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Sample records for nonradial pulsations lecture

  1. Nonradial Pulsations in ɛ Persei

    Science.gov (United States)

    Saio, Hideyuki; Kambe, Eiji; Lee, Umin

    2000-11-01

    We consider the question of whether all the modes detected in the line profile variations of ɛ Persei are consistent with nonradial pulsations excited by the kappa mechanism at the opacity Z-bump. We have computed massive (12.5-14 Msolar) main-sequence models, adjusting the parameters such that the evolutionary tracks pass around the approximate position of ɛ Per on the H-R diagram. A linear nonadiabatic, nonradial pulsation analysis is applied to these models. The periods in the frame corotating with the stellar surface for the observed 2.3-4.5 hr modes are found to be consistent with the Z-bump kappa mechanism. We have found, however, that the longest-period mode (8.48 hr in the observer's frame) cannot be explained by the kappa mechanism. We have examined the effect of rotation on the stability of oscillations and found that the stabilizing effect is weak, so that only a few of the shortest-period modes are stabilized for the rotation speed of ɛ Per. No significant difference is found between prograde and retrograde modes in the stability. It is a puzzle why no retrograde mode has been detected in ɛ Per, which should equally be excited by the kappa mechanism. We also discuss the observed and theoretical line profile variations of ɛ Per in the Appendix.

  2. Nonradial Pulsations in Classical Cepheids of the Magellanic Clouds

    CERN Document Server

    Moskalik, P; Moskalik, Pawel; Mizerski, Zbigniew Kolaczkowski & Tomasz

    2003-01-01

    We have performed systematic frequency analysis of the LMC Cepheids observed by OGLE project. Several new types of pulsation behaviour are identified, including triple-mode and amplitude-modulated double-mode pulsations. In ~10% of the first overtone Cepheids we find low amplitude secondary periodicities corresponding to nonradial modes. This is the first evidence for excitation of nonradial oscillations in Classical Cepheid variables.

  3. Latitude distribution of nonradial pulsations in rapidly rotating B stars

    Science.gov (United States)

    Jankov, S.; Mathias, P.; Domiciano de Souza, A., Jr.; Uytterhoeven, K.; Aerts, C.

    2004-05-01

    We present a method for the analysis of latitude distribution associated with temperature and/or velocity perturbations of the stellar surface due to non-radial pulsation (NRP) modes in rapidly rotating B stars. The technique is applied together with Fourier Doppler Imaging (FDI) to high resolution and high signal-to-noise ratio spectroscopic observations of ɛ Per. The main advantage of this approach is that it decomposed complex multi-periodic line profile variations into single components, allowing the detailed analysis of each mode seperately. We study the 10.6-d-1 frequency that is particularly important for modal analysis of non-radial pulsations in the star.

  4. Non-radial Pulsations in the Open Cluster NGC 3766

    CERN Document Server

    Roettenbacher, Rachael M; McSwain, M Virginia

    2009-01-01

    Non-radial pulsations (NRPs) are a proposed mechanism for the formation of decretion disks around Be stars and are important tools to study the internal structure of stars. NGC 3766 has an unusually large fraction of transient Be stars, so it is an excellent location to study the formation mechanism of Be star disks. High resolution spectroscopy can reveal line profile variations from NRPs, allowing measurements of both the degree, l, and azimuthal order, m. However, spectroscopic studies require large amounts of time with large telescopes to achieve the necessary high S/N and time domain coverage. On the other hand, multi-color photometry can be performed more easily with small telescopes to measure l only. Here, we present representative light curves of Be stars and non-emitting B stars in NGC 3766 from the CTIO 0.9m telescope in an effort to study NRPs in this cluster.

  5. Indirect imaging of nonradial pulsations in a rapidly oscillating Ap star

    CERN Document Server

    Kochukhov, O P

    2004-01-01

    Many types of stars show periodic variations of radius and brightness, which are commonly referred to as `stellar pulsations'. Observed pulsational characteristics are determined by fundamental stellar parameters. Consequently, investigations of stellar pulsations provide a unique opportunity to verify and refine our understanding of the evolution and internal structure of stars. However, a key boundary condition for this analysis -- precise information about the geometry of pulsations in the outer stellar envelopes -- has been notoriously difficult to secure. Here we demonstrate that it is possible to solve this problem by constructing an `image' of the pulsation velocity field from time series observations of stellar spectra. This technique is applied to study the geometry of nonradial pulsations in a prototype magnetic oscillating (roAp) star HR 3831. Our velocity map directly demonstrates an alignment of pulsations with the axis of the global magnetic field and reveals a significant magnetically induced d...

  6. Discovery of non-radial pulsations in the spectroscopic binary Herbig Ae star RS Cha

    CERN Document Server

    Böhm, T; Catala, C; Alecian, E; Pollard, K; Wright, D

    2008-01-01

    In this article we present a first discovery of non radial pulsations in both components of the Herbig Ae spectroscopic binary star RS Cha. The binary was monitored in quasi-continuous observations during 14 observing nights (Jan 2006) at the 1m Mt John (New Zealand) telescope with the Hercules high-resolution echelle spectrograph. The cumulated exposure time on the star was 44 hrs, corresponding to 255 individual high-resolution echelle spectra with $R = 45000$. Least square deconvolved spectra (LSD) were obtained for each spectrum representing the effective photospheric absorption profile modified by pulsations. Difference spectra were calculated by subtracting rotationally broadened artificial profiles; these residual spectra were analysed and non-radial pulsations were detected. A subsequent analysis with two complementary methods, namely Fourier Parameter Fit (FPF) and Fourier 2D (F2D) has been performed and first constraints on the pulsation modes have been derived. In fact, both components of the spect...

  7. A New Code for Nonradial Stellar Pulsations and its Application to Low - Mass, Helium White Dwarfs

    CERN Document Server

    Corsico, A H

    2002-01-01

    We present a finite difference code intended for computing linear, adiabatic, nonradial pulsations of spherical stars. This code is based on a general Newton - Raphson technique in order to handle the relaxation of the eigenvalue (square of the eigenfrequency) of the modes and their corresponding eigenfunctions. This code has been tested computing the pulsation spectra of polytropic spheres finding a good agreement with previous work. Then, we have coupled this code to our evolutionary code and applied it to the computation of the pulsation spectrum of a low mass, pure - helium white dwarf of 0.3 M_{sun} for a wide range of effective temperatures. In making this calculation we have taken an evolutionary time step short enough such that eigenmodes corresponding to a given model are used as initial approximation to those of the next one. Specifically, we have computed periods, period spacing, eigenfunctions, weight functions, kinetic energies and variational periods for a wide range of modes. To our notice this...

  8. Non-radial pulsations in the γ Doradus star HD 195068

    Science.gov (United States)

    Jankov, S.; Mathias, P.; Chapellier, E.; Le Contel, J.-M.; Sareyan, J.-P.

    2006-07-01

    We present high resolution spectroscopic observations of the γ Doradus star HD 195068. About 230 spectra were collected over 2 years. Time series analysis performed on radial velocity data shows a main peak at 1.61 d-1 , a frequency not yet detected in photometry. The Hipparcos photometric 1.25 d-1 frequency is easily recovered as is 1.30 d-1 while the third photometric frequency, 0.97 d-1 , is only marginally present. The good quality of our data, which includes 196 spectra collected over seven consecutive nights, shows that both the 1.61 d-1 and intermediate 1.27 d-1 (mixture of 1.25 and 1.30 d-1 ) frequencies are present in the line profile variations. Using the Fourier-Doppler Imaging (FDI) method, the variability associated with 1.61 d-1 can be successfully modeled by a non-radial pulsation mode ℓ=5± 1, |m|=4± 1. For the intermediate frequency 1.27 d-1 we deduce ℓ=4± 1, |m|=3± 1. Evidence that the star is not pulsating in the radial mode (ℓ=0) rules out a previous classification as an RR Lyrae type star. We investigate the time variability of FDI power spectra concluding that the observed temporal variability of modes can be explained by a beating phenomenon between closely spaced frequencies of two non-radial modes. The distribution of the oscillation power within the line profile indicates that there is a significant tangential velocity component of oscillations characteristic of high radial order gravity modes which are predicted to be observed in γ Doradus type stars.

  9. Spectroscopic monitoring of the Herbig Ae star HD 104237. II. Non-radial pulsations, mode analysis and fundamental stellar parameters

    CERN Document Server

    Fumel, Aurelie

    2011-01-01

    Herbig Ae/Be stars are intermediate-mass pre-main sequence (PMS) stars showing signs of intense activity and strong stellar winds, whose origin is not yet understood in the frame of current theoretical models of stellar evolution for young stars. The evolutionary tracks of the earlier Herbig Ae stars cross a recently discovered PMS instability strip. Many of these stars exhibit pulsations of delta Scuti type. HD 104237 is a well-known pulsating Herbig Ae star. In this article, we reinvestigated an extensive high-resolution quasi-continuous spectroscopic data set in order to search for very faint indications of non-radial pulsations in the line profile. To do this, we worked on dynamical spectra of equivalent photospheric (LSD) profiles of HD 104237. A 2D Fourier analysis (F2D) was performed of the entire profile and the temporal variation of the central depth of the line was studied with the time-series analysis tools Period04 and SigSpec. We present a mode identification corresponding to the detected dominan...

  10. Non-radial Pulsations in RR Lyrae Stars from the OGLE Collection

    CERN Document Server

    Netzel, H

    2016-01-01

    RR Lyrae stars are classical pulsating stars. They pulsate mostly in the radial fundamental mode (RRab stars), in the radial first overtone mode (RRc stars), or in both modes simultaneously (RRd stars). Collection of variable stars from the Optical Gravitational Lensing Experiment (OGLE) contains more than 38 000 RR Lyrae stars from the Galactic bulge. We analysed these data for RRc and RRd stars. We have found new members of radial-non-radial double-mode RR Lyrae stars, with characteristic period ratio of the two modes around 0.61. We increased the number of known RR Lyrae stars of this type by a factor of 8. We have also discovered another group of double-mode RR Lyrae stars. They pulsate in the first overtone and in another, unidentified mode, which has period longer than period of the undetected fundamental mode. The period ratios tightly cluster around 0.686. These proceedings are focused on this puzzling group. In particular, we report eight new members of the group.

  11. Rapid Rotation and Nonradial Pulsations $\\kappa$-Mechanism Excitation of G-Modes in B Stars

    CERN Document Server

    Ushomirsky, G; Ushomirsky, Greg; Bildsten, Lars

    1998-01-01

    Several classes of stars (most notably O and B main-sequence stars, as well as accreting white dwarfs and neutron stars) rotate quite rapidly, at spin frequencies greater than the typical g-mode frequencies. We discuss how rapid rotation modifies the $\\kappa$-mechanism excitation and observability of g-mode oscillations. We find that, by affecting the timescale match between the mode period and the thermal time at the driving zone, rapid rotation stabilizes some of the g-modes that are excited in a non-rotating star, and, conversely, excites g-modes that are damped in absence of rotation. The fluid velocities and temperature perturbations are strongly concentrated near the equator for most g-modes in rapidly rotating stars, which means that a favorable viewing angle may be required to observe the pulsations. Moreover, the stability of modes of the same $l$ but different $m$ is affected differently by rotation. We illustrate this by considering g-modes in Slowly Pulsating B-type stars as a function of the rota...

  12. Non-radial pulsation in first overtone Cepheids of the Small Magellanic Cloud

    CERN Document Server

    Smolec, R

    2016-01-01

    We analyse photometry for 138 first overtone Cepheids from the Small Magellanic Cloud, in which Optical Gravitational Lensing Experiment (OGLE) team discovered additional variability with period shorter than first overtone period, and period ratios in the (0.60, 0.65) range. In the Petersen diagram these stars form three well separated sequences. The additional variability cannot correspond to other radial mode. This form of pulsation is still puzzling. We find that amplitude of the additional variability is small, typically 2-4 per cent of the first overtone amplitude, which corresponds to 2-5 mmag. In some stars we find simultaneously two close periodicities corresponding to two sequences in the Petersen diagram. The most important finding is the detection of power excess at half the frequency of the additional variability (at subharmonic) in 35 per cent of the analysed stars. Interestingly, power excess at subharmonic frequency is detected mostly for stars of the middle sequence in the Petersen diagram (74...

  13. Non-radial pulsations in the Be/X binaries 4U0115+63 and SAXJ2103.5+4545

    CERN Document Server

    Gutiérrez-Soto, J; Fabregat, J; Fox-Machado, L

    2010-01-01

    The discovery of non-radial pulsations (NRP) in the Be/X binaries of the Magellanic Clouds (MC, eg. Fabrycky 2005, Coe et al. 2005, Schmidtke & Cowley 2005) provided a new approach to understand these complex systems, and, at the same time, favoured the synergy between two different fields: stellar pulsations and X-ray binaries. This breakthrough was possible thanks to the MACHO and OGLE surveys. However, in our Galaxy, only two Be/X have been reported to show NRP: GROJ2058+42 (Kiziloglu et al. 2007) and LSI+61 235 (Sarty et al. 2009). Our objective is to study the short-term variability of Galactic Be/X binaries, compare them to the Be/X of the MC and to the isolated Galactic Be observed with CoRoT and Kepler. We present preliminary results of two Be/X stars, namely 4U0115+63 and SAXJ2103.5+4545 showing multiperiodicity and periodicity respectively, most probably produced by non-radial pulsations.

  14. Non-radial pulsation, rotation and outburst in the Be star omega Orionis from the MuSiCoS 1998 campaign

    Science.gov (United States)

    Neiner, C.; Hubert, A.-M.; Floquet, M.; Jankov, S.; Henrichs, H. F.; Foing, B.; Oliveira, J.; Orlando, S.; Abbott, J.; Baldry, I. K.; Bedding, T. R.; Cami, J.; Cao, H.; Catala, C.; Cheng, K. P.; Domiciano de Souza, A., Jr.; Janot-Pacheco, E.; Hao, J. X.; Kaper, L.; Kaufer, A.; Leister, N. V.; Neff, J. E.; O'Toole, S. J.; Schäfer, D.; Smartt, S. J.; Stahl, O.; Telting, J.; Tubbesing, S.; Zorec, J.

    2002-06-01

    omega Ori (HD 37490, HR 1934) is a Be star known to have presented variations. In order to investigate the nature and origin of its short-term and mid-term variability, a study is performed of several spectral lines (Hα , Hdelta , ion {He}i 4471, 4713, 4921, 5876, 6678, ion {C}{ii} 4267, 6578, 6583, ion {Mg}{ii} 4481, ion {Si}{iii} 4553 and ion {Si}{ii} 6347), based on 249 high signal-to-noise high-resolution spectra taken with 8 telescopes over 22 consecutive nights during the MuSiCoS (Multi SIte COntinuous Spectroscopy) campaign in November-December 1998. The stellar parameters are revisited and the projected rotational velocity (vsin i = 179 km s-1) is redetermined using several methods. With the MuSiCoS 98 dataset, a time series analysis of line-profile variations (LPVs) is performed using the Restricted Local Cleanest (RLC) algorithm and a least squares method. The behaviour of the velocity of the centroid of the lines, the equivalent widths and the apparent vsini for several lines, as well as Violet and Red components of photospheric lines affected by emission (red ion {He}i lines, ion {Si}{ii} 6347, ion {C}{ii} 6578, 6583) are analyzed. The non-radial pulsation (NRP) model is examined using phase diagrams and the Fourier-Doppler Imaging (FDI) method. The LPVs are consistent with a NRP mode with l = 2 or 3, |m| = 2 with frequency 1.03 c d-1. It is shown that an emission line outburst occurred in the middle of the campaign. Two scenarios are proposed to explain the behaviour of a dense cloud, temporarily orbiting around the star with a frequency 0.46 c d-1, in relation to the outburst. Based on observations taken during the MuSiCoS 98 campaign at OHP (France), La Silla (ESO, Chile, ID 62.H-0270), Mount Stromlo (Australia), Xinglong Station (China), Kitt Peak (USA), MCT/LNA (Brazil) and INT (Isaac Newton Group, La Palma Island).

  15. The complex case of V445 Lyr observed with Kepler: Two Blazhko modulations, a non-radial mode, possible triple mode RR Lyrae pulsation, and more

    CERN Document Server

    Guggenberger, E; Nemec, J M; Smolec, R; Benkő, J M; Ngeow, C -C; Cohen, J G; Sesar, B; Szabó, R; Catelan, M; Moskalik, P; Kinemuchi, K; Seader, S E; Smith, J C; Tenenbaum, P; Kjeldsen, H

    2012-01-01

    Rapid and strong changes in the Blazhko modulation of RR Lyrae stars, as they have recently been detected in high precision satellite data, have become a crucial topic in finding an explanation of the long-standing mystery of the Blazhko effect. We present here an analysis of the most extreme case detected so far, the RRab star V445 Lyr (KIC 6186029) which was observed with the Kepler space mission. V445 Lyr shows very strong cycle-to-cycle changes in its Blazhko modulation, which are caused both by a secondary long-term modulation period as well as irregular variations. In addition to the complex Blazhko modulation, V445 Lyr also shows a rich spectrum of additional peaks in the frequency range between the fundamental pulsation and the first harmonic. Among those peaks, the second radial overtone could be identified, which, combined with a metallicity estimate of [Fe/H]=-2.0 dex from spectroscopy, allowed to constrain the mass (0.55-0.65 M_sun) and luminosity (40-50 L_sun) of V445 Lyr through theoretical Pete...

  16. First Kepler results on compact pulsators - II. KIC 010139564, a new pulsating subdwarf B (V361 Hya) star with an additional low-frequency mode

    DEFF Research Database (Denmark)

    Kawaler, Stephen; Reed, M.D.; Quint, A.C.;

    2010-01-01

    We present the discovery of non-radial pulsations in a hot subdwarf B star based on 30.5 d of nearly continuous time series photometry using the Kepler spacecraft. KIC 010139564 is found to be a short-period pulsator of the V361 Hya (EC 14026) class with more than 10 independent pulsation modes...

  17. Pulsations in close binaries: challenges and opportunities

    Directory of Open Access Journals (Sweden)

    Maceroni C.

    2015-01-01

    Full Text Available CoRoT and Kepler provided a precious by-product: a number of eclipsing binaries containing variable stars and, among these, non-radial pulsators. This providential occurrence allows combining independent information from two different phenomena whose synergy yields scientific results well beyond those from the single sources. In particular, the analysis of pulsations in eclipsing binary components throws light on the internal structure of the pulsating star, on the system evolution, and on the role of tidal forces in exciting the oscillations. The case study of the Kepler target KIC 3858884 is illustrative of the difficulties of analysis and of the achievements in this rapidly developing field.

  18. Pulsating stars

    CERN Document Server

    Catelan, M?rcio

    2014-01-01

    The most recent and comprehensive book on pulsating stars which ties the observations to our present understanding of stellar pulsation and evolution theory.  Written by experienced researchers and authors in the field, this book includes the latest observational results and is valuable reading for astronomers, graduate students, nuclear physicists and high energy physicists.

  19. Long Period Variables: questioning the pulsation paradigm

    CERN Document Server

    Berlioz-Arthaud, Paul

    2016-01-01

    Long period variables, among them Miras, are thought to be pulsating. Under this approach the whole star inflates and deflates along a period that can vary from 100 to 900 days; that pulsation is assumed to produce shock waves on the outer layers of the star that propagate into the atmosphere and could account for the increase in luminosity and the presence of emission lines in the spectra of these stars. However, this paradigm can seriously be questioned from a theoretical point of view. First, in order to maintain a radial pulsation, the spherical symmetry of the star must be preserved: how can it be reconciled with the large convective cells present in these stars? or when close companions are detected? Secondly, how different radial and non-radial pulsation modes of a sphere could be all damped except one radial mode? These problems have no solution and significantly weigh on the pulsation paradigm. Acknowledging this inconsistency, we show that a close companion around these stars could account for the s...

  20. Nonradial modes in RR Lyrae stars from the OGLE Collection of Variable Stars

    CERN Document Server

    Netzel, Henryka; Moskalik, Pawel

    2016-01-01

    The Optical Gravitational Lensing Experiment (OGLE) is a great source of top-quality photometry of classical pulsators. Collection of variable stars from the fourth part of the project contains more than 38 000 RR Lyrae stars. These stars pulsate mostly in the radial fundamental mode (RRab), in radial first overtone (RRc) or in both modes simultaneously (RRd). Analysis of the OGLE data allowed to detect additional non-radial modes in RRc and in RRd stars. We have found more than 260 double-mode stars with characteristic period ratio of the additional (shorter) period to first overtone period around 0.61, increasing the number of known stars of this type by factor of 10. Stars from the OGLE sample form three nearly parallel sequences in the Petersen diagram. Some stars show more than one non-radial mode simultaneously. These modes belong to different sequences.

  1. Hybrid Pulsators -- Pulsating Stars with Multiple Identities

    CERN Document Server

    Zhou, A -Y

    2015-01-01

    We have carried out a statistic survey on the pulsating variable stars with multiple identities. These stars were identified to exhibit two types of pulsation or multiple light variability types in the literature, and are usually called hybrid pulsators. We extracted the hybrid information based on the Simbad database. Actually, all the variables with multiple identities are retrieved. The survey covers various pulsating stars across the Hertzsprung-Russell diagram. We aim at giving a clue in selecting interesting targets for further observation. Hybrid pulsators are excellent targets for asteroseismology. An important implication of such stars is their potential in advancing the theories of both stellar evolution and pulsation. By presenting the statistics, we address the open questions and prospects regarding current status of hybrid pulsation studies.

  2. Return of Pulsations in SDSS 0745+4538

    Science.gov (United States)

    Mukadam, Anjum S.; Townsley, D. M.; Szkody, P.; Gänsicke, B. T.; Winget, D. E.; Hermes, J. J.; Howell, Steve B.; Teske, J.; Patterson, Joseph; Kemp, Jonathan; Armstrong, Eve

    2010-11-01

    Nonradial pulsations had ceased in the accreting white dwarf SDSS J074531.92+453829.6 subsequent to its October 2006 outburst. We recently acquired optical high-speed time-series photometry on this cataclysmic variable more than three years after its outburst to find that pulsations have now returned to the primary white dwarf. Moreover, the observed pulsation periods agree with pre-outburst periods within the uncertainties of 1-2 s. This discovery is both remarkable and significant because it indicates that the outburst did not affect the interior stellar structure, which dictates the observed pulsation frequencies. Using this discovery in addition to an HST ultra-violet temperature measurement obtained one year after outburst, we have also been able to constrain the matter accreted during the 2006 outburst.

  3. Coupling of radial and nonradial oscillations of relativistic stars: Gauge-invariant formalism

    Science.gov (United States)

    Passamonti, Andrea; Bruni, Marco; Gualtieri, Leonardo; Sopuerta, Carlos F.

    2005-01-01

    Linear perturbation theory is appropriate to describe small oscillations of stars, while a mild nonlinearity is still tractable perturbatively but requires one to consider mode coupling, i.e., to take into account second order effects. It is natural to start to look at this problem by considering the coupling between linear radial and nonradial modes. A radial pulsation may be thought of as an important component of an overall mildly nonlinear oscillation, e.g., of a protoneutron star. Radial pulsations of spherical compact objects do not per se emit gravitational waves but, if the coupling between the existing first order radial and nonradial modes is efficient in driving and possibly amplifying the nonradial oscillations, one may expect the appearance of nonlinear harmonics, and gravitational radiation could then be produced to a significant level. More in general, mode coupling typically leads to an interesting phenomenology, thus it is worth investigating in the context of star perturbations. In this paper we develop the relativistic formalism to study the coupling of radial and nonradial first order perturbations of a compact spherical star. From a mathematical point of view, it is convenient to treat the two sets of perturbations as separately parametrized, using a 2-parameter perturbative expansion of the metric, the energy-momentum tensor and Einstein equations in which λ is associated with the radial modes, ɛ with the nonradial perturbations, and the λɛ terms describe the coupling. This approach provides a well-defined framework to consider the gauge dependence of perturbations, allowing us to use ɛ order gauge-invariant nonradial variables on the static background and to define new second order λɛ gauge-invariant variables representing the result of the nonlinear coupling. We present the evolution and constraint equations for our variables outlining the setup for numerical computations, and briefly discuss the surface boundary conditions in terms

  4. High-Precision Spectroscopy of Pulsating Stars

    CERN Document Server

    Aerts, C; Desmet, M; Carrier, F; Zima, W; Briquet, M; De Ridder, J

    2007-01-01

    We review methodologies currently available to interprete time series of high-resolution high-S/N spectroscopic data of pulsating stars in terms of the kind of (non-radial) modes that are excited. We illustrate the drastic improvement of the detection treshold of line-profile variability thanks to the advancement of the instrumentation over the past two decades. This has led to the opportunity to interprete line-profile variations with amplitudes of order m/s, which is a factor 1000 lower than the earliest line-profile time series studies allowed for.

  5. Recent advances in the theoretical modeling of pulsating low-mass He-core white dwarfs

    CERN Document Server

    Córsico, A H; Calcaferro, L M; Serenelli, A M; Kepler, S O; Jeffery, C S

    2016-01-01

    Many extremely low-mass (ELM) white-dwarf (WD) stars are currently being found in the field of the Milky Way. Some of these stars exhibit long-period nonradial $g$-mode pulsations, and constitute the class of ELMV pulsating WDs. In addition, several low-mass pre-WDs, which could be precursors of ELM WDs, have been observed to show short-period photometric variations likely due to nonradial $p$ modes and radial modes. They could constitute a new class of pulsating low-mass pre-WD stars, the pre-ELMV stars. Here, we present the recent results of a thorough theoretical study of the nonadiabatic pulsation properties of low-mass He-core WDs and pre-WDs on the basis of fully evolutionary models representative of these stars.

  6. KIC 3858884: a hybrid {\\delta} Sct pulsator in a highly eccentric eclipsing binary

    CERN Document Server

    Maceroni, C; da Silva, R; Montalbán, J; Lee, C -U; Ak, H; Deshpande, R; Yakut, K; Debosscher, J; Guo, Z; Kim, S -L; Lee, J W; Southworth, J

    2014-01-01

    The analysis of eclipsing binaries containing non-radial pulsators allows: i) to combine two different and independent sources of information on the internal structure and evolutionary status of the components, and ii) to study the effects of tidal forces on pulsations. KIC 3858884 is a bright Kepler target whose light curve shows deep eclipses, complex pulsation patterns with pulsation frequencies typical of {\\delta} Sct, and a highly eccentric orbit. We present the result of the analysis of Kepler photometry and of high resolution phaseresolved spectroscopy. Spectroscopy yielded both the radial velocity curves and, after spectral disentangling, the primary component effective temperature and metallicity, and line-of-sight projected rotational velocities. The Kepler light curve was analyzed with an iterative procedure devised to disentangle eclipses from pulsations which takes into account the visibility of the pulsating star during eclipses. The search for the best set of binary parameters was performed com...

  7. GW Librae: A unique laboratory for pulsations in an accreting white dwarf

    CERN Document Server

    Toloza, O; Hermes, J J; Townsley, D M; Schreiber, M R; Szkody, P; Pala, A; Beuermann, K; Bildsten, L; Breedt, E; Cook, M; Godon, P; Henden, A A; Hubeny, I; Knigge, C; Long, K S; Marsh, T R; de Martino, D; Mukadam, A S; Myers, G; Nelson, P; Oksanen, A; Patterson, J; Sion, E M; Zorotovic, M

    2016-01-01

    Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of HST ultraviolet spectroscopy taken in 2002, 2010 and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in May~2013, we obtained new HST/COS ultraviolet observations that displayed unexpected behaviour: besides showing variability at ~275s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhi...

  8. The pulsations of the Sun and the stars

    CERN Document Server

    Rozelot, Jean-Pierre

    2011-01-01

    This volume of lecture notes brings together the knowledge on pulsations of the Sun and the stars, with a particular emphasis on recent observations and modelling, and on the influence of pulsations of other physical processes. The book begins with an extensive introduction to helioseismology. The solar cycle and gravity modes are discussed before the focus is widened from helioseismology to asteroseismology which is detailed in a series of specific chapters. Based on courses given at a graduate school, these tutorial lecture notes will be of interest and useful to a rather broad audience of scientists and students.

  9. A Photometric Study of the Pulsating Variable Star TYC 0075 01143 1

    Science.gov (United States)

    Khruslov, A. V.; Kusakin, A. V.

    2013-09-01

    We present the results of our new observations of TYC 0075 01143 1, a recently discovered double-mode delta Scuti variable. We improved the frequencies f0 and f1 and pulsation amplitudes, detected the interaction frequencies f1+f0, f1-f0, and a possible nonradial frequency fN.

  10. New DA white dwarf evolutionary models and their pulsational properties

    CERN Document Server

    Corsico, A H; Benvenuto, O G; Serenelli, A M

    2001-01-01

    In this letter we investigate the pulsational properties of ZZ Ceti stars on the basis of new white dwarf evolutionary models calculated in a self-consistent way with the predictions of time dependent element diffusion and nuclear burning. In addition, full account is taken of the evolutionary stages prior to the white dwarf formation. Emphasis is placed on the trapping properties of such models. By means of adiabatic, non-radial pulsation calculations, we find, as a result of time dependent diffusion, a much weaker mode trapping effect, particularly for the high-period regime of the pulsation g-spectrum. This result is valid at least for models with massive hydrogen-rich envelopes. Thus, mode trapping would not be an effective mechanism to explain the fact that all the high periods expected from standard models of stratified white dwarfs are not observed in the ZZ Ceti stars.

  11. GW Librae: a unique laboratory for pulsations in an accreting white dwarf

    Science.gov (United States)

    Toloza, O.; Gänsicke, B. T.; Hermes, J. J.; Townsley, D. M.; Schreiber, M. R.; Szkody, P.; Pala, A.; Beuermann, K.; Bildsten, L.; Breedt, E.; Cook, M.; Godon, P.; Henden, A. A.; Hubeny, I.; Knigge, C.; Long, K. S.; Marsh, T. R.; de Martino, D.; Mukadam, A. S.; Myers, G.; Nelson, P.; Oksanen, A.; Patterson, J.; Sion, E. M.; Zorotovic, M.

    2016-07-01

    Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of Hubble Space Telescope (HST) ultraviolet spectroscopy taken in 2002, 2010, and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in 2013 May, we obtained new HST/Cosmic Origin Spectrograph ultraviolet observations that displayed unexpected behaviour: besides showing variability at ≃275 s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhibits high-amplitude variability on an ≃4.4 h time-scale. We demonstrate that this variability is produced by an increase of the temperature of a region on white dwarf covering up to ≃30 per cent of the visible white dwarf surface. We argue against a short-lived accretion episode as the explanation of such heating, and discuss this event in the context of non-radial pulsations on a rapidly rotating star.

  12. Nonradial g-mode oscillations in X-ray bursting neutron stars

    Science.gov (United States)

    Mcdermott, P. N.; Taam, Ronald E.

    1987-01-01

    The oscillation spectrum of nonradial g-modes in X-ray bursting neutron stars has been studied. The pulsation periods are found to be sensitive to the envelope temperature and range from about 15 ms to about 50 ms for the l = 1 g(1) mode during the X-ray burst. From a quasi-adiabatic stability analysis it is likely that a spectrum of l-pole g-modes is unstable due to the epsilon-mechanism associated with rapid alpha captures. As the thermal structure of the envelope of the neutron star changes on time scales less than 0.2 s during the rise of the X-ray burst, the oscillations are expected to be quasi-coherent during this phase. The calculated period derivatives are large during the burst and are about 1 ms/s. The pulsations are short-lived and are most likely to be seen in the immediate vicinity of the burst peak. Finally, the possible relevance of nonradial g-mode pulsations to the recently discovered quasi-periodic oscillations observed in a number of X-ray sources is discussed.

  13. First Kepler results on compact pulsators - V. Slowly pulsating subdwarf B stars in short-period binaries

    DEFF Research Database (Denmark)

    Kawaler, Stephen D.; Reed, Michael D.; Østensen, Roy H.

    2010-01-01

    The survey phase of the Kepler Mission includes a number of hot subdwarf B (sdB) stars to search for non-radial pulsations. We present our analysis of two sdB stars that are found to be g-mode pulsators of the V1093 Her class. These two stars also display the distinct irradiation effect typical...... of sdB stars with a close M-dwarf companion with orbital periods of less than half a day. Because the orbital period is so short, the stars should be in synchronous rotation, and if so, the rotation period should imprint itself on the multiplet structure of the pulsations. However, we do not find clear...... evidence for such rotational splitting. Though the stars do show some frequency spacings that are consistent with synchronous rotation, they also display multiplets with splittings that are much smaller. Longer-duration time series photometry will be needed to determine if those small splittings...

  14. First Kepler results on compact pulsators - III. Subdwarf B stars with V1093 Her and hybrid (DW Lyn) type pulsations

    DEFF Research Database (Denmark)

    Reed, M.D.; Kawaler, Stephen D.; Østensen, Roy H.

    2010-01-01

    1093 Her (PG 1716) class or a hybrid star with both short and long periods. The apparently non-binary long-period and hybrid pulsators are described here. The V1093 Her periods range from 1 to 4.5 h and are associated with g-mode pulsations. Three stars also exhibit short periods indicative of p......We present the discovery of non-radial pulsations in five hot subdwarf B (sdB) stars based on 27 d of nearly continuous time series photometry using the Kepler spacecraft. We find that every sdB star cooler than ≈27 500 K that Kepler has observed (seven so far) is a long-period pulsator of the V......-modes with periods of 2-5 min and in addition, these stars exhibit periodicities between both classes from 15 to 45 min. We detect the coolest and longest-period V1093 Her-type pulsator to date, KIC010670103 (Teff≈ 20 900 K, Pmax≈ 4.5 h) as well as a suspected hybrid pulsator, KIC002697388, which is extremely cool...

  15. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    23, 24, 25, 26 and 27 April REGULAR LECTURE PROGRAMME From 11:00 hrs - Main Auditorium bldg. 500, on 23 April from 11:15 to 12:15 hrs Searches for Dark Matter F. Feinstein / CPPM, Marseille, F The fact that the mass of the visible stars could not account for the gravitational cohesion of the galaxy clusters was the first manifestation of non-radiating matter in the Universe. Since then, many observations imply that most of the matter is indeed dark. Its nature is still unknown and likely to have several contributions. Recent results indicate that most of it may not be composed of normal matter. These lectures will review the experimental methods, which have been developed to unravel this 70-year long mystery and confront their results with the current theoretical framework of cosmology.

  16. Is $\\lambda$ Cep a pulsating star?

    CERN Document Server

    Uuh-Sonda, J M; Rauw, G

    2014-01-01

    It has been proposed that the variability seen in absorption lines of the O6Ief star $\\lambda$ Cep is periodical and due to non-radial pulsations (NRP). We have obtained new spectra during six campaigns lasting between five and nine nights. In some datasets we find recurrent spectral variations which move redward in the absorption line profile, consistent with perturbations on the stellar surface of a rotating star. However the periods found are not stable between datasets, at odds with the NRP hypothesis. Moreover, even when no redward trend is found in a full dataset of an observing campaign, it can be present in a subset, suggesting that the phenomenon is short-lived, of the order of a few days, and possibly linked to transient magnetic loops.

  17. Radial velocity measurements of the pulsating zirconium star: LS IV -14 116

    CERN Document Server

    Jeffery, C Simon; Neelamkodan, Naslim; Kerzendorf, Wolfgang

    2014-01-01

    The helium-rich hot subdwarf LS IV -14 116 shows remarkably high surface abundances of zirconium, yttrium, strontium, and germanium, indicative of strong chemical stratification in the photosphere. It also shows photometric behaviour indicative of non-radial g-mode pulsations, despite having surface properties inconsistent with any known pulsational instability zone. We have conducted a search for radial velocity variability. This has demonstrated that at least one photometric period is observable in several absorption lines as a radial velocity variation with a semi-amplitude in excess of 5 km s$^{-1}$. A correlation between line strength and pulsation amplitude provides evidence that the photosphere pulsates differentially. The ratio of light to velocity amplitude is too small to permit the largest amplitude oscillation to be radial.

  18. Pulsations and outbursts in Be stars: Small differences - big impacts

    CERN Document Server

    Baade, D; Pigulski, A; Carciofi, A; Handler, G; Kuschnig, R; Martayan, Ch; Mehner, A; Moffat, A F J; Pablo, H; Popowicz, A; Rucinski, S M; Wade, G A; Weiss, W W; Zwintz, K

    2016-01-01

    New high-cadence observations with BRITE covering many months confirm that coupled pairs of nonradial pulsation modes are widespread among early-type Be stars. With the difference frequency between the parental variations they may form a roughly sinusoidal variability or the amplitude may cyclicly vary. A first - amplified - beat pattern is also found. In all three cases the amplitudes of difference frequencies can exceed the amplitude sum of the base frequencies, and modulations of the star-to-circumstellar-disk mass-transfer rate may be associated with these slow variations. This suggests more strongly than any earlier observations that significant dissipation of pulsational energy in the atmosphere may be a cause of mass ejections from Be stars. A unifying interpretative concept is presented.

  19. Non-radiative excitation fluorescence microscopy

    Science.gov (United States)

    Riachy, Lina; Vézy, Cyrille; Jaffiol, Rodolphe

    2016-03-01

    Non-radiative Excitation Fluorescence Microscopy (NEFM) constitutes a new way to observe biological samples beyond the diffraction limit. Non-radiative excitation of the samples is achieved by coating the substrate with donor species, such as quantum dots (QDs). Thus the dyes are not excited directly by the laser source, as in common fluorescence microscopy, but through a non-radiative energy transfer. To prevent dewetting of the donor film, we have recently implemented a silanization process to covalently bond the QDs on the substrate. An homogeneous monolayer of QDs was then deposited on only one side of the coverslips. Atomic force microscopy was then used to characterize the QD layer. We highlight the potential of our method through the study of Giant Unilamellar Vesicles (GUVs) labeled with DiD as acceptor, in interaction with surface functionalized with poly-L-lysine. In the presence of GUVs, we observed a quenching of QDs emission, together with an emission of DiD located in the membrane, which clearly indicated that non-radiative energy transfer from QDs to DiD occurs.

  20. Pulsational mode-typing in line profile variables. I - Four Beta Cephei stars

    Science.gov (United States)

    Campos, A. J.; Smith, M. A.

    1980-01-01

    The detailed variations of line profiles in the Beta Cephei-type variable stars Gamma Pegasi, Beta Cephei, Delta Ceti and Sigma Scorpii are modeled throughout their pulsation cycles in order to classify the dominant pulsation mode as radial or nonradial. High-dispersion Reticon observations of the variables were obtained for the Si III line at 4567 A, and line profiles broadened by radial or nonradial pulsations, rotation and radial-tangential macroturbulence were calculated based on a model atmosphere. It is found that only a radial pulsation mode can reproduce the radial velocity amplitude, changes in line asymmetry and uniform line width observed in all four stars. Results are in agreement with the color-to-light arguments of Stamford and Watson (1978), and suggest that radial pulsation plays the dominant role in the observed variations in most Beta Cephei stars. Evidence for shocks or moving shells is also found in visual line data for Sigma Scorpii and an ultraviolet line of Beta Cephei, together with evidence of smooth, secular period changes in Beta Cephei and Delta Ceti.

  1. Nonlinear pulsation masses

    Energy Technology Data Exchange (ETDEWEB)

    Davis, C.G.

    1990-01-01

    The advent of nonlinear pulsation theory really coincides with the development of the large computers after the second world war. Christy and Stobbie were the first to make use of finite difference techniques on computers to model the bumps'' observed in the classical Cepheid light and velocity curves, the so-called Hertzsprung'' sequence. Following this work a more sophisticated analysis of the light and velocity curves from the models was made by Simon and Davis using Fourier techniques. Recently a simpler amplitude equation formalism has been developed that helps explain this resonance mechanism. The determination of Population I Cepheid masses by nonlinear methods will be discussed. For the lower mass objects, such as RR Lyrae and BL Her. stars, we find general agreement using evolutionary masses and nonlinear pulsation theory. An apparent difficulty of nonlinear pulsation theory occurs in the understanding of double'' mode pulsation, which will also be discussed. Recent studies in nonlinear pulsation theory have dealt with the question of mode selection, period doubling and the trends towards chaotic behavior such as is observed in the transition from W Virginis to RV Tauri-like stars. 10 refs., 1 fig., 2 tabs.

  2. The Lecture

    Science.gov (United States)

    Chaudhury, S. Raj

    2011-01-01

    Academic lectures for the purpose of instruction maintain an important presence in most colleges and universities worldwide. This chapter examines the current state of the lecture and how learning sciences research can inform the most effective use of this method. The author presents evidence that the lecture can be an effective element of…

  3. Introducing CAFein, a New Computational Tool for Stellar Pulsations and Dynamic Tides

    OpenAIRE

    Valsecchi, Francesca; Farr, Will M.; Willems, Bart; Rasio, Frederic A.; Kalogera, Vassiliki

    2013-01-01

    Here we present CAFein, a new computational tool for investigating radiative dissipation of dynamic tides in close binaries and of non-adiabatic, non-radial stellar oscillations in isolated stars in the linear regime. For the latter, CAFein computes the non-adiabatic eigenfrequencies and eigenfunctions of detailed stellar models. The code is based on the so-called Riccati method, a numerical algorithm that has been successfully applied to a variety of stellar pulsators, and which doesn't suff...

  4. Excitation of Stellar Pulsations

    DEFF Research Database (Denmark)

    Houdek, G.

    2012-01-01

    In this review I present an overview of our current understanding of the physical mechanisms that are responsible for the excitation of pulsations in stars with surface convection zones. These are typically cooler stars such as the δ Scuti stars, and stars supporting solar-like oscillations....

  5. Asteroseismology of hybrid δ Scuti-γ Doradus pulsating stars

    Science.gov (United States)

    Sánchez Arias, J. P.; Córsico, A. H.; Althaus, L. G.

    2017-01-01

    Context. Hybrid δ Scuti-γ Doradus pulsating stars show acoustic (p) oscillation modes typical of δ Scuti variable stars, and gravity (g) pulsation modes characteristic of γ Doradus variable stars simultaneously excited. Observations from space missions such as MOST, CoRoT, and Kepler have revealed a large number of hybrid δ Scuti-γ Doradus pulsators, thus paving the way for an exciting new channel of asteroseismic studies. Aims: We perform detailed asteroseismological modelling of five hybrid δ Scuti-γ Doradus stars. Methods: A grid-based modeling approach was employed to sound the internal structure of the target stars using stellar models ranging from the zero-age main sequence to the terminal-age main sequence, varying parameters such as stellar mass, effective temperature, metallicity and core overshooting. Their adiabatic radial (ℓ = 0) and non-radial (ℓ = 1,2,3) p and g mode periods were computed. Two model-fitting procedures were used to search for asteroseismological models that best reproduce the observed pulsation spectra of each target star. Results: We derive the fundamental parameters and the evolutionary status of five hybrid δ Scuti-γ Doradus variable stars recently observed by the CoRoT and Kepler space missions: CoRoT 105733033, CoRoT 100866999, KIC 11145123, KIC 9244992, and HD 49434. The asteroseismological model for each star results from different criteria of model selection, in which we take full advantage of the richness of periods that characterises the pulsation spectra for this kind of star.

  6. Asteroseismology of hybrid $\\delta$ Scuti--$\\gamma$ Doradus pulsating stars

    CERN Document Server

    Arias, J P Sánchez; Althaus, L G

    2016-01-01

    Hybrid $\\delta$ Scuti-$\\gamma$ Doradus pulsating stars show acoustic ($p$) oscillation modes typical of $\\delta$ Scuti variable stars, and gravity ($g$) pulsation modes characteristic of $\\gamma$ Doradus variable stars simultaneously excited. Observations from space missions like MOST, CoRoT, and \\emph{Kepler} have revealed a large number of hybrid $\\delta$ Scuti-$\\gamma$ Doradus pulsators, thus paving the way for a exciting new channel for asteroseismic studies. We perform a detailed asteroseismological modeling of five hybrid $\\delta$ Scuti-$\\gamma$ Doradus stars. We employ a grid-based modeling approach to sound the internal structure of the target stars by employing a huge grid of stellar models from the zero-age main sequence to the terminal-age main sequence, varying parameters like stellar mass, effective temperature, metallicity and core overshooting. We compute their adiabatic radial ($\\ell= 0$) and non-radial ($\\ell= 1, 2, 3$) $p$ and $g$ mode periods. We employ two model-fitting procedures to searc...

  7. Pulsations powered by hydrogen shell burning in white dwarfs

    CERN Document Server

    Camisassa, María E; Althaus, Leandro G; Shibahashi, Hiromoto

    2016-01-01

    In the absence of a third dredge-up episode during the asymptotic giant branch phase, white dwarf models evolved from low-metallicity progenitors have a thick hydrogen envelope, which makes hydrogen shell burning be the most important energy source. We investigate the pulsational stability of white dwarf models with thick envelopes to see whether nonradial $g$-mode pulsations are triggered by hydrogen burning, with the aim of placing constraints on hydrogen shell burning in cool white dwarfs and on a third dredge-up during the asymptotic giant branch evolution of their progenitor stars. We construct white-dwarf sequences from low-metallicity progenitors by means of full evolutionary calculations, and analyze their pulsation stability for the models in the range of effective temperatures $T_{\\rm eff} \\sim 15\\,000\\,-\\, 8\\,000$ K. We demonstrate that, for white dwarf models with masses $M_{\\star} \\lesssim 0.71\\,\\rm M_{\\sun}$ and effective temperatures $8\\,500 \\lesssim T_{\\rm eff} \\lesssim 11\\,600$ K that evolved...

  8. Pulsation driving and convection

    Science.gov (United States)

    Antoci, Victoria

    2015-08-01

    Convection in stellar envelopes affects not only the stellar structure, but has a strong impact on different astrophysical processes, such as dynamo-generated magnetic fields, stellar activity and transport of angular momentum. Solar and stellar observations from ground and space have shown that the turbulent convective motion can also drive global oscillations in many type of stars, allowing to study stellar interiors at different evolutionary stages. In this talk I will concentrate on the influence of convection on the driving of stochastic and coherent pulsations across the Hertzsprung-Russell diagram and give an overview of recent studies.

  9. Coupling of Radial and Axial non-Radial Oscillations of Compact Stars: Gravitational Waves from first-order Differential Rotation

    CERN Document Server

    Passamonti, A; Gualtieri, L; Nagar, A; Sopuerta, C F

    2006-01-01

    We investigate the non-linear coupling between radial and non-radial oscillations of static spherically symmetric neutron stars as a possible mechanism for the generation of gravitational waves that may lead to observable signatures. In this paper we concentrate on the axial sector of the non-radial perturbations. By using a multi-parameter perturbative framework we introduce a complete description of the non-linear coupling between radial and axial non-radial oscillations; we study the gauge invariant character of the associated perturbative variables and develop a computational scheme to evolve the non-linear coupling perturbations in the time domain. We present results of simulations corresponding to different physical situations and discuss the dynamical behaviour of this non-linear coupling. Of particular interest is the occurrence of signal amplifications in the form of resonance phenomena when a frequency associated with the radial pulsations is close to a frequency associated with one of the axial w-m...

  10. Nonradial and radial period changes of the δ Scuti star 4 CVn. II. Systematic behavior over 40 years

    Science.gov (United States)

    Breger, M.; Montgomery, M. H.; Lenz, P.; Pamyatnykh, A. A.

    2017-03-01

    Aims: Radial and nonradial pulsators on and near the main sequence show period and amplitude changes that are too large to be the product of stellar evolution. The multiperiodic δ Sct stars are well suited to study this, as the period changes of different modes excited in the same star can be compared. This requires a very large amount of photometric data covering years and decades as well as mode identifications. Methods: We have examined over 800 nights of high-precision photometry of the multiperiodic pulsator 4 CVn obtained from 1966 through 2012. Because most of the data were obtained in adjacent observing seasons, it is possible to derive very accurate period values for a number of the excited pulsation modes and to study their systematic changes from 1974 to 2012. Results: Most pulsation modes show systematic significant period and amplitude changes on a timescale of decades. For the well-studied modes, around 1986 a general reversal of the directions of both the positive and negative period changes occurred. Furthermore, the period changes between the different modes are strongly correlated, although they differ in size and sign. For the modes with known values of the spherical degree and azimuthal order, we find a correlation between the direction of the period changes and the identified azimuthal order, m. The associated amplitude changes generally have similar timescales of years or decades, but show little systematic or correlated behavior from mode to mode. Conclusions: A natural explanation for the opposite behavior of the prograde and retrograde modes is that their period changes are driven by a changing rotation profile. The changes in the rotation profile could in turn be driven by processes, perhaps the pulsations themselves, that redistribute angular momentum within the star. In general, different modes have different rotation kernels, so this will produce period shifts of varying magnitude for different modes.

  11. Asteroseismology of Pulsating Stars

    Indian Academy of Sciences (India)

    Santosh Joshi; Yogesh C. Joshi

    2015-03-01

    The success of helioseismology is due to its capability of measuring -mode oscillations in the Sun. This allows us to extract information on the internal structure and rotation of the Sun from the surface to the core. Similarly, asteroseismology is the study of the internal structure of the stars as derived from stellar oscillations. In this review we highlight the progress in the observational asteroseismology, including some basic theoretical aspects. In particular, we discuss our contributions to asteroseismology through the study of chemically peculiar stars under the 'Nainital-Cape Survey' project being conducted at ARIES, Nainital, since 1999. This survey aims to detect new rapidly-pulsating Ap (roAp) stars in the northern hemisphere. We also discuss the contribution of ARIES towards the asteroseismic study of the compact pulsating variables. We comment on the future prospects of our project in the light of the new optical 3.6-m telescope to be installed at Devasthal (ARIES). Finally, we present a preliminary optical design of the high-speed imaging photometers for this telescope.

  12. Asteroseismology of the Beta Cephei star Nu Eridani: photometric observations and pulsational frequency analysis

    CERN Document Server

    Handler, G; Jerzykiewicz, M; Krisciunas, K; Tshenye, T; Rodríguez, E; Costa, V; Zhou, A Y; Medupe, R; Phorah, W M; Garrido, R; Amado, P J; Paparo, M; Zsuffa, D; Ramokgali, L; Crowe, R; Purves, N; Avila, R; Knight, R; Brassfield, E; Kilmartin, P M; Cottrell, P L

    2004-01-01

    We undertook a multisite photometric campaign for the Beta Cephei star Nu Eridani. More than 600 hours of differential photoelectric uvyV photometry were obtained with 11 telescopes during 148 clear nights. The frequency analysis of our measurements shows that the variability of Nu Eri can be decomposed into 23 sinusoidal components, eight of which correspond to independent pulsation frequencies between 5 - 8 c/d. Some of these are arranged in multiplets, which suggests rotational m-mode splitting of nonradial pulsation modes as the cause. If so, the rotation period of the star must be between 30 - 60 d. One of the signals in the light curves of Nu Eri has a very low frequency of 0.432 c/d. It can be a high-order combination frequency or, more likely, an independent pulsation mode. In the latter case Nu Eri would be both a Beta Cephei star and a slowly pulsating B (SPB) star. The photometric amplitudes of the individual pulsation modes of Nu Eri appear to have increased by about 20 per cent over the last 40 y...

  13. Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: II. Nonadiabatic analysis

    CERN Document Server

    Córsico, Alejandro H

    2016-01-01

    Low-mass ($M_{\\star}/M_{\\sun} \\lesssim 0.45$) white dwarfs, including the so called extremely low-mass white dwarfs (ELM, $M_{\\star}/M_{\\sun } \\lesssim 0.18-0.20$), are being currently discovered in the field of our Galaxy through dedicated photometric surveys. The fact that some of them pulsate opens the unparalleled chance for sounding their interiors. We present a detailed nonadiabatic pulsational analysis of such stars based on a new set of He-core white-dwarf models with masses ranging from $0.1554$ to $0.4352 M_{\\sun}$ derived by computing the non-conservative evolution of a binary system consisting of an initially $1 M_{\\sun}$ ZAMS star and a $1.4 M_{\\sun}$ neutron star. We have computed nonadiabatic radial modes and nonradial g and p modes to assess the dependence of the pulsational stability properties of these objects with stellar parameters such as the stellar mass, the effective temperature, and the convective efficiency. We found that a dense spectrum of unstable radial modes and nonradial g and ...

  14. Tuning nonradiative lifetimes via molecular aggregation

    CERN Document Server

    Celestino, A

    2016-01-01

    We show that molecular aggregation can strongly influence the nonradiative decay (NRD) lifetime of an electronic excitation. As a demonstrative example, we consider a transition-dipole-dipole-interacting dimer whose monomers have harmonic potential energy surfaces (PESs). Depending on the position of the NRD channel ($q_{\\rm nr}$), we find that the NRD lifetime ($\\tau_{\\rm nr}^{\\rm dim}$) can exhibit a completely different dependence on the intermolecular-interaction strength. We observe that (i) for $q_{\\rm nr}$ near the Franck-Condon region, $\\tau_{\\rm nr}^{\\rm dim}$ increases with the interaction strength; (ii) for $q_{\\rm nr}$ near the minimum of the monomer excited PES, the intermolecular interaction has little influence on $\\tau_{\\rm nr}^{\\rm dim}$; (iii) for $q_{\\rm nr}$ near the classical turning point of the monomer nuclear dynamics, on the other side of the minimum, $\\tau_{\\rm nr}^{\\rm dim}$ decreases with the interaction strength. Our findings suggest design principles for molecular systems where a...

  15. Mode selection in pulsating stars

    CERN Document Server

    Smolec, R

    2013-01-01

    In this review we focus on non-linear phenomena in pulsating stars the mode selection and amplitude limitation. Of many linearly excited modes only a fraction is detected in pulsating stars. Which of them and why (the problem of mode selection) and to what amplitude (the problem of amplitude limitation) are intrinsically non-linear and still unsolved problems. Tools for studying these problems are briefly discussed and our understanding of mode selection and amplitude limitation in selected groups of self-excited pulsators is presented. Focus is put on classical pulsators (Cepheids and RR Lyrae stars) and main sequence variables (delta Scuti and beta Cephei stars). Directions of future studies are briefly discussed.

  16. Sacler lectures

    CERN Document Server

    Bernstein, J

    1995-01-01

    The series of three lectures given at Tel-Aviv University in 1992: 1. Tensor categories. 2. Quantum groups. 3. Topological (quantum) field theories. Published as the preprint IAS 897-92 of Tel-Aviv University and The Mortimer and Raymond Sacler Institute of Advanced Studies.

  17. SEISMOLOGY OF A MASSIVE PULSATING HYDROGEN ATMOSPHERE WHITE DWARF

    Energy Technology Data Exchange (ETDEWEB)

    Kepler, S. O.; Pelisoli, Ingrid; Pecanha, Viviane; Costa, J. E. S. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, RS (Brazil); Fraga, Luciano [Southern Observatory for Astrophysical Research, Casilla 603, La Serena (Chile); Hermes, J. J.; Winget, D. E.; Castanheira, Barbara [Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712-1083 (United States); Corsico, A. H.; Romero, A. D.; Althaus, Leandro [Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata (Argentina); Kleinman, S. J.; Nitta, A. [Gemini Observatory, Northern Operations Center, 670 North A' ohoku Place, Hilo, HI 96720 (United States); Koester, D. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Kiel, D-24098 Kiel (Germany); Kuelebi, Baybars [Institut de Ciencies de L' Espai, Universitat Autonoma de Barcelon and Institute for Space Studies of Catalonia, c/Gran Capita 2-4, Edif. Nexus 104, E-08034 Barcelona (Spain); Jordan, Stefan [Astronomisches Rechen-Institut, ZAH, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany); Kanaan, Antonio, E-mail: kepler@if.ufrgs.br [Departamento de Fisica, Universidade Federal de Santa Catarina, Florianopolis, SC (Brazil)

    2012-10-01

    We report our observations of the new pulsating hydrogen atmosphere white dwarf SDSS J132350.28+010304.22. We discovered periodic photometric variations in frequency and amplitude that are commensurate with nonradial g-mode pulsations in ZZ Ceti stars. This, along with estimates for the star's temperature and gravity, establishes it as a massive ZZ Ceti star. We used time-series photometric observations with the 4.1 m SOAR Telescope, complemented by contemporary McDonald Observatory 2.1 m data, to discover the photometric variability. The light curve of SDSS J132350.28+010304.22 shows at least nine detectable frequencies. We used these frequencies to make an asteroseismic determination of the total mass and effective temperature of the star: M{sub *} = 0.88 {+-} 0.02 M{sub Sun} and T{sub eff} = 12, 100 {+-} 140 K. These values are consistent with those derived from the optical spectra and photometric colors.

