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EXPERIMENTS ON THE RELATION OF THE INHIBITORY TO THE ACCELERATOR NERVES OF THE HEART

Hunt, Reid
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/03/1897 EN
Relevância na Pesquisa
36.14%
The experiments described in Part IV of this paper show that in whatever manner the problem of the relation of the vagus to the accelerators is approached, whether the accelerators are stimulated during a stimulation of the vagus, or the vagus during a stimulation of the accelerators, or both are stimulated simultaneously, either for a short or for a longer period, the result is the same, viz., the effect upon the rate of the heart is determined entirely by the relative strength of the stimuli applied to the two nerves. If the stimuli are of approximately the same strength, as judged by the effect of stimulating the nerves separately, the rate of the heart is but slightly affected; if the stimulus applied to the vagus is the stronger, the heart is slowed; if it is weaker, the heart is accelerated. In all cases the result of stimulating the two nerves simultaneously is approximately the algebraic sum of the results of stimulating them separately; sometimes the inhibitory effect slightly predominates, but not more frequently than does the accelerator effect. Moreover, the two nerves may be stimulated simultaneously for a considerable period of time without either completely overcoming the effect of the other. Thus as far as their effect upon the rate of the ventricular beat is concerned...

Cyclical Effects of Bank Capital Requirements with Imperfect Credit Markets

Agénor, Pierre-Richard; Pereira da Silva, Luiz A.
Fonte: Banco Mundial Publicador: Banco Mundial
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36.03%
This paper analyzes the cyclical effects of bank capital requirements in a simple model with credit market imperfections. Lending rates are set as a premium over the cost of borrowing from the central bank, with the premium itself depending on firms effective collateral. Basel I- and Basel II-type regulatory regimes are defined and a capital channel is introduced through a signaling effect of capital buffers on the cost of bank deposits. The macroeconomic effects of various shocks (a drop in output, an increase in the refinance rate, and a rise in the capital adequacy ratio) are analyzed, under both binding and nonbinding capital requirements. Factors affecting the procyclicality of each regime (defined in terms of the behavior of the risk premium) are also identified and policy implications are discussed.

Public Infrastructure and Private Investment in the Middle East and North Africa

Agénor, Pierre-Richard; Nabli, Mustapha K.; Yousef, Tarik M.
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
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36.02%
The authors examine the impact of public infrastructure on private capital formation in three countries of the Middle East and North Africa-Egypt, Jordan, and Tunisia. They highlight various channels through which public infrastructure may affect private investment. Then they describe their empirical framework, which is based on a vector autoregression (VAR) model that accounts for flows and (quality-adjusted) stocks of public infrastructure, private investment, as well as changes in output, private sector credit, and the real exchange rate. The authors propose two aggregate measures of the quality of public infrastructure and use principal components to derive a composite indicator. Their analysis suggests that public infrastructure has both "flow" and "stock" effects on private investment in Egypt, but only a "stock" effect in Jordan and Tunisia. But these effects are small and short-lived, reflecting the unfavorable environment for private investment in their sample of countries. Reducing unproductive public capital expenditure and improving quality must be accompanied by policy reforms aimed at limiting investment to infrastructure capital that crowds in the private sector and corrects for fundamental market failures. This will entail privatization and greater involvement of the private sector in infrastructure investment. While infrastructure (in the form of the provision of critical telecommunications...

Financial Intermediary Development and Growth Volatility : Do Intermediaries Dampen or Magnify Shocks?

Beck, Thorsten; Lundberg, Mattias; Majnoni, Giovanni
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
EN_US
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36.03%
The authors extend the recent literature on the link between financial development and economic volatility by focusing on the channels through which the development of financial intermediaries affects economic volatility. Their theoretical model predicts that well-developed financial intermediaries dampen the effect of real sector shocks on the volatility of growth while magnifying the effect of monetary shocks-suggesting that, overall, financial intermediaries have no unambiguous effect on growth volatility. The authors test these predictions in a panel data set covering 63 countries over the period 1960-97, using the volatility of terms of trade to proxy for real volatility, and the volatility of inflation to proxy for monetary volatility. They find no robust relationship between the development of financial intermediaries and growth volatility, weak evidence that financial intermediaries dampen the effect of terms of trade volatility, and evidence that financial intermediaries magnify the impact of inflation volatility in low- and middle-income countries.

