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1

Domain wall brane in Eddington-inspired Born-Infeld gravity  

NASA Astrophysics Data System (ADS)

Recently, inspired by Eddington’s theory, an alternative gravity called Eddington-inspired Born-Infeld gravity was proposed by Bañados and Ferreira. It is equivalent to Einstein’s general relativity in vacuum, but deviates from it when matter is included. Interestingly, it seems that the cosmological singularities are prevented in this theory. Based on the new theory, we investigate a thick brane model with a scalar field presenting in the five-dimensional background. A domain wall solution is obtained, and further, we find that at low energy the four-dimensional Einstein gravity is recovered on the brane. Moreover, the stability of gravitational perturbations is ensured in this model.

Liu, Yu-Xiao; Yang, Ke; Guo, Heng; Zhong, Yuan

2012-06-01

2

Eddington's planet finding capabilities  

Microsoft Academic Search

The capabilities of Eddington for the detection and analysis of extrasolar planets are outlined. The primary goal of the PF (Planet finding) part of the mission is the detection of planets that are Earth like - which limits their size to less then 3 Earth radii - and which are potentially habitable - which limits their temperature or their orbital

H. J. Deeg; K. Horne

2002-01-01

3

EINSTein  

NASA Astrophysics Data System (ADS)

Artificial Life techniques—specifically, multiagent-based models and evolutionary learning algorithms—provide a powerful new approach to understanding some of the fundamental processes of war. This chapter introduces a simple artificial “toy model” of combat called EINSTein. EINSTein is designed to illustrate how certain aspects of land combat can be viewed as self-organized, emergent phenomena resulting from the dynamical web of interactions among notional combatants. EINSTein's bottom-up, synthesist approach to the modeling of combat stands in stark contrast to the more traditional top-down, or reductionist, approach taken by conventional military models, and it represents a step toward developing a complex systems theoretic toolbox for identifying, exploring, and possibly exploiting self-organized, emergent collective patterns of behavior on the real battlefield. A description of the model is provided, along with examples of emergent spatial patterns and behaviors.

Ilachinski, Andrew

4

Einstein  

NSDL National Science Digital Library

From the American Museum of Natural History comes the online exhibit on the life and legacy of Albert Einstein. Students (who should probably be at least of high school age) can learn about Einstein's revolutionary thinking; his work with light, time, energy, and gravity; his thoughts on peace and war, on being a global citizen, and his legacy according to the museum. Although fairly brief, the site contains some interesting photographs and does a good job of describing the uniqueness of one of history's greatest minds.

2002-01-01

5

Escape, capture, and levitation of matter in Eddington outbursts  

NASA Astrophysics Data System (ADS)

Context. An impulsive increase in luminosity by one half or more of the Eddington value will lead to ejection of all optically thin plasma from Keplerian orbits around the radiating star, if gravity is Newtonian and the Poynting-Robertson drag is neglected. Radiation drag may bring some particles down to the stellar surface. On the other hand, general relativistic calculations show that gravity may be balanced by a sufficiently intense radiation field at a certain distance from the star. Aims: We investigate the motion of test particles around highly luminous stars to determine conditions under which plasma may be ejected from the system. Results: In Einstein's gravity, if the outburst is close to the Eddington luminosity, all test particles orbiting outside an "escape sphere" will be ejected from the system, while all others will be captured from their orbits onto the surface of another sphere, which is well above the stellar surface, and may even be outside the escape sphere, depending on the value of luminosity. Radiation drag will bring all the captured particles to rest on this "Eddington capture sphere", where they will remain suspended in an equilibrium state as long as the local flux of radiation does not change and remains at the effective Eddington value.

Stahl, A.; Klu?niak, W.; Wielgus, M.; Abramowicz, M.

2013-07-01

6

Surface singularities in Eddington-inspired Born-Infeld gravity.  

PubMed

Eddington-inspired Born-Infeld gravity was recently proposed as an alternative to general relativity that offers a resolution of spacetime singularities. The theory differs from Einstein's gravity only inside matter due to nondynamical degrees of freedom, and it is compatible with all current observations. We show that the theory is reminiscent of Palatini f(R) gravity and that it shares the same pathologies, such as curvature singularities at the surface of polytropic stars and unacceptable Newtonian limit. This casts serious doubt on its viability. PMID:23368444

Pani, Paolo; Sotiriou, Thomas P

2012-12-21

7

PHOTON FEEDBACK: SCREENING AND THE EDDINGTON LIMIT  

SciTech Connect

Bright star-forming galaxies radiate well below their Eddington limits. The value of the flux-mean opacity that mediates the radiation force onto matter is orders of magnitude smaller than the UV or optical dust opacity. On empirical grounds, it is shown that high-redshift ULIRGs radiate at two orders of magnitude below their Eddington limits, while the local starbursters M82 and Arp 220 radiate at a few percent of their Eddington limits. A model for the radiative transfer of UV and optical light in dust-rich environments is considered. Radiation pressure on dust does not greatly affect the large-scale gas dynamics of star-forming galaxies.

Socrates, Aristotle [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Sironi, Lorenzo, E-mail: socrates@ias.edu, E-mail: lsironi@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States)

2013-08-01

8

Cosmology in Eddington-Inspired Gravity  

NASA Astrophysics Data System (ADS)

In this paper, we study the cosmological evolution of the universe filled with the perfect fluid in the Eddington-inspired Born-Infeld gravity, proposed recently by Banados and Ferreira. Applying a method in which the evolution of the scale factor is regarded as that of a particle moving in a potential, we show all possible cases of cosmological evolution.

Ji, Dong

2014-07-01

9

Eddington's theory of gravity and its progeny.  

PubMed

We resurrect Eddington's proposal for the gravitational action in the presence of a cosmological constant and extend it to include matter fields. We show that the Newton-Poisson equation is modified in the presence of sources and that charged black holes show great similarities with those arising in Born-Infeld electrodynamics coupled to gravity. When we consider homogeneous and isotropic space-times, we find that there is a minimum length (and maximum density) at early times, clearly pointing to an alternative theory of the big bang. We thus argue that the modern formulation of Eddington's theory, Born-Infeld gravity, presents us with a novel, nonsingular description of the Universe. PMID:20867432

Bañados, Máximo; Ferreira, Pedro G

2010-07-01

10

Compact Stars in Eddington Inspired Gravity  

NASA Astrophysics Data System (ADS)

A new, Eddington inspired theory of gravity was recently proposed by Bañados and Ferreira. It is equivalent to general relativity in vacuum, but differs from it inside matter. This viable, one-parameter theory was shown to avoid cosmological singularities and turns out to lead to many other exciting new features that we report here. First, for a positive coupling parameter, the field equations have a dramatic impact on the collapse of dust, and do not lead to singularities. We further find that the theory supports stable, compact pressureless stars made of perfect fluid, which provide interesting models of self-gravitating dark matter. Finally, we show that the mere existence of relativistic stars imposes a strong, near optimal constraint on the coupling parameter, which can even be improved by observations of the moment of inertia of the double pulsar.

Pani, Paolo; Cardoso, Vitor; Delsate, Térence

2011-07-01

11

Compact stars in Eddington inspired gravity.  

PubMed

A new, Eddington inspired theory of gravity was recently proposed by Bañados and Ferreira. It is equivalent to general relativity in vacuum, but differs from it inside matter. This viable, one-parameter theory was shown to avoid cosmological singularities and turns out to lead to many other exciting new features that we report here. First, for a positive coupling parameter, the field equations have a dramatic impact on the collapse of dust, and do not lead to singularities. We further find that the theory supports stable, compact pressureless stars made of perfect fluid, which provide interesting models of self-gravitating dark matter. Finally, we show that the mere existence of relativistic stars imposes a strong, near optimal constraint on the coupling parameter, which can even be improved by observations of the moment of inertia of the double pulsar. PMID:21838345

Pani, Paolo; Cardoso, Vitor; Delsate, Térence

2011-07-15

12

BAL QSOs AND EXTREME UFOs: THE EDDINGTON CONNECTION  

SciTech Connect

We suggest a common physical origin connecting the fast, highly ionized winds (UFOs) seen in nearby active galactic nuclei (AGNs), and the slower and less ionized winds of broad absorption line (BAL) QSOs. The primary difference is the mass-loss rate in the wind, which is ultimately determined by the rate at which mass is fed toward the central supermassive black hole (SMBH) on large scales. This is below the Eddington accretion rate in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143, but ranges up to {approx}10-50 times this in BAL QSOs. For UFOs this implies black hole accretion rates and wind mass-loss rates which are at most comparable to Eddington, giving fast, highly ionized winds. In contrast, BAL QSO black holes have mildly super-Eddington accretion rates, and drive winds whose mass-loss rates are significantly super-Eddington, and so are slower and less ionized. This picture correctly predicts the velocities and ionization states of the observed winds, including the recently discovered one in SDSS J1106+1939. We suggest that luminous AGNs may evolve through a sequence from BAL QSO through LoBAL to UFO-producing Seyfert or quasar as their Eddington factors drop during the decay of a bright accretion event. LoBALs correspond to a short-lived stage in which the AGN radiation pressure largely evacuates the ionization cone, but before the large-scale accretion rate has dropped to the Eddington value. We show that sub-Eddington wind rates would produce an M-{sigma} relation lying above that observed. We conclude that significant SMBH mass growth must occur in super-Eddington phases, either as BAL QSOs, extreme UFOs, or obscured from direct observation.

Zubovas, Kastytis; King, Andrew, E-mail: kastytis.zubovas@ftmc.lt [Theoretical Astrophysics Group, University of Leicester, Leicester LE1 7RH (United Kingdom)

2013-05-20

13

BAL QSOs and Extreme UFOs: The Eddington Connection  

NASA Astrophysics Data System (ADS)

We suggest a common physical origin connecting the fast, highly ionized winds (UFOs) seen in nearby active galactic nuclei (AGNs), and the slower and less ionized winds of broad absorption line (BAL) QSOs. The primary difference is the mass-loss rate in the wind, which is ultimately determined by the rate at which mass is fed toward the central supermassive black hole (SMBH) on large scales. This is below the Eddington accretion rate in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143, but ranges up to ~10-50 times this in BAL QSOs. For UFOs this implies black hole accretion rates and wind mass-loss rates which are at most comparable to Eddington, giving fast, highly ionized winds. In contrast, BAL QSO black holes have mildly super-Eddington accretion rates, and drive winds whose mass-loss rates are significantly super-Eddington, and so are slower and less ionized. This picture correctly predicts the velocities and ionization states of the observed winds, including the recently discovered one in SDSS J1106+1939. We suggest that luminous AGNs may evolve through a sequence from BAL QSO through LoBAL to UFO-producing Seyfert or quasar as their Eddington factors drop during the decay of a bright accretion event. LoBALs correspond to a short-lived stage in which the AGN radiation pressure largely evacuates the ionization cone, but before the large-scale accretion rate has dropped to the Eddington value. We show that sub-Eddington wind rates would produce an M-? relation lying above that observed. We conclude that significant SMBH mass growth must occur in super-Eddington phases, either as BAL QSOs, extreme UFOs, or obscured from direct observation.

Zubovas, Kastytis; King, Andrew

2013-05-01

14

The Mythical Snake which Swallows its Tail: Einstein's matter world  

E-print Network

In 1917 Einstein introduced into his field equations a cosmological term having the cosmological constant as a coefficient, in order that the theory should yield a static universe. Einstein desired to eliminate absolute space from physics according to "Mach's ideas". De Sitter objected to the "world-matter" in Einstein's world, and proposed a vacuum solution of Einstein's field equations with the cosmological constant and with no "world-matter". In 1920 the world-matter of Einstein's world was equivalent to "Mach's Ether", a carrier of the effects of inertia. De Sitter's 1917 solution predicted a spectral shift effect. In 1923 Eddington and Weyl adopted De Sitter's model and studied this effect. Einstein objected to this "cosmological problem". This paper is a new interpretation to Einstein's cosmological considerations over the period 1917-1923.

Weinstein, Galina

2013-01-01

15

BAL QSOs and Extreme UFOs: the Eddington connection  

E-print Network

We suggest a common physical origin connecting the fast, highly ionized winds (UFOs) seen in nearby AGN, and the slower and less ionized winds of BAL QSOs. The primary difference is the mass loss rate in the wind, which is ultimately determined by the rate at which mass is fed towards the central supermassive black hole (SMBH) on large scales. This is below the Eddington accretion rate in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143, but ranges up to $\\sim 10-50$ times this in BAL QSOs. For UFOs this implies black hole accretion rates and wind mass loss rates which are at most comparable to Eddington, giving fast, highly-ionized winds. In contrast BAL QSO black holes have mildly super-Eddington accretion rates, and drive winds whose mass loss rates are significantly super-Eddington, and so are slower and less ionized. This picture correctly predicts the velocities and ionization states of the observed winds, including the recently-discovered one in SDSS J1106+1939. We suggest tha...

Zubovas, Kastytis

2013-01-01

16

Not Only Because of Theory: Dyson, Eddington and the Competing Myths of the 1919 Eclipse Expedition  

E-print Network

The 1919 Eclipse Expedition to test the light-bending prediction of General Relativity remains one of the most famous physics experiments of the 20th century. However, in recent decades it has been increasingly often alleged that the data-analysis of the expedition's leaders was faulty and biased in favor of Einstein's theory. Arthur Stanley Eddington is particularly alleged to have been prejudiced in favor of general relativity. Specifically it is claimed that some of the data, which would have favored the so-called Newtonian prediction, was thrown out on dubious grounds. This paper argues that a close examination of the views of the expedition's organizers, and of their data analysis, suggests that they had good grounds for acting as they did, and that the key people involved, in particular the astronomer Frank Watson Dyson, were not biased in favor of Einstein. It also draws attention to a modern re-analysis of the most important eclipse plates which, though overlooked until now, tends to strongly support the thesis of this paper.

Daniel Kennefick

2007-09-05

17

FOREWORD: Modern Applications of Timescales Modern Applications of Timescales  

NASA Astrophysics Data System (ADS)

The development of the first atomic frequency standard by Louis Essen in the 1950s is at the origin of the adoption of the atomic definition of the SI second by the 13th General Conference on Weights and Measures in 1967 and the consequent adoption of the atomic timescale. After the short reign of ephemeris time as the world's reference timescale from 1954 until 1967, Coordinated Universal Time (UTC), synchronized to universal time UT1, appeared as the best compromise for satisfying the requests of all users. At the moment of the discussion on the adoption of an atomic timescale to replace ephemeris time, the possibility of having both an astronomical time and an atomic time to serve different purposes was discussed. In the words of Essen [1], this 'would cause endless confusion as well as involving duplication of equipment'. Forty years after the adoption of the definition of Coordinated Universal Time at the International Telecommunication Union (ITU), we are close to the moment of making a decision on whether or not to decouple UTC from its tight link to the rotation of the Earth embodied in UT1. It has been a ten-year process of discussion, mainly at the ITU with the input of the International Astronomical Union, the BIPM, the Consultative Committee for Time and Frequency and other organizations. The majority opinion supported the change based on developers and users of systems that need time synchronization to a stable and continuous reference timescale; others insist on the necessity of keeping the leap-second strategy for serving some applications or just for tradition. It is our hope that, as happened in the seventies, the most appropriate definition to serve all modern applications will be adopted with the consensus of the different sectors. The redirection of international timekeeping from astronomy to metrology can be considered the benchmark that started the era of modern timescales, all based on atomic properties. The aim of this special issue of Metrologia is to review timescales in use today, either the internationally recognized references or those adapted to some specific applications, to discuss new and future developments and to present the sometimes complex procedures for making international recommendations. We are grateful to our colleagues who, without exception, accepted our invitation to contribute to this special issue. Reference Henderson D 2005 Metrologia 42 S4-29 The pdf file contains an appendix: "Glossary of acronyms related to timescales used in this issue".

Arias, E. F.; Lewandowski, W.

2011-08-01

18

Einstein Online  

NSDL National Science Digital Library

Einstein Online provides the user with a simple, but meticulous, approach to Einstein's Theory of Relativity. In the section 'Elementary Einstein', the theories of Special and General Relativity are explained in detail, going through concepts like Relativity, Spacetime and Space Geometry. The following section, 'Spotlights on Relativity', contains applications of both theories, from the Relativity of Simultaneity, to Gravity and Gravitational Waves, to Black Holes and Cosmology, to the Quantum realm.

2007-06-18

19

Jet production in super-Eddington accretion disks  

NASA Technical Reports Server (NTRS)

A two-dimensional, radiation-coupled, Newtonian hydrodynamic simulation is reported for a super-Eddington, mass accretion rate, M = 4 M(E) disk accretion flow onto a 3-solar mass pseudoblack hole. Near the disk midplane, convection cells effectively block the accretion flow, even though viscous heating maximizes there. Accretion predominantly occurs in a supersonic inflow which follows streamlines of approximately constant angular momentum. The optically thick inflow traps radiation so that 80 percent of the luminosity is absorbed by the black hole; the emergent power is sub-Eddington. An axial jet self consistently forms just outside a conical photosphere which bounds the accretion zone; radiation pressure accelerates the jet to about 10 to the 10th cm/s. The jet's mass efflux is only 0.4 percent of the total mass accretion rate.

Eggum, G. E.; Coroniti, F. V.; Katz, J. I.

1985-01-01

20

Electron positron pair winds and the Eddington limit  

NASA Technical Reports Server (NTRS)

The dynamics of pair winds in the environment of the central engine of Active Galactic Nuclei (AGN) are investigated assuming super Eddington accretion onto black holes. If the accretion is assumed to be spherically symmetric with the accreting matter occurring in discrete cool blobs, and pairs are produced by a nonthermal mechanism, these pairs are blown out by radiation pressure if the coupling between the pairs and accreting blobs is not complete. The coupling also determines the escaping luminosity. If the maximal coupling constraint is relaxed, then a qualitative argument shows that the classical Eddington limit may be exceeded. When the pairs are considered to be noninteracting particles, the outflow is optically thin. Frame dependent effects are considered. Equations are derived considering pair production in the rest frame of the wind and also in the rest frame of the accreting cool blobs. The hydrodynamic equations are integrated numerically.

Leighly, K. M.; Tsuruta, S.

1989-01-01

21

Kaluza Ansatz applied to Eddington inspired Born-Infeld Gravity  

E-print Network

We apply Kaluza's procedure to Eddington-inspired Born-Infeld action in gravity in five dimensions. The resulting action contains, in addition to the usual four-dimensional actions for gravity and electromagnetism, nonlinear couplings between the electromagnetic field strength and curvature. Considering the spherically symmetric solution as an example we find the lowest order corrections for the Reissner-Nordstr\\"om metric and the electromagnetic field.

Karan Fernandes; Amitabha Lahiri

2014-05-09

22

Centenarian Einstein  

ScienceCinema

Commémoration de A.Einstein avec 4 orateurs pour honnorer sa mémoire: le prof.Weisskopf parlera de l'homme de science engagé, Daniel Amati du climat de la physique aux années 1920, Sergio Fubini de l'heure scientifique d'A.Einstein et le prof.Berob(?)

None

2011-04-25

23

Solar activity over different timescales  

NASA Astrophysics Data System (ADS)

The report deals with the “General History of the Sun” (multi-scale description of the long-term behavior of solar activity): the possibility of reconstruction. Time scales: • 100-150 years - the Solar Service. • 400 - instrumental observations. • 1000-2000 years - indirect data (polar auroras, sunspots seen with the naked eye). • Over-millennial scale (Holocene) -14? (10Be) Overview and comparison of data sets. General approaches to the problem of reconstruction of solar activity indices on a large timescale. North-South asymmetry of the sunspot formation activity. 200-year cycle over the “evolution timescales”.The relative contribution of the large-scale and low-latitude. components of the solar magnetic field to the general geomagnetic activity. “Large-scale” and low-latitude sources of geomagnetic disturbances.

Obridko, Vladimir; Nagovitsyn, Yuri

24

Accretion Timescales from Kepler AGN  

NASA Astrophysics Data System (ADS)

We constrain AGN accretion disk variability mechanisms using the optical light curves of AGN observed by Kepler. AGN optical fluxes are known to exhibit stochastic variations on timescales of hours, days, months and years. The excellent sampling properties of the original Kepler mission - high S/N ratio (105), short sampling interval (30 minutes), and long sampling duration (~ 3.5 years) - allow for a detailed examination of the differences between the variability processes present in various sub-types of AGN such as Type I and II Seyferts, QSOs, and Blazars. We model the flux data using the Auto-Regressive Moving Average (ARMA) representation from the field of time series analysis. We use the Kalman filter to determine optimal mode parameters and use the Akaike Information Criteria (AIC) to select the optimal model. We find that optical light curves from Kepler AGN cannot be fit by low order statistical models such as the popular AR(1) process or damped random walk. Kepler light curves exhibit complicated power spectra and are better modeled by higher order ARMA processes. We find that Kepler AGN typically exhibit power spectra that change from a bending power law (PSD ~ 1/fa) to a flat power spectrum on timescales in the range of ~ 5 - 100 days consistent with the orbital and thermal timescales of a typical 107 solar mass black hole.