  18. Pulsations of rapidly rotating stars: I. The ACOR numerical code

    CERN Document Server

    Ouazzani, Rhita-Maria; Reese, Daniel

    2012-01-01

    Very high precision seismic space missions such as CoRoT and Kepler provide the means of testing the modeling of transport processes in stellar interiors. For some stars, such as solar-like and red giant stars, a rotational splitting is measured. However, in order to fully exploit these splittings and constrain the rotation profile, one needs to be able to calculate them accurately. For some other stars, such as $\\delta$ Scuti and Be stars, for instance, the observed pulsation spectra are modified by rotation to such an extent that a perturbative treatment of the effects of rotation is no longer valid. We present here a new two-dimensional non-perturbative code, called ACOR (\\textit{Adiabatic Code of Oscillation including Rotation}) which allows us to compute adiabatic non-radial pulsations of rotating stars, without making any assumptions on the sphericity of the star, the fluid properties (i.e. baroclinicity) or the rotation profile. The 2D non-perturbative calculations fully take into account the centrifug...

  19. Spectroscopic Pulsational Frequency Identification and Mode Determination of {\\gamma} Doradus Star HD 12901

    CERN Document Server

    Brunsden, E; Cottrell, P L; Wright, D J; De Cat, P

    2012-01-01

    Using multi-site spectroscopic data collected from three sites, the frequencies and pulsational modes of the {\\gamma} Doradus star HD 12901 were identified. A total of six frequencies in the range 1-2 c/d were observed, their identifications supported by multiple line-profile measurement techniques and previously-published photometry. Five frequencies were of sufficient signal-to-noise for mode identification and all five displayed similar three-bump standard deviation profiles which were fitted well with (l,m)=(1,1) modes. These fits had reduced chi-squared values of less than 18. We propose that this star is an excellent candidate to test models of non-radially pulsating {\\gamma} Doradus stars as a result of the presence of multiple (1,1) modes.

  20. The Effects of Element Diffusion on the Pulsational Properties of Variable DA White Dwarf Stars

    CERN Document Server

    Corsico, A H; Althaus, L G; Serenelli, A M

    2002-01-01

    We explore the effects of element diffusion due to gravitational settling and thermal and chemical diffusion on the pulsational properties of DA white dwarfs. To this end, we employ an updated evolutionary code coupled with a pulsational, finite difference code for computing the linear, non-radial g-modes in the adiabatic approximation. We follow the evolution of a 0.55 \\msun white dwarf model in a self-consistent way with the evolution of chemical abundance distribution as given by time dependent diffusion processes. Results are compared with the standard treatment of diffusive equilibrium in the trace element approximation. Appreciable differences are found between the two employed treatments. We conclude that time dependent element diffusion plays an important role in determining the whole oscillation pattern and the temporal derivative of the periods in DAV white dwarfs. In addition, we discuss the plausibility of the standard description employed in accounting for diffusion in most of white dwarf asteros...

  1. Pulsating Star Mystery Solved

    Science.gov (United States)

    2010-11-01

    By discovering the first double star where a pulsating Cepheid variable and another star pass in front of one another, an international team of astronomers has solved a decades-old mystery. The rare alignment of the orbits of the two stars in the double star system has allowed a measurement of the Cepheid mass with unprecedented accuracy. Up to now astronomers had two incompatible theoretical predictions of Cepheid masses. The new result shows that the prediction from stellar pulsation theory is spot on, while the prediction from stellar evolution theory is at odds with the new observations. The new results, from a team led by Grzegorz Pietrzyński (Universidad de Concepción, Chile, Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), appear in the 25 November 2010 edition of the journal Nature. Grzegorz Pietrzyński introduces this remarkable result: "By using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile, along with other telescopes, we have measured the mass of a Cepheid with an accuracy far greater than any earlier estimates. This new result allows us to immediately see which of the two competing theories predicting the masses of Cepheids is correct." Classical Cepheid Variables, usually called just Cepheids, are unstable stars that are larger and much brighter than the Sun [1]. They expand and contract in a regular way, taking anything from a few days to months to complete the cycle. The time taken to brighten and grow fainter again is longer for stars that are more luminous and shorter for the dimmer ones. This remarkably precise relationship makes the study of Cepheids one of the most effective ways to measure the distances to nearby galaxies and from there to map out the scale of the whole Universe [2]. Unfortunately, despite their importance, Cepheids are not fully understood. Predictions of their masses derived from the theory of pulsating stars are 20-30% less than predictions from the theory of the

  2. [Bachelard and the mathematical pulsation].

    Science.gov (United States)

    Guitart, René

    2015-01-01

    The working mathematician knows a specific gesture named « mathematical pulsation », a necessary creative moving in diagrams of thoughts and interpretations of mathematical writings. In this perspective the fact of being an object is definitely undecided, and related to the game of relations. The purpose of this paper today is to construct this pulsation, starting from the epistemology of Bachelard, concerning mathematics as well as mathematical physics. On the way, we recover links between ideas of Bachelard and more recent specific propositions by Gilles Ch-let, Charles Alunni, or René Guitart. Also are used authors like Jacques Lacan, Arthur Koestler, Alfred N. Whitehead, Charles S. Peirce. We conclude that the mathematical work consists with pulsative moving in the space of diagrams; we claim that this view is well compatible with the Bachelard's analysis of scientific knowledge: the intellectual or formal mathematical data preceeds the empirical objects, and in some sense these objects result from the pulsative gestures of the thinkers. So we finish with a categorical scheme of the pulsation.

  3. Whole Earth Telescope observations of the pulsating subdwarf B star PG 0014+067

    CERN Document Server

    Vuckovic, M; O'Toole, S; Csubry, Z; Baran, A; Zola, S; Moskalik, P; Klumpe, E W; Riddle, R; O'Brien, M S; Mullally, F; Wood, M A; Wilkat, V; Zhou, A Y; Reed, M D; Terndrup, D M; Sullivan, D J; Kim, S L; Chen, W P; Chen, C W; Hsiao, W S; Sanchawala, K; Lee, H T; Jiang, X J; Janulis, R; Siwak, M; Ogloza, W; Paparo, M; Bognár, Z; Sodor, A; Handler, G; Lorenz, D; Steininger, B; Silvotti, R; Vauclair, G; Oreiro, R; Ostensen, R; Bronowska, A; Castanheira, B G; Kepler, S O; Fraga, L; Shipman, H L; Provencal, J L; Childers, D

    2006-01-01

    PG 0014+067 is one of the most promising pulsating subdwarf B stars for seismic analysis, as it has a rich pulsation spectrum. The richness of its pulsations, however, poses a fundamental challenge to understanding the pulsations of these stars, as the mode density is too complex to be explained only with radial and nonradial low degree (l < 3) p-modes without rotational splittings. One proposed solution, for the case of PG 0014+067 in particular, assigns some modes with high degree (l=3). On the other hand, theoretical models of sdB stars suggest that they may retain rapidly rotating cores, and so the high mode density may result from the presence of a few rotationally-split triplet (l=1), quintuplet (l=2) modes, along with radial (l=0) p-modes. To examine alternative theoretical models for these stars, we need better frequency resolution and denser longitude coverage. Therefore, we observed this star with the Whole Earth Telescope for two weeks in October 2004. In this paper we report the results of Whol...

  4. A pulsation zoo in the hot subdwarf B star KIC 10139564 observed by Kepler

    CERN Document Server

    Baran, A S; Stello, D; Ostensen, R H; Telting, J H; Pakstiene, E; O'Toole, S J; Silvotti, R; Degroote, P; Bloemen, S; Hu, H; Van Grootel, V; Clarke, B D; Van Cleve, J; Thompson, S E; Kawaler, S D

    2012-01-01

    We present our analyses of 15 months of Kepler data on KIC 10139564. We detected 57 periodicities with a variety of properties not previously observed all together in one pulsating subdwarf B star. Ten of the periodicities were found in the low-frequency region, and we associate them with nonradial g-modes. The other periodicities were found in the high-frequency region, which are likely p-modes. We discovered that most of the periodicities are components of multiplets with a common spacing. Assuming that multiplets are caused by rotation, we derive a rotation period of 25.6(1.8) days. The multiplets also allow us to identify the pulsations to an unprecedented extent for this class of pulsator. We also detect l<=2 multiplets, which are sensitive to the pulsation inclination and can constrain limb darkening via geometric cancellation factors. While most periodicities are stable, we detected several regions that show complex patterns. Detailed analyses showed these regions are complicated by several factors....

  5. Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: I. Adiabatic properties

    CERN Document Server

    Córsico, A H

    2014-01-01

    The discovery of pulsations in some low-mass white dwarfs, including the so-called extremely low-mass white dwarfs, has opened the unprecedented opportunity of probing the internal structure of these ancient stars. We present a detailed adiabatic pulsational study of these stars based on a new set of He-core white-dwarf models with masses ranging from $0.1554$ to $0.4352 M_{\\odot}$ derived by computing the non-conservative evolution of a binary system consisting of an initially $1 M_{\\odot}$ ZAMS star and a $1.4 M_{\\odot}$ neutron star. We computed adiabatic radial ($\\ell= 0$) and non-radial ($\\ell= 1, 2$) $p$ and $g$ modes to assess the dependence of the pulsational properties of these objects on stellar parameters such as the stellar mass and the effective temperature, as well as the effects of element diffusion. We found that for white dwarf models with masses below $\\sim 0.18 M_{\\odot}$, $g$ modes mainly probe the core regions and $p$ modes the envelope, therefore pulsations offer the opportunity of const...

  6. Summary Lecture

    Indian Academy of Sciences (India)

    J. O. Stenflo

    2000-09-01

    This summary lecture makes no attempt to summarize what was actually said at the meeting, since this is well covered by the other contributors. Instead I have structured my presentation in three parts: First I try to demonstrate why the Sun is unique by comparing it with laboratory plasmas. This is followed by some personal reminiscences that go back a significant fraction of the century. I conclude in the form of a poem about this memorable conference in honor of the centennial anniversary of the Kodaikanal Observatory.

  7. Nonradiative charge transfer in collisions of protons with rubidium atoms

    Institute of Scientific and Technical Information of China (English)

    Yan Ling-Ling; Qu Yi-Zhi; Liu Chun-Hua; Zhang Yu; Wang Jian-Guo; Buenker Robert J

    2012-01-01

    The nonradiative charge-transfer cross sections for protons colliding with Rb(5s) atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10-3 keV 10 keV.The total and state-selective charge-transfer cross sections are in good agreement with the experimental data in the relatively low energy region.The importance of rotational coupling for chargetransfer process is stressed.Compared with the radiative charge-transfer process,nonradiative charge transfer is a dominant mechanism at energies above 15 eV.The resonance structures of state-selective charge-transfer cross sections arising from the competition among channels are analysed in detail.The radiative and nonradiative charge-transfer rate coefficients from low to high temperature are presented.

  8. Pulsational-Pair Instability Supernovae

    CERN Document Server

    Woosley, S E

    2016-01-01

    The final evolution of stars in the mass range 60 - 150 solar masses is explored. Depending upon their mass loss and rotation rates, many of these stars will end their lives as pulsational pair-instability supernovae. Even a non-rotating 70 solar mass star is pulsationally unstable during oxygen shell burning and can power a sub-luminous supernova. Rotation decreases the limit further. For more massive stars, the pulsations are less frequent, span a longer time, and are more powerful. Violent pulsations eject not only any residual low density envelope, but also that fraction of the helium core mass outside about 35 - 50 solar masses. The remaining core of helium and heavy elements continues to evolve, ultimately forming an iron core of about 2.5 solar masses that probably collapses to a black hole. A variety of observational transients result with total durations ranging from days to 10,000 years, and luminosities from 10$^{41}$ to 10$^{44}$ erg s$^{-1}$. Many transients resemble ordinary Type IIp supernovae,...

  9. Four new subdwarf B pulsators

    Science.gov (United States)

    Østensen, R.; Heber, U.; Silvotti, R.; Solheim, J.-E.; Dreizler, S.; Edelmann, H.

    2001-11-01

    We report the detection of short period oscillations in the sdB stars HS 0039+4302, HS 0444+0408, HS 1824+5745 and HS 2151+0857 from time-series photometry made at the Nordic Optical Telescope (NOT) of a sample of 55 candidates. Hence these four hot subdwarfs are new members of the EC 14026 class of pulsating sdB stars. HS 0039+4302 is a multi-mode pulsator with at least four distinct periods in the range between 182 and 234 s, and amplitudes up to 8 mma. HS 0444+0408 shows one dominant pulsation at 137 s (A ~ 12 mma) and a second weaker pulsation at 170 s (A ~ 3 mma). For HS 1824+5745 we find a single period of 139 s with an amplitude of about 5 mma. HS 2151+0857 shows four periods in the range 129-151 s with amplitudes between 2 and 5 mma. Our NLTE model atmosphere analysis of the time-averaged optical spectra place all stars well within the theoretical sdBV instability strip. Based on observations obtained at the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. }\\fnmsep\\thanks{ Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Plank-Institute für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy. Based on observations collected at the European Southern Observatory, Chile (ESO No. 66.D-0031).

  10. ENIGMATIC RECURRENT PULSATIONAL VARIABILITY OF THE ACCRETING WHITE DWARF EQ LYN (SDSS J074531.92+453829.6)

    Energy Technology Data Exchange (ETDEWEB)

    Mukadam, Anjum S.; Szkody, Paula [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Townsley, D. M.; Brockett, T. [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States); Gaensicke, B. T.; Parsons, S. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Southworth, J. [Astrophysics Group, Keele University, Staffordshire ST5 5BG (United Kingdom); Hermes, J. J.; Montgomery, M. H.; Winget, D. E.; Harrold, S. [Department of Astronomy, University of Texas at Austin, Austin, TX 78759 (United States); Tovmassian, G.; Zharikov, S. [Observatorio Astronomico Nacional SPM, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ensenada, BC (Mexico); Drake, A. J. [Department of Astronomy and the Center for Advanced Computing Research, California Institute of Technology, Pasadena, CA 91225 (United States); Henden, A. [American Association of Variable Star Observers, 25 Birch Street, Cambridge, MA 02138 (United States); Rodriguez-Gil, P. [Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38204 Santa Cruz de Tenerife (Spain); Sion, E. M. [Department of Astronomy and Astrophysics, Villanova University, Villanova, PA 19085 (United States); Zola, S.; Szymanski, T. [Astronomical Observatory, Jagiellonian University, ul. Orla 171, PL-30-244 Krakow (Poland); Pavlenko, E. [Crimean Astrophysical Observatory, Crimea 98409 (Ukraine); and others

    2013-09-15

    Photometric observations of the cataclysmic variable EQ Lyn (SDSS J074531.92+453829.6), acquired from 2005 October to 2006 January, revealed high-amplitude variability in the range 1166-1290 s. This accreting white dwarf underwent an outburst in 2006 October, during which its brightness increased by at least five magnitudes, and it started exhibiting superhumps in its light curve. Upon cooling to quiescence, the superhumps disappeared and it displayed the same periods in 2010 February as prior to the outburst within the uncertainties of a couple of seconds. This behavior suggests that the observed variability is likely due to nonradial pulsations in the white dwarf star, whose core structure has not been significantly affected by the outburst. The enigmatic observations begin with an absence of pulsational variability during a multi-site campaign conducted in 2011 January-February without any evidence of a new outburst; the light curve is instead dominated by superhumps with periods in the range of 83-87 minutes. Ultraviolet Hubble Space Telescope time-series spectroscopy acquired in 2011 March reveals an effective temperature of 15,400 K, placing EQ Lyn within the broad instability strip of 10,500-16,000 K for accreting pulsators. The ultraviolet light curve with 90% flux from the white dwarf shows no evidence of any pulsations. Optical photometry acquired during 2011 and Spring 2012 continues to reflect the presence of superhumps and an absence of pulsations. Subsequent observations acquired in 2012 December and 2013 January finally indicate the disappearance of superhumps and the return of pulsational variability with similar periods as previous data. However, our most recent data from 2013 March to May reveal superhumps yet again with no sign of pulsations. We speculate that this enigmatic post-outburst behavior of the frequent disappearance of pulsational variability in EQ Lyn is caused either by heating the white dwarf beyond the instability strip due to an

  11. Why do hot subdwarf stars pulsate?

    CERN Document Server

    Geier, S

    2015-01-01

    Hot subdwarf B stars (sdBs) are the stripped cores of red giants located at the bluest extension of the horizontal branch. Several different kinds of pulsators are found among those stars. The mechanism that drives those pulsations is well known and the theoretically predicted instability regions for both the short-period p-mode and the long-period g-mode pulsators match the observed distributions fairly well. However, it remains unclear why only a fraction of the sdB stars pulsate, while stars with otherwise very similar parameters do not show pulsations. From an observers perspective I review possible candidates for the missing parameter that makes sdB stars pulsate or not.

  12. Head pulsations in a centrifugal pump

    Science.gov (United States)

    Boiko, V. S.; Sotnyk, M. I.; Moskalenko, V. V.

    2017-08-01

    This article investigated the factors, which affect to the character of the head pulsations of a centrifugal pump. We investigated the dependence of the shape and depth of these pulsations from the operation mode of the pump. Was determined, that the head pulsations at the outlet of the impeller (pulsations on the blade passing frequency) cause head pulsations at the outlet of the pump, that have the same frequency, but differ in shape and depth. These pulsations depend on the design features of the flow-through part of the pump (from the ratio of hydraulic losses on the friction and losses on the vortex formation). A feature of the researches that were conducted is also the using of not only hydraulic but also electric modeling methods. It allows determining the values of the components of hydraulic losses.

  13. Pulsations driven by the $\\epsilon$-mechanism in post-merger remnants: first results

    CERN Document Server

    Bertolami, Marcelo M Miller; Zhang, Xianfei; Althaus, Leandro G; Jeffery, C Simon

    2012-01-01

    Helium-rich subdwarfs are a rare subclass of hot subdwarf stars which constitute a small and inhomogeneous group showing varying degrees of helium enrichment. Only one star, LS IV $^\\circ$14 116 has been found to show multiperiodic luminosity variations. The variability of LS IV $^\\circ$14 116 has been explained as the consequence of nonradial g-mode oscillations, whose excitation is difficult to understand within the frame of the standard $\\kappa$-mechanism driving pulsations in sdBV stars. In a recent study, we have proposed that the pulsations of LS IV $^\\circ$14 116 might be driven through the $\\epsilon$-mechanism acting in unstable He-burning zones in the interior of the star, that appear before the quiescent He-burning phase. One of the few accepted scenarios for the formation of He-rich subdwarfs is the merger of two He-core white dwarfs. As part of this project, we present a study of the $\\epsilon$-mechanism in post-merger remnants, and discuss the results in the light of the pulsations exhibited by L...

  14. Non-Radial Oscillations in an Axisymmetric MHD Incompressible Fluid

    Indian Academy of Sciences (India)

    A. Satya Narayanan

    2000-09-01

    It is well known from Helioseismology that the Sun exhibits oscillations on a global scale, most of which are non-radial in nature. These oscillations help us to get a clear picture of the internal structure of the Sun as has been demonstrated by the theoretical and observational (such as GONG) studies. In this study we formulate the linearised equations of motion for non-radial oscillations by perturbing the MHD equilibrium solution for an axisymmetric incompressible fluid. The fluid motion and the magnetic field are expressed as scalars , , and , respectively. In deriving the exact solution for the equilibrium state, we neglect the contribution due to meridional circulation. The perturbed quantities *, *, *, * are written in terms of orthogonal polynomials. A special case of the above formulation and its stability is discussed.

  15. Nonradiative limitations to plasmon propagation in chains of metallic nanoparticles

    CERN Document Server

    Brandstetter-Kunc, Adam; Downing, Charles A; Weinmann, Dietmar; Jalabert, Rodolfo A

    2016-01-01

    We investigate the collective plasmonic modes in a chain of metallic nanoparticles that are coupled by near-field interactions. The size- and momentum-dependent nonradiative Landau damping and radiative decay rates are calculated analytically within an open quantum system approach. These decay rates determine the excitation propagation along the chain. In particular, the behavior of the radiative decay rate as a function of the plasmon wavelength leads to a transition from an exponential decay of the collective excitation for short distances to an algebraic decay for large distances. Importantly, we show that the exponential decay is of a purely nonradiative origin. Our transparent model enables us to provide analytical expressions for the polarization-dependent plasmon excitation profile along the chain and for the associated propagation length. Our theoretical analysis constitutes an important step in the quest for the optimal conditions for plasmonic propagation in nanoparticle chains.

  16. Variability and pulsations in the Be star 66 Ophiuchi

    Science.gov (United States)

    Floquet, M.; Neiner, C.; Janot-Pacheco, E.; Hubert, A. M.; Jankov, S.; Zorec, J.; Briot, D.; Chauville, J.; Leister, N. V.; Percy, J. R.; Ballereau, D.; Bakos, A. G.

    2002-10-01

    66 Oph is a Be star seen under a moderate inclination angle that shows strong variability from UV to IR wavelengths. A concise review of long-term variability history is given. High resolution, high S/N spectroscopic observations obtained in 1997, 1998 and 2001 and spectropolarimetric observations obtained in 2000 are presented. These observations occurred during a long-term decrease of Hα intensity. Fundamental parameters of the star have been revisited from Barbier-Chalonge-Divan (BCD) calibrations. New V sin i values are obtained using Fourier transforms applied to observed helium lines and a rotational frequency f_rot = 1.29 c d-1 is determined. Time series analysis and Fourier Doppler Imaging (FDI) of He I lines (4713, 4921, 5876 and 6678 Å) lead for the first time to the detection of multi-periodicity in 66 Oph. The two main frequencies found are f = 2.22 c d-1 and f = 4.05 c d-1 . They are attributed to non-radial pulsations and can be associated with mode degree l = 2 and l = 3, respectively. Inspection of Stokes V profiles suggests the presence of a weak Zeeman signature but further observations are needed to confirm the detection of a magnetic field in 66 Oph. Based on observations taken at OHP and Pic du Midi Observatory (France), at MBT/LNA (Brazil) and on Brazilian observing time at La Silla (ESO, Chile).

  17. SHORT-PERIOD g-MODE PULSATIONS IN LOW-MASS WHITE DWARFS TRIGGERED BY H-SHELL BURNING

    Energy Technology Data Exchange (ETDEWEB)

    Córsico, A. H.; Althaus, L. G., E-mail: acorsico@fcaglp.unlp.edu.ar [Grupo de Evolución Estelar y Pulsaciones, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata (Argentina)

    2014-09-20

    The detection of pulsations in white dwarfs with low mass offers the possibility of probing their internal structures through asteroseismology and placing constraints on the binary evolutionary processes involved in their formation. In this Letter, we assess the impact of stable H burning on the pulsational stability properties of low-mass He-core white dwarf models resulting from binary star evolutionary calculations. We found that besides a dense spectrum of unstable radial modes and nonradial g and p modes driven by the κ mechanism due to the partial ionization of H in the stellar envelope, some unstable g modes with short pulsation periods are also powered by H burning via the ε mechanism of mode driving. This is the first time that ε destabilized modes are found in models representative of cool white dwarf stars. The short periods recently detected in the pulsating low-mass white dwarf SDSS J111215.82+111745.0 could constitute the first evidence of the existence of stable H burning in these stars, in particular in the so-called extremely low-mass white dwarfs.

  18. First Kepler results on compact pulsators - I. Survey target selection and the first pulsators

    Science.gov (United States)

    Østensen, R. H.; Silvotti, R.; Charpinet, S.; Oreiro, R.; Handler, G.; Green, E. M.; Bloemen, S.; Heber, U.; Gänsicke, B. T.; Marsh, T. R.; Kurtz, D. W.; Telting, J. H.; Reed, M. D.; Kawaler, S. D.; Aerts, C.; Rodríguez-López, C.; Vučković, M.; Ottosen, T. A.; Liimets, T.; Quint, A. C.; Van Grootel, V.; Randall, S. K.; Gilliland, R. L.; Kjeldsen, H.; Christensen-Dalsgaard, J.; Borucki, W. J.; Koch, D.; Quintana, E. V.

    2010-12-01

    We present results from the first two quarters of a survey to search for pulsations in compact stellar objects with the Kepler spacecraft. The survey sample and the various methods applied in its compilation are described, and spectroscopic observations are presented to separate the objects into accurate classes. From the Kepler photometry we clearly identify nine compact pulsators and a number of interesting binary stars. Of the pulsators, one shows the strong, rapid pulsations typical of a V361 Hya-type sdB variable (sdBV); seven show long-period pulsation characteristics of V1093 Her-type sdBVs; and one shows low-amplitude pulsations with both short and long periods. We derive effective temperatures and surface gravities for all the subdwarf B stars in the sample and demonstrate that below the boundary region where hybrid sdB pulsators are found, all our targets are pulsating. For the stars hotter than this boundary temperature a low fraction of strong pulsators (region, and several of the V1093 Her pulsators show low-amplitude modes in the short-period region, indicating that hybrid behaviour may be common in these stars, also outside the boundary temperature region where hybrid pulsators have hitherto been found.

  19. Enhancements of Impinging Flame by Pulsation

    Institute of Scientific and Technical Information of China (English)

    AySu; Ying-ChiehLiu

    2000-01-01

    Experimental investigations on the pulsating jet-impinging diffusion flame were executed.A soleoid valve was aligned upstream of the jet orifice and the methane fuel was controlled in open-closed cycles from 0 Hz to 20Hz.Results show that the open-closed cycles,indeed increase the fluctuations of the methane fuel obviously.The evolutions of pulsating flame therefore develop faster than the continuous impinging flame.The optimized pulating frequencies are near 9 to 11 hz from the Re=170 to 283.The temperature differences between that under optimized pulsating rate and full open condition(no pulsation)are ranging from 100 to 150 degree.The pulsating effect is more singnificant at low Reynolds number.The cross section of continuous impinging flame behaves as elliptic shape with axial ratio equals to 2/3.The tip of the impinging flame obviously crosses at 42mm above the impinging point.ecause of the phenomenon of pulsation flame,the flame sheet or flame front may not be identified clearly in the averaged temperature contours.Results shows that the averaged end-contour of pulsation flame rears at 38mm above the impinging point.By observation and experiment,the pulsating flame behaves more stable and efficient than the continuous impinging flame.

  20. Self-pulsation in Raman fiber amplifiers

    DEFF Research Database (Denmark)

    Pedersen, Martin Erland Vestergaard; Ott, Johan Raunkjær; Rottwitt, Karsten

    2009-01-01

    Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated.......Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated....

  1. Industry Lecture 2010

    DEFF Research Database (Denmark)

    Kragh, Helge

    2010-01-01

    Sammendrag af "Industry Lecture", Norsk Kjemisk Selskap, Universitetet i Oslo, givet 15/10 2010.......Sammendrag af "Industry Lecture", Norsk Kjemisk Selskap, Universitetet i Oslo, givet 15/10 2010....

  2. Industry Lecture 2010

    DEFF Research Database (Denmark)

    Kragh, Helge

    2010-01-01

    Sammendrag af "Industry Lecture", Norsk Kjemisk Selskap, Universitetet i Oslo, givet 15/10 2010.......Sammendrag af "Industry Lecture", Norsk Kjemisk Selskap, Universitetet i Oslo, givet 15/10 2010....

  3. Attention Breaks in Lectures

    Science.gov (United States)

    Johnstone, A. H.; Percival, F.

    1976-01-01

    Describes research into student attention patterns during lectures that suggests that student attention declines steadily during a lecture, and that the rate of decrease is dependent upon several variables including subject difficulty. (MLH)

  4. TransLectures

    OpenAIRE

    Silvestre Cerdà, Joan Albert; Del Agua Teba, Miguel Angel; Garcés Díaz-Munío, Gonzalo Vicente; GASCÓ MORA, GUILLEM; Giménez Pastor, Adrián; Martínez-Villaronga, Adrià Agustí; Pérez González de Martos, Alejandro Manuel; Sánchez-Cortina, Isaías; Serrano Martínez-Santos, Nicolás; Spencer, Rachel Nadine; Valor Miró, Juan Daniel; Andrés Ferrer, Jesús; Civera Saiz, Jorge; Sanchis Navarro, José Alberto; Juan Císcar, Alfonso

    2012-01-01

    transLectures (Transcription and Translation of Video Lectures) is an EU STREP project in which advanced automatic speech recognition and machine translation techniques are being tested on large video lecture repositories. The project began in November 2011 and will run for three years. This paper will outline the project¿s main motivation and objectives, and give a brief description of the two main repositories being considered: VideoLectures.NET and poliMedia. The first re...

  5. Blood Pulsation Intensity Video Mapping

    CERN Document Server

    Borges, Pedro Henrique de M

    2016-01-01

    In this study, we make non-invasive, remote, passive measurements of the heart beat frequency and determine the map of blood pulsation intensity in a region of interest (ROI) of skin. The ROI used was the forearm of a volunteer. The method employs a regular video camera and visible light, and the video acquisition takes less than 1 minute. The mean cardiac frequency found in our volunteer was within 1 bpm of the ground-truth value simultaneously obtained via earlobe plethysmography. Using the signals extracted from the video images, we have determined an intensity map for the blood pulsation at the surface of the skin. In this paper we present the experimental and data processing details of the work and well as limitations of the technique. ----------------------------------------- Neste estudo medimos a frequ\\^encia card\\'iaca de forma n\\~ao invasiva, remota e passiva e determinamos o mapa da atividade de pulsa\\c{c}\\~ao sangu\\'inea numa regi\\~ao de interesse (ROI) da pele. A ROI utilizada foi o antebra\\c{c}o...

  6. Pulsating star research from Antarctica

    Science.gov (United States)

    Chadid, Merieme

    2017-09-01

    This invited talk discusses the pulsating star research from the heart of Antarctica and the scientific polar challenges in the extreme environment of Antarctica, and how the new polar technology could cope with unresolved stellar pulsation enigmas and evolutionary properties challenges towards an understanding of the mysteries of the Universe. PAIX, the first robotic photometer Antarctica program, has been successfully launched during the polar night 2007. This ongoing program gives a new insight to cope with unresolved stellar enigmas and stellar oscillation challenges with a great opportunity to benefit from an access to the best astronomical site on Earth, Dome C. PAIX achieves astrophysical measurement time-series of stellar fields, challenging photometry from space. A continuous and an uninterrupted series of multi-color photometric observations has been collected each polar night - 150 days - without regular interruption, Earth's rotation effect. PAIX shows the first light curve from Antarctica and first step for the astronomy in Antarctica giving new insights in remote polar observing runs and robotic instruments towards a new technology.

  7. Occurrence and average behavior of pulsating aurora

    Science.gov (United States)

    Partamies, N.; Whiter, D.; Kadokura, A.; Kauristie, K.; Nesse Tyssøy, H.; Massetti, S.; Stauning, P.; Raita, T.

    2017-05-01

    Motivated by recent event studies and modeling efforts on pulsating aurora, which conclude that the precipitation energy during these events is high enough to cause significant chemical changes in the mesosphere, this study looks for the bulk behavior of auroral pulsations. Based on about 400 pulsating aurora events, we outline the typical duration, geomagnetic conditions, and change in the peak emission height for the events. We show that the auroral peak emission height for both green and blue emission decreases by about 8 km at the start of the pulsating aurora interval. This brings the hardest 10% of the electrons down to about 90 km altitude. The median duration of pulsating aurora is about 1.4 h. This value is a conservative estimate since in many cases the end of event is limited by the end of auroral imaging for the night or the aurora drifting out of the camera field of view. The longest durations of auroral pulsations are observed during events which start within the substorm recovery phases. As a result, the geomagnetic indices are not able to describe pulsating aurora. Simultaneous Antarctic auroral images were found for 10 pulsating aurora events. In eight cases auroral pulsations were seen in the southern hemispheric data as well, suggesting an equatorial precipitation source and a frequent interhemispheric occurrence. The long lifetimes of pulsating aurora, their interhemispheric occurrence, and the relatively high-precipitation energies make this type of aurora an effective energy deposition process which is easy to identify from the ground-based image data.

  8. Laughter in University Lectures

    Science.gov (United States)

    Nesi, Hilary

    2012-01-01

    This paper analyses laughter in spoken academic discourse, with the aim of discovering why lecturers provoke laughter in their lectures. A further purpose of the paper is to identify episodes in British data which may differ from those in other cultural contexts where other lecturing practices prevail, and thus to inform the design of study skills…

  9. A Planet Found by Pulsations

    Science.gov (United States)

    Kohler, Susanna

    2016-10-01

    Searching for planets around very hot stars is much more challenging than looking around cool stars. For this reason, the recent discovery of a planet around a main-sequence A star is an important find both because of its unique position near the stars habitable zone, and because of the way in which the planet was discovered.Challenges in VariabilityIn the past three decades, weve discovered thousands of exoplanets yet most of them have been found around cool stars (like M dwarfs) or moderate stars (like G stars like our Sun). Very few of the planets that weve found orbit hot stars; in fact, weve only discovered ~20 planets orbiting the very hot, main-sequence A stars.The instability strip, indicated on an H-R diagram. Stellar classification types are listed across the bottom of the diagram. Many main-sequence A stars reside in the instability strip. [Rursus]Why is this? We dont expect that main-sequence A stars host fewer planets than cooler stars. Instead, its primarily because the two main techniques that we use to find planets namely, transits and radial velocity cant be used as effectively on the main-sequence A stars that are most likely to host planets, because the luminosities of these stars are often variable.These stars can lie on whats known as the classical instability strip in the Herzsprung-Russell diagram. Such variable stars pulsate due to changes in the ionization state of atoms deep in their interiors, which causes the stars to puff up and then collapse back inward. For variable main-sequence A stars, the periods for these pulsations can be several to several tens of times per day.These very pulsations that make transits and radial-velocity measurements so difficult, however, can potentially be used to detect planets in a different way. Led by Simon Murphy (University of Sydney, Australia and Aarhus University, Denmark), a team of scientists has recently detected the first planet ever to be discovered around a main-sequence A star from the timing

  10. Fourier decomposition and frequency analysis of the pulsating stars with P < 1day in the OGLE database. II. Multiperiodic RR Lyrae variables in the Galactic Bulge

    CERN Document Server

    Moskalik, P

    2003-01-01

    We present the results of a systematic search for multiperiodic pulsators among the Galactic Bulge RR Lyrae stars of the OGLE-1 sample. We identify one "canonical" double-mode variable (RRd star) pulsating in two radial modes. In 38 stars we detect secondary periodicities very close to the primary pulsation frequency. This type of multiperiodic variables constitute ~23% of RRab and ~5% of RRc population of the Bulge. With the observed period ratios of 0.95-1.02 the secondary periods must correspond to nonradial modes of oscillation. Their beating with the primary (radial) pulsation leads to a long-term amplitude and phase modulation, known as the Blazhko effect. The Blazhko RRab variables occur more frequently in the Galactic Bulge than in the LMC. The opposite tendency is seen in case of the RRd stars. The differences of incidence rates are most likely caused by different metallicity of the two populations. We discuss pulsation properties of the OGLE-1 Blazhko stars and compare them with predictions of theor...

  11. Pulsating low-mass white dwarfs in the frame of new evolutionary sequences. I. Adiabatic properties

    Science.gov (United States)

    Córsico, A. H.; Althaus, L. G.

    2014-09-01

    Context. Many low-mass white dwarfs with masses M∗/M⊙ ≲ 0.45, including the so-called extremely low-mass white dwarfs (M∗/M⊙ ≲ 0.20 - 0.25), have recently been discovered in the field of our Galaxy through dedicated photometric surveys. The subsequent discovery of pulsations in some of them has opened the unprecedented opportunity of probing the internal structure of these ancient stars. Aims: We present a detailed adiabatic pulsational study of these stars based on full evolutionary sequences derived from binary star evolution computations. The main aim of this study is to provide a detailed theoretical basis of reference for interpreting present and future observations of variable low-mass white dwarfs. Methods: Our pulsational analysis is based on a new set of He-core white-dwarf models with masses ranging from 0.1554 to 0.4352 M⊙ derived by computing the non-conservative evolution of a binary system consisting of an initially 1 M⊙ ZAMS star and a 1.4 M⊙ neutron star. We computed adiabatic radial (ℓ = 0) and non-radial (ℓ = 1,2) p and g modes to assess the dependence of the pulsational properties of these objects on stellar parameters such as the stellar mass and the effective temperature, as well as the effects of element diffusion. Results: We found that for white dwarf models with masses below ~ 0.18 M⊙, g modes mainly probe the core regions and p modes the envelope, therefore pulsations offer the opportunity of constraining both the core and envelope chemical structure of these stars via asteroseismology. For models with M∗ ≳ 0.18 M⊙, on the other hand, g modes are very sensitive to the He/H compositional gradient and therefore can be used as a diagnostic tool for constraining the H envelope thickness. Because both types of objects have not only very distinct evolutionary histories (according to whether the progenitor stars have experienced CNO-flashes or not), but also have strongly different pulsation properties, we propose to

  12. Piezoelectric actuator for pulsating jets

    Science.gov (United States)

    Brissaud, Michel; Gonnard, Paul; Bera, Jean-Christophe; Sunyach, Michel

    2000-08-01

    Recent researches in aeronautics showed that fluidic actuator systems could offer possibilities for drag reduction and lift improvement. To this end many actuator types were designed. This paper deals with the design, fabrication and test of piezoelectric actuator in order to generate pulsated jets normal to a surface and control air flow separation. It is based on the flexural displacement of a rectangular metal plate clamped on one of its large edge. Piezoelectric patches cemented on the plate were used for driving into vibration the actuator. Experimental measurements show that pulsed flow velocities are adjustable from 1.5m/s to 35m/s through a 100x1mm2 slit andwithin a 100 to 400 Hz frequency range. Prototype provides the jet performances classically required for active control flow.

  13. Pulsative hematoma: A penile fracture complication

    Directory of Open Access Journals (Sweden)

    Nale Đorđe

    2007-01-01

    Full Text Available Background. Fracture of the penis is a direct blunt trauma of the erect or semi-erect penis. It can be treated by conservative or surgical means. Retrospective analyses of conservative penile fracture treatment reveal frequent immediate and later complications. Case report. We presented a 41- year-old patient with pulsative hematoma caused by an unusual fracture of the penis. Fracture had appeared 40 days before the admittance during a sexual intercourse. The patient was treated surgically. Conclusion. Pulsative hematoma (pulsative diverticulum is a very rare, early complication of a conservatively treated penile fracture. Surgical treatment has an advantage over surgical one, which was confirmed by our case report.

  14. Self-pulsation in Raman fiber amplifiers

    OpenAIRE

    Pedersen, Martin Erland Vestergaard; Ott, Johan Raunkjær; Rottwitt, Karsten

    2009-01-01

    Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated.

  15. Stellar pulsation and rotation in NGC 6811

    Science.gov (United States)

    Rodríguez, E.; Ocando, S.; López-González, M. J.; Martín-Ruiz, S.

    2017-03-01

    We present the results of the frequency analysis for a selected sample of pulsating δ Sct- and γ Dor-type stars in the field of the open cluster NGC 6811, which have been observed in short-cadence (SC) mode by the Kepler satellite. In all cases, the resulting frequency spectra are very complex, especially when the dominant pulsation is that of the δ Sct type, that is, short-period pulsations corresponding to excited pressure (p) modes. In all cases, the δ Sct stars are shown to be essentially δ Sct/ γ Dor hybrid pulsators. However, the opposite seems not to be true. We also find that the δ Sct-type peaks commonly are not stable in amplitude. Many of the main peaks significantly change their amplitudes over relatively short time scales. For a large percentage of pulsators in our sample we also find that the variability shown in the light curves is not produced by a single cause, but a combination of various sources: δ Sct- and γ Dor-type pulsations together with rotational modulation produced by starspots in the surfaces of these stars. This is an indication of stellar activity in the surfaces of these relatively hot stars of spectral type A(-F). Sometimes, activity dominates the luminosity variations in various pulsating stars in our sample. Eclipsing binarity is also detected in a few cases. Flares are also detected in one of the δ Sct-type pulsators. This is an indication of unusual strong activity for this kind of hot stars.

  16. Statistical study of dayside pulsating aurora

    Science.gov (United States)

    Kanmae, T.; Kadokura, A.; Ogawa, Y.; Ebihara, Y.; Motoba, T.; Gerrard, A. J.; Weatherwax, A. T.

    2015-12-01

    Pulsating aurora normally occurs after a substorm breakup in the midnight sector, often observed to persist through the morning sector and beyond. Indeed, it has also been observed on the dayside; however, the characteristics of the dayside pulsating aurora are poorly known. A handful of observational studies have been reported, but the results are somewhat disputable because most of the studies had non-uniform sampling of the dark dayside region. Furthermore, the previous studies used photometer data, with which the spatial characteristics of the pulsating aurora cannot be examined. To determine both temporal and spatial characteristics of the pulsating aurora, we have studied three years of all-sky image data obtained at the South Pole station. Because of its unique geographical location, the station has 24 hours of darkness during the austral winter from April to August, providing an ideal platform for studying dayside aurora. In a preliminary survey of the data, we have identified the pulsating auroras in 198 days out of 365 days of observations. The magnetic local time (MLT) distribution of the occurrence peaks between 9:00 and 11:00, but shows no or little dependence on the geomagnetic activity. In many events, pulsating patches initially appear as east-west aligned arc segments and later in the afternoon sector develop into large, diffuse patches, which occasionally fill a large part of the field of view. Using the long-term data, we will statistically examine both temporal (occurrence rate, duration and pulsation period) and spatial (sizes and shapes) characteristics of the dayside pulsating aurora.

  17. A motion picture presentation of magnetic pulsations

    Science.gov (United States)

    Suzuki, A.; Kim, J. S.; Sugura, M.; Nagano, H.

    1981-01-01

    Using the data obtained from the IMS North American magnetometer network stations at high latitudes, a motion picture was made by a computer technique, describing time changes of Pc5 and Pi3 magnetic pulsation vectors. Examples of pulsation characteristics derived from this presentation are regional polarization changes including shifts of polarization demarcation lines, changes in the extent of an active region and its movement with time.

  18. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    Main Auditorium bldg. 500 Date Time Lecturer Title Monday 13 August 9:15 10:15 11:15 Student Session (3/3) Course Review Course Review Tuesday 14 August 16:00 Poster Session Further information can be obtained on the web at the following URL: Summer Student Lecture ProgrammeSummer Student Lectures are available at: http://agenda.cern.ch/SSLP2001

  19. E-nhance Lectures

    OpenAIRE

    Naber, Larissa; Köhle, Monika

    2006-01-01

    Ever more lecturers find themselves forced to Web-enhance their courses out of economic pressure or prestige. Universities trapped between rising student numbers and decreasing budgets are turning to e-learning as the one-stop solution, with little concern for student or teacher needs. An e-(nhanced) learning environment can only be successful if it fulfils students' and lecturers' needs alike. The student needs to be supported in various stages of learning, whereas the lecturer cannot afford...

  20. A Geminoid as Lecturer

    DEFF Research Database (Denmark)

    Abildgaard, Julie Rafn; Schärfe, Henrik

    2012-01-01

    In this paper we report our findings from an experiment with the teleoperated android Geminoid-DK. The geminoid took up the role of a university lecturer and delivered a 45 minute lecture in front of 150 freshmen students at Aalborg University. While considering the role of the geminoid in this e......In this paper we report our findings from an experiment with the teleoperated android Geminoid-DK. The geminoid took up the role of a university lecturer and delivered a 45 minute lecture in front of 150 freshmen students at Aalborg University. While considering the role of the geminoid...

  1. Effective lecture presentation skills.

    Science.gov (United States)

    Gelula, M H

    1997-02-01

    Lectures are the most popular form of teaching in medical education. As much as preparation and organization are key to the lecture's success, the actual presentation also depends upon the presenter's ability to reach the audience. Teaching is a lively activity. It calls for more than just offering ideas and data to an audience. It calls for direct contact with the audience, effective use of language, capability to use limited time effectively, and the ability to be entertaining. This article offers a structure to effective lecturing by highlighting the importance of voice clarity and speaking speed, approaches to using audiovisual aids, effectively using the audience to the lecture, and ways to be entertaining.

  2. Introducing CAFein, a New Computational Tool for Stellar Pulsations and Dynamic Tides

    CERN Document Server

    Valsecchi, Francesca; Willems, Bart; Kalogera, Vassiliki

    2013-01-01

    Here we present CAFein, a new computational tool for investigating radiative dissipation of dynamic tides in close binaries and of non-adiabatic, non-radial stellar oscillations in isolated stars in the linear regime. For the latter, CAFein computes the non-adiabatic eigenfrequencies and eigenfunctions of detailed stellar models. The code is based on the so-called Riccati method, a numerical algorithm that has been successfully applied to a variety of stellar pulsators, and which doesn't suffer of the major drawbacks of commonly used shooting and relaxation schemes. Here we present an extension of the Riccati method to investigate dynamic tides in close binaries. We demonstrate CAFein's capabilities as a stellar pulsation code both in the adiabatic and non-adiabatic regime, by reproducing previously published eigenfrequencies of a polytrope, and by successfully identifying the unstable modes of a stellar model in the beta Cephei/SPB region of the Hertzsprung-Russell diagram. Finally, we verify CAFein's behavi...

  3. Non-Radiative Step Facets in Semiconductor Nanowires.

    Science.gov (United States)

    Sanchez, Ana M; Zhang, Yunyan; Tait, Edward W; Hine, Nicholas D M; Liu, Huiyun; Beanland, Richard

    2017-03-24

    One of the main advantages of nanowires for functional applications is their high perfection, which results from surface image forces that act on line defects such as dislocations, rendering them unstable and driving them out of the crystal. Here we show that there is a class of linear defects that are stable in nanowires, with no long-range strain field or dislocation character. In zinc-blende semiconductors, they take the form of Ʃ3 (112) facets with heights constrained to be a multiple of three {111} monolayers. Density functional theory calculations show that they act as non-radiative recombination centres and have deleterious effects on nanowire properties. We present experimental observations of these defects on twin boundaries and twins that terminate inside GaAsP nanowires and find that they are indeed always multiples of three monolayers in height. Strategies to use the three-monolayer rule during growth to prevent their formation are discussed.

  4. General Relativistic Non-radial Oscillations of Compact Stars

    Science.gov (United States)

    Hall, Zack, II; Jaikumar, Prashanth

    2017-01-01

    Currently, we lack a means of identifying the type of matter at the core of compact stars, but in the future, we may be able to use gravitational wave signals produced by fluid oscillations inside compact stars to discover new phases of dense matter. To this end, we study the fluid perturbations inside compact stars such as Neutron Stars and Strange Quark Stars, focusing on modes that couple to gravitational waves. Using a modern equation of state for quark matter that incorporates interactions at moderately high densities, we implement an efficient computational scheme to solve the oscillation equations in the framework of General Relativity, and determine the complex eigenfrequencies that describe the oscillation and damping of the non-radial fluid modes. We discuss the significance of our results for future detection of these modes through gravitational waves. This work is supported in part by the CSULB Graduate Research Fellowship and by the National Science Foundation NSF PHY-1608959.

  5. Academic Training Lecture - Regular lecture programme

    CERN Multimedia

    PH Department

    2011-01-01

    Wednesday 28, Thursday 29 and Friday 30 September 2011 Supersymmetric Recipes by Prof. Ben Allanech / University of Cambridge, UK  from 11:00 to 12:00 (Europe/Zurich) at CERN ( Main Auditorium, Bldg. 500 ) In these lectures, I shall describe the theory of supersymmetry accessible to people with a knowledge of basic quantum field theory. The lectures will contain recipes of how to calculate which interactions (and which special relations) are in supersymmetry, without providing detailed proofs of where they come from. We shall also cover: motivation for weak-scale supersymmetry and the minimal supersymmetric standard model.

  6. Objective detection of retinal vessel pulsation.

    Directory of Open Access Journals (Sweden)

    William H Morgan

    Full Text Available PURPOSE: Retinal venous pulsation detection is a subjective sign, which varies in elevated intracranial pressure, venous obstruction and glaucoma. To date no method can objectively measure and identify pulsating regions. METHOD: Using high resolution video-recordings of the optic disk and retina we measured fluctuating light absorption by haemoglobin during pulsation. Pulsation amplitude was calculated from all regions of the retinal image video-frames in a raster pattern. Segmented retinal images were formed by objectively selecting regions with amplitudes above a range of threshold values. These were compared to two observers manually drawing an outline of the pulsating areas while viewing video-clips in order to generate receiver operator characteristics. RESULTS: 216,515 image segments were analysed from 26 eyes in 18 research participants. Using data from each eye, the median area under the receiver operator curve (AU-ROC was 0.95. With all data analysed together the AU-ROC was 0.89. We defined the ideal threshold amplitude for detection of any pulsating segment being that with maximal sensitivity and specificity. This was 5 units (95% confidence interval 4.3 to 6.0 compared to 12 units before any regions were missed. A multivariate model demonstrated that ideal threshold amplitude increased with increased variation in video-sequence illumination (p = 0.0119, but between the two observers (p = 0.0919 or other variables. CONCLUSION: This technique demonstrates accurate identification of retinal vessel pulsating regions with no areas identified manually being missed with the objective technique. The amplitude values are derived objectively and may be a significant advance upon subjective ophthalmodynamometric threshold techniques.

  7. Lectures on Law Enforcement.

    Science.gov (United States)

    Nettleship, Lois

    Three lectures on law enforcement are presented that were prepared for study purposes at Johnson County Community College. The first lecture examines the fundamental ideas of the Age of Enlightenment and discusses their influence on the American Revolution, the United States Constitution, and the Bill of Rights. Major provisions of the Bill of…

  8. Lectures on combustion theory

    Energy Technology Data Exchange (ETDEWEB)

    Burstein, S.Z.; Lax, P.D.; Sod, G.A. (eds.)

    1978-09-01

    Eleven lectures are presented on mathematical aspects of combustion: fluid dynamics, deflagrations and detonations, chemical kinetics, gas flows, combustion instability, flame spread above solids, spark ignition engines, burning rate of coal particles and hydrocarbon oxidation. Separate abstracts were prepared for three of the lectures. (DLC)

  9. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel 73127

    2001-01-01

    28, 29, 30, 31 May and 1 June REGULAR LECTURE PROGRAMME From 11:00 hrs - Main Auditorium bldg. 500 Quantum computing and Quantum cryptography T. Hey / University of Southampton, GB, and D. Ross / CERN-TH This course will give both an overview and a detailed introduction to quantum computing and quantum cryptography. The first lecture will survey the field, starting from its origins in Feyman's lecture in 1981. The next three lectures will explain in detail the relevance of Bell states and the workings of Grover's Quantum Search and Shor's quantum factorization algorithms. In addition, an explanation of quantum teleportation will be given. The last lecture will survey the recent progress towards realizing working quantum computers and quantum cryptographic systems.

  10. White Dwarf Pulsational Constraints on Stellar Evolution

    Science.gov (United States)

    Dunlap, Bart H.; Clemens, J. Christopher; O'Brien, Patrick C.; Hermes, J. J.; Fuchs, Joshua T.

    2017-01-01

    The complex processes that convert a protostellar cloud into a carbon/oxygen-core white dwarf star are distilled and modeled in state of the art stellar evolution codes. Many of these processes are well-constrained, but several are uncertain or must be parameterized in the models because a complete treatment would be computationally prohibitive—turbulent motions such as convective overshoot cannot, for example, be modeled in 1D. Various free parameters in the models must therefore be calibrated. We will discuss how white dwarf pulsations can inform such calibrations. The results of all prior evolution are cemented into the interiors of white dwarf stars and, so, hidden from view. However, during certain phases of their cooling, pulsations translate the star's evolutionary history into observable surface phenomena. Because the periods of a pulsating white dwarf star depend on an internal structure assembled as it evolved to its final state, white dwarf pulsation periods can be viewed as observable endpoints of stellar evolution. For example, the thickness of the helium layer in a white dwarf directly affects its pulsations; the observed periods are, therefore, a function of the number of thermal pulses during which the star converts helium into core material on the asymptotic giant branch. Because they are also a function of several other significant evolutionary processes, several pulsation modes are necessary to tease all of these apart. Unfortunately, white dwarf pulsators typically do not display enough oscillation modes to constrain stellar evolution. To avoid this limitation, we consider the pulsations of the entire collection of hot pulsating hydrogen-atmosphere white dwarf stars (DAVs). Though any one star may not have sufficient information to place interesting constraints on its evolutionary history, taken together, the stars show a pattern of modes that allows us to test evolutionary models. For an example set of published evolutionary models, we show a

  11. Modeling non-radial oscillations on components of close binaries

    Science.gov (United States)

    Latković, Olivera; Cséki, Attila

    2014-02-01

    We developed an advanced binary system model that includes stellar oscillations on one or both stars, with the goal of mode identification by fitting of the photometric light curves. The oscillations are modeled as perturbations of the local surface temperature and the local gravitational potential. In the case of tidally distorted stars, it is assumed that the pulsation axis coincides with the direction connecting the centers of the components rather than with the rotation axis. The mode identification method, originally devised by B. Bíró, is similar to eclipse mapping in that it utilizes the amplitude, phase and frequency modulation of oscillations during the eclipse; but the identification is achieved by grid-fitting of the observed light curve rather than by image reconstruction. The proposed model and the mode identification method have so far been tested on synthetic data with encouraging results.

  12. Connections between whistlers and pulsation activity

    Directory of Open Access Journals (Sweden)

    J. Verö

    Full Text Available Simultaneous whistler records of one station and geomagnetic pulsation (Pc3 records at three stations were compared. In a previous study correlation was found between occurrence and L value of propagation/excitation for the two phenomena. The recently investigated simultaneous records have shown that the correlation is better on longer time scales (days than on shorter ones (minutes, but the L values of the propagation of whistlers/excitation of pulsations are correlated, i.e. if whistlers propagate in higher latitude ducts, pulsations have periods longer than in the case when whistlers propagate in lower latitude ducts.

    Key words: Electromagnetics (wave propagation - Magnetospheric physics (magnetospheric configuration and dynamics; MHD waves and instabilities

  13. Pulsating star research and the Gaia revolution

    Directory of Open Access Journals (Sweden)

    Eyer Laurent

    2017-01-01

    Full Text Available In this article we present an overview of the ESA Gaia mission and of the unprecedented impact that Gaia will have on the field of variable star research. We summarise the contents and impact of the first Gaia data release on the description of variability phenomena, with particular emphasis on pulsating star research. The Tycho-Gaia astrometric solution, although limited to 2.1 million stars, has been used in many studies related to pulsating stars. Furthermore a set of 3,194 Cepheids and RR Lyrae stars with their times series have been released. Finally we present the plans for the ongoing study of variable phenomena with Gaia and highlight some of the possible impacts of the second data release on variable, and specifically, pulsating stars.

  14. Pulsating star research and the Gaia revolution

    Science.gov (United States)

    Eyer, Laurent; Clementini, Gisella; Guy, Leanne P.; Rimoldini, Lorenzo; Glass, Florian; Audard, Marc; Holl, Berry; Charnas, Jonathan; Cuypers, Jan; Ridder, Joris De; Evans, Dafydd W.; de Fombelle, Gregory Jevardat; Lanzafame, Alessandro; Lecoeur-Taibi, Isabelle; Mowlavi, Nami; Nienartowicz, Krzysztof; Riello, Marco; Ripepi, Vincenzo; Sarro, Luis; Süveges, Maria

    2017-09-01

    In this article we present an overview of the ESA Gaia mission and of the unprecedented impact that Gaia will have on the field of variable star research. We summarise the contents and impact of the first Gaia data release on the description of variability phenomena, with particular emphasis on pulsating star research. The Tycho-Gaia astrometric solution, although limited to 2.1 million stars, has been used in many studies related to pulsating stars. Furthermore a set of 3,194 Cepheids and RR Lyrae stars with their times series have been released. Finally we present the plans for the ongoing study of variable phenomena with Gaia and highlight some of the possible impacts of the second data release on variable, and specifically, pulsating stars.

