wade, Nicholas J

2012-01-01

Among the myths surrounding the invention of the stereoscope, that of Helioth stands as a supreme example of shoddy scholarship and its subsequent dissemination. Helioth was said to have made a simple stereoscope before Wheatstone presented his mirror stereoscope to the public in 1838. There is no evidence of Helioth's existence prior to a report in the mid-twentieth century, and despite attempts to dispel his ghost it has recently resurfaced.

Hot Corrosion Degradation of Metals and Alloys - A Unified Theory

DTIC Science & Technology

1979-06-01

microscope, electron beam microprobe and X-ray diffraction. REULTS AND DMCtESION Hot Corrosion Degradation Sectuence In attempting to develop a unified...Figure 40a. Such ghost images, which can be called corrosion front ghosts , appear as sequential dark and light zones in electron backscatter images... Electronic and Solid State Sciences AUG Ill 1979I Bolling AFB, D.C. 20332 ID PRATT &WHITNEY ARCRAFT GROUP P.O . Box 2861 /Government Products Division wi

Predicting financial market crashes using ghost singularities.

PubMed

Smug, Damian; Ashwin, Peter; Sornette, Didier

2018-01-01

We analyse the behaviour of a non-linear model of coupled stock and bond prices exhibiting periodically collapsing bubbles. By using the formalism of dynamical system theory, we explain what drives the bubbles and how foreshocks or aftershocks are generated. A dynamical phase space representation of that system coupled with standard multiplicative noise rationalises the log-periodic power law singularity pattern documented in many historical financial bubbles. The notion of 'ghosts of finite-time singularities' is introduced and used to estimate the end of an evolving bubble, using finite-time singularities of an approximate normal form near the bifurcation point. We test the forecasting skill of this method on different stochastic price realisations and compare with Monte Carlo simulations of the full system. Remarkably, the approximate normal form is significantly more precise and less biased. Moreover, the method of ghosts of singularities is less sensitive to the noise realisation, thus providing more robust forecasts.

Predicting financial market crashes using ghost singularities

PubMed Central

2018-01-01

We analyse the behaviour of a non-linear model of coupled stock and bond prices exhibiting periodically collapsing bubbles. By using the formalism of dynamical system theory, we explain what drives the bubbles and how foreshocks or aftershocks are generated. A dynamical phase space representation of that system coupled with standard multiplicative noise rationalises the log-periodic power law singularity pattern documented in many historical financial bubbles. The notion of ‘ghosts of finite-time singularities’ is introduced and used to estimate the end of an evolving bubble, using finite-time singularities of an approximate normal form near the bifurcation point. We test the forecasting skill of this method on different stochastic price realisations and compare with Monte Carlo simulations of the full system. Remarkably, the approximate normal form is significantly more precise and less biased. Moreover, the method of ghosts of singularities is less sensitive to the noise realisation, thus providing more robust forecasts. PMID:29596485

Structural character of the Ghost Dance fault, Yucca Mountain, Nevada

USGS Publications Warehouse

Spengler, R.W.; Braun, C.A.; Linden, R.M.; Martin, L.G.; Ross-Brown, D. M.; Blackburn, R.L.

1993-01-01

Detailed structural mapping of an area that straddles the southern part of the Ghost Dance Fault has revealed the presence of several additional subparallel to anastomosing faults. These faults, mapped at a scale of 1:240, are: 1) dominantly north trending, 2) present on both the upthrown and downthrown sides of the surface trace of the Ghost Dance fault, 3) near-vertical features that commonly offset strata down to the west by 3 to 6 m (10 to 20 ft), and 4) commonly spaced 15 to 46 m (50 to 150 ft) apart. The zone also exhibits a structural fabric, containing an abundance of northwest-trending fractures. The width of the zone appears to be at least 213 m (700 ft) near the southernmost boundary of the study area but remains unknown near the northern extent of the study area, where the width of the study area is only 183 m (600 ft).

Ghosts, strong coupling, and accidental symmetries in massive gravity

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

Deffayet, C.; GReCO/IAP, 98 bis boulevard Arago, 75014 Paris; Rombouts, J.-W.

2005-08-15

We show that the strong self-interaction of the scalar polarization of a massive graviton can be understood in terms of the propagation of an extra ghostlike degree of freedom, thus relating strong coupling to the sixth degree of freedom discussed by Boulware and Deser in their Hamiltonian analysis of massive gravity. This enables one to understand the Vainshtein recovery of solutions of massless gravity as being due to the effect of the exchange of this ghost, which gets frozen at distances larger than the Vainshtein radius. Inside this region, we can trust the two-field Lagrangian perturbatively, while at larger distancesmore » one can use the higher derivative formulation. We also compare massive gravity with other models, namely, deconstructed theories of gravity, as well as the Dvali-Gabadadze-Porrati model. In the latter case, we argue that the Vainshtein recovery process is of a different nature, not involving a ghost degree of freedom.« less

Building Shadow Detection from Ghost Imagery

NASA Astrophysics Data System (ADS)

Zhou, G.; Sha, J.; Yue, T.; Wang, Q.; Liu, X.; Huang, S.; Pan, Q.; Wei, J.

2018-05-01

Shadow is one of the basic features of remote sensing image, it expresses a lot of information of the object which is loss or interference, and the removal of shadow is always a difficult problem to remote sensing image processing. In this paper, it is mainly analyzes the characteristics and properties of shadows from the ghost image (traditional orthorectification). The DBM and the interior and exterior orientation elements of the image are used to calculate the zenith angle of sun. Then this paper combines the scope of the architectural shadows which has be determined by the zenith angle of sun with the region growing method to make the detection of architectural shadow areas. This method lays a solid foundation for the shadow of the repair from the ghost image later. It will greatly improve the accuracy of shadow detection from buildings and make it more conducive to solve the problem of urban large-scale aerial imagines.

Bigravity from gradient expansion

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

Yamashita, Yasuho; Tanaka, Takahiro; Department of Physics, Kyoto University,606-8502, Kyoto

2016-05-04

We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The bulk configuration is solved for given boundary metrics, and it is substituted back into the action to obtain the effective four-dimensional action. In order to obtain the ghost-free bigravity, we consider the gradient expansion in which the brane separation is supposed to be sufficiently small so that two boundary metrics are almost identical. The obtained effective theory is shown to be ghost free as expected, however, the interaction between two gravitons takesmore » the Fierz-Pauli form at the leading order of the gradient expansion, even though we do not use the approximation of linear perturbation. We also find that the radion remains as a scalar field in the four-dimensional effective theory, but its coupling to the metrics is non-trivial.« less

Non-minimal derivative couplings of the composite metric

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

Heisenberg, Lavinia, E-mail: laviniah@kth.se

2015-11-01

In the context of massive gravity, bi-gravity and multi-gravity non-minimal matter couplings via a specific composite effective metric were investigated recently. Even if these couplings generically reintroduce the Boulware-Deser ghost, this composite metric is unique in the sense that the ghost reemerges only beyond the decoupling limit and the matter quantum loop corrections do not detune the potential interactions. We consider non-minimal derivative couplings of the composite metric to matter fields for a specific subclass of Horndeski scalar-tensor interactions. We first explore these couplings in the mini-superspace and investigate in which scenario the ghost remains absent. We further study thesemore » non-minimal derivative couplings in the decoupling-limit of the theory and show that the equation of motion for the helicity-0 mode remains second order in derivatives. Finally, we discuss preliminary implications for cosmology.« less

Non-minimal derivative couplings of the composite metric

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

Heisenberg, Lavinia; Department of Physics & The Oskar Klein Centre,AlbaNova University Centre, 10691 Stockholm

2015-11-04

In the context of massive gravity, bi-gravity and multi-gravity non-minimal matter couplings via a specific composite effective metric were investigated recently. Even if these couplings generically reintroduce the Boulware-Deser ghost, this composite metric is unique in the sense that the ghost reemerges only beyond the decoupling limit and the matter quantum loop corrections do not detune the potential interactions. We consider non-minimal derivative couplings of the composite metric to matter fields for a specific subclass of Horndeski scalar-tensor interactions. We first explore these couplings in the mini-superspace and investigate in which scenario the ghost remains absent. We further study thesemore » non-minimal derivative couplings in the decoupling-limit of the theory and show that the equation of motion for the helicity-0 mode remains second order in derivatives. Finally, we discuss preliminary implications for cosmology.« less

Optimisation of a low cost SLM for diffraction efficiency and ghost order suppression

NASA Astrophysics Data System (ADS)

Bowman, R.; D'Ambrosio, V.; Rubino, E.; Jedrkiewicz, O.; di Trapani, P.; Padgett, M. J.