Kasliwal, Vishal P.; Vogeley, Michael S.; Richards, Gordon T.

2015-01-01

25

Einsteins dream  

SciTech Connect

This book discusses the following topics: the search for meaning; Einstein's dream; curved space; Einstein and warped space-time and extreme wraping; early unified field theories; star death; beyond the white dwarf; the early universe; the hadron, Lepton, and Radiation eras; the redshift controversy; other universes; the final fate of the universe; the missing mass; bounce; fate of the open universe; the world of particles and fields; Dirac's equation; Yukawa; gauge theory; quantum chromodynamics; supergravity and superstrings; twistors and heaven; and the new Einstein.

Parker, B.

1986-01-01

26

Is Eddington-Born-Infeld theory really free of cosmological singularities?  

NASA Astrophysics Data System (ADS)

The Eddington-inspired-Born-Infeld (EiBI) theory has recently been resurrected. Such a theory is characterized by being equivalent to Einstein theory in vacuum but differing from it in the presence of matter. One of the virtues of the theory is that it avoids the Big Bang singularity for a radiation-filled universe. In this paper, we analyze singularity avoidance in this kind of model. More precisely, we analyze the behavior of a homogeneous and isotropic universe filled with phantom energy in addition to the dark and baryonic matter. Unlike the Big Bang singularity that can be avoided in this kind of model through a bounce or a loitering effect on the physical metric, we find that the Big Rip singularity is unavoidable in the EiBI phantom model even though it can be postponed towards a slightly further future cosmic time as compared with the same singularity in other models based on the standard general relativity and with the same matter content as described above.

Bouhmadi-López, Mariam; Chen, Che-Yu; Chen, Pisin

2014-03-01

27

Celebrating Einstein  

NASA Astrophysics Data System (ADS)

The Gravity Group at Montana State University (MSU) hosted Celebrating Einstein, a free public arts and multimedia event celebrating Einstein and his ideas in Bozeman, Montana April 2-6, 2013. The products of our efforts are now available to any party interested in hosting a similar event. Celebrating Einstein is a truly interdisciplinary effort including art, film, dance, music, physics, history, and education. Events included a black hole immersive art installation, a series of public talks by physicists, and Einstein lessons in the public schools leading up to a live free public multimedia performance including a professional dance company, a live interview with a renowned physicist, and an original score composed for the MSU student symphony to be performed with an original film produced by the Science and Natural History film program at MSU. This project is funded by the Montana Space Grant Consortium, Montana State University, and the National Science Foundation.

Shapiro Key, Joey; Yunes, Nicolas

2013-04-01

28

Decoding Intention at Sensorimotor Timescales  

PubMed Central

The ability to decode an individual's intentions in real time has long been a ‘holy grail’ of research on human volition. For example, a reliable method could be used to improve scientific study of voluntary action by allowing external probe stimuli to be delivered at different moments during development of intention and action. Several Brain Computer Interface applications have used motor imagery of repetitive actions to achieve this goal. These systems are relatively successful, but only if the intention is sustained over a period of several seconds; much longer than the timescales identified in psychophysiological studies for normal preparation for voluntary action. We have used a combination of sensorimotor rhythms and motor imagery training to decode intentions in a single-trial cued-response paradigm similar to those used in human and non-human primate motor control research. Decoding accuracy of over 0.83 was achieved with twelve participants. With this approach, we could decode intentions to move the left or right hand at sub-second timescales, both for instructed choices instructed by an external stimulus and for free choices generated intentionally by the participant. The implications for volition are considered. PMID:24523855

Salvaris, Mathew; Haggard, Patrick

2014-01-01

29

The controversy between Alexander Friedmann and Albert Einstein about the possibility of a non-static world (German Title: Die Kontroverse zwischen Alexander Friedmann und Albert Einstein um die Möglichkeit einer nichtstatischen Welt)  

Microsoft Academic Search

Einstein's treatment of the cosmological problem as well as his unshakeable adherence to his own static solution of the complete field equations was throughout determined by Ernst Mach's idea of relativity of inertia. Friedmann, however, like Eddington, Weyl and others did not consider Mach's principle to be a part of general relativity, and so he regarded a time dependent developing

Georg Singer

2005-01-01

30

Genomic clocks and evolutionary timescales  

NASA Technical Reports Server (NTRS)

For decades, molecular clocks have helped to illuminate the evolutionary timescale of life, but now genomic data pose a challenge for time estimation methods. It is unclear how to integrate data from many genes, each potentially evolving under a different model of substitution and at a different rate. Current methods can be grouped by the way the data are handled (genes considered separately or combined into a 'supergene') and the way gene-specific rate models are applied (global versus local clock). There are advantages and disadvantages to each of these approaches, and the optimal method has not yet emerged. Fortunately, time estimates inferred using many genes or proteins have greater precision and appear to be robust to different approaches.

Blair Hedges, S.; Kumar, Sudhir

2003-01-01

31

Einstein's Gravity  

NSDL National Science Digital Library

In this lesson, students will read the 1919 edition of the Cosmic Times (see related resources) and respond by raising questions to be answered with further research. They will make a model of curved space to view the motion of spheres as explained by Albert Einstein's General Theory of Relativity. After presentations of their research to the class they will create an interview with Einstein. This activity is part of the Cosmic Times teachers guide and is intended to be used in conjunction with the 1919 Cosmic Times Poster.

32

Einstein Light  

NSDL National Science Digital Library

This web site is a basic, non-mathematical introduction to relativity, built around the framework of Flash media files with narration and animations. Einstein Light was intended to serve a diverse range of users at a variety of levels. It explores concepts from Galileo, Newton, and Maxwell through Einstein and special relativity. The site also introduces modern topics such as binding energies in the nucleus and the relationship between gravity and quantum mechanics. Background information is provided in 30 detailed pages, organized by topic and level of mathematics required for understanding. Questions are also available to assess student comprehension.

Wolfe, Joe; Hatsidimitris, George

2007-12-08

33

Einstein Revisited  

ERIC Educational Resources Information Center

A brief description on the work and life of the great physicist scientist Albert Einstein is presented. The photoelectric paper written by him in 1905 led him to the study of fluctuations in the energy density of radiation and from there to the incomplete nature of the equipartition theorem of classical mechanics, which failed to account for…

Fine, Leonard

2005-01-01

34

Einstein's Mirror  

ERIC Educational Resources Information Center

Reflection of light from a plane mirror in uniform rectilinear motion is a century-old problem, intimately related to the foundations of special relativity. The problem was first investigated by Einstein in his famous 1905 paper by using the Lorentz transformations to switch from the mirror's rest frame to the frame where the mirror moves at a…

Gjurchinovski, Aleksandar; Skeparovski, Aleksandar

2008-01-01

35

Einstein's Relativity  

NSDL National Science Digital Library

These web pages contain material explaining Einstein's general and special theories of relativity. Gravity and warped spacetime are included, along with explanations of the impact on observational astronomy. This is part of Astronomy Notes, an educational resource for introductory astronomy classes.

Strobel, Nick

2004-06-13

36

Radation force on a relativistic plasma and the Eddington limit  

SciTech Connect

The Thomson-scattering radiation force on a hot isotropic exceeds that on a cold one by a factor of (2/3<(..gamma beta..)/sup 2/>+1), where ..gamma.. = (1-..beta../sup 2/)/sup -1/2/ is the electron Lorentz factor. This excess force results from the anisotropic loss of internal energy. Consequently, a relativistic plasma with <..gamma../sup 2/>>>5/2, when exposed to an anisotropic radiation field, acts as a rocket-a ''Compton rocket'', Compton rockets quite likely play a role in the more exotic astronomical objects (quasars, blazars, Seyfert nuclei, compact galactic X-ray sources, etc.), which appear to operate within a few orders of magnitude of the (classical) Thomson-scattering Eddington limit.

O'Dell, S.L.

1981-02-01

37

BOOK REVIEW: Einsteins Kosmos. Untersuchungen zur Geschichte der Kosmologie Relativitatstheorie und zu Einsteins Wirken und Nachwirken  

NASA Astrophysics Data System (ADS)

This book collects about 15 papers (most of them by one single author) on Einstein and the history of general relativity (GR) and the foundations of relativistic cosmology. The matter not only deals with Einstein and his times, but also with pre-GR ideas, and with the interplay of Einstein and his colleagues (opposing as well as supporting personalities). As the title indicates, all papers are written in German, but they include comprehensive Abstracts both in German and English. The book is illustrated with quite a number classical - but also some far more original though not less beautiful - photographs and facsimiles of documents. The book is edited very well, though the style of references is not quite homogeneous. There is no Index. K. Hentschel covers Einstein's argumentation for the existence of graviational redshift, and the initial search for empirical support. The error analysis of observational evidence supporting relativistic light deflection is discussed in a paper by P. Brosche. In particular, H. Duerbeck and P. Flin - in their description of the life and work of Silberstein, who was quite sceptic on the significance of the observational verifications a la Eddington - include the transcription of two most revealing letters by Silberstein to Sommerfeld (1919) and to Einstein (1934). In the first letter, Silberstein clearly shows his scientific maturity and integrity by scrutinising the observational evidence supporting light deflection, presented at a joint meeting of the Royal Society and the Royal Astronomical Society. The second letter, which is more a personal letter, includes lots of political references and connotations. Some of Einstein's political views are also revealed by D.B. Herrmann on the basis of his own correspondence with E.G. Straus, a collaborator of Einstein's. In a consequent paper, S. Grundmann gives remarks on Herrmann's contribution and illustrates Einstein's attitude towards Marx, Engels, Lenin and Stalin. M. Schemmel discusses Schwarzschild's cosmological speculations, and wonders why some people do immediately grasp the meaning and consequence of newly proposed doctrines, whereas the bulk of the contemporaneous scientists respond in a rather low profile. T. Jung reviews Einstein's contribution to cosmology, leading to the Friedmann-Einstein and Einstein-de Sitter universes (with a detailed Appendix on the Friedmann-Lemaitre cosmology), and also presents the cosmological work of Selety, and his correspondence with Einstein. In a subsequent paper, H.-J. Schmidt comments on Einstein's criticism on de Sitter's solution of the Einstein field equations. Controversies with Einstein are elaborated by G. Singer (on Friedmann) and by K. Roessler (on Lemaitre). J. Renn and T. Sauer discuss Mandl's role in the publication history of Einstein's papers, notably Einstein's short paper on gravitational lensing. Finally, the book concludes with a contribution by D.B. Herrmann about the relationship between Einstein and Archenhold Observatory (where Einstein gave his first Berlin popular lecture in 1915), the transcription of H.-J. Treder's 1979 public address at the Einstein memorial plaque, and an inventory list of about 50 Einstein memorabilia - monuments, busts, plaques - compiled by W.R. Dick. This book is based on ideas approached in a historical context from the individual perspective of the authors. It is a real treasure trove of information and basic references on the history of GR, and it also covers quite some grounds with mathematical equations.

Sterken, C.; Duerbeck, H. W.; Dick, W. R.

2006-12-01

38

Transforming Education at Einstein  

E-print Network

of Albert Einstein College of Medicine of Yeshiva University #12;2 EinstEin : WintEr/spring 2012 Meet Our trANsfOrMiNg eDuCAtiON At eiNsteiN Education at Albert Einstein College of Medicine is undergoing the magazine for alumni, faculty, students, friends and supporters of Albert einstein College of Medicine

Yates, Andrew

39

Eddington-class flares and their distance from the central black hole in blazars  

NASA Astrophysics Data System (ADS)

The distance from the central engine at which the bright gamma-ray flares of blazars take place is an open question with implications on our understanding of jet formation and collimation. In some cases, pair opacity arguments suggest that the detection of sub-TeV photons points to the emission taking place beyond the ~ 0.1 pc size broad line region. Here we show that for bright flares having beaming-corrected luminosity comparable to the Eddington luminosity (Eddington-class flares), strong deceleration due to Compton drag is expected if the flare takes place inside the 1-few pc molecular torus region. This is incompatible with the highly superluminal speeds these sources exhibit, requiring that Eddington-class flares take place beyond the molecular torus. We demonstrate this in the case of the MAGIC-detected source PKS 1222+21 (Aleksicet al. 2011), a source that exhibited Eddington-class flares in 2010 (Tanaka11).

Georganopoulos, Markos; Rivas, David

2014-08-01

40

Three dimensional Eddington-inspired Born-Infeld gravity: Solutions  

NASA Astrophysics Data System (ADS)

Three dimensional Eddington-inspired Born-Infeld gravity is studied with the goal of finding new solutions. Beginning with cosmology, we obtain analytical and numerical solutions for the scale factor a(t), in spatially flat (k=0) and spatially curved (k=±1) Friedmann-Roberston-Walker universes with (i) pressureless dust (P=0) and (ii) perfect fluid (P=(?)/(2)), as matter sources. When the theory parameter ?>0, our cosmological solutions are generically singular (except for the open universe, with a specific condition). On the other hand, for ?<0 we do find nonsingular cosmologies. We then move on towards finding static, circularly symmetric line elements with matter obeying (i) p=0 and (ii) p=(?)/(2). For p=0, the solution found is nonsingular for ?<0 with the matter-stress-energy representing inhomogeneous dust. For p=(?)/(2) we obtain nonsingular solutions, for all ?, and discuss some interesting characteristics of these solutions. Finally, we look at the rather simple p=-? case where the solutions are either de Sitter or anti-de Sitter or flat spacetime.

Jana, Soumya; Kar, Sayan

2013-07-01

41

Eddington-limited X-Ray Bursts as Distance Indicators. I. Systematic Trends and Spherical Symmetry in Bursts from 4U 1728-34  

NASA Astrophysics Data System (ADS)

We investigate the limitations of thermonuclear X-ray bursts as a distance indicator for the weakly magnetized accreting neutron star 4U 1728-34. We measured the unabsorbed peak flux of 81 bursts in public data from the Rossi X-Ray Timing Explorer (RXTE). The distribution of peak fluxes was bimodal: 66 bursts exhibited photospheric radius expansion (presumably reaching the local Eddington limit) and were distributed about a mean bolometric flux of 9.2×10-8ergscm-2s-1, while the remaining (non-radius expansion) bursts reached 4.5×10-8ergscm-2s-1, on average. The peak fluxes of the radius expansion bursts were not constant, exhibiting a standard deviation of 9.4% and a total variation of 46%. These bursts showed significant correlations between their peak flux and the X-ray colors of the persistent emission immediately prior to the burst. We also found evidence for quasi-periodic variation of the peak fluxes of radius expansion bursts, with a timescale of ~=40 days. The persistent flux observed with RXTE/ASM over 5.8 yr exhibited quasi-periodic variability on a similar timescale. We suggest that these variations may have a common origin in reflection from a warped accretion disk. Once the systematic variation of the peak burst fluxes is subtracted, the residual scatter is only ~=3%, roughly consistent with the measurement uncertainties. The narrowness of this distribution strongly suggests that (1) the radiation from the neutron star atmosphere during radius expansion episodes is nearly spherically symmetric and (2) the radius expansion bursts reach a common peak flux that may be interpreted as a standard candle intensity. Adopting the minimum peak flux for the radius expansion bursts as the Eddington flux limit, we derive a distance for the source of 4.4-4.8 kpc (assuming RNS=10 km), with the uncertainty arising from the probable range of the neutron star mass MNS=1.4-2 Msolar.

Galloway, Duncan K.; Psaltis, Dimitrios; Chakrabarty, Deepto; Muno, Michael P.

2003-06-01

42

Tidal Despinning Timescales in the Solar System  

Microsoft Academic Search

Planets and satellites in the Solar System despin to a spin-evolved end-state due to tidal dissipation. The usual derivation for the despinning timescale sets the change in spin angular momentum equal to to the gravitational torque acting on the object's tidal bulge (MacDonald 1964, Goldreich and Soter 1966, Peale 1974, 1977). The despinning timescale is found to be proportional to

C. F. Chyba; P. J. Thomas

1998-01-01

43

Earth accretion dynamics and time-scales  

Microsoft Academic Search

The degree to which efficient mixing of new material, losses of volatiles to space and changes in oxidation characterize the impact-driven growth of Earth-like planets in unclear. These processes affect calculated time-scales and can be studied by parallel modeling of data from different radiogenic isotope systems. The W isotope composition of the silicate Earth yields a model time-scale for accretion

A. N. Halliday

2003-01-01

44

Millisecond Timescale Synchrony among Hippocampal Neurons.  

PubMed

Inhibitory neurons in cortical circuits play critical roles in composing spike timing and oscillatory patterns in neuronal activity. These roles in turn require coherent activation of interneurons at different timescales. To investigate how the local circuitry provides for these activities, we applied resampled cross-correlation analyses to large-scale recordings of neuronal populations in the cornu ammonis 1 (CA1) and CA3 regions of the hippocampus of freely moving rats. Significant counts in the cross-correlation of cell pairs, relative to jittered surrogate spike-trains, allowed us to identify the effective couplings between neurons in CA1 and CA3 hippocampal regions on the timescale of milliseconds. In addition to putative excitatory and inhibitory monosynaptic connections, we uncovered prominent millisecond timescale synchrony between cell pairs, observed as peaks in the central 0 ms bin of cross-correlograms. This millisecond timescale synchrony appeared to be independent of network state, excitatory input, and ? oscillations. Moreover, it was frequently observed between cells of differing putative interneuronal type, arguing against gap junctions as the sole underlying source. Our observations corroborate recent in vitro findings suggesting that inhibition alone is sufficient to synchronize interneurons at such fast timescales. Moreover, we show that this synchronous spiking may cause stronger inhibition and rebound spiking in target neurons, pointing toward a potential function for millisecond synchrony of interneurons in shaping and affecting timing in pyramidal populations within and downstream from the circuit. PMID:25378164

Diba, Kamran; Amarasingham, Asohan; Mizuseki, Kenji; Buzsáki, György

2014-11-01

45

Was Einstein A Laplacean?  

E-print Network

distinguished physicists, Niels Bohr and Albert Einstein. It is widely believed that the dynamics of this dialogue were dictated by an overview of "physical reality" held by Einstein. Such interpretations typically presume that Einstein's arguments.... Colodny, ed., Paradigms and Paradoxes, Pittsburgh, 1972, pp. 67-302. 4 Victor F. Lenzen, "Einstein's Theory of Knowledge," in P. A. Schilpp, ed., Albert Einstein: Philosopher-Scientist, Open Court, 1970, pp7 357-82. 5 W. H. Furry, "Note...

Horner, Jack K.

46

Relativistic radiative transfer in relativistic plane-parallel flows: Behavior of the Eddington factor  

NASA Astrophysics Data System (ADS)

Relativistic radiative transfer in a relativistic plane-parallel flow which is accelerated from its base, like an accretion disk wind, is numerically examined under a fully special-relativistic treatment. We first derive relativistic formal solutions. We then iteratively solve the relativistic transfer equation for several cases such as radiative equilibrium or local thermodynamic equilibrium, and obtain specific intensities in the inertial and comoving frames, as well as moment quantities and the Eddington factor. Moment quantities are rather different in each case, but the behavior of the Eddington factor for the plane-parallel case is quite similar in all cases. The Eddington factor generally depends on the flow velocity v as well as the optical depth ?. In the case of relativistic plane-parallel flows, in an optically thin regime of ? ? 1, it is slightly larger than 1/3 at very slow speed, it becomes smaller than 1/3 at mildly relativistic speed, and it again increases up to unity in the highly relativistic case. At highly relativistic speed, on the other hand, it becomes larger than 1/3 even in an optically thick regime. We find the Eddington approximation is fairly good, except for ? ? 1 or v/c ? 0.9, although the moment formalism under the Eddington approximation has some defects at v/c=1/?{3}.

Fukue, Jun

2014-07-01

47

Massive stars near the Eddington-limit, pulsations & mass-loss  

NASA Astrophysics Data System (ADS)

Very massive stars (in excess of ~ 100 M ?) and massive stars in pre-SN phases at the end of their evolution are continuously approaching the Eddington limit. According to our theoretical predictions their high Eddington factors lead to a peculiar sub-photospheric structure and enhanced mass-loss. Their proximity to the Eddington limit is thus likely the reason why these objects appear as LBVs and WR stars. Here we discuss how our predictions relate to the characteristics of strange-mode pulsations, and how rotating massive stars at low metallicities can produce spectroscopic signatures that have recently been observed in a sample of star-forming galaxies at redshifts z ~ 2 - 4.

Gräfener, G.

2015-01-01

48

Super-Eddington mechanical power of an accreting black hole in M83.  