  15. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    12, 13, 14, 15 & 16 March REGULAR LECTURE PROGRAMME From 11:00 hrs - Main Auditorium bldg. 500 Telecommunication for the future Rob Parker / CERN-IT Few fields have experienced such a high level of technical advance over the last few decades as that of telecommunications. This lecture series will track the evolution of telecommunications systems since their inception, and consider how technology is likely to advance over the next years. A personal view will also be given of the effect of these innovations on our work and leisure activities.The lecture series will be aimed at an audience with no specific technical knowledge of telecommunications.

  16. Benefit of pulsation in soft corals.

    Science.gov (United States)

    Kremien, Maya; Shavit, Uri; Mass, Tali; Genin, Amatzia

    2013-05-28

    Soft corals of the family Xeniidae exhibit a unique, rhythmic pulsation of their tentacles (Movie S1), first noted by Lamarck nearly 200 y ago. However, the adaptive benefit of this perpetual, energetically costly motion is poorly understood. Using in situ underwater particle image velocimetry, we found that the pulsation motions thrust water upward and enhance mixing across the coral-water boundary layer. The induced upward motion effectively prevents refiltration of water by neighboring polyps, while the intensification of mixing, together with the upward flow, greatly enhances the coral's photosynthesis. A series of controlled laboratory experiments with the common xeniid coral Heteroxenia fuscescens showed that the net photosynthesis rate during pulsation was up to an order of magnitude higher than during the coral's resting, nonpulsating state. This enhancement diminished when the concentration of oxygen in the ambient water was artificially raised, indicating that the enhancement of photosynthesis was due to a greater efflux of oxygen from the coral tissues. By lowering the internal oxygen concentration, pulsation alleviates the problem of reduced affinity of ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) to CO2 under conditions of high oxygen concentrations. The photosynthesis-respiration ratio of the pulsating H. fuscescens was markedly higher than the ratios reported for nonpulsating soft and stony corals. Although pulsation is commonly used for locomotion and filtration in marine mobile animals, its occurrence in sessile (bottom-attached) species is limited to members of the ancient phylum Cnidaria, where it is used to accelerate water and enhance physiological processes.

  17. Pulsating White Dwarfs in Globular Clusters

    Science.gov (United States)

    Kanaan, A.; Zabot, A.; Fraga, L.

    2012-09-01

    We present our current efforts to detect pulsating white dwarfs in globular clusters and analyze the future of this area when the Extremely Large Telescope (ELT), the Giant Magellan Telescope (GMT) and the Thirty-Meter Telescope (TMT) all become operational. Today we are able to detect pulsating white dwarfs in M 4, NGC 6397 and NGC 6752. When ELT comes on line we should be able to improve the quality of data for the nearby clusters and push the limit to at least 3 magnitudes further, up to NGC 6626, increasing the number of observable clusters from 3 to 20.

  18. Interactive lectures in engineering education

    NARCIS (Netherlands)

    van Dijk, L.A.; van den Berg, G.C.; van Keulen, H.

    2001-01-01

    This article discusses an alternative approach to lecturing: the interactive lecture. In the literature, interactive teaching is forwarded as a means to increase the effectiveness of lectures. Members of lecturing staff still seem, however, reluctant to incorporate interactive teaching in their clas

  19. Interactive lectures in engineering education

    NARCIS (Netherlands)

    van Dijk, L.A.; van den Berg, G.C.; van Keulen, H.

    2001-01-01

    This article discusses an alternative approach to lecturing: the interactive lecture. In the literature, interactive teaching is forwarded as a means to increase the effectiveness of lectures. Members of lecturing staff still seem, however, reluctant to incorporate interactive teaching in their

  20. Feynman Lectures on Computation

    CERN Document Server

    Feynman, Richard Phillips; Allen, Robin W

    1999-01-01

    "When, in 1984-86, Richard P. Feynman gave his famous course on computation at the California Institute of Technology, he asked Tony Hey to adapt his lecture notes into a book. Although led by Feynman,"

  1. A Geminoid as Lecturer

    DEFF Research Database (Denmark)

    Abildgaard, Julie Rafn; Schärfe, Henrik

    2012-01-01

    In this paper we report our findings from an experiment with the teleoperated android Geminoid-DK. The geminoid took up the role of a university lecturer and delivered a 45 minute lecture in front of 150 freshmen students at Aalborg University. While considering the role of the geminoid in this e...... in this educational context, we report results relating to large-room teaching, as well as gender differences in the perception of the robot....

  2. Evaluation of pump pulsation in respirable size-selective sampling: part I. Pulsation measurements.

    Science.gov (United States)

    Lee, Eun Gyung; Lee, Larry; Möhlmann, Carsten; Flemmer, Michael M; Kashon, Michael; Harper, Martin

    2014-01-01

    Pulsations generated by personal sampling pumps modulate the airflow through the sampling trains, thereby varying sampling efficiencies, and possibly invalidating collection or monitoring. The purpose of this study was to characterize pulsations generated by personal sampling pumps relative to a nominal flow rate at the inlet of different respirable cyclones. Experiments were conducted using a factorial combination of 13 widely used sampling pumps (11 medium and 2 high volumetric flow rate pumps having a diaphragm mechanism) and 7 cyclones [10-mm nylon also known as Dorr-Oliver (DO), Higgins-Dewell (HD), GS-1, GS-3, Aluminum, GK2.69, and FSP-10]. A hot-wire anemometer probe cemented to the inlet of each cyclone type was used to obtain pulsation readings. The three medium flow rate pump models showing the highest, a midrange, and the lowest pulsations and two high flow rate pump models for each cyclone type were tested with dust-loaded filters (0.05, 0.21, and 1.25mg) to determine the effects of filter loading on pulsations. The effects of different tubing materials and lengths on pulsations were also investigated. The fundamental frequency range was 22-110 Hz and the magnitude of pulsation as a proportion of the mean flow rate ranged from 4.4 to 73.1%. Most pump/cyclone combinations generated pulse magnitudes ≥10% (48 out of 59 combinations), while pulse shapes varied considerably. Pulsation magnitudes were not considerably different for the clean and dust-loaded filters for the DO, HD, and Aluminum cyclones, but no consistent pattern was observed for the other cyclone types. Tubing material had less effect on pulsations than tubing length; when the tubing length was 183cm, pronounced damping was observed for a pump with high pulsation (>60%) for all tested tubing materials except for the Tygon Inert tubing. The findings in this study prompted a further study to determine the possibility of shifts in cyclone sampling efficiency due to sampling pump pulsations

  3. X-ray Pulsation Searches with NICER

    Science.gov (United States)

    Ray, Paul S.; Arzoumanian, Zaven

    2016-04-01

    The Neutron Star Interior Composition Explorer (NICER) is an X-ray telescope with capabilities optimized for the study of the structure, dynamics, and energetics of neutron stars through high-precision timing of rotation- and accretion-powered pulsars in the 0.2-12 keV band. It has large collecting area (twice that of the XMM-Newton EPIC-pn camera), CCD-quality spectral resolution, and high-precision photon time tagging referenced to UTC through an onboard GPS receiver. NICER will begin its 18-month prime mission as an attached payload on the International Space Station around the end of 2016. I will describe the science planning for the pulsation search science working group, which is charged with searching for pulsations and studying flux modulation properties of pulsars and other neutron stars. A primary goal of our observations is to detect pulsations from new millisecond pulsars that will contribute to NICER’s studies of the neutron star equation of state through pulse profile modeling. Beyond that, our working group will search for pulsations in a range of source categories, including LMXBs, new X-ray transients that might be accreting millisecond pulsars, X-ray counterparts to unassociated Fermi LAT sources, gamma-ray binaries, isolated neutron stars, and ultra-luminous X-ray sources. I will survey our science plans and give an overview of our planned observations during NICER’s prime mission.

  4. Picosecond nonradiative processes in neodymium-doped crystals and glasses: mechansim for the energy gap law

    Energy Technology Data Exchange (ETDEWEB)

    Bibeau, C.; Payne, S.A.

    1997-09-29

    We present measurements of the 4G7/2 emission lifetime for 26 Nd-doped materials. A model of nonradiative decay based on dipole-dipole energy transfer is developed and found to be supported by our data.

  5. A Pulsation Mechanism for GW Virginis Variables

    Science.gov (United States)

    Cox, Arthur N.

    2003-03-01

    The mechanism that produces pulsations in the hottest pre-white dwarfs has been uncertain since the early work indicated that helium is a poison that smooths opacity bumps in the opacity-temperature plane caused by the ionizations of the large observed amounts of carbon and oxygen. Very little helium seemed to be needed to prevent the kappa effect pulsation driving, but helium amounts of almost half of the mass in the surface composition are observed in the pulsating PG 1159-035 stars called the GW Virginis variables. Rather little change in the C and O surface abundances is observed from the hottest (RX J2117.1+3412 at 170,000 K) to the coolest (PG 0122+200 at 80,000 K) GW Vir variables. Actually the shortest observed periods (300-400 s) of these variables are generally predicted to be unstable in all models, but the longest observed periods (up to 1000 s) are difficult to excite. Three recent investigations differ in their conclusions, with two finding that helium and even a slight amount of hydrogen does not prevent the kappa effect of C and O ionizations. A more detailed study reported here confirms the poisoning effect of helium. However, the ionization K- and L-edge opacity of the original iron, whose global abundance is unaffected by all previous evolution, especially if enhanced by radiation absorption levitation, can give different, previously unexplored, opacity driving that can explain the observed pulsations. But even this iron ionization driving can be somewhat poisoned by bump smoothing if the C and O abundances are large. Nonvariable GW Vir stars in the observed instability strip could be the result of small composition variations in the pulsation driving layers.

  6. Model of two-stream non-radial accretion for binary X-ray pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Lipunov, V.M. (Sternberg Astronomical Inst., Moscow (USSR))

    1982-03-01

    The general case of non-radial accretion is assumed to occur in real binary systems containing X-ray pulsars. The structure and the stability of the magnetosphere, the interaction between the magnetosphere and accreted matter, as well as evolution of neutron star in close binary system are examined within the framework of the two-stream model of nonradial accretion onto a magnetized neutron star. Observable parameters of X-ray pulsars are explained in terms of the model considered.

  7. Digital filter technology and its application to geomagnetic pulsations in Antarctica

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Digital filter technology is an important method in study of geomagnetic pulsations in Antarctica. The signals received by pulsation magnetometer on the ground include various types of magnetic pulsations. Some types of pulsations or some frequency hands of pulsations can be extracted from the signals by means of digital filter technology because types of pulsations are defined according to their frequency range. In this paper usual digital filter technology is provided for study of magnetic pulsations in Antarctica and some examples are introduced.

  8. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    ACADEMIC TRAINING LECTURE 1, 2, 3, 4 and 5 October LECTURES FOR POSTGRADUATE STUDENTS From 10:00 hrs - Main Auditorium bldg. 500 1 Introduction to particle accelerators E.J.N. Wilson / CERN-AC , Head of the CERN Accelerator School This new series of lectures is intended for anyone with a technical or scientific background who would like to become familiar with the principles of accelerator design. It is a complement to last year's course and includes new lectures on present day accelerators, and their applications as well as colliders and neutrino factories. Beam dynamics, which was treated at length in last year's course, has been compressed into one lecture, intended as revision for those who followed earlier courses and an introduction for newcomers to the field. The course should not be missed by those who will attend the CAS Intermediate Accelerator School in Seville. 1-10 10:00 Present-day Accelerators 11:00 - Beam Dynamics 2-10 10:00 Accelerating Cavities 11:00 - Non-linear Dynamics 3-10 10:00 E...

  9. Academic Training Lecture - Regular Programme

    CERN Multimedia

    PH Department

    2011-01-01

    Regular Lecture Programme 9 May 2011 ACT Lectures on Detectors - Inner Tracking Detectors by Pippa Wells (CERN) 10 May 2011 ACT Lectures on Detectors - Calorimeters (2/5) by Philippe Bloch (CERN) 11 May 2011 ACT Lectures on Detectors - Muon systems (3/5) by Kerstin Hoepfner (RWTH Aachen) 12 May 2011 ACT Lectures on Detectors - Particle Identification and Forward Detectors by Peter Krizan (University of Ljubljana and J. Stefan Institute, Ljubljana, Slovenia) 13 May 2011 ACT Lectures on Detectors - Trigger and Data Acquisition (5/5) by Dr. Brian Petersen (CERN) from 11:00 to 12:00 at CERN ( Bldg. 222-R-001 - Filtration Plant )

  10. Lectures on functor homology

    CERN Document Server

    Touzé, Antoine

    2015-01-01

    This book features a series of lectures that explores three different fields in which functor homology (short for homological algebra in functor categories) has recently played a significant role. For each of these applications, the functor viewpoint provides both essential insights and new methods for tackling difficult mathematical problems. In the lectures by Aurélien Djament, polynomial functors appear as coefficients in the homology of infinite families of classical groups, e.g. general linear groups or symplectic groups, and their stabilization. Djament’s theorem states that this stable homology can be computed using only the homology with trivial coefficients and the manageable functor homology. The series includes an intriguing development of Scorichenko’s unpublished results. The lectures by Wilberd van der Kallen lead to the solution of the general cohomological finite generation problem, extending Hilbert’s fourteenth problem and its solution to the context of cohomology. The focus here is o...

  11. Lectures on Chevalley groups

    CERN Document Server

    Steinberg, Robert

    2016-01-01

    Robert Steinberg's Lectures on Chevalley Groups were delivered and written during the author's sabbatical visit to Yale University in the 1967-1968 academic year. The work presents the status of the theory of Chevalley groups as it was in the mid-1960s. Much of this material was instrumental in many areas of mathematics, in particular in the theory of algebraic groups and in the subsequent classification of finite groups. This posthumous edition incorporates additions and corrections prepared by the author during his retirement, including a new introductory chapter. A bibliography and editorial notes have also been added. This is a great unsurpassed introduction to the subject of Chevalley groups that influenced generations of mathematicians. I would recommend it to anybody whose interests include group theory. -Efim Zelmanov, University of California, San Diego Robert Steinberg's lectures on Chevalley groups were given at Yale University in 1967. The notes for the lectures contain a wonderful exposition of ...

  12. Lectures for CERN pensioners

    CERN Multimedia

    GS Department

    2009-01-01

    The CERN Medical Service and the Pensioners Association are pleased to invite CERN pensioners to a series of lectures given by professors and specialists from the Teaching Hospitals and the Faculty of Medicine of the University of Geneva on the following topic: PROMOTION OF OPTIMUM BRAIN AGEING The lectures will take place in the Main CERN Auditorium (Building 60) from 2.30 p.m. to 4.30 p.m. on the following dates: Thursday 15 January 2009: Diagnosing and treating Alzheimer’s disease Pr Gabriel GOLD Wednesday 25 February 2009: What is the brain reserve? Speaker’s name to be announced at a later date. The lectures will be given in French, with transparencies in English, and will be followed by a wide-ranging debate with the participants. CERN Medical Service - Pensioners Association - CERN-ESO (GAC-EPA)

  13. Albert Einstein memorial lectures

    CERN Document Server

    Mechoulam, Raphael; The Israel Academy for Sciences and Humanities

    2012-01-01

    This volume consists of a selection of the Albert Einstein Memorial Lectures presented annually at the Israel Academy of Sciences and Humanities. Delivered by eminent scientists and scholars, including Nobel laureates, they cover a broad spectrum of subjects in physics, chemistry, life science, mathematics, historiography and social issues. This distinguished memorial lecture series was inaugurated by the Israel Academy of Sciences and Humanities following an international symposium held in Jerusalem in March 1979 to commemorate the centenary of Albert Einstein's birth. Considering that Einstein's interests, activities and influence were not restricted to theoretical physics but spanned broad fields affecting society and the welfare of humankind, it was felt that these memorial lectures should be addressed to scientists, scholars and erudite laypersons rather than to physicists alone.

  14. Memory for Lectures: How Lecture Format Impacts the Learning Experience.

    Directory of Open Access Journals (Sweden)

    Trish L Varao-Sousa

    Full Text Available The present study investigated what impact the presentation style of a classroom lecture has on memory, mind wandering, and the subjective factors of interest and motivation. We examined if having a professor lecturing live versus on video alters the learning experience of the students in the classroom. During the lectures, students were asked to report mind wandering and later complete a memory test. The lecture format was manipulated such that all the students received two lectures, one live and one a pre-recorded video. Results indicate that lecture format affected memory performance but not mind wandering, with enhanced memory in the live lectures. Additionally, students reported greater interest and motivation in the live lectures. Given that a single change to the classroom environment, professor presence, impacted memory performance, as well as motivation and interest, the present results have several key implications for technology-based integrations into higher education classrooms.

  15. Memory for Lectures: How Lecture Format Impacts the Learning Experience.

    Science.gov (United States)

    Varao-Sousa, Trish L; Kingstone, Alan

    2015-01-01

    The present study investigated what impact the presentation style of a classroom lecture has on memory, mind wandering, and the subjective factors of interest and motivation. We examined if having a professor lecturing live versus on video alters the learning experience of the students in the classroom. During the lectures, students were asked to report mind wandering and later complete a memory test. The lecture format was manipulated such that all the students received two lectures, one live and one a pre-recorded video. Results indicate that lecture format affected memory performance but not mind wandering, with enhanced memory in the live lectures. Additionally, students reported greater interest and motivation in the live lectures. Given that a single change to the classroom environment, professor presence, impacted memory performance, as well as motivation and interest, the present results have several key implications for technology-based integrations into higher education classrooms.

  16. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    26, 27, 28 February and 1, 2 March REGULAR LECTURE PROGRAMME From 11:00 hrs - Main Auditorium bldg. 500 Recent Results on CP Violation and B Physics P.F. HARRISON / QMW, London, UK With the advent of the asymmetric B factories in Japan and the US, exciting new results on CP Violation and B Physics are starting to be achieved. In these lectures, we review the existing experimental and phenomenological context of these measurements, we compare and contrast the new experimental facilities and discuss the implications of the recent results on our understanding. Finally we summarise the prospects for future developments.

  17. Lectures in general algebra

    CERN Document Server

    Kurosh, A G; Stark, M; Ulam, S

    1965-01-01

    Lectures in General Algebra is a translation from the Russian and is based on lectures on specialized courses in general algebra at Moscow University. The book starts with the basics of algebra. The text briefly describes the theory of sets, binary relations, equivalence relations, partial ordering, minimum condition, and theorems equivalent to the axiom of choice. The text gives the definition of binary algebraic operation and the concepts of groups, groupoids, and semigroups. The book examines the parallelism between the theory of groups and the theory of rings; such examinations show the

  18. Twenty lectures on thermodynamics

    CERN Document Server

    Buchdahl, H A

    2013-01-01

    Twenty Lectures on Thermodynamics is a course of lectures, parts of which the author has given various times over the last few years. The book gives the readers a bird's eye view of phenomenological and statistical thermodynamics. The book covers many areas in thermodynamics such as states and transition; adiabatic isolation; irreversibility; the first, second, third and Zeroth laws of thermodynamics; entropy and entropy law; the idea of the application of thermodynamics; pseudo-states; the quantum-static al canonical and grand canonical ensembles; and semi-classical gaseous systems. The text

  19. Lectures on quantum mechanics

    CERN Document Server

    Dirac, Paul A M

    2001-01-01

    The author of this concise, brilliant series of lectures on mathematical methods in quantum mechanics was one of the shining intellects in the field, winning a Nobel prize in 1933 for his pioneering work in the quantum mechanics of the atom. Beyond that, he developed the transformation theory of quantum mechanics (which made it possible to calculate the statistical distribution of certain variables), was one of the major authors of the quantum theory of radiation, codiscovered the Fermi-Dirac statistics, and predicted the existence of the positron.The four lectures in this book were delivered

  20. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    26, 27, 28 February and 1, 2 March REGULAR LECTURE PROGRAMME From 11:00 hrs - Main Auditorium bldg. 500 Recent Results on CP Violation and B Physics P.F. HARRISON / QMW, London, UK With the advent of the asymmetric B factories in Japan and the US, exciting new results on CP Violation and B Physics are starting to be achieved. In these lectures, we review the existing experimental and phenomenological context of these measurements, we compare and contrast the new experimental facilities and discuss the implications of the recent results on our understanding. Finally we summarise the prospects for future developments.

  1. Lectures on Constrained Systems

    CERN Document Server

    Date, Ghanashyam

    2010-01-01

    These lecture notes were prepared as a basic introduction to the theory of constrained systems which is how the fundamental forces of nature appear in their Hamiltonian formulation. Only a working knowledge of Lagrangian and Hamiltonian formulation of mechanics is assumed. These notes are based on the set of eight lectures given at the {\\em Refresher Course for College Teachers} held at IMSc during May-June, 2005. These are submitted to the arxiv for an easy access to a wider body of students.

  2. Introducing CAFein, a New Computational Tool for Stellar Pulsations and Dynamic Tides

    Science.gov (United States)

    Valsecchi, F.; Farr, W. M.; Willems, B.; Rasio, F. A.; Kalogera, V.

    2013-08-01

    Here we present CAFein, a new computational tool for investigating radiative dissipation of dynamic tides in close binaries and of non-adiabatic, non-radial stellar oscillations in isolated stars in the linear regime. For the latter, CAFein computes the non-adiabatic eigenfrequencies and eigenfunctions of detailed stellar models. The code is based on the so-called Riccati method, a numerical algorithm that has been successfully applied to a variety of stellar pulsators, and which does not suffer from the major drawbacks of commonly used shooting and relaxation schemes. Here we present an extension of the Riccati method to investigate dynamic tides in close binaries. We demonstrate CAFein's capabilities as a stellar pulsation code both in the adiabatic and non-adiabatic regimes, by reproducing previously published eigenfrequencies of a polytrope, and by successfully identifying the unstable modes of a stellar model in the β Cephei/SPB region of the Hertzsprung-Russell diagram. Finally, we verify CAFein's behavior in the dynamic tides regime by investigating the effects of dynamic tides on the eigenfunctions and orbital and spin evolution of massive main sequence stars in eccentric binaries, and of hot Jupiter host stars. The plethora of asteroseismic data provided by NASA's Kepler satellite, some of which include the direct detection of tidally excited stellar oscillations, make CAFein quite timely. Furthermore, the increasing number of observed short-period detached double white dwarfs (WDs) and the observed orbital decay in the tightest of such binaries open up a new possibility of investigating WD interiors through the effects of tides on their orbital evolution.

  3. INTRODUCING CAFein, A NEW COMPUTATIONAL TOOL FOR STELLAR PULSATIONS AND DYNAMIC TIDES

    Energy Technology Data Exchange (ETDEWEB)

    Valsecchi, F.; Farr, W. M.; Willems, B.; Rasio, F. A.; Kalogera, V., E-mail: francesca@u.northwestern.edu [Department of Physics and Astronomy and Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)

    2013-08-10

    Here we present CAFein, a new computational tool for investigating radiative dissipation of dynamic tides in close binaries and of non-adiabatic, non-radial stellar oscillations in isolated stars in the linear regime. For the latter, CAFein computes the non-adiabatic eigenfrequencies and eigenfunctions of detailed stellar models. The code is based on the so-called Riccati method, a numerical algorithm that has been successfully applied to a variety of stellar pulsators, and which does not suffer from the major drawbacks of commonly used shooting and relaxation schemes. Here we present an extension of the Riccati method to investigate dynamic tides in close binaries. We demonstrate CAFein's capabilities as a stellar pulsation code both in the adiabatic and non-adiabatic regimes, by reproducing previously published eigenfrequencies of a polytrope, and by successfully identifying the unstable modes of a stellar model in the {beta} Cephei/SPB region of the Hertzsprung-Russell diagram. Finally, we verify CAFein's behavior in the dynamic tides regime by investigating the effects of dynamic tides on the eigenfunctions and orbital and spin evolution of massive main sequence stars in eccentric binaries, and of hot Jupiter host stars. The plethora of asteroseismic data provided by NASA's Kepler satellite, some of which include the direct detection of tidally excited stellar oscillations, make CAFein quite timely. Furthermore, the increasing number of observed short-period detached double white dwarfs (WDs) and the observed orbital decay in the tightest of such binaries open up a new possibility of investigating WD interiors through the effects of tides on their orbital evolution.

  4. Stellar Pulsations in Beyond Horndeski Gravity Theories

    CERN Document Server

    Sakstein, Jeremy; Koyama, Kazuya

    2016-01-01

    Theories of gravity in the beyond Horndeski class recover the predictions of general relativity in the solar system whilst admitting novel cosmologies, including late-time de Sitter solutions in the absence of a cosmological constant. Deviations from Newton's law are predicted inside astrophysical bodies, which allow for falsifiable, smoking-gun tests of the theory. In this work we study the pulsations of stars by deriving and solving the wave equation governing linear adiabatic oscillations to find the modified period of pulsation. Using both semi-analytic and numerical models, we perform a preliminary survey of the stellar zoo in an attempt to identify the best candidate objects for testing the theory. Brown dwarfs and Cepheid stars are found to be particularly sensitive objects and we discuss the possibility of using both to test the theory.

  5. Flow induced pulsations in pipe systems

    Science.gov (United States)

    Bruggeman, Jan Cornelis

    1987-12-01

    The aeroacoustic behavior of a low Mach number, high Reynolds number flow through a pipe with closed side branches was investigated. Sound is generated by coherent structures of concentrated vorticity formed periodically in the separated flow in the T-shaped junctions of side branches and the main pipe. The case of moderate pulsation amplitudes was investigated. It appears that the vortical flow in a T-joint is an aeroacoustic source of constant strength when acoustic energy losses due to radiation and friction are small but not negligible. When acoustic energy losses due to radiation and friction are negligible, the nonlinear character of vortex damping is the amplitude limiting mechanism. It is stressed that aeroacoustic sources should not be neglected in studies of the response of a piping lay-out with flow to, e.g., the pulsating output of a compressor.

  6. Stellar pulsations in beyond Horndeski gravity theories

    Science.gov (United States)

    Sakstein, Jeremy; Kenna-Allison, Michael; Koyama, Kazuya

    2017-03-01

    Theories of gravity in the beyond Horndeski class recover the predictions of general relativity in the solar system whilst admitting novel cosmologies, including late-time de Sitter solutions in the absence of a cosmological constant. Deviations from Newton's law are predicted inside astrophysical bodies, which allow for falsifiable, smoking-gun tests of the theory. In this work we study the pulsations of stars by deriving and solving the wave equation governing linear adiabatic oscillations to find the modified period of pulsation. Using both semi-analytic and numerical models, we perform a preliminary survey of the stellar zoo in an attempt to identify the best candidate objects for testing the theory. Brown dwarfs and Cepheid stars are found to be particularly sensitive objects and we discuss the possibility of using both to test the theory.

  7. Pulsating White Dwarf Stars and Precision Asteroseismology

    CERN Document Server

    Winget, D E

    2008-01-01

    Galactic history is written in the white dwarf stars. Their surface properties hint at interiors composed of matter under extreme conditions. In the forty years since their discovery, pulsating white dwarf stars have moved from side-show curiosities to center stage as important tools for unraveling the deep mysteries of the Universe. Innovative observational techniques and theoretical modeling tools have breathed life into precision asteroseismology. We are just learning to use this powerful tool, confronting theoretical models with observed frequencies and their time rate-of-change. With this tool, we calibrate white dwarf cosmochronology; we explore equations of state; we measure stellar masses, rotation rates, and nuclear reaction rates; we explore the physics of interior crystallization; we study the structure of the progenitors of Type Ia supernovae, and we test models of dark matter. The white dwarf pulsations are at once the heartbeat of galactic history and a window into unexplored and exotic physics.

  8. Pulsating White Dwarf Stars and Precision Asteroseismology

    Science.gov (United States)

    Winget, D. E.; Kepler, S. O.

    2008-09-01

    Galactic history is written in the white dwarf stars. Their surface properties hint at interiors composed of matter under extreme conditions. In the forty years since their discovery, pulsating white dwarf stars have moved from side-show curiosities to center stage as important tools for unraveling the deep mysteries of the Universe. Innovative observational techniques and theoretical modeling tools have breathed life into precision asteroseismology. We are just learning to use this powerful tool, confronting theoretical models with observed frequencies and their time rate-of-change. With this tool, we calibrate white dwarf cosmochronology; we explore equations of state; we measure stellar masses, rotation rates, and nuclear reaction rates; we explore the physics of interior crystallization; we study the structure of the progenitors of Type Ia supernovae, and we test models of dark matter. The white dwarf pulsations are at once the heartbeat of galactic history and a window into unexplored and exotic physics.

  9. The Harvey lectures, Series 82

    Energy Technology Data Exchange (ETDEWEB)

    Botstein, D.; Cech, T.R.; Hille, B.; Lodish, H.F.; Majerus, P.W.

    1988-01-01

    The Harvey Lecture Series is published annually and provides reviews of research topics in the biomedical sciences. Eight lectures by investigators are included in the volume representing the most recent work in the major laboratories.

  10. Pulsating Radio Sources near the Crab Nebula.

    Science.gov (United States)

    Staelin, D H; Reifenstein, E C

    1968-12-27

    Two new pulsating radio sources, designated NP 0527 and NP 0532, were found near the Crab Nebula and could be coincident with it. Both sources are sporadic, and no periodicities are evident. The pulse dispersions indicate that 1.58 +/- 0.03 and 1.74 +/- 0.02 x 10(20) electrons per square centimeter lie in the direction of NP 0527 and NP 0532, respectively.

  11. The MACHO Project Sample of Galactic Bulge High-Amplitude Scuti Stars: Pulsation Behavior and Stellar Properties

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, D.P.; Cook, K.H.; Freeman, K.C.; Geha, M.; Griest, K.; Lehner, M.J.; Marshall, S.L.; McNamara, B.J.; Minniti, D.; Nelson, C.; Peterson, B.A.; Popowski, P.; Pratt, M.R.; Quinn, P.J.; Rodgers, A.W.; Sutherland, W.; Templeton, M.R.; Vandehei, T.; Welch, D.L.

    1999-11-16

    We have detected 90 objects with periods and lightcurve structure similar to those of field {delta} Scuti stars, using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude {delta} Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground {delta} Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population {delta} Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field {delta} Scuti stars and the {delta} Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude {delta} Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles d{sup -1}) and the observed period ratios of {approx}0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes.

  12. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    1, 2, 3, 4 and 5 October LECTURES FOR POSTGRADUATE STUDENTS From 10:00 hrs - Main Auditorium bldg. 500 1 Introduction to particle accelerators E.J.N. Wilson / CERN-AC , Head of the CERN Accelerator School This new series of lectures is intended for anyone with a technical or scientific background who would like to become familiar with the principles of accelerator design. It is a complement to last year's course and includes new lectures on present day accelerators, and their applications as well as colliders and neutrino factories. Beam dynamics, which was treated at length in last year's course, has been compressed into one lecture, intended as revision for those who followed earlier courses and an introduction for newcomers to the field. The course should not be missed by those who will attend the CAS Intermediate Accelerator School in Seville. 1-10 10:00 Present-day Accelerators 11:00 - Beam Dynamics 2-10 10:00 Accelerating Cavities 11:00 - Non-linear Dynamics 3-10 10:00 Electron Dynamics 11:00 - ...

  13. Podcasting a Physics Lecture

    Science.gov (United States)

    McDonald, James E. R.

    2008-01-01

    The technology of podcasting, or creating audio or video files that can be subscribed to over the Internet, has grown in popularity over the past few years. Many educators have already begun realizing the potential of delivering such customized content, but most efforts have focused on lecture-style humanities courses or multimedia arts courses.…

  14. When Lecturing: Teach!

    Science.gov (United States)

    Aiken, Warren R.

    1980-01-01

    Techniques that can be used to make the lecture method of teaching more effective include using pictures or objects to facilitate memory, using guided fantasies to stimulate students' imagination of processes, and the suggestopedia method for memorizing facts, principles, and vocabulary. (MSE)

  15. Participatory Lecture Demonstrations.

    Science.gov (United States)

    Battino, Rubin

    1979-01-01

    The use of participatory lecture demonstrations in the classroom is described. Examples are given for the following topics: chromatography, chemical kinetics, balancing equations, the gas laws, kinetic molecular theory, Henry's law of gas solubility, electronic energy levels in atoms, and translational, vibrational, and rotational energies of…

  16. Summer Student Lecture Programme

    CERN Multimedia

    2004-01-01

    Main Auditorium, bldg. 500 DATE TIME LECTURER TITLE Monday 2 August 09:15 - 10:00 P. Wells (CERN) The Higgs Saga at LEP 10:15 - 11:00 G. Cowan (Univ. of London) Introduction to Statistics (2/3) 11:15 - 12:00 G. Cowan (Univ. of London) Introduction to Statistics (3/3) DATE TIME LECTURER TITLE Tuesday 3 August 09:15 - 10:00 P. Sphicas (CERN) Trigger and Data Acquisition Systems (1/2) 10:15 - 11:00 R. Jacobsen (LBLN) From Raw Data to Physics Results (1/2) 11:15 - 12:00 R. Jacobsen (LBLN) G. Cowan (University of London) Discussion Session DATE TIME LECTURER TITLE Wednesday 4 August 09:15 - 10:00 P. Sphicas (CERN) Trigger and Data Acquisition Systems (2/2) 10:15 - 11:00 R. Jacobsen (LBLN) From Raw Data to Physics Results (2/2) 11:15 - 12:00 N. Palanque-Delabrouille (CEA) Astroparticle Physics (1/3) DATE TIME LECTURER TITLE Thursday 5 August 09:15 - 10:00 N. Palanque-Delabrouille (CEA) Astroparticle Physics (2/3) 10:15 - 11:00 N. Palanque-Delabrouille (CEA) A...

  17. Optimising Lecture Time

    DEFF Research Database (Denmark)

    Holst-Christensen, Bo

    the students problems from the educator to the students. By using techniques that put more weight on student participation, cooperation and preparation, I have been able to cut significantly down on the time used for lecturing, allowing more time for student work and reflection. As an example by getting...

  18. When Lecturing: Teach!

    Science.gov (United States)

    Aiken, Warren R.

    1980-01-01

    Techniques that can be used to make the lecture method of teaching more effective include using pictures or objects to facilitate memory, using guided fantasies to stimulate students' imagination of processes, and the suggestopedia method for memorizing facts, principles, and vocabulary. (MSE)

  19. Computer Aided Lecturing.

    Science.gov (United States)

    Van Meter, Donald E.

    1994-01-01

    Surveyed students taking a natural resource conservation course to determine the effects of computer software that provides tools for creating and managing visual presentations to students. Results indicated that 94% of the respondents believed computer-aided lectures helped them and recommended their continued use; note taking was more effective,…

  20. Discovery of five new massive pulsating white dwarf stars

    Science.gov (United States)

    Castanheira, B. G.; Kepler, S. O.; Kleinman, S. J.; Nitta, A.; Fraga, L.

    2013-03-01

    Using the SOuthern Astrophysical Research telescope (SOAR) Optical Imager at the SOAR 4.1 m telescope, we report on the discovery of five new massive pulsating white dwarf stars. Our results represent an increase of about 20 per cent in the number of massive pulsators. We have detected both short and long periods, low and high amplitude pulsation modes, covering the whole range of the ZZ Ceti instability strip. In this paper, we present a first seismological study of the new massive pulsators based on the few frequencies detected. Our analysis indicates that these stars have masses higher than average, in agreement with the spectroscopic determinations. In addition, we study for the first time the ensemble properties of the pulsating white dwarf stars with masses above 0.8 M⊙. We found a bimodal distribution of the main pulsation period with the effective temperature for the massive DAVs, which indicates mode selection mechanisms.

  1. The Onset of Chaos in Pulsating Variable Stars

    CERN Document Server

    Turner, David G; Percy, J R; Abdel-Latif, Mohamed Abdel-Sabour

    2011-01-01

    Random changes in pulsation period occur in cool pulsating Mira variables, Type A, B, and C semiregular variables, RV Tauri variables, and in most classical Cepheids. The physical processes responsible for such fluctuations are uncertain, but presumably originate in temporal modifications of the envelope convection in such stars. Such fluctuations are seemingly random over a few pulsation cycles of the stars, but are dominated by the regularity of the primary pulsation over the long term. The magnitude of stochasticity in pulsating stars appears to be linked directly to their dimensions, although not in simple fashion. It is relatively larger in M supergiants, for example, than in short-period Cepheids, but is common enough that it can be detected in visual observations for many types of pulsating stars. Although chaos was discovered in such stars 80 years ago, detection of its general presence in the group has only been possible in recent studies.

  2. SuperWASP observations of pulsating Am stars

    CERN Document Server

    Smalley, B; Smith, A M S; Fossati, L; Anderson, D R; Barros, S C C; Butters, O W; Cameron, A Collier; Christian, D J; Enoch, B; Faedi, F; Haswell, C A; Hellier, C; Holmes, S; Horne, K; Kane, S R; Lister, T A; Maxted, P F L; Norton, A J; Parley, N; Pollacco, D; Simpson, E K; Skillen, I; Southworth, J; Street, R A; West, R G; Wheatley, P J; Wood, P L

    2011-01-01

    We have studied over 1600 Am stars at a photometric precision of 1 mmag with SuperWASP photometric data. Contrary to previous belief, we find that around 200 Am stars are pulsating delta Sct and gamma Dor stars, with low amplitudes that have been missed in previous, less extensive studies. While the amplitudes are generally low, the presence of pulsation in Am stars places a strong constraint on atmospheric convection, and may require the pulsation to be laminar. While some pulsating Am stars have been previously found to be delta Sct stars, the vast majority of Am stars known to pulsate are presented in this paper. They will form the basis of future statistical studies of pulsation in the presence of atomic diffusion.

  3. Usage Reporting on Recorded Lectures

    NARCIS (Netherlands)

    Gorissen, Pierre; Bruggen, Jan van; Jochems, Wim

    2012-01-01

    This study analyses the interactions of students with the recorded lectures. We report on an analysis of students' use of recorded lectures at two Universities in the Netherlands. The data logged by the lecture capture system (LCS) is used and combined with collected survey data. We describe the pro

  4. In Defence of the Lecture

    Science.gov (United States)

    Webster, R. Scott

    2015-01-01

    In response to the lecture format coming under "attack" and being replaced by online materials and smaller tutorials, this paper attempts to offer not only a defence but also to assert that the potential value of the lecture is difficult to replicate through other learning formats. Some of the criticisms against lectures will be…

  5. CoRoT\\,102699796, the first metal-poor Herbig Ae pulsator: a hybrid $\\delta$ Sct-$\\gamma$ Dor variable?

    CERN Document Server

    Ripepi, V; Di Criscienzo, M; Catanzaro, G; Palla, F; Marconi, M; Ventura, P; Neiner, C; Catala, C; Bernabei, S

    2011-01-01

    We present the analysis of the time series observations of CoRoT\\,102699796 obtained by the CoRoT satellite that show the presence of five independent oscillation frequencies in the range 3.6-5 c/d. Using spectra acquired with FLAMES@VLT, we derive the following stellar parameters: spectral type F1V, T$_{\\rm eff}$=7000$\\pm$200 K, log(g)=$3.8\\pm0.4$, [M/H]=$-1.1\\pm0.2$, $v$sin$i$=$50\\pm5$ km/s, L/L$_{\\odot}$=21$^{+21}_{-11}$. Thus, for the first time we report the existence of a metal poor, intermediate-mass PMS pulsating star. Ground-based and satellite data are used to derive the spectral energy distribution of CoRoT\\,102699796 extending from the optical to mid-infrared wavelengths. The SED shows a significant IR excess at wavelengths greater than $\\sim5 \\mu$. We conclude that CoRoT\\,102699796 is a young Herbig Ae (F1Ve) star with a transitional disk, likely associated to the HII region [FT96]213.1-2.2. The pulsation frequencies have been interpreted in the light of the non-radial pulsation theory, using the...

  6. A search for low-metallicity pulsating B stars

    Science.gov (United States)

    Engelbrecht, Chris; Kgoadi, Refilwe; Frescura, Fabio

    2017-09-01

    We report on some recent results from a long-term UBVI survey of various fields in the Large Magellanic Cloud (LMC), which is aimed at identifying and classifying pulsating B stars in the selected LMC fields. Difference Imaging Analysis shows a clear advantage over conventional PSF fitting. Tentative indications have been found of a varying incidence of pulsation amplitudes (and, by inference, of metal content of the pulsators) across the LMC bar.

  7. Intrinsic non-radiative voltage losses in fullerene-based organic solar cells

    Science.gov (United States)

    Benduhn, Johannes; Tvingstedt, Kristofer; Piersimoni, Fortunato; Ullbrich, Sascha; Fan, Yeli; Tropiano, Manuel; McGarry, Kathryn A.; Zeika, Olaf; Riede, Moritz K.; Douglas, Christopher J.; Barlow, Stephen; Marder, Seth R.; Neher, Dieter; Spoltore, Donato; Vandewal, Koen

    2017-06-01

    Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared with the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant non-radiative recombination. Here, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer-state energies. This observation is explained by considering non-radiative charge-transfer-state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single-junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to 1.45-1.65 eV, that is, 0.2-0.3 eV higher than for technologies with minimized non-radiative voltage losses.

  8. Activated barrier crossing dynamics in the non-radiative decay of NADH and NADPH

    Energy Technology Data Exchange (ETDEWEB)

    Blacker, Thomas S., E-mail: t.blacker@ucl.ac.uk [Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London WC1E 6BT (United Kingdom); Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Research Department of Cell and Developmental Biology, University College London, London WC1E 6BT (United Kingdom); Marsh, Richard J., E-mail: richard.marsh@ucl.ac.uk [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Duchen, Michael R., E-mail: m.duchen@ucl.ac.uk [Research Department of Cell and Developmental Biology, University College London, London WC1E 6BT (United Kingdom); Bain, Angus J., E-mail: a.bain@ucl.ac.uk [Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London WC1E 6BT (United Kingdom); Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)

    2013-08-30

    Highlights: ► NADH and NADPH have a high rate of non-radiative excited state decay. ► Conformational relaxation is shown to be a significant non-radiative pathway. ► The Kramers equation describes the barrier crossing dynamics of the relaxation. ► Conformational restriction upon enzyme binding will alter NAD(P)H lifetimes. - Abstract: In live tissue, alterations in metabolism induce changes in the fluorescence decay of the biological coenzyme NAD(P)H, the mechanism of which is not well understood. In this work, the fluorescence and anisotropy decay dynamics of NADH and NADPH were investigated as a function of viscosity in a range of water–glycerol solutions. The viscosity dependence of the non-radiative decay is well described by Kramers and Kramers–Hubbard models of activated barrier crossing over a wide viscosity range. Our combined lifetime and anisotropy analysis indicates common mechanisms of non-radiative relaxation in the two emitting states (conformations) of both molecules. The low frequencies associated with barrier crossing suggest that non-radiative decay is mediated by small scale motion (e.g. puckering) of the nicotinamide ring. Variations in the fluorescence lifetimes of NADH and NADPH when bound to different enzymes may therefore be attributed to differing levels of conformational restriction upon binding.

  9. On the pulsation and evolutionary properties of helium burning radially pulsating variables

    Science.gov (United States)

    Bono, G.; Pietrinferni, A.; Marconi, M.; Braga, V. F.; Fiorentino, G.; Stetson, P. B.; Buonanno, R.; Castellani, M.; Dall'Ora, M.; Fabrizio, M.; Ferraro, I.; Giuffrida, G.; Iannicola, G.; Marengo, M.; Magurno, D.; Martinez-Vazquez, C. E.; Matsunaga, N.; Monelli, M.; Neeley, J.; Rastello, S.; Salaris, M.; Short, L.; Stellingwerf, R. F.

    2016-05-01

    We discuss pulsation and evolutionary properties of low- (RR Lyrae, Type II Cepheids) and intermediate-mass (Anomalous Cepheids) radial variables. We focus our attention on the topology of the instability strip and the distribution of the quoted variables in the Hertzsprung-Russell diagram. We discuss their evolutionary status and the dependence on the metallicity. Moreover, we address the diagnostics (period derivative, difference in luminosity, stellar mass) that can provide solid constraints on their progenitors and on the role that binarity and environment have in shaping their current pulsation characteristics. Finally, we briefly outline their use as standard candles.

  10. Feynman Lectures on Gravitation

    Energy Technology Data Exchange (ETDEWEB)

    Borcherds, P

    2003-05-21

    In the early 1960s Feynman lectured to physics undergraduates and, with the assistance of his colleagues Leighton and Sands, produced the three-volume classic Feynman Lectures in Physics. These lectures were delivered in the mornings. In the afternoons Feynman was giving postgraduate lectures on gravitation. This book is based on notes compiled by two students on that course: Morinigo and Wagner. Their notes were checked and approved by Feynman and were available at Caltech. They have now been edited by Brian Hatfield and made more widely available. The book has a substantial preface by John Preskill and Kip Thorne, and an introduction entitled 'Quantum Gravity' by Brian Hatfield. You should read these before going on to the lectures themselves. Preskill and Thorne identify three categories of potential readers of this book. 1. Those with a postgraduate training in theoretical physics. 2. 'Readers with a solid undergraduate training in physics'. 3. 'Admirers of Feynman who do not have a strong physics background'. The title of the book is perhaps misleading: readers in category 2 who think that this book is an extension of the Feynman Lectures in Physics may be disappointed. It is not: it is a book aimed mainly at those in category 1. If you want to get to grips with gravitation (and general relativity) then you need to read an introductory text first e.g. General Relativity by I R Kenyon (Oxford: Oxford University Press) or A Unified Grand Tour of Theoretical Physics by Ian D Lawrie (Bristol: IoP). But there is no Royal Road. As pointed out in the preface and in the introduction, the book represents Feynman's thinking about gravitation some 40 years ago: the lecture course was part of his attempts to understand the subject himself, and for readers in all three categories it is this that makes the book one of interest: the opportunity to observe how a great physicist attempts to tackle some of the hardest challenges of physics

  11. Handouts: making the lecture portable.

    Science.gov (United States)

    Kroenke, K

    1991-01-01

    Previous medical literature on preparing lecture handouts has focused on their use in student education, where as part of a course there is a series of lectures followed by an examination. Conversely, resident and practising physicians usually attend single lectures on individual topics in order to update and improve their clinical skills. Handouts designed for the latter type of lecture can serve as a useful resource in subsequent day-to-day teaching and patient care. This article examines the purpose, distribution, structure, and substance of such handouts. Guidelines to assist the speaker in preparing lecture handouts are discussed.

  12. The IACOB project. IV. New predictions for high-degree non-radial mode instability domains in massive stars and their connection with macroturbulent broadening

    Science.gov (United States)

    Godart, M.; Simón-Díaz, S.; Herrero, A.; Dupret, M. A.; Grötsch-Noels, A.; Salmon, S. J. A. J.; Ventura, P.

    2017-01-01

    Context. Asteroseismology is a powerful tool to access the internal structure of stars. Apart from the important impact of theoretical developments, progress in this field has been commonly associated with the analysis of time-resolved observations. Recently, the so-called macroturbulent broadening has been proposed as a complementary and less expensive way - in terms of observational time - to investigate pulsations in massive stars. Aims: We assess to what extent this ubiquitous non-rotational broadening component which shapes the line profiles of O stars and B supergiants is a spectroscopic signature of pulsation modes driven by a heat mechanism. Methods: We compute stellar main-sequence and post-main-sequence models from 3 to 70 M⊙ with the ATON stellar evolution code, and determine the instability domains for heat-driven modes for degrees ℓ = 1-20 using the adiabatic and non-adiabatic codes LOSC and MAD. We use the observational material compiled in the framework of the IACOB project to investigate possible correlations between the single snapshot line-broadening properties of a sample of ≈260 O and B-type stars and their location inside or outside the various predicted instability domains. Results: We present an homogeneous prediction for the non-radial instability domains of massive stars for degree ℓ up to 20. We provide a global picture of what to expect from an observational point of view in terms of the frequency range of excited modes, and we investigate the behavior of the instabilities with respect to stellar evolution and the degree of the mode. Furthermore, our pulsational stability analysis, once compared to the empirical results, indicates that stellar oscillations originated by a heat mechanism cannot explain alone the occurrence of the large non-rotational line-broadening component commonly detected in the O star and B supergiant domain. Based on observations made with the Nordic Optical Telescope, operated by NOTSA, and the Mercator

  13. Observation of a nonradiative flat band for spoof surface plasmons in a metallic Lieb lattice

    CERN Document Server

    Kajiwara, Sho; Nakata, Yosuke; Nakanishi, Toshihiro; Kitano, Masao

    2016-01-01

    We demonstrate a nonradiative flat band for spoof surface plasmon polaritons bounded on a structured surface with Lieb lattice symmetry in the terahertz regime. First, we theoretically derive the dispersion relation of spoof plasmons in a metallic Lieb lattice based on the electrical circuit model. We obtain three bands, one of which is independent of wave vector. To confirm the theoretical result, we numerically and experimentally observe the flat band in transmission and attenuated total reflection configurations. We reveal that the quality factor of the nonradiative flat-band mode decoupled from the propagating wave is higher than that of the radiative flat-band mode. This indicates that the nonradiative flat-band mode is three-dimensionally confined in the lattice.

  14. Photoacoustic Determination of Non-radiative Relaxation Time of Absorbing Centers in Maize Seeds

    Science.gov (United States)

    Domínguez-Pacheco, A.; Hernández-Aguilar, C.; Cruz-Orea, A.

    2017-07-01

    Using non-destructive photothermal techniques, it is possible to characterize non-homogenous materials to obtain its optical and thermal properties through photoacoustic spectroscopy (PAS). In photoacoustic (PA) phenomena, there are transient states of thermal excitation, when samples absorb the incident light; these states manifest an excitation process that generates the PA signal, being in direct relation with the non-radiative relaxation times with the sample absorbent centers. The objective of this study was to determine the non-radiative relaxation times associated with different absorbent centers of corn seeds ( Zea mays L.), by using PAS. A frequency scan was done at different wavelengths (350 nm, 470 nm and 650 nm) in order to obtain the non-radiative relaxation times with different types of maize seeds.

  15. Exploring Tablet PC Lectures: Lecturer Experiences and Student Perceptions in Biomedicine

    Science.gov (United States)

    Choate, Julia; Kotsanas, George; Dawson, Phillip

    2014-01-01

    Lecturers using tablet PCs with specialised pens can utilise real-time changes in lecture delivery via digital inking. We investigated student perceptions and lecturer experiences of tablet PC lectures in large-enrolment biomedicine subjects. Lecturers used PowerPoint or Classroom Presenter software for lecture preparation and in-lecture pen-based…

  16. Multisite campaign on the open cluster M67. III. Delta Scuti pulsations in the blue stragglers

    CERN Document Server

    Bruntt, H; Suárez, J C; Arentoft, T; Bedding, T R; Bouzid, M Y; Csubry, Z; Dall, T H; Dind, Z E; Frandsen, S; Gilliland, R L; Jacob, A P; Jensen, H R; Kang, Y B; Kim, S -L; Kiss, L L; Kjeldsen, H; Koo, J -R; Lee, J -A; Lee, C -U; Nuspl, J; Sterken, C; Szabó, R

    2007-01-01

    We have made an asteroseismic analysis of the variable blue stragglers in the open cluster M67. The data set consists of photometric time series from eight sites using nine 0.6-2.1 meter telescopes with a time baseline of 43 days. In two stars, EW Cnc and EX Cnc, we detect the highest number of frequencies (41 and 26) detected in delta Scuti stars belonging to a stellar cluster, and EW Cnc has the second highest number of frequencies detected in any delta Scuti star. We have computed a grid of pulsation models that take the effects of rotation into account. The distribution of observed and theoretical frequencies show that in a wide frequency range a significant fraction of the radial and non-radial low-degree modes are excited to detectable amplitudes. Despite the large number of observed frequencies we cannot constrain the fundamental parameters of the stars. To make progress we need to identify the degrees of some of the modes either from multi-colour photometry or spectroscopy.

  17. Kepler photometry of RRc stars: peculiar double-mode pulsations and period doubling

    CERN Document Server

    Moskalik, P; Kolenberg, K; Molnár, L; Kurtz, D W; Szabó, R; Benkő, J M; Nemec, J M; Chadid, M; Guggenberger, E; Ngeow, C -C; Jeon, Y -B; Kopacki, G; Kanbur, S M

    2014-01-01

    We present the analysis of four first overtone RR Lyrae stars observed with the Kepler space telescope, based on data obtained over nearly 2.5yr. All four stars are found to be multiperiodic. The strongest secondary mode with frequency f_2 has an amplitude of a few mmag, 20 - 45 times lower than the main radial mode with frequency f_1. The two oscillations have a period ratio of P_2/P_1 = 0.612 - 0.632 that cannot be reproduced by any two radial modes. Thus, the secondary mode is nonradial. Modes yielding similar period ratios have also recently been discovered in other variables of the RRc and RRd types. These objects form a homogenous group and constitute a new class of multimode RR Lyrae pulsators, analogous to a similar class of multimode classical Cepheids in the Magellanic Clouds. Because a secondary mode with P_2/P_1 ~ 0.61 is found in almost every RRc and RRd star observed from space, this form of multiperiodicity must be common. In all four Kepler RRc stars studied, we find subharmonics of f_2 at ~1/...

  18. Lectures on Classical Integrability

    CERN Document Server

    Torrielli, Alessandro

    2016-01-01

    We review some essential aspects of classically integrable systems. The detailed outline of the lectures consists of: 1. Introduction and motivation, with historical remarks; 2. Liouville theorem and action-angle variables, with examples (harmonic oscillator, Kepler problem); 3. Algebraic tools: Lax pairs, monodromy and transfer matrices, classical r-matrices and exchange relations, non-ultralocal Poisson brackets, with examples (non-linear Schroedinger model, principal chiral field); 4. Features of classical r-matrices: Belavin-Drinfeld theorems, analyticity properties, and lift of the classical structures to quantum groups; 5. Classical inverse scattering method to solve integrable differential equations: soliton solutions, spectral properties and the Gel'fand-Levitan-Marchenko equation, with examples (KdV equation, Sine-Gordon model). Prepared for the Durham Young Researchers Integrability School, organised by the GATIS network. This is part of a collection of lecture notes.

  19. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Françoise Benz

    2002-01-01

    18, 19, 20, 21, 22 November LECTURE FOR POSTGRADUATE STUDENTS From 11:00 hrs - Main Auditorium bldg. 500 Telling the Truth with Statistics R. Barlow / Univ. of Manchester, UK This course of lectures will cover probability, distributions, fitting, errors and confidence levels, for practising High Energy Physicists who need to use Statistical techniques to express their results. Concentrating on these appropriate specialist techniques means that they can be covered in appropriate depth, while assuming only the knowledge and experience of a typical Particle Physicist. The different definitions of probability will be explained, and it will be appear why this basic subject is so controversial; there are several viewpoints and it is important to understand them all, rather than abusing the adherents of different beliefs. Distributions will be covered: the situations they arise in, their useful properties, and the amazing result of the Central Limit Theorem. Fitting a parametrisation to a set of data is one of the m...