2011-11-01

Spatial Light Modulators (SLMs) are a powerful tool in many optics laboratories, but due to the technology required for their fabrication, they are usually very expensive. Recently some inexpensive devices have been produced, however their phase shift range is less than 2π, leading to a loss of diffraction efficiency for the SLM. We show how to improve the first order diffraction efficiency of such an SLM by adjusting the blazing function, and obtain a 1.5 times increase in first order diffracted power. Even a perfect SLM with 2π phase throw can produce undesired effects in some situations; for example in holographic optical tweezers it is common to find unwanted "ghost spots" near to the array of first-order spots. Modulating the amplitude, by spatially modulating the blazing function, allows us to suppress the ghost spots. This increases the contrast between desired and unwanted spots by more than an order of magnitude.

Massless spinning particle and null-string on AdS d : projective-space approach

NASA Astrophysics Data System (ADS)

Uvarov, D. V.

2018-07-01

The massless spinning particle and the tensionless string models on an AdS d background in the projective-space realization are proposed as constrained Hamiltonian systems. Various forms of particle and string Lagrangians are derived and classical mechanics is studied including the Lax-type representation of the equations of motion. After that, the transition to the quantum theory is discussed. The analysis of potential anomalies in the tensionless string model necessitates the introduction of ghosts and BRST charge. It is shown that a quantum BRST charge is nilpotent for any d if coordinate-momentum ordering for the phase-space bosonic variables, Weyl ordering for the fermions and cb () ordering for the ghosts is chosen, while conformal reparametrizations and space-time dilatations turn out to be anomalous for ordering in terms of positive and negative Fourier modes of the phase-space variables and ghosts.

Gravitational effective action at second order in curvature and gravitational waves

NASA Astrophysics Data System (ADS)

Calmet, Xavier; Capozziello, Salvatore; Pryer, Daniel

2017-09-01

We consider the full effective theory for quantum gravity at second order in curvature including non-local terms. We show that the theory contains two new degrees of freedom beyond the massless graviton: namely a massive spin-2 ghost and a massive scalar field. Furthermore, we show that it is impossible to fine-tune the parameters of the effective action to eliminate completely the classical spin-2 ghost because of the non-local terms in the effective action. Being a classical field, it is not clear anyway that this ghost is problematic. It simply implies a repulsive contribution to Newton's potential. We then consider how to extract the parameters of the effective action and show that it is possible to measure, at least in principle, the parameters of the local terms independently of each other using a combination of observations of gravitational waves and measurements performed by pendulum type experiments searching for deviations of Newton's potential.

Three-dimensional ghost imaging using acoustic transducer

NASA Astrophysics Data System (ADS)

Zhang, Chi; Guo, Shuxu; Guan, Jian; Cao, Junsheng; Gao, Fengli

2016-06-01

We propose a novel three-dimensional (3D) ghost imaging method using unfocused ultrasonic transducer, where the transducer is used as the bucket detector to collect the total photoacoustic signal intensity from spherical surfaces with different radius circling the transducer. This collected signal is a time sequence corresponding to the optic absorption information on the spherical surfaces, and the values at the same moments in all the sequences are used as the bucket signals to restore the corresponding spherical images, which are assembled as the object 3D reconstruction. Numerical experiments show this method can effectively accomplish the 3D reconstruction and by adding up each sequence on time domain as a bucket signal it can also realize two dimensional (2D) ghost imaging. The influence of the measurement times on the 3D and 2D reconstruction is analyzed with Peak Signal to Noise Ratio (PSNR) as the yardstick, and the transducer as a bucket detector is also discussed.

Force-momentum-based self-guided Langevin dynamics: A rapid sampling method that approaches the canonical ensemble

NASA Astrophysics Data System (ADS)

Wu, Xiongwu; Brooks, Bernard R.

2011-11-01

The self-guided Langevin dynamics (SGLD) is a method to accelerate conformational searching. This method is unique in the way that it selectively enhances and suppresses molecular motions based on their frequency to accelerate conformational searching without modifying energy surfaces or raising temperatures. It has been applied to studies of many long time scale events, such as protein folding. Recent progress in the understanding of the conformational distribution in SGLD simulations makes SGLD also an accurate method for quantitative studies. The SGLD partition function provides a way to convert the SGLD conformational distribution to the canonical ensemble distribution and to calculate ensemble average properties through reweighting. Based on the SGLD partition function, this work presents a force-momentum-based self-guided Langevin dynamics (SGLDfp) simulation method to directly sample the canonical ensemble. This method includes interaction forces in its guiding force to compensate the perturbation caused by the momentum-based guiding force so that it can approximately sample the canonical ensemble. Using several example systems, we demonstrate that SGLDfp simulations can approximately maintain the canonical ensemble distribution and significantly accelerate conformational searching. With optimal parameters, SGLDfp and SGLD simulations can cross energy barriers of more than 15 kT and 20 kT, respectively, at similar rates for LD simulations to cross energy barriers of 10 kT. The SGLDfp method is size extensive and works well for large systems. For studies where preserving accessible conformational space is critical, such as free energy calculations and protein folding studies, SGLDfp is an efficient approach to search and sample the conformational space.

Beyond Positivity Bounds and the Fate of Massive Gravity

NASA Astrophysics Data System (ADS)

Bellazzini, Brando; Riva, Francesco; Serra, Javi; Sgarlata, Francesco

2018-04-01

We constrain effective field theories by going beyond the familiar positivity bounds that follow from unitarity, analyticity, and crossing symmetry of the scattering amplitudes. As interesting examples, we discuss the implications of the bounds for the Galileon and ghost-free massive gravity. The combination of our theoretical bounds with the experimental constraints on the graviton mass implies that the latter is either ruled out or unable to describe gravitational phenomena, let alone to consistently implement the Vainshtein mechanism, down to the relevant scales of fifth-force experiments, where general relativity has been successfully tested. We also show that the Galileon theory must contain symmetry-breaking terms that are at most one-loop suppressed compared to the symmetry-preserving ones. We comment as well on other interesting applications of our bounds.

Beyond Positivity Bounds and the Fate of Massive Gravity.

PubMed

Bellazzini, Brando; Riva, Francesco; Serra, Javi; Sgarlata, Francesco

2018-04-20

We constrain effective field theories by going beyond the familiar positivity bounds that follow from unitarity, analyticity, and crossing symmetry of the scattering amplitudes. As interesting examples, we discuss the implications of the bounds for the Galileon and ghost-free massive gravity. The combination of our theoretical bounds with the experimental constraints on the graviton mass implies that the latter is either ruled out or unable to describe gravitational phenomena, let alone to consistently implement the Vainshtein mechanism, down to the relevant scales of fifth-force experiments, where general relativity has been successfully tested. We also show that the Galileon theory must contain symmetry-breaking terms that are at most one-loop suppressed compared to the symmetry-preserving ones. We comment as well on other interesting applications of our bounds.