PubMed

Mass accretion onto black holes releases energy in the form of radiation and outflows. Although the radiative flux cannot substantially exceed the Eddington limit, at which the outgoing radiation pressure impedes the inflow of matter, it remains unclear whether the kinetic energy flux is bounded by this same limit. Here, we present the detection of a radio-optical structure, powered by outflows from a non-nuclear black hole. Its accretion disk properties indicate that this black hole is less than 100 solar masses. The optical-infrared line emission implies an average kinetic power of 3 × 10(40) erg second(-1), higher than the Eddington luminosity of the black hole. These results demonstrate kinetic power exceeding the Eddington limit over a sustained period, which implies greater ability to influence the evolution of the black hole's environment. PMID:24578533

Soria, R; Long, K S; Blair, W P; Godfrey, L; Kuntz, K D; Lenc, E; Stockdale, C; Winkler, P F

2014-03-21

49

Einstein Books for Adults  

NSDL National Science Digital Library

This reference list has more than 15 books and articles on Einstein that are written for adults, including biographies and some of Einstein's own writings. For each title, the author's name, publisher, and publication date are included.

50

Albert Einstein's Methodology  

E-print Network

This paper discusses Einstein's methodology. 1. Einstein characterized his work as a theory of principle and reasoned that beyond kinematics, the 1905 heuristic relativity principle could offer new connections between non-kinematical concepts. 2. Einstein's creativity and inventiveness and process of thinking; invention or discovery. 3. Einstein considered his best friend Michele Besso as a sounding board and his class-mate from the Polytechnic Marcel Grossman, as his active partner. Yet, Einstein wrote to Arnold Sommerfeld that Grossman will never claim to be considered a co-discoverer of the Einstein-Grossmann theory. He only helped in guiding Einstein through the mathematical literature, but contributed nothing of substance to the results of the theory. Hence, Einstein neither considered Besso or Grossmann as co-discoverers of the relativity theory which he invented.

Weinstein, Galina

2012-01-01

51

Posing Einstein's Question: Questioning Einstein's Pose.  

ERIC Educational Resources Information Center

Discusses the events surrounding a famous picture of Albert Einstein in which he poses near a blackboard containing a tensor form of his 10 field equations for pure gravity with a question mark after it. Speculates as to the content of Einstein's lecture and the questions he might have had about the equation. (Contains over 30 references.) (WRM)

Topper, David; Vincent, Dwight E.

2000-01-01

52

Einstein's Philosophy of Science  

E-print Network

interest, not only because of his contributions to science, but also because he spoke in great detail about his own philosophy, is Albert Einstein. This paper will cover only three main aspects of Einstein's philosophy of science: the nature... Einstein, On The Method of Theoretical Physics (New York: Oxford University Press, 1933), "p. 6. Albert Einstein, The Philosophy of Bertrand Russell, The Libary of Living Philosophers, vol. V, ed. Paul A. Schilpp, rpt. in Ideas and Opinions, Albert...

Holmer, Bruce

53

A LONG, LONG time ago: geologic timescales  

NSDL National Science Digital Library

Each student randomly picks a card with a geologic event (written description and an image) on it. A timeline has 11 events, not including the formation of the Earth and today. Students attach their event where they think it should go on a 45.5' timeline (in the hallway) made out of paper adding tape and mark the location on the timeline. They return to the classroom and receive a list of age dates for each event. Each group figures out the scale (1 foot = 100 million years) and then moves their events to the correct locations. Students are asked how the position of the events changed, and answer other questions that reinforce the difference between human timescales and geologic timescales. The powerpoint file below contains a template for making geologic event labels for the index cards. Instructors can tailor the geologic event list to fit their course.

Johnson, Elizabeth

54

Einstein as Evaluator?  

ERIC Educational Resources Information Center

Like any other person, Albert Einstein was an informal evaluator, engaged in placing value on various aspects of his life, work, and the world. Based on Einstein's own statements, this paper speculates about what Einstein would have been like as a connoisseur evaluator, a conceptual evaluator, or a responsive evaluator. (Author/BW)

Caulley, Darrel N.

1982-01-01

55

Passive optical limiting in long timescales  

NASA Astrophysics Data System (ADS)

From its use in medicine to measure and/or probe various physiologies to commercial applications such as data storage on optical disks, the laser has positively contributed to the lives of people around the globe. Alongside it's unique properties, the control of laser light poses significant challenges. Optical limiting, or the truncation of optical energy at particular thresholds represents one such challenge. Given the plethora of radiation sources available, it is of significant value to identify a means by which optical limiting can be achieved simultaneously for a wide berth of source parameters. That said, this document focuses on the exploration of a particular optical limiting modality applied to long timescales; That is, optical pulses with durations on the order of hundreds of nanoseconds, microseconds and up to continuous-wave. Given that this modality has been previously shown to be broadband and effective in short timescales, evidence of it's efficacy in long timescales would demonstrate the modality as an exceptional option in the design of truly robust optical limiting devices. The results of L34 optical limiting research with incident laser light at a 750nm wavelength and pulse durations in the microsecond and nanosecond regimes as well as continuous-wave light at 532nm are shown and discussed. Results are discussed for both bulk and liquid-infiltrated capillary-array arrangements and for various output light collection configurations. The mechanisms by which limiting action occurs are discussed and their optimization within various configurations is considered. Through measurement in a variety of experimental situations and device configurations, the organic liquid L34 is shown to be an effective optical limiting material in long timescales. When combined with the fiber array architecture, these results provide evidence that L34 is an excellent candidate for use as a spectrally and temporally robust optical limiting system that is easy to construct and maintain.

Stinger, Michael Vincent

56

Tuning up Mind's Pattern to Nature's Own Idea : Eddington's Early Twenties Case  

E-print Network

Tuning up Mind's Pattern to Nature's Own Idea : Eddington's Early Twenties Case for Variational intended to embody the mind's collusion with nature by linking atomicity of matter with atomicity of action, variational derivatives were at first assigned a dual role requiring of them not only to express mind

Boyer, Edmond

57

An expedition to heal the wounds of war. The 1919 eclipse and Eddington as Quaker adventurer  

Microsoft Academic Search

The 1919 eclipse expedition's confirmation of general relativity is often celebrated as a triumph of scientific internationalism. However, British scientific opinion during World War I leaned toward the permanent severance of intellectual ties with Germany. That the expedition came to be remembered as a progressive moment of internationalsm was largely the result of the efforts of A. S. Eddington. A

Matthew Stanley

2003-01-01

58

Einstein x-ray observations of cataclysmic variables  

SciTech Connect

Observations with the imaging x-ray detectors on the Einstein Observatory have led to a large increase in the number of low luminosity x-ray sources known to be associated with cataclysmic variable stars (CVs). The high sensitivity of the Einstein instrumentation has permitted study of their short timescale variability and spectra. The data are adding significantly to our knowledge of the accretion process in cataclysmic variables and forcing some revision in our ideas concerning the origin of the optical variability in these stars.

Mason, K.O.; Cordova, F.A.

1982-01-01

59

A Century of Einstein  

NSDL National Science Digital Library

This intriguing MSNBC website addresses how Einstein's theories still affect the world we live in today. Users can view a Macromedia Flash Player-enhanced slide show summarizing Einstein's life and major accomplishments. Visitors can download the five papers from 1905, Einstein's "miracle year." Students can find a helpful interactive module discussing the principles of relativity and its importance. The website discusses Einstein's personality and beliefs and hypothesizes how Einstein might have faired in today's world. Users can learn about the questions dealing with dark matter and dark energy that scientists are still trying to understand today.

60

The formation of trapped surfaces in spherically-symmetric Einstein-Euler spacetimes with bounded variation  

E-print Network

We study the evolution of a self-gravitating compressible fluid in spherical symmetry and we prove the existence of weak solutions with bounded variation for the Einstein-Euler equations of general relativity. We formulate the initial value problem in Eddington-Finkelstein coordinates and prescribe spherically symmetric data on a characteristic initial hypersurface. We introduce here a broad class of initial data which contain no trapped surfaces, and we then prove that their Cauchy development contains trapped surfaces. We therefore establish the formation of trapped surfaces in weak solutions to the Einstein equations. This result generalizes a theorem by Christodoulou for regular vacuum spacetimes (but without symmetry restriction). Our method of proof relies on a generalization of the "random choice" method for nonlinear hyperbolic systems and on a detailed analysis of the nonlinear coupling between the Einstein equations and the relativistic Euler equations in spherical symmetry.

Annegret Y. Burtscher; Philippe G. LeFloch

2014-11-11

61

Advances in time-scale algorithms  

NASA Technical Reports Server (NTRS)

The term clock is usually used to refer to a device that counts a nearly periodic signal. A group of clocks, called an ensemble, is often used for time keeping in mission critical applications that cannot tolerate loss of time due to the failure of a single clock. The time generated by the ensemble of clocks is called a time scale. The question arises how to combine the times of the individual clocks to form the time scale. One might naively be tempted to suggest the expedient of averaging the times of the individual clocks, but a simple thought experiment demonstrates the inadequacy of this approach. Suppose a time scale is composed of two noiseless clocks having equal and opposite frequencies. The mean time scale has zero frequency. However if either clock fails, the time-scale frequency immediately changes to the frequency of the remaining clock. This performance is generally unacceptable and simple mean time scales are not used. First, previous time-scale developments are reviewed and then some new methods that result in enhanced performance are presented. The historical perspective is based upon several time scales: the AT1 and TA time scales of the National Institute of Standards and Technology (NIST), the A.1(MEAN) time scale of the US Naval observatory (USNO), the TAI time scale of the Bureau International des Poids et Measures (BIPM), and the KAS-1 time scale of the Naval Research laboratory (NRL). The new method was incorporated in the KAS-2 time scale recently developed by Timing Solutions Corporation. The goal is to present time-scale concepts in a nonmathematical form with as few equations as possible. Many other papers and texts discuss the details of the optimal estimation techniques that may be used to implement these concepts.

Stein, S. R.

1993-01-01

62

Formation of Millisecond Pulsars with Heavy White Dwarf Companions: Extreme Mass Transfer on Subthermal Timescales.  

PubMed

We have performed detailed numerical calculations of the nonconservative evolution of close X-ray binary systems with intermediate-mass (2.0-6.0 M middle dot in circle) donor stars and a 1.3 M middle dot in circle accreting neutron star. We calculated the thermal response of the donor star to mass loss in order to determine its stability and follow the evolution of the mass transfer. Under the assumption of the "isotropic reemission model," we demonstrate that in many cases it is possible for the binary to prevent a spiral-in and survive a highly super-Eddington mass transfer phase (1timescale if the convective envelope of the donor star is not too deep. These systems thus provide a new formation channel for binary millisecond pulsars with heavy CO white dwarfs and relatively short orbital periods (3-50 days). However, we conclude that to produce a binary pulsar with a O-Ne-Mg white dwarf or Porb approximately 1 day (e.g., PSR B0655+64) the above scenario does not work, and a spiral-in phase is still considered the most plausible scenario for the formation of such a system. PMID:10655173

Tauris; van Den Heuvel EP; Savonije

2000-02-20

63

AIDS Arises and Einstein Responds  

E-print Network

and Friends of Albert Einstein College of Medicine of Yeshiva University #12;2 EinstEin : summEr/fall 2011 The magazine for alumni, faculty, students, friends and supporters of albert einstein College of medicine.yu.edu Website: www.einstein.yu.edu Copyright © 2011 albert einstein College of medicine of Yeshiva university

Yates, Andrew

64

STP Einstein Solids Program  

NSDL National Science Digital Library

The STP EinsteinSolids program displays the energy distribution of an Einstein solid in thermal contact with another Einstein solid. The purpose of this program is to explore the distribution of energy between two systems in thermal contact. The default state is two Einstein solids, system A and system B of with 4 particles each, and energies 10 and 2, respectively. Additional states and parameters can be specified using the Display|Switch GUI menu item. STP EinsteinSolids is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp_EinsteinSolids.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-05-28

65

Neuromythology of Einstein's brain.  

PubMed

The idea that the brain of the great physicist Albert Einstein is different from "average" brains in both cellular structure and external shape is widespread. This belief is based on several studies examining Einstein's brain both histologically and morphologically. This paper reviews these studies and finds them wanting. Their results do not, in fact, provide support for the claim that the structure of Einstein's brain reflects his intellectual abilities. PMID:24836969

Hines, Terence

2014-07-01

66

Einstein in Time  

NSDL National Science Digital Library

This fun Web site is part of OLogy, where kids can collect virtual trading cards and create projects with them. Here, they are introduced to Einstein's scientific and humanitarian pursuits with two engaging, kid-friendly sections: Einstein in Time, a fascinating look at the major events in his life presented in a timeline and Everyday Einstein: Humanitarian, a quick overview of how he used his fame to draw attention to the things he believed in.

67

On the accuracy of the Eddington approximation for radiative transfer in the microwave frequencies  

NASA Technical Reports Server (NTRS)

The paper examines how well an Eddington approximation can reproduce brightness temperatures obtained from a more complete, N-stream discrete ordinate solution in the microwave regime. Radiation propagation through a plane parallel medium is considered. Although model discrepancies are complicated functions of the cloud constituents, the differences between an eight-stream discrete ordinate solution and an analytical Eddington solution were found to be generally small, ranging from 0 to 6 K when only one uniform layer of hydrometeors was considered. When realistic multilayered cloud hydrometeor profiles were used, the differences between these two models never exceeded 3 K over the entire range of microwave frequencies considered (6.6-183 GHz). The models agreed to within 0.2 K in the absence of scattering constituents.

Kummerow, Christian

1993-01-01

68

Tensor-to-scalar ratio in Eddington-inspired Born-Infeld inflation  

NASA Astrophysics Data System (ADS)

We investigate the scalar perturbation of the inflation model driven by a massive scalar field in Eddington-inspired Born-Infeld gravity. We focus on the perturbation at the attractor stage in which the first and the second slow-roll conditions are satisfied. The scalar perturbation exhibits the corrections to the chaotic inflation model in general relativity. We find that the tensor-to-scalar ratio becomes smaller than that of the usual chaotic inflation.

Cho, Inyong; Singh, Naveen K.

2014-11-01

69

V4641Sgr - A super-Eddington source enshrouded by an extended envelope  

NASA Astrophysics Data System (ADS)

Optical spectroscopy of an unusual fast transient V4641 Sgr constrains its mass to be 8.7-11.7 Msun (9.6 Msun is the best fit value) and the distance to 7.4-12.3 kpc (Orosz et al. \\cite{orosz}). At this distance the peak flux as measured by ASM/RXTE in 2-12 keV energy band implies the X-ray luminosity exceeding 2-3x 1039 erg s-1, i.e. near or above the Eddington limit for a 9.6 Msun black hole. Optical photometry shows that at the peak of the optical outburst the visual magnitude increased by Delta mV >~ 4.7m relative to the quiescent level and reached mV<~ 8.8m. An assumption that this optical emission is due to the irradiated surface of an accretion disk or a companion star with a black body spectrum would mean that the bolometric luminosity of the system exceeds >~ 3 x 1041 erg s-1 ~ 300 LEdd. We argue that the optical data strongly suggest the presence of an extended envelope surrounding the source which absorbs X-ray flux and reemits it in the optical and UV. The data also suggest that this envelope should be optically thin in UV, EUV and soft X-rays. The observed properties of V4641 Sgr at the peak of an optical flare are very similar to those of SS433. This envelope is likely the result of a near- or super-Eddington rate of mass accretion onto the black hole. The envelope vanishes during subsequent evolution of the source when the apparent luminosity drops well below the Eddington value. Thus this transient source provides us with direct proof of the dramatic change in the character of an accretion flow at the mass accretion rate near or above the critical Eddington value as predicted long ago by the theoretical models.

Revnivtsev, M.; Sunyaev, R.; Gilfanov, M.; Churazov, E.

2002-04-01

70

Relativistic timescale analysis suggests lunar theory revision  

NASA Technical Reports Server (NTRS)

The SI second of the atomic clock was calibrated to match the Ephemeris Time (ET) second in a mutual four year effort between the National Physical Laboratory (NPL) and the United States Naval Observatory (USNO). The ephemeris time is 'clocked' by observing the elapsed time it takes the Moon to cross two positions (usually occultation of stars relative to a position on Earth) and dividing that time span into the predicted seconds according to the lunar equations of motion. The last revision of the equations of motion was the Improved Lunar Ephemeris (ILE), which was based on E. W. Brown's lunar theory. Brown classically derived the lunar equations from a purely Newtonian gravity with no relativistic compensations. However, ET is very theory dependent and is affected by relativity, which was not included in the ILE. To investigate the relativistic effects, a new, noninertial metric for a gravitated, translationally accelerated and rotating reference frame has three sets of contributions, namely (1) Earth's velocity, (2) the static solar gravity field and (3) the centripetal acceleration from Earth's orbit. This last term can be characterized as a pseudogravitational acceleration. This metric predicts a time dilation calculated to be -0.787481 seconds in one year. The effect of this dilation would make the ET timescale run slower than had been originally determined. Interestingly, this value is within 2 percent of the average leap second insertion rate, which is the result of the divergence between International Atomic Time (TAI) and Earth's rotational time called Universal Time (UT or UTI). Because the predictions themselves are significant, regardless of the comparison to TAI and UT, the authors will be rederiving the lunar ephemeris model in the manner of Brown with the relativistic time dilation effects from the new metric to determine a revised, relativistic ephemeris timescale that could be used to determine UT free of leap second adjustments.

Deines, Steven D.; Williams, Carol A.

1995-01-01

71

Planetary Chaotic Zone Clearing: Destinations and Timescales  

NASA Astrophysics Data System (ADS)

We investigate the orbital evolution of particles in a planet's chaotic zone to determine their final destinations and their timescales of clearing. There are four possible final states of chaotic particles: collision with the planet, collision with the star, escape, or bounded but non-collision orbits. In our investigations, within the framework of the planar circular restricted three body problem for planet-star mass ratio ? in the range 10–9 to 10–1.5, we find no particles hitting the star. The relative frequencies of escape and collision with the planet are not scale-free, as they depend upon the size of the planet. For planet radius Rp >= 0.001 RH where RH is the planet's Hill radius, we find that most chaotic zone particles collide with the planet for ? <~ 10–5 particle scattering to large distances is significant only for higher mass planets. For fixed ratio Rp /RH , the particle clearing timescale, T cl, has a broken power-law dependence on ?. A shallower power law, T cl ~ ?–1/3, prevails at small ? where particles are cleared primarily by collisions with the planet; a steeper power law, T cl ~ ?–3/2, prevails at larger ? where scattering dominates the particle loss. In the limit of vanishing planet radius, we find T cl ? 0.024 ?–3/2. The interior and exterior boundaries of the annular zone in which chaotic particles are cleared are increasingly asymmetric about the planet's orbit for larger planet masses; the inner boundary coincides well with the classical first order resonance overlap zone, ?a cl, int ~= 1.2 ?0.28 ap ; the outer boundary is better described by ?a cl, ext ~= 1.7 ?0.31 ap , where ap is the planet-star separation.

Morrison, Sarah; Malhotra, Renu

2015-01-01

72

Quantifying population structure on short timescales.  

PubMed

Quantifying the contribution of the various processes that influence population genetic structure is important, but difficult. One of the reasons is that no single measure appropriately quantifies all aspects of genetic structure. An increasing number of studies is analysing population structure using the statistic D, which measures genetic differentiation, next to G(ST) , which quantifies the standardized variance in allele frequencies among populations. Few studies have evaluated which statistic is most appropriate in particular situations. In this study, we evaluated which index is more suitable in quantifying postglacial divergence between three-spined stickleback (Gasterosteus aculeatus) populations from Western Europe. Population structure on this short timescale (10?000 generations) is probably shaped by colonization history, followed by migration and drift. Using microsatellite markers and anticipating that D and G(ST) might have different capacities to reveal these processes, we evaluated population structure at two levels: (i) between lowland and upland populations, aiming to infer historical processes; and (ii) among upland populations, aiming to quantify contemporary processes. In the first case, only D revealed clear clusters of populations, putatively indicative of population ancestry. In the second case, only G(ST) was indicative for the balance between migration and drift. Simulations of colonization and subsequent divergence in a hierarchical stepping stone model confirmed this discrepancy, which becomes particularly strong for markers with moderate to high mutation rates. We conclude that on short timescales, and across strong clines in population size and connectivity, D is useful to infer colonization history, whereas G(ST) is sensitive to more recent demographic events. PMID:22646231

Raeymaekers, Joost A M; Lens, Luc; Van den Broeck, Frederik; Van Dongen, Stefan; Volckaert, Filip A M

2012-07-01

73

Einstein Educator's Guide Insert  

NSDL National Science Digital Library

This printable two-page handout includes a timeline of Einstein's life that showcases the causes he supported, along with his scientific discoveries and a copy of the letter Einstein sent to the editor of a Japanese magazine in 1952, in which he explains why he signed the letter to President Roosevelt that advocated atomic energy research.

74

When Art Meets Einstein  

ERIC Educational Resources Information Center

This article deals with a pale blue sculpture entitled "A New World View", as an homage to the most famous scientist in modern history, Albert Einstein. It has 32 bas-relief squares composed of glass and steel that represent one aspect of the life and legacy of Albert Einstein. Images of children's faces peer out from behind the glass squares,…

Science Scope, 2006

2006-01-01

75

Einstein Papers Project  

NSDL National Science Digital Library

This is the website for a project hosted by the California Institute of Technology to collect all of Albert Einstein's papers into a single series. The papers cover everything from relativity and quantum mechanics to pacifism and Zionism. The website also includes a link to the Princeton University Press for many published papers by Einstein.