  20. Globe: Lecture series

    CERN Multimedia

    2007-01-01

    The LHC: an accelerator of science This series of lectures is all about understanding the scientific and technological challenges of the phenomenal LHC project and assessing its innovations through their everyday applications. Come and take a sneak preview of the LHC! Communicate: the Grid, a computer of global dimensions François Grey, head of communication in CERN’s Information Technology Department How will it be possible for the 15 million billion bytes of data generated by the LHC every year to be handled and stored by a computer that doesn’t have to be the size of a skyscraper? The computer scientists have the answer: the Grid, which will harness the power of tens of thousands of computers all over the world by creating a network of computers and making them operate as one. >>> Lectures are free and require no specialist knowledge. In french. 
 >>> By reservation only: tel. +41 (0)22 767 76 76

  1. Lectures on instantons

    CERN Document Server

    Vandoren, Stefan

    2008-01-01

    This is a self-contained set of lecture notes on instantons in (super) Yang-Mills theory in four dimensions and in quantum mechanics. First the basics are derived from scratch: the regular and singular one-instanton solutions for Yang-Mills theories with gauge groups SU(2) and SU(N), their bosonic and fermionic zero modes, the path integral instanton measure, and supersymmetric Yang-Mills theories in Euclidean space. Then we discuss applications: the \\theta-angle of QCD, the solution of the U(1) problem, the way Higgs fields solve the large-instanton problem, and tunneling and phase transitions in quantum mechanics and in nonabelian gauge theories. These lecture notes are an extension of a review on Yang-Mills and D-instantons written in 2000 by both authors and A.Belitsky

  2. Lecture 2: Software Security

    CERN Document Server

    CERN. Geneva

    2013-01-01

    Computer security has been an increasing concern for IT professionals for a number of years, yet despite all the efforts, computer systems and networks remain highly vulnerable to attacks of different kinds. Design flaws and security bugs in the underlying software are among the main reasons for this. This lecture addresses the following question: how to create secure software? The lecture starts with a definition of computer security and an explanation of why it is so difficult to achieve. It then introduces the main security principles (like least-privilege, or defense-in-depth) and discusses security in different phases of the software development cycle. The emphasis is put on the implementation part: most common pitfalls and security bugs are listed, followed by advice on best practice for security development, testing and deployment. Sebastian Lopienski is CERN’s deputy Computer Security Officer. He works on security strategy and policies; offers internal consultancy and audit services; develops and ...

  3. Lectures on Quantum Gravity

    CERN Document Server

    Gomberoff, Andres

    2006-01-01

    The 2002 Pan-American Advanced Studies Institute School on Quantum Gravity was held at the Centro de Estudios Cientificos (CECS),Valdivia, Chile, January 4-14, 2002. The school featured lectures by ten speakers, and was attended by nearly 70 students from over 14 countries. A primary goal was to foster interaction and communication between participants from different cultures, both in the layman’s sense of the term and in terms of approaches to quantum gravity. We hope that the links formed by students and the school will persist throughout their professional lives, continuing to promote interaction and the essential exchange of ideas that drives research forward. This volume contains improved and updated versions of the lectures given at the School. It has been prepared both as a reminder for the participants, and so that these pedagogical introductions can be made available to others who were unable to attend. We expect them to serve students of all ages well.

  4. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    2, 3, 4, 5 and 6 April REGULAR LECTURE PROGRAMME From 11:00 hrs - Main Auditorium bldg. 500 New Developments in Supersymmetry S. Raby / CERN-TH Introduction to supersymmetric grand unified theories. An introduction to the MSSM and different mechanisms for supersymmetry breaking. Then the details of SU(5) and SO(10) unification, the new gauge sector beyond the standard model, representations of quarks and leptons. Gauge and Yukawa coupling unification and some predictions.

  5. Lectures on knot homology

    CERN Document Server

    Nawata, Satoshi

    2015-01-01

    We provide various formulations of knot homology that are predicted by string dualities. In addition, we also explain the rich algebraic structure of knot homology which can be understood in terms of geometric representation theory in these formulations. These notes are based on lectures in the workshop "Physics and Mathematics of Link Homology" at Centre de Recherches Math\\'ematiques, Universit\\'e de Montr\\'eal.

  6. Lectures on classical electrodynamics

    CERN Document Server

    Englert, Berthold-Georg

    2014-01-01

    These lecture notes cover classical electrodynamics at the level of advanced undergraduates or postgraduates. There is a strong emphasis on the general features of the electromagnetic field and, in particular, on the properties of electromagnetic radiation. It offers a comprehensive and detailed, as well as self-contained, account of material that can be covered in a one-semester course for students with a solid undergraduate knowledge of basic electricity and magnetism.

  7. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    9, 10 and 11 May REGULAR LECTURE PROGRAMME From 10:00 to 12:00 hrs on 9 and 10 May and on 11 May from 11:00 to 12:00 hrs - Main Auditorium bldg. 500 Cosmology and Particle Physics K. Olive / CERN-TH A general overview of the standard big bang model will be presented with special emphasis on astro-particle physics. Specific topics will include: Inflation, Baryoogenesis, Nucleosynthesis and Dark Matter.

  8. B.Gregory Lecture

    CERN Multimedia

    Jacob,M

    1987-01-01

    Troisième série de "Gregory lectures" en mémoire de B.Gregory (1919-1977),DG de 1965 à 1970. La première conférence B.Gregory a été donné par le Prof.V.Weisskopf, son prédécesseur. Chris Greeg (?)de Berkley prend aussi la parole

  9. An LHC Lecture

    CERN Document Server

    Plehn, Tilman

    2009-01-01

    When we try to advance from a solid knowledge of field theory to LHC physics we usually encounter a frustrating problem: in particular Higgs physics and QCD techniques appear as a impenetrable granite block of phenomenological know-how, common lores, and historically grown intuition what works and what does not. I hope this lecture can drill a few holes into the rock and put you into a position to digest advanced writeups as well as some first research papers on the topic.

  10. Lectures for CERN pensioners

    CERN Multimedia

    SC Unit

    2008-01-01

    The CERN Medical Service and the Pensioners Association are pleased to invite CERN pensioners to a series of lectures given by professors and specialists from the Teaching Hospitals and the Faculty of Medicine of the University of Geneva on the following topic: PROMOTION OF OPTIMUM BRAIN AGEING The lectures will take place in the Main CERN Auditorium (Building 60) from 2.30 p.m. to 4.30 p.m. on the following dates: Wednesday 12 November 2008: Assessing the extent of brain ageing Dr Dina ZEKRY Friday 12 December 2008: Can memory decline be prevented? Pr Jean-Pierre MICHEL Thursday 15 January 2009: Diagnosing and treating Alzheimer’s disease Pr Gabriel GOLD Wednesday 25 February 2009: What is the brain reserve? Speaker’s name to be announced at a later date The lectures will be given in French, with transparencies in English, and will be followed by a wide-ranging debate with the participants. CERN Medical Service - Pensioners Association - CERN-ESO (GAC-EPA)

  11. Summer Student Lecture Programme

    CERN Multimedia

    2004-01-01

    Main Auditorium, bldg. 500 More Information DATE TIME LECTURER TITLE Wednesday 7 July 09:15 - 10:00 L. Fayard, O. Ullaland, D. Heagerty (CERN) Programme Presentation Workshops presentation Information on Computing Rules 10:15 - 11:00 R. Aymar (CERN) Introduction to CERN (1/2) 11:15 - 12:00 J. Engelen (CERN) Introduction to CERN (2/2) 15:00 - 16:30 H. Menzel (CERN) An Introduction to Radiation Protection DATE TIME LECTURER TITLE Thursday 8 july 09:15 - 10:00 L. Di Lella (CERN) Introduction to Particle Physics (1/4) 10:15 - 11:00 L. Di Lella (CERN) Introduction to Particle Physics (2/4) 11:15 - 12:00 P. Chomaz (GANIL / CERN) Fundamental questions in modern nuclear physics: The challenge of exotic nuclei (1/2) DATE TIME LECTURER TITLE Friday 9 July 09:15 - 10:00 L. Di Lella (CERN) Introduction to Particle Physics (3/4) 10:15 - 11:00 P. Chomaz (GANIL / CERN) Fundamental questions in modern nuclear physics: The challenge of exotic nuclei (2/2) 11:15 - 12:00 P....

  12. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    5, 6, 7, 8 and 9 March REGULAR LECTURE PROGRAMME From 11:00 hrs - Main Auditorium bldg. 500 Tracking at the LHC K. Safarik / CERN-EP The lecture will start with a short history of particle tracking in high-energy physics. Then we will concentrate on tracking in the LHC experiments. We will discuss various tracking devices proposed for these experiments, dividing them into two large groups: solid state detectors and gas detectors. Their characteristics, as well as their behaviour in different external conditions (i.e. magnetic field, radiation) will be compared. Furthermore, we will turn to the question: how to design a tracker using these various technologies, what are the essential parameters to be taken into account and we will apply these considerations to the proposed the LHC detectors. The last part of the lecture will be devoted to tracking software. We will mention simulation and concentrate on track finding and reconstruction, reviewing different algorithms prototyped for the LHC experiments. We will ...

  13. Lectures for CERN pensioners

    CERN Multimedia

    SC Unit

    2008-01-01

    The CERN Medical Service and the Pensioners Association are pleased to invite CERN pensioners to a series of lectures given by professors and specialists from the Teaching Hospitals and the Faculty of Medicine of the University of Geneva on the following topic: PROMOTION OF OPTIMUM BRAIN AGEING The lectures will take place in the Main CERN Auditorium (Building 60) from 2.30 p.m. to 4.30 p.m. on the following dates: Wednesday 12 November 2008: Assessing the extent of brain ageing Dr Dina ZEKRY Friday 12 December 2008: Can memory decline be prevented? Pr Jean-Pierre MICHEL Thursday 15 January 2009: Diagnosing and treating Alzheimer’s disease Pr Gabriel GOLD Wednesday 25 February 2009: What is the brain reserve? Speaker’s name to be announced at a later date The lectures will be given in French, with transparencies in English, and will be followed by a wide-ranging debate with the participants. CERN Medical Service - Pensioners Association - CERN-ESO (GAC-EPA)

  14. Most recent Web Lectures

    CERN Multimedia

    Steven Goldfarb

    Web Archives of ATLAS Plenary Sessions, Workshops, Meetings, and Tutorials recorded over the past two years are available via the University of Michigan portal here. Most recent additions include the ROOT Workshop held at CERN on March 26-27, the Physics Analysis Tools Workshop held in Bergen, Norway on April 23-27, and the CTEQ Workshop: "Physics at the LHC: Early Challenges" held at Michigan State University on May 14-15. Viewing requires a standard web browser with RealPlayer plug-in (included in most browsers automatically) and works on any major platform. Lectures can be viewed directly over the web or downloaded locally. In addition, you will find access to a variety of general tutorials and events via the portal. Suggestions for events or tutorials to record in 2007, as well as feedback on existing archives is always welcome. Please contact us at wlap@umich.edu. Thank you and enjoy the lectures! The Michigan Web Lecture Team Tushar Bhatnagar, Steven Goldfarb, Jeremy Herr, Mitch McLachlan, Homer A....

  15. Multidimensional modelling of classical pulsating stars

    CERN Document Server

    Muthsam, Herbert J

    2016-01-01

    After an overview of general aspects of modelling the pulsation- convection interaction we present reasons why such simulations (in multidimensions) are needed but, at the same time, pose a considerable challenge. We then discuss, for several topics, what insights multidimensional simulations have either already provided or can be expected to yield in the future. We finally discuss properties of our ANTARES code. Many of these features can be expected to be characteristic of other codes which may possibly be applied to these physical questions in the foreseeable future.

  16. RZ Cassiopeia: Eclipsing Binary with Pulsating Component

    CERN Document Server

    Golovin, A

    2007-01-01

    We report time-resolved VR-band CCD photometry of the eclipsing binary RZ Cas obtained with 38-cm Cassegrain telescope at the Crimean Astrophysical Observatory during July 2004 - October 2005. Obtained lightcurves clearly demonstrates rapid pulsations with the period about 22 minutes. Periodogram analysis of such oscillations also is reported. On the 12, January, 2005 we observed rapid variability with higher amplitude (~0.^m 1) that, perhaps, may be interpreted as high-mass-transfer-rate event and inhomogeneity of accretion stream. Follow-up observations (both, photometric and spectroscopic) of RZ Cas are strictly desirable for more detailed study of such event.

  17. Pulsations, interpulsations, and sea-floor spreading.

    Science.gov (United States)

    Pessagno, E. A., Jr.

    1973-01-01

    It is postulated that worldwide transgressions (pulsations) and regressions (interpulsations) through the course of geologic time are related to the elevation and subsidence of oceanic ridge systems and to sea-floor spreading. Two multiple working hypotheses are advanced to explain major transgressions and regressions and the elevation and subsidence of oceanic ridge systems. One hypothesis interrelates the sea-floor spreading hypothesis to the hypothesis of sub-Mohorovicic serpentinization. The second hypothesis relates the sea-floor spreading hypothesis to a hypothesis involving thermal expansion and contraction.

  18. First Kepler results on compact pulsators - VII. Pulsating subdwarf B stars detected in the second half of the survey phase

    Science.gov (United States)

    Baran, A. S.; Kawaler, S. D.; Reed, M. D.; Quint, A. C.; O'Toole, S. J.; Østensen, R. H.; Telting, J. H.; Silvotti, R.; Charpinet, S.; Christensen-Dalsgaard, J.; Still, M.; Hall, J. R.; Uddin, K.

    2011-07-01

    We present five new pulsating subdwarf B (sdB) stars discovered by the Kepler spacecraft during the asteroseismology survey phase. We perform time series analysis on the nearly continuous month-long Kepler data sets of these five objects; these data sets provide nearly alias-free time series photometry at unprecedented precision. Following an iterative pre-whitening process, we derive the pulsational frequency spectra of these stars, separating out artefacts of known instrumental origin. We find that these new pulsating sdB stars are multiperiodic long-period pulsators of the V1093 Her type, with the number of periodicities ranging from eight (KIC 8302197) to 53 (KIC 11558725). The frequencies and amplitudes are typical of g-mode pulsators of this type. We do not find any evidence for binarity in the five stars from their observed pulsation frequencies. As these are g-mode pulsators, we briefly looked for period spacings for mode identification and found average spacings of about 260 and 145 s. This may indicate l= 1 and 2 patterns. Some modes may show evidence of rotational splitting. These discoveries complete the list of compact pulsators found in the survey phase. Of the 13 compact pulsators, only one star was identified as a short-period (p-mode) V361 Hya pulsator, while all other new pulsators turned out to be V1093 Her class objects. Among the latter objects, two of them seemed to be pure V1093 Her while the others show additional low-amplitude peaks in the p-mode frequency range, suggesting their hybrid nature. Authenticity of these peaks will be tested with longer runs currently under analysis.

  19. The Cepheid mass discrepancy and pulsation-driven mass loss

    NARCIS (Netherlands)

    Neilson, H.R.; Cantiello, M.; Langer, N.

    2011-01-01

    Context. A longstanding challenge for understanding classical Cepheids is the Cepheid mass discrepancy, where theoretical mass estimates using stellar evolution and stellar pulsation calculations have been found to differ by approximately 10−20%. Aims. We study the role of pulsation-driven mass loss

  20. Review and prospect of research on hydraulic pulsation attenuator

    Science.gov (United States)

    Shan, Chang-ji; Zhao, Qi-jun; Dai, Ting-ting; Bian, Yi-duo; Cai, Yan

    2017-09-01

    The pressure pulsation attenuator is able to decrease the fluid fluctuation of the hydraulic pump effectively, so it is widely used in construction machinery. This paper reviews the history and progresses of the research on the pressure pulsation attenuator in China and overseas, summarizes its two types: H-type rigid structure and built-in flexible material, meanwhile, discusses its future research area.

  1. Effect of Molecular Packing and Charge Delocalization on the Nonradiative Recombination of Charge-Transfer States in Organic Solar Cells

    KAUST Repository

    Chen, Xian Kai

    2016-09-05

    In organic solar cells, a major source of energy loss is attributed to nonradiative recombination from the interfacial charge transfer states to the ground state. By taking pentacene–C60 complexes as model donor–acceptor systems, a comprehensive theoretical understanding of how molecular packing and charge delocalization impact these nonradiative recombination rates at donor–acceptor interfaces is provided.

  2. Pulsating low-mass white dwarfs in the frame of new evolutionary sequences. IV. The secular rate of period change

    Science.gov (United States)

    Calcaferro, Leila M.; Córsico, Alejandro H.; Althaus, Leandro G.

    2017-04-01

    Context. An increasing number of low-mass (M⋆/M⊙ ≲ 0.45) and extremely low-mass (ELM, M⋆/M⊙ ≲ 0.18-0.20) white-dwarf stars are being discovered in the field of the Milky Way. Some of these stars exhibit long-period g-mode pulsations, and are called ELMV variable stars. Also, some low-mass pre-white dwarf stars show short-period p-mode (and likely radial-mode) photometric variations, and are designated as pre-ELMV variable stars. The existence of these new classes of pulsating white dwarfs and pre-white dwarfs opens the prospect of exploring the binary formation channels of these low-mass white dwarfs through asteroseismology. Aims: We aim to present a theoretical assessment of the expected temporal rates of change of periods (\\dot{Π}) for such stars, based on fully evolutionary low-mass He-core white dwarf and pre-white dwarf models. Methods: Our analysis is based on a large set of adiabatic periods of radial and nonradial pulsation modes computed on a suite of low-mass He-core white dwarf and pre-white dwarf models with masses ranging from 0.1554 to 0.4352 M⊙, which were derived by computing the non-conservative evolution of a binary system consisting of an initially 1 M⊙ ZAMS star and a 1.4 M⊙ neutron star companion. Results: We computed the secular rates of period change of radial (ℓ = 0) and nonradial (ℓ = 1,2) g and p modes for stellar models representative of ELMV and pre-ELMV stars, as well as for stellar objects that are evolving just before the occurrence of CNO flashes at the early cooling branches. We find that the theoretically expected magnitude of \\dot{Π} of g modes for pre-ELMVs is by far larger than for ELMVs. In turn, \\dot{Π} of g modes for models evolving before the occurrence of CNO flashes are larger than the maximum values of the rates of period change predicted for pre-ELMV stars. Regarding p and radial modes, we find that the larger absolute values of \\dot{Π} correspond to pre-ELMV models. Conclusions: We

  3. Secular Evolution in Mira Variable Pulsations

    CERN Document Server

    Templeton, M R; Willson, L A

    2005-01-01

    Stellar evolution theory predicts that asymptotic giant branch stars undergo a series of short thermal pulses that significantly change their luminosity and mass on timescales of hundreds to thousands of years. Secular changes in these stars resulting from thermal pulses can be detected as measurable changes in period if the star is undergoing Mira pulsations. The American Association of Variable Star Observers (AAVSO) International Database currently contains visual data for over 1500 Mira variables. Light curves for these stars span nearly a century in some cases, making it possible to study the secular evolution of the pulsation behavior on these timescales. In this paper, we present the results of our study of period change in 547 Mira variables using data from the AAVSO. We find non-zero rates of period change, dlnP/dt, at the 2-sigma significance level in 57 of the 547 stars, at the 3-sigma level in 21 stars, and at the level of 6-sigma or greater in eight of the 547. The latter eight stars have been pr...

  4. Impulsively started, steady and pulsated annular inflows

    Science.gov (United States)

    Abdel-Raouf, Emad; Sharif, Muhammad A. R.; Baker, John

    2017-04-01

    A computational investigation was carried out on low Reynolds number laminar inflow starting annular jets using multiple blocking ratios and atmospheric ambient conditions. The jet exit velocity conditions are imposed as steady, unit pulsed, and sinusoidal pulsed while the jet surroundings and the far-field jet inlet upstream conditions are left atmospheric. The reason is to examine the flow behavior in and around the jet inlet under these conditions. The pulsation mode behavior is analyzed based on the resultant of the momentum and pressure forces at the entry of the annulus, the circulation and vortex formation, and the propulsion efficiency of the inflow jets. The results show that under certain conditions, the net force of inflow jets (sinusoidal pulsed jets in particular) could point opposite to the flow direction due to the adverse pressure drops in the flow. The propulsion efficiency is also found to increase with pulsation frequency and the sinusoidal pulsed inflow jets are more efficient than the unit pulsed inflow jets. In addition, steady inflow jets did not trigger the formation of vortices, while unit and sinusoidal pulsed inflow jets triggered the formation of vortices under a certain range of frequencies.

  5. Pulsating variable stars and large spectroscopic surveys

    Science.gov (United States)

    De Cat, Peter

    2017-09-01

    In the past decade, the research of pulsating variable stars has taken a giant leap forward thanks to the photometric measurements provided by space missions like Most, CoRoT, Kepler/K2, and Brite. These missions have provided quasi uninterrupted photometric time-series with an ultra-high quality and a total length that is not achievable from Earth. However, many of the success stories could not have been told without ground-based spectroscopic follow-up observations. Indeed, spectroscopy has some important assets as it can provide (more) accurate information about stellar parameters (like the effective temperature, surface gravity, metallicity, and abundances that are mandatory parameters for an in-depth asteroseismic study), the radial velocity (that is important for the detection of binaries and for the confirmation of cluster membership, if applicable), and the projected rotational velocity (that allows the study of the effects of rotation on pulsations). Fortunately, several large spectroscopic surveys are (becoming) available that can be used for these purposes. For some of these surveys, sub-projects have been initiated with the specific goal to complement space-based photometry. In this review, several spectroscopic surveys are introduced and compared with each other. We show that a large amount of spectroscopic data is (becoming) available for a large variety of objects.

  6. Computational model of miniature pulsating heat pipes.

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Mario J.; Givler, Richard C.

    2013-01-01

    The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heat pipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heat pipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.

  7. Computational model of miniature pulsating heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Mario J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Givler, Richard C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2013-01-01

    The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heat pipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heat pipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.

  8. The pulsation spectrum of VX Hydrae

    CERN Document Server

    Templeton, M R; Dvorak, S; Poklar, R; Butterworth, N; Gerner, H

    2009-01-01

    We present the results of a two-year, multisite observing campaign investigating the high-amplitude delta Scuti star VX Hydrae during the 2006 and 2007 observing seasons. The final data set consists of nearly 8500 V-band observations spanning HJD 2453763.6 to 2454212.7 (2006 January 28 to 2007 April 22). Separate analyses of the two individual seasons of data yield 25 confidently-detected frequencies common to both data sets, of which two are pulsation modes, and the remaining 23 are Fourier harmonics or beat frequencies of these two modes. The 2006 data set had five additional frequencies with amplitudes less than 1.5 mmag, and the 2007 data had one additional frequency. Analysis of the full 2006-2007 data set yields 22 of the 25 frequencies found in the individual seasons of data. There are no significant peaks in the spectrum other than these between 0 and 60 c/d. The frequencies of the two main pulsation modes derived from the 2006 and 2007 observing seasons individually do not differ at the level of 3-si...

  9. The Pulsation Spectrum of VX Hydrae

    Science.gov (United States)

    Templeton, M. R.; Samolyk, G.; Dvorak, S.; Poklar, R.; Butterworth, N.; Gerner, H.

    2009-10-01

    We present the results of a two-year, multisite observing campaign investigating the high-amplitude δ Scuti star VX Hydrae during the 2006 and 2007 observing seasons. The final data set consists of nearly 8500 V-band observations spanning HJD 2453763.6 to 2454212.7 (2006 January 28 to 2007 April 22). Separate analyses of the two individual seasons of data yield 25 confidently detected frequencies common to both data sets, of which two are pulsation modes, and the remaining 23 are Fourier harmonics or beat frequencies of these two modes. The 2006 data set had five additional frequencies with amplitudes less than 1.5 mmag, and the 2007 data had one additional frequency. Analysis of the full 2006–2007 data set yields 22 of the 25 frequencies found in the individual seasons of data. There are no significant peaks in the spectrum other than these between 0 and 60 cycles day-1. The frequencies of the two main pulsation modes derived from the 2006 and 2007 observing seasons individually do not differ at the level of 3σ, and thus we find no conclusive evidence for period change over the span of these observations. However, the amplitude of changed significantly between the two seasons, while the amplitude of remained constant; amplitudes of the Fourier harmonics and beat frequencies of f1 also changed. Similar behavior was seen in the 1950s, and it is clear that VX Hydrae undergoes significant amplitude changes over time.

  10. Research on Non-radial Oscillations of the Sun and Stars in the Early 1970s

    Science.gov (United States)

    Osaki, Y.

    2013-12-01

    I describe some historical background of helio- and astero-seismology research in the early 1970s from my personal recollection, particularly on how our Tokyo research group on non-radial oscillations of stars got started. I also describe my recent research on the super-outburst mechanism of SU UMa-type dwarf novae.

  11. A micro-scale hot-surface device based on non-radiative carrier recombination

    NARCIS (Netherlands)

    Kovalgin, Alexeij Y.; Holleman, J.; Iordache, G.

    2004-01-01

    This work employs the idea of making micro-scale hot-surface devices (e.g. sensors, flow meters, micro reactors, etc) based on generation of heat due to nonradiative recombination of carriers in a thin (13 nm) poly silicon surface layer. An important part of the device is a nano-scale (10-100 nm)

  12. Three lectures on free probability

    OpenAIRE

    2012-01-01

    These are notes from a three-lecture mini-course on free probability given at MSRI in the Fall of 2010 and repeated a year later at Harvard. The lectures were aimed at mathematicians and mathematical physicists working in combinatorics, probability, and random matrix theory. The first lecture was a staged rediscovery of free independence from first principles, the second dealt with the additive calculus of free random variables, and the third focused on random matrix models.

  13. Determination of discharge during pulsating flow

    Science.gov (United States)

    Thompson, T.H.

    1968-01-01

    Pulsating flow in an open channel is a manifestation of unstable-flow conditions in which a series of translatory waves of perceptible magnitude develops and moves rapidly downstream. Pulsating flow is a matter of concern in the design and operation of steep-gradient channels. If it should occur at high stages in a channel designed for stable flow, the capacity of the channel may be inadequate at a discharge that is much smaller than that for which the channel was designed. If the overriding translatory wave carries an appreciable part of the total flow, conventional stream-gaging procedures cannot be used to determine the discharge; neither the conventional instrumentation nor conventional methodology is adequate. A method of determining the discharge during pulsating flow was tested in the Santa Anita Wash flood control channel in Arcadia, Calif., April 16, 1965. Observations of the dimensions and velocities of translatory waves were made during a period of controlled reservoir releases of about 100, 200, and 300 cfs (cubic feet per second). The method of computing discharge was based on (1) computation of the discharge in the overriding waves and (2) computation of the discharge in the shallow-depth, or overrun, part of the flow. Satisfactory results were obtained by this method. However, the procedure used-separating the flow into two components and then treating the shallow-depth component as though it were steady--has no theoretical basis. It is simply an expedient for use until laboratory investigation can provide a satisfactory analytical solution to the problem of computing discharge during pulsating flow. Sixteen months prior to the test in Santa Anita Wash, a robot camera had been designed .and programmed to obtain the data needed to compute discharge by the method described above. The photographic equipment had been installed in Haines Creek flood control channel in Los Angeles, Calif., but it had not been completely tested because of the infrequency of

  14. Weak decays. [Lectures, phenomenology

    Energy Technology Data Exchange (ETDEWEB)

    Wojcicki, S.

    1978-11-01

    Lectures are given on weak decays from a phenomenological point of view, emphasizing new results and ideas and the relation of recent results to the new standard theoretical model. The general framework within which the weak decay is viewed and relevant fundamental questions, weak decays of noncharmed hadrons, decays of muons and the tau, and the decays of charmed particles are covered. Limitation is made to the discussion of those topics that either have received recent experimental attention or are relevant to the new physics. (JFP) 178 references

  15. Lectures in Micro Meteorology

    DEFF Research Database (Denmark)

    Larsen, Søren Ejling

    This report contains the notes from my lectures on Micro scale meteorology at the Geophysics Department of the Niels Bohr Institute of Copenhagen University. In the period 1993-2012, I was responsible for this course at the University. At the start of the course, I decided that the text books...... available in meteorology at that time did not include enough of the special flavor of micro meteorology that characterized the work of the meteorology group at Risø (presently of the Institute of wind energy of the Danish Technical University). This work was focused on Boundary layer flows and turbulence...

  16. Lectures on quantum chromodynamics

    CERN Document Server

    Smilga, Andrei

    2001-01-01

    Quantum chromodynamics is the fundamental theory of strong interactions. It is a physical theory describing Nature. Lectures on Quantum Chromodynamics concentrates, however, not on the phenomenological aspect of QCD; books with comprehensive coverage of phenomenological issues have been written. What the reader will find in this book is a profound discussion on the theoretical foundations of QCD with emphasis on the nonperturbative formulation of the theory: What is gauge symmetry on the classical and on the quantum level? What is the path integral in field theory? How to define the path integ

  17. Lectures on electromagnetism

    CERN Document Server

    Das, Ashok

    2013-01-01

    These lecture notes on electromagnetism have evolved from graduate and undergraduate EM theory courses given by the author at the University of Rochester, with the basics presented with clarity and his characteristic attention to detail. The thirteen chapters cover, in logical sequence, topics ranging from electrostatics, magnetostatics and Maxwell's equations to plasmas and radiation. Boundary value problems are treated extensively, as are wave guides, electromagnetic interactions and fields. This second edition comprises many of the topics expanded with more details on the derivation of vari

  18. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    26, 27, 28, 29 and 30 March REGULAR LECTURE PROGRAMME From 11:00 hrs - Main Auditorium bldg. 500 Introduction to General Relativity and Black Holes T. Damour / IHES, Bures-sur-Yvette, F. Conceptual foundations of General Relativity (GR). Uniqueness of GR. Mathematical framework: tensor calculus, Riemannian geometry, connection, 'spin' connection, curvature, Cartan's form calculus. Hilbert-Einstein action, Einstein equations. Weak gravitational fields. Post Newtonian Approximation. Gravitanional Waves. Exact solutions. Killing vectors. Experimental tests. Black Holes: extensions of the Schwarzschild solution; Kerr-Newman holes; no-hair theorems; energtics of black holes; the membrane approach; quantum mechanics of black holes; Bekenstein entropy; Hawking temperature; black holes and string theory.

  19. Lectures in particle physics

    CERN Document Server

    Green, Dan

    1994-01-01

    The aim of this book on particle physics is to present the theory in a simple way. The style and organization of the material is unique in that intuition is employed, not formal theory or the Monte Carlo method. This volume attempts to be more physical and less abstract than other texts without degenerating into a presentation of data without interpretation.This book is based on four courses of lectures conducted at Fermilab. It should prove very useful to advanced undergraduates and graduate students.

  20. Joseph Mountin Lecture

    Centers for Disease Control (CDC) Podcasts

    2009-10-26

    In this podcast, William H. Foege, MD, MPH delivers the 29th Annual Joseph W. Mountin Lecture. Dr. Foege was a key leader in the smallpox effort and worked as an epidemiologist in the successful eradication campaign in the 1970s. Dr. Foege became chief of the Smallpox Eradication Program at CDC, and was appointed director of CDC in 1977.  Created: 10/26/2009 by Centers for Disease Control and Prevention (CDC).   Date Released: 10/29/2009.

  1. The complex case of V445 Lyr observed with Kepler: two Blazhko modulations, a non-radial mode, possible triple mode RR Lyrae pulsation, and more

    DEFF Research Database (Denmark)

    Guggenberger, E.; Kolenberg, K.; Nemec, J. M.

    2012-01-01

    Rapid and strong changes in the Blazhko modulation of RR Lyrae stars, as they have recently been detected in high precision satellite data, have become a crucial topic in finding an explanation of the long-standing mystery of the Blazhko effect. We present here an analysis of the most extreme cas...

  2. The complex case of V445 Lyr observed with Kepler: two Blazhko modulations, a non-radial mode, possible triple mode RR Lyrae pulsation, and more

    DEFF Research Database (Denmark)

    Guggenberger, E.; Kolenberg, K.; Nemec, J. M.

    2012-01-01

    Rapid and strong changes in the Blazhko modulation of RR Lyrae stars, as they have recently been detected in high precision satellite data, have become a crucial topic in finding an explanation of the long-standing mystery of the Blazhko effect. We present here an analysis of the most extreme cas...

  3. Effects of pulsation rate and viscosity on pulsation-induced taste enhancement: new insights into texture-taste interactions.

    Science.gov (United States)

    Burseg, Kerstin Martha Mensien; Camacho, Sara; Bult, Johannes Hendrikus Franciscus

    2011-05-25

    Oral stimulation with high-tastant concentrations that are alternared with low-tastant concentrations or water rinses (pulsatile stimulation) results in taste intensity ratings that are higher than continuous stimulation with the same average tastant concentration. This study tested the combined effects of taste pulsation rate and viscosity on pulsation-induced taste enhancement in apple juice. According to a tastant-kinetics hypothesis, less pulsation-induced taste enhancement is expected at enhanced pulsation rates in the high-viscous proximal stimulus compared to lower viscous stimuli. High-concentration sucrose apple juice pulses and low-concentration sucrose apple juice intervals were alternated at different pulsation periods (pulse + interval in seconds) every 2.5 s (period length = 5 s) or every 1.25 s (period length = 2.5 s). Pulsed stimuli were presented at two viscosity levels by the addition of pectin (0 and 10 g/L). Sweetness intensities of pulsed stimuli were compared to a continuous reference of the same net but nonalternating sucrose concentration. Sweetness ratings were higher for pulsatile stimuli than for continuous stimuli. In low-viscous stimuli, enhancement depended on the pulsation period and peaked at 5 s periods. In high-viscous stimuli, the same enhancement was observed for both pulsation periods. These results contradict a tastant-kinetics hypothesis of viscosity-induced taste suppression because impaired tastant kinetics by viscosity would predict the opposite: lower pulsation-induced taste enhancement for viscous stimuli, especially at higher pulsation rates. Instead, these observations favor an explanation based on perceptual texture-taste interactions, which predict the observed independence between viscosity and pulsation rate.

  4. Forum: The Lecture and Student Learning. The Lecture's Absent Audience

    Science.gov (United States)

    Sciullo, Nick J.

    2017-01-01

    According to the "Oxford English Dictionary" ("OED"), the noun "lecture" dates from the 14th century and means the "action of reading, perusal. Also, that which is read or perused." This definition, while accurate and resonates today in many college classrooms, ignores a key feature of any lecture. The…

  5. Lectures on Yangian symmetry

    Science.gov (United States)

    Loebbert, Florian

    2016-08-01

    In these introductory lectures we discuss the topic of Yangian symmetry from various perspectives. Forming the classical counterpart of the Yangian and an extension of ordinary Noether symmetries, first the concept of nonlocal charges in classical, two-dimensional field theory is reviewed. We then define the Yangian algebra following Drinfel’d's original motivation to construct solutions to the quantum Yang-Baxter equation. Different realizations of the Yangian and its mathematical role as a Hopf algebra and quantum group are discussed. We demonstrate how the Yangian algebra is implemented in quantum, two-dimensional field theories and how its generators are renormalized. Implications of Yangian symmetry on the two-dimensional scattering matrix are investigated. We furthermore consider the important case of discrete Yangian symmetry realized on integrable spin chains. Finally we give a brief introduction to Yangian symmetry in planar, four-dimensional super Yang-Mills theory and indicate its impact on the dilatation operator and tree-level scattering amplitudes. These lectures are illustrated by several examples, in particular the two-dimensional chiral Gross-Neveu model, the Heisenberg spin chain and { N }=4 superconformal Yang-Mills theory in four dimensions.

  6. Lectures on Quantum Mechanics

    CERN Document Server

    Basdevant, Jean-Louis

    2007-01-01

    Beautifully illustrated and engagingly written, Lectures on Quantum Mechanics presents theoretical physics with a breathtaking array of examples and anecdotes. Basdevant's style is clear and stimulating, in the manner of a brisk classroom lecture that students can follow with ease and enjoyment. Here is a sample of the book's style, from the opening of Chapter 1: "If one were to ask a passer-by to quote a great formula of physics, chances are that the answer would be 'E = mc2'. Nevertheless, the formula 'E=hV' which was written in the same year 1905 by the same Albert Einstein, and which started quantum theory, concerns their daily life considerably more. In fact, of the three watershed years for physics toward the beginning of the 20th century - 1905: the Special Relativity of Einstein, Lorentz and Poincaré; 1915: the General Relativity of Einstein, with its extraordinary reflections on gravitation, space and time; and 1925: the full development of Quantum Mechanics - it is surely the last which has the mos...

  7. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Françoise Benz

    2002-01-01

    Main Auditorium, bldg. 500   DATE TIME LECTURER TITLE Monday 5 August 09:15-10:00 F. GIANOTTI LHC Physics (1/3) 10:15-12:00 T. NAKADA CP Violation (3&4/4) Tuesday 6 August 09:15-10:00 F. GIANOTTI LHC Physics (2/3) 10:15-11:00 R. JACOBSEN From Raw Data to Physics Results (1/3) 11:15-12:00 R. JACOBSEN / T. NAKADA Discussion Session Wednesday 7 August 09:15-10:00 F. GIANOTTI LHC Physics (3/3) 10:15-11:00 R. JACOBSEN From Raw Data to Physics Results (2/3) 11:15-12:00 J. LESGOURDES Cosmology (1/4) 14:00-16:00 C. BENVENUTI Basic Science, Society, and Technological Innovation (Council Chamber, bldg. 503) Thursday 8 August 09:15-10:00 J. LESGOURDES Cosmology (2/4) 10:15-11:00 R. JACOBSEN From Raw Data to Physics Results (3/3) 11:15-12:00 J. CARR / J. LESGOURDES Discussion Session Friday 9 August 09:15-11:00 J. LESGOURDES Cosmology (3&4/4) 11:15-12:00 C. JARLSKOG Historic Lecture 14:00-16:00 Course Review Monday 12 August 09:15-12:00 Students Sessi...

  8. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Françoise Benz

    2002-01-01

    SUMMER STUDENT LECTURE PROGRAMME Main Auditorium, bldg. 500   DATE TIME LECTURER TITLE Monday 29 July 09:15 - 10:00 R. RATTAZZI Beyond the Standard Model (3/3) 10:15 - 11:00 P. WELLS Experimental test of the SM - LEP (3/3) 11:15 - 12:00 P. WELLS Discussion Session 14:00 - 16:00 R. ASSMANN The CLIC Concept for a Future Particle Collider at the Energy Frontier Tuesday 30 July 09:15 - 10:00 F. ANTINORI Heavy Ions (1/2) 10:15 - 12:00 F. DYDAK Neutrino Physics (1&2/4) Wednesday 31 July  09:15 - 10:00 F. ANTINORI Heavy Ions (2/2) 10:15 - 11:00 F. DYDAK Neutrino Physics (3/4) 11:15 - 12:00 F. DYDAK / F. ANTINORI Discussion Session Thursday 1 August 09:15 - 10:00 T. NAKADA CP Violation (1/4) 10:15 - 11:00 F. DYDAK Neutrino Physics (4/4) 11:15 - 12:00 F. BEDESCHI Experimental test of the SM Tevatron (1/2) Friday 2 August 09:15 - 10:00 T. NAKADA CP Violation (2/4) 10:15 ? 11:00 F. BEDESCHI Experimental test of the SM Tevatron (2/2) 11:15 ? 12:00 F. BEDESCHI / T. NAKADA Di...

  9. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    14, 15 and 16 May REGULAR LECTURE PROGRAMME 14, 15 May from 10:00 to 12:00 hrs - Main Auditorium bldg. 500 16 May from 11:00 to 12:00 hrs - Council Chamber, bldg 503 Modern Signal Processing: Wavelets vs. Fourier M. Vetterli / EPFL, Lausanne, CH and UC Berkeley Wavelets have established themselves as an important tool in modern signal processing as well as in applied mathematics. This is linked to several facts, among others: i. New theoretical advances have been achieved, like new forms of 4 time-frequency bases for signal analysis. ii. Efficient computational algorithms are available. iii. Many applications either used similar ideas, like for example the concept of multiresolution, or took advantage of the unified framework provided by wavelets. This combination of elegant theory, efficient algorithms, and successful applications makes the field of wavelets and signal processing quite exciting. It is the purpose of these lectures to establish the theory necessary to understand wavelets and related construct...

  10. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    14, 15 and 16 May REGULAR LECTURE PROGRAMME 14, 15 May from 10:00 to 12:00 hrs - Main Auditorium bldg. 500 16 May from 11:00 to 12:00 hrs - Council Chamber, bldg 503 Modern Signal Processing: Wavelets vs. Fourier M. Vetterli / EPFL, Lausanne, CH and UC Berkeley Wavelets have established themselves as an important tool in modern signal processing as well as in applied mathematics. This is linked to several facts, among others: New theoretical advances have been achieved, like new forms of 4 time-frequency bases for signal analysis. Efficient computational algorithms are available. Many applications either used similar ideas, like for example the concept of multiresolution, or took advantage of the unified framework provided by wavelets. This combination of elegant theory, efficient algorithms, and successful applications makes the field of wavelets and signal processing quite exciting. It is the purpose of these lectures to establish the theory necessary to understand wavelets and related constructions. A...

  11. A Deep Test of Radial Differential Rotation in a Helium-atmosphere White Dwarf. I. Discovery of Pulsations in PG 0112+104

    Science.gov (United States)

    Hermes, J. J.; Kawaler, Steven D.; Bischoff-Kim, A.; Provencal, J. L.; Dunlap, B. H.; Clemens, J. C.

    2017-02-01

    We present the detection of non-radial oscillations in a hot, helium-atmosphere white dwarf using 78.7 days of nearly uninterrupted photometry from the Kepler space telescope. With an effective temperature >30,000 K, PG 0112+104 becomes the hottest helium-atmosphere white dwarf known to pulsate. The rich oscillation spectrum of low-order g-modes includes clear patterns of rotational splittings from consecutive sequences of dipole and quadrupole modes, which can be used to probe the rotation rate with depth in this highly evolved stellar remnant. We also measure a surface rotation rate of 10.17404 hr from an apparent spot modulation in the K2 data. With two independent measures of rotation, PG 0112+104 provides a remarkable test of asteroseismic inference.

  12. Pulsating hydraulic fracturing technology in low permeability coal seams

    Institute of Scientific and Technical Information of China (English)

    Wang Wenchao; Li Xianzhong; Lin Baiquan; Zhai Cheng

    2015-01-01

    Based on the difficult situation of gas drainage in a single coal bed of high gas content and low perme-ability, we investigate the technology of pulsating hydraulic pressure relief, the process of crank plunger movement and the mechanism of pulsating pressure formation using theoretical research, mathematical modeling and field testing. We analyze the effect of pulsating pressure on the formation and growth of fractures in coal by using the pulsating hydraulic theory in hydraulics. The research results show that the amplitude of fluctuating pressure tends to increase in the case where the exit is blocked, caused by pulsating pressure reflection and frictional resistance superposition, and it contributes to the growth of fractures in coal. The crack initiation pressure of pulsating hydraulic fracturing is 8 MPa, which is half than that of normal hydraulic fracturing;the pulsating hydraulic fracturing influence radius reaches 8 m. The total amount of gas extraction is increased by 3.6 times, and reaches 50 L/min at the highest point. The extraction flow increases greatly, and is 4 times larger than that of drilling without fracturing and 1.2 times larger than that of normal hydraulic fracturing. The technology provides a technical measure for gas drainage of high gas content and low permeability in the single coal bed.

  13. Surviving Lecture: A Pedagogical Alternative

    Science.gov (United States)

    Berry, Whitney

    2008-01-01

    Lecture is the approach traditionally used to teach music theory courses. Although efficient in the delivery of large amounts of information in a short period of time, lecture lacks the effectiveness of an active learning approach. "Theory Survivor" is a unique cooperative-learning method based on the Student Teams-Achievement Divisions technique…

  14. La lecture à voix haute

    OpenAIRE

    Victoria Reyzabal, Maria

    2015-01-01

    La lecture à voix haute apparaît comme une technique pour la compréhension active des textes, elle ajoute d’autres possibilités de compréhension à la lecture silencieuse et peut préparer à des pratiques créatives et des productions personnelles.

  15. Sher 25: pulsating but apparently alone

    CERN Document Server

    Taylor, William D; Simón-Díaz, Sergio; Sana, Hugues; Langer, Norbert; Smith, Nathan; Smartt, Stephen J

    2014-01-01

    The blue supergiant Sher25 is surrounded by an asymmetric, hourglass-shaped circumstellar nebula, which shows similarities to the triple-ring structure seen around SN1987A. From optical spectroscopy over six consecutive nights, we detect periodic radial velocity variations in the stellar spectrum of Sher25 with a peak-to-peak amplitude of ~12 km/s on a timescale of about 6 days, confirming the tentative detec-tion of similar variations by Hendry et al. From consideration of the amplitude and timescale of the signal, coupled with observed line profile variations, we propose that the physical origin of these variations is related to pulsations in the stellar atmosphere, rejecting the previous hypothesis of a massive, short-period binary companion. The radial velocities of two other blue supergiants with similar bipolar nebulae, SBW1 and HD 168625, were also monitored over the course of six nights, but these did not display any significant radial velocity variations.

  16. Pc3 pulsations during variable IMF conditions

    Directory of Open Access Journals (Sweden)

    U. Villante

    Full Text Available Pc3 geomagnetic field fluctuations detected at low latitude (L'Aquila, Italy during the passage of a high velocity solar wind stream, characterized by variable interplanetary magnetic field conditions, are analyzed. Higher frequency resonant fluctuations and lower frequency phenomena are simultaneously observed; the intermittent appearance and the variable frequency of the longer period modes can be well interpreted in terms of the variable IMF elements; moreover their polarization characteristics are consistent with an origin related to external waves propagating in antisunward direction. A comparison with simultaneous observations performed at Terra Nova Bay (Antarctica provides additional evidence for a clear relationship between the IMF and Pc3 pulsations also at very high latitudes.

    Key words. Magnetospheric physics (MHD waves and instabilities; solar wind · magnetosphere interactions

  17. Pulsating stars in SuperWASP

    Directory of Open Access Journals (Sweden)

    Holdsworth Daniel L.

    2017-01-01

    Full Text Available SuperWASP is one of the largest ground-based surveys for transiting exoplanets. To date, it has observed over 31 million stars. Such an extensive database of time resolved photometry holds the potential for extensive searches of stellar variability, and provide solid candidates for the upcoming TESS mission. Previous work by e.g. [15], [5], [12] has shown that the WASP archive provides a wealth of pulsationally variable stars. In this talk I will provide an overview of the SuperWASP project, present some of the published results from the survey, and some of the on-going work to identify key targets for the TESS mission.

  18. THE PULSATION MODE OF THE CEPHEID POLARIS

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D. G. [Department of Astronomy and Physics, Saint Mary' s University, Halifax NS B3H 3C3 (Canada); Kovtyukh, V. V.; Usenko, I. A. [Astronomical Observatory, Odessa National University, and Isaac Newton Institute of Chile, Odessa Branch, T. G. Shevkenko Park, 65014 Odessa (Ukraine); Gorlova, N. I., E-mail: turner@ap.smu.ca [Institute of Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2013-01-01

    A previously derived photometric parallax of 10.10 {+-} 0.20 mas, d = 99 {+-} 2 pc, is confirmed for Polaris by a spectroscopic parallax derived using line ratios in high dispersion spectra for the Cepheid. The resulting estimates for the mean luminosity of (M{sub V} ) = -3.07 {+-} 0.01 s.e., average effective temperature of (T{sub eff}) = 6025 {+-} 1 K s.e., and intrinsic color of ((B) - (V)){sub 0} = +0.56 {+-} 0.01 s.e., which match values obtained previously from the photometric parallax for a space reddening of E{sub B-V} = 0.02 {+-} 0.01, are consistent with fundamental mode pulsation for Polaris and a first crossing of the instability strip, as also argued by its rapid rate of period increase. The systematically smaller Hipparcos parallax for Polaris appears discrepant by comparison.

  19. Ambiguity of mapping the relative phase of blood pulsations

    Science.gov (United States)

    Teplov, Victor; Nippolainen, Ervin; Makarenko, Alexander A.; Giniatullin, Rashid; Kamshilin, Alexei A.

    2014-01-01

    Blood pulsation imaging (BPI) is a non-invasive optical method based on photoplethysmography (PPG). It is used for the visualization of changes in the spatial distribution of blood in the microvascular bed. BPI specifically allows measurements of the relative phase of blood pulsations and using it we detected a novel type of PPG fast waveforms, which were observable in limited areas with asynchronous regional blood supply. In all subjects studied, these fast waveforms coexisted with traditional slow waveforms of PPG. We are therefore presenting a novel lock-in image processing technique of blood pulsation imaging, which can be used for detailed temporal characterization of peripheral microcirculation. PMID:25401026

  20. Ambiguity of mapping the relative phase of blood pulsations.

    Science.gov (United States)

    Teplov, Victor; Nippolainen, Ervin; Makarenko, Alexander A; Giniatullin, Rashid; Kamshilin, Alexei A

    2014-09-01

    Blood pulsation imaging (BPI) is a non-invasive optical method based on photoplethysmography (PPG). It is used for the visualization of changes in the spatial distribution of blood in the microvascular bed. BPI specifically allows measurements of the relative phase of blood pulsations and using it we detected a novel type of PPG fast waveforms, which were observable in limited areas with asynchronous regional blood supply. In all subjects studied, these fast waveforms coexisted with traditional slow waveforms of PPG. We are therefore presenting a novel lock-in image processing technique of blood pulsation imaging, which can be used for detailed temporal characterization of peripheral microcirculation.

  1. Lecture Notes: Approximate Molecular Orbital Theory

    DEFF Research Database (Denmark)

    Spanget-Larsen, Jens

    2015-01-01

    Lecture Notes for the introductory course "Quantum Chemistry & Spectroscopy" (Dept. Science, Roskilde University)......Lecture Notes for the introductory course "Quantum Chemistry & Spectroscopy" (Dept. Science, Roskilde University)...

  2. Lectures on LHC physics

    CERN Document Server

    Plehn, Tilman

    2015-01-01

    With the discovery of the Higgs boson, the LHC experiments have closed the most important gap in our understanding of fundamental interactions, confirming that such interactions between elementary particles can be described by quantum field theory, more specifically by a renormalizable gauge theory. This theory is a priori valid for arbitrarily high energy scales and does not require an ultraviolet completion. Yet, when trying to apply the concrete knowledge of quantum field theory to actual LHC physics - in particular to the Higgs sector and certain regimes of QCD - one inevitably encounters an intricate maze of phenomenological know-how, common lore and other, often historically developed intuitions about what works and what doesn’t. These lectures cover three aspects to help understand LHC results in the Higgs sector and in searches for physics beyond the Standard Model: they discuss the many facets of Higgs physics, which is at the core of this significantly expanded second edition; then QCD, to the deg...

  3. TASI Lectures on Inflation

    CERN Document Server

    Baumann, Daniel

    2009-01-01

    In a series of five lectures I review inflationary cosmology. I begin with a description of the initial conditions problems of the Friedmann-Robertson-Walker (FRW) cosmology and then explain how inflation, an early period of accelerated expansion, solves these problems. Next, I describe how inflation transforms microscopic quantum fluctuations into macroscopic seeds for cosmological structure formation. I present in full detail the famous calculation for the primordial spectra of scalar and tensor fluctuations. I then define the inverse problem of extracting information on the inflationary era from observations of cosmic microwave background fluctuations. The current observational evidence for inflation and opportunities for future tests of inflation are discussed. Finally, I review the challenge of relating inflation to fundamental physics by giving an account of inflation in string theory.

  4. Lectures on Yangian Symmetry

    CERN Document Server

    Loebbert, Florian

    2016-01-01

    In these introductory lectures we discuss the topic of Yangian symmetry from various perspectives. Forming the classical counterpart of the Yangian and an extension of ordinary Noether symmetries, first the concept of nonlocal charges in classical, two-dimensional field theory is reviewed. We then define the Yangian algebra following Drinfeld's original motivation to construct solutions to the quantum Yang-Baxter equation. Different realizations of the Yangian and its mathematical role as a Hopf algebra and quantum group are discussed. We demonstrate how the Yangian algebra is implemented in quantum, two-dimensional field theories and how its generators are renormalized. Implications of Yangian symmetry on the two-dimensional scattering matrix are investigated. We furthermore consider the important case of discrete Yangian symmetry realized on integrable spin chains. Finally we give a brief introduction to Yangian symmetry in planar, four-dimensional super Yang-Mills theory and indicate its impact on the dila...

  5. Lectures on amenability

    CERN Document Server

    Runde, Volker

    2002-01-01

    The notion of amenability has its origins in the beginnings of modern measure theory: Does a finitely additive set function exist which is invariant under a certain group action? Since the 1940s, amenability has become an important concept in abstract harmonic analysis (or rather, more generally, in the theory of semitopological semigroups). In 1972, B.E. Johnson showed that the amenability of a locally compact group G can be characterized in terms of the Hochschild cohomology of its group algebra L^1(G): this initiated the theory of amenable Banach algebras. Since then, amenability has penetrated other branches of mathematics, such as von Neumann algebras, operator spaces, and even differential geometry. Lectures on Amenability introduces second year graduate students to this fascinating area of modern mathematics and leads them to a level from where they can go on to read original papers on the subject. Numerous exercises are interspersed in the text.

  6. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    8, 9, 10, 11 and 12 October LECTURES FOR POSTGRADUATE STUDENTS From 10:00 hrs - Main Auditorium bldg. 500 Introduction to Field Theory R. Kleiss / University of Nijmegen, NL Starting from the notion of path integrals as developed by Feynman, we discuss field theory in zero spacetime dimensions. The concepts of perturbation expansions, connected amplitudes, Feynman diagrams, classical solutions, renormalization and the effective action are developed. The model is extended to four spacetime dimensions, and the full Feynman rules for relativisitc scalar theory derived. The S matrix and the concept of unitarity are discussed, leading to the amputation rules for S matrix elements from considerations of unitarity. The rules are extended to include particles with spin-1/2 and spin-1. The high-energy behaviour of the theory is discussed as a method to derive the gauge symmetry of the various models.

  7. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    11, 12, 13, 14 and 15 June REGULAR LECTURE PROGRAMME From 11:00 hrs - Main Auditorium bldg. 500 What have we learned from LEP J. Ellis / CERN-TH The basic formalism of the Standard Model will be reviewed, and the limited state of our knowledge before the start-up of LEP will be recalled. Neutrino counting at LEP will be compared with astrophysical and cosmological constraints. The interpretation of precision electroweak data will be discussed, including their predictions for the top quark and the Higgs boson, and the hints they offer for the future direction beyond the Standard Model: probably a weakly-interacting theory that may be extrapolated up to a grand unification scale. Topics in QCD and heavy-flavour physics will be discussed briefly, and topics in W physics at greater length. Direct LEP searches for the Higgs boson and supersymmetric particles will be discussed, and the prospects for their discoveries at future accelerators will be previewed.

  8. Lecture on Thermal Radiation

    Science.gov (United States)

    Dennis, Brian R.

    2006-01-01

    This lecture will cover solar thermal radiation, particularly as it relates to the high energy solar processes that are the subject of this summer school. After a general review of thermal radiation from the Sun and a discussion of basic definitions, the various emission and absorption mechanisms will be described including black-body emission, bremsstrahlung, free-bound, and atomic line emissions of all kinds. The bulk of the time will be spent discussing the observational characteristics of thermal flare plasma and what can be learned about the flare energy release process from observations of the thermal radiation at all wavelengths. Information that has been learned about the morphology, temperature distribution, and composition of the flare plasma will be presented. The energetics of the thermal flare plasma will be discussed in relation to the nonthermal energy of the particles accelerated during the flare. This includes the total energy, the radiated and conductive cooling processes, and the total irradiated energy.

  9. Lectures on algebraic statistics

    CERN Document Server

    Drton, Mathias; Sullivant, Seth

    2009-01-01

    How does an algebraic geometer studying secant varieties further the understanding of hypothesis tests in statistics? Why would a statistician working on factor analysis raise open problems about determinantal varieties? Connections of this type are at the heart of the new field of "algebraic statistics". In this field, mathematicians and statisticians come together to solve statistical inference problems using concepts from algebraic geometry as well as related computational and combinatorial techniques. The goal of these lectures is to introduce newcomers from the different camps to algebraic statistics. The introduction will be centered around the following three observations: many important statistical models correspond to algebraic or semi-algebraic sets of parameters; the geometry of these parameter spaces determines the behaviour of widely used statistical inference procedures; computational algebraic geometry can be used to study parameter spaces and other features of statistical models.

  10. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    21, 22, 23 November LECTURES FOR POSTGRADUATE STUDENTS From 11:00 hrs - Council Chamber bldg. 503 on 21 November Auditorium, bldg 500 on 22, 23 November Introduction to symmetry breaking phenomena in physics E. Brezin / ENS, Paris, F. The notion of broken symmetries started slowly to emerge in the 19th century. The early studies of Pasteur on the parity asymmetry of life, the studies of Curie on piezoelectricity and on the symmetries of effects versus the symmetry of causes (which clearly excluded spontaneous symmetry breaking), are important historical landmarks. However the possibility of spontaneous symmetry breaking within the usual principles of statistical mechanics, waited for the work of Peierls and Onsager. The whole theory of phase transitions and critical phenomena, as well as the construction of field theoretic models as long distance limit of yet unknown physics, relies nowadays on the concept of criticality associated to spontaneous symmetry breaking. The phenomena of Goldstone bosons, of Meissn...