Ghosts in the Machine II: Neural Correlates of Memory Interference from the Previous Trial.

PubMed

Papadimitriou, Charalampos; White, Robert L; Snyder, Lawrence H

2017-04-01

Previous memoranda interfere with working memory. For example, spatial memories are biased toward locations memorized on the previous trial. We predicted, based on attractor network models of memory, that activity in the frontal eye fields (FEFs) encoding a previous target location can persist into the subsequent trial and that this ghost will then bias the readout of the current target. Contrary to this prediction, we find that FEF memory representations appear biased away from (not toward) the previous target location. The behavioral and neural data can be reconciled by a model in which receptive fields of memory neurons converge toward remembered locations, much as receptive fields converge toward attended locations. Convergence increases the resources available to encode the relevant memoranda and decreases overall error in the network, but the residual convergence from the previous trial can give rise to an attractive behavioral bias on the next trial. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

On the curious spectrum of duality invariant higher-derivative gravity

DOE PAGES

Hohm, Olaf; Naseer, Usman; Zwiebach, Barton

2016-08-31

Here, we analyze the spectrum of the exactly duality and gauge invariant higher-derivative double field theory. While this theory is based on a chiral CFT and does not correspond to a standard string theory, our analysis illuminates a number of issues central in string theory. The full quadratic action is rewritten as a two-derivative theory with additional fields. This allows for a simple analysis of the spectrum, which contains two massive spin-2 ghosts and massive scalars, in addition to the massless fields. Moreover, in this formulation, the massless or tensionless limit α' → ∞ is non-singular and leads to anmore » enhanced gauge symmetry. We show that the massive modes can be integrated out exactly at the quadratic level, leading to an infinite series of higher-derivative corrections. Lastly, we present a ghost-free massive extension of linearized double field theory, which employs a novel mass term for the dilaton and metric.« less

Ghost Particle Velocimetry: Accurate 3D Flow Visualization Using Standard Lab Equipment

NASA Astrophysics Data System (ADS)

Buzzaccaro, Stefano; Secchi, Eleonora; Piazza, Roberto

2013-07-01

We describe and test a new approach to particle velocimetry, based on imaging and cross correlating the scattering speckle pattern generated on a near-field plane by flowing tracers with a size far below the diffraction limit, which allows reconstructing the velocity pattern in microfluidic channels without perturbing the flow. As a matter of fact, adding tracers is not even strictly required, provided that the sample displays sufficiently refractive-index fluctuations. For instance, phase separation in liquid mixtures in the presence of shear is suitable to be directly investigated by this “ghost particle velocimetry” technique, which just requires a microscope with standard lamp illumination equipped with a low-cost digital camera. As a further bonus, the peculiar spatial coherence properties of the illuminating source, which displays a finite longitudinal coherence length, allows for a 3D reconstruction of the profile with a resolution of few tenths of microns and makes the technique suitable to investigate turbid samples with negligible multiple scattering effects.

Advanced Fluid System Simulation

DTIC Science & Technology

1980-04-01

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Report of the NASA lunar energy enterprise case study task force

NASA Technical Reports Server (NTRS)

1989-01-01

The Lunar Energy Enterprise Cast Study Task Force was formed to determine the economic viability and commercial business potential of mining and extracting He-3 from the lunar soil for use in earth-based fusion reactors. In addition, the Solar Power Satellite (SPS) and the Lunar Power Station (LPS) were also evaluated because they involve the use of lunar materials and could provide energy for lunar-based activities. The Task Force considered: (1) the legal and liability aspects of the space energy projects; (2) the long-range terrestrial energy needs and options; (3) the technical maturity of the three space energy projects; and (4) their commercial potential. The use of electricity is expected to increase, but emerging environmental concerns and resource availability suggest changes for the national energy policy. All three options have the potential to provide a nearly inexhaustible, clean source of electricity for the U.S. and worldwide, without major adverse impacts on the Earth's environment. Assumption by industry of the total responsibility for these energy projects is not yet possible. Pursuit of these energy concepts requires the combined efforts of government and industry. The report identifies key steps necessary for the development of these concepts and an evolving industrial role.

Scalable Failure Masking for Stencil Computations using Ghost Region Expansion and Cell to Rank Remapping

DOE PAGES

Gamell, Marc; Teranishi, Keita; Kolla, Hemanth; ...

2017-10-26

In order to achieve exascale systems, application resilience needs to be addressed. Some programming models, such as task-DAG (directed acyclic graphs) architectures, currently embed resilience features whereas traditional SPMD (single program, multiple data) and message-passing models do not. Since a large part of the community's code base follows the latter models, it is still required to take advantage of application characteristics to minimize the overheads of fault tolerance. To that end, this paper explores how recovering from hard process/node failures in a local manner is a natural approach for certain applications to obtain resilience at lower costs in faulty environments.more » In particular, this paper targets enabling online, semitransparent local recovery for stencil computations on current leadership-class systems as well as presents programming support and scalable runtime mechanisms. Also described and demonstrated in this paper is the effect of failure masking, which allows the effective reduction of impact on total time to solution due to multiple failures. Furthermore, we discuss, implement, and evaluate ghost region expansion and cell-to-rank remapping to increase the probability of failure masking. To conclude, this paper shows the integration of all aforementioned mechanisms with the S3D combustion simulation through an experimental demonstration (using the Titan system) of the ability to tolerate high failure rates (i.e., node failures every five seconds) with low overhead while sustaining performance at large scales. In addition, this demonstration also displays the failure masking probability increase resulting from the combination of both ghost region expansion and cell-to-rank remapping.« less

New ghost-node method for linking different models with varied grid refinement

USGS Publications Warehouse

James, S.C.; Dickinson, J.E.; Mehl, S.W.; Hill, M.C.; Leake, S.A.; Zyvoloski, G.A.; Eddebbarh, A.-A.

2006-01-01

A flexible, robust method for linking grids of locally refined ground-water flow models constructed with different numerical methods is needed to address a variety of hydrologic problems. This work outlines and tests a new ghost-node model-linking method for a refined "child" model that is contained within a larger and coarser "parent" model that is based on the iterative method of Steffen W. Mehl and Mary C. Hill (2002, Advances in Water Res., 25, p. 497-511; 2004, Advances in Water Res., 27, p. 899-912). The method is applicable to steady-state solutions for ground-water flow. Tests are presented for a homogeneous two-dimensional system that has matching grids (parent cells border an integer number of child cells) or nonmatching grids. The coupled grids are simulated by using the finite-difference and finite-element models MODFLOW and FEHM, respectively. The simulations require no alteration of the MODFLOW or FEHM models and are executed using a batch file on Windows operating systems. Results indicate that when the grids are matched spatially so that nodes and child-cell boundaries are aligned, the new coupling technique has error nearly equal to that when coupling two MODFLOW models. When the grids are nonmatching, model accuracy is slightly increased compared to that for matching-grid cases. Overall, results indicate that the ghost-node technique is a viable means to couple distinct models because the overall head and flow errors relative to the analytical solution are less than if only the regional coarse-grid model was used to simulate flow in the child model's domain.

Dynamic 2D self-phase-map Nyquist ghost correction for simultaneous multi-slice echo planar imaging.