2009-06-15

76

SHORT TIMESCALE VARIATIONS IN THE ATMOSPHERE OF ANTARES A  

SciTech Connect

We analyze three years of high-resolution spectroscopic data and find radial velocity variations with a characteristic timescale of 100 ± 6 days that are nearly sinusoidal. Simultaneous variations in line-depth ratios imply temperature variations of up to 100 K. No photometric variation is seen on a 100 day timescale. The timescale of the variation and its resonant nature suggest solar-like oscillations driven by large-scale convection.

Pugh, T.; Gray, David F., E-mail: tpugh@uwo.ca [Department of Physics and Astronomy, Western University, London, ON (Canada)

2013-11-01

77

A hierarchy of intrinsic timescales across primate cortex.  

PubMed

Specialization and hierarchy are organizing principles for primate cortex, yet there is little direct evidence for how cortical areas are specialized in the temporal domain. We measured timescales of intrinsic fluctuations in spiking activity across areas and found a hierarchical ordering, with sensory and prefrontal areas exhibiting shorter and longer timescales, respectively. On the basis of our findings, we suggest that intrinsic timescales reflect areal specialization for task-relevant computations over multiple temporal ranges. PMID:25383900

Murray, John D; Bernacchia, Alberto; Freedman, David J; Romo, Ranulfo; Wallis, Jonathan D; Cai, Xinying; Padoa-Schioppa, Camillo; Pasternak, Tatiana; Seo, Hyojung; Lee, Daeyeol; Wang, Xiao-Jing

2014-12-01

78

Einstein and Planck  

NASA Astrophysics Data System (ADS)

As an editor of the Annalen der Physik, Max Planck published Einstein's early papers on thermodynamics and on special relativity, which Planck probably was the first major physicist to appreciate. They respected one another not only as physicists but also, for their inspired creation of world pictures, as artists. Planck helped to establish Einstein in a sinecure at the center of German physics, Berlin. Despite their differences in scientific style, social life, politics, and religion, they became fast friends. Their mutual admiration survived World War I, during which Einstein advocated pacifism and Planck signed the infamous Manifesto of the 93 Intellectuals supporting the German invasion of Belgium. It also survived the Weimar Republic, which Einstein favored and Planck disliked. Physics drew them together, as both opposed the Copenhagen Interpretation; so did common decency, as Planck helped to protect Einstein from anti-semitic attacks. Their friendship did not survive the Nazis. As a standing secretary of the Berlin Academy, Planck had to advise Einstein to resign from it before his colleagues, outraged at his criticism of the new Germany from the safety of California, expelled him. Einstein never forgave his old friend and former fellow artist for not protesting publicly against his expulsion and denigration, and other enormities of National Socialism. .

Heilbron, John

2005-03-01

79

Einstein and Millikan  

NASA Astrophysics Data System (ADS)

Albert Einstein traveled to America by boat during the great depression to consult with scientists at the California Institute of Technology. He was a theoretical physicist, a Nobel Prize winner, and a 20th century folk hero. Few members of the general public understood his theories, but they idolized him all the same. The invitation came from physicist Robert Millikan, who had initiated a visiting-scholars program at Caltech shortly after he became head of the school in 1921. Einstein's visits to the campus in 1931, 1932, and 1933 capped Millikan's campaign to make Caltech one of the physics capitals of the world. Mount Wilson astronomer Edwin Hubble's discovery that redshifts are proportional to their distances from the observer challenged Einstein's cosmological picture of a static universe. The big question at Caltech in 1931 was whether Einstein would give up his cosmological constant and accept the idea of an expanding universe. By day, Einstein discussed his theory and its interpretation at length with Richard Tolman, Hubble, and the other scientists on the campus. By night, Einstein filled his travel diary with his personal impressions. During his third visit, Einstein sidestepped as long as possible the question of whether conditions in Germany might prevent his return there. After the January 30 announcement that Hitler had become chancellor of Germany, the question could no longer be evaded. He postponed his return trip for a few weeks and then went to Belgium for several months instead of to Berlin. In the fall of 1933, Albert Einstein returned to the United States as an emigre and became a charter member of Abraham Flexner's new Institute for Advanced Study in Princeton, New Jersey. Why did Einstein go to Princeton and not Pasadena?

Erwin, Charlotte

2005-03-01

80

PHYSICS AND REALITY. ALBERT EINSTEIN.  

E-print Network

PHYSICS AND REALITY. BY ALBERT EINSTEIN. (Translation by Jean Piccard.) § I. GENERALCONSIDERATION " of their connection. But even the concept of the Copyright, 1936, by Albert Einstein. 349 www.kostic.niu.eduHosted by Prof. M. Kostic at: Physics and Reality by Albert Einstein #12;35 ° ALBERT EINSTEIN. [J. F. I. " real

Kostic, Milivoje M.

81

The stolen brain of Einstein  

Microsoft Academic Search

Pathologist Thomas Stoltz Harvey performed an autopsy on Einstein after his death in 1955. During the autopsy Harvey removed Einstein's brain, took pictures of it and then cut it into several pieces. A lot of scientific attention has been devoted to Einstein' brain, and it still comes up once in a while. We've all heard something or other about Einstein's

Kavan Modi

2008-01-01

82

Personal Recollections of Albert Einstein  

Microsoft Academic Search

My grandparents were good friends of Albert Einstein in Berlin. Later my parents also were on friendly terms with him. I had the opportunity to meet Einstein four times after my parents and I came to the United States in 1940. My parents and I, on occasion, had correspondence with Einstein and took a few photos of him. Albert Einstein

Steven Moszkowski

2005-01-01

83

Einstein and 1905  

NASA Astrophysics Data System (ADS)

From March 17 to September 29, 1905, just over six months, Einstein wrote five papers that shifted the tectonic foundations of physics and changed the face of Nature. Three of these papers, the March paper presenting the particle of light, the May paper on Brownian motion, and the June paper on the Special Theory of Relativity are universally recognized as fundamental; however, the Brownian motion paper cannot be divorced from Einstein's April paper, A New Determination of the Dimensions of Molecules, and the September paper that gave the world its most famous equation, E = mc^2, cannot be separated from the June paper. These five papers reveal characteristics of Einstein's approach to physics.

Rigden, John

2005-05-01

84

The Discovery of Timescale-dependent Color Variability of Quasars  

NASA Astrophysics Data System (ADS)

Quasars are variable on timescales from days to years in UV/optical and generally appear bluer while they brighten. The physics behind the variations in fluxes and colors remains unclear. Using Sloan Digital Sky Survey g- and r-band photometric monitoring data for quasars in Stripe 82, we find that although the flux variation amplitude increases with timescale, the color variability exhibits the opposite behavior. The color variability of quasars is prominent at timescales as short as ~10 days, but gradually reduces toward timescales up to years. In other words, the variable emission at shorter timescales is bluer than that at longer timescales. This timescale dependence is clearly and consistently detected at all redshifts from z = 0 to 3.5; thus, it cannot be due to contamination to broadband photometry from emission lines that do not respond to fast continuum variations. The discovery directly rules out the possibility that simply attributes the color variability to contamination from a non-variable redder component such as the host galaxy. It cannot be interpreted as changes in global accretion rate either. The thermal accretion disk fluctuation model is favored in the sense that fluctuations in the inner, hotter region of the disk are responsible for short-term variations, while longer-term and stronger variations are expected from the larger and cooler disk region. An interesting implication is that one can use quasar variations at different timescales to probe disk emission at different radii.

Sun, Yu-Han; Wang, Jun-Xian; Chen, Xiao-Yang; Zheng, Zhen-Ya

2014-09-01

85

Chemical Timescales in the Atmospheres of Highly Eccentric Exoplanets  

NASA Astrophysics Data System (ADS)

Close-in exoplanets with highly eccentric orbits are subject to large variations in incoming stellar flux between periapse and apoapse. These variations may lead to large swings in atmospheric temperature, which in turn may cause changes in the chemistry of the atmosphere from relatively higher CO abundances at periapse to relatively higher CH4 abundances at apoapse. Here we examine chemical timescales for CO<->CH4 interconversion compared to orbital timescales and vertical mixing timescales for the highly eccentric exoplanets HAT-P-2b and CoRoT-10b. As exoplanet atmospheres cool, the chemical timescales for CO<->CH4 tend to exceed orbital and/or vertical mixing timescales, leading to quenching. The relative roles of orbit-induced thermal quenching and vertical quenching depend upon mixing timescales relative to orbital timescales. For both HAT-P-2b and CoRoT-10b, vertical quenching will determine disequilibrium CO<->CH4 chemistry at faster vertical mixing rates, whereas orbit-induced thermal quenching may play a significant role at slower mixing rates. The general abundance and chemical timescale results - calculated as a function of pressure, temperature, and metallicity - can be applied for different atmospheric profiles in order to estimate the quench level and disequilibrium abundances of CO and CH4 on hydrogen-dominated exoplanets. Observations of CO and CH4 on highly eccentric exoplanets may yield important clues to the chemical and dynamical properties of their atmospheres.

Visscher, Channon

2012-10-01

86

Einstein in Wyoming.  

ERIC Educational Resources Information Center

Describes "Einstein's Adventurarium," a science center housed in an empty shopping mall in Gillette, Wyoming, created through school, business, and city-county government partnership. Describes how interactive exhibits allow exploration of life sciences, physics, and paleontology. (KDFB)

Elliot, Ian

1996-01-01

87

Once Upon Einstein  

NSDL National Science Digital Library

This book provides a description of Einstein's work through imagined scenes from his life. Topics covered include time, relativity, and quantum physics. Simple, non-mathematical analogies are used to explain the physics.

Damour, Thibault

2007-01-28

88

Einstein's Miraculous Year  

E-print Network

With each passing year, the young Albert Einstein's achievements in physics in the year 1905 seem to be ever more miraculous. We describe why the centenary of this remarkable year is worthy of celebration.

Natarajan, Vasant; Mukunda, N

2013-01-01

89

Event Rate and Einstein Time Evaluation in Pixel Microlensing  

SciTech Connect

In previous work it has been shown that a flux-weighted FWHM timescale of a microlensing event can be used as an unbiased estimator of the optical depth. For the first time, this allows the optical depth, which is effectively the microlensing probability, to be easily estimated from pixel microlensing data. In this paper we derive analytic expressions for the observed rate of pixel lensing events as a function of the FWHM timescale. This contrasts works in the literature that express rates in terms of an ''event duration'' or Einstein time, which require knowledge of the magnification, which is difficult to determine in a pixel event. The FWHM is the most directly measured timescale. We apply these results to possible pixel lensing surveys, using the Hubble Space Telescope (HST) for M87 and the Canada-France-Hawaii Telescope (CFHT) for M31. We predict M87 microlensing rates for the HST Advanced Camera and for the Next-Generation Space Telescope (NGST), and demonstrate that one will be able to probe the stellar initial mass function (IMF). Next, we describe a new method by which a crude measurement of the magnification can be made in the regime of magnifications A{approx}10-100. This in turn gives a crude measurement of the Einstein time. This program requires good photometry and sampling in the low-magnification tails of an event, but is feasible with today's technology. (c) 2000 The American Astronomical Society.

Baltz, Edward A.; Silk, Joseph

2000-02-20

90

Direct dark matter event rates with a velocity distribution in the Eddington approach  

SciTech Connect

Exotic dark matter together with the vacuum energy (associated with the cosmological constant) seem to dominate the Universe. Thus its direct detection is central to particle physics and cosmology. Supersymmetry provides a natural dark matter candidate, the lightest supersymmetric particle (LSP). One essential ingredient in obtaining the direct detection rates is the density and the velocity distribution of the LSP in our vicinity. In the present paper we study simultaneously density profiles and velocity distributions in the context of the Eddington approach. In such an approach, unlike the commonly assumed Maxwell-Boltzmann (M-B) distribution, the upper bound of the velocity arises naturally from the potential.

Vergados, J. D. [University of Ioannina, Ioannina, GR 45110 (Greece); Owen, D. [Department of Physics, Ben Gurion University (Israel)

2007-02-15

91

A link between ghost-free bimetric and Eddington-inspired Born-Infeld theory  

E-print Network

We provide an auxiliary field formulation of the full ghost-free bimetric theory which avoids the explicit presence of a square-root matrix in the action. This description always allows for a branch of solutions where the auxiliary fields can be integrated out to give back the ghost-free theory. For certain parameter regions the two formulations are dynamically equivalent, but in the general case another branch of solutions also exists. We show that this second branch, with certain restrictions on the parameters of the theory, is dynamically equivalent to Eddington-inspired Born-Infeld gravity. This establishes a definite connection between two seemingly unrelated theories of modified gravity.

Angnis Schmidt-May; Mikael von Strauss

2014-12-11

92

A link between ghost-free bimetric and Eddington-inspired Born-Infeld theory  

E-print Network

We provide an auxiliary field formulation of the full ghost-free bimetric theory which avoids the explicit presence of a square-root matrix in the action. This description always allows for a branch of solutions where the auxiliary fields can be integrated out to give back the ghost-free theory. For certain parameter regions the two formulations are dynamically equivalent, but in the general case another branch of solutions also exists. We show that this second branch, with certain restrictions on the parameters of the theory, is dynamically equivalent to Eddington-inspired Born-Infeld gravity. This establishes a definite connection between two seemingly unrelated theories of modified gravity.

Schmidt-May, Angnis

2014-01-01

93

Einstein equation at singularities  

NASA Astrophysics Data System (ADS)

Einstein's equation is rewritten in an equivalent form, which remains valid at the singularities in some major cases. These cases include the Schwarzschild singularity, the Friedmann-Lemaître-Robertson-Walker Big Bang singularity, isotropic singularities, and a class of warped product singularities. This equation is constructed in terms of the Ricci part of the Riemann curvature (as the Kulkarni-Nomizu product between Einstein's equation and the metric tensor).

Stoica, Ovidiu-Cristinel

2014-02-01

94

Albert Einstein Cancer Center  

Cancer.gov

The Albert Einstein College of Medicine at Yeshiva University was founded in 1955. In 1971, the Albert Einstein Cancer Center (AECC) was established at the medical school and in 1972, AECC became an NCI-designated Cancer Center. AECC is located in the Chanin Research Institute. The Center’s imaging facility, new mouse facilities, and expanded research programs are housed in the newly opened Price Center for Genetic and Translational Medicine.

95

Albert Einstein's Hypothetism  

NASA Astrophysics Data System (ADS)

This paper would like to show that Albert Einstein preceded Karl Popper in formulating the fundamental ideas of the so-called hypothetism. The ideas closest to Popper''s later view were presented by Einstein in a very interesting, yet little known article entitled ''Induction and Deduction in Physics'' published in a Berlin daily Berliner Tageblatt on Christmas Day of 1919. The text and ideas of this article will be presented (with German original appended) and comments will be made on them.

Kostro, Ludwik

96

Profile: Albert Einstein  

NSDL National Science Digital Library

This online article is from the Museum's Seminars on Science, a series of distance-learning courses designed to help educators meet the new national science standards. "Profile: Albert Einstein," part of the Frontiers in Physical Science seminar, briefly covers Einstein's life and work including his Special Theory of Relativity and the paper that gave the world E=mc², his Nobel Prize in Physics, his influence yet exclusion from the Manhattan Project, and his promotion of peace and human rights.

97

Einstein's Big Idea  

NSDL National Science Digital Library

This free digital library resource is tied to standards and includes downloadable video and audio segments, Flash interactives, and more.In this segment, NOVA explores the stories behind E = mc2 and relates how Einstein came to his startling conclusion that mass and energy are two forms of the same thing. A brief biography is given along with Einsteins achievements, and his discoveries about energy, mass, special relativity, and atoms.

2005-11-11

98

The Energy-Dependence of GRB Minimum Variability Timescales  

E-print Network

We constrain the minimum variability timescales for 938 GRBs observed by the Fermi/GBM instrument prior to July 11, 2012. The tightest constraints on progenitor radii derived from these timescales are obtained from light curves in the hardest energy channel. In the softer bands -- or from measurements of the same GRBs in the hard X-rays from Swift -- we show that variability timescales tend to be a factor 2--3 longer. Applying a survival analysis to account for detections and upper limits, we find median minimum timescale in the rest frame for long-duration and short-duration GRBs of 45 ms and 10 ms, respectively. Fewer than 10% of GRBs show evidence for variability on timescales below 2 ms. These shortest timescales require Lorentz factors $\\gtrsim 400$ and imply typical emission radii $R \\approx 1 {\\times} 10^{14}$ cm for long-duration GRBs and $R \\approx 3 {\\times} 10^{13}$ cm for short-duration GRBs. We discuss implications for the GRB fireball model and investigate whether GRB minimum timescales evolve w...

Golkhou, V Zach; Littlejohns, Owen M

2015-01-01

99

X-RAY OUTFLOWS AND SUPER-EDDINGTON ACCRETION IN THE ULTRALUMINOUS X-RAY SOURCE HOLMBERG IX X-1  

SciTech Connect

Studies of X-ray continuum emission and flux variability have not conclusively revealed the nature of ultraluminous X-ray sources (ULXs) at the high-luminosity end of the distribution (those with L{sub X} {>=} 10{sup 40} erg s{sup -1}). These are of particular interest because the luminosity requires either super-Eddington accretion onto a black hole of mass {approx}10 M{sub Sun} or more standard accretion onto an intermediate-mass black hole. Super-Eddington accretion models predict strong outflowing winds, making atomic absorption lines a key diagnostic of the nature of extreme ULXs. To search for such features, we have undertaken a long, 500 ks observing campaign on Holmberg IX X-1 with Suzaku. This is the most sensitive data set in the iron K bandpass for a bright, isolated ULX to date, yet we find no statistically significant atomic features in either emission or absorption; any undetected narrow features must have equivalent widths less than 15-20 eV at 99% confidence. These limits are far below the {approx}>150 eV lines expected if observed trends between mass inflow and outflow rates extend into the super-Eddington regime and in fact rule out the line strengths observed from disk winds in a variety of sub-Eddington black holes. We therefore cannot be viewing the central regions of Holmberg IX X-1 through any substantial column of material, ruling out models of spherical super-Eddington accretion. If Holmberg IX X-1 is a super-Eddington source, any associated outflow must have an anisotropic geometry. Finally, the lack of iron emission suggests that the stellar companion cannot be launching a strong wind and that Holmberg IX X-1 must primarily accrete via Roche-lobe overflow.

Walton, D. J.; Harrison, F. A. [Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States); Miller, J. M.; Reis, R. C. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Fabian, A. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Roberts, T. P. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Middleton, M. J. [Astronomical Institute Anton Pannekoek, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam (Netherlands)

2013-08-10

100

NOVA: Einstein's Big Idea  

NSDL National Science Digital Library

It is hard to overestimate the importance of Albert Einstein's equation, "Energy equals mass times the speed of light squared." A recent special from NOVA explores many different facets of the lasting and pervasive effects of this revolutionary statement. The website was developed to provide a host of complementary resources to the actual television program, and as such, anyone with even a trace of interest in the history of science or physics will want to take a close look. The interactive features are excellent; they include 10 top physicist's explanation of the famous equation and a timeline of Einstein's life. The essays offered here are also top-notch, and they include a piece titled "Einstein the Nobody" by David Bodanis and "Relativity and the Cosmos" by Alan Lightman.

2005-01-01

101

Chemical Timescales in the Atmospheres of Highly Eccentric Exoplanets  

NASA Astrophysics Data System (ADS)

Close-in exoplanets with highly eccentric orbits are subject to large variations in incoming stellar flux between periapse and apoapse. These variations may lead to large swings in atmospheric temperature, which in turn may cause changes in the chemistry of the atmosphere from higher CO abundances at periapse to higher CH4 abundances at apoapse. Here, we examine chemical timescales for CO\\rightleftarrowsCH4 interconversion compared to orbital timescales and vertical mixing timescales for the highly eccentric exoplanets HAT-P-2b and CoRoT-10b. As exoplanet atmospheres cool, the chemical timescales for CO\\rightleftarrowsCH4 tend to exceed orbital and/or vertical mixing timescales, leading to quenching. The relative roles of orbit-induced thermal quenching and vertical quenching depend upon mixing timescales relative to orbital timescales. For both HAT-P-2b and CoRoT-10b, vertical quenching will determine disequilibrium CO\\rightleftarrowsCH4 chemistry at faster vertical mixing rates (Kzz > 107 cm2 s-1), whereas orbit-induced thermal quenching may play a significant role at slower mixing rates (Kzz < 107 cm2 s-1). The general abundance and chemical timescale results—calculated as a function of pressure, temperature, and metallicity—can be applied for different atmospheric profiles in order to estimate the quench level and disequilibrium abundances of CO and CH4 on hydrogen-dominated exoplanets. Observations of CO and CH4 on highly eccentric exoplanets may yield important clues to the chemical and dynamical properties of their atmospheres.