Monte-Carlo-Simulation des Strahlungstransports im Strahlerkopf eines Elektronenlinearbeschleunigers; The Monte Carlo Simulation of the radiation transport in the Radiation head of an electron linear accelerator

Haryanto, Freddy
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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36.24%
Dok. 1: Dissertation - Textteil Dok. 2 - 5: Anhänge ********************************* Diese Arbeit wurde verfasst, um einen Strahlerkopf für den Strahlungstransport von 6 MV und 15 MV Röntgenstrahlung anhand des Monte-Carlo-Verfahrens zu modellieren. Gestützt auf die Ergebnisse der Arbeit, kann die Dosisberechnung bei Bestrahlungstechniken, insbesondere bei solchen mit fluenzmodulierten Strahlenfeldern, mit der für die klinische Anwendung erforderlichen Genauigkeit durchgeführt werden. Darüber hinaus finden die mit diesen Modellen durchgeführten Simulationen Verwendung, um die entsprechenden Messungen zu verifizieren oder um die bei den Messungen gefundenen Phänomene zu erklären. Zu Beginn wurden sechs Modelle für jede Strahlungsqualität entworfen. Die Parameter der Elektronenquelle wurden für alle sechs Modelle variiert, um die Einflüsse der Parameter der Elektronenquelle auf die Strahlungsfeldgrößen für Röntgenstrahlung und auf die Dosisverteilung im Wasserphantom beobachten zu können. Dabei ergaben sich folgende Resultate : Die Energie der Elektronenquelle spielt eine wichtige Rolle sowohl für die Strahlungsfeldgrößen für Röntgenstrahlung als auch für die Dosisverteilung im Wasserphantom. Die Elektronenenergie beeinflusst nicht nur die Zahl der auf den Phasenraum treffenden Photonen...

Spatial Dynamics of Labor Markets in Brazil

Chomitz, Kenneth M.; da Mata, Daniel; de Carvalho, Alexandre Ywata; Magalhães, João Carlos
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Publications & Research :: Policy Research Working Paper; Publications & Research
ENGLISH
Relevância na Pesquisa
36.02%
There was substantial spatial variation in labor market outcomes in Brazil over the 1990s. In 2000, about one-fifth of workers lived in apparently economically stagnant municipios where real wages declined but employment increased faster than the national population growth rate. More than one-third lived in apparently dynamic municipios, experiencing both real wage growth and faster-than-average employment growth. These areas absorbed more than half of net employment growth over the period. To elucidate this spatial variation, the authors estimate spatial labor supply and demand equations describing wage and employment changes of Brazilian municipios. They use Conley's spatial GMM technique to allow for instrumental variable estimation in the presence of spatially autocorrelated errors. The main findings include: (1) a very strong influence of initial workforce educational levels on subsequent wage growth (controlling for possibly confounding variables such as remoteness and climate); (2) evidence of positive spillover effects of own-municipio growth onto neighbors' wage and employment levels; (3) an exodus from farming areas; (4) relatively elastic response of wages to an increase in labor supply; and (5) evidence of a local multiplier effect from government transfers.

The Effect of Gas Ion Bombardment on the Secondary Electron Yield of TiN, TiCN and TiZrV Coatings For Suppressing Collective Electron Effects in Storage Rings

Pimpec, F. Le; Kirby, R. E.; King, F. K.; Pivi, M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.95%
In many accelerator storage rings running positively charged beams, ionization of residual gas and secondary electron emission (SEE) in the beam pipe will give rise to an electron cloud which can cause beam blow-up or loss of the circulating beam. A preventative measure that suppresses electron cloud formation is to ensure that the vacuum wall has a low secondary emission yield (SEY). The SEY of thin films of TiN, sputter deposited Non-Evaporable Getters and a novel TiCN alloy were measured under a variety of conditions, including the effect of re-contamination from residual gas.; Comment: 15 pages - 7 figures - 8 tables, submitted to NIM A