PubMed

Yarach, Uten; Tung, Yi-Hang; Setsompop, Kawin; In, Myung-Ho; Chatnuntawech, Itthi; Yakupov, Renat; Godenschweger, Frank; Speck, Oliver

2018-02-09

To develop a reconstruction pipeline that intrinsically accounts for both simultaneous multislice echo planar imaging (SMS-EPI) reconstruction and dynamic slice-specific Nyquist ghosting correction in time-series data. After 1D slice-group average phase correction, the separate polarity (i.e., even and odd echoes) SMS-EPI data were unaliased by slice GeneRalized Autocalibrating Partial Parallel Acquisition. Both the slice-unaliased even and odd echoes were jointly reconstructed using a model-based framework, extended for SMS-EPI reconstruction that estimates a 2D self-phase map, corrects dynamic slice-specific phase errors, and combines data from all coils and echoes to obtain the final images. The percentage ghost-to-signal ratios (%GSRs) and its temporal variations for MB3R y 2 with a field of view/4 shift in a human brain obtained by the proposed dynamic 2D and standard 1D phase corrections were 1.37 ± 0.11 and 2.66 ± 0.16, respectively. Even with a large regularization parameter λ applied in the proposed reconstruction, the smoothing effect in fMRI activation maps was comparable to a very small Gaussian kernel size 1 × 1 × 1 mm 3 . The proposed reconstruction pipeline reduced slice-specific phase errors in SMS-EPI, resulting in reduction of GSR. It is applicable for functional MRI studies because the smoothing effect caused by the regularization parameter selection can be minimal in a blood-oxygen-level-dependent activation map. © 2018 International Society for Magnetic Resonance in Medicine.

Scalable Failure Masking for Stencil Computations using Ghost Region Expansion and Cell to Rank Remapping

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

Gamell, Marc; Teranishi, Keita; Kolla, Hemanth

In order to achieve exascale systems, application resilience needs to be addressed. Some programming models, such as task-DAG (directed acyclic graphs) architectures, currently embed resilience features whereas traditional SPMD (single program, multiple data) and message-passing models do not. Since a large part of the community's code base follows the latter models, it is still required to take advantage of application characteristics to minimize the overheads of fault tolerance. To that end, this paper explores how recovering from hard process/node failures in a local manner is a natural approach for certain applications to obtain resilience at lower costs in faulty environments.more » In particular, this paper targets enabling online, semitransparent local recovery for stencil computations on current leadership-class systems as well as presents programming support and scalable runtime mechanisms. Also described and demonstrated in this paper is the effect of failure masking, which allows the effective reduction of impact on total time to solution due to multiple failures. Furthermore, we discuss, implement, and evaluate ghost region expansion and cell-to-rank remapping to increase the probability of failure masking. To conclude, this paper shows the integration of all aforementioned mechanisms with the S3D combustion simulation through an experimental demonstration (using the Titan system) of the ability to tolerate high failure rates (i.e., node failures every five seconds) with low overhead while sustaining performance at large scales. In addition, this demonstration also displays the failure masking probability increase resulting from the combination of both ghost region expansion and cell-to-rank remapping.« less

Powering a leadless pacemaker using a PiezoMEMS energy harvester

NASA Astrophysics Data System (ADS)

Jackson, Nathan; Olszewski, Oskar; O'Murchu, Cian; Mathewson, Alan

2017-06-01

MEMS based vibrational energy harvesting devices have been a highly researched topic over the past decade. The application targeted in this paper focuses on a leadless pacemaker that will be implanted in the right ventricle of the heart. A leadless pacemaker requires the same functionality as a normal pacemaker, but with significantly reduced volume. The reduced volume limits the space for a battery; therefore an energy harvesting device is required. This paper compares varying the dimensions of a linear MEMS based piezoelectric energy harvester that can harvest energy from the mechanical vibrations of the heart due to shock induced vibration. Typical MEMS linear energy harvesting devices operate at high frequency (<50 Hz) with low acceleration (< 1g). The force generated from the heart acts as a series of impulses as opposed to traditional sinusoidal vibration force with high acceleration (1-4 g). Therefore the design of a MEMS harvester that is based on shock-induced vibration is necessary. PiezoMEMS energy harvesting devices consisting of a silicon substrate and mass with aluminium nitride piezoelectric material were developed and characterized using acceleration forces that mimic the heartbeat. Peak powers of up to 25μW were obtained at 1 g acceleration with a powder density of approximately 1.5 mW cm-3.

Objective lens simultaneously optimized for pupil ghosting, wavefront delivery and pupil imaging

NASA Technical Reports Server (NTRS)

Olczak, Eugene G (Inventor)

2011-01-01

An objective lens includes multiple optical elements disposed between a first end and a second end, each optical element oriented along an optical axis. Each optical surface of the multiple optical elements provides an angle of incidence to a marginal ray that is above a minimum threshold angle. This threshold angle minimizes pupil ghosts that may enter an interferometer. The objective lens also optimizes wavefront delivery and pupil imaging onto an optical surface under test.

Embeddings of the "New Massive Gravity"

NASA Astrophysics Data System (ADS)

Dalmazi, D.; Mendonça, E. L.

2016-07-01

Here we apply different types of embeddings of the equations of motion of the linearized "New Massive Gravity" in order to generate alternative and even higher-order (in derivatives) massive gravity theories in D=2+1. In the first part of the work we use the Weyl symmetry as a guiding principle for the embeddings. First we show that a Noether gauge embedding of the Weyl symmetry leads to a sixth-order model in derivatives with either a massive or a massless ghost, according to the chosen overall sign of the theory. On the other hand, if the Weyl symmetry is implemented by means of a Stueckelberg field we obtain a new scalar-tensor model for massive gravitons. It is ghost-free and Weyl invariant at the linearized level around Minkowski space. The model can be nonlinearly completed into a scalar field coupled to the NMG theory. The elimination of the scalar field leads to a nonlocal modification of the NMG. In the second part of the work we prove to all orders in derivatives that there is no local, ghost-free embedding of the linearized NMG equations of motion around Minkowski space when written in terms of one symmetric tensor. Regarding that point, NMG differs from the Fierz-Pauli theory, since in the latter case we can replace the Einstein-Hilbert action by specific f(R,Box R) generalizations and still keep the theory ghost-free at the linearized level.

Possible treatment of the ghost states in the Lee-Wick standard model

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

Shalaby, Abouzeid M.; Physics Department, Faculty of Science, Qassim University

2009-07-15

In this work, we employ the techniques used to cure the indefinite norm problem in pseudo-Hermitian Hamiltonians to show that the ghost states in a higher derivative scalar field theory are not real ghosts. For the model under investigation, an imaginary auxiliary field is introduced to have an equivalent non-Hermitian two-field scalar theory. We were able to calculate exactly the positive definite metric operator {eta} for the quantum mechanical as well as the quantum field versions of the theory. While the equivalent Hamiltonian is non-Hermitian in a Hilbert space characterized by the Dirac sense inner product, it is, however, amore » Hermitian in a Hilbert space endowed with the inner product . The main feature of the latter Hilbert space is that the propagator has the correct sign (no Lee-Wick fields). Moreover, the calculated metric operator diagonalizes the Hamiltonian in the two fields (no mixing). We found that the Hermiticity of the calculated metric operator to lead to the constrain M>2m for the two Higgs masses, in agreement with other calculations in the literature. Besides, our mass formulas coincide with those obtained in other works (obtained by a very different regime but with the existence of ghost states), which means that our positive normed Hamiltonian form preserves the mass spectra.« less

Annual air pollution caused by the Hungry Ghost Festival.

PubMed

Khezri, B; Chan, Y Y; Tiong, L Y D; Webster, R D

2015-09-01

Burning of joss paper and incense is still a very common traditional custom in countries with a majority Chinese population. The Hungry Ghost Festival which is celebrated in the 7 month of the Chinese calendar is one of the events where joss paper and incense are burned as offerings. This study investigates the impact of the Ghost Month Festival (open burning event) on air quality by analysis of the chemical composition of particulate matter (PM) and rainwater samples collected during this event, compared with data collected throughout the year, as well as bottom ash samples from burning the original joss paper and incense. The results showed that the change in the chemical composition of the rainwater and PM2.5 (PM ≤ 2.5 μm) atmospheric samples could be correlated directly with burning events during this festival, with many elements increasing between 18% and 60% during August and September compared to the yearly mean concentrations. The order of percentage increase in elemental composition (in rain water and PM2.5) during the Hungry Ghost Festival is as follows: Zn > Ca > K > Mg > Fe > Al > Na ∼ Mn ∼ Ti ∼ V > Cu > As > Ni > Co > Cd > Cr > Pb. The chemical composition of the original source materials (joss paper and incense for combustion) and their associated bottom ash were analysed to explain the impact of burning on air quality.