  11. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    19, 20, 21, 22 and 23 February REGULAR LECTURE PROGRAMME From 11:00 hrs - 19, 20 and 21 February Main Auditorium bldg. 500, 22 and 23 February Council Chamber, bldg 503 Introduction to Cryogenic Engineering J.G. Weisend / SLAC, Stanford, USA Cryogenic engineering is an important speciality at CERN. With the construction of LHC, this technology will have an even greater impact on machine operations. The goal of the course is to give people not working in cryogenics an appreciation of the basic principals and problems associated with the field. The course will also provide a foundation for future learning in cryogenics. Topics to be covered will include: properties of cryogenic fluids and materials, refrigeration, cryostat design, instrumentation, safety and propertiesof He II. Examples of working cryogenic systems, many of them from high energy physics, will be presented.

  12. Lecture critique de Luttwak

    OpenAIRE

    Guichaoua, Mickaël

    2016-01-01

    La grande stratégie de l’Empire romain d’Edward Luttwak, qui fut conseiller militaire du président Reagan, parut pour la première fois en 1974 mais ne fut éditée en français qu’en 1989. Cet ouvrage connaît toujours un grand succès dans les milieux universitaires et particulièrement chez les étudiants. Cette lecture entre dans le cadre de nos préoccupations sur le dialogue militaire entre Anciens et Modernes, sinon les contemporains. En effet, Luttwak explique, dans son introduction, qu’«  il ...

  13. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    8, 9, 10, 11 and 12 October LECTURES FOR POSTGRADUATE STUDENTS From 10:00 hrs - Main Auditorium bldg. 500 Introduction to Field Theory R. Kleiss / University of Nijmegen, NL Starting from the notion of path integrals as developed by Feynman, we discuss field theory in zero spacetime dimensions. The concepts of perturbation expansions, connected amplitudes, Feynman diagrams, classical solutions, renormalization and the effective action are developed. The model is extended to four spacetime dimensions, and the full Feynman rules for relativisitc scalar theory derived. The S matrix and the concept of unitarity are discussed, leading to the amputation rules for S matrix elements from considerations of unitarity. The rules are extended to include particles with spin-1/2 and spin-1. The high-energy behaviour of the theory is discussed as a method to derive the gauge symmetry of the various models.

  14. Göttingen Lectures

    CERN Document Server

    Woyczyński, Wojbor A

    1998-01-01

    These lecture notes are woven around the subject of Burgers' turbulence/KPZ model of interface growth, a study of the nonlinear parabolic equation with random initial data. The analysis is conducted mostly in the space-time domain, with less attention paid to the frequency-domain picture. However, the bibliography contains a more complete information about other directions in the field which over the last decade enjoyed a vigorous expansion. The notes are addressed to a diverse audience, including mathematicians, statisticians, physicists, fluid dynamicists and engineers, and contain both rigorous and heuristic arguments. Because of the multidisciplinary audience, the notes also include a concise exposition of some classical topics in probability theory, such as Brownian motion, Wiener polynomial chaos, etc.

  15. Report of geomagnetic pulsation indices for space weather applications

    Science.gov (United States)

    Xu, Z.; Gannon, Jennifer L.; Rigler, Erin J.

    2013-01-01

    The phenomenon of ultra-low frequency geomagnetic pulsations was first observed in the ground-based measurements of the 1859 Carrington Event and has been studied for over 100 years. Pulsation frequency is considered to be “ultra” low when it is lower than the natural frequencies of the plasma, such as the ion gyrofrequency. Ultra-low frequency pulsations are considered a source of noise in some geophysical analysis techniques, such as aeromagnetic surveys and transient electromagnetics, so it is critical to develop near real-time space weather products to monitor these geomagnetic pulsations. The proper spectral analysis of magnetometer data, such as using wavelet analysis techniques, can also be important to Geomagnetically Induced Current risk assessment.

  16. Search of Secondary Pulsation Modes: Globular cluster (NGC 6496)

    CERN Document Server

    Joshi, Gireesh C

    2016-01-01

    The Fourier-discrete-peridogram are used to identify pulsation modes in variables. We have found two pulsation modes in V1 and V2 among 13 new variables as described by Abbas et al.. The five variables V9 to V13 are not shown close to periodic values by analysis of the frequency distribution of multi-band data and also create difficulty to describe their varied nature. The multi-band periodic values of V1 and V6 are matched with known literature values. The scattering of the varied nature of secondary pulsation modes is eliminated by moving average methodology. The phase curve of secondary mode is found to be more smooth compared to a prominent mode of pulsation.

  17. Unilateral Loss of Spontaneous Venous Pulsations in an Astronaut

    Science.gov (United States)

    Mader, Thomas H.; Gibson, C. Robert; Lee, Andrew G.; Patel, Nimesh; Hart, Steven; Pettit, Donald R.

    2014-01-01

    Spontaneous venous pulsations seen on the optic nerve head (optic disc) are presumed to be caused by fluctuations in the pressure gradient between the intraocular and retrolaminar venous systems. The disappearance of previously documented spontaneous venous pulsations is a well-recognized clinical sign usually associated with a rise in intracranial pressure and a concomitant bilateral elevation of pressure in the subarachnoid space surrounding the optic nerves. In this correspondence we report the unilateral loss of spontaneous venous pulsations in an astronaut 5 months into a long duration space flight. We documented a normal lumbar puncture opening pressure 8 days post mission. The spontaneous venous pulsations were also documented to be absent 21 months following return to Earth.. We hypothesize that these changes may have resulted from a chronic unilateral rise in optic nerve sheath pressure caused by a microgravity-induced optic nerve sheath compartment syndrome.

  18. Stochastic Processes in Yellow and Red Pulsating Variables

    CERN Document Server

    Turner, David G; Colivas, T; Berdnikov, Leonid N; Abdel-Latif, Mohamed Abdel-Sabour

    2009-01-01

    Random changes in pulsation period are well established in cool pulsating stars, in particular the red giant variables: Miras, semi-regulars of types A and B, and RV Tau variables. Such effects are also observed in a handful of Cepheids, the SX Phe variable XX Cyg, and, most recently, the red supergiant variable, BC Cyg, a type C semi-regular. The nature of such fluctuations is seemingly random over a few pulsation cycles of the stars, yet the regularity of the primary pulsation mechanism dominates over the long term. The degree of stochasticity is linked to the dimensions of the stars, the randomness parameter 'e' appearing to correlate closely with mean stellar radius through the period 'P', with an average value of e/P = 0.0136+-0.0005. The physical processes responsible for such fluctuations are uncertain, but presumably originate in temporal modifications of envelope convection in such stars.

  19. LARGE EDDY SIMULATION OF PULSATING TURBULENT OPEN CHANNEL FLOW

    Institute of Scientific and Technical Information of China (English)

    ZOU Li-yong; LIU Nan-sheng; LU Xi-yun

    2004-01-01

    Pulsating turbulent open channel flow has been investigated by the use of Large Eddy Simulation (LES) technique coupled with dynamic Sub-Grid-Scale (SGS) model for turbulent SGS stress to closure the governing equations. Three-dimensional filtered Navier-Stokes equations are numerically solved by a fractional-step method. The objective of this study is to deal with the behavior of the pulsating turbulent open channel flow and to examine the reliability of the LES approach for predicting the pulsating turbulent flow. In this study, the Reynolds number (Reτ ) is chosen as 180 based on the friction velocity and the channel depth. The frequency of the driving pressure gradient for the pulsating turbulent flow ranges low, medium and high value. Statistical turbulence quantities as well as the flow structures are analyzed.

  20. Micro-Channel Embedded Pulsating Heat Pipes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — As the need for thermal control technology becomes more demanding Micro-Channel Embedded Pulsating Heat Pipes (ME-PHPs) represents a sophisticated and enabling...

  1. Nonradiating and radiating modes excited by quantum emitters in open epsilon-near-zero cavities

    CERN Document Server

    Liberal, Iñigo

    2015-01-01

    Controlling the emission and interaction properties of quantum emitters (QEs) embedded within an optical cavity is a key technique in engineering light-matter interactions at the nanoscale, as well as in the development of quantum information processing. State-of-the-art optical cavities are based on high Q photonics crystals and dielectric resonators. However, wealthier responses might be attainable with cavities carved in more exotic materials. Here, we theoretically investigate the emission and interaction properties of QEs embedded in open epsilon-near-zero (ENZ) cavities. Using analytical methods and numerical simulations, it is demonstrated that open ENZ cavities present the unique property of supporting nonradiating modes independently of the geometry of the external boundary of the cavity (shape, size, topology...). Moreover, the possibility of switching between radiating and nonradiating modes enables a dynamic control of both the emission by, and the interaction between, QEs. These phenomena provide...

  2. Non-Radial Instabilities and Progenitor Asphericities in Core-Collapse Supernovae

    CERN Document Server

    Mueller, B

    2014-01-01

    Since core-collapse supernova simulations still struggle to produce robust neutrino-driven explosions in 3D, it has been proposed that asphericities caused by convection in the progenitor might facilitate shock revival by boosting the activity of non-radial hydrodynamic instabilities in the post-shock region. We investigate this scenario in depth using 42 relativistic 2D simulations with multi-group neutrino transport to examine the effects of velocity and density perturbations in the progenitor for different perturbation geometries that obey fundamental physical constraints (like the anelastic condition). As a framework for analysing our results, we introduce semi-empirical scaling laws relating neutrino heating, average turbulent velocities in the gain region, and the shock deformation in the saturation limit of non-radial instabilities. The squared turbulent Mach number, , reflects the violence of aspherical motions in the gain layer, and explosive runaway occurs for ~0.3, corresponding to a reduction of t...

  3. nIFTy galaxy cluster simulations I: dark matter & non-radiative models

    CERN Document Server

    Sembolini, Federico; Pearce, Frazer R; Knebe, Alexander; Kay, Scott T; Power, Chris; Cui, Weiguang; Beck, Alexander M; Borgani, Stefano; Vecchia, Claudio Dalla; Davé, Romeel; Elahi, Pascal Jahan; February, Sean; Huang, Shuiyao; Hobbs, Alex; Katz, Neal; Lau, Erwin; McCarthy, Ian G; Murante, Giuseppe; Nagai, Daisuke; Nelson, Kaylea; Newton, Richard D A; Puchwein, Ewald; Read, Justin I; Saro, Alexandro; Schaye, Joop; Thacker, Robert J

    2015-01-01

    We have simulated the formation of a galaxy cluster in a $\\Lambda$CDM universe using twelve different codes modeling only gravity and non-radiative hydrodynamics (\\art, \\arepo, \\hydra\\ and 9 incarnations of GADGET). This range of codes includes particle based, moving and fixed mesh codes as well as both Eulerian and Lagrangian fluid schemes. The various GADGET implementations span traditional and advanced smoothed-particle hydrodynamics (SPH) schemes. The goal of this comparison is to assess the reliability of cosmological hydrodynamical simulations of clusters in the simplest astrophysically relevant case, that in which the gas is assumed to be non-radiative. We compare images of the cluster at $z=0$, global properties such as mass, and radial profiles of various dynamical and thermodynamical quantities. The underlying gravitational framework can be aligned very accurately for all the codes allowing a detailed investigation of the differences that develop due to the various gas physics implementations employ...

  4. Radiative and nonradiative pathways in multiexciton recombination in giant nanocrystal quantum dots

    Science.gov (United States)

    Malko, Anton; Sampat, Siddharth; Htoon, Han; Vela-Becerra, Javier; Chen, Yongfen; Hollingsworth, Jennifer; Klimov, Victor

    2010-03-01

    Recently,footnotetextY. Chen et al., JACS 130, 5026 (2008) we developed ``giant'' nanocrystal quantum dots (g-NQDs), in which a small emitting core of CdSe is overcoated with a thick shell of a wider-gap CdS. We conduct room-temp measurements of photoluminescence (PL) lifetimes in such g-NQDs as a function of excitation power and a number of shell monolayers. At low pump levels, corresponding to excitation of less than 1 exciton per dot on average (>1, fast (˜1ns) PL component appeared, accompanied by a transition to a sub-linear scaling of PL intensity with . Our findings indicate that while g-NQDs indeed produce suppression of nonradiative Auger recombination,footnotetextF. Garcia-Santamaria et al., Nanoletters 9, 3482 (2009) this suppression is incomplete. We conduct systematic studies of relative efficiencies of nonradiative and radiative processes in these nanostructures.

  5. Observation of non-radiative de-excitation processes in silicon nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Milgram, J.N.; Wojcik, J.; Mascher, P. [Department of Engineering Physics, Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario (Canada); Crowe, I.; Sherliker, B.; Halsall, M.P. [School of Electrical and Electronic Engineering, University of Manchester (United Kingdom); Gwilliam, R.M. [Surrey Ion Beam Centre, Advanced Technology Institute, University of Surrey, Guildford (United Kingdom); Knights, A.P.

    2009-05-15

    We describe the impact of non-radiative de-excitation mechanisms on the optical emission from silicon nanocrystals formed in SiO{sub 2}. Auger excitation via free carriers deliberately introduced through phosphorus ion implantation, shows a monotonic increase with increasing phosphorus concentration which can be modelled adequately using a simple statistical approach. We also report a reduction in nanocrystal luminescence intensity with increasing exposure to UV radiation and suggest this phenomenon results from the introduction of non-radiative defects in the Si/SiO{sub 2} network. The effect of UV radiation varies significantly depending on the sample preparation. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. 3D Convection-pulsation Simulations with the HERACLES Code

    Science.gov (United States)

    Felix, S.; Audit, E.; Dintrans, B.

    2015-10-01

    We present 3D simulations of the coupling between surface convection and pulsations due to the κ-mechanism in classical Cepheids of the red edge of Hertzsprung-Russell diagram's instability strip. We show that 3D convection is less powerful than 2D convection and does not quench the radiative pulsations, leading to an efficient 3D κ-mechanism. Thus, the 3D instability strip is closer to the observed one than the 1D or 2D were.

  7. Self-Pulsating Semiconductor Lasers Theory and Experiment

    CERN Document Server

    Mirasso, C R; Hernández-García, E; Lenstra, D; Lynch, S; Landais, P; Phelan, P; O'Gorman, J; San Miguel, M; Elsasser, W

    1999-01-01

    We report detailed measurements of the pump-current dependency of the self-pulsating frequency of semiconductor CD lasers. A distinct kink in this dependence is found and explained using rate-equation model. The kink denotes a transition between a region where the self-pulsations are weakly sustained relaxation oscillations and a region where Q-switching takes place. Simulations show that spontaneous emission noise plays a crucial role for the cross-over.

  8. Non-radial, non-adiabatic solar-like oscillations in RGB and HB stars

    CERN Document Server

    Grosjean, M; Belkacem, K; Montalban, J; Noels, A; Samadi, R

    2013-01-01

    CoRoT and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. We compare the theoretical spectrum of two red giants in the same region of the HR diagram but in different evolutionary phases. We present here our first results on the inertia, lifetimes and amplitudes of the oscillations and discuss the differences between the two stars.

  9. The effect of non-radial motions on the CDM model predictions

    CERN Document Server

    Popolo, A D

    1998-01-01

    In this paper we show how non-radial motions, originating from the tidal interaction of the irregular mass distribution within and around protoclusters, can solve some of the problems of the CDM model. Firstly the discrepancy between the CDM predicted two-points correlation function of clusters and the observed one. We compare the two-points correlation function, that we obtain taking account of non-radial motions, with that obtained by Sutherland & Efstathiou (1991) from the analysis of Geller & Hucra's (1988) deep redshift survey and with the data points for the APM clusters obtained by Efstathiou et al. (1992). Secondly the problem of the X-ray clusters abundance over-production predicted by the CDM model. In this case we compare the X-ray temperature distribution function, calculated using Press-Schechter theory and Evrard's (1990) prescriptions for the mass-temperature relation, taking also account of the non-radial motions, with Henry & Arnaud (1991) and Edge et al. (1990) X-ray temperature ...

  10. Non-radial solar wind flows induced by the motion of interplanetary coronal mass ejections

    Directory of Open Access Journals (Sweden)

    M. Owens

    2004-12-01

    Full Text Available A survey of the non-radial flows (NRFs during nearly five years of interplanetary observations revealed the average non-radial speed of the solar wind flows to be ~30km/s, with approximately one-half of the large (>100km/s NRFs associated with ICMEs. Conversely, the average non-radial flow speed upstream of all ICMEs is ~100km/s, with just over one-third preceded by large NRFs. These upstream flow deflections are analysed in the context of the large-scale structure of the driving ICME. We chose 5 magnetic clouds with relatively uncomplicated upstream flow deflections. Using variance analysis it was possible to infer the local axis orientation, and to qualitatively estimate the point of interception of the spacecraft with the ICME. For all 5 events the observed upstream flows were in agreement with the point of interception predicted by variance analysis. Thus we conclude that the upstream flow deflections in these events are in accord with the current concept of the large-scale structure of an ICME: a curved axial loop connected to the Sun, bounded by a curved (though not necessarily circular cross section.

    Key words. Interplanetary physics (flare and stream dynamics; interplanetary magnetic fields; interplanetary shocks

  11. Effects of the impurity-host interactions on the nonradiative processes in ZnS:Cr

    Science.gov (United States)

    Tablero, C.

    2010-11-01

    There is a great deal of controversy about whether the behavior of an intermediate band in the gap of semiconductors is similar or not to the deep-gap levels. It can have significant consequences, for example, on the nonradiative recombination. In order to analyze the behavior of an intermediate band, we have considered the effect of the inward and outward displacements corresponding to breathing and longitudinal modes of Cr-doped ZnS and on the charge density for different processes involved in the nonradiative recombination using first-principles. This metal-doped zinc chalcogenide has a partially filled band within the host semiconductor gap. In contrast to the properties exhibited by deep-gap levels in other systems, we find small variations in the equilibrium configurations, forces, and electronic density around the Cr when the nonradiative recombination mechanisms modify the intermediate band charge. The charge density around the impurity is equilibrated in response to the perturbations in the equilibrium nuclear configuration and the charge of the intermediate band. The equilibration follows a Le Chatelier principle through the modification of the contribution from the impurity to the intermediate band and to the valence band. The intermediate band introduced by Cr in ZnS for the concentrations analyzed makes the electronic capture difficult and later multiphonon emission in the charge-transfer processes, in accordance with experimental results.

  12. Moving nonradiating kinks in nonlocal φ4 and φ4-φ6 models.

    Science.gov (United States)

    Alfimov, G L; Medvedeva, E V

    2011-11-01

    We explore the existence of moving nonradiating kinks in nonlocal generalizations of φ(4) and φ(4)-φ(6) models. These models are described by nonlocal nonlinear Klein-Gordon equation, u(tt)-Lu+F(u)=0, where L is a Fourier multiplier operator of a specific form and F(u) includes either just a cubic term (φ(4) case) or cubic and quintic (φ(4)-φ(6) case) terms. The general mechanism responsible for the discretization of kink velocities in the nonlocal model is discussed. We report numerical results obtained for these models. It is shown that, contrary to the traditional φ(4) model, the nonlocal φ(4) model does not admit moving nonradiating kinks but admits solitary waves that do not exist in the local model. At the same time the nonlocal φ(4)-φ(6) model describes moving nonradiating kinks. The set of velocities allowed for these kinks is discrete with the highest possible velocity c(1). This set of velocities is unambiguously determined by the parameters of the model. Numerical simulations show that a kink launched at the velocity c higher than c(1) starts to decelerate, and its velocity settles down to the highest value of the discrete spectrum c(1).

  13. Non-radiation related osteonecrosis of the jaws in dogs: 14 cases (1996 - 2014

    Directory of Open Access Journals (Sweden)

    Santiago ePeralta

    2015-05-01

    Full Text Available Osteonecrosis of the jaws is an entity of major clinical impact characterized by chronically exposed necrotic mandibular or maxillary bone. Its clinicopathological characteristics and possible inciting or risk factors are well described in humans but only anecdotally reported in dogs. Treatment modalities and outcome vary depending on the inciting factors involved and the extent and severity of the lesions. The objectives of this study were to retrospectively describe the clinicopathological features of non-radiation related osteonecrosis of the jaws in a series of 14 dogs, identify possible inciting or risk factors, and report on the surgical treatment and outcome. For all patients, the medical records were used to collect information regarding signalment, clinical signs, characteristics of the oral, jaw and dental lesions, diagnostic imaging findings, histopathological and microbiological analysis, treatment performed and outcome. The data collected showed that non-radiation related osteonecrosis of the jaws appears to be an infrequent clinical entity but of significant impact in dogs; that a history of systemic antibiotics and dental disease is common among affected dogs; that previous dental extractions are commonly associated with ONJ sites; that using a systematic diagnostic approach is essential for diagnosis; and that thorough surgical débridement combined with a course of oral antibiotics was effective in the described dogs affected by advanced non-radiation related osteonecrosis of the jaws.

  14. The Oskar Klein Memorial Lectures

    CERN Document Server

    1991-01-01

    The Oskar Klein Memorial Lectures, instituted in 1988 and supported by the Royal Swedish Academy of Sciences through its Nobel Committee for Physics, are given at Stockholm University in Sweden, where Oskar Klein was professor in Theoretical Physics 1930-1962.Volume 1 contains the 1988 lectures on "Symmetry and Physics" and "From the Bethe-Hulthén Hypothesis to the Yang-Baxter Equation," given by C N Yang, Nobel Prize winner (1957) and professor at the State University of New York at Stony Brook. The 1989 lectures on "Beyond the Standard Models," referring to models for cosmology and elementar

  15. To Lecture or Not to Lecture? That is the Question.

    Science.gov (United States)

    Oja, Kenneth John; Kelly, Lesly

    2016-01-01

    A quasi-experimental mixed-methods study compared the effects of an unfolding case study with lecture in a nursing orientation class on new graduate registered nurses' knowledge, perceived learning, and satisfaction with the instructional method. Although results showed that the unfolding case study was engaging, learners who received content in a lecture format achieved significantly higher posttest scores. Nursing professional development specialists will find this article helpful when considering instructional methods for new graduate registered nurses.

  16. Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: III. The pre-ELM white dwarf instability strip

    CERN Document Server

    Córsico, A H; Serenelli, A M; Kepler, S O; Jeffery, C S; Corti, M A

    2016-01-01

    Two low-mass pre-white dwarfs, which could be precursors of ELM white dwarfs, have been observed to show multiperiodic photometric variations. They could constitute a new class of pulsating low-mass pre-white dwarf stars. We present a detailed nonadiabatic pulsation study of such stars, employing full evolutionary sequences of low-mass He-core pre-white dwarf models. We have considered models in which element diffusion is accounted for and also models in which it is neglected. We confirm and explore in detail a new instability strip in the domain of low gravities and low effective temperatures of the $T_{\\rm eff}-\\log g$ diagram, where low-mass pre-white dwarfs are currently found. The destabilized modes are radial and nonradial $p$ and $g$ modes excited by the $\\kappa-\\gamma$ mechanism acting mainly at the zone of the second partial ionization of He, with non-negligible contributions from the region of the first partial ionization of He and the partial ionization of H. The computations with element diffusion...

  17. The Oskar Fehr Lecture.

    Science.gov (United States)

    Weiss, J S

    2016-06-01

    The first Oskar Fehr lecture is given in honour of Professor Fehr, a well respected ophthalmologist, who was head physician of the Department of Eye Diseases at the Rudolf Virchow Hospital from 1918. He practiced there until 1938, when he was forbidden to enter the clinic because he was Jewish and subject to the anti-Semitic laws that were instituted after the rise of the Nazi party. Dr. Fehr escaped to Great Britain, where he practiced ophthalmology into his eighties. He was the first to distinguish between granular corneal dystrophy, lattice corneal dystrophy and macular corneal dystrophy. The topic of the first Oskar Fehr lecture is Schnyder corneal dystrophy (SCD), an autosomal dominantly inherited corneal dystrophy associated with abnormal cholesterol deposition in the cornea. The clinical, histopathologic and genetic findings of 115 individuals with SCD followed over 18 years are discussed. The impact of systemic cholesterol metabolism on other diseases is reviewed. Corneal findings in SCD are predictable on the basis of patient age. All patients develop progressive corneal haze because of abnormal deposition of corneal lipid, but only half of patients with SCD have evidence of corneal crystals. The prior name for this disease, Schnyder crystalline corneal dystrophy, led me to create the International Committee for the Classification of Corneal Dystrophies, in order to create a more up-to-date and accurate nomenclature for SCD and other corneal dystrophies. The name was then changed to Schnyder corneal dystrophy. Histopathology of excised SCD corneas demonstrates abnormal deposition of only HDL cholesterol. Mutations in the UBIAD1 gene result in SCD. Three dimensional protein modeling shows that mutations result in impaired vitamin K synthesis, suggesting a common link between vitamin K and cholesterol metabolism. UBIAD1 mutations are associated with other diseases, such as bladder carcinoma and Parkinson's disease like findings in Drosophila. Studies of the

  18. Introductory Lectures on Collider Physics

    Science.gov (United States)

    Tait, Tim M. P.; Wang, Lian-Tao

    2013-12-01

    These are elementary lectures about collider physics. They are aimed at graduate students who have some background in computing Feynman diagrams and the Standard Model, but assume no particular sophistication with the physics of high energy colliders.

  19. SABRE observations of Pi2 pulsations: case studies

    Science.gov (United States)

    Bradshaw, E. G.; Lester, M.

    1997-01-01

    The characteristics of substorm-associated Pi2 pulsations observed by the SABRE coherent radar system during three separate case studies are presented. The SABRE field of view is well positioned to observe the differences between the auroral zone pulsation signature and that observed at mid-latitudes. During the first case study the SABRE field of view is initially in the eastward electrojet, equatorward and to the west of the substorm-enhanced electrojet current. As the interval progresses, the western, upward field-aligned current of the substorm current wedge moves westward across the longitudes of the radar field of view. The westward motion of the wedge is apparent in the spatial and temporal signatures of the associated Pi2 pulsation spectra and polarisation sense. During the second case study, the complex field-aligned and ionospheric currents associated with the pulsation generation region move equatorward into the SABRE field of view and then poleward out of it again after the third pulsation in the series. The spectral content of the four pulsations during the interval indicate different auroral zone and mid-latitude signatures. The final case study is from a period of low magnetic activity when SABRE observes a Pi2 pulsation signature from regions equatorward of the enhanced substorm currents. There is an apparent mode change between the signature observed by SABRE in the ionosphere and that on the ground by magnetometers at latitudes slightly equatorward of the radar field of view. The observations are discussed in terms of published theories of the generation mechanisms for this type of pulsation. Different signatures are observed by SABRE depending on the level of magnetic activity and the position of the SABRE field of view relative to the pulsation generation region. A twin source model for Pi2 pulsation generation provides the clearest explanation of the signatures observed Acknowledgements. The authors are grateful to Prof. D. J. Southwood

  20. Lectures on general relativity

    CERN Document Server

    Papapetrou, Achille

    1974-01-01

    This book is an elaboration of lecture notes for the graduate course on General Rela­ tivity given by the author at Boston University in the spring semester of 1972. It is an introduction to the subject only, as the time available for the course was limited. The author of an introduction to General Relativity is faced from the beginning with the difficult task of choosing which material to include. A general criterion as­ sisting in this choice is provided by the didactic character of the book: Those chapters have to be included in priority, which will be most useful to the reader in enabling him to understand the methods used in General Relativity, the results obtained so far and possibly the problems still to be solved. This criterion is not sufficient to ensure a unique choice. General Relativity has developed to such a degree, that it is impossible to include in an introductory textbook of a reasonable length even a very condensed treatment of all important problems which have been discussed unt...

  1. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    Main Auditorium bldg. 500 Date Time Lecturer Title Monday 16 July 9:15 10:15 11:15 A. Pich O. Brüning / CERN C. Gaspar / CERN Particle Physics: the Standard Model (1/8) Accelerators (1/5) Trigger and Data Acquisition (1/3) Tuesday 17 July 9:15 10:15 11:15 A. Pich O. Brüning / CERN C. Gaspar / CERN Particle Physics: the Standard Model (2/8) Accelerators (2/5) Trigger and Data Acquisition (2/3) Wednesday 18 July 9:15 10:15 11:15 A. Pich O. Brüning / CERN A. Pich and O. Brüning Particle Physics: the Standard Model (3/8) Accelerators (3/5) Discussion Session Thursday 19 July 9:15 10:15 11:15 A. Pich O. Brüning / CERN C. Gaspar / CERN Particle Physics: the Standard Model (4/8) Accelerators (4/5) Trigger and Data Acquisition (3/3) Friday 20 July 9:15 10:15 11:15 A. Pich O. Brüning / CERN A. Pich and O. Brüning Particle Physics: the Standard Model (5/8) Accelerators (5/5) Discussion Session Monday 23 July 9:15 10:15 11:15 A. Pich R. Jacobse...

  2. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    Main Auditorium bldg. 500 Date Time Lecturer Title Monday 23 July 9:15 10:15 11:15 A. Pich R. Jacobsen / LBLN, Berkeley (USA) T. Cass / CERN Particle Physics: the Standard Model (6/8) From Raw Data to Physics Results (1/3) Computing at CERN (1/3) Tuesday 24 July 9:15 10:15 11:15 A. Pich R. Jacobsen / LBLN, Berkeley (USA) T. Cass / CERN Particle Physics: the Standard Model (7/8) From Raw Data to Physics Results (2/3) Computing at CERN (2/3) Wednesday 25 July 9:15 10:15 11:15 A. Pich R. Jacobsen / LBLN, Berkeley (USA) A. Pich and R. Jacobsen J. Tuckmantel / CERN Particle Physics: the Standard Model (8/8) From Raw Data to Physics Results (3/3) Discussion Session Superconducting cavities Thursday 26 July 9:15 10:15 11:15 T. Nakada / CERN P. Wells / CERN T. Cass / CERN Violation of Particle Anti-particle Symmetry (1/3) LEP Physics (1/4) Computing at CERN (3/3) Friday 27July 9:15 10:15 11:15 T. Nakada / CERN P. Wells / CERN T. Nakada; T. Cass T. Nakada in main auditorium T. Cass in TH auditorium Violati...

  3. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    Main Auditorium bldg. 500 Date Time Lecturer Title Monday 30 July 9:15 10:15 11:15 G. Guidice / CERN T. Nakada / CERN P. Wells / CERN Beyond the Standard Model (1/3) Violation of Particle Anti-particle Symmetry (3/3) LEP Physics (3/4) Tuesday 31 July 9:15 10:15 11:15 G. Guidice / CERN F. Dydak / CERN P. Wells / CERN P. Lebrun / CERN P. Lebrun / CERN Beyond the Standard Model (2/3) Neutrino Physics (1/4) LEP Physics (4/4) Superconducting Technology for particle accelerators (1/2) Superconducting Technology for particle accelerators (2/2) Wednesday 1 August 9:15 10:15 11:15 G. Guidice / CERN F. Dydak / CERN G. Guidice; P. Wells G. Guidice in main auditorium, P. Wells in TH auditorium) O. Grobner / CERN O. Grobner / CERN Beyond the Standard Model (3/3) Neutrino Physics (2/4) Discussion Session Ultra High Vacuum Technology (1/2) Ultra High Vacuum Technology (2/2) Thursday 2 August 9:15 10:15 11:15 F. Antinori / CERN F. Dydak / CERN J. Aysto / CERN Heavy Ions (1/2) Neutrino Physics (3/4) Isolde Physics O...

  4. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    Main Auditorium bldg. 500 Date Time Lecturer Title Wednesday 4 July 9:15 10:15 11:15 14:00 15:00 15:45 L. Maiani / CERN L. Maiani / CERN M. Franklin / CERN G. Stevenson M. Diemoz O. Ullaland Introduction to CERN & Particle Physics (1/2) Introduction to CERN & Particle Physics (2/2) Classic Experiments (1/3) CERN Radiation Protection CERN Information on Activities CERN Intro to workshops Thursday 5 July 9:15 10:15 11:15 14:00 15:00 16:30 M. Franklin / CERN M. Franklin / CERN M. Franklin / CERN F. Close F. Close   Classic Experiments (2/3) Classic Experiments (3/3) Discussion session Particle Physics (for non-physics students) (1/4) Particle Physics (for non-physics students) (2/4) Welcome Drink Friday 6 July 9:15 10:15 F. Close F. Close Particle Physics (for non-physics students) (3/4) Particle Physics (for non-physics students) (4/4) Monday 9 July 9:15 10:15 11:15 R. Kleiss / CERN L. Rolandi / CERN L. Rolandi / CERN Fundamental Concepts of Particle Physics (1/6) Big Experime...

  5. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    Main Auditorium bldg. 500 Date Time Lecturer Title Wednesday 4 July 9:15 10:15 11:15 14:00 15:00 15:45 L. Maiani / CERN L. Maiani / CERN M. Franklin / CERN G. Stevenson M. Diemoz O. Ullaland Introduction to CERN & Particle Physics (1/2) Introduction to CERN & Particle Physics (2/2) Classic Experiments (1/3) CERN Radiation Protection CERN Information on Activities CERN Intro to workshops Thursday 5 July 9:15 10:15 11:15 14:00 15:00 16:30 M. Franklin / CERN M. Franklin / CERN M. Franklin / CERN F. Close F. Close   Classic Experiments (2/3) Classic Experiments (3/3) Discussion session Particle Physics (for non-physics students) (1/4) Particle Physics (for non-physics students) (2/4) Welcome Drink Friday 6 July 9:15 10:15 F. Close F. Close Particle Physics (for non-physics students) (3/4) Particle Physics (for non-physics students) (4/4) Further information can be obtained on the web at the following URL: http://cern.web.cern.ch/CERN/Divisions/PE/HRS/Recruitment/sum_prog99.html

  6. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    Main Auditorium bldg. 500 Date Time Lecturer Title Monday 6 August 9:15 10:15 11:15 F. Gianotti / CERN J. Carr / CERN E. Copeland / Centre for Theoretical Physics University of Sussex, UK LHC Physics (1/3) Astroparticle Physics (1/3) Introduction to Cosmology (1/2) Tuesday 7 August 9:15 10:15 11:15 14:00 15:00 F. Gianotti / CERN J. Carr / CERN E. Copeland / Centre for Theoretical Physics University of Sussex, UK LHC Physics (2/3) Astroparticle Physics (2/3) Introduction to Cosmology (2/2) Wednesday 8 August 9:15 10:15 11:15 14:00 15:00 F. Gianotti / CERN J. Carr / CERN J. Carr; F. Gianotti J. Carr in main auditorium F. Gianotti in TH auditorium LHC Physics (2/3) Astroparticle Physics (2/3) Discussion Session Thursday 9 August 9:15 10:15 11:15 G. Veneziano / CERN G. Veneziano; E. Copeland G. Veneziano in main auditorium E. Copeland in TH auditorium Dreams of a Finite Theory (1/2) Student Session (1/3) Discussion Session Friday 10 August 9:15 10:15 11:15 G. Veneziano / CERN L. Okun / CERN Student Se...

  7. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    Main Auditorium bldg. 500 Date Time Lecturer Title Monday 9 July 9:15 10:15 11:15 R. Kleiss / CERN L. Rolandi / CERN L. Rolandi / CERN Fundamental Concepts of Particle Physics (1/6) Big Experiments Discussion Session Tuesday 10 July 9:15 10:15 11:15 R. Kleiss / CERN R. Kleiss / CERN C. Joram Fundamental Concepts of Particle Physics (2/6) Fundamental Concepts of Particle Physics (3/6) Particle Detectors (1/5) Wednesday 11 July 9:15 10:15 11:15 R. Kleiss / CERN C. Joram / CERN R. Kleiss / C. Joram Fundamental Concepts of Particle Physics (4/6) Particle Detectors (2/5) Discussion Session Thursday 12 July 9:15 10:15 11:15 R. Kleiss / CERN C. Joram / CERN C. Joram / CERN Fundamental Concepts of Particle Physics (5/6) Particle Detectors (3/5) Particle Detectors (4/5) Friday 13 July 9:15 10:15 11:15 R. Kleiss / CERN C. Joram / CERN R. Kleiss / C. Joram Fundamental Concepts of Particle Physics (6/6) Particle Detectors (5/5) Discussion Session Monday 16 July 9:15 10:15 11:15 A. Pich O. Brüning C...

  8. Lectures on Bound states

    CERN Document Server

    Hoyer, Paul

    2016-01-01

    Even a first approximation of bound states requires contributions of all powers in the coupling. This means that the concept of "lowest order bound state" needs to be defined. In these lectures I discuss the "Born" (no loop, lowest order in $\\hbar$) approximation. Born level states are bound by gauge fields which satisfy the classical field equations. As a check of the method, Positronium states of any momentum are determined as eigenstates of the QED Hamiltonian, quantized at equal time. Analogously, states bound by a strong external field $A^\\mu(\\xv)$ are found as eigenstates of the Dirac Hamiltonian. Their Fock states have dynamically created $e^+e^-$ pairs, whose distribution is determined by the Dirac wave function. The linear potential of $D=1+1$ dimensions confines electrons but repels positrons. As a result, the mass spectrum is continuous and the wave functions have features of both bound states and plane waves. The classical solutions of Gauss' law are explored for hadrons in QCD. A non-vanishing bo...

  9. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    14, 15, 16, 17, 18 January LECTURES FOR POSTGRADUATE STUDENTS From 11:00 hrs - Auditorium, bldg 500 Superconducting materials suitable for magnets D.C. Larbalestier / Univ. of Wisconsin, USA The range of materials available for superconducting magnets is steadily expanding, even as the choice of material becomes potentially more complex. When virtually all magnets were cooled by helium at ~2-5 K it was easy to separate the domain of Nb-Ti from those of Nb3Sn applications and very little surprise that more than 90% of all magnets are still made from Nb-Ti. But the development of useful conductors of the Bi-Sr-Ca-Cu-O and YBa2Cu3Ox high temperature superconductors, coupled to the recent discovery of the 39 K superconductor MgB2 and the developing availability of cryocoolers suggests that new classes of higher temperature, medium field magnets based on other than Nb-based conductors could become available in the next 5-10 years. My talks will discuss the essential physics and materials science of these 5 classes...

  10. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2002-01-01

    14, 15, 16, 17, 18 January LECTURE SERIES From 11:00 hrs - Auditorium, bldg 500 Superconducting materials suitable for magnets D.C. Larbalestier / Univ. of Wisconsin, USA The range of materials available for superconducting magnets is steadily expanding, even as the choice of material becomes potentially more complex. When virtually all magnets were cooled by helium at ~2-5 K it was easy to separate the domain of Nb-Ti from those of Nb3Sn applications and very little surprise that more than 90% of all magnets are still made from Nb-Ti. But the development of useful conductors of the Bi-Sr-Ca-Cu-O and YBa2Cu3Ox high temperature superconductors, coupled to the recent discovery of the 39 K superconductor MgB2 and the developing availability of cryocoolers suggests that new classes of higher temperature, medium field magnets based on other than Nb-based conductors could become available in the next 5-10 years. My talks will discuss the essential physics and materials science of these 5 classes of material - Nb-Ti...

  11. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    27, 28, 29 June and 2, 3 July REGULAR LECTURE PROGRAMME From 11:00 hrs - Council Chamber bldg. 503 on 27, 28, 29 June and Auditorium, bldg 500 on 2, 3 July Particle Identification at the LHC P. Eerola / Lund University, SE The LHC experiments will explore new frontiers of particle physics. To maximize the physics potential of LHC, we need identification of leptons, hadrons, photons and 'invisible' particles. This is realized through reconstruction of electrons and muons, charged particle tracking and identification, b- and tau-tagging, and jet reconstruction. In addition, missing energy has to be measured in order to look for signatures of invisible particles. The experimental conditions posed by the collider, which will be operating at higher energy and luminosity than the present ones, are demanding. A large dynamical range is required in order to measure energies and momenta ranging from below one GeV to several TeVs. The detectors should be able to cope with the 40 MHz collision rate, with a large number ...

  12. John Adams Lecture

    CERN Multimedia

    PH Department

    2010-01-01

    13 December 2010 14:30 - Council Chamber, Bldg.503-1-001 Accelerator Breakthroughs, Achievements and Lessons from the Tevatron Collider V. Shiltsev / Fermilab’s Accelerator Physics Centre This year we celebrate the 25th anniversary of the first proton-antiproton collisions in the Tevatron. For two and a half decades the Tevatron at Fermilab (Batavia, IL, USA) was a centerpiece of the US and world’s High Energy Physics as the world’s highest energy particle collider at 1.8 TeV center of mass energy. While funding agencies are deciding on a 3-year extension of the Collider Run II operation through 2014, we – in this 2010 John Adams Lecture - will take a look in exciting story of the Tevatron: the story of long preparations, great expectations, numerous difficulties, years of “blood and sweat”, continuous upgrades, exceeding original goals (by a factor of 400) and high emotions. An accelerator scientist prospective will be given on a wide spectrum o...

  13. ACADEMIC TRAINING LECTURE

    CERN Multimedia

    Academic Training; Tel. 73127

    2001-01-01

    27, 28, 29 June and 2, 3 July REGULAR LECTURE PROGRAMME From 11:00 hrs - Council Chamber bldg. 503 on 27, 28, 29 June and Auditorium, bldg 500 on 2, 3 July Particle Identification at the LHC P. Eerola / Lund University, SE The LHC experiments will explore new frontiers of particle physics. To maximize the physics potential of LHC, we need identification of leptons, hadrons, photons and 'invisible' particles. This is realized through reconstruction of electrons and muons, charged particle tracking and identification, b- and tau-tagging, and jet reconstruction. In addition, missing energy has to be measured in order to look for signatures of invisible particles. The experimental conditions posed by the collider, which will be operating at higher energy and luminosity than the present ones, are demanding. A large dynamical range is required in order to measure energies and momenta ranging from below one GeV to several TeVs. The detectors should be able to cope with the 40 MHz collision rate, with a large number ...

  14. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Françoise Benz

    2002-01-01

    Main Auditorium, bldg. 500   DATE TIME LECTURER TITLE Monday 22 July 09:15 - 10:00 A. PICH Standard Model (6/8) 10:15 - 11:00 J. CARR  Astroparticles (1/3) 11:15 - 12:00 J. SHIERS Computing (1/3) Tuesday 23 July 09:15 - 10:00 A. PICH Standard Model (7/8) 10:15 - 11:00 J. CARR  Astroparticles (2/3) 11:15 - 12:00 J. SHIERS Computing (2/3) Wednesday 24July 09:15 - 10:00 A. PICH Standard Model (8/8) 10:15 - 11:00 J. CARR  Astroparticles (3/3) 11:15 - 12:00 Discussion Session 14:00 - 16:00 O. GROBNER UHV Technology Thursday 25 July (Theory Auditorium) 09:15 - 10:00 R. RATTAZZI Beyond the Standard Model (1/3) (TH) 10:15 - 11:00 P. WELLS Experimental test of the SM - LEP (1/3) (TH) 11:15 - 12:00 J. SHIERS Computing (3/3) (TH) Friday 26 July 09:15 - 10:00 R. RATTAZZI Beyond the Standard Model (2/3) 10:15 - 11:00 P. WELLS Experimental test of the SM - LEP (2/3) 11:15 - 12:00 Discussion Session Monday 29 July 09:15 - 10:00  R...

  15. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Françoise Benz

    2002-01-01

    Main Auditorium, bldg. 500   DATE TIME LECTURER TITLE Monday 15 July 09:15 - 10:00 A. PICH Standard Model (1/8) 10:15 - 11:00 O. BRÜNING Accelerators (1/5) 11:15 - 12:00 C. GASPAR Trigger and Data Acquisition (1/3) Tuesday 16 July 09:15 - 10:00 A. PICH Standard Model (2/8) 10:15 - 11:00 O. BRÜNING Accelerators (2/5) 11:15 - 12:00 C. GASPAR Trigger and Data Acquisition (2/3) Wednesday 17 July 09:15 - 10:00 A. PICH Standard Model (3/8) 10:15 - 11:00 O. BRÜNING Accelerators (3/5) 11:15 - 12:00 Discussion Session Thursday 18 July 09:15 - 10:00 A. PICH Standard Model (4/8) 10:15 - 11:00 O. BRÜNING Accelerators (4/5) 11:15 - 12:00 C. GASPAR Trigger and Data Acquisition (3/3) Friday 19 July 09:15 - 10:00 A. PICH Standard Model (5/8) 10:15 - 11:00 O. BRÜNING Accelerators (5/5) 11:15 - 12:00 Discussion Session Monday 22 July 09:15 - 10:00 A. PICH Standard Model (6/8) 10:15 - 11:00 T. WENAUS From Raw Data to Physics ...

  16. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Françoise Benz

    2002-01-01

    Main Auditorium, bldg. 500   DATE TIME LECTURER TITLE Monday 8 July 09:15 - 10:00 R. KLEISS Fundamental Concepts of Particle Physics (1/6) 10:15 - 11:00 C. JORAM Particle Detectors (2/5) 11:15 - 12:00 M. FRANKLIN Classic Experiments (1/3) 14:00 - 15:00 M. LINDROOS Isolde 15:30 - 16:30 M. LINDROOS Visit of the Experiment Tuesday 9 july 09:15 - 10:00 R. KLEISS Fundamental Concepts of Particle Physics (2/6) 10:15 - 11:00 C. JORAM Particle Detectors (3/5) 11:15 - 12:00 M. FRANKLIN Classic Experiments (2/3) Wednesday 10 July 09:15 - 10:00 R. KLEISS Fundamental Concepts of Particle Physics (3/6) 10:15 - 11:00 C. JORAM Particle Detectors (4/5) 11:15 - 12:00 Discussion Session Thursday 11 July 09:15 - 10:00 R. KLEISS Fundamental Concepts of Particle Physics (4/6) 10:15 - 11:00 C. JORAM Particle Detectors (5/5) 11:15 - 12:00 M. FRANKLIN Classic Experiments (3/3) Friday 12 July 09:15 - 11:00 R. KLEISS Fundamental Concepts of Particle Physics (5&6/6) 11:15 ...

  17. SUMMER STUDENT LECTURE PROGRAMME

    CERN Multimedia

    Françoise Benz

    2002-01-01

    Main Auditorium, bldg. 500   DATE TIME LECTURER TITLE Wednesday 3 July 09:15 - 10:00 L. FAYARD, O. ULLALAND Presentation of the Summer Student Programm 10:15 - 12:00 L. MAIANI Introduction to CERN (1&2/2) 14:00 - 15:00 G. Stevenson Radiation Protection (Council Chamber, bldg.503) Thursday 4 July 09:15 - 11:00 F. CLOSE Introduction to Particle Physics for non Physics Students (1&2/4) 11:15 - 12:00 C. JORAM Particle Detectors (1/5) Friday 5 July 09:15 - 11:00 F. CLOSE Introduction to Particle Physics for non Physics Students (3&4/4) 11:15 - 12:00 Discussion Session Monday 8 July 09:15 - 10:00 R. KLEISS Fundamental Concepts of Particle Physics (1/6) 10:15 - 11:00 C. JORAM Particle Detectors (2/5) 11:15 - 12:00 M. FRANKLIN Classic Experiments (1/3) 14:00 - 15:00 M. LINDROOS Isolde 15:30 - 16:30 M. LINDROOS Visit of the Experiment Tuesday 9 july 09:15 - 10:00 R. KLEISS Fundamental Concepts of Particle Physics (2/6) 10:15 - 11:00 C. JORAM Part...

  18. Nonradiative recombination due to Ar implantation induced point defects in GaInN/GaN quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Langer, Torsten; Pietscher, Hans-Georg; Joenen, Holger; Rossow, Uwe; Bremers, Heiko; Hangleiter, Andreas [Institut fuer Angewandte Physik, Technische Universitaet Braunschweig (Germany); Menzel, Dirk [Institut fuer Physik der Kondensierten Materie, Technische Universitaet Braunschweig (Germany)

    2013-07-01

    We quantitatively investigate nonradiative recombination at point defects via temperature dependent time-resolved photoluminescence spectroscopy on argon implanted MOVPE-grown GaInN/GaN single quantum wells (QW). An implantation dose dependent (doses: 10{sup 11} cm{sup -2}-10{sup 13} cm{sup -2}) reduction of nonradiative lifetimes from several nanoseconds (unimplanted sample) to less than 100 ps at room temperature is observed. This shortening of nonradiative lifetimes is attributed to nonradiative recombination due to increased implantation induced defect densities. An effective hole capture coefficient can be estimated to about 10{sup 9} cm{sup 3}s{sup -1} via the measured nonradiative lifetimes and simulated (SRIM) defect densities. The thermal stability of the defects is analyzed using rapid thermal annealing at 800 {sup circle} C in order to recover the crystal from implantation damage. At high temperatures, nonradiative recombination in the barriers becomes dominant: defect density dependent losses with an activation energy equal to half the difference between the GaN band gap and the peak position of the QW luminescence are observed.

  19. Optional Student Use of Online Lecture Resources: Resource Preferences, Performance and Lecture Attendance

    Science.gov (United States)

    Grabe, M.; Christopherson, K.

    2008-01-01

    One of the most common uses of a course management system in the on-campus environment is to offer lecture resources to students. Few researchers have investigated how students use such resources. This study considers student use of lecture resources that offer a representation of the lecture presented (i.e. lecture outline, lecture summary, audio…

  20. Source of temperature and pressure pulsations during sessile droplet evaporation into multicomponent atmospheres.

    Science.gov (United States)

    Persad, Aaron H; Sefiane, Khellil; Ward, Charles A

    2013-10-29

    During sessile droplet evaporation, studies with IR thermography and shadowgraphs have indicated temperature pulsations. We confirm those observations with microthermocouples, but microthermocouples also indicate temperature pulsations in the atmosphere of the droplet. The pressure in this atmosphere pulsated as well and was correlated with the temperature pulsations in the droplet. Also, we find that if a droplet evaporates into its own vapor, there are no temperature or pressure pulsations. The pulsations occur only if the droplet evaporates into an atmosphere with a component having a heat of solution with the droplet when it adsorbs-absorbs. None of the currently proposed mechanisms for the temperature pulsations provide an explanation for the coupling between the temperature pulsations in the droplet and the vapor-phase pressure pulsations, and for the absence of the pulsations when the system is single-component. As a mechanism for the pulsations, we propose that when a droplet is exposed to an atmosphere containing a component that has a heat of solution with the droplet, energy will be released from adsorption-absorption. This energy will cause pulsations in the evaporation flux, and these pulsations could cause the observed temperature and pressure pulsations. We examine this mechanism by showing that, if the measured temperature pulsations in a water droplet exposed to a methanol atmosphere are used as the input to a theory of evaporation kinetics (statistical rate theory), the pressure pulsations of the water vapor in the methanol atmosphere are predicted and agree with those measured with a quadrupole mass analyzer. When the inputs and outputs are reversed in the theory, we find that the temperature pulsations in the droplet are correctly predicted from the measured water vapor pulsations in the atmosphere.

  1. Radio Pulsating Structures with Coronal Loop Contraction

    Science.gov (United States)

    Kallunki, J.; Pohjolainen, S.

    2012-10-01

    We present a multi-wavelength study of a solar eruption event on 20 July 2004, comprising observations in Hα, EUV, soft X-rays, and in radio waves with a wide frequency range. The analyzed data show both oscillatory patterns and shock wave signatures during the impulsive phase of the flare. At the same time, large-scale EUV loops located above the active region were observed to contract. Quasi-periodic pulsations with ˜ 10 and ˜ 15 s oscillation periods were detected both in microwave - millimeter waves and in decimeter - meter waves. Our calculations show that MHD oscillations in the large EUV loops - but not likely in the largest contracting loops - could have produced the observed periodicity in radio emission, by triggering periodic magnetic reconnection and accelerating particles. As the plasma emission in decimeter - meter waves traces the accelerated particle beams and the microwave emission shows a typical gyrosynchrotron flux spectrum (emission created by trapped electrons within the flare loop), we find that the particles responsible for the two different types of emission could have been accelerated in the same process. Radio imaging of the pulsed decimetric - metric emission and the shock-generated radio type II burst in the same wavelength range suggest a rather complex scenario for the emission processes and locations. The observed locations cannot be explained by the standard model of flare loops with an erupting plasmoid located above them, driving a shock wave at the CME front.

  2. The evolved pulsating CEMP star HD112869

    CERN Document Server

    Začs, L; Grankina, A; Deveikis, V; Kaminskyi, B; Pavlenko, Y; Musaev, F

    2015-01-01

    Radial velocity measurements, $BVR_C$ photometry, and high-resolution spectroscopy in the wavelength region from blue to near infrared are employed in order to clarify the evolutionary status of the carbon-enhanced metal-poor star HD112869 with unique ratio of carbon isotopes in the atmosphere. An LTE abundance analysis was carried out using the method of spectral synthesis and new self consistent 1D atmospheric models. The radial velocity monitoring confirmed semiregular variations with a peak-to-peak amplitude of about 10 km $s^{-1}$ and a dominating period of about 115 days. The light, color and radial velocity variations are typical of the evolved pulsating stars. The atmosphere of HD112869 appears to be less metal-poor than reported before, [Fe/H] = -2.3 $\\pm$0.2 dex. Carbon to oxygen and carbon isotope ratios are found to be extremely high, C/O $\\simeq$ 12.6 and $^{12}C/^{13}C \\gtrsim$ 1500, respectively. The s-process elements yttrium and barium are not enhanced, but neodymium appears to be overabundan...

  3. KIC 8262223: A Post-mass Transfer Eclipsing Binary Consisting of a Delta Scuti Pulsator and a Helium White Dwarf Precursor

    Science.gov (United States)

    Guo, Zhao; Gies, Douglas R.; Matson, Rachel A.; García Hernández, Antonio; Han, Zhanwen; Chen, Xuefei

    2017-03-01

    KIC 8262223 is an eclipsing binary with a short orbital period (P = 1.61 day). The Kepler light curves are of Algol-type and display deep and partial eclipses, ellipsoidal variations, and pulsations of δ Scuti type. We analyzed the Kepler photometric data, complemented by phase-resolved spectra from the R-C Spectrograph on the 4 meter Mayall telescope at the Kitt Peak National Observatory and determined the fundamental parameters of this system. The low-mass and oversized secondary ({M}2=0.20{M}ȯ , {R}2=1.31{R}ȯ ) is the remnant of the donor star that transferred most of its mass to the gainer, and now the primary star. The current primary star is thus not a normal δ Scuti star but the result of mass accretion from a lower mass progenitor. We discuss the possible evolutionary history and demonstrate with the MESA evolution code that this system and several other systems discussed in prior literature can be understood as the result of non-conservative binary evolution for the formation of EL CVn-type binaries. The pulsations of the primary star can be explained as radial and non-radial pressure modes. The equilibrium models from single star evolutionary tracks can match the observed mass and radius ({M}1=1.94{M}ȯ , {R}1=1.67{R}ȯ ) but the predicted unstable modes associated with these models differ somewhat from those observed. We discuss the need for better theoretical understanding of such post-mass transfer δ Scuti pulsators.

  4. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    Energy Technology Data Exchange (ETDEWEB)

    Córsico, A.H.; Althaus, L.G. [Grupo de Evolución Estelar y Pulsaciones, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, (1900) La Plata (Argentina); Bertolami, M.M. Miller [Instituto de Astrofísica La Plata, CONICET-UNLP, Paseo del Bosque s/n, (1900) La Plata (Argentina); Kepler, S.O. [Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, Porto Alegre 91501-970, RS (Brazil); García-Berro, E., E-mail: acorsico@fcaglp.unlp.edu.ar, E-mail: althaus@fcaglp.unlp.edu.ar, E-mail: marcelo@MPA-Garching.MPG.DE, E-mail: kepler@if.ufrgs.br, E-mail: enrique.garcia-berro@upc.edu [Departament de Física Aplicada, Universitat Politècnica de Catalunya, c/Esteve Terrades 5, 08860, Castelldefels (Spain)

    2014-08-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μ{sub ν}) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pidot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pidot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μ{sub ν} ∼< 10{sup -11} μ{sub B}. This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.