Visscher, Channon

2012-09-01

102

Einstein-?tsuki vacuum equations  

NASA Astrophysics Data System (ADS)

The generalisation of the Einstein vacuum theory to ?tsuki geometry is considered. It is shown that the theory based on Lagrangian density ?-gR is consistent and leads to a theory that is classically indistinguishable from the Einstein theory.

Smrz, P. K.

1993-01-01

103

Conversations With Albert Einstein. II  

ERIC Educational Resources Information Center

Discusses Einstein's views on the role of Michelson-Morley, Fizeau, and Miller experiments in the development of relativity and his attitude toward the theories of new quantum mechanics. Indicates that Einstein's opposition to quantum mechanics is beyond dispute. (CC)

Shankland, R. S.

1973-01-01

104

Eye on Einstein  

NSDL National Science Digital Library

This OLogy activity challenges students to find nine inventions that Einstein's ideas helped to create. The activity begins with an illustration of Al's Junk Shop. Mixed in with his junk are a Global Positioning System, CD player, computer, calculator, scanner, laser pointer, TV, and representations of both laser surgery and nuclear energy. After making a mental list of their nine choices, students can click to a second page to check their answers. Each invention has a rollover note about how Einstein's ideas helped pave the way for its creation. Alternately, the first page could be printed and used as a handout for an offline activity.

105

Super-Eddington Accretion in the Ultraluminous X-ray Source NGC1313 X-2: An Ephemeral Feast  

E-print Network

We investigate the X-ray spectrum, variability and the surrounding ionized bubble of NGC1313 X-2 to explore the physics of super-Eddington accretion. Beyond the Eddington luminosity, the accretion disk of NGC1313 X-2 is truncated at a large radius ($\\sim$ 50 times of innermost stable circular orbit), and displays the similar evolution track with both luminous Galactic black-hole and neutron star X-ray binaries. In super-critical accretion, the speed of radiatively driven outflows from the inner disk is mildly relativistic. Such ultra-fast outflows would be over ionized and might produce weak Fe K absorption lines, which may be detected by the coming X-ray mission {\\it Astro-H}. If the NGC1313 X-2 is a massive stellar X-ray binary, the high luminosity indicates that an ephemeral feast is held in the source. That is, the source must be accreting at a hyper-Eddington mass rate to give the super-Eddington emission over $\\sim 10^{4}-10^{5}$ yr. The expansion of the surrounding bubble nebula with a velocity of $\\si...

Weng, Shan-Shan; Zhao, Hai-Hui

2013-01-01

106

The Eddington Limit in Cosmic Rays: An Explanation for the Observed Faintness of Starbursting Galaxies  

E-print Network

We show that the luminosity of a star forming galaxy is capped by the production and subsequent expulsion of cosmic rays from its interstellar medium. By defining an Eddington luminosity in cosmic rays, we show that the star formation rate of a given galaxy is limited by its mass content and the cosmic ray mean free path. When the cosmic ray luminosity and pressure reaches a critical value as a result of vigorous star formation, hydrostatic balance is lost, a cosmic ray-driven wind develops, and star formation is choked off. Cosmic ray pressure-driven winds are likely to produce wind velocities significantly in excess of the galactic escape velocity. It is possible that cosmic ray feedback results in the Faber-Jackson relation for a plausible set of input parameters that describe cosmic ray production and transport, which are calibrated by observations of the Milky Way's interstellar cosmic rays as well as other galaxies.

Aristotle Socrates; Shane W. Davis; Enrico Ramirez-Ruiz

2008-01-22

107

Radial oscillations and stability of compact stars in Eddington-inspired Born-Infeld gravity  

NASA Astrophysics Data System (ADS)

We study the hydrostatic equilibrium structure of compact stars in the Eddington-inspired Born-Infeld gravity recently proposed by Bañados and Ferreira [Phys. Rev. Lett. 105, 011101 (2010)]. We also develop a framework to study the radial perturbations and stability of compact stars in this theory. We find that the standard results of stellar stability still hold in this theory. The frequency square of the fundamental oscillation mode vanishes for the maximum-mass stellar configuration. The dependence of the oscillation mode frequencies on the coupling parameter ? of the theory is also investigated. We find that the fundamental mode is insensitive to the value of ?, while higher-order modes depend more strongly on ?.

Sham, Y.-H.; Lin, L.-M.; Leung, P. T.

2012-09-01

108

Radial oscillations and stability of compact stars in Eddington-inspired Born-Infeld gravity  

E-print Network

We study the hydrostatic equilibrium structure of compact stars in the Eddington-inspired Born-Infeld gravity recently proposed by Banados and Ferreira [Phys. Rev. Lett. 105, 011101 (2010)]. We also develop a framework to study the radial perturbations and stability of compact stars in this theory. We find that the standard results of stellar stability still hold in this theory. The frequency square of the fundamental oscillation mode vanishes for the maximum-mass stellar configuration. The dependence of the oscillation mode frequencies on the coupling parameter \\kappa of the theory is also investigated. We find that the fundamental mode is insensitive to the value of \\kappa, while higher order modes depend more strongly on \\kappa.

Y. -H. Sham; L. -M. Lin; P. T. Leung

2012-09-21

109

Compact stars in Eddington-inspired Born-Infeld gravity: Anomalies associated with phase transitions  

E-print Network

We study how generic phase transitions taking place in compact stars constructed in the framework of the Eddington-inspired Born-Infeld (EiBI) gravity can lead to anomalous behavior of these stars. For the case with first-order phase transitions, compact stars in EiBI gravity with a positive coupling parameter $\\kappa $ exhibit a finite region with constant pressure, which is absent in general relativity. However, for the case with a negative $\\kappa $, an equilibrium stellar configuration cannot be constructed. Hence, EiBI gravity seems to impose stricter constraints on the microphysics of stellar matter. Besides, in the presence of spatial discontinuities in the sound speed $c_s$ due to phase transitions, the Ricci scalar is spatially discontinuous and contains $\\delta$-function singularities proportional to the jump in $c_s^2$ acquired in the associated phase transition.

Y. -H. Sham; P. T. Leung; L. -M. Lin

2013-04-09

110

Generalised Eddington approximation for radiative transfer problems in spherically-symmetric moving media  

NASA Astrophysics Data System (ADS)

A moment method with three stream division of the radiation field was suggested by Wilson, Wan and Sen (1980) for solving radiative transfer problems in stationary, nongrey extended shells surrounding a central star. Use was made of the generalized Eddington relations as the closure conditions of the moment equations. In the present paper, the same method has been utilized to study the radiative transfer problems in a nongrey, expanding gaseous spherical shells surrounding a central star. The transfer equation has been set in comoving frame in spherical geometry. The radiation and material quantities, angles and frequencies have been expressed in comoving frame. The mean intensity, flux and K-integrals have been calculated for extensive atmospheres in the presence of different velocity fields.

Sen, K. K.; Wilson, S. J.

1993-05-01

111

HIGH-VELOCITY OUTFLOWS WITHOUT AGN FEEDBACK: EDDINGTON-LIMITED STAR FORMATION IN COMPACT MASSIVE GALAXIES  

SciTech Connect

We present the discovery of compact, obscured star formation in galaxies at z {approx} 0.6 that exhibit {approx}> 1000 km s{sup -1} outflows. Using optical morphologies from the Hubble Space Telescope and infrared photometry from the Wide-field Infrared Survey Explorer, we estimate star formation rate (SFR) surface densities that approach {Sigma}{sub SFR} Almost-Equal-To 3000 M{sub Sun} yr{sup -1} kpc{sup -2}, comparable to the Eddington limit from radiation pressure on dust grains. We argue that feedback associated with a compact starburst in the form of radiation pressure from massive stars and ram pressure from supernovae and stellar winds is sufficient to produce the high-velocity outflows we observe, without the need to invoke feedback from an active galactic nucleus.

Diamond-Stanic, Aleksandar M.; Moustakas, John; Coil, Alison L. [Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92093 (United States); Tremonti, Christy A.; Sell, Paul H. [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States); Hickox, Ryan C. [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States); Robaina, Aday R. [Institut de Ciencies del Cosmos, University of Barcelona, 08028 Barcelona (Spain); Rudnick, Gregory H., E-mail: aleks@ucsd.edu [Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 (United States)

2012-08-20

112

Observational discrimination of Eddington-inspired Born-Infeld gravity from general relativity  

E-print Network

Direct observations of neutron stars could tell us an imprint of modified gravity. However, it is generally difficult to resolve the degeneracy due to the uncertainties in equation of state (EOS) of neutron star matter and in gravitational theories. In this paper, we are successful to find the observational possibility to distinguish Eddington-inspired Born-Infeld gravity (EiBI) from general relativity. We show that the radii of neutron stars with $0.5M_{sun}$ are strongly correlated with the neutron skin thickness of ${}^{208}$Pb independently of EOS, while this correlation depends on the coupling constant in EiBI. As a result, via the direct observations of radius of neutron star with $0.5M_{sun}$ and the measurements of neutron skin thickness of ${}^{208}$Pb by the terrestrial experiments, one could not only discriminate EiBI from general relativity but also estimate the coupling constant in EiBI.

Sotani, Hajime

2014-01-01

113

Observational discrimination of Eddington-inspired Born-Infeld gravity from general relativity  

E-print Network

Direct observations of neutron stars could tell us an imprint of modified gravity. However, it is generally difficult to resolve the degeneracy due to the uncertainties in equation of state (EOS) of neutron star matter and in gravitational theories. In this paper, we are successful to find the observational possibility to distinguish Eddington-inspired Born-Infeld gravity (EiBI) from general relativity. We show that the radii of neutron stars with $0.5M_{sun}$ are strongly correlated with the neutron skin thickness of ${}^{208}$Pb independently of EOS, while this correlation depends on the coupling constant in EiBI. As a result, via the direct observations of radius of neutron star with $0.5M_{sun}$ and the measurements of neutron skin thickness of ${}^{208}$Pb by the terrestrial experiments, one could not only discriminate EiBI from general relativity but also estimate the coupling constant in EiBI.

Hajime Sotani

2014-04-22

114

SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant  

NASA Astrophysics Data System (ADS)

We present observations of SN Hunt 248, a new supernova (SN) impostor in NGC 5806, which began a multi-stage outburst in May 2014. The "2014a" discovery brightening exhibited an absolute magnitude of M ? -12 and the spectral characteristics of a cool dense outflow, with P-Cygni lines of H?, Fe II, and Na I. The source rapidly climbed and peaked at M ? -15 mag after two additional weeks. During this bright "2014b'' phase the spectrum became hotter, dominated by Balmer emission and a stronger blue continuum, similar to the SN impostor SN 1997bs. Archival images from the Hubble Space Telescope between 1997 and 2005 reveal a luminous (4×105 L?) variable precursor star. Its location on the Hertzsprung-Russell diagram is consistent with a massive (Minit ? 30 M?) cool hypergiant having an extremely dense wind and an Eddington ratio (?) just below unity. At the onset of the 2014a brightening, however, the object was super-Eddington (? = 4 - 12). The subsequent boost in luminosity during the 2014b phase probably resulted from circumstellar interaction. SN Hunt 248 provides the first case of a cool hypergiant undergoing a giant eruption reminiscent of outbursts from luminous blue variable stars (LBVs). This lends support to the hypothesis that some cool hypergiants, such as ?Cas, could be LBVs masquerading under a pseudo-photosphere created by their extremely dense winds. Moreover, SN Hunt 248 demonstrates that eruptions stemming from such stars can rival in peak luminosity the giant outbursts of much more massive systems like ?Car.

Mauerhan, Jon; Van Dyk, Schuyler D.; Graham, Melissa Lynn; Zheng, WeiKang; Clubb, Kelsey I.; Filippenko, Alexei V.; Valenti, Stefano; Brown, Peter; Smith, Nathan; Howell, Dale Andrew; Arcavi, Iair

2015-01-01

115

SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant  

NASA Astrophysics Data System (ADS)

We present observations of SN Hunt 248, a new supernova (SN) impostor in NGC 5806, which began a multistage outburst in 2014 May. The `2014a' discovery brightening exhibited an absolute magnitude of M ? -12 and the spectral characteristics of a cool, dense outflow, including P Cygni lines of Fe II, H I, and Na I, and line blanketing from metals. The source rapidly climbed and peaked at M ? -15 mag after two additional weeks. During this bright `2014b' phase the spectrum became dominated by Balmer emission and a stronger blue continuum, similar to the SN impostor SN 1997bs. Archival images from the Hubble Space Telescope between 1997 and 2005 reveal a luminous (4 × 105 L?) variable precursor star. Its location on the Hertzsprung-Russell diagram is consistent with a massive (Minit ? 30 M?) cool hypergiant having an extremely dense wind and an Eddington ratio (?) just below unity. At the onset of the 2014a brightening, however, the object was super-Eddington (? = 4-12). The subsequent boost in luminosity during the 2014b phase probably resulted from circumstellar interaction. SN Hunt 248 provides the first case of a cool hypergiant undergoing a giant eruption reminiscent of outbursts from luminous blue variable stars (LBVs). This lends support to the hypothesis that some cool hypergiants, such as ? Cas, could be LBVs masquerading under a pseudo-photosphere created by their extremely dense winds. Moreover, SN Hunt 248 demonstrates that eruptions stemming from such stars can rival in peak luminosity the giant outbursts of much more massive systems like ? Car.

Mauerhan, Jon C.; Van Dyk, Schuyler D.; Graham, Melissa L.; Zheng, WeiKang; Clubb, Kelsey I.; Filippenko, Alexei V.; Valenti, Stefano; Brown, Peter; Smith, Nathan; Howell, D. Andrew; Arcavi, Iair

2015-02-01

116

THE STAR FORMATION LAWS OF EDDINGTON-LIMITED STAR-FORMING DISKS  

SciTech Connect

Two important avenues into understanding the formation and evolution of galaxies are the Kennicutt-Schmidt (K-S) and Elmegreen-Silk (E-S) laws. These relations connect the surface densities of gas and star formation ({Sigma}{sub gas} and {Sigma}-dot{sub *}, respectively) in a galaxy. To elucidate the K-S and E-S laws for disks where {Sigma}{sub gas} {approx}> 10{sup 4} M{sub Sun} pc{sup -2}, we compute 132 Eddington-limited star-forming disk models with radii spanning tens to hundreds of parsecs. The theoretically expected slopes ( Almost-Equal-To 1 for the K-S law and Almost-Equal-To 0.5 for the E-S relation) are relatively robust to spatial averaging over the disks. However, the star formation laws exhibit a strong dependence on opacity that separates the models by the dust-to-gas ratio that may lead to the appearance of a erroneously large slope. The total infrared luminosity (L{sub TIR}) and multiple carbon monoxide (CO) line intensities were computed for each model. While L{sub TIR} can yield an estimate of the average {Sigma}-dot{sub *} that is correct to within a factor of two, the velocity-integrated CO line intensity is a poor proxy for the average {Sigma}{sub gas} for these warm and dense disks, making the CO conversion factor ({alpha}{sub CO}) all but useless. Thus, observationally derived K-S and E-S laws at these values of {Sigma}{sub gas} that uses any transition of CO will provide a poor measurement of the underlying star formation relation. Studies of the star formation laws of Eddington-limited disks will require a high-J transition of a high density molecular tracer, as well as a sample of galaxies with known metallicity estimates.

Ballantyne, D. R.; Armour, J. N.; Indergaard, J., E-mail: david.ballantyne@physics.gatech.edu [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

2013-03-10

117

The Einstein Toolkit  

NASA Astrophysics Data System (ADS)

The Einstein Toolkit Consortium is developing and supporting open software for relativistic astrophysics. Its aim is to provide the core computational tools that can enable new science, broaden our community, facilitate interdisciplinary research and take advantage of petascale computers and advanced cyberinfrastructure. The Einstein Toolkit currently consists of an open set of over 100 modules for the Cactus framework, primarily for computational relativity along with associated tools for simulation management and visualization. The toolkit includes solvers for vacuum spacetimes as well as relativistic magneto-hydrodynamics, along with modules for initial data, analysis and computational infrastructure. These modules have been developed and improved over many years by many different researchers. The Einstein Toolkit is supported by a distributed model, combining core support of software, tools, and documentation in its own repositories and through partnerships with other developers who contribute open software and coordinate together on development. As of January 2012 it has 68 registered members from 30 research groups world-wide. This talk will present the current capabilities of the Einstein Toolkit and will point to information how to leverage it for future research.

Löffler, Frank

2012-03-01

118

Examining the Enigmatic Einstein  

ERIC Educational Resources Information Center

Albert Einstein is the icon of scientific genius. His is one the most recognizable faces in the history of mankind. This paper takes a cursory look at the man who is commonly perceived to be the epitome of eccentricity. We manage to sum up his salient traits which are associated with his name. The traits are based on anecdotal evidence. This…

Khoon, Koh Aik

2007-01-01

119

Einstein on Brownian Motion  

NSDL National Science Digital Library

This essay by David Cassiday presents the disagreements among physicists at the end of the 19th century over the existence of atoms and the apparent disagreement between mechanics and thermodynamics. Cassiday describes Einstein's prediction of the characteristics of Brownian motion and how this work brought about the acceptance of atomic theory.

2008-04-14

120

Einstein Archives Online  

NSDL National Science Digital Library

Officially released on the Web last week, this impressive digital archive features the writings, scholarship, and thoughts of Albert Einstein, one of the 20th century's greatest scientists. The site allows visitors to view and browse 3,000 high-quality digitized images of Einstein's writings, ranging from his travel diaries (many of which are in German) to his published and unpublished scholarly manuscripts. The online archive draws on the manuscripts held by the Albert Einstein Archives at the Hebrew University of Jerusalem, and was produced by the Jewish National & University Library's Digitization Project. Additionally, visitors have access to the archive database, which contains 43,000 records of Einstein related documents, such as his notebooks and third-party items. More casual visitors will want to visit the online gallery, which contains a selection of some of the key documents available here, such as his famous article that mentions the equation E=mc2. Overall, this is a thoroughly engaging and informative trove of digitized material on one of the world's most respected scientists.

121

Einstein Books for Kids  

NSDL National Science Digital Library

This OLogy reference list has 10 kid-friendly books on physics. A short description is given for each title, along with author name and publisher. The list includes engaging biographies covering Einstein's life and contributions, collections of easy-to-complete science experiments, and illustrated looks at energy, time and space, light, and matter.

122

From Newton to Einstein.  

ERIC Educational Resources Information Center

Discusses the history of scientific thought in terms of the theories of inertia and absolute space, relativity and gravitation. Describes how Sir Isaac Newton used the work of earlier scholars in his theories and how Albert Einstein used Newton's theories in his. (CW)

Ryder, L. H.

1987-01-01

123

When Art Meets Einstein  

NSDL National Science Digital Library

A New World View, a composition of pale blue glass and steel, is an homage to the most famous scientist in modern history -- Albert Einstein. View this masterpiece for yourself by visiting the World Year of Physics (WYP) team's website that includes a number of extension activities to help middle school students explore their understanding and appreciation of science through art.

American Physical Society

2006-02-01

124

Einstein Cannon Model  

NSDL National Science Digital Library

The Einstein Cannon model computes and displays the trajectory of cannonballs (particles) shot from a cannon in the vicinity of a black hole.  It was created for the study of Einstein's theory of general relativity and the Schwarzschild metric.  The main window displays a map of space in the vicinity of the black hole using Schwarzschild coordinates and a cannon located a distance r0 from the center black hole's center.  The position and firing angle of the cannon can be adjusted by dragging a marker and the number of cannon balls and their initial speed can be changed using input fields.  The maximum speed of the cannon ball is the speed of light c=1 in accordance with Einstein's theory.  Newton suggested that a cannon ball fired from a high mountain could fall to Earth, orbit the Earth, or fly away depending on how it was fired.  The same is true in general relativity but there are many important differences.  This model demonstrates these differences. The Einstein Cannon model is a supplemental simulation for the article "When action is not least for orbits in general relativity" by C. G. Gray and Eric Poisson in the American Journal of Physics 79(1), 43-55 (2011) and has been approved by the authors and the American Journal of Physics (AJP) editor. The simulation was developed using the Easy Java Simulations (EJS) modeling tool and is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_gr_EinsteinCannon.jar file will run the program if Java is installed.

Christian, Wolfgang

2010-10-30

125

Timescales of Soil Moisture Anomalies: Results from Two GCMs  

NASA Technical Reports Server (NTRS)

Soil moisture anomalies dissipate over timescales that may span weeks to months. Characterizing the geographical and seasonal variations in these timescales can have important practical benefit; significant soil moisture "memory" allows long-lead forecasts of soil moisture, which have been found in recent studies to be essential for useful Ion--lead forecasts of precipitation in many regions. In this talk, we will present and compare the soil moisture timescales derived in two separate general circulation model (GCM) studies. Both studies employ multiple ensembles of short-term climate simulations. Timescales at a given point are effectively estimated by determining how quickly the soil moisture distribution generated in one ensemble of simulations (characterized by a unique set of initial soil moisture conditions) approaches that produced by another ensemble (characterized by a different set of initial soil moisture conditions). The talk will include a discussion of why the timescales produced by the two GCMs differ in some regions, and it will also describe the impact of soil moisture memory on simulated precipitation.