Linear spin-2 fields in most general backgrounds

NASA Astrophysics Data System (ADS)

Bernard, Laura; Deffayet, Cédric; Schmidt-May, Angnis; von Strauss, Mikael

2016-04-01

We derive the full perturbative equations of motion for the most general background solutions in ghost-free bimetric theory in its metric formulation. Clever field redefinitions at the level of fluctuations enable us to circumvent the problem of varying a square-root matrix appearing in the theory. This greatly simplifies the expressions for the linear variation of the bimetric interaction terms. We show that these field redefinitions exist and are uniquely invertible if and only if the variation of the square-root matrix itself has a unique solution, which is a requirement for the linearized theory to be well defined. As an application of our results we examine the constraint structure of ghost-free bimetric theory at the level of linear equations of motion for the first time. We identify a scalar combination of equations which is responsible for the absence of the Boulware-Deser ghost mode in the theory. The bimetric scalar constraint is in general not manifestly covariant in its nature. However, in the massive gravity limit the constraint assumes a covariant form when one of the interaction parameters is set to zero. For that case our analysis provides an alternative and almost trivial proof of the absence of the Boulware-Deser ghost. Our findings generalize previous results in the metric formulation of massive gravity and also agree with studies of its vielbein version.

Ecological periodic tables for benthic macrofaunal usage of estuarine habitats: Insights from a case study in Tillamook Bay, Oregon, USA

NASA Astrophysics Data System (ADS)

Ferraro, Steven P.; Cole, Faith A.

2012-05-01

This study validates the ecological relevance of estuarine habitat types to the benthic macrofaunal community and, together with previous similar studies, suggests they can serve as elements in ecological periodic tables of benthic macrofaunal usage in the bioregion. We compared benthic macrofaunal Bray-Curtis similarity and the means of eight benthic macrofaunal community measures across seven habitat types in Tillamook Bay, Oregon, USA: intertidal eelgrass (Zostera marina), dwarf eelgrass (Zostera japonica), oyster (Crassostrea gigas) ground culture, burrowing mud shrimp (Upogebia pugettensis), burrowing ghost shrimp (Neotrypaea californiensis), sand and subtidal. Benthic macrofaunal Bray-Curtis similarity differed among all the habitats except ghost shrimp and sand. The habitat rank order on mean benthic macrofaunal species richness, abundance and biomass was dwarf eelgrass ≈ oyster ≥ mud shrimp ≈ eelgrass > sand ≈ ghost shrimp ≈ subtidal. The benthic macrofaunal habitat usage pattern in Tillamook Bay was, with a few exceptions, similar to that in two other US Pacific Northwest estuaries. The exceptions indicate variants of eelgrass and ghost shrimp habitat that differ in benthic macrofaunal usage perhaps due to differences in the coarseness of the sand fraction of the sediments in which they live. The similarities indicate periodic benthic macrofaunal usage patterns across the other habitat types extend over a wider geographic scale and range of environmental conditions than previously known.

The evaluation model of the enterprise energy efficiency based on DPSR.

PubMed

Wei, Jin-Yu; Zhao, Xiao-Yu; Sun, Xue-Shan

2017-05-08

The reasonable evaluation of the enterprise energy efficiency is an important work in order to reduce the energy consumption. In this paper, an effective energy efficiency evaluation index system is proposed based on DPSR (Driving forces-Pressure-State-Response) with the consideration of the actual situation of enterprises. This index system which covers multi-dimensional indexes of the enterprise energy efficiency can reveal the complete causal chain which includes the "driver forces" and "pressure" of the enterprise energy efficiency "state" caused by the internal and external environment, and the ultimate enterprise energy-saving "response" measures. Furthermore, the ANP (Analytic Network Process) and cloud model are used to calculate the weight of each index and evaluate the energy efficiency level. The analysis of BL Company verifies the feasibility of this index system and also provides an effective way to improve the energy efficiency at last.

Ghost forest creation and the conversion of uplands to wetlands

NASA Astrophysics Data System (ADS)

Kirwan, M. L.; Schieder, N. W.; Reay, W.

2017-12-01

Global sea level rise rates began accelerating sharply in the late 19th century, with an approximate tripling in sea level rise rates in many regions of the world. Some portions of the coastal landscape, such as marshes and barrier islands, survive relative sea level rise by natural eco-geomorphic processes that allow them to build elevation vertically and migrate landward. In contrast, adjacent uplands typically occupied by forests and agricultural fields have limited ability to resist the impacts of sea level rise. This portion of the coastal landscape consists of mostly salt intolerant plants, receives little mineral sediment deposition, and rarely builds elevation through the accumulation of soil organic matter. Thus, ghost forests- dead trees surrounded by marshland- are a prominent feature of many low-relief coastal landscapes, and represent a striking visual indicator of upland to wetland conversion. Here, we report preliminary results of several efforts designed to quantify rates and drivers of upland to wetland conversion in the mid-Atlantic region of the United States. Drone based canopy monitoring and ground-based seedling experiments suggest that ghost forests are created by episodic, storm-driven adult tree mortality paired with continuous seedling mortality. Preliminary comparisons between sediment cores and historical photographs from 5 sites in Maryland, Virginia, and North Carolina suggest that modern coastal forest retreat is 2-10 times faster than late-Holocene retreat rates, and that rates have accelerated in most decades since the 1930's. Finally, historical T-Sheet maps suggest that approximately 100,000 acres (400 km2) of uplands have converted to wetlands in the Chesapeake region, and that about 1/3 of all present-day marsh was created by upland drowning since the late 19th Century. Together, these observations indicate rapid coastal transgression, where low-relief, terrestrial portions of the coastal landscape are perhaps more sensitive to sea level rise than better studied, more seaward portions.

Ghosts in the self-accelerating brane universe

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

Koyama, Kazuya; Institute of Cosmology and Gravitation, Portsmouth University, Portsmouth, PO1 2EG

2005-12-15

We study the spectrum of gravitational perturbations about a vacuum de Sitter brane with the induced 4D Einstein-Hilbert term, in a 5D Minkowski spacetime (DGP model). We consider solutions that include a self-accelerating universe, where the accelerating expansion of the universe is realized without introducing a cosmological constant on the brane. The mass of the discrete mode for the spin-2 graviton is calculated for various Hr{sub c}, where H is the Hubble parameter and r{sub c} is the crossover scale determined by the ratio between the 5D Newton constant and the 4D Newton constant. We show that, if we introducemore » a positive cosmological constant on the brane (Hr{sub c}>1), the spin-2 graviton has mass in the range 01/2. In a self-accelerating universe Hr{sub c}=1, the spin-2 graviton has mass m{sup 2}=2H{sup 2}, which coincides with the mass of the brane fluctuation mode. Then there arises a mixing between the brane fluctuation mode and the spin-2 graviton. We argue that this mixing presumably gives a ghost in the self-accelerating universe by continuity across Hr{sub c}=1, although a careful calculation of the effective action is required to verify this rigorously.« less

Understanding the sources and effects of abandoned, lost, and discarded fishing gear on marine turtles in northern Australia.