  5. Exploring medical student decisions regarding attending live lectures and using recorded lectures.

    Science.gov (United States)

    Gupta, Anmol; Saks, Norma Susswein

    2013-09-01

    Student decisions about lecture attendance are based on anticipated effect on learning. Factors involved in decision-making, the use of recorded lectures and their effect on lecture attendance, all warrant investigation. This study was designed to identify factors in student decisions to attend live lectures, ways in which students use recorded lectures, and if their use affects live lecture attendance. A total of 213 first (M1) and second year (M2) medical students completed a survey about lecture attendance, and rated factors related to decisions to attend live lectures and to utilize recorded lectures. Responses were analyzed overall and by class year and gender. M1 attended a higher percentage of live lectures than M2, while both classes used the same percentage of recorded lectures. Females attended more live lectures, and used a smaller percentage of recorded lectures. The lecturer was a key in attendance decisions. Also considered were the subject and availability of other learning materials. Students use recorded lectures as replacement for live lectures and as supplement to them. Lectures, both live and recorded, are important for student learning. Decisions about lecture placement in the curriculum need to be based on course content and lecturer quality.

  6. Interpretation of the BRITE oscillation data of the hybrid pulsator ν Eridani: a call for the modification of stellar opacities

    Science.gov (United States)

    Daszyńska-Daszkiewicz, J.; Pamyatnykh, A. A.; Walczak, P.; Colgan, J.; Fontes, C. J.; Kilcrease, D. P.

    2017-04-01

    The analysis of the BRIght Target Explorer (BRITE) oscillation spectrum of the main-sequence early B-type star ν Eridani is presented. Only models with the modified mean opacity profile can account for the observed frequency ranges as well as for the values of some individual frequencies. The number of the κ-modified seismic models is constrained by the non-adiabatic parameter f, which is very sensitive to the opacity changes in the subphotospheric layers, where the pulsations are driven. We present an example of the model that satisfies all the above conditions. It seems that the OPLIB opacities are preferred over those from the OPAL and OP projects. Moreover, we discuss additional consequences of the opacity modification, namely, an enhancement of the efficiency of convection in the Z bump as well as an occurrence of close radial modes which is a kind of avoided-crossing phenomenon common for non-radial modes in standard main-sequence models.

  7. Heartbeat Stars and the Ringing of Tidal Pulsations

    Directory of Open Access Journals (Sweden)

    Hambleton Kelly

    2015-01-01

    Full Text Available With the advent of high precision photometry from satellites such as Kepler and CoRoT, a whole new layer of interesting and astounding astronomical objects has been revealed: heartbeat stars are an example of such objects. Heartbeat stars are eccentric ellipsoidal variables that undergo strong tidal interactions when the stars are almost in contact at the time of closest approach. These interactions deform of the stars and cause a notable light curve variation in the form of a tidal pulse. A subset of these objects (~20% show prominent tidally induced pulsations: pulsations forced by the binary orbit. We now have a fully functional code that models binary star features (using PHOEBE and stellar pulsations simultaneously, enabling a complete and accurate heartbeat star model to be determined. In this paper we show the results of our new code, which uses emcee, a variant of mcmc, to generate a full set of stellar parameters. We further highlight the interesting features of KIC 8164262, including its tidally induced pulsations and resonantly locked pulsations.

  8. Learning from Pulsating Stars: Progress over the Last Century (Abstract)

    Science.gov (United States)

    Smith, H.

    2016-12-01

    (Abstract only) Scarcely more than a century has elapsed since it began to be widely accepted that pulsation plays an important role in the variability of stars. During that century pulsating stars have been used as tools to explore a variety of astrophysical questions, including the determination of distances to other galaxies, the testing of timescales of evolution through the HR diagram, and the identification of the ages and star formation histories of stellar populations. Among the significant early milestones along this investigative path are Henrietta Leavitt's discovery of a relation between the periods and luminosities of Cepheids, Harlow Shapley's proposal that all Cepheids are pulsating stars, and Arthur Stanley Eddington's use of the observed period change of d Cephei to constrain its power source. Today our explorations of pulsating stars are bolstered by long observational histories of brighter variables, surveys involving unprecedentedly large numbers of stars, and improved theoretical analyses. This talk will review aspects of the history and our current understanding of pulsating stars, paying particular attention to RR Lyrae, d Scuti, and Cepheid variables. Observations by AAVSO members have provided insight into several questions regarding the behavior of these stars.

  9. Photometric Survey to Search for Field sdO Pulsators

    CERN Document Server

    Johnson, Christopher B; Wallace, S; O'Malley, C J; Amaya, H; Biddle, L; Fontaine, G

    2013-01-01

    We present the results of a campaign to search for subdwarf O (sdO) star pulsators among bright field stars. The motivation for this project is the recent discovery by Randall et al. (2011), of four rapidly pulsating sdO stars in the globular cluster Omega Cen, with Teff near 50,000 K, 5.4 -0.1 and similar temperatures and gravities. To date, we have found no detectable pulsations at amplitudes above 0.08% (4 times the mean noise level) in any of the 36 field sdO stars that we observed. The presence of pulsations in Omega Cen sdO stars and their apparent absence in seemingly comparable field sdO stars is perplexing. While very suggestive, the significance of this result is difficult to assess more completely right now due to remaining uncertainties about the temperature width and purity of the Omega Cen instability strip and the existence of any sdO pulsators with weaker amplitudes than the current detection limit in globular clusters.

  10. Theoretical rates of pulsation period change in the Galactic Cepheids

    CERN Document Server

    Fadeyev, Yuri A

    2014-01-01

    Theoretical estimates of the rates of radial pulsation period change in Galactic Cepheids with initial masses 5.5M_\\odot <= Mzams <= 13M_\\odot, chemical composition X=0.7, Z=0.02 and periods 1.5 day <= P <= 100 day are obtained from consistent stellar evolution and nonlinear stellar pulsation computations. Pulsational instability was investigated for three crossings of the instability strip by the evolutionary track in the HR diagram. The first crossing occurs at the post-main sequence helium core gravitational contraction stage which proceeds in the Kelvin--Helmholtz timescale whereas the second and the third crossings take place at the evolutionary stage of thermonuclear core helium burning. During each crossing of the instability strip the period of radial pulsations is a quadratic function of the stellar evolution time. Theoretical rates of the pulsation period change agree with observations but the scatter of observational estimates of dP/dt noticeably exceeds the width of the band (\\delta\\lo...

  11. Finding non-eclipsing binaries through pulsational phase modulation

    Science.gov (United States)

    Murphy, Simon J.; Bedding, Timothy R.; Shibahashi, Hiromoto; Kurtz, Donald W.; Kjeldsen, Hans

    2015-09-01

    We present a method for finding binaries among pulsating stars that were observed by the Kepler Mission. We use entire four-year light curves to accurately measure the frequencies of the strongest pulsation modes, then track the pulsation phases at those frequencies in 10-d segments. This produces a series of time-delay measurements in which binarity is apparent as a periodic modulation whose amplitude gives the projected light travel time across the orbit. Fourier analysis of this time-delay curve provides the parameters of the orbit, including the period, eccentricity, angle of ascending node and time of periastron passage. Differentiating the time-delay curve yields the full radial-velocity curve directly from the Kepler photometry, without the need for spectroscopy. We show examples with delta Scuti stars having large numbers of pulsation modes, including one system in which both components of the binary are pulsating. The method is straightforward to automate, thus radial velocity curves can be derived for hundreds of non-eclipsing binary stars from Kepler photometry alone. This contribution is based largely upon the work by Murphy et al. [1], describing the phase-modulation method in detail.

  12. On the polarization properties of magnetar giant flare pulsating tails

    CERN Document Server

    Yang, Yuan-Pei

    2015-01-01

    Three giant flares have been detected so far from soft gamma-ray repeaters, each characterized by an initial short hard spike and a pulsating tail. The observed pulsating tails are characterized by a duration of $\\sim100\\,\\rm{s}$, an isotropic energy of $\\sim 10^{44}\\,\\rm{erg}$, and a pulse period of a few seconds. The pulsating tail emission likely originates from the residual energy after the intense energy release during the initial spike, which forms a trapped fireball composed of a photon-pair plasma in a closed field line region of the magnetars. Observationally the spectra of pulsating tails can be fitted by the superposition of a thermal component and a power-law component, with the thermal component dominating the emission in the early and late stages of the pulsating tail observations. In this paper, assuming that the trapped fireball is from a closed field line region in the magnetosphere, we calculate the atmosphere structure of the optically-thick trapped fireball and the polarization properties ...

  13. Practical strategies for effective lectures.

    Science.gov (United States)

    Lenz, Peter H; McCallister, Jennifer W; Luks, Andrew M; Le, Tao T; Fessler, Henry E

    2015-04-01

    Lecturing is an essential teaching skill for scientists and health care professionals in pulmonary, critical care, and sleep medicine. However, few medical or scientific educators have received training in contemporary techniques or technology for large audience presentation. Interactive lecturing outperforms traditional, passive-style lecturing in educational outcomes, and is being increasingly incorporated into large group presentations. Evidence-based techniques range from the very simple, such as inserting pauses for audience discussion, to more technologically advanced approaches such as electronic audience response systems. Alternative software platforms such as Prezi can overcome some of the visual limits that the ubiquitous PowerPoint imposes on complex scientific narratives, and newer technology formats can help foster the interactive learning environment. Regardless of the technology, adherence to good principles of instructional design, multimedia learning, visualization of quantitative data, and informational public speaking can improve any lecture. The storyline must be clear, logical, and simplified compared with how it might be prepared for scientific publication. Succinct outline and summary slides can provide a roadmap for the audience. Changes of pace, and summaries or other cognitive breaks inserted every 15-20 minutes can renew attention. Graphics that emphasize clear, digestible data graphs or images over tables, and simple, focused tables over text slides, are more readily absorbed. Text slides should minimize words, using simple fonts in colors that contrast to a plain background. Adherence to these well-established principles and addition of some new approaches and technologies will yield an engaging lecture worth attending.

  14. Nonradiative transfer of excitation in coherent decay from a Gaussian atomic distribution

    Energy Technology Data Exchange (ETDEWEB)

    Friedberg, Richard, E-mail: rfriedberg1@nyc.rr.com [Physics Department, Columbia University, NY (United States)

    2011-09-14

    Coherent decay of a spherically symmetric ensemble of initially resonantly phased two-level atoms is studied in the scalar photon model, in the continuum and Markov approximations. Emphasis is on the Gaussian distribution, where nonradiative transfer of excitation to excited states orthogonal to the initial one is found to be nonzero even in the limit of short wavelength, whether or not the scalar kernel exp(ik{sub 0}R)/ik{sub 0}R is replaced by its real part. Numerical results are compared to known values for the uniform distribution.

  15. Nonradiative resonant energy transfer between PbS QDs in porous matrix

    Science.gov (United States)

    Ushakova, Elena V.; Litvin, Aleksandr P.; Parfenov, Peter S.; Fedorov, Anatoly V.; Cherevkov, Sergei A.; Baranov, Alexander V.

    2013-09-01

    Nonradiative fluorescence resonance energy transfer (FRET) between lead sulfide quantum dots (QDs) of two different sizes embedded in porous matrix is observed by a fluorescence spectroscopy. Analysis of decays of photoluminescence from QD mixture shows that energy transfer in studied systems is determined by static quenching, specific for direct contact between QD-donor and QD-acceptor in the QDs close-packed ensembles. From steady-state spectral analysis it was found that efficiency of energy transfer depends on the molar ratio QD-donor/QD-acceptor and energy transfer from the donor to the acceptor passes by several channels.

  16. Correlation of Electrical Noise with Non-radiative Current for High Power QWLs

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The characteristics of low-frequency electrical noise, voltage-current (V-I) and electrical derivation for 980nm InGaAsP/InGaAs/GaAs high power double quantum well lasers(DQWLs) are measured under different conditions. The correlation of the low-frequency electrical noise with surface non-radiative current of devices is discussed. The results indicate the low-frequency electrical noise of 980nm DQWLs with high power is mainly 1/f noise and has good relation with the device surface current at low injection.

  17. Lecture Quiz Extended: An Improvement of the Lecture Quiz Game

    OpenAIRE

    Tran, Long Tien

    2008-01-01

    Lecture Quiz is a game used to provide more active and participant students in lectures. The game is based on a server, a teacher client and a student client. In a master thesis done in 2007, Ole Kristian Mørch-Storstein and Terje Øfsdahl have explored concept of game to be used in higher education and develop a prototype game to further evaluate that concept. Their game has three components; the first one is the server part running on a server. This component connect to a database and provid...

  18. Finding the Instability Strip for Accreting Pulsating White Dwarfs from HST and Optical Observations

    CERN Document Server

    Szkody, Paula; Gansicke, Boris T; Henden, Arne; Templeton, Matthew; Holtzman, Jon; Montgomery, Michael H; Howell, Steve B; Nitta, Atsuko; Sion, Edward M; Schwartz, Richard D; Dillon, William

    2010-01-01

    Time-resolved low resolution Hubble Space Telescope ultraviolet spectra together with ground-based optical photometry and spectra are used to constrain the temperatures and pulsation properties of six cataclysmic variables containing pulsating white dwarfs. Combining our temperature determinations for the five pulsating white dwarfs that are several years past outburst with past results on six other systems shows that the instability strip for accreting pulsating white dwarfs ranges from 10,500-15,000K, a wider range than evident for ZZ Ceti pulsators. Analysis of the UV/optical pulsation properties reveals some puzzling aspects. While half the systems show high pulsation amplitudes in the UV compared to their optical counterparts, others show UV/optical amplitude ratios that are less than one or no pulsations at either wavelength region.

  19. Search for pulsations in the LMXB EXO 0748-676

    Institute of Scientific and Technical Information of China (English)

    Chetana Jain; Biswajit Paul

    2011-01-01

    We present here results from our search for X-ray pulsations of the neutron star in the low mass X-ray binary EXO 0748-676 at a frequency near the burstoscillation frequency of 44.7 Hz.Using the observations made with the Proportional Counter Array onboard the Rossi X-ray Timing Explorer, we did not find any pulsations in the frequency band of 44.4 Hz to 45.0 Hz and obtained a 3σ upper limit of 0.47% on the pulsed fraction for any possible underlying pulsation in this frequency band.We also discuss the importance of EXO 0748-676 as a promising source for the detection of Gravitational Waves.

  20. Prediction of gas pulsation of an industrial compressor

    Institute of Scientific and Technical Information of China (English)

    Heuicheol; Kim; Mi-Gyung; Cho; Jaehong; Park; Cheolho; Bai; Jaesool; Shim

    2013-01-01

    The measurement and prediction of gas pulsations are performed along the discharge pipeline of a reciprocating compressor for a refrigerator. A regression based experimental model of the one-dimensional acoustic field is developed. First, the conventional method for gas pulsation measurement and prediction, which separates the incident and reflected wave of acoustic waves traveling in the frequency domain, is discussed. Then, regression based on our proposed simple model, which is able to predict gas pulsation compared to the conventional method, is introduced for the analysis of a reciprocating compressor(The conventional method requires the value of sound speed in the piping line for the reciprocating compressor). A numerical prediction is made for the regression method. Three power spectrum values along the discharge pipeline are used for analysis, and two values are used for verification. Our results are in a good agreement with the conventional method.

  1. Period Changes and Evolution in Pulsating Variable Stars

    Science.gov (United States)

    Neilson, H. R.; Percy, J. R.; Smith, H. A.

    2016-12-01

    We review ways in which observations of the changing periods of pulsating variable stars can be used to detect and directly measure their evolution. We briefly describe the two main techniques of analysis-(O-C) analysis and wavelet analysis - and results for pulsating variable star types which are reasonably periodic: type I and II Cepheids, RR Lyrae stars, beta Cephei stars, and Mira stars. We comment briefly on delta Scuti stars and pulsating white dwarfs. For some of these variable star types, observations agree approximately with the predictions of evolutionary models, but there still exist significant areas of disagreement that challenge future models of stellar evolution. There may be a need, for instance, to include processes such as rotation, mass loss, and magnetic fields. There may also be non-evolutionary processes which are contributing to the period changes.

  2. Period Changes and Evolution in Pulsating Variable Stars

    CERN Document Server

    Neilson, Hilding R; Smith, Horace A

    2016-01-01

    We review ways in which observations of the changing periods of pulsating variable stars can be used to detect and directly measure their evolution. We briefly describe the two main techniques of analysis -- (O-C) analysis and wavelet analysis -- and results for pulsating variable star types which are reasonably periodic: type I and II Cepheids, RR Lyrae stars, beta Cephei stars, and Mira stars. We comment briefly on delta Scuti stars and pulsating white dwarfs. For some of these variable star types, observations agree approximately with the predictions of evolutionary models, but there still exist significant areas of disagreement that challenge future models of stellar evolution. There may be a need, for instance, to include processes such as rotation, mass loss, and magnetic fields. There may also be non-evolutionary processes which are contributing to the period changes.

  3. Stellar Pulsations, Impact of New Instrumentation and New Insights

    CERN Document Server

    Garrido, R; Balona, L; Christensen-Dalsgaard, J; 20th Stellar Pulsation Conference Series

    2013-01-01

    Analyses of photometric time series obtained from the MOST, CoRoT and Kepler space missions were presented at the 20th conference on Stellar Pulsations (Granada, September 2011). These results are leading to a re-appraisal of our views on stellar pulsation in some stars and posing some new and unexpected challenges. The very important and exciting role played by innovative ground-based observational techniques, such as interferometric measurements of giant pulsating stars and high-resolution spectroscopy in the near infrared, is also discussed. These Proceedings are distinguished by the format of the conference, which brings together a variety of related but different topics not found in other meetings of this nature.

  4. Nonlinear simulations of the convection-pulsation coupling

    CERN Document Server

    Gastine, T

    2011-01-01

    In cold Cepheids close to the red edge of the classical instability strip, a strong coupling between the stellar pulsations and the surface convective motions occurs. This coupling is by now poorly described by 1-D models of convection, the so-called "time-dependent convection models" (TDC). The intrinsic weakness of such models comes from the large number of unconstrained free parameters entering in the description of turbulent convection. A way to overcome these limits is to compute two-dimensional direct simulations (DNS), in which all the nonlinearities are correctly solved. Two-dimensional DNS of the convection-pulsation coupling are presented here. In an appropriate parameter regime, convective motions can actually quench the radial pulsations of the star, as suspected in Cepheids close to the red edge of the instability strip. These nonlinear simulations can also be used to determine the limits and the relevance of the TDC models.

  5. On the pulsation modes and masses of RGB OSARGs

    Directory of Open Access Journals (Sweden)

    Saio H.

    2013-03-01

    Full Text Available OSARG (OGLE Small Amplitude Red Giants variables are RGB or AGB stars that show multi-periodic light variations with periods of about 10-100 days. Comparing linear nonadiabatic pulsation periods and period ratios with observed ones, we determined pulsation modes and masses of the RGB OSARG variables in the LMC. We found that pulsations of OSARGs involve radial 1st to 3rd overtones, p4 of l = 1, and p2 of l = 2 modes. The range of mass isfound to be 0.9-1.4M⊙ for RGB OSARGs and their mass-luminosity relation is logL/L⊙ = 0.79 M/M⊙ + 2.2.

  6. Finding the First Cosmic Explosions. III. Pair-Pulsational Supernovae

    CERN Document Server

    Whalen, Daniel J; Even, Wesley; Woosley, S E; Heger, Alexander; Stiavelli, Massimo; Fryer, Chris L

    2013-01-01

    Population III supernovae have been the focus of growing attention because of their potential to directly probe the properties of the first stars, particularly the most energetic events that can be seen at the edge of the observable universe. But until now pair-pulsation supernovae, in which explosive thermonuclear burning in massive stars fails to unbind them but can eject their outer layers into space, have been overlooked as cosmic beacons at the earliest redshifts. These shells can later collide and, like Type IIn supernovae, produce superluminous events in the UV at high redshifts that could be detected in the near infrared today. We present numerical simulations of a 110 M$_{\\odot}$ pair-pulsation explosion done with the Los Alamos radiation hydrodynamics code RAGE. We find that collisions between consecutive pair pulsations are visible in the near infrared out to z $\\sim$ 15 - 20 and can probe the earliest stellar populations at cosmic dawn.

  7. Outbursts in Two New Cool Pulsating DA White Dwarfs

    Science.gov (United States)

    Bell, Keaton J.; Hermes, J. J.; Montgomery, M. H.; Gentile Fusillo, N. P.; Raddi, R.; Gänsicke, B. T.; Winget, D. E.; Dennihy, E.; Gianninas, A.; Tremblay, P.-E.; Chote, P.; Winget, K. I.

    2016-10-01

    The unprecedented extent of coverage provided by Kepler observations recently revealed outbursts in two hydrogen-atmosphere pulsating white dwarfs (DAVs) that cause hours-long increases in the overall mean flux of up to 14%. We have identified two new outbursting pulsating white dwarfs in K2, bringing the total number of known outbursting white dwarfs to four. EPIC 211629697, with {T}{eff} = 10,780 ± 140 K and {log} g = 7.94 ± 0.08, shows outbursts recurring on average every 5.0 days, increasing the overall flux by up to 15%. EPIC 229227292, with {T}{eff} = 11,190 ± 170 K and {log} g = 8.02 ± 0.05, has outbursts that recur roughly every 2.4 days with amplitudes up to 9%. We establish that only the coolest pulsating white dwarfs within a small temperature range near the cool, red edge of the DAV instability strip exhibit these outbursts.

  8. Lectures on Conformal Field Theory

    CERN Document Server

    Qualls, Joshua D

    2015-01-01

    These lectures notes are based on courses given at National Taiwan University, National Chiao-Tung University, and National Tsing Hua University in the spring term of 2015. Although the course was offered primarily for graduate students, these lecture notes have been prepared for a more general audience. They are intended as an introduction to conformal field theories in various dimensions, with applications related to topics of particular interest: topics include the conformal bootstrap program, boundary conformal field theory, and applications related to the AdS/CFT correspondence. We assume the reader to be familiar with quantum mechanics at the graduate level and to have some basic knowledge of quantum field theory. Familiarity with string theory is not a prerequisite for this lectures, although it can only help.

  9. "Don't Lecture Me"

    Science.gov (United States)

    2011-11-01

    Often I will listen to public radio on long drives when I am alone. Recently I happened to catch a program called "Don't Lecture Me" and it really caught my attention for several reasons. First, the speakers were all notable leaders in Physics Education Research such as Joe Redish, David Hestenes, and Eric Mazur. (See this month's WebSights column.) These folks are among many who have devoted their energies to understanding how students learn physics and how teachers can design classroom instruction and interactions to best meet the needs of learners. Second, on this particular trip, I had just observed a teacher whose class was very teacher-centered as the teacher lectured most of the class period. As we discussed this later, she expressed concern that she had to cover the material and didn't feel that she could do it without lecturing.

  10. ``Don't Lecture Me''

    Science.gov (United States)

    Blanton, Patricia

    2011-11-01

    Often I will listen to public radio on long drives when I am alone. Recently I happened to catch a program called ``Don't Lecture Me'' and it really caught my attention for several reasons. First, the speakers were all notable leaders in Physics Education Research such as Joe Redish, David Hestenes, and Eric Mazur. (See this month's WebSights column.) These folks are among many who have devoted their energies to understanding how students learn physics and how teachers can design classroom instruction and interactions to best meet the needs of learners. Second, on this particular trip, I had just observed a teacher whose class was very teacher-centered as the teacher lectured most of the class period. As we discussed this later, she expressed concern that she had to cover the material and didn't feel that she could do it without lecturing.

  11. Articulated pipes conveying fluid pulsating with high frequency

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard

    1999-01-01

    Stability and nonlinear dynamics of two articulated pipes conveying fluid with a high-frequency pulsating component is investigated. The non-autonomous model equations are converted into autonomous equations by approximating the fast excitation terms with slowly varying terms. The downward hanging...... pipe position will lose stability if the mean flow speed exceeds a certain critical value. Adding a pulsating component to the fluid flow is shown to stabilize the hanging position for high values of the ratio between fluid and pipe-mass, and to marginally destabilize this position for low ratios...

  12. Flame fronts in Supernovae Ia and their pulsational stability

    CERN Document Server

    Glazyrin, S I; Dolgov, A D

    2013-01-01

    The structure of the deflagration burning front in type Ia supernovae is considered. The parameters of the flame are obtained: its normal velocity and thickness. The results are in good agreement with previous work of different authors. After that the question of pulsational instability of the flame subject to plane perturbations is considered. The flame can be unstable if hydrodynamics can be ignored, e.g. in solid-body propellants. However, with account of hydrodynamics we find that the flame in type Ia supernovae is pulsationally stable with realistic parameters of reactions and thermal conduction.

  13. Cycles of self-pulsations in a photonic integrated circuit.

    Science.gov (United States)

    Karsaklian Dal Bosco, Andreas; Kanno, Kazutaka; Uchida, Atsushi; Sciamanna, Marc; Harayama, Takahisa; Yoshimura, Kazuyuki

    2015-12-01

    We report experimentally on the bifurcation cascade leading to the appearance of self-pulsation in a photonic integrated circuit in which a laser diode is subjected to delayed optical feedback. We study the evolution of the self-pulsing frequency with the increase of both the feedback strength and the injection current. Experimental observations show good qualitative accordance with numerical results carried out with the Lang-Kobayashi rate equation model. We explain the mechanism underlying the self-pulsations by a phenomenon of beating between successive pairs of external cavity modes and antimodes.

  14. Search for Optical Pulsations in PSR J0337+1715

    CERN Document Server

    Strader, M J; Meeker, S R; Szypryt, P; Walter, A B; van Eyken, J C; Ulbricht, G; Stoughton, C; Bumble, B; Kaplan, D L; Mazin, B A

    2016-01-01

    We report on a search for optical pulsations from PSR J0337+1715 at its observed radio pulse period. PSR J0337+1715 is a millisecond pulsar (2.7 ms spin period) in a triple hierarchical system with two white dwarfs, and has a known optical counterpart with g-band magnitude 18. The observations were done with the Array Camera for Optical to Near-IR Spectrophotometry (ARCONS) at the 200" Hale telescope at Palomar Observatory. No significant pulsations were found in the range 4000-11000 angstroms, and we can limit pulsed emission in g-band to be fainter than 25 mag.

  15. Eight lectures on theoretical physics

    CERN Document Server

    Planck, Max

    1997-01-01

    In 1909 the great German physicist and Nobel Prize winner Max Planck (1858-1947) delivered a series of eight lectures at Columbia University giving a fascinating overview of the new state of physics, which he had played a crucial role in bringing about. The first, third, fifth, and sixth lectures present his account of the revolutionary developments occasioned when he first applied the quantum hypothesis to blackbody radiation. The reader is given an invaluable opportunity to witness Planck's thought processes both on the level of philosophical principles as well as their application to physi

  16. Displacement ventilation in lecture halls

    OpenAIRE

    Egorov, Artem

    2013-01-01

    This thesis considers several important goals. The main purpose is to see how displacement ventilation sys-tem works in the lecture hall of M-building and compare obtained results with D2 and Indoor Climate Classi-fication. The second one is to analyze the function of the ventilation system. The last one is to realize when displacement ventilation is preferable to mixing ventilation. Analysis of the system was carried out with instruments from MUAS HVAC laboratory. In lecture hall were me...

  17. TASI Lectures on Flavor Physics

    CERN Document Server

    Ligeti, Zoltan

    2015-01-01

    These notes overlap with lectures given at the TASI summer schools in 2014 and 2011, as well as at the European School of High Energy Physics in 2013. This is primarily an attempt at transcribing my hand-written notes, with emphasis on topics and ideas discussed in the lectures. It is not a comprehensive introduction or review of the field, nor does it include a complete list of references. I hope, however, that someone may find it useful to better understand the reasons for excitement about recent progress and future opportunities in flavor physics.

  18. TASI Lectures on Flavor Physics

    Science.gov (United States)

    Ligeti, Zoltan

    These notes overlap with lectures given at the TASI summer schools in 2014 and 2011, as well as at the European School of High Energy Physics in 2013. This is primarily an attempt at transcribing my handwritten notes, with emphasis on topics and ideas discussed in the lectures. It is not a comprehensive introduction or review of the field, nor does it include a complete list of references. I hope, however, that some may find it useful to better understand the reasons for excitement about recent progress and future opportunities in flavor physics.

  19. A Non-radial Eruption in a Quadrupolar Magnetic Configuration with a Coronal Null

    Science.gov (United States)

    Sun, Xudong; Hoeksema, J. Todd; Liu, Yang; Chen, Qingrong; Hayashi, Keiji

    2012-10-01

    We report one of the several homologous non-radial eruptions from NOAA active region (AR) 11158 that are strongly modulated by the local magnetic field as observed with the Solar Dynamic Observatory. A small bipole emerged in the sunspot complex and subsequently created a quadrupolar flux system. Nonlinear force-free field extrapolation from vector magnetograms reveals its energetic nature: the fast-shearing bipole accumulated ~2 × 1031 erg free energy (10% of AR total) over just one day despite its relatively small magnetic flux (5% of AR total). During the eruption, the ejected plasma followed a highly inclined trajectory, over 60° with respect to the radial direction, forming a jet-like, inverted-Y-shaped structure in its wake. Field extrapolation suggests complicated magnetic connectivity with a coronal null point, which is favorable of reconnection between different flux components in the quadrupolar system. Indeed, multiple pairs of flare ribbons brightened simultaneously, and coronal reconnection signatures appeared near the inferred null. Part of the magnetic setting resembles that of a blowout-type jet; the observed inverted-Y structure likely outlines the open field lines along the separatrix surface. Owing to the asymmetrical photospheric flux distribution, the confining magnetic pressure decreases much faster horizontally than upward. This special field geometry likely guided the non-radial eruption during its initial stage.

  20. A NON-RADIAL ERUPTION IN A QUADRUPOLAR MAGNETIC CONFIGURATION WITH A CORONAL NULL

    Energy Technology Data Exchange (ETDEWEB)

    Sun Xudong; Hoeksema, J. Todd; Liu Yang; Hayashi, Keiji [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Chen Qingrong, E-mail: xudong@sun.stanford.edu [Department of Physics, Stanford University, Stanford, CA 94305 (United States)

    2012-10-01

    We report one of the several homologous non-radial eruptions from NOAA active region (AR) 11158 that are strongly modulated by the local magnetic field as observed with the Solar Dynamic Observatory. A small bipole emerged in the sunspot complex and subsequently created a quadrupolar flux system. Nonlinear force-free field extrapolation from vector magnetograms reveals its energetic nature: the fast-shearing bipole accumulated {approx}2 Multiplication-Sign 10{sup 31} erg free energy (10% of AR total) over just one day despite its relatively small magnetic flux (5% of AR total). During the eruption, the ejected plasma followed a highly inclined trajectory, over 60 Degree-Sign with respect to the radial direction, forming a jet-like, inverted-Y-shaped structure in its wake. Field extrapolation suggests complicated magnetic connectivity with a coronal null point, which is favorable of reconnection between different flux components in the quadrupolar system. Indeed, multiple pairs of flare ribbons brightened simultaneously, and coronal reconnection signatures appeared near the inferred null. Part of the magnetic setting resembles that of a blowout-type jet; the observed inverted-Y structure likely outlines the open field lines along the separatrix surface. Owing to the asymmetrical photospheric flux distribution, the confining magnetic pressure decreases much faster horizontally than upward. This special field geometry likely guided the non-radial eruption during its initial stage.

  1. Fluorescence and Nonradiative Properties of Nd3+ in Novel Heavy Metal Contained Fluorophosphate Glass

    Directory of Open Access Journals (Sweden)

    Ju H. Choi

    2007-01-01

    Full Text Available We demonstrate new series of heavy metal containing fluorophosphate glass system. The fluorescence and nonradiative properties of Nd3+ ions are investigated as a function of Nd2O3 concentration. The variation of intensity parameters Ω2, Ω4, and Ω6 is determined from absorption spectra. The spontaneous probability (A and branching ratio (β are determined using intensity parameters. The emission cross sections for the 4F3/2→4I13/2 transition, which is calculated by Fuchtbabauer-Ladenburg method, decrease from 6.1×10−21 to 3.0×10−21(pm2 and those for the 4F3/2→4I11/2 transition decrease from 3.51×10−20 to 1.7×10−20 as Nd2O3 concentration increase up to 3 wt%. The nonradiative relaxation is analyzed in terms of multiphonon relaxation and concentration quenching due to energy transfer among Nd3+ ions. Finally, the above results obtained at 1 wt %Nd2O3 are compared with some of reported laser host glasses which indicated the potentials for broadband-amplifiers and high-power laser applications.

  2. nIFTy galaxy cluster simulations - I. Dark matter and non-radiative models

    Science.gov (United States)

    Sembolini, Federico; Yepes, Gustavo; Pearce, Frazer R.; Knebe, Alexander; Kay, Scott T.; Power, Chris; Cui, Weiguang; Beck, Alexander M.; Borgani, Stefano; Dalla Vecchia, Claudio; Davé, Romeel; Elahi, Pascal Jahan; February, Sean; Huang, Shuiyao; Hobbs, Alex; Katz, Neal; Lau, Erwin; McCarthy, Ian G.; Murante, Guiseppe; Nagai, Daisuke; Nelson, Kaylea; Newton, Richard D. A.; Perret, Valentin; Puchwein, Ewald; Read, Justin I.; Saro, Alexandro; Schaye, Joop; Teyssier, Romain; Thacker, Robert J.

    2016-04-01

    We have simulated the formation of a galaxy cluster in a Λ cold dark matter universe using 13 different codes modelling only gravity and non-radiative hydrodynamics (RAMSES, ART, AREPO, HYDRA and nine incarnations of GADGET). This range of codes includes particle-based, moving and fixed mesh codes as well as both Eulerian and Lagrangian fluid schemes. The various GADGET implementations span classic and modern smoothed particle hydrodynamics (SPH) schemes. The goal of this comparison is to assess the reliability of cosmological hydrodynamical simulations of clusters in the simplest astrophysically relevant case, that in which the gas is assumed to be non-radiative. We compare images of the cluster at z = 0, global properties such as mass and radial profiles of various dynamical and thermodynamical quantities. The underlying gravitational framework can be aligned very accurately for all the codes allowing a detailed investigation of the differences that develop due to the various gas physics implementations employed. As expected, the mesh-based codes RAMSES, ART and AREPO form extended entropy cores in the gas with rising central gas temperatures. Those codes employing classic SPH schemes show falling entropy profiles all the way into the very centre with correspondingly rising density profiles and central temperature inversions. We show that methods with modern SPH schemes that allow entropy mixing span the range between these two extremes and the latest SPH variants produce gas entropy profiles that are essentially indistinguishable from those obtained with grid-based methods.

  3. Nonradiating and radiating modes excited by quantum emitters in open epsilon-near-zero cavities.

    Science.gov (United States)

    Liberal, Iñigo; Engheta, Nader

    2016-10-01

    Controlling the emission and interaction properties of quantum emitters (QEs) embedded within an optical cavity is a key technique in engineering light-matter interactions at the nanoscale, as well as in the development of quantum information processing. State-of-the-art optical cavities are based on high quality factor photonic crystals and dielectric resonators. However, wealthier responses might be attainable with cavities carved in more exotic materials. We theoretically investigate the emission and interaction properties of QEs embedded in open epsilon-near-zero (ENZ) cavities. Using analytical methods and numerical simulations, we demonstrate that open ENZ cavities present the unique property of supporting nonradiating modes independently of the geometry of the external boundary of the cavity (shape, size, topology, etc.). Moreover, the possibility of switching between radiating and nonradiating modes enables a dynamic control of the emission by, and the interaction between, QEs. These phenomena provide unprecedented degrees of freedom in controlling and trapping fields within optical cavities, as well as in the design of cavity opto- and acoustomechanical systems.

  4. Green Development Performance in China: A Metafrontier Non-Radial Approach

    Directory of Open Access Journals (Sweden)

    Ke Li

    2016-03-01

    Full Text Available This paper proposes a green development growth index (GDGI for measuring the changes in sustainable development over time. This index considers a wide range of pollutants, and allows for the incorporation of group heterogeneity and non-radial slack in the conventional green development index. The GDGI is calculated based on a non-radial directional distance function derived by several data envelopment analysis (DEA models, and was decomposed into an efficiency change (EC index, a best-practice gap change (BPC index and a technology gap change (TGC index. The proposed indices are employed to measure green development performance in 30 provinces in China from 2000 to 2012. The empirical results show that China has a low level of green development, with a 2.58% increase per year driven by an innovation effect. China’s green development is mainly led by the eastern region, and the technology gaps between the eastern region and the other two regions (the central and western regions have become wider over the years. The group innovative provinces have set a target for resource utilization of non-innovative provinces in order to catch-up with the corresponding groups, while the metafrontier innovative provinces provide targets for the technology levels of other provinces to improve their green development performance.

  5. Videotaped Lectures in a Graduate Cytogenetics Course.

    Science.gov (United States)

    Phillips, R. L.; Jellen, E. N.

    1994-01-01

    Graduate students evaluated the use of videotape recordings of lectures on chromosome configurations in a cytogenetics course. Ninety-two percent of the students indicated that videotaping was worthwhile. Advantages for using the videotaped cytogenetics lectures are presented. (MDH)

  6. Carrier density dependence of plasmon-enhanced nonradiative energy transfer in a hybrid quantum well-quantum dot structure.

    Science.gov (United States)

    Higgins, L J; Karanikolas, V D; Marocico, C A; Bell, A P; Sadler, T C; Parbrook, P J; Bradley, A L

    2015-01-26

    An array of Ag nanoboxes fabricated by helium-ion lithography is used to demonstrate plasmon-enhanced nonradiative energy transfer in a hybrid quantum well-quantum dot structure. The nonradiative energy transfer, from an InGaN/GaN quantum well to CdSe/ZnS nanocrystal quantum dots embedded in an ~80 nm layer of PMMA, is investigated over a range of carrier densities within the quantum well. The plasmon-enhanced energy transfer efficiency is found to be independent of the carrier density, with an efficiency of 25% reported. The dependence on carrier density is observed to be the same as for conventional nonradiative energy transfer. The plasmon-coupled energy transfer enhances the QD emission by 58%. However, due to photoluminescence quenching effects an overall increase in the QD emission of 16% is observed.

  7. Spectroscopic analyses of subluminous B stars: observational constraints for the theory of stellar evolution, pulsation, and diffusion

    Science.gov (United States)

    Edelmann, Heinz

    2003-06-01

    This thesis deals with quantitative spectroscopic analyses of large samples of subluminous B stars in order to find constraints the theory of stellar evolution, pulsation, and diffusion. Subluminous B stars, also known as subdwarf B (sdB) stars, are very important in several respects: They dominate the population of faint blue stars in high galactic latitudes, and are found both in the field and in globular clusters. Therefore, sdB stars are important to understand the structure and evolution of our galaxy. From the cosmological point of view, they are candidate progenitors of supernovae of type Ia due to their membership in close binary systems. In the context of stellar astrophysics, subdwarf B stars play an important role because several of them are discovered to show non-radial pulsations, which allows to probe their interior by asteroseismology. Last but not least, sdB stars show very peculiar element abundance patterns, probably caused by diffusion processes. Subluminous B stars are generally considered to be core helium-burning stars with extremely thin hydrogen envelopes (clarified. Recently, several sdB stars have been found to show non-radial pulsations. We initiated a collaboration with two groups in Norway and Italy in 1999 to search for pulsating sdB stars in our sample. About one pulsator within ten observed sdB stars were found. With this discovery we enhanced the number of known pulsating sdB stars by about 50%. The surface metal abundance patterns of 16 sdB stars have been determined from high resolution, high S/N, optical spectra using equivalent widths measurements. This analysis almost quadruples the number of detailed metal abundance analyses of sdB stars. As typical for early B type stars, the metal lines are few and very weak. Three peculiar sdB stars have been found which show in addition to the absorption lines common in sdB stars many lines due to iron group elements (calcium, scandium, titanium, vanadium, manganese, and nickel) which have

  8. TASI Lectures on Jet Substructure

    CERN Document Server

    Shelton, Jessie

    2013-01-01

    Jet physics is a rich and rapidly evolving field, with many applications to physics in and beyond the Standard Model. These notes, based on lectures delivered at the June 2012 Theoretical Advanced Study Institute, provide an introduction to jets at the Large Hadron Collider. Topics covered include sequential jet algorithms, jet shapes, jet grooming, and boosted Higgs and top tagging.

  9. Koshiba, Tanaka give Nobel lectures

    CERN Multimedia

    2002-01-01

    Masatoshi Kosiba and Koichi Tanaka presented lectures in English on Sunday, touching on topics ranging from particle physics, to teamwork to commemorate their reception of this year's Nobel Prize for Physics and Chemistry. The two will receive their respective prizes in an awards ceremony scheduled for Tuesday (1 page).

  10. Six Lectures on Commutative Algebra

    CERN Document Server

    Elias, J; Miro-Roig, Rosa Maria; Zarzuela, Santiago

    2009-01-01

    Interest in commutative algebra has surged over the years. In order to survey and highlight the developments in this rapidly expanding field, the Centre de Recerca Matematica in Bellaterra organized a ten-days Summer School on Commutative Algebra in 1996. This title offers a synthesis of the lectures presented at the Summer School

  11. Applied Fluid Mechanics. Lecture Notes.

    Science.gov (United States)

    Gregg, Newton D.

    This set of lecture notes is used as a supplemental text for the teaching of fluid dynamics, as one component of a thermodynamics course for engineering technologists. The major text for the course covered basic fluids concepts such as pressure, mass flow, and specific weight. The objective of this document was to present additional fluids…

  12. TASI lectures on complex structures

    CERN Document Server

    Denef, Frederik

    2011-01-01

    These lecture notes give an introduction to a number of ideas and methods that have been useful in the study of complex systems ranging from spin glasses to D-branes on Calabi-Yau manifolds. Topics include the replica formalism, Parisi's solution of the Sherrington-Kirkpatrick model, overlap order parameters, supersymmetric quantum mechanics, D-brane landscapes and their black hole duals.

  13. TASI Lectures on Complex Structures

    Science.gov (United States)

    Denef, Frederik

    2012-11-01

    These lecture notes give an introduction to a number of ideas and methods that have been useful in the study of complex systems ranging from spin glasses to D-branes on Calabi-Yau manifolds. Topics include the replica formalism, Parisi's solution of the Sherrington-Kirkpatrick model, overlap order parameters, supersymmetric quantum mechanics, D-brane landscapes and their black hole duals.

  14. Applied Fluid Mechanics. Lecture Notes.

    Science.gov (United States)

    Gregg, Newton D.

    This set of lecture notes is used as a supplemental text for the teaching of fluid dynamics, as one component of a thermodynamics course for engineering technologists. The major text for the course covered basic fluids concepts such as pressure, mass flow, and specific weight. The objective of this document was to present additional fluids…

  15. Embedding Laboratory Experience in Lectures

    Science.gov (United States)

    Morgan, James R.; Barroso, Luciana R.; Simpson, Nancy

    2009-01-01

    Demonstrations can be very effective at enhancing student learning and represent a mechanism for embedding laboratory experiences within a classroom setting. A key component to an effective demonstration is active student engagement throughout the entire process, leading to a guided laboratory experience in a lecture setting. Students are involved…

  16. College Students' Perception of Lecturers Using Humor.

    Science.gov (United States)

    Tamborini, Ron; Zillmann, Dolf

    1981-01-01

    Audio-taped lectures by male or female professors were produced in four versions: no humor; sexual humor; other-disparaging humor; and self-disparaging humor. Male and female students rated lecturers' intelligence and appeal. Intelligence ratings were unaffected by humor variations, but significant lecturer-student sex interactions were found on…

  17. Interactive Lecture Discourse for University EFL Students

    Science.gov (United States)

    Morell, Teresa

    2004-01-01

    Interactive lectures play an important role in improving comprehension and in enhancing communicative competence in the English language for EFL university students taking content lecture courses. This article considers the interactive discourse in lectures of the English Studies Department at the University of Alicante, Spain. It describes an…

  18. Clickers and Formative Feedback at University Lectures

    Science.gov (United States)

    Egelandsdal, Kjetil; Krumsvik, Rune Johan

    2017-01-01

    Lecturing is often criticized for being a monological and student passive way of teaching. However, digital technology such as Student Response Systems (SRS) can be used to reconstruct the traditional lecturing format. During a series of five two-hour lectures in "qualitative methods" for first year psychology students, we used SRS to…

  19. Transformerless photovoltaic inverters with leakage current and pulsating power elimination

    DEFF Research Database (Denmark)

    Tang, Yi; Yao, Wenli; Wang, H.;

    2015-01-01

    that is inherent in single-phase PV systems. By properly injecting CM voltages to the output filter capacitors, the pulsating power can be decoupled from the dc-link. Therefore, it is possible to use long lifetime film capacitors instead of electrolytic capacitors to improve the reliability of the PV system...

  20. The triple-mode pulsating variable V823 Cassiopeiae

    Science.gov (United States)

    Jurcsik, J.; Szeidl, B.; Váradi, M.; Henden, A.; Hurta, Zs.; Lakatos, B.; Posztobányi, K.; Klagyivik, P.; Sódor, Á.

    2006-01-01

    Using extended multicolour CCD photometry of the triple-mode radial pulsator V823 Cas we studied the properties of the coupling frequencies invoked by nonlinear processes. Our results support that a resonance connection affects the mode coupling behaviour. The P1/P0 period ratio of V823 Cas has an “out of range” value if compared with the period ratios of the known double mode pulsators, while the P2/P1 period ratio is normal. The periods and period ratios cannot be consistently interpreted without conflict with pulsation and/or evolution models. We describe this failure with the suggestion that at present, the periods of V823 Cas are in a transient, resonance affected state, thus do not reflect the true parameters of the object. The anomalous period change behaviour of the fundamental and second overtone modes supports this idea. We have also raised the possibility that a f0 +f2 = 2f1 resonance may act in triple mode pulsators.

  1. EXOTIME: searching for planets around pulsating subdwarf B stars

    CERN Document Server

    Schuh, Sonja; Lutz, Ronny; Loeptien, Bjoern; Green, Elizabeth M; Ostensen, Roy H; Leccia, Silvio; Kim, Seung-Lee; Fontaine, Gilles; Charpinet, Stephane; Francoeur, Myriam; Randall, Suzanna; Rodriguez-Lopez, Cristina; van Grootel, Valerie; Odell, Andrew P; Paparo, Margit; Bognar, Zsofia; Papics, Peter; Nagel, Thorsten; Beeck, Benjamin; Hundertmark, Markus; Stahn, Thorsten; Dreizler, Stefan; Hessman, Frederic V; Dall'Ora, Massimo; Mancini, Dario; Cortecchia, Fausto; Benatti, Serena; Claudi, Riccardo; Janulis, Rimvydas; 10.1007/s10509-010-0356-4

    2010-01-01

    In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undiscovered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendipitous discovery, the EXOTIME (http://www.na.astro.it/~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pulsating subdwarf B stars on time-scales of several years with two immediate observational goals: 1) determine Pdot of the pulsational periods P 2) search for signatures of substellar companions in O-C residuals due to periodic light travel time variations, which would be tracking the central star's companion-induced wobble around the center of mass. These sets of data should therefore at the same time: on the one hand be useful to provide extra constraints for classical asteroseismological exercises from the Pdot (comparison with "local" evolutionary models), and on the othe...

  2. M dwarf search for pulsations within Kepler GO program

    CERN Document Server

    Rodríguez-López, C; MacDonald, J; Amado, P J; Carosso, A

    2014-01-01

    We present the analysis of four M dwarf stars -plus one M giant that seeped past our selection criteria- observed in Cycle 3 of Kepler Guest Observer program (GO3) in a search for intrinsic pulsations. Stellar oscillations in M dwarfs were theoretically predicted by Rodr\\'iguez-L\\'opez et al. (2012) to be in the range ~20-40 min and ~4-8 h, depending on the age and the excitation mechanism. We requested Kepler short cadence observations to have an adequate sampling of the oscillations. The targets were chosen on the basis of detectable rotation in the initial Kepler results, biasing towards youth.The analysis reveals no oscillations attributable to pulsations at a detection limit of several parts per million, showing that either the driving mechanisms are not efficient in developing the oscillations to observable amplitudes, or that if pulsations are driven, the amplitudes are very low. The size of the sample, and the possibility that the instability strip is not pure, allowing the coexistence of pulsators an...

  3. Experimental and numerical study of pulsating transversal jets

    Science.gov (United States)

    Goldfeld, M. A.; Fedorova, N. N.; Fedorchenko, I. A.; Pozdnyakov, G. A.; Timofeev, K. Yu.; Zhakharova, Yu. V.

    2015-06-01

    Paper presents results of joint experimental and numerical investigation of pulsating jet penetration into still air and supersonic flow. Goal of the study is to investigate two-dimensional (2D) Hartmann generator (HG) properties and clear up its possibilities in providing better mixing between air and secondary (injected) gases.

  4. Solar Microwave and Geomagnetic Field Pulsations as Space Weather Factors

    Science.gov (United States)

    Snegirev, S. D.; Fridman, V. M.; Sheiner, O. A.

    The procedure of short-term prediction of main solar flares was created on the basis of temporal behavior of long-period microwave pulsations [Kobrin et al., 1997]. At the same time it was shown that before these flares one could observe long-period (T > 20 min) pulsations of geomagnetic field [Kobrin et al, 1985]. The resemblance between microwave and geomagnetic pulsations (duration and temporal behaviour) allows us to propose the common nature of these variations: the reflection of solar energy accumulation and instabilities in solar centers of activity. To be an important factor of Space Weather above mentioned pulsations can be useful for constructing the procedures to predict the near Earth's conditions. This work was supported by the Russian Foundation for Fundamental Research and Russian Federal Programm "Astronomy" (grant N 1.5.5.5). Kobrin M.M, Malygin V.I., Snegirev S.D. Plan. Space Sci., 33, N11, p. 1251 (1985). Kobrin M.M., Pakhomov V.V., Snegirev S.D., Fridman V.M., Sheiner O.A. Proc. Workshop `STPW-96', Tokyo: RCW, p. 200 (1997).

  5. Pressure pulsations in reciprocating pump piping systems Part 1: Modelling

    CERN Document Server

    Shu, Jian-Jun; Edge, Kevin A

    2014-01-01

    A distributed parameter model of pipeline transmission line behaviour is presented, based on a Galerkin method incorporating frequency-dependent friction. This is readily interfaced to an existing model of the pumping dynamics of a plunger pump to allow time-domain simulations of pipeline pressure pulsations in both suction and delivery lines. A new model for the pump inlet manifold is also proposed.

  6. The triple-mode pulsating variable V823 Cas

    CERN Document Server

    Jurcsik, J; Varadi, M; Henden, A; Hurta, Z; Lakatos, B; Posztobanyi, K; Klagyivik, P; Sodor, A; Hurta, Zs.

    2005-01-01

    Based on extended multicolour CCD photometry of the triple-mode radial pulsator V823 Cas we studied the properties of the coupling frequencies invoked by nonlinear processes. Our results support that a resonance connection as suggested by Antonello & Aikawa (1998) affects the mode coupling behaviour. The P1/P0 period ratio of V823 Cas has an "out of range" value if compared with the period ratios of the known double mode pulsators, while the P2/P1 period ratio is normal. The periods and period ratios cannot be consistently interpret without conflict with pulsation and/or evolution models. We attempt to interpret this failure by the suggestion that at present, the periods of V823 Cas are in a transient, resonance affected state, thus do not reflect the true parameters of the object. The anomalous period change behaviour of the fundamental and second overtone modes supports this idea. We have also raised the possibility that a f0 + f2 = 2f1 resonance may act in triple mode pulsators.

  7. First Kepler results on compact pulsators VI. Targets in the final half of the survey phase

    DEFF Research Database (Denmark)

    H. Østensen, R.; Silvotti, R.; Charpinet, S.;

    2011-01-01

    We present results from the final six months of a survey to search for pulsations in white dwarfs and hot subdwarf stars with the Kepler spacecraft. Spectroscopic observations are used to separate the objects into accurate classes, and we explore the physical parameters of the subdwarf B (sd....... No V361 Hya type of short-period pulsating sdB stars were found in this half, leaving us with a total of one single multiperiodic V361 Hya and 13 V1093 Her pulsators for the full survey. Except for the sdB pulsators, no other clearly pulsating hot subdwarfs or white dwarfs were found, although a few...

  8. Global well-posedness and scattering for the focusing nonlinear Schrödinger equation in the nonradial case

    Directory of Open Access Journals (Sweden)

    Pigong Han

    2012-01-01

    Full Text Available The energy-critical, focusing nonlinear Schrödinger equation in the nonradial case reads as follows: \\[i\\partial_t u = -\\Delta u -|u|^{\\frac{4}{N-2}}u,\\quad (x,0=u_0 \\in H^1 (\\mathbb{R}^N,\\quad N\\geq 3.\\] Under a suitable assumption on the maximal strong solution, using a compactness argument and a virial identity, we establish the global well-posedness and scattering in the nonradial case, which gives a positive answer to one open problem proposed by Kenig and Merle [Invent. Math. 166 (2006, 645–675].

  9. Spectroscopy of cyanine dyes in fluid solution at atmospheric and high pressure: The effect of viscosity on nonradiative processes

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, S.; Sauerwein, B.; Drickamer, H.G.; Schuster, G.B. (Univ. of Illinois, Urbana, IL (United States))

    1994-12-22

    The spectroscopy of cyanine dyes was examined at atmospheric pressure and at high pressure in a series of alcohols and other solvents. Variation of external pressure provides the means to control viscosity over a wide range in one solvent at constant temperature. The findings reveal that the nonradiative relaxation of cyanines in fluid solution can occur when the motion leading to the formation of the cis isomer is stopped completely. Analysis of the viscosity dependence of the nonradiative relaxation rate constant reveals consistent deviation from the Kramers-DSE relation. 33 refs., 5 figs., 2 tabs.

  10. ON THE POLARIZATION PROPERTIES OF MAGNETAR GIANT FLARE PULSATING TAILS

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yuan-Pei [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Zhang, Bing, E-mail: yypspore@gmail.com, E-mail: zhang@physics.unlv.edu [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States)

    2015-12-10

    Three giant flares have been detected so far from soft gamma-ray repeaters, each characterized by an initial short hard spike and a pulsating tail. The observed pulsating tails are characterized by a duration of ∼100 s, an isotropic energy of ∼10{sup 44} erg, and a pulse period of a few seconds. The pulsating tail emission likely originates from the residual energy after the intense energy release during the initial spike, which forms a trapped fireball composed of a photon-pair plasma in a closed-field-line region of the magnetars. Observationally the spectra of pulsating tails can be fitted by the superposition of a thermal component and a power-law component, with the thermal component dominating the emission in the early and late stages of the pulsating-tail observations. In this paper, assuming that the trapped fireball is from a closed-field-line region in the magnetosphere, we calculate the atmospheric structure of the optically thick trapped fireball and the polarization properties of the trapped fireball. By properly treating the photon propagation in a hot, highly magnetized, electron–positron pair plasma, we tally photons in two modes (O mode and E mode) at a certain observational angle through Monte Carlo simulations. Our results suggest that the polarization degree depends on the viewing angle with respect to the magnetic axis of the magnetar, and can be as high as Π ≃ 30% in the 1–30 keV band, and Π ≃ 10% in the 30–100 keV band, if the line of sight is perpendicular to the magnetic axis.

  11. Continuous vs. pulsating flow boiling. Part 2: Statistical comparison using response surface methodology

    DEFF Research Database (Denmark)

    Kærn, Martin Ryhl; Elmegaard, Brian; Meyer, Knud Erik

    2016-01-01

    Response surface methodology is used to investigate an active method for flow boiling heat transfer enhancement by means of fluid flow pulsation. The flow pulsations are introduced by a flow modulating expansion device and compared with the baseline continuous flow provided by a stepper-motor exp......Response surface methodology is used to investigate an active method for flow boiling heat transfer enhancement by means of fluid flow pulsation. The flow pulsations are introduced by a flow modulating expansion device and compared with the baseline continuous flow provided by a stepper...... pulsations is statistically significant in terms of the time-averaged flow boiling heat transfer coefficient. The cycle time range from 1 s to 9 s for the pulsations. The results show that the effect of fluid flow pulsations is statistically significant, disregarding the lowest heat flux measurements...