Koster, Randal D.; Milly, P. C. D.; Schlosser, C. Adam; Suarez, Max J.

1999-01-01

126

A diversity of localized timescales in network activity  

PubMed Central

Neurons show diverse timescales, so that different parts of a network respond with disparate temporal dynamics. Such diversity is observed both when comparing timescales across brain areas and among cells within local populations; the underlying circuit mechanism remains unknown. We examine conditions under which spatially local connectivity can produce such diverse temporal behavior. In a linear network, timescales are segregated if the eigenvectors of the connectivity matrix are localized to different parts of the network. We develop a framework to predict the shapes of localized eigenvectors. Notably, local connectivity alone is insufficient for separate timescales. However, localization of timescales can be realized by heterogeneity in the connectivity profile, and we demonstrate two classes of network architecture that allow such localization. Our results suggest a framework to relate structural heterogeneity to functional diversity and, beyond neural dynamics, are generally applicable to the relationship between structure and dynamics in biological networks. DOI: http://dx.doi.org/10.7554/eLife.01239.001 PMID:24448407

Chaudhuri, Rishidev; Bernacchia, Alberto; Wang, Xiao-Jing

2014-01-01

127

Reliability of African climate prediction and attribution across timescales  

NASA Astrophysics Data System (ADS)

This study investigates the reliability of seasonal to multi-decadal climate simulations of the wet seasons of several key African regions. It is found that reliability varies across regions and seasons, and that simulations of precipitation are universally less reliable than simulations of temperature. Similar levels of reliability are found across all the timescales considered for most (but not all) region/season combinations. Reliability for temperatures increases on longer timescales, both due to the differences in the modelling systems for each timescale and, in part, due to the contribution from systematic climate warming. Though the use of reliability is well-established for forecasting, its meaning for attribution is less clear, and further work is underway to further clarify this.

Lott, Fraser C.; Gordon, Margaret; Graham, Richard J.; Scaife, Adam A.; Vellinga, Michael

2014-10-01

128

Optical Depths and Timescale Distributions in Galactic Microlensing  

E-print Network

We present microlensing calculations for a Galactic model based on Han & Gould (2003), which is empirically normalised by star counts. We find good agreement between this model and data recently published by the MACHO and OGLE collaborations for the optical depth in various Galactic fields, and the trends thereof with Galactic longitude l and latitude b. We produce maps of optical depth and, by adopting simple kinematic models, of average event timescales for microlensing towards the Galactic bulge. We also find that our model predictions are in reasonable agreement with the OGLE data for the expected timescale distribution. We show that the fractions of events with very long and short timescales due to a lens of mass M are weighted by M^2 n(M)dM and M^(-1) n(M)dM respectively, independent of the density and kinematics of the lenses.

Alexander Wood; Shude Mao

2005-07-08

129

Diffusion Time-Scale of Porous Pressure-Sensitive Paint  

NASA Technical Reports Server (NTRS)

Pressure-sensitive paint (PSP) is an optical pressure sensor that utilizes the oxygen quenching of luminescence. PSP measurements in unsteady aerodynamic flows require fast time response of the paint. There are two characteristic time-scales that are related to the time response of PSP. One is the luminescent lifetime representing an intrinsic physical limit for the achievable temporal resolution of PSP. Another is the time-scale of oxygen diffusion across the PSP layer. When the time-scale of oxygen diffusion is much larger than the luminescent lifetime, the time response of PSP is controlled by oxygen diffusion. In a thin homogenous polymer layer where diffusion is Fickian, the oxygen concentration 1021 can be described by the diffusion equation in one-dimension.

Liu, Tianshu; Teduka, Norikazu; Kameda, Masaharu; Asai, Keisuke

2001-01-01

130

BINARY ASTEROID ENCOUNTERS WITH TERRESTRIAL PLANETS: TIMESCALES AND EFFECTS  

SciTech Connect

Many asteroids that make close encounters with terrestrial planets are in a binary configuration. Here, we calculate the relevant encounter timescales and investigate the effects of encounters on a binary's mutual orbit. We use a combination of analytical and numerical approaches with a wide range of initial conditions. Our test cases include generic binaries with close, moderate, and wide separations, as well as seven well-characterized near-Earth binaries. We find that close approaches (<10 Earth radii) occur for almost all binaries on 1-10 million year timescales. At such distances, our results suggest substantial modifications to a binary's semimajor axis, eccentricity, and inclination, which we quantify. Encounters within 30 Earth radii typically occur on sub-million year timescales and significantly affect the wider binaries. Important processes in the lives of near-Earth binaries, such as tidal and radiative evolution, can be altered or stopped by planetary encounters.

Fang, Julia; Margot, Jean-Luc [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

2012-01-15

131

Einstein's Real "biggest Blunder"  

NASA Astrophysics Data System (ADS)

Albert Einstein's real "biggest blunder" was not the 1917 introduction into his gravitational field equations of a cosmological constant term ?, rather was his failure in 1916 to distinguish between the entirely different concepts of active gravitational mass and passive gravitational mass. Had he made the distinction, and followed David Hilbert's lead in deriving field equations from a variational principle, he might have discovered a true (not a cut and paste) Einstein-Rosen bridge and a cosmological model that would have allowed him to predict, long before such phenomena were imagined by others, inflation, a big bounce (not a big bang), an accelerating expansion of the universe, dark matter, and the existence of cosmic voids, walls, filaments and nodes.

Ellis, Homer G.

2012-10-01

132

From Antiquity to Einstein  

NSDL National Science Digital Library

These online notes outline the history of Western thought on cosmology and the structure of space and time. Included is an introduction to the scientific method and large numbers, astronomy, Newton's laws, and the aspects of electricity and magnetism and optics that lead to 20th century physics. The final sections cover special and general relativity, and their impact on astronomy and cosmology. Important contributions by the Babylonians, the Egyptians, the Greeks, Ptomely, Copernicus, Kepler, Galileo, Newton, and Einstein are included..

Wudka, Jose

2004-08-11

133

Relativistic fireballs - Energy conversion and time-scales  

NASA Technical Reports Server (NTRS)

The expansion energy of a relativistic fireball can be reconverted into radiation when it interacts with an external medium. For expansion with Lorentz factors greater than or approximately equal to 1000 into a typical galactic environment, the corresponding time-scale in the frame of the observer is of the order of seconds. This mechanism would operate in any cosmological scenario of gamma-ray bursts involving initial energies of order a percent of a stellar rest mass, and implies photon energies and time-scales compatible with those observed in gamma-ray bursts.

Rees, M. J.; Meszaros, P.

1992-01-01

134

Albert Einstein: Rebellious Wunderkind  

E-print Network

Childhood and Schooldays: Albert Einstein, and the family members seemed to have exaggerated the story of Albert who developed slowly, learned to talk late, and whose parents thought he was abnormal. These and other stories were adopted by biographers as if they really happened in the form that Albert and his sister told them. Hence biographers were inspired by them to create a mythical public image of Albert Einstein. Albert had tendency toward temper tantrums, the young impudent rebel Einstein had an impulsive and upright nature. He rebelled against authority and refused to learn by rote. He could not easily bring himself to study what did not interest him at school, especially humanistic subjects. And so his sister told the story that his Greek professor, to whom he once submitted an especially poor paper, went so far in his anger to declare that nothing would ever become of him. Albert learned subjects in advance when it came to sciences; and during the vacation of a few months from school, Albert indepen...

Weinstein, Galina

2012-01-01

135

The stolen brain of Einstein  

NASA Astrophysics Data System (ADS)

Pathologist Thomas Stoltz Harvey performed an autopsy on Einstein after his death in 1955. During the autopsy Harvey removed Einstein's brain, took pictures of it and then cut it into several pieces. A lot of scientific attention has been devoted to Einstein' brain, and it still comes up once in a while. We've all heard something or other about Einstein's brain, as it has become somewhat of a folk lore. What is less known is that Harvey in actuality did not have the permission to remove the brain. Only later Harvey convinced Einstein's Hans Albert Einstein son that this was for a good purpose. The brain would only be used for scientific purpose, which will be published reputable journals. I will try to describe in some detail the long journey this brain has taken in last fifty two years.

Modi, Kavan

2008-03-01

136

THE CAMPAIGN TO TRANSFORM EINSTEIN 2 THE CAMPAIGN TO TRANSFORM EINSTEIN  

E-print Network

THE CAMPAIGN TO TRANSFORM EINSTEIN #12;2 THE CAMPAIGN TO TRANSFORM EINSTEIN #12;ALBERT EINSTEIN COLLEGE OF MEDICINE 1 F or more than five decades, Albert Einstein College of Medicine has responded: Albert Einstein grants his name to the Albert Einstein College of Medicine 1970s: Establishment

Yates, Andrew

137

Brief Communications Timescale-Invariant Representation of Acoustic  

E-print Network

. Such a timescale-invariant recognition is essential under natural conditions, because grasshoppers do; temporal pattern; spike train; burst code; invariant object recognition Introduction Object recognition´ry et al., 1993; Ito et al., 1995; Rolls, 2000), the strength of an odor (Stopfer et al., 2003

Benda, Jan

138

Molecular timescales and the fossil record: a paleontological perspective  

Microsoft Academic Search

The fossil record serves a crucial function as an external calibration for genomic clocks and molecular evolutionary timescales. Although certain portions of the vertebrate fossil record are accurate, there is always uncertainty in establishing a divergence time because the fossils can only provide evidence of the first appearance of the descendants of a split, and by definition they underestimate the

Robert R. Reisz; Johannes Müller

2004-01-01

139

Multiple time-scale power system dynamic simulation  

Microsoft Academic Search

A new program, EXSTAB (extended time-scale stability) has been developed for representing a wide variety of power system performance problems, from transient stability through long-term dynamics and voltage instability. The capability of the program includes multiple execution modes and automatic step size selection to address conflicting goals of accuracy and efficiency. The modeling includes a broad range of apparatus to

A. Kurita; H. Okubo; K. Oki; S. Agematsu; D. B. Klapper; N. W. Miller; J. J. Sanchez-Gasca; K. A. Wirgau; T. D. Younkins

1993-01-01

140

On the pathways and timescales of intercontinental air pollution transport  

Microsoft Academic Search

This paper presents results of a 1-year simulation of the transport of six passive tracers, released over the continents according to an emission inventory for carbon monoxide (CO). Lagrangian concepts are introduced to derive age spectra of the tracer concentrations on a global grid in order to determine the timescales and pathways of pollution export from the continents. Calculating these

Andreas Stohl; Sabine Eckhardt; Caroline Forster; Paul James; Nicole Spichtinger

2002-01-01

141

Antarctic temperature at orbital timescales controlled by local summer duration  

Microsoft Academic Search

During the late Pleistocene epoch, proxies for Southern Hemisphere climate from the Antarctic ice cores vary nearly in phase with Northern Hemisphere insolation intensity at the precession and obliquity timescales. This coherence has led to the suggestion that Northern Hemisphere insolation controls Antarctic climate. However, it is unclear what physical mechanisms would tie southern climate to northern insolation. Here we

Peter Huybers; George Denton

2008-01-01

142

Comprehensive Scenarios of Millennial Timescale Carbon Cycle and Climate  

E-print Network

by prior beliefs and climate observations Data assimilated World Ocean Atlas temperature and salinity NCEP uncertainty in ocean circulation and spatial surface climate pattern but not climate sensitivity or carbonComprehensive Scenarios of Millennial Timescale Carbon Cycle and Climate Change in a new Earth

Williamson, Mark

143

Distinct Neural Mechanisms Mediate Olfactory Memory Formation at Different Timescales  

ERIC Educational Resources Information Center

Habituation is one of the oldest forms of learning, broadly expressed across sensory systems and taxa. Here, we demonstrate that olfactory habituation induced at different timescales (comprising different odor exposure and intertrial interval durations) is mediated by different neural mechanisms. First, the persistence of habituation memory is…

McNamara, Ann Marie; Magidson, Phillip D.; Linster, Christiane; Wilson, Donald A.; Cleland, Thomas A.

2008-01-01

144

Stochastic Simulation of Enzyme-Catalyzed Reactions with Disparate Timescales  

E-print Network

Stochastic Simulation of Enzyme-Catalyzed Reactions with Disparate Timescales Debashis Barik-steady-state approximation'' for enzyme-catalyzed reactions provides a useful framework for efficient and accurate stochastic simulations. The method is applied to three examples: a simple enzyme-catalyzed reaction where enzyme

Paul, Mark

145

The Short-Timescale Behavior of Glacial Ice  

E-print Network

The Short-Timescale Behavior of Glacial Ice Thesis by Jeffrey Muir Thompson In Partial Fulfillment #12;iii This thesis is dedicated to William (Bill) Bing and Dr. Jennifer Howes. Without their unending thesis advisory committee, and for encouraging me to get a minor in civil engineering. I've learned a lot

Winfree, Erik

146

Geol 102 Historical Geology The Geologic Timescale 2012  

E-print Network

.0 Triassic 252.2 - 201.3 Permian 298.9 - 252.2 Pennsylvanian Sub-period 323.2 - 298.9 Mississippian Sub-periodGeol 102 Historical Geology The Geologic Timescale 2012 EON ERA PERIOD (Special Units) EPOCH Range

Holtz Jr., Thomas R.

147

The time-scale of escape from star clusters  

Microsoft Academic Search

In this paper a cluster is modelled as a smooth potential (due to the cluster stars) plus the steady tidal field of the Galaxy. In this model there is a minimum energy below which stars cannot escape. Above this energy, however, the time-scale on which a star escapes varies with the orbital parameters of the star (mainly its energy) in

T. Fukushige; D. C. Heggie

2000-01-01

148

Dynamical masses, time-scales, and evolution of star clusters  

E-print Network

This review discusses (i) dynamical methods for determining the masses of Galactic and extragalactic star clusters, (ii) dynamical processes and their time-scales for the evolution of clusters, including evaporation, mass segregation, core collapse, tidal shocks, dynamical friction and merging. These processes lead to significant evolution of globular cluster systems after their formation.

Ortwin Gerhard

2000-07-18

149

Why Mountains? Tales & Timescales of their Birth & Death  

E-print Network

Why Mountains? Tales & Timescales of their Birth & Death Saturday, September 12, 2009: 2146 Snee:40-10:00 Chris Andronicos (Cornell) The Birth, Life, and Death of North America's Largest Batholith: The Coast as the Hills: A Thermochronological View of the Birth and Death of Mountains 2:40-3:00 Frank Pazzaglia (Lehigh

Pritchard, Matthew

150

Einstein Toolkit for Relativistic Astrophysics  

NASA Astrophysics Data System (ADS)

The Einstein Toolkit is a collection of software components and tools for simulating and analyzing general relativistic astrophysical systems. Such systems include gravitational wave space-times, collisions of compact objects such as black holes or neutron stars, accretion onto compact objects, core collapse supernovae and Gamma-Ray Bursts. The Einstein Toolkit builds on numerous software efforts in the numerical relativity community including CactusEinstein, Whisky, and Carpet. The Einstein Toolkit currently uses the Cactus Framework as the underlying computational infrastructure that provides large-scale parallelization, general computational components, and a model for collaborative, portable code development.

Collaborative Effort

2011-02-01

151

Scalar Perturbation Produced at the Pre-inflationary Stage in Eddington-inspired Born-Infeld Gravity  

E-print Network

We investigate the scalar perturbation produced at the pre-inflationary stage driven by a massive scalar field in Eddington-inspired Born-Infeld gravity. The scalar power spectrum exhibits a peculiar rise for low $k$-modes. The tensor-to-scalar ratio can be significantly lowered compared with that in the standard chaotic inflation model in general relativity. This result is very affirmative considering the recent dispute on the detection of the gravitational wave radiation between PLANCK and BICEP2.

Cho, Inyong

2014-01-01

152

Super-Eddington Accretion in the Ultraluminous X-Ray Source NGC 1313 X-2: An Ephemeral Feast  

NASA Astrophysics Data System (ADS)

We investigate the X-ray spectrum, variability, and the surrounding ionized bubble of NGC 1313 X-2 to explore the physics of super-Eddington accretion. Beyond the Eddington luminosity, the accretion disk of NGC 1313 X-2 is truncated at a large radius (~50 times the innermost stable circular orbit), and displays the similar evolution track with both luminous Galactic black-hole and neutron star X-ray binaries (XRBs). In super-critical accretion, the speed of radiatively driven outflows from the inner disk is mildly relativistic. Such ultra-fast outflows would be overionized and might produce weak Fe K absorption lines, which may be detected by the coming X-ray mission Astro-H. If NGC 1313 X-2 is a massive stellar XRB, the high luminosity indicates that an ephemeral feast is held in the source. That is, the source must be accreting at a hyper-Eddington mass rate to give the super-Eddington emission over ~104-105 yr. The expansion of the surrounding bubble nebula with a velocity of ~100 km s-1 might indicate that it has existed over ~106 yr and is inflated by the radiatively driven outflows from the transient with a duty cycle of activity of ~ a few percent. Alternatively, if the surrounding bubble nebula is produced by line-driven winds, less energy is required than the radiatively driven outflow scenario, and the radius of the Strömgren radius agrees with the nebula size. Our results are in favor of the line-driven winds scenario, which can avoid the conflict between the short accretion age and the apparently much longer bubble age inferred from the expansion velocity in the nebula.

Weng, Shan-Shan; Zhang, Shuang-Nan; Zhao, Hai-Hui

2014-01-01

153

Integral equations of the photon fluence rate and flux based on a generalized Delta-Eddington phase function  

PubMed Central

We present a generalized Delta-Eddington phase function to simplify the radiative transfer equation to integral equations with respect to both photon fluence rate and flux vector. The photon fluence rate and flux can be solved from the system of integral equations. By comparing to the Monte Carlo simulation results, the solutions of the system of integral equations accurately model the photon propagation in biological tissue over a wide range of optical parameters. PMID:18465979

Cong, Wenxiang; Shen, Haiou; Cong, Alexander X.; Wang, Ge

2009-01-01

154

Properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity  

NASA Astrophysics Data System (ADS)

We systematically examine the properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity with not only the positive but also the negative coupling constant in the theory. As a result, we numerically find that the black hole solution exists even with the negative coupling constant, where the electric charge of black hole can be larger than the black hole mass. We also clarify the parameter space where the black hole solution exists. On the other hand, to examine the particle motion around such black hole, we derive the geodesic equation. The behavior of the effective potential for the radial particle motion is almost the same as that in general relativity, but the radius of the innermost stable circular orbit and the angular momentum giving the innermost stable circular orbit can be changed, depending on the coupling constant. In particular, we find that the radius of innermost stable circular orbit with the specific value of the coupling constant can be smaller than that for the extreme case in general relativity. Such a particle can release the gravitational binding energy more than the prediction in general relativity, which could be important from the observational point of view.

Sotani, Hajime; Miyamoto, Umpei

2014-12-01

155

Structure of neutron, quark, and exotic stars in Eddington-inspired Born-Infeld gravity  

NASA Astrophysics Data System (ADS)

We consider the structure and physical properties of specific classes of neutron, quark, and “exotic” stars in Eddington-inspired Born-Infeld (EiBI) gravity. The latter reduces to standard general relativity in vacuum, but presents a different behavior of the gravitational field in the presence of matter. The equilibrium equations for a spherically symmetric configuration (mass continuity and Tolman-Oppenheimer-Volkoff) are derived, and their solutions are obtained numerically for different equations of state of neutron and quark matter. More specifically, stellar models, described by the stiff fluid, radiationlike, polytropic and the bag model quark equations of state are explicitly constructed in both general relativity and EiBI gravity, thus allowing a comparison between the predictions of these two gravitational models. As a general result it turns out that for all the considered equations of state, EiBI gravity stars are more massive than their general relativistic counterparts. Furthermore, an exact solution of the spherically symmetric field equations in EiBI gravity, describing an exotic star, with decreasing pressure but increasing energy density, is also obtained. As a possible astrophysical application of the obtained results we suggest that stellar mass black holes, with masses in the range of 3.8M? and 6M?, respectively, could be in fact EiBI neutron or quark stars.

Harko, Tiberiu; Lobo, Francisco S. N.; Mak, M. K.; Sushkov, Sergey V.

2013-08-01

156

Black hole solution and strong gravitational lensing in Eddington-inspired Born-Infeld gravity  

E-print Network

A new theory of gravity called Eddington-inspired Born-Infeld (EiBI) gravity was recently proposed by Ba\\~{n}ados and Ferreira. This theory leads to some exciting new features, such as free of cosmological singularities. In this paper, we first obtain a charged EiBI black hole solution with a nonvanishing cosmological constant when the electromagnetic field is included in. Then based on it, we study the strong gravitational lensing by the asymptotic flat charged EiBI black hole. The strong deflection limit coefficients and observables are shown to closely depend on the additional coupling parameter $\\kappa$ in the EiBI gravity. It is found that, compared with the corresponding charged black hole in general relativity, the positive coupling parameter $\\kappa$ will shrink the black hole horizon and photon sphere. Moreover, the coupling parameter will decrease the angular position and relative magnitudes of the relativistic images, while increase the angular separation, which may shine new light on testing such gravity theory in near future by the astronomical instruments.