PubMed

Wilcox, Chris; Heathcote, Grace; Goldberg, Jennifer; Gunn, Riki; Peel, David; Hardesty, Britta Denise

2015-02-01

Globally, 6.4 million tons of fishing gear are lost in the oceans annually. This gear (i.e., ghost nets), whether accidently lost, abandoned, or deliberately discarded, threatens marine wildlife as it drifts with prevailing currents and continues to entangle marine organisms indiscriminately. Northern Australia has some of the highest densities of ghost nets in the world, with up to 3 tons washing ashore per kilometer of shoreline annually. This region supports globally significant populations of internationally threatened marine fauna, including 6 of the 7 extant marine turtles. We examined the threat ghost nets pose to marine turtles and assessed whether nets associated with particular fisheries are linked with turtle entanglement by analyzing the capture rates of turtles and potential source fisheries from nearly 9000 nets found on Australia's northern coast. Nets with relatively larger mesh and smaller twine sizes (e.g., pelagic drift nets) had the highest probability of entanglement for marine turtles. Net size was important; larger nets appeared to attract turtles, which further increased their catch rates. Our results point to issues with trawl and drift-net fisheries, the former due to the large number of nets and fragments found and the latter due to the very high catch rates resulting from the net design. Catch rates for fine-mesh gill nets can reach as high as 4 turtles/100 m of net length. We estimated that the total number of turtles caught by the 8690 ghost nets we sampled was between 4866 and 14,600, assuming nets drift for 1 year. Ghost nets continue to accumulate on Australia's northern shore due to both legal and illegal fishing; over 13,000 nets have been removed since 2005. This is an important and ongoing transboundary threat to biodiversity in the region that requires attention from the countries surrounding the Arafura and Timor Seas. © 2014 Society for Conservation Biology.

Human threats to sandy beaches: A meta-analysis of ghost crabs illustrates global anthropogenic impacts.

NASA Astrophysics Data System (ADS)

Schlacher, Thomas A.; Lucrezi, Serena; Connolly, Rod M.; Peterson, Charles H.; Gilby, Ben L.; Maslo, Brooke; Olds, Andrew D.; Walker, Simon J.; Leon, Javier X.; Huijbers, Chantal M.; Weston, Michael A.; Turra, Alexander; Hyndes, Glenn A.; Holt, Rebecca A.; Schoeman, David S.

2016-02-01

Beach and coastal dune systems are increasingly subjected to a broad range of anthropogenic pressures that on many shorelines require significant conservation and mitigation interventions. But these interventions require reliable data on the severity and frequency of adverse ecological impacts. Such evidence is often obtained by measuring the response of 'indicator species'. Ghost crabs are the largest invertebrates inhabiting tropical and subtropical sandy shores and are frequently used to assess human impacts on ocean beaches. Here we present the first global meta-analysis of these impacts, and analyse the design properties and metrics of studies using ghost-crabs in their assessment. This was complemented by a gap analysis to identify thematic areas of anthropogenic pressures on sandy beach ecosystems that are under-represented in the published literature. Our meta-analysis demonstrates a broad geographic reach, encompassing studies on shores of the Pacific, Indian, and Atlantic Oceans, as well as the South China Sea. It also reveals what are, arguably, two major limitations: i) the near-universal use of proxies (i.e. burrow counts to estimate abundance) at the cost of directly measuring biological traits and bio-markers in the organism itself; and ii) descriptive or correlative study designs that rarely extend beyond a simple 'compare and contrast approach', and hence fail to identify the mechanistic cause(s) of observed contrasts. Evidence for a historically narrow range of assessed pressures (i.e., chiefly urbanisation, vehicles, beach nourishment, and recreation) is juxtaposed with rich opportunities for the broader integration of ghost crabs as a model taxon in studies of disturbance and impact assessments on ocean beaches. Tangible advances will most likely occur where ghost crabs provide foci for experiments that test specific hypotheses associated with effects of chemical, light and acoustic pollution, as well as the consequences of climate change (e.g. species range shifts).

Molecular cloning and expression of a chloride channel-associated protein pICln in human young red blood cells: association with actin.

PubMed

Schwartz, R S; Rybicki, A C; Nagel, R L

1997-10-15

We report the cloning and sequencing from human reticulocytes of cDNA coding for the Cl- channel-associated protein, pICln. Human reticulocyte pICln (HRpICln) cDNA encodes a protein (predicted molecular mass 26293Da) identical with human non-pigmented ciliary epithelial cell pICln. By using full-length HRpICln cDNA (approx. 1.2 kb) to probe human lymphocyte metaphase-chromosome spreads, the location of the human ICln gene was mapped to 11q13 by fluorescence in situ hybridization analysis. Polyclonal antibodies to recombinant HRpICln detected bands at approx. 43 kDa and approx. 37 kDa in both normal (AA) and sickle (SS) red blood cell (RBC) ghost membranes. In SS ghosts, and in ghosts from a patient with autoimmune haemolytic anaemia with 9.8% reticulocytes, the amount of HRpICln was increased compared with AA ghosts, suggesting that the expression or membrane assembly of HRpICln is cell age-dependent. Laser scanning confocal fluorescent microscopy immunolocalized HRpICln largely to the RBC membrane. The increased staining intensity of HRpICln in a reticulocyte-enriched AA RBC density-separated fraction is consistent with a dependence of HRpICln membrane content on cell age. HRpICln and beta-actin form stable complexes in vivo, demonstrated with the yeast two-hybrid system. Low-ionic-strength extraction of ghost membranes, which results in the extraction of the spectrin-actin cytoskeleton, also results in the extraction of HRpICln, consistent with the possibility for the association of these proteins in RBCs in vivo. The results presented here establish the presence of the Cl- channel-associated protein, pICln, in human RBCs, and raises the possibility that this protein has a role in RBC Cl- transport and volume regulation in young RBCs. Moreover the association of RBC pICln with actin offers a model in which to test interactions between RBC ion channels and the cytoskeleton.

Accuracy of buffered-force QM/MM simulations of silica

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

Peguiron, Anke; Moras, Gianpietro; Colombi Ciacchi, Lucio

2015-02-14

We report comparisons between energy-based quantum mechanics/molecular mechanics (QM/MM) and buffered force-based QM/MM simulations in silica. Local quantities—such as density of states, charges, forces, and geometries—calculated with both QM/MM approaches are compared to the results of full QM simulations. We find the length scale over which forces computed using a finite QM region converge to reference values obtained in full quantum-mechanical calculations is ∼10 Å rather than the ∼5 Å previously reported for covalent materials such as silicon. Electrostatic embedding of the QM region in the surrounding classical point charges gives only a minor contribution to the force convergence. Whilemore » the energy-based approach provides accurate results in geometry optimizations of point defects, we find that the removal of large force errors at the QM/MM boundary provided by the buffered force-based scheme is necessary for accurate constrained geometry optimizations where Si–O bonds are elongated and for finite-temperature molecular dynamics simulations of crack propagation. Moreover, the buffered approach allows for more flexibility, since special-purpose QM/MM coupling terms that link QM and MM atoms are not required and the region that is treated at the QM level can be adaptively redefined during the course of a dynamical simulation.« less

Time-Reversal Location of the 2004 M6.0 Parkfield Earthquake Using the Vertical Component of Seismic Data.

NASA Astrophysics Data System (ADS)

Larmat, C. S.; Johnson, P.; Huang, L.; Randall, G.; Patton, H.; Montagner, J.