Accelerator Measurements of the Askaryan effect in Rock Salt: A Roadmap Toward Teraton Underground Neutrino Detectors

Gorham, P. W.; Saltzberg, D.; Field, R. C.; Guillian, E.; Milincic, R.; Walz, D.; Williams, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.99%
We report on further SLAC measurements of the Askaryan effect: coherent radio emission from charge asymmetry in electromagnetic cascades. We used synthetic rock salt as the dielectric medium, with cascades produced by GeV bremsstrahlung photons at the Final Focus Test Beam. We extend our prior discovery measurements to a wider range of parameter space and explore the effect in a dielectric medium of great potential interest to large scale ultra-high energy neutrino detectors: rock salt (halite), which occurs naturally in high purity formations containing in many cases hundreds of cubic km of water-equivalent mass. We observed strong coherent pulsed radio emission over a frequency band from 0.2-15 GHz. A grid of embedded dual-polarization antennas was used to confirm the high degree of linear polarization and track the change of direction of the electric-field vector with azimuth around the shower. Coherence was observed over 4 orders of magnitude of shower energy. The frequency dependence of the radiation was tested over two orders of magnitude of UHF and microwave frequencies. We have also made the first observations of coherent transition radiation from the Askaryan charge excess, and the result agrees well with theoretical predictions. Based on these results we have performed a detailed and conservative simulation of a realistic GZK neutrino telescope array within a salt-dome...

Analysis of longitudinal bunching inan FEL driven two-beam accelerator

Lidia, S.; Gardelle, J.; Lefevre, T.; Donohue, J. T.; Gouard, P.; Rullier, J. L.; Vermare, C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/08/2000
Relevância na Pesquisa
35.97%
Recent experiments [1] have explored the use of a free-electron laser (FEL) as a buncher for a microwave two-beam accelerator, and the subsequent driving of a standing-wave rf output cavity. Here we present a deeper analysis of the longitudinal dynamics of the electron bunches as they are transported from the end of the FEL and through the output cavity. In particular, we examine the effect of the transport region and cavity aperture to filter the bunched portion of the beam. [1] T. Lefevre, et. al., Phys. Rev. Lett. 84 (2000), 1188.; Comment: 3 pages, 8 figures. Submitted to XX Int'l LINAC Conference

RF Processing of X-band Accelerator Structures at the NLCTA

Adolphsen, C.; Baumgartner, W.; Jobe, K.; Loewen, R.; McCormick, D.; Ross, M.; Smith, T.; Wang, J. W.; Higo, T.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/08/2000
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36.03%
During the initial phase of operation, the linacs of the Next Linear Collider (NLC) will contain roughly 5000 X-Band accelerator structures that will accelerate beams of electrons and positrons to 250 GeV. These structures will nominally operate at an unloaded gradient of 72 MV/m. As part of the NLC R&D program, several prototype structures have been built and operated at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. Here, the effect of high gradient operation on the structure performance has been studied. Significant progress was made during the past year after the NLCTA power sources were upgraded to reliably produce the required NLC power levels and beyond. This paper describes the structures, the processing methodology and the observed effects of high gradient operation.; Comment: Submitted to LINAC 2000: Paper ID = TUE01

Wake Field Effect Analysis in APT Linac

Kurennoy, Sergey S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/07/1998
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36.05%
The 1.7-GeV 100-mA CW proton linac is now under design for the Accelerator Production of Tritium (APT) Project. The APT linac comprises both the normal conducting (below 211 MeV) and superconducting (SC) sections. The high current leads to stringent restrictions on allowable beam losses (<1 nA/m), that requires analyzing carefully all possible loss sources. While wake-field effects are usually considered negligible in proton linacs, we study these effects for the APT to exclude potential problems at such a high current. Loss factors and resonance frequency spectra of various discontinuities of the vacuum chamber are investigated, both analytically and using 2-D and 3-D simulation codes with a single bunch as well as with many bunches. Our main conclusion is that the only noticeable effect is the HOM heating of the 5-cell SC cavities. It, however, has an acceptable level and, in addition, will be taken care of by HOM couplers.; Comment: 3 pages, 6 figures; presented at European Particle Accelerator Conference, Stockholm, Sweden (June 22-26, 1998)