Shao-Wen Wei; Ke Yang; Yu-Xiao Liu

2014-05-09

157

Super-Eddington accreting massive black holes as long-lived cosmological standards.  

PubMed

Super-Eddington accreting massive black holes (SEAMBHs) reach saturated luminosities above a certain accretion rate due to photon trapping and advection in slim accretion disks. We show that these SEAMBHs could provide a new tool for estimating cosmological distances if they are properly identified by hard x-ray observations, in particular by the slope of their 2-10 keV continuum. To verify this idea we obtained black hole mass estimates and x-ray data for a sample of 60 narrow line Seyfert 1 galaxies that we consider to be the most promising SEAMBH candidates. We demonstrate that the distances derived by the new method for the objects in the sample get closer to the standard luminosity distances as the hard x-ray continuum gets steeper. The results allow us to analyze the requirements for using the method in future samples of active black holes and to demonstrate that the expected uncertainty, given large enough samples, can make them into a useful, new cosmological ruler. PMID:23473126

Wang, Jian-Min; Du, Pu; Valls-Gabaud, David; Hu, Chen; Netzer, Hagai

2013-02-22

158

Dark matter density profile and galactic metric in Eddington-inspired Born-Infeld gravity  

E-print Network

We consider the density profile of pressureless dark matter in Eddington-inspired Born-Infeld (EiBI) gravity. The gravitational field equations are investigated for a spherically symmetric dark matter galactic halo, by adopting a phenomenological tangential velocity profile for test particles moving in stable circular orbits around the galactic center. The density profile and the mass distribution, as well as the general form of the metric tensor is obtained by numerically integrating the gravitational field equations, and in an approximate analytical form by using the Newtonian limit of the theory. In the weak field limit the dark matter density distribution is described by the Lane-Emden equation with polytropic index $n=1$, and is non-singular at the galactic center. The parameter $\\kappa $ of the theory is determined so that that the theory could provide a realistic description of the dark matter halos. The gravitational properties of the dark matter halos are also briefly discussed in the Newtonian approximation.

Tiberiu Harko; Francisco S. N. Lobo; M. K. Mak; Sergey V. Sushkov

2014-02-18

159

The global monsoon across timescales: coherent variability of regional monsoons  

NASA Astrophysics Data System (ADS)

Monsoon has earned increasing attention from the climate community since the last century, yet only recently have regional monsoons been recognized as a global system. It remains a debated issue, however, as to what extent and at which timescales the global monsoon can be viewed as a major mode of climate variability. For this purpose, a PAGES (Past Global Changes) working group (WG) was set up to investigate the concept of the global monsoon and its future research directions. The WG's synthesis is presented here. On the basis of observation and proxy data, the WG found that the regional monsoons can vary coherently, although not perfectly, at various timescales, varying between interannual, interdecadal, centennial, millennial, orbital and tectonic timescales, conforming to the global monsoon concept across timescales. Within the global monsoon system, each subsystem has its own features, depending on its geographic and topographic conditions. Discrimination between global and regional components in the monsoon system is a key to revealing the driving factors in monsoon variations; hence, the global monsoon concept helps to enhance our understanding and to improve future projections of the regional monsoons. This paper starts with a historical review of the global monsoon concept in both modern and paleo-climatology, and an assessment of monsoon proxies used in regional and global scales. The main body of the paper is devoted to a summary of observation data at various timescales, providing evidence of the coherent global monsoon system. The paper concludes with a projection of future monsoon shifts in a warming world. The synthesis will be followed by a companion paper addressing driving mechanisms and outstanding issues in global monsoon studies.

Wang, P. X.; Wang, B.; Cheng, H.; Fasullo, J.; Guo, Z. T.; Kiefer, T.; Liu, Z. Y.

2014-11-01

160

THE DEMOGRAPHICS OF BROAD-LINE QUASARS IN THE MASS-LUMINOSITY PLANE. II. BLACK HOLE MASS AND EDDINGTON RATIO FUNCTIONS  

SciTech Connect

We employ a flexible Bayesian technique to estimate the black hole (BH) mass and Eddington ratio functions for Type 1 (i.e., broad line) quasars from a uniformly selected data set of {approx}58, 000 quasars from the Sloan Digital Sky Survey (SDSS) DR7. We find that the SDSS becomes significantly incomplete at M {sub BH} {approx}< 3 Multiplication-Sign 10{sup 8} M {sub Sun} or L/L {sub Edd} {approx}< 0.07, and that the number densities of Type 1 quasars continue to increase down to these limits. Both the mass and Eddington ratio functions show evidence of downsizing, with the most massive and highest Eddington ratio BHs experiencing Type 1 quasar phases first, although the Eddington ratio number densities are flat at z < 2. We estimate the maximum Eddington ratio of Type 1 quasars in the observable universe to be L/L {sub Edd} {approx} 3. Consistent with our results in Shen and Kelly, we do not find statistical evidence for a so-called sub-Eddington boundary in the mass-luminosity plane of broad-line quasars, and demonstrate that such an apparent boundary in the observed distribution can be caused by selection effect and errors in virial BH mass estimates. Based on the typical Eddington ratio in a given mass bin, we estimate growth times for the BHs in Type 1 quasars and find that they are comparable to or longer than the age of the universe, implying an earlier phase of accelerated (i.e., with higher Eddington ratios) and possibly obscured growth. The large masses probed by our sample imply that most of our BHs reside in what are locally early-type galaxies, and we interpret our results within the context of models of self-regulated BH growth.

Kelly, Brandon C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93107 (United States)] [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93107 (United States); Shen, Yue [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States)

2013-02-10

161

Einstein and His Times  

NSDL National Science Digital Library

In this lesson, students will read about and research the major historical events that occurred throughout the year 1919. They will use different readings and articles to understand and describe what life was like during this time. In addition, the students will present their case as to whether or not Albert Einstein should be voted "Man of the Year" for 1919. This activity is from the Cosmic Times teachers guide and is intended to be used in conjunction with the 1919 Cosmic Times Poster.

162

Einstein spectra of quasars  

NASA Technical Reports Server (NTRS)

The results of the initial stage of the CfA survey of quasar energy distributions are reviewed. Einstein imaging proportional counter spectra of 33 quasars have been studied by fitting a single power law slope and absorption by an equivalent column density of neutral hydrogen. Comparison with the higher energy HEAO-A2 data leads to a two-component model for the X-ray spectrum. The X-ray column density is systematically lower than the 21-cm measured Galactic column density along the same line of sight.

Wilkes, Belinda J.

1988-01-01

163

OWL representation of the geologic timescale implementing stratigraphic best practice  

NASA Astrophysics Data System (ADS)

The geologic timescale is a cornerstone of the earth sciences. Versions are available from many sources, with the following being of particular interest: (i) The official International Stratigraphic Chart (ISC) is maintained by the International Commission for Stratigraphy (ICS), following principles developed over the last 40 years. ICS provides the data underlying the chart as part of a specialized software package, and the chart itself as a PDF using the standard colours; (ii) ITC Enschede has developed a representation of the timescale as a thesaurus in SKOS, used in a Web Map Service delivery system; (iii) JPL's SWEET ontology includes a geologic timescale. This takes full advantage of the capabilities of OWL. However, each of these has limitations - The ISC falls down because of incompatibility with web technologies; - While SKOS supports multilingual labelling, SKOS does not adequately support timescale semantics, in particular since it does not include ordering relationships; - The SWEET version (as of version 2) is not fully aligned to the model used by ICS, in particular not recognizing the role of the Global Boundary Stratotype Sections and Point (GSSP). Furthermore, it is distributed as static documents, rather than through a dynamic API using SPARQL. The representation presented in this paper overcomes all of these limitations as follows: - the timescale model is formulated as an OWL ontology - the ontology is directly derived from the UML representation of the ICS best practice proposed by Cox & Richard [2005], and subsequently included as the Geologic Timescale package in GeoSciML (http://www.geosciml.org); this includes links to GSSPs as per the ICS process - key properties in the ontology are also asserted to be subProperties of SKOS properties (topConcept and broader/narrower relations) in order to support SKOS-based queries; SKOS labelling is used to support multi-lingual naming and synonyms - the International Stratigraphic Chart is implemented as a set of instances of classes from the ontology, and published through a SPARQL end-point - the elements of the Stratigraphic chart are linked to the corresponding elements in SWEET (Raskin et al., 2011) and DBpedia to support traceability between different commonly accessed representations. The ontology builds on standard geospatial information models, including the Observations and Measurements model (ISO 19156), and GeoSciML. This allows the ages given in the chart to be linked to the evidence basis found in the associated GeoSciML features.

Cox, S. J.

2011-12-01

164

Einstein and the "Crucial" Experiment  

ERIC Educational Resources Information Center

Examines the widespread view that it was the crucial Michelson-Morley experiment that led Einstein to formulate the special relativity theory. From Einstein's writings, evidence is presented that no such direct genetic connection exists. The author suggests that the historian of science must resist the experimenticist's fallacy of imposing a…

Holton, Gerald

1969-01-01

165

Albert Einstein 1879-1955.  

ERIC Educational Resources Information Center

Celebrates the centennial of Einstein's birth with an eight-page pictorial biography and two special articles: (1) Einstein the catalyst; and (2) Unitary field theories. His special and general theories of relativity and his contributions to quantum physics and other topics are also presented. (HM)

Physics Today, 1979

1979-01-01

166

Einstein Inflationary Probe (EIP)  

NASA Technical Reports Server (NTRS)

I will discuss plans to develop a concept for the Einstein Inflation Probe: a mission to detect gravity waves from inflation via the unique signature they impart to the cosmic microwave background (CMB) polarization. A sensitive CMB polarization satellite may be the only way to probe physics at the grand-unified theory (GUT) scale, exceeding by 12 orders of magnitude the energies studied at the Large Hadron Collider. A detection of gravity waves would represent a remarkable confirmation of the inflationary paradigm and set the energy scale at which inflation occurred when the universe was a fraction of a second old. Even a strong upper limit to the gravity wave amplitude would be significant, ruling out many common models of inflation, and pointing to inflation occurring at much lower energy, if at all. Measuring gravity waves via the CMB polarization will be challenging. We will undertake a comprehensive study to identify the critical scientific requirements for the mission and their derived instrumental performance requirements. At the core of the study will be an assessment of what is scientifically and experimentally optimal within the scope and purpose of the Einstein Inflation Probe.

Hinshaw, Gary

2004-01-01

167

STP Entropy Einstein Solid Program  

NSDL National Science Digital Library

The STP Entropy Einstein Solid program calculates the entropy of two Einstein solids that can exchange energy. The purpose of this calculation is to illustrate that the entropy is a maximum at thermal equilibrium. The default system is two Einstein solids with 50 particles each and total energy E =200. STP EntropyEinsteinSolid is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp_EntropyEinsteinSolid.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2009-03-13

168

Particle-acceleration timescales in TeV blazar flares  

E-print Network

Observations of minute-scale flares in TeV Blazars place constraints on particle acceleration mechanisms in those objects. The implications for a variety of radiation mechanisms have been addressed in the literature; in this paper we compare four different acceleration mechanisms: diffusive shock acceleration, second-order Fermi, shear acceleration and the converter mechanism. When the acceleration timescales and radiative losses are taken into account, we can exclude shear acceleration and the neutron-based converted mechanism as possible acceleration processes in these systems. The first-order Fermi process and the converter mechanism working via SSC photons are still practically instantaneous, however, provided sufficient turbulence is generated on the timescale of seconds. We propose stochastic acceleration as a promising candidate for the energy-dependent time delays in recent gamma-ray flares of Markarian 501.

Joni Tammi; Peter Duffy

2008-12-01

169

Characteristic microvessel relaxation timescales associated with ultrasound-activated microbubbles  

PubMed Central

Ultrasound-activated microbubbles were used as actuators to deform microvessels for quantifying microvessel relaxation timescales at megahertz frequencies. Venules containing ultrasound contrast microbubbles were insonified by short 1?MHz ultrasound pulses. Vessel wall forced-deformations were on the same microsecond timescale as microbubble oscillations. The subsequent relaxation of the vessel was recorded by high-speed photomicrography. The tissue was modeled as a simple Voigt solid. Relaxation time constants were measured to be on the order of ?10??s. The correlation coefficients between the model and 38 data sets were never lower than 0.85, suggesting this model is sufficient for modeling tissue relaxation at these frequencies. The results place a bound on potential numerical values for viscosity and elasticity of venules. PMID:23152641

Chen, Hong; Brayman, Andrew A.; Matula, Thomas J.

2012-01-01

170

Insect olfactory coding and memory at multiple timescales  

PubMed Central

Insects can learn, allowing them great flexibility for locating seasonal food sources and avoiding wily predators. Because insects are relatively simple and accessible to manipulation, they provide good experimental preparations for exploring mechanisms underlying sensory coding and memory. Here we review how the intertwining of memory with computation enables the coding, decoding, and storage of sensory experience at various stages of the insect olfactory system. Individual parts of this system are capable of multiplexing memories at different timescales, and conversely, memory on a given timescale can be distributed across different parts of the circuit. Our sampling of the olfactory system emphasizes the diversity of memories, and the importance of understanding these memories in the context of computations performed by different parts of a sensory system. PMID:21632235

Gupta, Nitin; Stopfer, Mark

2011-01-01

171

Comparison of inversion codes for polarized line formation in MHD simulations. I. Milne-Eddington codes  

NASA Astrophysics Data System (ADS)

Milne-Eddington (M-E) inversion codes for the radiative transfer equation are the most widely used tools to infer the magnetic field from observations of the polarization signals in photospheric and chromospheric spectral lines. Unfortunately, a comprehensive comparison between the different M-E codes available to the solar physics community is still missing, and so is a physical interpretation of their inferences. In this contribution we offer a comparison between three of those codes (VFISV, ASP/HAO, and HeLIx+). These codes are used to invert synthetic Stokes profiles that were previously obtained from realistic non-grey three-dimensional magnetohydrodynamical (3D MHD) simulations. The results of the inversion are compared with each other and with those from the MHD simulations. In the first case, the M-E codes retrieve values for the magnetic field strength, inclination and line-of-sight velocity that agree with each other within ?B ? 35 (Gauss), ?? ? 1.2°, and ?v ? 10 m s-1, respectively. Additionally, M-E inversion codes agree with the numerical simulations, when compared at a fixed optical depth, within ?B ? 130 (Gauss), ?? ? 5°, and ?v ? 320 m s-1. Finally, we show that employing generalized response functions to determine the height at which M-E codes measure physical parameters is more meaningful than comparing at a fixed geometrical height or optical depth. In this case the differences between M-E inferences and the 3D MHD simulations decrease to ?B ? 90 (Gauss), ?? ? 3°, and ?v ? 90 m s-1.

Borrero, J. M.; Lites, B. W.; Lagg, A.; Rezaei, R.; Rempel, M.

2014-12-01

172

EDDINGTON-LIMITED ACCRETION AND THE BLACK HOLE MASS FUNCTION AT REDSHIFT 6  

SciTech Connect

We present discovery observations of a quasar in the Canada-France High-z Quasar Survey (CFHQS) at redshift z = 6.44. We also use near-infrared spectroscopy of nine CFHQS quasars at z {approx} 6 to determine black hole masses. These are compared with similar estimates for more luminous Sloan Digital Sky Survey quasars to investigate the relationship between black hole mass and quasar luminosity. We find a strong correlation between Mg II FWHM and UV luminosity and that most quasars at this early epoch are accreting close to the Eddington limit. Thus, these quasars appear to be in an early stage of their life cycle where they are building up their black hole mass exponentially. Combining these results with the quasar luminosity function, we derive the black hole mass function at z = 6. Our black hole mass function is {approx}10{sup 4} times lower than at z = 0 and substantially below estimates from previous studies. The main uncertainties which could increase the black hole mass function are a larger population of obscured quasars at high redshift than is observed at low redshift and/or a low quasar duty cycle at z = 6. In comparison, the global stellar mass function is only {approx}10{sup 2} times lower at z = 6 than at z = 0. The difference between the black hole and stellar mass function evolution is due to either rapid early star formation which is not limited by radiation pressure as is the case for black hole growth or inefficient black hole seeding. Our work predicts that the black hole mass-stellar mass relation for a volume-limited sample of galaxies declines rapidly at very high redshift. This is in contrast to the observed increase at 4 < z < 6 from the local relation if one just studies the most massive black holes.

Willott, Chris J.; Crampton, David; Hutchings, John B.; Schade, David [Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Albert, Loic [Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Highway, Kamuela, HI 96743 (United States); Arzoumanian, Doris [CEA-Saclay, IRFU, SAp, 91191 Gif-sur-Yvette (France); Bergeron, Jacqueline; Omont, Alain [Institut d'Astrophysique de Paris, CNRS and Universite Pierre et Marie Curie, 98bis Boulevard Arago, F-75014 Paris (France); Delorme, Philippe [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom); Reyle, Celine, E-mail: chris.willott@nrc.c [Institut Utinam, Observatoire de Besancon, Universite de Franche-Comte, BP1615, 25010 Besancon Cedex (France)

2010-08-15

173

Timescale algorithms combining cesium clocks and hydrogen masers  

NASA Technical Reports Server (NTRS)

The United States Naval Observatory (USNO) atomic timescale, formerly based on an ensemble of cesium clocks, is now produced by an ensemble of cesium clocks and hydrogen masers. In order to optimize stability and reliability, equal clock weighting has been replaced by a procedure reflecting the relative, time-varying noise characteristics of the two different types of clocks. Correlation of frequency drift is required, and residual drift is avoided by the eventual complete deweighting of the masers.

Breakiron, Lee A.

1992-01-01

174

The Timescale and Mode of Star Formation in Clusters  

E-print Network

I discuss two questions about the origin of star clusters: How long does the process take? What is the mode of individual star formation? I argue that observations of Galactic star-forming regions, particularly the Orion Nebula Cluster (ONC), indicate that cluster formation often takes several Myr, which is many local dynamical timescales. Individual stars and binaries, including massive stars, appear to form from the collapse of gas cores.

Jonathan C. Tan

2004-10-05

175

Geol 102 Historical Geology The Geologic Timescale 2011  

E-print Network

Geol 102 Historical Geology The Geologic Timescale 2011 EON ERA PERIOD (Special Units) EPOCH Range 65.5 - 55.8 Mesozoic Cretaceous 145.5 - 65.5 Jurassic 201.5 - 145.5 Triassic 252.3 - 201.5 Paleozoic Permian 299.0 - 252.3 Carboniferous Pennsylvanian Sub-period 318.1 - 299.0 Mississippian Sub-period 359

Holtz Jr., Thomas R.

176

Geol 102 Historical Geology The Geologic Timescale 2009  

E-print Network

Geol 102 Historical Geology The Geologic Timescale 2009 EON ERA PERIOD (Special Units) EPOCH Range.5 - 55.8 Mesozoic Cretaceous 145.5 - 65.5 Jurassic 199.6 - 145.5 Triassic 251.0 - 199.6 Paleozoic Permian 299.0 - 251.0 Carboniferous Pennsylvanian Sub-period 318.1 - 299.0 Mississippian Sub-period 359

Holtz Jr., Thomas R.