2007-12-01

In this work we describe Time Reversal experiments applying seismic waves recorded from the 2004 M6.0 Parkfield Earthquake. The reverse seismic wavefield is created by time-reversing recorded seismograms and then injecting them from the seismograph locations into a whole entire Earth velocity model. The concept is identical to acoustic Time-Reversal Mirror laboratory experiments except the seismic data are numerically backpropagated through a velocity model (Fink, 1996; Ulrich et al, 2007). Data are backpropagated using the finite element code SPECFEM3D (Komatitsch et al, 2002), employing the velocity model s20rts (Ritsema et al, 2000). In this paper, we backpropagate only the vertical component of seismic data from about 100 broadband surface stations located worldwide (FDSN), using the period band of 23-120s. We use those only waveforms that are highly correlated with forward-propagated synthetics. The focusing quality depends upon the type of waves back- propagated; for the vertical displacement component the possible types include body waves, Rayleigh waves, or their combination. We show that Rayleigh waves, both real and artifact, dominate the reverse movie in all cases. They are created during rebroadcast of the time reverse signals, including body wave phases, because we use point-like-force sources for injection. The artifact waves, termed "ghosts" manifest as surface waves, do not correspond to real wave phases during the forward propagation. The surface ghost waves can significantly blur the focusing at the source. We find that the ghosts cannot be easily eliminated in the manner described by Tsogka&Papanicolaou (2002). It is necessary to understand how they are created in order to remove them during TRM studies, particularly when using only the body waves. For this moderate magnitude of earthquake we demonstrate the robustness of the TRM as an alternative location method despite the restriction to vertical component phases. One advantage of TRM location is that it does not rely on a prior picking of specific phases (Larmat et al, 2006). In future work will be conducted TRM backpropagation using the horizontal displacement components of seismic data as well as study the source complexity (double couples). Our ultimate goal is to determine whether or not Time Reversal offers information about the source that cannot be obtained from other methods, or that complements other methods.

New symmetries and ghost structure of covariant string theories

NASA Astrophysics Data System (ADS)

Neveu, A.; Nicolai, H.; West, P.

1986-02-01

It is shown that there exists an infinite set of new symmetries of the previously given covariant string formulations. These symmetries have themselves an infinite set of hidden local symmetries and so on. A new physically equivalent further extended string action is given in which the infinite set of symmetries is most easily displayed. A quantization involving gauge fixing and ghosts of the various covariant string actions is given. permanent address: Kings College, Mathematics Department, London WC2R 2LS, UK.

Various Forms of BRST Symmetry in Abelian 2-FORM Gauge Theory

NASA Astrophysics Data System (ADS)

Rai, Sumit Kumar; Mandal, Bhabani Prasad

We derive the various forms of BRST symmetry using Batalin-Fradkin-Vilkovisky approach in the case of Abelian 2-form gauge theory. We show that the so-called dual BRST symmetry is not an independent symmetry but the generalization of BRST symmetry obtained from the canonical transformation in the bosonic and ghost sector. We further obtain the new forms of both BRST and dual-BRST symmetry by making a general transformation in the Lagrange multipliers of the bosonic and ghost sector of the theory.

The conformal hyperplet

NASA Astrophysics Data System (ADS)

Faux, Michael

2017-05-01

We introduce a finite off-shell hypermultiplet with no off-shell central charge. This requires 192+192 degrees of freedom, all but 8+8 of which are auxiliary or gauge. In the absence of supergravity, the model has a saddle-point vacuum instability implying ghost-like propagators. These are cured by realizing the model superconformally, such that the erstwhile ghosts are realized as compensators. Gauge fixing these links the physical hypermultiplets to supergravity. This evokes the prospect of realizing 𝒩 = 4 super-Yang-Mills theory off-shell.

Ghost microscope imaging system from the perspective of coherent-mode representation

NASA Astrophysics Data System (ADS)

Shen, Qian; Bai, Yanfeng; Shi, Xiaohui; Nan, Suqin; Qu, Lijie; Li, Hengxing; Fu, Xiquan

2018-03-01

The coherent-mode representation theory of partially coherent fields is firstly used to analyze a two-arm ghost microscope imaging system. It is shown that imaging quality of the generated images depend crucially on the distribution of the decomposition coefficients of the object imaged when the light source is fixed. This theory is also suitable for demonstrating the effects from the distance the object is moved away from the original plane on imaging quality. Our results are verified theoretically and experimentally.

Nonperturbative finite-temperature Yang-Mills theory

NASA Astrophysics Data System (ADS)

Cyrol, Anton K.; Mitter, Mario; Pawlowski, Jan M.; Strodthoff, Nils

2018-03-01

We present nonperturbative correlation functions in Landau-gauge Yang-Mills theory at finite temperature. The results are obtained from the functional renormalisation group within a self-consistent approximation scheme. In particular, we compute the magnetic and electric components of the gluon propagator, and the three- and four-gluon vertices. We also show the ghost propagator and the ghost-gluon vertex at finite temperature. Our results for the propagators are confronted with lattice simulations and our Debye mass is compared to hard thermal loop perturbation theory.

Democracy – the real ‘ghost’ in the machine of global health policy

PubMed Central

Harmer, Andrew

2014-01-01

Politics is not the ghost in the machine of global health policy. Conceptually, it makes little sense to argue otherwise, while history is replete with examples of individuals and movements engaging politically in global health policy. Were one looking for ghosts, a more likely candidate would be democracy, which is currently under attack by a new global health technocracy. Civil society movements offer an opportunity to breathe life into a vital, but dying, political component of global health policy PMID:25197680

Secure Quantum Technologies

NASA Astrophysics Data System (ADS)

Malik, Mehul

Over the past three decades, quantum mechanics has allowed the development of technologies that provide unconditionally secure communication. In parallel, the quantum nature of the transverse electromagnetic field has spawned the field of quantum imaging that encompasses technologies such as quantum lithography, quantum ghost imaging, and high-dimensional quantum key distribution (QKD). The emergence of such quantum technologies also highlights the need for the development of accurate and efficient methods of measuring and characterizing the elusive quantum state itself. In this thesis, I present new technologies that use the quantum properties of light for security. The first of these is a technique that extends the principles behind QKD to the field of imaging and optical ranging. By applying the polarization-based BB84 protocol to individual photons in an active imaging system, we obtained images that were secure against any intercept-resend jamming attacks. The second technology presented in this thesis is based on an extension of quantum ghost imaging, a technique that uses position-momentum entangled photons to create an image of an object without directly gaining any spatial information from it. We used a holographic filtering technique to build a quantum ghost image identification system that uses a few pairs of photons to identify an object from a set of known objects. The third technology addressed in this thesis is a high-dimensional QKD system that uses orbital-angular-momentum (OAM) modes of light for encoding. Moving to a high-dimensional state space in QKD allows one to impress more information on each photon, as well as introduce higher levels of security. I discuss the development of two OAM-QKD protocols based on the BB84 and Ekert protocols of QKD. In addition, I present a study characterizing the effects of turbulence on a communication system using OAM modes for encoding. The fourth and final technology presented in this thesis is a relatively new technique called direct measurement that uses sequential weak and strong measurements to characterize a quantum state. I use this technique to characterize the quantum state of a photon with a dimensionality of d = 27, and visualize its rotation in the natural basis of OAM.

Folding Free Energy Landscape of the Decapeptide Chignolin

NASA Astrophysics Data System (ADS)

Dou, Xianghua; Wang, Jihua

Chignolin is an artificially designed ten-residue (GYDPETGTWG) folded peptide, which is the smallest protein and provides a good template for protein folding. In this work, we completed four explicit water molecular dynamics simulations of Chignolin folding using GROMOS and OPLS-AA force fields from extended initial states without any experiment informations. The four-folding free energy landscapes of the peptide has been drawn. The folded state of Chignolin has been successfully predicated based on the free energy landscapes. The four independent simulations gave similar results. (i) The four free energy landscapes have common characters. They are fairly smooth, barrierless, funnel-like and downhill without intermediate state, which consists with the experiment. (ii) The different extended initial structures converge at similar folded structures with the lowest free energy under GROMOS and OPLS-AA force fields. In the GROMOS force field, the backbone RMSD of the folded structures from the NMR native structure of Chignolin is only 0.114 nm, which is a stable structure in this force field. In the OPLS-AA force field, the similar results have been obtained. In addition, the smallest RMSD structure is in better agreement with the NMR native structure but unlikely stable in the force field.