Use of a Bent Crystal with a Decreasing Curvature to Increase the Efficiency of the Extraction and Collimation of a Beam in an Accelerator

Yazynin, I. A.; Maisheev, V. A.; Chesnokov, Yu. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/10/2011
Relevância na Pesquisa
35.97%
It has been shown that the use of a bent crystal with a variable curvature radius makes it possible to reduce the fraction of dechanneled particles by an order of magnitude. This effect enables the strong reduction of the particle density at the edge of a collimator or the partition of a septum upon the multiturn extraction of a beam from a ring accelerator. In particular, the beam extraction efficiency at the U-70 synchrotron and Large Hadron Collider can be increased to 95 and 99.65%, respectively.; Comment: 4 pages, 4 figures

Effect of transverse electron velocities on the longitudinal cooling force in the Fermilab electron cooler

Khilkevich, Andrei; Prost, Lionel R.; Shemyakin, Alexander V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 16/08/2012
Relevância na Pesquisa
35.95%
In Fermilab's electron cooler, a 0.1A, 4.3MeV DC electron beam propagates through the 20 m cooling section, which is immersed in a weak longitudinal magnetic field. A proper adjustment of 200 dipole coils, installed in the cooling section for correction of the magnetic field imperfections, can create a helix-like trajectory with the wavelength of 1-10 m. The longitudinal cooling force is measured in the presence of such helixes at different wavelengths and amplitudes. The results are compared with a model calculating the cooling force as a sum of collisions with small impact parameters, where the helical nature of the coherent angle is ignored, and far collisions, where the effect of the coherent motion is neglected. A qualitative agreement is found.; Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1 Apr 2011. New York, USA

Effect of Noise on the Standard Mapping

Karney, Charles F. F.; Rechester, Alexander B.; White, Roscoe B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/01/2005
Relevância na Pesquisa
36.05%
The effect of a small amount of noise on the standard mapping is considered. Whenever the standard mapping possesses accelerator modes (where the action increases approximately linearly with time), the diffusion coefficient contains a term proportional to the reciprocal of the variance of the noise term. At large values of the stochasticity parameter, the accelerator modes exhibit a universal behavior. As a result the dependence of the diffusion coefficient on the stochasticity parameter also shows some universal behavior.; Comment: Plain TeX, 18 pages, 4 figures

Effect of Compton Scattering on the Electron Beam Dynamics at the ATF Damping Ring

Chaikovska, I.; Bruni, C.; Delerue, N.; Variola, A.; Zomer, F.; Kubo, K.; Naito, T.; Omori, T.; Terunuma, N.; Urakawa, J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/10/2011
Relevância na Pesquisa
35.99%
Compton scattering provides one of the most promising scheme to obtain polarized positrons for the next generation of $e^-$ -- $e^+$ colliders. Moreover it is an attractive method to produce monochromatic high energy polarized gammas for nuclear applications and X-rays for compact light sources. In this framework a four-mirror Fabry-P\'erot cavity has been installed at the Accelerator Test Facility (ATF - KEK, Tsukuba, Japan) and is used to produce an intense flux of polarized gamma rays by Compton scattering \cite{ipac-mightylaser}. For electrons at the ATF energy (1.28 GeV) Compton scattering may result in a shorter lifetime due to the limited bucket acceptance. We have implemented the effect of Compton scattering on a 2D tracking code with a Monte-Carlo method. This code has been used to study the longitudinal dynamics of the electron beam at the ATF damping ring, in particular the evolution of the energy spread and the bunch length under Compton scattering. The results obtained are presented and discussed. Possible methods to observe the effect of Compton scattering on the ATF beam are proposed.