  12. Effects of self-pulsation on the spray characteristics of gas-liquid swirl coaxial injector

    Science.gov (United States)

    Kang, Zhongtao; Li, Qinglian; Cheng, Peng; Zhang, Xinqiao; Wang, Zhen-guo

    2016-10-01

    To understand the influence of self-pulsation on the spray characteristics of gas-liquid swirl coaxial injector, a back-lighting photography technique has been employed to capture the instantaneous self-pulsated spray and stable spray images with a high speed camera. The diameter and velocity of the droplets in the spray have been characterized with a Dantec Phase Doppler Anemometry (PDA) system. The effects of self-pulsation on the spray pattern, primary breakup, spray angle, diameter and velocity distribution and mass flow rate distribution are analyzed and discussed. The results show that the spray morphology is greatly influenced by self-pulsation. The stable spray has a cone shape, while the self-pulsated spray looks like a Christmas tree. The main difference of these two sprays is the primary breakup. The liquid film of stable spray keeps stable while that of self-pulsated spray oscillates periodically. The film width of self-pulsated spray varies in a large range with 'neck' and 'shoulder' features existing. The liquid film of self-pulsated spray breaks up at the second neck, and then the second shoulder begins to breakup into ligaments. The self-pulsated spray produces droplet clusters periodically, varies horizontal spray width and mass flux periodically. From the point of spatial distribution, self-pulsation is good for the spray, it uniformizes the mass flux along radius and increases the spray angle. However, when self-pulsation occurs, the SMD distribution varies from an inverted V shape to a hollow cone shape, and SMD increases at all the measuring points. Namely, from the point of atomization performance, self-pulsation has negative effects even when the breakup length is smaller. The effects of self-pulsation on the diameter and velocity distributions of the spray are mainly in the center part of the spray. The periphery of stable and self-pulsated spray has similar diameter and velocity distribution.

  13. A Non-radial Eruption in a Quadrupolar Magnetic Configuration with a Coronal Null

    CERN Document Server

    Sun, Xudong; Liu, Yang; Chen, Qingrong; Hayashi, Keiji

    2012-01-01

    We report one of several homologous non-radial eruptions from NOAA active region (AR) 11158 that are strongly modulated by the local magnetic field as observed with the Solar Dynamic Observatory (SDO). A small bipole emerged in the sunspot complex and subsequently created a quadrupolar flux system. Non-linear force-free field (NLFFF) extrapolation from vector magnetograms reveals its energetic nature: the fast-shearing bipole accumulated ~2e31 erg free energy (10% of AR total) over just one day despite its relatively small magnetic flux (5% of AR total). During the eruption, the ejected plasma followed a highly inclined trajectory, over 60 degrees with respect to the radial direction, forming a jet-like, inverted-Y shaped structure in its wake. Field extrapolation suggests complicated magnetic connectivity with a coronal null point, which is favorable of reconnection between different flux components in the quadrupolar system. Indeed, multiple pairs of flare ribbons brightened simultaneously, and coronal reco...

  14. Enhanced non-radiative energy transfer in hybrid III-nitride structures

    Energy Technology Data Exchange (ETDEWEB)

    Smith, R. M.; Athanasiou, M.; Bai, J.; Liu, B.; Wang, T., E-mail: t.wang@sheffield.ac.uk [Department of Electrical and Electronic Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2015-09-21

    The effect of surface states has been investigated in hybrid organic/inorganic white light emitting structures that employ high efficiency, nearfield non-radiative energy transfer (NRET) coupling. The structures utilize blue emitting InGaN/GaN multiple quantum well (MQW) nanorod arrays to minimize the separation with a yellow emitting F8BT coating. Surface states due to the exposed III-nitride surfaces of the nanostructures are found to reduce the NRET coupling rate. The surface states are passivated by deposition of a silicon nitride layer on the III-nitride nanorod surface leading to reduced surface recombination. A low thickness surface passivation is shown to increase the NRET coupling rate by 4 times compared to an un-passivated hybrid structure. A model is proposed to explain the increased NRET rate for the passivated hybrid structures based on the reduction in surface electron depletion of the passivated InGaN/GaN MQW nanorods surfaces.

  15. Enhanced non-radiative energy transfer in hybrid III-nitride structures

    Science.gov (United States)

    Smith, R. M.; Athanasiou, M.; Bai, J.; Liu, B.; Wang, T.

    2015-09-01

    The effect of surface states has been investigated in hybrid organic/inorganic white light emitting structures that employ high efficiency, nearfield non-radiative energy transfer (NRET) coupling. The structures utilize blue emitting InGaN/GaN multiple quantum well (MQW) nanorod arrays to minimize the separation with a yellow emitting F8BT coating. Surface states due to the exposed III-nitride surfaces of the nanostructures are found to reduce the NRET coupling rate. The surface states are passivated by deposition of a silicon nitride layer on the III-nitride nanorod surface leading to reduced surface recombination. A low thickness surface passivation is shown to increase the NRET coupling rate by 4 times compared to an un-passivated hybrid structure. A model is proposed to explain the increased NRET rate for the passivated hybrid structures based on the reduction in surface electron depletion of the passivated InGaN/GaN MQW nanorods surfaces.

  16. Disentangling nonradiative recombination processes in Ge micro-crystals on Si substrates

    Science.gov (United States)

    Pezzoli, Fabio; Giorgioni, Anna; Gallacher, Kevin; Isa, Fabio; Biagioni, Paolo; Millar, Ross W.; Gatti, Eleonora; Grilli, Emanuele; Bonera, Emiliano; Isella, Giovanni; Paul, Douglas J.; Miglio, Leo

    2016-06-01

    We address nonradiative recombination pathways by leveraging surface passivation and dislocation management in μm-scale arrays of Ge crystals grown on deeply patterned Si substrates. The time decay photoluminescence (PL) at cryogenic temperatures discloses carrier lifetimes approaching 45 ns in band-gap engineered Ge micro-crystals. This investigation provides compelling information about the competitive interplay between the radiative band-edge transitions and the trapping of carriers by dislocations and free surfaces. Furthermore, an in-depth analysis of the temperature dependence of the PL, combined with capacitance data and finite difference time domain modeling, demonstrates the effectiveness of GeO2 in passivating the surface of Ge and thus in enhancing the room temperature PL emission.

  17. Radiative and non-radiative recombinations in tensile strained Ge microstrips: Photoluminescence experiments and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Virgilio, M., E-mail: virgilio@df.unipi.it [Dip. di Fisica “E. Fermi,” Università di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy); NEST, Istituto Nanoscienze-CNR, P.za San Silvestro 12, 56127 Pisa (Italy); Schroeder, T.; Yamamoto, Y. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Capellini, G. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Dip. di scienze, Università Roma Tre, viale G. Marconi 446, 00146 Roma (Italy)

    2015-12-21

    Tensile germanium microstrips are candidate as gain material in Si-based light emitting devices due to the beneficial effect of the strain field on the radiative recombination rate. In this work, we thoroughly investigate their radiative recombination spectra by means of micro-photoluminescence experiments at different temperatures and excitation powers carried out on samples featuring different tensile strain values. For sake of comparison, bulk Ge(001) photoluminescence is also discussed. The experimental findings are interpreted in light of a numerical modeling based on a multi-valley effective mass approach, taking in to account the depth dependence of the photo-induced carrier density and of the self-absorption effect. The theoretical modeling allowed us to quantitatively describe the observed increase of the photoluminescence intensity for increasing values of strain, excitation power, and temperature. The temperature dependence of the non-radiative recombination time in this material has been inferred thanks to the model calibration procedure.

  18. The formation of entropy cores in non-radiative galaxy cluster simulations: SPH versus AMR

    CERN Document Server

    Power, C; Hobbs, A

    2013-01-01

    Abridged: We simulate a massive galaxy cluster in a LCDM Universe using three different approaches to solving the equations of non-radiative hydrodynamics: `classic' Smoothed Particle Hydrodynamics (SPH); a novel SPH with a higher order dissipation switch (SPHS); and adaptive mesh refinement (AMR). We find that SPHS and AMR are in excellent agreement, with both forming a well-defined entropy core that rapidly converges with increasing mass and force resolution. By contrast, SPH exhibits rather different behaviour. At low redshift, entropy decreases systematically with decreasing cluster-centric radius, converging on ever lower central values with increasing resolution. At higher redshift, SPH is in better agreement with SPHS and AMR but shows much poorer numerical convergence. We trace these discrepancies to artificial surface tension in SPH at phase boundaries. At early times, the passage of massive substructures close to the cluster centre stirs and shocks gas to build an entropy core. At later times, artif...

  19. Disentangling nonradiative recombination processes in Ge micro-crystals on Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Pezzoli, Fabio, E-mail: fabio.pezzoli@unimib.it; Giorgioni, Anna; Gatti, Eleonora; Grilli, Emanuele; Bonera, Emiliano; Miglio, Leo [LNESS and Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, via Cozzi 55, I-20125 Milano (Italy); Gallacher, Kevin; Millar, Ross W.; Paul, Douglas J. [School of Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow G12 8LT (United Kingdom); Isa, Fabio [LNESS, Dipartimento di Fisica del Politecnico di Milano and IFN-CNR, Polo Territoriale di Como, Via Anzani 42, I-22100 Como (Italy); Laboratory for Solid State Physics, ETH Zurich, Otto-Stern-Weg 1, CH-8093 Zürich (Switzerland); Biagioni, Paolo [LNESS, Dipartimento di Fisica del Politecnico di Milano and IFN-CNR, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Isella, Giovanni [LNESS, Dipartimento di Fisica del Politecnico di Milano and IFN-CNR, Polo Territoriale di Como, Via Anzani 42, I-22100 Como (Italy)

    2016-06-27

    We address nonradiative recombination pathways by leveraging surface passivation and dislocation management in μm-scale arrays of Ge crystals grown on deeply patterned Si substrates. The time decay photoluminescence (PL) at cryogenic temperatures discloses carrier lifetimes approaching 45 ns in band-gap engineered Ge micro-crystals. This investigation provides compelling information about the competitive interplay between the radiative band-edge transitions and the trapping of carriers by dislocations and free surfaces. Furthermore, an in-depth analysis of the temperature dependence of the PL, combined with capacitance data and finite difference time domain modeling, demonstrates the effectiveness of GeO{sub 2} in passivating the surface of Ge and thus in enhancing the room temperature PL emission.

  20. Lasing in organic semiconductors - time-resolved studies of non-radiative decay processes

    CERN Document Server

    Zenz, C R

    2000-01-01

    Based on the demonstration of optical gain in an organic single crystal of a soluble oligo-phenylene-vinylene with gain values higher than 60 cm-1 and optically pumped lasing in a longitudinal adjustable microcavity based on laddertype polyparaphenylene, the realization of an organic laserdiode is discussed. The output characteristics of the microcavity can be modeled using classical rate equations, however the obtained threshold values are limited by the short excited state lifetime. A comparison with the lifetime measured on isolated molecules shows, that non-radiative decay processes in the solid state are determining the excited state lifetime. Using conventional and a novel field-assisted differential transmission spectroscopy with femtosecond time resolution, two main decay mechanism could be identified. (i) Triplet exciton in para-hexaphenyl is formed by non-geminate recombination of photo-generated polarons. (ii) Dissociation of the luminescent singlet excitons into polarons is important for two reaso...

  1. Non-Radiative Energy Transfer Mediated by Hybrid Light-Matter States.

    Science.gov (United States)

    Zhong, Xiaolan; Chervy, Thibault; Wang, Shaojun; George, Jino; Thomas, Anoop; Hutchison, James A; Devaux, Eloise; Genet, Cyriaque; Ebbesen, Thomas W

    2016-05-17

    We present direct evidence of enhanced non-radiative energy transfer between two J-aggregated cyanine dyes strongly coupled to the vacuum field of a cavity. Excitation spectroscopy and femtosecond pump-probe measurements show that the energy transfer is highly efficient when both the donor and acceptor form light-matter hybrid states with the vacuum field. The rate of energy transfer is increased by a factor of seven under those conditions as compared to the normal situation outside the cavity, with a corresponding effect on the energy transfer efficiency. The delocalized hybrid states connect the donor and acceptor molecules and clearly play the role of a bridge to enhance the rate of energy transfer. This finding has fundamental implications for coherent energy transport and light-energy harvesting.

  2. Method for determining effective nonradiative lifetime and leakage losses in double-heterostructure lasers

    Energy Technology Data Exchange (ETDEWEB)

    van Opdorp, C.; ' t Hooft, G.W.

    1981-06-01

    Carrier losses in double-heterostructure lasers are twofold: (i) nonradiative recombination through killers in the bulk of the active region and at all its boundaries (interfaces and surfaces), and (ii) leakage out of the active region. A simple theory shows the following. In the high-injection regime (papprox. =n) all processes under (i) are directly proportional to n. Consequently their contributions can be lumped together in a single effective nonradiative carrier lifetime tau/sub nr/ ; this tau/sub nr/ is constant (i.e., independent of n) owing to the constant degree of occupation of all killers in the mentioned regime. On the other hand, the leakage losses (ii) are superlinear in n. This provides a well-grounded basis for disentangling the contributions of (i) and (ii) in a given sample. Further, a simple method is presented for accurately determining tau/sub nr/ from data of the external quantum efficiency eta/sub ext/ measured as a function of current I in the spontaneous high-injection regime below the laser threshold. Knowledge of the light-extraction factor (i.e., the ratio of external and internal quantum efficiencies) is essentially unnecessary with this method. However, optionally it can be determined easily from a slight extension of the method. For illustration the method of determining tau/sub nr/, which is also applicable to double-hetero LED's, has been applied to some thirty LPE and metal-organic VPE GaAs-(Ga,Al)As lasers of widely varying qualities. The values found vary between 0.8 and 55 ns. From the measured values of tau/sub nr/ it follows that the upper limit for the interface recombination velocity in the best samples is 270 cm/s. For most samples tau/sub nr/ cannot account for all electrical losses at laser threshold. The superlinear excess losses are ascribable to leakage.

  3. Understanding and eliminating non-radiative decay in organic-inorganic perovskites (Conference Presentation)

    Science.gov (United States)

    Stranks, Samuel D.; de Quilettes, Dane

    2016-09-01

    Organic-inorganic perovskites such as CH3NH3PbI3 are highly promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21% and promising applications in light-emitting diodes, lasers and photodetectors also emerging. A key enabling property of the perovskites is their high photoluminescence quantum efficiency, suggesting that these materials could in principle approach the thermodynamic device efficiency limits in which all recombination is radiative. However, non-radiative recombination sites are present which vary heterogeneously from grain to grain and limit device performance. Here, I will present results where we probe the local photophysics of neat CH3NH3PbI3 perovskite films using confocal photoluminescence (PL) measurements and correlate the observations with the local chemistry of the grains using energy-dispersive X-ray spectroscopy (EDX) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). We investigate the connection between grains that are bright or dark in emission and the local Pb:I ratios at the surface and through the grains. We also examine how the photophysics, local chemistry and non-radiative decay pathways change slowly over time under illumination. Our results reveal a "photo-induced cleaning" arising from a redistribution of iodide content in the films, giving strong evidence for photo-induced ion migration. These slow transient effects appear to be related to anomalous hysteresis phenomena observed in full solar cells. I will discuss how immobilizing ions, reducing trap densities and achieving homogenous stoichiometries could suppress hysteresis effects and lead to devices approaching the efficiency limits.

  4. Nonadiabatic nonradial p-mode frequencies of the standard solar model, with and without helium diffusion

    Science.gov (United States)

    Guenther, D. B.

    1994-01-01

    The nonadiabatic frequencies of a standard solar model and a solar model that includes helium diffusion are discussed. The nonadiabatic pulsation calculation includes physics that describes the losses and gains due to radiation. Radiative gains and losses are modeled in both the diffusion approximation, which is only valid in optically thick regions, and the Eddington approximation, which is valid in both optically thin and thick regions. The calculated pulsation frequencies for modes with l less than or equal to 1320 are compared to the observed spectrum of the Sun. Compared to a strictly adiabatic calculation, the nonadiabatic calculation of p-mode frequencies improves the agreement between model and observation. When helium diffusion is included in the model the frequencies of the modes that are sensitive to regions near the base of the convection zone are improved (i.e., brought into closer agreement with observation), but the agreement is made worse for other modes. Cyclic variations in the frequency spacings of the Sun as a function of frequency of n are presented as evidence for a discontinuity in the structure of the Sun, possibly located near the base of the convection zone.

  5. Three Lectures on Hadron Physics

    CERN Document Server

    Roberts, Craig D

    2015-01-01

    These lectures explain that comparisons between experiment and theory can expose the impact of running couplings and masses on hadron observables and thereby aid materially in charting the momentum dependence of the interaction that underlies strong-interaction dynamics. The series begins with a primer on continuum QCD, which introduces some of the basic ideas necessary in order to understand the use of Schwinger functions as a nonperturbative tool in hadron physics. It continues with a discussion of confinement and dynamical symmetry breaking (DCSB) in the Standard Model, and the impact of these phenomena on our understanding of condensates, the parton structure of hadrons, and the pion electromagnetic form factor. The final lecture treats the problem of grand unification; namely, the contemporary use of Schwinger functions as a symmetry-preserving tool for the unified explanation and prediction of the properties of both mesons and baryons. It reveals that DCSB drives the formation of diquark clusters in bar...

  6. Kindergarten Quantum Mechanics lectures notes

    CERN Document Server

    Coecke, B

    2005-01-01

    These lecture notes survey some joint work with Samson Abramsky as it was presented by me at several conferences in the summer of 2005. It concerns `doing quantum mechanics using only pictures of lines, squares, triangles and diamonds'. This picture calculus can be seen as a very substantial extension of Dirac's notation, and has a purely algebraic counterpart in terms of so-called Strongly Compact Closed Categories (introduced by Abramsky and I in quant-ph/0402130 and [4]) which subsumes my Logic of Entanglement quant-ph/0402014. For a survey on the `what', the `why' and the `hows' I refer to a previous set of lecture notes quant-ph/0506132. In a last section we provide some pointers to the body of technical literature on the subject.

  7. ACADEMIC TRAINING LECTURES-QUESTIONNAIRE

    CERN Multimedia

    Françoise Benz

    2004-01-01

    ACADEMIC TRAINING Françoise Benz tel. 73127 academic.training@cern.ch SUGGEST AND WIN! Its time to plan the 2004-2005 lecture series. From today until March 19 you have the chance to give your contribution to planning for next year's Academic Training Lecture Series. At the web site: http://cern.ch/Academic.Training/questionnaire you will find questionnaires proposing topics in high energy physics, applied physics and science and society. Answering the questionnaire will help ensure that the selected topics are as close as possible to your interests. In particular requests and comments from students will be much appreciated. To encourage your contribution, the AT Committee will reward one lucky winner with a small prize, a 50 CHF coupon for a book purchase at the CERN bookshop.

  8. Lectures on Dark Matter Physics

    CERN Document Server

    Lisanti, Mariangela

    2016-01-01

    Rotation curve measurements from the 1970s provided the first strong indication that a significant fraction of matter in the Universe is non-baryonic. In the intervening years, a tremendous amount of progress has been made on both the theoretical and experimental fronts in the search for this missing matter, which we now know constitutes nearly 85% of the Universe's matter density. These series of lectures, first given at the TASI 2015 summer school, provide an introduction to the basics of dark matter physics. They are geared for the advanced undergraduate or graduate student interested in pursuing research in high-energy physics. The primary goal is to build an understanding of how observations constrain the assumptions that can be made about the astro- and particle physics properties of dark matter. The lectures begin by delineating the basic assumptions that can be inferred about dark matter from rotation curves. A detailed discussion of thermal dark matter follows, motivating Weakly Interacting Massive P...

  9. Lectures on matrix field theory

    CERN Document Server

    Ydri, Badis

    2017-01-01

    These lecture notes provide a systematic introduction to matrix models of quantum field theories with non-commutative and fuzzy geometries. The book initially focuses on the matrix formulation of non-commutative and fuzzy spaces, followed by a description of the non-perturbative treatment of the corresponding field theories. As an example, the phase structure of non-commutative phi-four theory is treated in great detail, with a separate chapter on the multitrace approach. The last chapter offers a general introduction to non-commutative gauge theories, while two appendices round out the text. Primarily written as a self-study guide for postgraduate students – with the aim of pedagogically introducing them to key analytical and numerical tools, as well as useful physical models in applications – these lecture notes will also benefit experienced researchers by providing a reference guide to the fundamentals of non-commutative field theory with an emphasis on matrix models and fuzzy geometries.

  10. Excitation of a nonradial mode in a millisecond X-ray pulsar XTE J1751-305

    CERN Document Server

    Lee, Umin

    2014-01-01

    We discuss candidates for non-radial modes excited in a mass accreting and rapidly rotating neutron star to explain the coherent frequency identified in the light curves of a millisecond X-ray pulsar XTE J1751-305. The spin frequency of the pulsar is $\

  11. Non-radiative decay of a dipole emitter close to a metallic nanoparticle: Importance of higher-order multipole contributions

    CERN Document Server

    Moroz, Alexander

    2009-01-01

    The contribution of higher-order multipoles to radiative and non-radiative decay of a single dipole emitter close to a spherical metallic nanoparticle is re-examined. Taking a Ag spherical nanoparticle (AgNP) with the radius of 5 nm as an example, a significant contribution (between 50% and 101% of the total value) of higher-order multipoles to non-radiative rates is found even at the emitter distance of 5 nm from the AgNP surface. On the other hand, the higher-order multipole contribution to radiative rates is negligible. Consequently, a dipole-dipole approximation can yield only an upper bound on the apparent quantum yield. In contrast, the non-radiative rates calculated with the quasistatic Gersten and Nitzan method are found to be in much better agreement with exact electrodynamic results. Finally, the size corrected metal dielectric function is shown to decrease the non-radiative rates near the dipolar surface plasmon resonance.

  12. Lectures on Matrix Field Theory

    Science.gov (United States)

    Ydri, Badis

    The subject of matrix field theory involves matrix models, noncommutative geometry, fuzzy physics and noncommutative field theory and their interplay. In these lectures, a lot of emphasis is placed on the matrix formulation of noncommutative and fuzzy spaces, and on the non-perturbative treatment of the corresponding field theories. In particular, the phase structure of noncommutative $\\phi^4$ theory is treated in great detail, and an introduction to noncommutative gauge theory is given.

  13. Academic Training Lecture - Regular Programme

    CERN Multimedia

    PH Department

    2010-01-01

    Tuesday 25 & Wednesday 26 May 2010 from 11:00 to 12:30 - Main Auditorium, Bldg. 500-1-001 Baryon Asymmetry of the Universe by Prof. Hitoshi Murayama (University of California, Berkeley) In two lectures, the following topics will be discussed: (1) Why baryon asymmetry is a problem at all (2) Review of the Sakharov's conditions (3) Why old models based on GUT did not work (4) Electroweak baryogenesis (5) Leptogenesis (6) Connections to the near-future experiments

  14. Lecture Notes on Differential Forms

    OpenAIRE

    2016-01-01

    This is a series of lecture notes, with embedded problems, aimed at students studying differential topology. Many revered texts, such as Spivak's "Calculus on Manifolds" and Guillemin and Pollack's "Differential Topology" introduce forms by first working through properties of alternating tensors. Unfortunately, many students get bogged down with the whole notion of tensors and never get to the punch lines: Stokes' Theorem, de Rham cohomology, Poincare duality, and the realization of various t...

  15. TASI 2006 Lectures on Leptogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Mu-Chun; /Fermilab /UC, Irvine

    2007-03-01

    The origin of the asymmetry between matter and anti-matter of the Universe has been one of the great challenges in particle physics and cosmology. Leptogenesis as a mechanism for generating the cosmological baryon asymmetry of the Universe has gained significant interests ever since the advent of the evidence of non-zero neutrino masses. In these lectures presented at TASI 2006, I review various realizations of leptogenesis and allude to recent developments in this subject.

  16. MGMT 30100: Management Career Lectures

    OpenAIRE

    Landis, Maureen Huffer

    2014-01-01

    Abstract: Management Career Lectures (MGMT 30100) is designed to help undergraduate management students with their overall career/professional development whether that focus on internship/job search processes or graduate school attendance. The course also supports the development, refinement and enrichment of the competencies within the “Launching Business Leaders” initiative. Students develop skills useful for the internship/job search process, gain knowledge that benefits short and long-ter...

  17. Pulsating combustion - Combustion characteristics and reduction of emissions

    Energy Technology Data Exchange (ETDEWEB)

    Lindholm, Annika

    1999-11-01

    In the search for high efficiency combustion systems pulsating combustion has been identified as one of the technologies that potentially can meet the objectives of clean combustion and good fuel economy. Pulsating combustion offers low emissions of pollutants, high heat transfer and efficient combustion. Although it is an old technology, the interest in pulsating combustion has been renewed in recent years, due to its unique features. Various applications of pulsating combustion can be found, mainly as drying and heating devices, of which the latter also have had commercial success. It is, however, in the design process of a pulse combustor, difficult to predict the operating frequency, the heat release etc., due to the lack of a well founded theory of the phenomenon. Research concerning control over the combustion process is essential for developing high efficiency pulse combustors with low emissions. Natural gas fired Helmholtz type pulse combustors have been the experimental objects of this study. In order to investigate the interaction between the fluid dynamics and the chemistry in pulse combustors, laser based measuring techniques as well as other conventional measuring techniques have been used. The experimental results shows the possibilities to control the combustion characteristics of pulsating combustion. It is shown that the time scales in the large vortices created at the inlet to the combustion chamber are very important for the operation of the pulse combustor. By increasing/decreasing the time scale for the large scale mixing the timing of the heat release is changed and the operating characteristics of the pulse combustor changes. Three different means for NO{sub x} reduction in Helmholtz type pulse combustors have been investigated. These include exhaust gas recirculation, alteration of air/fuel ratio and changed inlet geometry in the combustion chamber. All used methods achieved less than 10 ppm NO{sub x} emitted (referred to stoichiometric

  18. Three Lectures on Hadron Physics

    Science.gov (United States)

    Roberts, Craig D.

    2016-04-01

    These lectures explain that comparisons between experiment and theory can expose the impact of running couplings and masses on hadron observables and thereby aid materially in charting the momentum dependence of the interaction that underlies strong-interaction dynamics. The series begins with a primer on continuum QCD, which introduces some of the basic ideas necessary in order to understand the use of Schwinger functions as a nonperturbative tool in hadron physics. It continues with a discussion of confinement and dynamical symmetry breaking (DCSB) in the Standard Model, and the impact of these phenomena on our understanding of condensates, the parton structure of hadrons, and the pion electromagnetic form factor. The final lecture treats the problem of grand unification; namely, the contemporary use of Schwinger functions as a symmetry-preserving tool for the unified explanation and prediction of the properties of both mesons and baryons. It reveals that DCSB drives the formation of diquark clusters in baryons and sketches a picture of baryons as bound-states with Borromean character. Planned experiments are capable of validating the perspectives outlined in these lectures.

  19. Features of Pc5 pulsations in the geomagnetic field, auroral luminosity, and Riometer absorption

    Science.gov (United States)

    Belakhovsky, V. B.; Pilipenko, V. A.; Samsonov, S. N.; Lorentsen, D.

    2016-01-01

    Simultaneous morning Pc5 pulsations ( f ~ 3-5 mHz) in the geomagnetic field, aurora intensities (in the 557.7 and 630.0 nm oxygen emissions and the 471.0 nm nitrogen emission), and riometer absorption, were studied based on the CARISMA, CANMOS, and NORSTAR network data for the event of January 1, 2000. According to the GOES-8 satellite observations, these Pc5 geomagnetic pulsations are observed as incompressible Alfvén waves with toroidal polarization in the magnetosphere. Although the Pc5 pulsation frequencies in auroras, the geomagnetic field, and riometer absorption are close to one another, stable phase relationships are not observed between them. Far from all trains of geomagnetic Pc5 pulsations are accompanied by corresponding auroral pulsations; consequently, geomagnetic pulsations are primary with respect to auroral pulsations. Both geomagnetic and auroral pulsations propagate poleward, and the frequency decreases with increasing geomagnetic latitude. When auroral Pc5 pulsations appear, the ratio of the 557.7/630.0 nm emission intensity sharply increases, which indicates that auroral pulsations result from not simply modulated particle precipitation but also an additional periodic acceleration of auroral electrons by the wave field. A high correlation is not observed between Pc5 pulsations in auroras and the riometer absorption, which indicates that these pulsations have a common source but different generation mechanisms. Auroral luminosity modulation is supposedly related to the interaction between Alfvén waves and the region with the field-aligned potential drop above the auroral ionosphere, and riometer absorption modulation is caused by the scattering of energetic electrons by VLF noise pulsations.

  20. On the optical pulsations from the Geminga pulsar

    CERN Document Server

    Gil, J; Melikidze, G I; Gil, Janusz; Khechinashvili, David; Melikidze, George

    2000-01-01

    We present a model for generation mechanisms of the optical pulsations recently detected from the Geminga pulsar. We argue that this is just a synchrotron radiation emitted along open magnetic field lines at altitudes of a few light cylinder radii (which requires that Geminga is an almost aligned rotator), where charged particles acquire non-zero pitch-angles as a result of the cyclotron absorption of radio waves in the magnetized pair plasma. This explains self-consistently both the lack of apparent radio emission, at least at frequencies higher than about 100 MHz, and the optical pulsations from the Geminga pulsar. From our model it follows that the synchrotron radiation is a maximum in the infrared band, which suggests that Geminga should also be a source of a pulsed infrared emission.

  1. Experimental investigation on a pulsating heat pipe with hydrogen

    Science.gov (United States)

    Deng, H. R.; Liu, Y. M.; Ma, R. F.; Han, D. Y.; Gan, Z. H.; Pfotenhauer, J. M.

    2015-12-01

    The pulsating heat pipe (PHP) has been increasingly studied in cryogenic application, for its high transfer coefficient and quick response. Compared with Nb3Sn and NbTi, MgB2 whose critical transformation temperature is 39 K, is expected to replace some high-temperature superconducting materials at 25 K. In order to cool MgB2, this paper designs a Hydrogen Pulsating Heat Pipe, which allows a study of applied heat, filling ratio, turn number, inclination angle and length of adiabatic section on the thermal performance of the PHP. The thermal performance of the hydrogen PHP is investigated for filling ratios of 35%, 51%, 70% at different heat inputs, and provides information regarding the starting process is received at three filling ratios.

  2. The First Six Outbursting Cool DA White Dwarf Pulsators

    CERN Document Server

    Bell, Keaton J; Montgomery, M H; Winget, D E; Fusillo, N P Gentile; Raddi, R; Gänsicke, B T

    2016-01-01

    Extensive observations from the Kepler spacecraft have recently revealed a new outburst phenomenon operating in cool pulsating DA (hydrogen atmosphere) white dwarfs (DAVs). With the introduction of two new outbursting DAVs from K2 Fields 7 (EPIC 229228364) and 8 (EPIC 220453225) in these proceedings, we presently know of six total members of this class of object. We present the observational commonalities of the outbursting DAVs: (1) outbursts that increase the mean stellar flux by up to 15%, last many hours, and recur irregularly on timescales of days; (2) effective temperatures that locate them near the cool edge of the DAV instability strip; and (3) rich pulsation spectra with modes that are observed to wander in amplitude/frequency.

  3. Experimental research on heat transfer of pulsating heat pipe

    Institute of Scientific and Technical Information of China (English)

    LI Jia; Yan Li

    2008-01-01

    Experimental research was conducted to understand heat transfer characteristic of pulsating heat pipe in this paper,and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fill ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heat pipe with changing diameters the thermal resistance is higher than that with uniform diameters.

  4. Quantitative results of stellar evolution and pulsation theories.

    Science.gov (United States)

    Fricke, K.; Stobie, R. S.; Strittmatter, P. A.

    1971-01-01

    The discrepancy between the masses of Cepheid variables deduced from evolution theory and pulsation theory is examined. The effect of input physics on evolutionary tracks is first discussed; in particular, changes in the opacity are considered. The sensitivity of pulsation masses to opacity changes and to the ascribed values of luminosity and effective temperature are then analyzed. The Cepheid mass discrepancy is discussed in the light of the results already obtained. Other astronomical evidence, including the mass-luminosity relation for main sequence stars, the solar neutrino flux, and cluster ages are also considered in an attempt to determine the most likely source of error in the event that substantial mass loss has not occurred.

  5. Study of the Thermal Pulsation of AGB Stars

    CERN Document Server

    Halabi, Ghina M

    2014-01-01

    A systematic investigation on the third dredge up in a 3M$_{\\odot}$, solar metallicity AGB star will be presented. The model evolves from the main sequence up to the Asymptotic Giant Branch (AGB). Intermediate mass stars are important because they contribute significantly via the slow neutron capture nucleosynthesis. The aim of this work is to gain insight on the behaviour of the AGB star during thermal pulsation. This investigation is based on an extended numerical simulation of the evolutionary phases and full, consistent AGB model calculations. In particular, the convective structure during pulsation will be studied, giving particular emphasis to the analysis of the stability of the Schwarzschild boundary that will eventually determine the occurrence of Third Dredge Up (hereafter referred to as TDUP). We provide a brief description of our updated evolutionary code and focus primarily on the obtaining the TDUP after 14 thermal pulses. We elaborate on the non-standard treatment of convection known as "oversh...

  6. Pulsating laminar pipe flows with sinusoidal mass flux variations

    Science.gov (United States)

    Ünsal, B.; Ray, S.; Durst, F.; Ertunç, Ö.

    2005-11-01

    Combined analytical and experimental investigation of sinusoidal mass flow-controlled, pulsating, laminar and fully developed pipe flow was carried out. The experimental investigation employed a mass flow control unit built at LSTM-Erlangen for the present investigation. For the analytical investigation, the equations describing such flows were normalized to allow for a general solution, depending only on the normalized amplitude mA* of the mass flow pulsation and the normalized frequency F. The analytical and experimental results are presented in this normalized way and it is shown that good agreement between the results of the authors is obtained. A diagram is presented for the condition of flow reversal in terms of the dimensionless frequency F and the mass flow rate amplitude mA*.

  7. Quasi-periodic pulsations in partially occulted flares

    Science.gov (United States)

    Szaforz, Zaneta; Tomczak, Michal

    The model of oscillating magnetic traps (OMT) suggests that the cusp-like magnetic structures located in an upper part of flare loops are responsible for quasi-periodic pulsations (QPP) observed sometimes in hard X-rays (HXR). Electrons within these oscillating traps are efficiently accelerated and confined, therefore the traps should be recognize as loop-top HXR sources. However, these sources are difficult for reconstruction in the presence of the stronger footpoint HXR sources. To overcome this problem, we analyzed partially occulted flares, observed by Yohkoh, from the survey of Tomczak (2009). We will present the correlation between the diameter of the loop-top HXR source and the period of pulsations. We will present also some interesting examples of observations, for which changes in QPPs coincide with the changes in appearance of loop-top sources.

  8. Modelling hybrid Beta Cephei/SPB pulsations: Gamma Pegasi

    CERN Document Server

    Zdravkov, T

    2009-01-01

    Recent photometric and spectroscopic observations of the hybrid variable Gamma Pegasi (Handler et al. 2009, Handler 2009) revealed 6 frequencies of the SPB type and 8 of the Beta Cep type pulsations. Standard seismic models, which have been constructed with OPAL (Iglesias & Rogers 1996) and OP (Seaton 2005) opacities by fitting three frequencies (those of the radial fundamental and two dipole modes), do not reproduce the frequency range of observed pulsations and do not fit the observed individual frequencies with a satisfactory accuracy. We argue that better fitting can be achieved with opacity enhancements, over the OP data, by about 20-50 percent around the opacity bumps produced by excited ions of the iron-group elements at temperatures of about 200 000 K (Z bump) and 2 million K (Deep Opacity Bump).

  9. Decreasing of pulsation intensity levels in X-ray receivers

    CERN Document Server

    Dvoryankin, V F; Kudryashov, A A; Petrov, A G

    2002-01-01

    The low frequency filter is applied in the multichannel receiver on the basis of the GaAs epitaxial structures for decreasing the pulsations level at the signals amplifier outlet. The optimal band of the filter is determined by the transition processes by the detector scanning in the roentgen beams. The X-ray source of radiation with the medium-frequency feeding generator is used for verifying the quality of the obtained X-ray image

  10. A size limit for uniformly pulsating sources of electromagnetic radiation

    Energy Technology Data Exchange (ETDEWEB)

    Dewdney, A.K.

    1979-01-01

    An extremal model for a uniformly pulsating source of electromagnetic radiation is developed, and a formula is obtained which relates the source variation to diameter, pulse width, and period. An upper limit on source diameter is derived from this formula, applied to three pulsars, and compared with standard estimates of their diameters. The use of the limit formula is shown to be no less justified, in general, than the size estimate based on the product of variation period and the speed of light.

  11. Effect of orientation on heat transfer in pulsating heat pipe

    Directory of Open Access Journals (Sweden)

    Naumova A. M.

    2010-10-01

    Full Text Available The paper presents the results of experimental research of orientation effect on heat transfer characteristics of a pulsating heat pipe (PHP. It is shown that transport of either mass or heat depends on PHP orientation against it`s axis. As a consequence of comparing experimental data with other authors’ results it was concluded that PHP thermal resistance depends not only on orientation but on some other determinal factors such as device construction and thermophysical properties of heat carrier.

  12. Research of heat exchange rate of the pulsating heat pipe

    Directory of Open Access Journals (Sweden)

    Kravets V. Yu.

    2010-02-01

    Full Text Available Given article presents experimental research of heat transfer characteristics of the pulsating heat pipe (PHP which consists of seven coils with 1 mm inner diameter. Water was used as the heat carrier. PHP construction, measuring circuit and research technique are presented. It is shown that under PHP functioning there are two characteristic modes of operation, which can be distinguished by values of thermal resistance. PHP heat exchange features are disclosed.

  13. Diffusion and pulsations in slowly rotating B stars

    CERN Document Server

    Turcotte, S

    2005-01-01

    Diffusion in cool B stars of the main sequence has been shown to strongly affect opacities and convection in cool B stars of the main sequence. We show here that diffusion in B stars maintains or enhances the excitation of pulsations in these stars. This result conflicts with observations as cool B stars that show evidence of diffusion, the HgMn stars, are stable to the current detection level. We discuss possible implications of this discrepancy for the models.

  14. Effects of Uniform and Differential Rotation on Stellar Pulsations

    OpenAIRE

    Lovekin, C. C.; Deupree, R. G.; Clement, M.J.

    2008-01-01

    We have investigated the effects of uniform rotation and a specific model for differential rotation on the pulsation frequencies of 10 \\Msun\\ stellar models. Uniform rotation decreases the frequencies for all modes. Differential rotation does not appear to have a significant effect on the frequencies, except for the most extreme differentially rotating models. In all cases, the large and small separations show the effects of rotation at lower velocities than do the individual frequencies. Unf...

  15. Self-pulsation threshold of Raman amplified Brillouin fiber cavities.

    Science.gov (United States)

    Ott, J R; Pedersen, M E V; Rottwitt, K

    2009-08-31

    An implicit equation for the oscillation threshold of stimulated Brillouin scattering from Raman amplified signals in fibers with external feedback is derived under the assumption of no depletion. This is compared to numerical investigations of Raman amplification schemes showing good agreement for high reflectivities. For low reflectivities and high attenuation or long fibers, the assumption of no depletion is shown not to be valid. In these cases the effects of the depletion on the self-pulsation is examined.

  16. Self-pulsation threshold of Raman amplified Brillouin fiber cavities

    DEFF Research Database (Denmark)

    Ott, Johan Raunkjær; Pedersen, Martin Erland Vestergaard; Rottwitt, Karsten

    2009-01-01

    An implicit equation for the oscillation threshold of stimulated Brillouin scattering from Raman amplified signals in fibers with external feedback is derived under the assumption of no depletion. This is compared to numerical investigations of Raman amplification schemes showing good agreement...... for high reflectivities. For low reflectivities and high attenuation or long fibers, the assumption of no depletion is shown not to be valid. In these cases the effects of the depletion on the self-pulsation is examined....

  17. THE PULSATION MODE AND DISTANCE OF THE CEPHEID FF AQUILAE

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D. G. [Department of Astronomy and Physics, Saint Mary' s University, Halifax, NS B3H 3C3 (Canada); Kovtyukh, V. V. [Astronomical Observatory, Odessa National University, and Isaac Newton Institute of Chile, Odessa Branch, T. G. Shevkenko Park, 65014 Odessa (Ukraine); Luck, R. E. [Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215 (United States); Berdnikov, L. N., E-mail: turner@ap.smu.ca, E-mail: val@deneb1.odessa.ua, E-mail: rel2@case.edu, E-mail: leonid.berdnikov@gmail.com [Sternberg Astronomical Institute, Moscow M. V. Lomonosov State University, Moscow 119992 (Russian Federation)

    2013-07-20

    The determination of pulsation mode and distance for field Cepheids is a complicated problem best resolved by a luminosity estimate. For illustration a technique based on spectroscopic luminosity discrimination is applied to the 4.47 day s-Cepheid FF Aql. Line ratios in high dispersion spectra of the variable yield values of (M{sub V} ) = -3.40 {+-} 0.02 s.e. ({+-}0.04 s.d.), average effective temperature T{sub eff} = 6195 {+-} 24 K, and intrinsic color ((B) - (V)){sub 0} = +0.506 {+-} 0.007, corresponding to a reddening of E{sub B-V} = 0.25 {+-} 0.01, or E{sub B-V}(B0) = 0.26 {+-} 0.01. The skewed light curve, intrinsic color, and luminosity of FF Aql are consistent with fundamental mode pulsation for a small-amplitude classical Cepheid on the blue side of the instability strip, not a sinusoidal pulsator. A distance of 413 {+-} 14 pc is estimated from the Cepheid's angular diameter in conjunction with a mean radius of (R) = 39.0 {+-} 0.7 R{sub Sun} inferred from its luminosity and effective temperature. The dust extinction toward FF Aql is described by a ratio of total-to-selective extinction of R{sub V} = A{sub V} /E(B - V) = 3.16 {+-} 0.34 according to the star's apparent distance modulus.

  18. Development of a balloon volume sensor for pulsating balloon catheters.

    Science.gov (United States)

    Nolan, Timothy D C; Hattler, Brack G; Federspiel, William J

    2004-01-01

    Helium pulsed balloons are integral components of several cardiovascular devices, including intraaortic balloon pumps (IABP) and a novel intravenous respiratory support catheter. Effective use of these devices clinically requires full inflation and deflation of the balloon, and improper operating conditions that lead to balloon under-inflation can potentially reduce respiratory or cardiac support provided to the patient. The goal of the present study was to extend basic spirographic techniques to develop a system to dynamically measure balloon volumes suitable for use in rapidly pulsating balloon catheters. The dynamic balloon volume sensor system (DBVSS) developed here used hot wire anemometry to measure helium flow in the drive line from console to catheter and integrated the flow to determine the volume delivered in each balloon pulsation. An important component of the DBVSS was an algorithm to automatically detect and adjust flow signals and measured balloon volumes in the presence of gas composition changes that arise from helium leaks occurring in these systems. The DBVSS was capable of measuring balloon volumes within 5-10% of actual balloon volumes over a broad range of operating conditions relevant to IABP and the respiratory support catheter. This includes variations in helium concentration from 70-100%, pulsation frequencies from 120-480 beats per minute, and simulated clinical conditions of reduced balloon filling caused by constricted vessels, increased driveline, or catheter resistance.

  19. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    CERN Document Server

    Córsico, Alejandro H; Bertolami, Marcelo M Miller; Kepler, S O; García-Berro, Enrique

    2014-01-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. By comparing the theoretical rate of change of period expected for this star with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment. Our upper limit for the neutrino magnetic dipole moment is somewhat less restrictive than, but still compat...

  20. Studies of the Long Secondary Periods in Pulsating Red Giants

    Science.gov (United States)

    Percy, J. R.; Deibert, E.

    2016-12-01

    We have used systematic, sustained visual observations from the AAVSO International Database and the AAVSO time-series analysis package VSTAR to study the unexplained "long secondary periods" (LSPs) in 27 pulsating red giants. In our sample, the LSPs range from 479 to 2967 days, and are on average 8.1 +/- 1.3 times the excited pulsation period. There is no evidence for more than one LSP in each star. In stars with both the fundamental and first overtone radial period present, the LSP is more often about 10 times the latter. The visual amplitudes of the LSPs are typically 0.1 magnitude and do not correlate with the LSP. The phase curves tend to be sinusoidal, but at least two are sawtooth. The LSPs are stable, within their errors, over the timespan of our data, which is typically 25,000 days. The amplitudes, however, vary by up to a factor of two or more on a time scale of roughly 20-30 LSPs. There is no obvious difference between the carbon (C) stars and the normal oxygen (M) stars. Previous multicolor observations showed that the LSP color variations are similar to those of the pulsation period, and of the LSPs in the Magellanic Clouds, and not like those of eclipsing stars. We note that the LSPs are similar to the estimated rotation periods of the stars, though the latter have large uncertainties. This suggests that the LSP phenomenon may be a form of modulated rotational variability.

  1. Mass-spring model of a self-pulsating drop.

    Science.gov (United States)

    Antoine, Charles; Pimienta, Véronique

    2013-12-03

    Self-pulsating sessile drops are a striking example of the richness of far-from-equilibrium liquid/liquid systems. The complex dynamics of such systems is still not fully understood, and simple models are required to grasp the mechanisms at stake. In this article, we present a simple mass-spring mechanical model of the highly regular drop pulsations observed in Pimienta, V.; Brost, M.; Kovalchuk, N.; Bresch, S.; Steinbock, O. Complex shapes and dynamics of dissolving drops of dichloromethane. Angew. Chem., Int. Ed. 2011, 50, 10728-10731. We introduce an effective time-dependent spreading coefficient that sums up all of the forces (due to evaporation, solubilization, surfactant transfer, coffee ring effect, solutal and thermal Marangoni flows, drop elasticity, etc.) that pull or push the edge of a dichloromethane liquid lens, and we show how to account for the periodic rim breakup. The model is examined and compared against experimental observations. The spreading parts of the pulsations are very rapid and cannot be explained by a constant positive spreading coefficient or superspreading.

  2. Continuous versus pulsating flow boiling. Experimental comparison, visualization, and statistical analysis

    DEFF Research Database (Denmark)

    Kærn, Martin Ryhl; Elmegaard, Brian; Meyer, Knud Erik

    2017-01-01

    are reduced from transient measurements immediately downstream of the expansion valves at low vapor qualities. The results show that the pulsations improve the time-averaged heat transfer coefficient by 3.2% on average at low cycle time (1 to 2 s), whereas the pulsations may reduce the time-averaged heat......This experimental study investigates an active method for flow boiling heat transfer enhancement by means of fluid flow pulsation. The hypothesis is that pulsations increase the flow boiling heat transfer by means of better bulk fluid mixing, increased wall wetting, and flow-regime destabilization....... The fluid pulsations are introduced by a flow modulating expansion device and are compared with continuous flow by a stepper-motor expansion valve in terms of time-averaged heat transfer coefficient. The cycle time ranges from 1 to 9 s for the pulsations. The time-averaged heat transfer coefficients...

  3. Continuous vs. pulsating flow boiling. Part 1: Experimental comparison and visualization

    DEFF Research Database (Denmark)

    Kærn, Martin Ryhl; Elmegaard, Brian; Meyer, Knud Erik

    2016-01-01

    are reduced from transient measurements immediately downstream of the expansion valves at low vapor qualities. The results show that the pulsations improve the time-averaged heat transfer coefficient by 3.2 % on average at low cycle time (1 s to 2) s, whereas the pulsations may reduce the time-averaged heat......This experimental study investigates an active method for flow boiling heat transfer enhancement by means of fluid flow pulsation. The hypothesis is that pulsations increase the flow boiling heat transfer by means of better bulk fluid mixing, increased wall wetting and flow-regime destabilization....... The fluid pulsations are introduced by a flow modulating expansion device and are compared with continuous flow by a stepper-motor expansion valve in terms of time-averaged heat transfer coefficient. The cycle time ranges from 1 s to 9 s for the pulsations. The time-averaged heat transfer coefficients...

  4. A Study on the Influence of Commutation Time on Torque Pulsating in BLDCM

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Choel Ju; Kang, Byoung Hee; Mok, Hyoung Su; Choe, Gyu-Ha [Konkuk University, Seoul(Korea)

    2001-01-01

    A BLDC motor has a serious drawback that torque pulsation is generated in every commutation period though it has many advantages compared to the conventional DC Motor. In this paper, the influence of commutation time on torque pulsation is studied. Generally in calculating the torque of BLDC motor, it is assumed that the decaying phase back EMF is constant, but the torque model considering decaying phase back EMF is introduced here. Through it, the torque in commutation period has torque pulsation component caused by commutation itself and it cannot be removed perfectly even if there is no current and pulsation. To reduce the torque pulsation, a new method is proposed, which controls a point of commutation and the optimal point of commutation is found. Simulation shows proposed method reduces the torque pulsation considerately. (author). 5 refs., 8 figs., 2 tabs.

  5. Excited-state structure, vibrations, and nonradiative relaxation of jet-cooled 5-fluorocytosine.

    Science.gov (United States)

    Lobsiger, Simon; Trachsel, Maria A; Den, Takuya; Leutwyler, Samuel

    2014-03-20

    The S0 → S1 vibronic spectrum and S1 state nonradiative relaxation of jet-cooled keto-amino 5-fluorocytosine (5FCyt) are investigated by two-color resonant two-photon ionization spectroscopy at 0.3 and 0.05 cm(–1) resolution. The 0(0)(0) rotational band contour is polarized in-plane, implying that the electronic transition is (1)ππ*. The electronic transition dipole moment orientation and the changes of rotational constants agree closely with the SCS-CC2 calculated values for the (1)ππ* (S1) transition of 5FCyt. The spectral region from 0 to 300 cm(–1) is dominated by overtone and combination bands of the out-of-plane ν1′ (boat), ν2′ (butterfly), and ν3′ (HN–C6H twist) vibrations, implying that the pyrimidinone frame is distorted out-of-plane by the (1)ππ* excitation, in agreement with SCS-CC2 calculations. The number of vibronic bands rises strongly around +350 cm(–1); this is attributed to the (1)ππ* state barrier to planarity that corresponds to the central maximum of the double-minimum out-of-plane vibrational potentials along the ν1′, ν2′, and ν3′ coordinates, which gives rise to a high density of vibronic excitations. At +1200 cm(–1), rapid nonradiative relaxation (k(nr) ≥ 10(12) s(–1)) sets in, which we interpret as the height of the (1)ππ* state barrier in front of the lowest S1/S0 conical intersection. This barrier in 5FCyt is 3 times higher than that in cytosine. The lifetimes of the ν′ = 0, 2ν1′, 2ν2′, 2ν1′ + 2ν2′, 4ν2′, and 2ν1′ + 4ν2′ levels are determined from Lorentzian widths fitted to the rotational band contours and are τ ≥ 75 ps for ν′ = 0, decreasing to τ ≥ 55 ps at the 2ν1′ + 4ν2′ level at +234 cm(–1). These gas-phase lifetimes are twice those of S1 state cytosine and 10–100 times those of the other canonical nucleobases in the gas phase. On the other hand, the 5FCyt gas-phase lifetime is close to the 73 ps lifetime in room-temperature solvents. This lack of

  6. How Interactive can a Lecture Become?

    OpenAIRE

    Koohgilani,Mehran

    2014-01-01

    The uses of technology have been well documented and many people have tried to use the available technology. In an age of increasingly idevices dependent generation where on average students check their portable devices at least every 15 minutes for 15 seconds, the way students engage with the lecture and the lecturer has changed. The dynamic environment of the lecture is one which can be very enjoyable, demanding and noisy. It requires the attention of the student, note taking skills, teachi...

  7. Lecture Notes on Multigrid Methods

    Energy Technology Data Exchange (ETDEWEB)

    Vassilevski, P S

    2010-06-28

    The Lecture Notes are primarily based on a sequence of lectures given by the author while been a Fulbright scholar at 'St. Kliment Ohridski' University of Sofia, Sofia, Bulgaria during the winter semester of 2009-2010 academic year. The notes are somewhat expanded version of the actual one semester class he taught there. The material covered is slightly modified and adapted version of similar topics covered in the author's monograph 'Multilevel Block-Factorization Preconditioners' published in 2008 by Springer. The author tried to keep the notes as self-contained as possible. That is why the lecture notes begin with some basic introductory matrix-vector linear algebra, numerical PDEs (finite element) facts emphasizing the relations between functions in finite dimensional spaces and their coefficient vectors and respective norms. Then, some additional facts on the implementation of finite elements based on relation tables using the popular compressed sparse row (CSR) format are given. Also, typical condition number estimates of stiffness and mass matrices, the global matrix assembly from local element matrices are given as well. Finally, some basic introductory facts about stationary iterative methods, such as Gauss-Seidel and its symmetrized version are presented. The introductory material ends up with the smoothing property of the classical iterative methods and the main definition of two-grid iterative methods. From here on, the second part of the notes begins which deals with the various aspects of the principal TG and the numerous versions of the MG cycles. At the end, in part III, we briefly introduce algebraic versions of MG referred to as AMG, focusing on classes of AMG specialized for finite element matrices.

  8. Investigation on the Possible Relationship between Magnetic Pulsations and Earthquakes

    Science.gov (United States)

    Jusoh, M.; Liu, H.; Yumoto, K.; Uozumi, T.; Takla, E. M.; Yousif Suliman, M. E.; Kawano, H.; Yoshikawa, A.; Asillam, M.; Hashim, M.

    2012-12-01

    The sun is the main source of energy to the solar system, and it plays a major role in affecting the ionosphere, atmosphere and the earth surface. The connection between solar wind and the ground magnetic pulsations has been proven empirically by several researchers previously (H. J. Singer et al., 1977, E. W. Greenstadt, 1979, I. A. Ansari 2006 to name a few). In our preliminary statistical analysis on relationship between solar and seismic activities (Jusoh and Yumoto, 2011, Jusoh et al., 2012), we observed a high possibility of solar-terrestrial coupling. We observed high tendency of earthquakes to occur during lower phase solar cycles which significantly related with solar wind parameters (i.e solar wind dynamic pressure, speed and input energy). However a clear coupling mechanism was not established yet. To connect the solar impact on seismicity, we investigate the possibility of ground magnetic pulsations as one of the connecting agent. In our analysis, the recorded ground magnetic pulsations are analyzed at different ranges of ultra low frequency; Pc3 (22-100 mHz), Pc4 (6.7-22 mHz) and Pc5 (1.7-6.7 mHz) with the occurrence of local earthquake events at certain time periods. This analysis focuses at 2 different major seismic regions; north Japan (mid latitude) and north Sumatera, Indonesia (low latitude). Solar wind parameters were obtained from the Goddard Space Flight Center, NASA via the OMNIWeb Data Explorer and the Space Physics Data Facility. Earthquake events were extracted from the Advanced National Seismic System (ANSS) database. The localized Pc3-Pc5 magnetic pulsations data were extracted from Magnetic Data Acquisition System (MAGDAS)/Circum Pan Magnetic Network (CPMN) located at Ashibetsu (Japan); for earthquakes monitored at north Japan and Langkawi (Malaysia); for earthquakes observed at north Sumatera. This magnetometer arrays has established by International Center for Space Weather Science and Education, Kyushu University, Japan. From the

  9. A remark concerning Chandrasekhar's derivation of the pulsation equation for relativistic stars

    Energy Technology Data Exchange (ETDEWEB)

    Knutsen, Henning; Pedersen, Janne [Stavanger University, 4036 Stavanger (Norway)

    2007-01-15

    It is shown that Chandrasekhar gives some misleading comments concerning his method to derive the pulsation equation for relativistic stars. Strictly following his procedure and approximations, we find that this equation should contain an extra term which destroys the beauty and simplicity of the pulsation equation. However, using a better approximation, we find that just this extra term cancels, and the nice original version of the pulsation equation is correct after all.