2018 Annual Terrestrial Sampling Plan for Sandia National Laboratories/New Mexico on Kirtland Air Force Base.

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

Griffith, Stacy R.

The 2018 Annual Terrestrial Sampling Plan for Sandia National Laboratories/New Mexico on Kirtland Air Force Base has been prepared in accordance with the “Letter of Agreement Between Department of Energy, National Nuclear Security Administration, Sandia Field Office (DOE/NNSA/SFO) and 377th Air Base Wing (ABW), Kirtland Air Force Base (KAFB) for Terrestrial Sampling” (signed January 2017), Sandia National Laboratories, New Mexico (SNL/NM). The Letter of Agreement requires submittal of an annual terrestrial sampling plan.

2017 Annual Terrestrial Sampling Plan for Sandia National Laboratories/New Mexico on Kirtland Air Force Base

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

Griffith, Stacy R.

The 2017 Annual Terrestrial Sampling Plan for Sandia National Laboratories/New Mexico on Kirtland Air Force Base has been prepared in accordance with the “Letter of Agreement Between Department of Energy, National Nuclear Security Administration, Sandia Field Office (DOE/NNSA/SFO) and 377th Air Base Wing (ABW), Kirtland Air Force Base (KAFB) for Terrestrial Sampling” (signed January 2017), Sandia National Laboratories, New Mexico (SNL/NM). The Letter of Agreement requires submittal of an annual terrestrial sampling plan.

Fighting detection using interaction energy force

NASA Astrophysics Data System (ADS)

Wateosot, Chonthisa; Suvonvorn, Nikom

2017-02-01

Fighting detection is an important issue in security aimed to prevent criminal or undesirable events in public places. Many researches on computer vision techniques have studied to detect the specific event in crowded scenes. In this paper we focus on fighting detection using social-based Interaction Energy Force (IEF). The method uses low level features without object extraction and tracking. The interaction force is modeled using the magnitude and direction of optical flows. A fighting factor is developed under this model to detect fighting events using thresholding method. An energy map of interaction force is also presented to identify the corresponding events. The evaluation is performed using NUSHGA and BEHAVE datasets. The results show the efficiency with high accuracy regardless of various conditions.

77 FR 32642 - Determination Concerning a Petition To Add a Class of Employees to the Special Exposure Cohort

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-01

... employees from Hangar 481 at Kirtland Air Force Base to the Special Exposure Cohort (SEC) under the Energy..., Kirtland Air Force Base, from March 1, 1989 through February 29, 1996. FOR FURTHER INFORMATION CONTACT...

A convex optimization method for self-organization in dynamic (FSO/RF) wireless networks

NASA Astrophysics Data System (ADS)

Llorca, Jaime; Davis, Christopher C.; Milner, Stuart D.

2008-08-01

Next generation communication networks are becoming increasingly complex systems. Previously, we presented a novel physics-based approach to model dynamic wireless networks as physical systems which react to local forces exerted on network nodes. We showed that under clear atmospheric conditions the network communication energy can be modeled as the potential energy of an analogous spring system and presented a distributed mobility control algorithm where nodes react to local forces driving the network to energy minimizing configurations. This paper extends our previous work by including the effects of atmospheric attenuation and transmitted power constraints in the optimization problem. We show how our new formulation still results in a convex energy minimization problem. Accordingly, an updated force-driven mobility control algorithm is presented. Forces on mobile backbone nodes are computed as the negative gradient of the new energy function. Results show how in the presence of atmospheric obscuration stronger forces are exerted on network nodes that make them move closer to each other, avoiding loss of connectivity. We show results in terms of network coverage and backbone connectivity and compare the developed algorithms for different scenarios.

Visible, invisible and trapped ghosts as sources of wormholes and black universes

NASA Astrophysics Data System (ADS)

Bolokhov, S. V.; Bronnikov, K. A.; Korolyov, P. A.; Skvortsova, M. V.

2016-02-01

We construct explicit examples of globally regular static, spherically symmetric solutions in general relativity with scalar and electromagnetic fields, describing traversable wormholes with flat and AdS asymptotics and regular black holes, in particular, black universes. (A black universe is a regular black hole with an expanding, asymptotically isotropic space-time beyond the horizon.) Such objects exist in the presence of scalar fields with negative kinetic energy (“phantoms”, or “ghosts”), which are not observed under usual physical conditions. To account for that, we consider what we call “trapped ghosts” (scalars whose kinetic energy is only negative in a strong-field region of space-time) and “invisible ghosts”, i.e., phantom scalar fields sufficiently rapidly decaying in the weak-field region. The resulting configurations contain different numbers of Killing horizons, from zero to four.

The evolving energy budget of accretionary wedges

NASA Astrophysics Data System (ADS)

McBeck, Jessica; Cooke, Michele; Maillot, Bertrand; Souloumiac, Pauline

2017-04-01

The energy budget of evolving accretionary systems reveals how deformational processes partition energy as faults slip, topography uplifts, and layer-parallel shortening produces distributed off-fault deformation. The energy budget provides a quantitative framework for evaluating the energetic contribution or consumption of diverse deformation mechanisms. We investigate energy partitioning in evolving accretionary prisms by synthesizing data from physical sand accretion experiments and numerical accretion simulations. We incorporate incremental strain fields and cumulative force measurements from two suites of experiments to design numerical simulations that represent accretionary wedges with stronger and weaker detachment faults. One suite of the physical experiments includes a basal glass bead layer and the other does not. Two physical experiments within each suite implement different boundary conditions (stable base versus moving base configuration). Synthesizing observations from the differing base configurations reduces the influence of sidewall friction because the force vector produced by sidewall friction points in opposite directions depending on whether the base is fixed or moving. With the numerical simulations, we calculate the energy budget at two stages of accretion: at the maximum force preceding the development of the first thrust pair, and at the minimum force following the development of the pair. To identify the appropriate combination of material and fault properties to apply in the simulations, we systematically vary the Young's modulus and the fault static and dynamic friction coefficients in numerical accretion simulations, and identify the set of parameters that minimizes the misfit between the normal force measured on the physical backwall and the numerically simulated force. Following this derivation of the appropriate material and fault properties, we calculate the components of the work budget in the numerical simulations and in the simulated increments of the physical experiments. The work budget components of the physical experiments are determined from backwall force measurements and incremental velocity fields calculated via digital image correlation. Comparison of the energy budget preceding and following the development of the first thrust pair quantifies the tradeoff of work done in distributed deformation and work expended in frictional slip due to the development of the first backthrust and forethrust. In both the numerical and physical experiments, after the pair develops internal work decreases at the expense of frictional work, which increases. Despite the increase in frictional work, the total external work of the system decreases, revealing that accretion faulting leads to gains in efficiency. Comparison of the energy budget of the accretion experiments and simulations with the strong and weak detachments indicate that when the detachment is strong, the total energy consumed in frictional sliding and internal deformation is larger than when the detachment is relatively weak.

AMS implications of charge-changing during acceleration

NASA Astrophysics Data System (ADS)

Knies, D. L.; Grabowski, K. S.; Cetina, C.; Demoranville, L. T.; Dougherty, M. R.; Mignerey, A. C.; Taylor, C. L.

2007-08-01

The NRL Accelerator Mass Spectrometer facility was recently reconfigured to incorporate a modified Cameca IMS 6f Secondary Ion Mass Spectrometer as a high-performance ion source. The NRL accelerator facility supplants the mass spectrometer portion of the IMS 6f instrument. As part of the initial testing of the combined instrument, charge-state scans were performed under various conditions. These provided the basis for studying the effects of terminal gas pressure on the process of charge-changing during acceleration. A combined system of transmission-micro-channel plate and energy detector was found to remove ghost beams produced from Pd charge-changing events in the accelerator tube.