Origin and reduction of wakefields in photonic crystal accelerator cavities

Bauer, Carl A.; Werner, Gregory R.; Cary, John R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.95%
Photonic crystal (PhC) defect cavities that support an accelerating mode tend to trap unwanted higher-order modes (HOMs) corresponding to zero-group-velocity PhC lattice modes at the top of the bandgap. The effect is explained quite generally from photonic band and perturbation theoretical arguments. Transverse wakefields resulting from this effect are observed in a hybrid dielectric PhC accelerating cavity based on a triangular lattice of sapphire rods. These wakefields are, on average, an order of magnitude higher than those in the waveguide-damped Compact Linear Collider (CLIC) copper cavities. The avoidance of translational symmetry (and, thus, the bandgap concept) can dramatically improve HOM damping in PhC-based structures.; Comment: 11 pages, 18 figures, 2 tables

Space Charges Can Significantly Affect the Dynamics of Accelerator Maps

Bountis, T.; Skokos, Ch.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/05/2006
Relevância na Pesquisa
36.05%
Space charge effects can be very important for the dynamics of intense particle beams, as they repeatedly pass through nonlinear focusing elements, aiming to maximize the beam's luminosity properties in the storage rings of a high energy accelerator. In the case of hadron beams, whose charge distribution can be considered as "frozen" within a cylindrical core of small radius compared to the beam's dynamical aperture, analytical formulas have been recently derived \cite{BenTurc} for the contribution of space charges within first order Hamiltonian perturbation theory. These formulas involve distribution functions which, in general, do not lead to expressions that can be evaluated in closed form. In this paper, we apply this theory to an example of a charge distribution, whose effect on the dynamics can be derived explicitly and in closed form, both in the case of 2--dimensional as well as 4--dimensional mapping models of hadron beams. We find that, even for very small values of the "perveance" (strength of the space charge effect) the long term stability of the dynamics changes considerably. In the flat beam case, the outer invariant "tori" surrounding the origin disappear, decreasing the size of the beam's dynamical aperture, while beyond a certain threshold the beam is almost entirely lost. Analogous results in mapping models of beams with 2-dimensional cross section demonstrate that in that case also...

Summary of SLAC'S SEY Measurement On Flat Accelerator Wall Materials

Pimpec, F. Le; Kirby, R. E.; King, F. K.; Pivi, M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/11/2007
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35.97%
The electron cloud effect (ECE) causes beam instabilities in accelerator structures with intense positively charged bunched beams. Reduction of the secondary electron yield (SEY) of the beam pipe inner wall is effective in controlling cloud formation. We summarize SEY results obtained from flat TiN, TiZrV and Al surfaces carried out in a laboratory environment. SEY was measured after thermal conditioning, as well as after low energy, less than 300 eV, particle exposure.; Comment: Presented at International Workshop on Electron-Cloud Effects (ECLOUD07), Daegu, Korea 5 figures, 4 pages

Resonant Laser Cooling of Circular Accelerator Beams

Tumanian, R. V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.03%
The resonant laser cooling of circular accelerator beams of relativistic charged particle is studied. It is shown that in the approximation of the given external electromagnetic wave amplitude (small gain free electron laser) the emittance of a beam of charged particles decreases. In the field of particle energy about 100 in the mass energy units the beam energy losses are negligible. The discovered effect can be used for cooling of charged particle beams in various accelerators. The significant cooling rates are possible to achieve by placing of the cooling device in the appropriate points of the accelerator orbit. Resonant laser cooling for various cases are considered. This method of charged particle beams cooling can be applied to circular accelerators of electron and various relativistic heavy particle beams and has significantly, about 3-4 orders of magnitude, shorter cooling time in comparison to any other cooling method.

Longitudinal jitter analysis of linear accelerator electron gun

Mingshan, Liu; Shilun, Pei; Iqbal, Munawar
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/09/2015
Relevância na Pesquisa
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We present measurement and analyses of longitudinal timing jitter of Beijing Electron Positron Collider (BEPCII) linear accelerator electron gun. We simulated longitudinal jitter effect of the gun using PARMELA about beam performance including beam profile, average energy, energy spread, longitudinal phase of reference particle and XY emittance. The maximum percentage difference of the beam parameters are calculated to be; 100%, 13.27%, 42.24%, 7.79% and 65.01%, 86.81%, respectively due to which the bunching efficiency is reduced to 54%. The simulation results are in agreement with test and are helpful to optimize the beam parameters by tuning the trigger timing of the gun during the bunching process.