  10. Live lecture versus video-recorded lecture: are students voting with their feet?

    Science.gov (United States)

    Cardall, Scott; Krupat, Edward; Ulrich, Michael

    2008-12-01

    In light of educators' concerns that lecture attendance in medical school has declined, the authors sought to assess students' perceptions, evaluations, and motivations concerning live lectures compared with accelerated, video-recorded lectures viewed online. The authors performed a cross-sectional survey study of all first- and second-year students at Harvard Medical School. Respondents answered questions regarding their lecture attendance; use of class and personal time; use of accelerated, video-recorded lectures; and reasons for viewing video-recorded and live lectures. Other questions asked students to compare how well live and video-recorded lectures satisfied learning goals. Of the 353 students who received questionnaires, 204 (58%) returned responses. Collectively, students indicated watching 57.2% of lectures live, 29.4% recorded, and 3.8% using both methods. All students have watched recorded lectures, and most (88.5%) have used video-accelerating technologies. When using accelerated, video-recorded lecture as opposed to attending lecture, students felt they were more likely to increase their speed of knowledge acquisition (79.3% of students), look up additional information (67.7%), stay focused (64.8%), and learn more (63.7%). Live attendance remains the predominant method for viewing lectures. However, students find accelerated, video-recorded lectures equally or more valuable. Although educators may be uncomfortable with the fundamental change in the learning process represented by video-recorded lecture use, students' responses indicate that their decisions to attend lectures or view recorded lectures are motivated primarily by a desire to satisfy their professional goals. A challenge remains for educators to incorporate technologies students find useful while creating an interactive learning culture.

  11. Improving Lecture Quality through Training in Public Speaking

    Science.gov (United States)

    Mowbray, Robert; Perry, Laura B.

    2015-01-01

    Lecturing is a common instructional format but poor lecturing skills can detract from students' learning experiences and outcomes. As lecturing is essentially a form of public communication, training in public speaking may improve lecture quality. Twelve university lecturers in Malaysia participated in a six-week public speaking skills training…

  12. Improving Lecture Quality through Training in Public Speaking

    Science.gov (United States)

    Mowbray, Robert; Perry, Laura B.

    2015-01-01

    Lecturing is a common instructional format but poor lecturing skills can detract from students' learning experiences and outcomes. As lecturing is essentially a form of public communication, training in public speaking may improve lecture quality. Twelve university lecturers in Malaysia participated in a six-week public speaking skills training…

  13. Mechanics lectures on theoretical physics

    CERN Document Server

    Sommerfeld, Arnold Johannes Wilhelm

    1952-01-01

    Mechanics: Lectures on Theoretical Physics, Volume I covers a general course on theoretical physics. The book discusses the mechanics of a particle; the mechanics of systems; the principle of virtual work; and d'alembert's principle. The text also describes oscillation problems; the kinematics, statics, and dynamics of a rigid body; the theory of relative motion; and the integral variational principles of mechanics. Lagrange's equations for generalized coordinates and the theory of Hamilton are also considered. Physicists, mathematicians, and students taking Physics courses will find the book

  14. Lectures on the Strominger system

    CERN Document Server

    Garcia-Fernandez, Mario

    2016-01-01

    These notes give an introduction to the Strominger system of partial differential equations, and are based on lectures given in September 2015 at the GEOQUANT School, held at the Institute of Mathematical Sciences (ICMAT) in Madrid. We describe the links with the theory of balanced metrics in hermitian geometry, the Hermite-Yang-Mills equations, and its origins in physics, that we illustrate with many examples. We also cover some recent developments in the moduli problem and the interrelation of the Strominger system with generalized geometry, via the cohomological notion of string class.

  15. Lectures on quantum field theory

    CERN Document Server

    Das, Ashok

    2008-01-01

    This book consists of the lectures for a two-semester course on quantum field theory, and as such is presented in a quite informal and personal manner. The course starts with relativistic one-particle systems, and develops the basics of quantum field theory with an analysis of the representations of the Poincaré group. Canonical quantization is carried out for scalar, fermion, Abelian and non-Abelian gauge theories. Covariant quantization of gauge theories is also carried out with a detailed description of the BRST symmetry. The Higgs phenomenon and the standard model of electroweak interactio

  16. Lectures on Logic and Computation

    DEFF Research Database (Denmark)

    foundational, introductory and advanced courses, as well as workshops, covering a wide variety of topics within the three areas of interest: Language and Computation, Language and Logic, and Logic and Computation. During two weeks, around 50 courses and 10 workshops are offered to the attendants, each of 1.......5 hours per day during a five days week, with up to seven parallel sessions. ESSLLI also includes a student session (papers and posters by students only, 1.5 hour per day during the two weeks) and four evening lectures by senior scientists in the covered areas. The 6 course notes were carefully reviewed...

  17. Lecture Notes in Quantum Mechanics

    CERN Document Server

    Cohen, D

    2006-01-01

    These lecture notes cover undergraduate textbook topics (e.g. as in Sakurai), and also additional advanced topics at the same level of presentation. In particular: EPR and Bell; Basic postulates; The probability matrix; Measurement theory; Entanglement; Quantum computation; Wigner-Weyl formalism; The adiabatic picture; Berry phase; Linear response theory; Kubo formula; Modern approach to scattering theory with mesoscopic orientation; Theory of the resolvent and the Green function; Gauge and Galilei Symmetries; Motion in magnetic field; Quantum Hall effect; Quantization of the electromagnetic field; Fock space formalism.

  18. The Relative Effects of Traditional Lectures and Guided Notes Lectures on University Student Test Scores

    Science.gov (United States)

    Williams, W. Larry; Weil, Timothy M.; Porter, James C. K.

    2012-01-01

    Guided notes were employed in two undergraduate Psychology courses involving 71 students. The study design utilized an alternating treatments format to compare Traditional Lectures with Guided Notes lectures. In one of the two courses, tests were administered after each class lecture, whereas the same type of test was administered at the beginning…

  19. The Use of Lecture Recordings in Higher Education: A Review of Institutional, Student, and Lecturer Issues

    Science.gov (United States)

    O'Callaghan, Frances V.; Neumann, David L.; Jones, Liz; Creed, Peter A.

    2017-01-01

    Web-based lecture technologies are being used increasingly in higher education. One widely-used method is the recording of lectures delivered during face-to-face teaching of on-campus courses. The recordings are subsequently made available to students on-line and have been variously referred to as lecture capture, video podcasts, and Lectopia. We…

  20. Forum: The Lecture and Student Learning. Lecture and Active Learning as a Dialectical Tension

    Science.gov (United States)

    Mallin, Irwin

    2017-01-01

    Lecture remains a valuable tool in the student learning toolbox--one that at its best helps students unpack what they read for class, place course material in context, and see how a subject matter expert solves problems. It may be useful to think of lecture and active learning as a dialectical tension satisfied by the interactive lecture. Just as…

  1. Online Lecture Recordings and Lecture Attendance: Investigating Student Preferences in a Large First Year Psychology Course

    Science.gov (United States)

    Yeung, Alexandra; Raju, Sadhana; Sharma, Manjula D.

    2016-01-01

    While blended learning has been around for some time, the interplay between lecture recordings, lecture attendance and grades needs further examination particularly for large cohorts of over 1,000 students in 500 seat lecture theatres. This paper reports on such an investigation with a cohort of 1,450 first year psychology students' who indicated…

  2. First Satellite Imaging of Auroral Pulsations by the Fast Auroral Imager on e-POP

    Science.gov (United States)

    Lui, A.; Cogger, L.; Howarth, A. D.; Yau, A. W.

    2015-12-01

    We report the first satellite imaging of auroral pulsations by the Fast Auroral Imager (FAI) onboard the Enhanced Polar Outflow Probe (e-POP) satellite. The near-infrared camera of FAI is capable of providing up to two auroral images per second, ideal for investigation of pulsating auroras. The auroral pulsations were observed within the auroral bulge formed during a substorm interval on 2014 February 19. This first satellite view of these pulsations from FAI reveals that (1) several pulsating auroral channels (PACs) occur within the auroral bulge, (2) periods of the intensity pulsations span over one decade within the auroral bulge, and (3) there is no apparent trend of longer pulsation periods associated with higher latitudes for these PACs. Although PACs resemble in some respect stable pulsating auroras reported previously but they have several important differences in characteristics.PACs are not embedded in or emerging from omega bands or torches and are located at significant distances from the equatorward boundary of the auroral oval, unlike the characteristics of stable pulsating auroras.

  3. Studies of the Long Secondary Periods in Pulsating Red Giants. II. Lower-Luminosity Stars

    CERN Document Server

    Percy, John R

    2016-01-01

    We have used AAVSO visual and photoelectric V data, and the AAVSO time-series package VSTAR and the Lomb-Scargle time-series algorithm to determine improved pulsation periods, "long secondary periods" (LSPs). and their amplitudes in 51 shorter-period pulsating red giants in the AAVSO photoelectric photometry program, and the AAVSO LPV (long period variable) binocular program. As is well known, radial pulsation becomes detectable in red giants at about spectral type M0, with periods of about 20 days. We find that the LSP phenomenon is also first detectable at about M0. Pulsation and LSP amplitudes increase from near zero to about 0.1 at pulsation periods of about 100 days. At longer periods, the pulsation amplitudes continue to increase, but the LSP amplitudes are generally between 0.1 and 0.2 on average. The ratios of LSP to pulsation period cluster around 5 and 10, presumably depending on whether the pulsation period is the fundamental or first overtone. The pulsation and LSP phase curves are generally close...

  4. New magnetic field measurements of beta Cephei stars and Slowly Pulsating B stars

    CERN Document Server

    Hubrig, S; De Cat, P; Schöller, M; Morel, T; Ilyin, I

    2009-01-01

    We present the results of the continuation of our magnetic survey with FORS1 at the VLT of a sample of B-type stars consisting of confirmed or candidate beta Cephei stars and Slowly Pulsating B stars. Roughly one third of the studied beta Cephei stars have detected magnetic fields. The fraction of magnetic Slowly Pulsating B and candidate Slowly Pulsating B stars is found to be higher, up to 50%. We find that the domains of magnetic and non-magnetic pulsating stars in the H-R diagram largely overlap, and no clear picture emerges as to the possible evolution of the magnetic field across the main sequence.

  5. White Dwarf Period Tables I. Pulsators with hydrogen-dominated atmospheres

    Science.gov (United States)

    Bognar, Zs.; Sodor, A.

    2016-09-01

    We aimed at collecting all known white dwarf pulsators with hydrogen-dominated atmospheres and list their main photometric and atmospheric parameters together with their pulsation periods and amplitudes observed at different epochs. For this purpose, we explored the pulsating white dwarf related literature with the systematic use of the SIMBAD and the NASA's Astrophysics Data System (ADS) databases. We summarized our results in four tables listing seven ZZ Ceti stars in detached white dwarf plus main-sequence binaries, seven extremely low-mass DA pulsators, three hot DAVs and 180 ZZ Ceti stars.

  6. White Dwarf Period Tables - I. Pulsators with hydrogen-dominated atmospheres

    CERN Document Server

    Bognár, Zs

    2016-01-01

    We aimed at collecting all known white dwarf pulsators with hydrogen-dominated atmospheres and list their main photometric and atmospheric parameters together with their pulsation periods and amplitudes observed at different epochs. For this purpose, we explored the pulsating white dwarf related literature with the systematic use of the SIMBAD and the NASA's Astrophysics Data System (ADS) databases. We summarized our results in four tables listing seven ZZ Ceti stars in detached white dwarf plus main-sequence binaries, seven extremely low-mass DA pulsators, three hot DAVs and 180 ZZ Ceti stars.

  7. Asteroseismology and forced oscillations of HD 209295, the first member of two classes of pulsating star

    CERN Document Server

    Handler, G; Shobbrook, R R; Koen, C; Bruch, A; Romero-Colmenero, E; Pamyatnykh, A A; Willems, B; Eyer, L; James, D J; Maas, T; Crause, L A

    2001-01-01

    We report the discovery of both intermediate-order gravity mode and low-order pressure mode pulsation in the same star, HD 209295. It is therefore both a gamma Doradus and a delta Scuti star, which makes it the first confirmed member of two classes of pulsating star. This object is located in a close binary system with an unknown, but likely degenerate companion in an eccentric orbit, and some of the gamma Doradus pulsation frequencies are exact integer multiples of the orbital frequency. We suggest that these pulsations are tidally excited. HD 209295 may be the progenitor of an intermediate-mass X-Ray binary.

  8. On the periodic variations of secondary cosmic rays and the geomagnetic Pc4 pulsations in BMAr

    Directory of Open Access Journals (Sweden)

    I. M. Martin

    Full Text Available In a set of balloon flights in the Brazilian magnetic anomaly region (BMAr short time periodic variations were observed, i.e. pulsation, of secondary charged and neutral particle fluxes, X- and -ray fluxes with amplitudes of about 2–4%. The pulsations are accompanied by the geomagnetic Pc4 pulsations and have similar periodicity. The phenomenon was observed over various local times and in quiet and disturbed magnetospheric conditions. One of the explanations of this effect, i.e. periodic variation of local cut-off rigidity, and following pulsations of primary and secondary cosmic ray intensity is suggested.

  9. Non-radiative relaxation of photoexcited chlorophylls: theoretical and experimental study

    Science.gov (United States)

    Bricker, William P.; Shenai, Prathamesh M.; Ghosh, Avishek; Liu, Zhengtang; Enriquez, Miriam Grace M.; Lambrev, Petar H.; Tan, Howe-Siang; Lo, Cynthia S.; Tretiak, Sergei; Fernandez-Alberti, Sebastian; Zhao, Yang

    2015-09-01

    Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis. We perform ultrafast transient absorption spectroscopy measurements, that reveal this internal conversion dynamics to be slightly slower in chlorophyll B than in chlorophyll A. Modeling this process with non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales. Even given smaller electron-vibrational couplings compared to common organic conjugated chromophores, these molecules are able to efficiently dissipate about 1 eV of electronic energy into heat on the timescale of around 200 fs. This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function.

  10. Non-radiation endoscopic retrograde cholangiopancreatography in the management of choledocholithiasis during pregnancy.

    Science.gov (United States)

    Wu, Wenming; Faigel, Douglas O; Sun, Gang; Yang, Yunsheng

    2014-11-01

    Gallstone diseases are common during pregnancy. In most cases, patients are asymptomatic and do not require any treatment. However, choledocholithiasis, cholangitis, and gallstone pancreatitis may potentially become life-threatening for both mother and fetus and often require urgent intervention. Although endoscopic retrograde cholangiopancreatography (ERCP) has become the standard technique for removing common bile duct stones, it is associated with ionizing radiation that could carry teratogenic risk. Non-radiation ERCP (NR-ERCP) is reported to be effective without incurring this risk. Two techniques have been described to confirm bile duct cannulation: bile aspiration and image guidance. With bile aspiration, biliary cannulation is confirmed by applying suction to the cannula to yield bile, thus confirming an intrabiliary position. Image guidance involves using ultrasound or direct visualization (choledochoscopy) to confirm selective biliary cannulation or duct clearance. Once cannulation is achieved, the stones are removed using standard ERCP techniques and tools. Case series and retrospective studies have reported success rates of up to 90% for NR-ERCP with complication rates similar to standard ERCP. Pregnancy outcomes are not adversely affected by NR-ERCP, but whether the avoidance of radiation carries benefit for the baby is unknown. Prospective comparative trials are lacking. NR-ERCP is technically demanding and should be attempted only by skilled biliary endoscopists in properly equipped and staffed health-care institutions, in a multidisciplinary setting. © 2014 The Authors. Digestive Endoscopy © 2014 Japan Gastroenterological Endoscopy Society.

  11. Resonant Transparency and Non-Trivial Non-Radiating Excitations in Toroidal Metamaterials

    Science.gov (United States)

    Fedotov, V. A.; Rogacheva, A. V.; Savinov, V.; Tsai, D. P.; Zheludev, N. I.

    2013-01-01

    Engaging strongly resonant interactions allows dramatic enhancement of functionalities of many electromagnetic devices. However, resonances can be dampened by Joule and radiation losses. While in many cases Joule losses may be minimized by the choice of constituting materials, controlling radiation losses is often a bigger problem. Recent solutions include the use of coupled radiant and sub-radiant modes yielding narrow asymmetric Fano resonances in a wide range of systems, from defect states in photonic crystals and optical waveguides with mesoscopic ring resonators to nanoscale plasmonic and metamaterial systems exhibiting interference effects akin to electromagnetically-induced transparency. Here we demonstrate theoretically and confirm experimentally a new mechanism of resonant electromagnetic transparency, which yields very narrow isolated symmetric Lorentzian transmission lines in toroidal metamaterials. It exploits the long sought non-trivial non-radiating charge-current excitation based on interfering electric and toroidal dipoles that was first proposed by Afanasiev and Stepanovsky in [J. Phys. A Math. Gen. 28, 4565 (1995)]. PMID:24132231

  12. FUSE Observations of the Cygnus Loop OVI Emission from a Nonradiative Shock

    CERN Document Server

    Sankrit, R; Sankrit, Ravi; Blair, William P.

    2001-01-01

    We present Far Ultraviolet Spectroscopic Explorer (FUSE) observations of a Balmer filament in the northeast region of the Cygnus Loop supernova remnant. The data consist of one spectrum obtained through the 30"x30" (LWRS) aperture and three spectra at adjacent positions obtained through the 4"x20" (MDRS) aperture. The nonradiative shocks in the region giving rise to these faint optical filaments produce strong OVI 1032,1038 emission, which is detected in all the spectra. The OVI emission is resolved by FUSE into a strong component centered at 0 km/s, and weaker components centered at +/- 140 km/s. The MDRS spectra allow us to study the variation of OVI emission in the post-shock structure. We find that the zero velocity emission is associated directly with the Balmer filament shock, while the high velocity emission comes from a more uniformly distributed component elsewhere along the line of sight. We also find that the shocks producing the emission at +/- 140 km/s have velocities between 180 km/s and 220 km/...

  13. Non-radiative relaxation of photoexcited chlorophylls: theoretical and experimental study.

    Science.gov (United States)

    Bricker, William P; Shenai, Prathamesh M; Ghosh, Avishek; Liu, Zhengtang; Enriquez, Miriam Grace M; Lambrev, Petar H; Tan, Howe-Siang; Lo, Cynthia S; Tretiak, Sergei; Fernandez-Alberti, Sebastian; Zhao, Yang

    2015-09-08

    Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis. We perform ultrafast transient absorption spectroscopy measurements, that reveal this internal conversion dynamics to be slightly slower in chlorophyll B than in chlorophyll A. Modeling this process with non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales. Even given smaller electron-vibrational couplings compared to common organic conjugated chromophores, these molecules are able to efficiently dissipate about 1 eV of electronic energy into heat on the timescale of around 200 fs. This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function.

  14. Energy efficiency in Spanish wastewater treatment plants: a non-radial DEA approach.

    Science.gov (United States)

    Hernández-Sancho, F; Molinos-Senante, M; Sala-Garrido, R

    2011-06-15

    Wastewater treatment plants (WWTPs) are energy-intensive facilities. Thus, reducing their carbon footprint is particularly important, both economically and environmentally. Knowing the real operating energy efficiency of WWTPs is the starting point for any energy-saving initiative. In this article, we applied a non-radial Data Envelopment Analysis (DEA) methodology to calculate energy efficiency indices for sampling of WWTPs located in Spain. In a second stage analysis, we examined the operating variables contributing to differences in energy efficiency among plants. It is verified that energy efficiencies of the analyzed WWTPs were quite low, with only 10% of them being efficient. We found that plant size, quantity of organic matter removed, and type of bioreactor aeration were significant variables in explaining energy efficiency differences. In contrast, age of the plant was not a determining factor in energy consumption. Lastly, we quantified the potential savings, both in economic terms and in terms of CO(2) emissions, that could be expected from an improvement in energy efficiency of WWTPs.

  15. Origin and implications of non-radial Imbrium Sculpture on the Moon

    Science.gov (United States)

    Schultz, Peter H.; Crawford, David A.

    2016-07-01

    Rimmed grooves, lineations and elongate craters around Mare Imbrium shape much of the nearside Moon. This pattern was coined the Imbrium Sculpture, and it was originally argued that it must have been formed by a giant oblique (~30°) impact, a conclusion echoed by later studies. Some investigators, however, noticed that many elements of the Imbrium Sculpture are not radial to Imbrium, thereby implicating an endogenic or structural origin. Here we use these non-radial trends to conclude that the Imbrium impactor was a proto-planet (half the diameter of Vesta), once part of a population of large proto-planets in the asteroid belt. Such independent constraints on the sizes of the Imbrium and other basin-forming impactors markedly increase estimates for the mass in the asteroid belt before depletion caused by the orbital migration of Jupiter and Saturn. Moreover, laboratory impact experiments, shock physics codes and the groove widths indicate that multiple fragments (up to 2% of the initial diameter) from each oblique basin-forming impactor, such as the one that formed Imbrium, should have survived planetary collisions and contributed to the heavy impact bombardment between 4.3 and 3.8 billion years ago.

  16. Lectures on Geophysical Fluid Dynamics

    Science.gov (United States)

    Samelson, Roger M.

    The fluid kaleidoscope of the Earth's ocean and atmosphere churns and sparkles with jets, gyres, eddies, waves, streams, and cyclones. These vast circulations, essential elements of the physical environment that support human life, are given a special character by the Earth's rotation and by their confinement to a shallow surficial layer, thin relative to the solid Earth in roughly the same proportion as an apple skin is to an apple. Geophysical fluid dynamics exploits this special character to develop a unified theoretical approach to the physics of the ocean and atmosphere.With Lectures on Geophysical Fluid Dynamics, Rick Salmon has added an insightful and provocative volume to the handful of authoritative texts currently available on the subject. The book is intended for first-year graduate students, but advanced students and researchers also will find it useful. It is divided into seven chapters, the first four of these adapted from course lectures. The book is well written and presents a fresh and stimulating perspective that complements existing texts. It would serve equally well either as the main text for a core graduate curriculum or as a supplementary resource for students and teachers seeking new approaches to both classical and contemporary problems. A lively set of footnotes contains many references to very recent work. The printing is attractive, the binding is of high quality, and typographical errors are few.

  17. Lectures on Dark Matter Physics

    Science.gov (United States)

    Lisanti, Mariangela

    Rotation curve measurements from the 1970s provided the first strong indication that a significant fraction of matter in the Universe is non-baryonic. In the intervening years, a tremendous amount of progress has been made on both the theoretical and experimental fronts in the search for this missing matter, which we now know constitutes nearly 85% of the Universe's matter density. These series of lectures provide an introduction to the basics of dark matter physics. They are geared for the advanced undergraduate or graduate student interested in pursuing research in high-energy physics. The primary goal is to build an understanding of how observations constrain the assumptions that can be made about the astro- and particle physics properties of dark matter. The lectures begin by delineating the basic assumptions that can be inferred about dark matter from rotation curves. A detailed discussion of thermal dark matter follows, motivating Weakly Interacting Massive Particles, as well as lighter-mass alternatives. As an application of these concepts, the phenomenology of direct and indirect detection experiments is discussed in detail.

  18. Web Lectures - ATLAS Overview Week

    CERN Multimedia

    Tushar Bhatnagar; Jeremy Herr; Mitch McLachlan; Homer A. Neal

    2007-01-01

    ATLAS Web Archives Web Archives of the ATLAS Overview Week in Glasgow are now available from the University of Michigan portal here. Archives of ATLAS Plenary Sessions, Workshops, Meetings, and Tutorials recorded over the past two years are available via the University of Michigan Lecture Portal. Other recent additions include the ROOT Workshop held at CERN on March 26-27, the Physics Analysis Tools Workshop held in Bergen, Norway on April 23-27, and the CTEQ Workshop: "Physics at the LHC: Early Challenges" held at Michigan State University on May 14-15. Viewing requires a standard Web browser with RealPlayer plug-in (included in most browsers automatically) and works on any major platform. Lectures can be viewed directly over the Web or downloaded locally. In addition, you will find access to a variety of general tutorials and events via the portal. Feedback & Suggestions Welcome Suggestions for events or tutorials to record in 2007, as well as feedback on existing archives, is always welcome...

  19. Aging mathematical model of InGaN/GaN LEDs based on non-radiative recombination

    Science.gov (United States)

    Xu, Linwang; Qian, Keyuan

    2017-08-01

    This paper proposes a new aging mathematical model for InGaN/GaN-based light-emitting diodes (LEDs) based on non-radiative recombination. Light attenuation is an important index of the performance of LEDs, Arrhenius model as the main aging mathematical model of light attenuation is poorly targeted and cannot reflect the physical significance. Based on the physical theory of deep level defects and non-radiation recombination centers, we analyze the aging mechanism of LED chips and then establish the aging mathematical model. Meanwhile, a batch of GaN-based blue LED chips are selected to conduct accelerated life tests with constant current stresses, and the experimental data is obtained to verify the new model. The result shows that compared with the traditional Arrhenius model, the new model has many advantages such as more accurate, strong pertinence and obvious physical meaning.

  20. Influencing factors on lecture attendance at a tertiary institution ...

    African Journals Online (AJOL)

    The tendency towards decreasing class attendance by students is a concern for ... Various factors contribute to the motivation of students, which in turn directly or ... lecture attendance, lecture/r quality as well as reasons for attending classes.

  1. Full wave analysis of non-radiative dielectric waveguide modulator for the determination of electrical equivalent circuit

    Indian Academy of Sciences (India)

    N P Pathak; A Basu; S K Koul

    2008-07-01

    This paper reports the determination of electrical equivalent circuit of ON/OFF modulator in non-radiative dielectric (NRD) guide configurations at Ka-band. Schottky barrier mixer diode is used to realize this modulator and its characteristics are determined experimentally using vector network analyzer. Full wave FEM simulator HFSS is used to determine an equivalent circuit for the mounted diode and modulator in ON and OFF states. This equivalent circuit is used to qualitatively explain the experimental characteristics of modulator.

  2. Full-band structure modeling of the radiative and non-radiative properties of semiconductor materials and devices (Presentation Recording)

    Science.gov (United States)

    Bellotti, Enrico; Wen, Hanqing; Pinkie, Benjamin; Matsubara, Masahiko; Bertazzi, Francesco

    2015-08-01

    Understanding the radiative and non-radiative properties of semiconductor materials is a prerequisite for optimizing the performance of existing light emitters and detectors and for developing new device architectures based on novel materials. Due to the ever increasing complexity of novel semiconductor systems and their relative technological immaturity, it is essential to have design tools and simulation strategies that include the details of the microscopic physics and their dependence on the macroscopic (continuum) variables in the macroscopic device models. Towards this end, we have developed a robust full-band structure based approach that can be used to study the intrinsic material radiative and non-radiative properties and evaluate the same characteristics of low-dimensional device structures. A parallel effort is being carried out to model the effect of substrate driven stress/strain and material quality (dislocations and defects) on microscopic quantities such as non-radiative recombination rate. Using this modeling approach, we have extensively studied the radiative and non-radiative properties of both elemental (Si and Ge) and compound semiconductors (HgCdTe, InGaAs, InAsSb and InGaN). In this work we outline the details of the modelling approach, specifically the challenges and advantages related to the use of the full-band description of the material electronic structure. We will present a detailed comparison of the radiative and Auger recombination rates as a function of temperature and doping for HgCdTe and InAsSb that are two important materials for infrared detectors and emitters. Furthermore we will discuss the role of non-radiatiave Auger recombination processes in explaining the performance of light emitter diodes. Finally we will present the extension of the model to low dimensional structures employed in a number of light emitter and detector structures.

  3. Short lecture series in sustainable product development

    DEFF Research Database (Denmark)

    McAloone, Tim C.

    2005-01-01

    Three lectures in sustainable product development models, methods and mindsets should give insight into the way of thinking about the environment when developing products. The first two lectures will guide you through: . Environmental problems in industry & life-cycle thinking . Professional...... methods for analysing and changing products’ environmental profiles . Sustainability as a driver for innovation...

  4. The Role of Lecturers and Inclusive Education

    Science.gov (United States)

    Molina, Víctor M.; Perera Rodríguez, Víctor Hugo; Melero Aguilar, Noelia; Cotán Fernández, Almudena; Moriña, Anabel

    2016-01-01

    This paper presents an analysis of how lecturers respond to students with disabilities, the initial question being: do lecturers aid or hinder students? Findings pertain to a broader research project employing a non-usual research methodology in higher education research and students with disabilities: the biographical-narrative methodology. The…

  5. The Role of Lecturers and Inclusive Education

    Science.gov (United States)

    Molina, Víctor M.; Perera Rodríguez, Víctor Hugo; Melero Aguilar, Noelia; Cotán Fernández, Almudena; Moriña, Anabel

    2016-01-01

    This paper presents an analysis of how lecturers respond to students with disabilities, the initial question being: do lecturers aid or hinder students? Findings pertain to a broader research project employing a non-usual research methodology in higher education research and students with disabilities: the biographical-narrative methodology. The…

  6. In Defense of the Populist Lecture

    Science.gov (United States)

    Schrad, Mark Lawrence

    2010-01-01

    Information and communication technology (ICT) programs like Microsoft PowerPoint and Apple Keynote have become the norm for large university lecture classes, but their record in terms of student engagement and active learning is mixed at best. Here, the author presents the merits of a "populist" lecture style that takes full advantage of the…

  7. Lectures on Composite Materials for Aircraft Structures,

    Science.gov (United States)

    1982-10-01

    lectures are related to structural applications of composites . In Lecture 7, the basic theory that is needed for composite structural analysis is...which composites have been taken up for aeronautical applications. Several specific applications of composites in aircraft structures am described in

  8. Short lecture series in sustainable product development

    DEFF Research Database (Denmark)

    McAloone, Tim C.

    2005-01-01

    Three lectures in sustainable product development models, methods and mindsets should give insight into the way of thinking about the environment when developing products. The first two lectures will guide you through: . Environmental problems in industry & life-cycle thinking . Professional...

  9. Lecture Notes in Statistics. 3rd Semester

    DEFF Research Database (Denmark)

    The lecture note is prepared to meet the requirements of the curriculum for the 3rd smester course in statistics at the Aarhus School of Business.......The lecture note is prepared to meet the requirements of the curriculum for the 3rd smester course in statistics at the Aarhus School of Business....

  10. Lecture 11: Some More Suggestions and Remarks

    Science.gov (United States)

    Montessori, Maria

    2016-01-01

    This lecture discusses how the careful preparation of the observer, control of conditions, and precise use of materials will allow the child to "be free to manifest the phenomena which we wish to observe." This lecture was delivered at the International Training Course, London, 1921. [Reprinted from "AMI Communications" (2008).

  11. Sir Nevill F. Mott Lecture Award

    NARCIS (Netherlands)

    Schropp, R.E.I.

    2010-01-01

    The Mott Lecture is awarded to scientists working in the tradition of Nobel laureate Sir Nevill F. Mott, with exceptional contributions to the fields important to the ICANS conference. The ICANS23 Mott Lecture was awarded to Prof. Dr. Sigurd Wagner of Princeton University. He is recognized for his g

  12. Students' Perception of Live Lectures' Inherent Disadvantages

    Science.gov (United States)

    Petrovic, Juraj; Pale, Predrag

    2015-01-01

    This paper aims to provide insight into various properties of live lectures from the perspective of sophomore engineering students. In an anonymous online survey conducted at the Faculty of Electrical Engineering and Computing, University of Zagreb, we investigated students' opinions regarding lecture attendance, inherent disadvantages of live…

  13. A Case Against Mandatory Lecture Attendance.

    Science.gov (United States)

    Hyde, Richard M.; Flournoy, D. J.

    1986-01-01

    Students' lecture attendance, course grades, class rank at the end of the first year of medical school, and scores on the NBME Part I examinations were correlated. The data suggest that a significant number of students who did not attend lectures did well academically. (MLW)

  14. Lecture Notes in Statistics. 3rd Semester

    DEFF Research Database (Denmark)

    The lecture note is prepared to meet the requirements of the curriculum for the 3rd smester course in statistics at the Aarhus School of Business.......The lecture note is prepared to meet the requirements of the curriculum for the 3rd smester course in statistics at the Aarhus School of Business....

  15. Richard Feynman's popular lectures on quantum electrodynamics: The 1979 Robb lectures at Auckland University

    Science.gov (United States)

    Dudley, J. M.; Kwan, A. M.

    1996-06-01

    The subject of quantum electrodynamics (QED) was the subject of QED—The Strange Theory of Light and Matter, the popular book by Richard Feynman which was published by Princeton University Press in 1985. On p. 1, Feynman makes passing reference to the fact that the book is based on a series of general lectures on QED which were, however, first delivered in New Zealand. At Auckland University, these lectures were delivered in 1979, as the Sir Douglas Robb lectures, and videotapes of the lectures are held by the Auckland University Physics Department. We have carried out a detailed examination of these videotapes, and we discuss here the major differences between the original Auckland lectures and the published version. We use selected quotations from the lectures to show that the original lectures provide additional insight into Feynman's character, and have great educational value.

  16. Anthropocentric Video Segmentation for Lecture Webcasts

    Directory of Open Access Journals (Sweden)

    Raul Rojas

    2008-03-01

    Full Text Available Many lecture recording and presentation systems transmit slides or chalkboard content along with a small video of the instructor. As a result, two areas of the screen are competing for the viewer's attention, causing the widely known split-attention effect. Face and body gestures, such as pointing, do not appear in the context of the slides or the board. To eliminate this problem, this article proposes to extract the lecturer from the video stream and paste his or her image onto the board or slide image. As a result, the lecturer acting in front of the board or slides becomes the center of attention. The entire lecture presentation becomes more human-centered. This article presents both an analysis of the underlying psychological problems and an explanation of signal processing techniques that are applied in a concrete system. The presented algorithm is able to extract and overlay the lecturer online and in real time at full video resolution.

  17. Lectures on Foliation Dynamics: Barcelona 2010

    CERN Document Server

    Hurder, Steven

    2011-01-01

    This survey is based on a series of five lectures, given May 3--7, 2010, at the Centre de Recerca Matematica, Barcelona. The goal of the lectures was to present aspects of the theory of foliation dynamical systems which have particular importance for the classification of foliations of compact manifolds. The lectures emphasized intuitive concepts and informal discussion, while taking the reader into topics of active research in this subject. These notes update and expand on the lectures, and include more recent progress. This article also includes an extensive set of references, as well as highlighting many open questions and problems. A set of "homework problems" is also included, one for each day of lecture.

  18. Anthropocentric Video Segmentation for Lecture Webcasts

    Directory of Open Access Journals (Sweden)

    Rojas Raul

    2007-01-01

    Full Text Available Abstract Many lecture recording and presentation systems transmit slides or chalkboard content along with a small video of the instructor. As a result, two areas of the screen are competing for the viewer's attention, causing the widely known split-attention effect. Face and body gestures, such as pointing, do not appear in the context of the slides or the board. To eliminate this problem, this article proposes to extract the lecturer from the video stream and paste his or her image onto the board or slide image. As a result, the lecturer acting in front of the board or slides becomes the center of attention. The entire lecture presentation becomes more human-centered. This article presents both an analysis of the underlying psychological problems and an explanation of signal processing techniques that are applied in a concrete system. The presented algorithm is able to extract and overlay the lecturer online and in real time at full video resolution.

  19. Appraisal of electromagnetic induction effects on magnetic pulsation studies

    Directory of Open Access Journals (Sweden)

    B. R. Arora

    Full Text Available The quantification of wave polarization characteristics of ULF waves from the geomagnetic field variations is done under ‘a priori’ assumption that fields of internal induced currents are in-phase with the external inducing fields. Such approximation is invalidated in the regions marked by large lateral conductivity variations that perturb the flow pattern of induced currents. The amplitude and phase changes that these perturbations produce, in the resultant fields at the Earth’s surface, make determination of polarization and phase of the oscillating external signals problematic. In this paper, with the help of a classical Pc5 magnetic pulsation event of 24 March 1991, recorded by dense network of magnetometers in the equatorial belt of Brazil, we document the nature and extent of the possible influence of anomalous induction effects in the wave polarization of ULF waves. The presence of anomalous induction effects at selected sites lead to an over estimation of the equatorial enhancement at pulsation period and also suggest changes in the azimuth of ULF waves as they propagate through the equatorial electrojet. Through numerical calculations, it is shown that anomalous horizontal fields, that result from induction in the lateral conductivity distribution in the study region, vary in magnitude and phase with the polarization of external source field. Essentially, the induction response is also a function of the period of external inducing source field. It is further shown that when anomalous induction fields corresponding to the magnitude and polarization of the 24 March 1991 pulsation event are eliminated from observed fields, corrected amplitude in the X and Y horizontal components allows for true characterisation of ULF wave parameters.

    Key words. Geomagnetism and paleomagnetism (geomagnetic induction – Ionosphere (equatorial ionosphere – Magnetospheric physics (magnetosphere-ionosphere interactions

  20. DARK STARS: IMPROVED MODELS AND FIRST PULSATION RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Rindler-Daller, T.; Freese, K. [Department of Physics and Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109 (United States); Montgomery, M. H.; Winget, D. E. [Department of Astronomy, McDonald Observatory and Texas Cosmology Center, University of Texas, Austin, TX 78712 (United States); Paxton, B. [Kavli Insitute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States)

    2015-02-01

    We use the stellar evolution code MESA to study dark stars (DSs). DSs, which are powered by dark matter (DM) self-annihilation rather than by nuclear fusion, may be the first stars to form in the universe. We compute stellar models for accreting DSs with masses up to 10{sup 6} M {sub ☉}. The heating due to DM annihilation is self-consistently included, assuming extended adiabatic contraction of DM within the minihalos in which DSs form. We find remarkably good overall agreement with previous models, which assumed polytropic interiors. There are some differences in the details, with positive implications for observability. We found that, in the mass range of 10{sup 4}-10{sup 5} M {sub ☉}, our DSs are hotter by a factor of 1.5 than those in Freese et al., are smaller in radius by a factor of 0.6, denser by a factor of three to four, and more luminous by a factor of two. Our models also confirm previous results, according to which supermassive DSs are very well approximated by (n = 3)-polytropes. We also perform a first study of DS pulsations. Our DS models have pulsation modes with timescales ranging from less than a day to more than two years in their rest frames, at z ∼ 15, depending on DM particle mass and overtone number. Such pulsations may someday be used to identify bright, cool objects uniquely as DSs; if properly calibrated, they might, in principle, also supply novel standard candles for cosmological studies.

  1. Discovery of a new PG 1159 (GW Vir) pulsator

    Science.gov (United States)

    Kepler, S. O.; Fraga, Luciano; Winget, Don Earl; Bell, Keaton; Córsico, Alejandro H.; Werner, Klaus

    2014-08-01

    We report the discovery of pulsations in the spectroscopic PG 1159 type pre-white dwarf SDSS J075415.12 + 085232.18. Analysis of the spectrum by Werner et al. indicated Teff = 120 000 ± 10 000 K, log g = 7.0 ± 0.3, mass {M}=0.52 ± 0.02 M_{⊙}, C/He = 0.33 by number. We obtained time series images with the SOAR 4.1 m telescope and 2.1 m Otto Struve telescope at McDonald Observatory and show the star is also a variable PG 1159 type star, with dominant period of 525 s.

  2. Discovery of a new PG1159 (GW Vir) Pulsator

    CERN Document Server

    Kepler, S O; Winget, Don Earl; Bell, Keaton; Corsico, Alejandro H; Werner, Klaus

    2014-01-01

    We report the discovery of pulsations in the spectroscopic PG 1159 type pre-white dwarf SDSS J075415.12+085232.18. Analysis of the spectrum by Werner, Rauch and Kepler (2014) indicated Teff=120 000+/-10 000 K, log g=7.0+/-0.3, mass M=0.52+/-0.02 Msun, C/He=0.33 by number. We obtained time-series images with the SOAR 4.1 m telescope and 2.1 m Otto Struve telescope at McDonald Observatory and show the star is also a variable PG 1159 type star, with dominant period of 525 s.

  3. Modeling KIC10684673 and KIC12216817 as Single Pulsating Variables

    CERN Document Server

    Turner, Garrison

    2016-01-01

    The raw light curves of both KIC 10684673 and KIC 12216817 show variability. Both are listed in the Kepler Eclipsing Binary Catalog (hereafter KEBC), however both are flagged as uncertain in nature. In the present study we show their light curves can be modeled by considering each target as a single, multi-modal delta Scuti pulsator. While this does not exclude the possibility of eclipsing systems, we argue, while spectroscopy on the systems is still lacking, the delta Scuti model is a simpler explanation and therefore more probable.

  4. DYNAMIC STABILITY OF AXIALLY MOVING VISCOELASTIC BEAMS WITH PULSATING SPEED

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-dong; CHEN Li-qun

    2005-01-01

    Parametric vibration of an axially moving, elastic, tensioned beam with pulsating speed was investigated in the vicinity of subharmonic and combination resonance. The method of averaging was used to yield a set of autonomous equations when the parametric excitation frequency is twice or the combination of the natural frequencies. Instability boundaries were presented in the plane of parametric frequency and amplitude. The analytical results were numerically verified. The effects of the viscoelastic damping, steady speed and tension on the instability boundaries were numerically demonstrated. It is found that the viscoelastic damping decreases the instability regions and the steady speed and the tension make the instability region drift along the frequency axis.

  5. Lecture notes on diophantine analysis

    CERN Document Server

    Zannier, Umberto

    2014-01-01

    These lecture notes originate from a course delivered at the Scuola Normale in Pisa in 2006. Generally speaking, the prerequisites do not go beyond basic mathematical material and are accessible to many undergraduates. The contents mainly concern diophantine problems on affine curves, in practice describing the integer solutions of equations in two variables. This case historically suggested some major ideas for more general problems. Starting with linear and quadratic equations, the important connections with Diophantine Approximation are presented and Thue's celebrated results are proved in full detail. In later chapters more modern issues on heights of algebraic points are dealt with, and applied to a sharp quantitative treatment of the unit equation. The book also contains several Supplements, hinted exercises and an Appendix on recent work on heights.

  6. Lectures on Gravity and Entanglement

    CERN Document Server

    Van Raamsdonk, Mark

    2016-01-01

    The AdS/CFT correspondence provides quantum theories of gravity in which spacetime and gravitational physics emerge from ordinary non-gravitational quantum systems with many degrees of freedom. Recent work in this context has uncovered fascinating connections between quantum information theory and quantum gravity, suggesting that spacetime geometry is directly related to the entanglement structure of the underlying quantum mechanical degrees of freedom and that aspects of spacetime dynamics (gravitation) can be understood from basic quantum information theoretic constraints. In these notes, we provide an elementary introduction to these developments, suitable for readers with some background in general relativity and quantum field theory. The notes are based on lectures given at the CERN Spring School 2014, the Jerusalem Winter School 2014, the TASI Summer School 2015, and the Trieste Spring School 2015.

  7. Academic Training Lecture Regular Programme

    CERN Multimedia

    2012-01-01

    Ultra-High Energy Cosmic Rays (1/3), by Maria Teresa Dova (Universidad Nacional de La Plata & CONICET, Argentina).   Wednesday, April 25, 2012 from 11:00 to 12:00 (Europe/Zurich) at CERN (500-1-001 - Main Auditorium ) The origin of the highest energy cosmic rays (UHECR) with energies above 1000 TeV, is still unknown. The discovery of their sources will reveal the engines of the most energetic astrophysical accelerators in the universe. In these lectures we present the recent observational results from HiRes, Telescope Array and Pierre Auger Observatory as well as (some of) the possible astrophysical origins of UHECR. These experiments deal with particle interactions at energies orders of magnitude higher than achieved in terrestrial accelerators. Organised by Luis Alvarez-Gaume.

  8. Lecture notes: Astrophysical fluid dynamics

    CERN Document Server

    Ogilvie, Gordon I

    2016-01-01

    These lecture notes and example problems are based on a course given at the University of Cambridge in Part III of the Mathematical Tripos. Fluid dynamics is involved in a very wide range of astrophysical phenomena, such as the formation and internal dynamics of stars and giant planets, the workings of jets and accretion discs around stars and black holes, and the dynamics of the expanding Universe. Effects that can be important in astrophysical fluids include compressibility, self-gravitation and the dynamical influence of the magnetic field that is 'frozen in' to a highly conducting plasma. The basic models introduced and applied in this course are Newtonian gas dynamics and magnetohydrodynamics (MHD) for an ideal compressible fluid. The mathematical structure of the governing equations and the associated conservation laws are explored in some detail because of their importance for both analytical and numerical methods of solution, as well as for physical interpretation. Linear and nonlinear waves, includin...

  9. Collide@CERN - public lecture

    CERN Multimedia

    2012-01-01

    CERN, the Republic and Canton of Geneva and the City of Geneva are delighted to invite you to a public lecture by Gilles Jobin, first winner of the Collide@CERN Geneva Dance and Performance Artist-in-residence Prize, and his CERN inspiration partner, Joao Pequenao. They will present their work in dance and science at the Globe of Science and Innovation on Wednesday, 23 May 2012 at 7 p.m. (doors open at 6.30 p.m.).   
                                                  Programme 19:00 Opening address by - Professor Rolf-Dieter Heuer, CERN Director-General, - Ariane Koek...

  10. Lecture 3: Web Application Security

    CERN Document Server

    CERN. Geneva

    2013-01-01

    Computer security has been an increasing concern for IT professionals for a number of years, yet despite all the efforts, computer systems and networks remain highly vulnerable to attacks of different kinds. Design flaws and security bugs in the underlying software are among the main reasons for this. This lecture focuses on security aspects of Web application development. Various vulnerabilities typical to web applications (such as Cross-site scripting, SQL injection, cross-site request forgery etc.) are introduced and discussed. Sebastian Lopienski is CERN’s deputy Computer Security Officer. He works on security strategy and policies; offers internal consultancy and audit services; develops and maintains security tools for vulnerability assessment and intrusion detection; provides training and awareness raising; and does incident investigation and response. During his work at CERN since 2001, Sebastian has had various assignments, including designing and developing software to manage and support servic...

  11. Lecture notes for criticality safety

    Science.gov (United States)

    Fullwood, R.

    1992-03-01

    These lecture notes for criticality safety are prepared for the training of Department of Energy supervisory, project management, and administrative staff. Technical training and basic mathematics are assumed. The notes are designed for a two-day course, taught by two lecturers. Video tapes may be used at the options of the instructors. The notes provide all the materials that are necessary but outside reading will assist in the fullest understanding. The course begins with a nuclear physics overview. The reader is led from the macroscopic world into the microscopic world of atoms and the elementary particles that constitute atoms. The particles, their masses and sizes and properties associated with radioactive decay and fission are introduced along with Einstein's mass-energy equivalence. Radioactive decay, nuclear reactions, radiation penetration, shielding and health-effects are discussed to understand protection in case of a criticality accident. Fission, the fission products, particles and energy released are presented to appreciate the dangers of criticality. Nuclear cross sections are introduced to understand the effectiveness of slow neutrons to produce fission. Chain reactors are presented as an economy; effective use of the neutrons from fission leads to more fission resulting in a power reactor or a criticality excursion. The six-factor formula is presented for managing the neutron budget. This leads to concepts of material and geometric buckling which are used in simple calculations to assure safety from criticality. Experimental measurements and computer code calculations of criticality are discussed. To emphasize the reality, historical criticality accidents are presented in a table with major ones discussed to provide lessons-learned. Finally, standards, NRC guides and regulations, and DOE orders relating to criticality protection are presented.

  12. Lecture notes for criticality safety

    Energy Technology Data Exchange (ETDEWEB)

    Fullwood, R.

    1992-03-01

    These lecture notes for criticality safety are prepared for the training of Department of Energy supervisory, project management, and administrative staff. Technical training and basic mathematics are assumed. The notes are designed for a two-day course, taught by two lecturers. Video tapes may be used at the options of the instructors. The notes provide all the materials that are necessary but outside reading will assist in the fullest understanding. The course begins with a nuclear physics overview. The reader is led from the macroscopic world into the microscopic world of atoms and the elementary particles that constitute atoms. The particles, their masses and sizes and properties associated with radioactive decay and fission are introduced along with Einstein`s mass-energy equivalence. Radioactive decay, nuclear reactions, radiation penetration, shielding and health-effects are discussed to understand protection in case of a criticality accident. Fission, the fission products, particles and energy released are presented to appreciate the dangers of criticality. Nuclear cross sections are introduced to understand the effectiveness of slow neutrons to produce fission. Chain reactors are presented as an economy; effective use of the neutrons from fission leads to more fission resulting in a power reactor or a criticality excursion. The six-factor formula is presented for managing the neutron budget. This leads to concepts of material and geometric buckling which are used in simple calculations to assure safety from criticality. Experimental measurements and computer code calculations of criticality are discussed. To emphasize the reality, historical criticality accidents are presented in a table with major ones discussed to provide lessons-learned. Finally, standards, NRC guides and regulations, and DOE orders relating to criticality protection are presented.

  13. Lecture notes for criticality safety

    Energy Technology Data Exchange (ETDEWEB)

    Fullwood, R.

    1992-03-01

    These lecture notes for criticality safety are prepared for the training of Department of Energy supervisory, project management, and administrative staff. Technical training and basic mathematics are assumed. The notes are designed for a two-day course, taught by two lecturers. Video tapes may be used at the options of the instructors. The notes provide all the materials that are necessary but outside reading will assist in the fullest understanding. The course begins with a nuclear physics overview. The reader is led from the macroscopic world into the microscopic world of atoms and the elementary particles that constitute atoms. The particles, their masses and sizes and properties associated with radioactive decay and fission are introduced along with Einstein's mass-energy equivalence. Radioactive decay, nuclear reactions, radiation penetration, shielding and health-effects are discussed to understand protection in case of a criticality accident. Fission, the fission products, particles and energy released are presented to appreciate the dangers of criticality. Nuclear cross sections are introduced to understand the effectiveness of slow neutrons to produce fission. Chain reactors are presented as an economy; effective use of the neutrons from fission leads to more fission resulting in a power reactor or a criticality excursion. The six-factor formula is presented for managing the neutron budget. This leads to concepts of material and geometric buckling which are used in simple calculations to assure safety from criticality. Experimental measurements and computer code calculations of criticality are discussed. To emphasize the reality, historical criticality accidents are presented in a table with major ones discussed to provide lessons-learned. Finally, standards, NRC guides and regulations, and DOE orders relating to criticality protection are presented.

  14. Pulsation Solution to the Equation of Earth's Gravitational Field (Main Outcome)

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Using d'Alembert equation as the approximation of Einstein's equation, a solution is given in this paper to the time-dependent gravitational equation of the Earth in consideration of the Earth's features, which describes the characteristics of pulsation of the Earth and the structures of spherical layers of its interior, thus providing a theoretical basis for establishing the idea of mantle pulsation.

  15. Observation of quasi-periodic pulsations in the solar flare SF 900610

    DEFF Research Database (Denmark)

    Terekhov, O.V.; Shevchenko, A.V.; Kuz'min, A.G.;

    2002-01-01

    A quasi-periodic component was found at the maximum of the X-ray light curve for the June 10, 1990 solar flare detected by the Granat observatory. The pulsation period was 143.2 +/- 0.8 s. The intensity of the pulsing component is not constant; the maximum amplitude of the pulsations is similar t...

  16. Ultracam Photometry of Pulsating Subdwarf B Stars rf B Binaries in the Edinburgh-Cape Survey

    NARCIS (Netherlands)

    Jeffery, C.S.; Aerts, C.C.; Dhillon, V.S.; Marsh, T.R.; Morales-Rueda, L.; Maxted, P.F.L.; Kilkenny, D.; O'Donoghue, D.

    2006-01-01

    High-speed multicolor photometry with ultracam promises to revolutionize the study of pulsating subdwarf B stars. As well as providing high S/N light curves with excellent temporal resolution, color amplitude ratios may be used to discriminate between different pulsation modes. In this paper we revi

  17. On the use of hot-wire anemometry in pulsating flows. A comment on 'A critical review on advanced velocity measurement techniques in pulsating flows'

    OpenAIRE

    Berson, Arganthaël; Blanc-Benon, Philippe; Comte-Bellot, Geneviève

    2010-01-01

    International audience; In their recent topical review, Nabavi and Siddiqui (Meas. Sci. Technol. 2010 21 042002) recommended the use of hot-wire anemometry for velocity measurements in pulsating flows, especially at high frequency. This recommendation is misleading. The procedures invoked by these authors are valid only for small-amplitude fluctuations, which are of little interest for pulsating flows. When large-amplitude velocity changes occur without flow reversal, new procedures for the c...

  18. Pulsation versus metallicism in Am stars as revealed by LAMOST and WASP

    CERN Document Server

    Smalley, B; Holdsworth, D L; Kurtz, D W; Murphy, S J; De Cat, P; Anderson, D R; Catanzaro, G; Cameron, A Collier; Hellier, C; Maxted, P F L; Norton, A J; Pollacco, D; Ripepi, V; West, R G; Wheatley, P J

    2016-01-01

    We present the results of a study of a large sample of A and Am stars with spectral types from LAMOST and light curves from WASP. We find that, unlike normal A stars, $\\delta$ Sct pulsations in Am stars are mostly confined to the effective temperature range 6900 $<$ $T_{\\rm eff}$ $<$ 7600 K. We find evidence that the incidence of pulsations in Am stars decreases with increasing metallicism (degree of chemical peculiarity). The maximum amplitude of the pulsations in Am stars does not appear to vary significantly with metallicism. The amplitude distributions of the principal pulsation frequencies for both A and Am stars appear very similar and agree with results obtained from Kepler photometry. We present evidence that suggests turbulent pressure is the main driving mechanism in pulsating Am stars, rather than the $\\kappa$-mechanism, which is expected to be suppressed by gravitational settling in these stars.

  19. The technology of heat transfer enhancement in channels by means of flow pulsations

    Directory of Open Access Journals (Sweden)

    Tsynaeva Anna

    2016-01-01

    Full Text Available The rate and efficiency of curing of concrete can boost when used intense heat. The work is dedicated to the development and research of technologies of intensification of heat transfer in channels by pulsations. The study was conducted by means of numerical methods based on mass and momentum conservation equations (Navier-Stokes with software Code Saturne. Verification of implemented methods and software was performed. The research of heat transfer enhancement for semicircle-shaped channel exposed to low-frequency pulsations was performed. The pulsation frequency of the flow during the study was in a range of 0…10 Hz. A significant (up to 4 times increase of turbulent kinetic energy with implementing pulsations was detected. Flow pulsations with frequency of 10 Hz results in 1.21 times increase of heat transfer coefficient.

  20. Searching for X-ray Pulsations from Neutron Stars Using NICER

    Science.gov (United States)

    Ray, Paul S.; Arzoumanian, Zaven; Bogdanov, Slavko; Bult, Peter; Chakrabarty, Deepto; Guillot, Sebastien; Kust Harding, Alice; Ho, Wynn C. G.; Lamb, Frederick K.; Mahmoodifar, Simin; Miller, M. Coleman; Strohmayer, Tod E.; Wilson-Hodge, Colleen A.; Wolff, Michael Thomas

    2017-08-01

    The Neutron Star Interior Composition Explorer (NICER) presents an exciting new capability for discovering new modulation properties of X-ray emitting neutron stars, including large area, low background, extremely precise absolute time stamps, superb low-energy response and flexible scheduling. The Pulsation Searches and Multiwavelength Coordination working group has designed a 2.5 Ms observing program to search for pulsations and characterize the modulation properties of about 30 known or suspected neutron star sources across a number of source categories. A key early goal will be to search for pulsations from millisecond pulsars that might exhibit thermal pulsations from the surface suitable for pulse profile modeling to constrain the neutron star equation of state. In addition, we will search for pulsations from transitional millisecond pulsars, isolated neutron stars, LMXBs, accretion-powered millisecond pulsars, central compact objects and other sources. We will present our science plan and initial results from the first months of the NICER mission.