177

Broad absorption line variability on multi-year timescales in a large quasar sample  

NASA Astrophysics Data System (ADS)

Outflows launched near the central supermassive black holes (SMBHs) are a common and important component of active galactic nuclei (AGNs). Outflows in luminous AGNs (i.e., quasars) play a key role in mass accretion onto SMBH as well as in the feedback into host galaxies. The most prominent signature of such outflows appears as broad absorption lines (BALs) that are blueshifted from the emission line with a few thousands km s--1 velocities. In this dissertation, I place further constrains upon the size scale, internal structure, dynamics, and evolution of the outflows investigating profiles, properties, and variation characteristics of BAL troughs. I present observational results on BAL troughs in a large quasar sample utilizing spectroscopic observations from the Sloan Digital Sky Survey spanning on multi-year timescales. The results presented here, for the first time, provide a large and well-defined variability data base capable of discriminating between time-dependent hydrodynamic wind calculations in a statistically powerful manner. In a study of 582 quasars, I present 21 examples of BAL trough disappearance. Approximately 3.3% of BAL quasars show disappearing C IV trough on rest-frame timescales of 1.1--3.9 yr. BAL disappearance appears to occur mainly for shallow and weak or moderate-strength absorption troughs but not the strongest ones. When one BAL trough in a quasar spectrum disappears, the other present troughs usually weaken. Possible causes of such coordinated variations could be disk-wind rotation or variations of shielding gas that lead to variations of ionizing-continuum radiation. I present a detailed study on the variability of 428 C IV and 235 Si IV BAL troughs using a systematically observed sample of 291 BAL quasars. BAL variation distributions indicate that BAL disappearance is an extreme type of general BAL variability, rather than a qualitatively distinct phenomenon. The high observed frequency of BAL variability on multi-year timescales is generally supportive of models where most BAL absorption arises at radii of 10--1000 light days. Average lifetime for a BAL trough along our line-of-sight is a few thousand years which is long compared to the orbital time of the accretion disk at the wind-launching radius. We have examined if BAL variations on several timescales depend upon quasar properties, including quasar luminosity, Eddington luminosity ratio, black hole mass, redshift, and radio loudness. Within the ranges of these properties spanned by our sample, we do not find any strong dependences. The coordinated trough variability of BAL quasars with multiple troughs suggests that changes in "shielding gas" may play a significant role in driving general BAL variability. I present a study investigating the dependence of C IV BAL properties and variation characteristics on accompanying Si IV and Al III absorption. Results of this study show that C IV BAL trough shapes, depths, velocity widths and strengths show a strong dependence on the presence of Si IV and Al III BAL troughs at corresponding velocities. Similarly, the variation characteristics and depth variation profiles of C IV BAL troughs also show a strong connection to BAL troughs in these transitions. Using these ions as a basic tracer of ionization level of the absorbing gas, systematic measurements of variability and profiles for a large sample of C IV , Si IV, and Al III BAL troughs present observational evidences of the relation between ionization level, column density and kinematics of outflows. Utilizing observational investigations on a large BAL quasar sample, we show that ionization level, column density and kinematics of outflows show correlated object-to-object differences. We present a detailed comparison between the observational results of this study and the well studied disk-wind model of quasar outflows, which suggests that the wind is launched from the accretion disk at ˜ 1016--1017 cm and radiatively driven by UV line pressure. Results of this study show that lines-of-sight with different viewing inclinations suc

Filiz Ak, Nurten

178

Simulated Performance of Timescale Metrics for Aperiodic Light Curves  

NASA Astrophysics Data System (ADS)

Aperiodic variability is a characteristic feature of young stars, massive stars, and active galactic nuclei. With the recent proliferation of time-domain surveys, it is increasingly essential to develop methods to quantify and analyze aperiodic variability. We develop three timescale metrics that have been little used in astronomy—?m-?t plots, peak-finding, and Gaussian process regression—and present simulations comparing their effectiveness across a range of aperiodic light curve shapes, characteristic timescales, observing cadences, and signal to noise ratios. We find that Gaussian process regression is easily confused by noise and by irregular sampling, even when the model being fit reflects the process underlying the light curve, but that ?m-?t plots and peak-finding can coarsely characterize timescales across a broad region of parameter space. We make public the software we used for our simulations, both in the spirit of open research and to allow others to carry out analogous simulations for their own observing programs.

Findeisen, Krzysztof; Cody, Ann Marie; Hillenbrand, Lynne

2015-01-01

179

The Importance of Rotational Time-scales in Accretion Variability  

NASA Astrophysics Data System (ADS)

For the first few million years, one of the dominant sources of emission from a low mass young stellar object is from accretion. This process regulates the flow of material and angular moments from the surroundings to the central object, and is thought to play an important role in the definition of the long term stellar properties. Variability is a well documented attribute of accretion, and has been observed on time-scales of from days to years. However, where these variations come from is not clear. Th current model for accretion is magnetospheric accretion, where the stellar magnetic field truncates the disc, allowing the matter to flow from the disc onto the surface of the star. This model allows for variations in the accretion rate to come from many different sources, such as the magnetic field, the circumstellar disc and the interaction of the different parts of the system. We have been studying unbiased samples of accretors in order to identify the dominant time-scales and typical magnitudes of variations. In this way different sources of variations can be excluded and any missing physics in these systems identified. Through our previous work with the Long-term Accretion Monitoring Program (LAMP), we found 10 accretors in the ChaI region, whose variability is dominated by short term variations of 2 weeks. This was the shortest time period between spectroscopic observations which spanned 15 months, and rules out large scale processes in the disk as origins of this variability. On the basis of this study we have gone further to study the accretion signature H-alpha, over the time-scales of minutes and days in a set of Herbig Ae and T Tauri stars. Using the same methods as we used in LAMP we found the dominant time-scales of variations to be days. These samples both point towards rotation period of these objects as being an important time-scale for accretion variations. This allows us to indicate which are the most likely sources of these variations.

Costigan, Gráinne; Vink, Joirck; Scholz, Aleks; Testi, Leonardo; Ray, Tom

2013-07-01

180

The Collected Papers of Albert Einstein  

E-print Network

The Collected Papers of Albert Einstein The Collected Papers of Albert Einstein is one of the most from among more than 40,000 documents contained in the personal collection of Albert Einstein now housed at the Albert Ein- stein Archives at Hebrew University,and 15,000 Ein- stein and Einstein

Landweber, Laura

181

The Einstein Fellowship 2014 Awarded by the Einstein Forum and the Daimler and Benz Foundation  

E-print Network

, FROM THE APPLICANT'S PREVIOUS WORK. Albert Einstein-Stipendium 2014 Vergeben vom Einstein Forum und derThe Einstein Fellowship 2014 Awarded by the Einstein Forum and the Daimler and Benz Foundation The Einstein Forum and the Daimler and Benz Foundation are offering a fellowship for outstanding young thinkers

Heermann, Dieter W.

182

The Global Water Cycle Drives Volcanism on Seasonal to Millennial Timescales  

Microsoft Academic Search

Global rates of occurrence of volcanic eruptions show periodic behaviour on timescales ranging from 106 years. At long timescales (>106 to 107 years), rates of eruption are controlled by plate tectonics. At shorter timescales, the periodic nature of volcanism is forced by the global water cycle. Historical records of the rates of onset of eruption for the past 300 years

D. M. Pyle; B. G. Mason; T. E. Jupp; W. B. Dade

2005-01-01

183

Eddington-inspired Born-Infeld gravity: nuclear physics constraints and the validity of the continuous fluid approximation  

SciTech Connect

In this paper we investigate the classical non-relativistic limit of the Eddington-inspired Born-Infeld theory of gravity. We show that strong bounds on the value of the only additional parameter of the theory ?, with respect to general relativity, may be obtained by requiring that gravity plays a subdominant role compared to electromagnetic interactions inside atomic nuclei. We also discuss the validity of the continuous fluid approximation used in this and other astrophysical and cosmological studies. We argue that although the continuous fluid approximation is expected to be valid in the case of sufficiently smooth density distributions, its use should eventually be validated at a quantum level.

Avelino, P.P., E-mail: ppavelin@fc.up.pt [Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)

2012-11-01

184

Einstein's Thoughts on the Ether  

NSDL National Science Digital Library

Do light waves travel through the ether like waves on a lake travel through water? In this video segment adapted from NOVA, a young Albert Einstein grapples with this question while examining the speed of light.

2004-02-20

185

Video Gallery: Reflection on Einstein  

NSDL National Science Digital Library

This online video gallery is from the Museum's Seminars on Science, a series of distance-learning courses designed to help educators meet the new national science standards. Reflections on Einstein, part of the Frontiers in Physical Science seminar, is available in broadband and modem formats and with a printable PDF transcript. The video shows excerpts of a panel of seven scientists reflecting on Einstein's influence.

186

The NASA Beyond Einstein Program  

NASA Technical Reports Server (NTRS)

The Laser Interferometer Space Antenna (LISA) mission is part of NASA s Beyond Einstein program. This program seeks to answer the questions What Powered the Big Bang?, What happens at the edge of a Black Hole?, and What is Dark Energy?. LISA IS the first mission to be launched in this new program. This paper will give an overview of the Beyond Einstein program, its current status and where LISA fits in.

White, Nicholas E.

2004-01-01

187

Granular impact dynamics: Fluctuations at short time-scales  

NASA Astrophysics Data System (ADS)

Several recent studies on granular impact have used a macroscopic force law which describes the slow (mean) dynamics. However, these force-law models must be modified to capture large fluctuations at short time-scales. Here, we discuss granular impact experiments using photoelastic particles, where high-speed video captures both the intruder dynamics and the local granular force response. We show how to systematically separate the fluctuations from the mean dynamics. We also show that these fluctuations are multiplicative with the mean force, and otherwise decoupled from the dynamics. These observations are instructive in connecting to microscopic processes which generate the fluctuations.

Clark, Abram H.; Kondic, Lou; Behringer, R. P.

2013-06-01

188

Compaction and contraction: Densification timescales of porous magmas  

NASA Astrophysics Data System (ADS)

Cyclic explosive volcanic eruptions are often thought to be characterised by the formation and subsequent destruction of a dense, less-permeable plug. We investigated the timescales and deformation mechanisms that could lead to the formation of a denser plug or volcanic dome. We experimentally simulated conditions conducive to (1) high porosity magma compaction and (2) sintering of heterogeneous distributions of pyroclasts. Both of these processes likely play a role in conduit densification. High porosity magmas are texturally unstable when the included gas phase becomes connected and thereby depressurises at shallow levels. Within a scenario of syn-eruptive, decompression-driven vesiculation and crack network development during highly explosive events such as cyclic Vulcanian eruptions, unerupted magma that has developed high porosity in the vent will densify if the volcanic conduit temperatures remain high enough to suppress a significant melt viscosity increase. Further, fragmented material falling back into a hot volcanic conduit or that is forced into cracks in dense magma (tuffisites) will sinter and densify over similar timescales. We explore this densification timescale experimentally by returning erupted pumice (February 2010, Soufriere Hills volcano) to magmatic temperatures and measuring the evolution of the pore network via helium pycnometry, ultrasonic wave velocities and volumetric determinations. We find that magma can recover the high densities and low porosities typical of dome-forming magma over timescales proportional to 1) the viscosity of the melt phase, 2) the melt surface tension and 3) a measure of the dominant pore geometry and distribution. On this basis, we present a unique expression for the evolution of porosity or density as a function of the structural relaxation time of the melt phase. Finally, gas permeability and Lattice Boltzmann simulations on rendered pore volumes from 3D X-Ray computed micro-tomography elucidate the changing efficiency with which pore pressure can be dissipated during ductile densification. These tools enable a discussion of likely scenarios for the explosive-effusive transition, evolving suspension rheology and the repose interval of cyclic eruptions as well as the testing of current conceptual models of dense plug formation.

Wadsworth, F. B.; Scheu, B.; Vasseur, J.; kennedy, B.; Lavallee, Y.; Jones, T.; Hess, K.; Heap, M. J.; Dingwell, D. B.

2013-12-01

189

The NASA Beyond Einstein Program  

NASA Technical Reports Server (NTRS)

Einstein's legacy is incomplete, his theory of General relativity raises -- but cannot answer --three profound questions: What powered the big bang? What happens to space, time, and matter at the edge of a black hole? and What is the mysterious dark energy pulling the Universe apart? The Beyond Einstein program within NASA's Office of Space Science aims to answer these questions, employing a series of missions linked by powerful new technologies and complementary approaches towards shared science goals. The Beyond Einstein program has three linked elements which advance science and technology towards two visions; to detect directly gravitational wave signals from the earliest possible moments of the BIg Bang, and to image the event horizon of a black hole. The central element is a pair of Einstein Great Observatories, Constellation-X and LISA. Constellation-X is a powerful new X-ray observatory dedicated to X-Ray Spectroscopy. LISA is the first spaced based gravitational wave detector. These powerful facilities will blaze new paths to the questions about black holes, the Big Bang and dark energy. The second element is a series of competitively selected Einstein Probes, each focused on one of the science questions and includes a mission dedicated resolving the Dark Energy mystery. The third element is a program of technology development, theoretical studies and education. The Beyond Einstein program is a new element in the proposed NASA budget for 2004. This talk will give an overview of the program and the missions contained within it.

White, Nicholas E.

2006-01-01

190

The Einstein Slew Survey  

NASA Technical Reports Server (NTRS)

A catalog of 819 sources detected in the Einstein IPC Slew Survey of the X-ray sky is presented; 313 of the sources were not previously known as X-ray sources. Typical count rates are 0.1 IPC count/s, roughly equivalent to a flux of 3 x 10 exp -12 ergs/sq cm s. The sources have positional uncertainties of 1.2 arcmin (90 percent confidence) radius, based on a subset of 452 sources identified with previously known pointlike X-ray sources (i.e., extent less than 3 arcmin). Identifications based on a number of existing catalogs of X-ray and optical objects are proposed for 637 of the sources, 78 percent of the survey (within a 3-arcmin error radius) including 133 identifications of new X-ray sources. A public identification data base for the Slew Survey sources will be maintained at CfA, and contributions to this data base are invited.

Elvis, Martin; Plummer, David; Schachter, Jonathan; Fabbiano, G.

1992-01-01

191

Timescales of magma residence at Campi Flegrei, Italy  

NASA Astrophysics Data System (ADS)

Campi Flegrei caldera has produced many large explosive eruptions, including the largest in Europe in the last 200 kyrs. There have been more than 60 violent Strombolian-Vulcanian through to Plinian eruptions in the last 15 kyrs. Recent changes in ground displacement and composition of fumarole fluids indicate the caldera is still active and suggest that magma resides in the upper crust (Chiodini et al., 2012). Here we used zoned crystals within the post-15 ka eruption deposits to assess the timescales of upper crustal magma residence at Campi Flegrei. We present details of the major and trace element composition of the crystals, and diffusion chronometry results. These data provide detail on the crystallisation timescales and the changing nature of the magmatic system. It is clear that the magmas that fuel the eruptions are assembled in an open system and that upper crustal residence for most of the melt is short. Chiodini, G., Caliro, S., De Martino, P., Avino, R., Gherardi, F. 2012. Early signals of new volcanic unrest at Campi Flegrei caldera? Insights from geochemical data and physical simulations. Geology. http://dx.doi.org/10.1130/G33251.1

Smith, V. C.; Saunders, K.; Isaia, R.

2012-12-01

192

A Hierarchy of Time-Scales and the Brain  

PubMed Central

In this paper, we suggest that cortical anatomy recapitulates the temporal hierarchy that is inherent in the dynamics of environmental states. Many aspects of brain function can be understood in terms of a hierarchy of temporal scales at which representations of the environment evolve. The lowest level of this hierarchy corresponds to fast fluctuations associated with sensory processing, whereas the highest levels encode slow contextual changes in the environment, under which faster representations unfold. First, we describe a mathematical model that exploits the temporal structure of fast sensory input to track the slower trajectories of their underlying causes. This model of sensory encoding or perceptual inference establishes a proof of concept that slowly changing neuronal states can encode the paths or trajectories of faster sensory states. We then review empirical evidence that suggests that a temporal hierarchy is recapitulated in the macroscopic organization of the cortex. This anatomic-temporal hierarchy provides a comprehensive framework for understanding cortical function: the specific time-scale that engages a cortical area can be inferred by its location along a rostro-caudal gradient, which reflects the anatomical distance from primary sensory areas. This is most evident in the prefrontal cortex, where complex functions can be explained as operations on representations of the environment that change slowly. The framework provides predictions about, and principled constraints on, cortical structure–function relationships, which can be tested by manipulating the time-scales of sensory input. PMID:19008936

Kiebel, Stefan J.; Daunizeau, Jean; Friston, Karl J.

2008-01-01

193

Three-Dimensional General Relativistic Radiation Magnetohydrodynamical Simulation of Super-Eddington Accretion, using a new code HARMRAD with M1 Closure  

E-print Network

Black hole (BH) accretion flows and jets are dynamic hot relativistic magnetized plasma flows whose radiative opacity can significantly affect flow structure and behavior. We describe a numerical scheme, tests, and an astrophysically relevant application using the M1 radiation closure within a new three-dimensional (3D) general relativistic (GR) radiation (R) magnetohydrodynamics (MHD) massively parallel code called HARMRAD. Our 3D GRRMHD simulation of super-Eddington accretion (about $20$ times Eddington) onto a rapidly rotating BH (dimensionless spin $j=0.9375$) shows sustained non-axisymmemtric disk turbulence, a persistent electromagnetic jet driven by the Blandford-Znajek effect, and a total radiative output consistently near the Eddington rate. The total accretion efficiency is of order $20\\%$, the large-scale electromagnetic jet efficiency is of order $10\\%$, and the total radiative efficiency that reaches large distances remains low at only order $1\\%$. However, the radiation jet and the electromagnet...

McKinney, Jonathan C; Sadowski, Aleksander; Narayan, Ramesh

2013-01-01

194

Is radio jet power linearly proportional to the product of central black hole mass and Eddington ratio in AGN?  

NASA Astrophysics Data System (ADS)

A model for the relation between radio jet power and the product of central black hole (BH) mass and Eddington ratio of AGN is proposed, and the model is examined with data from the literature. We find that radio jet power positively correlates but not linearly with the product of BH mass ( m in solar mass) and Eddington ratio ( ?), and the power law indices ( ?) are significantly less than unity for relatively low accretion ( ?<0.1) AGN, P j ?( ?m) ? , in the radio galaxies and the Seyfert galaxies. This leads to a negative correlation between radio loudness and ?m for the low luminosity AGN, i.e. R?( ?m) ? with ?=(7/6) ?-1<0, which may be attributed to a contribution of BH spin to total jet power assuming that the spin induced jet is gradually suppressed as the accretion rate increases. Whereas, for the high- z quasars which often show the slope ??1, a positive correlation between the radio loudness and disc luminosity is predicted. We discuss that the jet powers of the high- z FRII quasars are likely dominated by the accretion disc rather than by the BH spin.

Liu, Xiang; Han, Zhenhua

2014-12-01

195

Correlations of the IR Luminosity and Eddington Ratio with a Hard X-ray Selected Sample of AGN  

NASA Technical Reports Server (NTRS)

We use the SWIFT Burst Alert Telescope (BAT) sample of hard x-ray selected active galactic nuclei (AGN) with a median redshift of 0.03 and the 2MASS J and K band photometry to examine the correlation of hard x-ray emission to Eddington ratio as well as the relationship of the J and K band nuclear luminosity to the hard x-ray luminosity. The BAT sample is almost unbiased by the effects of obscuration and thus offers the first large unbiased sample for the examination of correlations between different wavelength bands. We find that the near-IR nuclear J and K band luminosity is related to the BAT (14 - 195 keV) luminosity over a factor of 10(exp 3) in luminosity (L(sub IR) approx.equals L(sub BAT)(sup 1.25) and thus is unlikely to be due to dust. We also find that the Eddington ratio is proportional to the x-ray luminosity. This new result should be a strong constraint on models of the formation of the broad band continuum.

Mushotzy, Richard F.; Winter, Lisa M.; McIntosh, Daniel H.; Tueller, Jack

2008-01-01

196

Einstein's theory of wavefronts versus Einstein's relativity of simultaneity  

E-print Network

The relativity of simultaneity implies that the image of a Lorentz transformed (LT) spherical (circular) wavefront is not a spherical (circular) wavefront (Einstein 1905) but an ellipsoidal (elliptical) wavefront (Moreau, Am.J.of Phys).We show firstly that the relativity of simultaneity leads to the consequence that the image of a Lorentz transformed plane wavefront is a tangent plane to an ellipsoid and not a tangent plane to a sphere (Einstein 1905). We deduce then a longitudinal component of the tangent vector to Poincare's ellipse which is directly connected to the relativity of simultaneity. We suggest finally that this violation of relativity of simultaneity is related to Einstein's implicit choice of the (non relativistic) transverse gauge in his theory of (rigid) wavefronts.

Dr Yves Pierseaux

2006-06-27

197

Equilibration timescale of atmospheric secondary organic aerosol partitioning  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) formed from partitioning of oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs) accounts for a substantial portion of atmospheric particulate matter. In describing SOA formation, it is generally assumed that VOC oxidation products rapidly adopt gas-aerosol equilibrium. Here we estimate the equilibration timescale, ?eq, of SOA gas-particle partitioning using a state-of-the-art kinetic flux model. ?eq is found to be of order seconds to minutes for partitioning of relatively high volatility organic compounds into liquid particles, thereby adhering to equilibrium gas-particle partitioning. However, ?eq increases to hours or days for organic aerosol associated with semi-solid particles, low volatility, large particle size, and low mass loadings. Instantaneous equilibrium partitioning may lead to substantial overestimation of particle mass concentration and underestimation of gas-phase concentration.

Shiraiwa, Manabu; Seinfeld, John H.

2012-12-01

198

From lifetime to evolution: timescales of human gut microbiota adaptation  

PubMed Central

Human beings harbor gut microbial communities that are essential to preserve human health. Molded by the human genome, the gut microbiota (GM) is an adaptive component of the human superorganisms that allows host adaptation at different timescales, optimizing host physiology from daily life to lifespan scales and human evolutionary history. The GM continuously changes from birth up to the most extreme limits of human life, reconfiguring its metagenomic layout in response to daily variations in diet or specific host physiological and immunological needs at different ages. On the other hand, the microbiota plasticity was strategic to face changes in lifestyle and dietary habits along the course of the recent evolutionary history, that has driven the passage from Paleolithic hunter-gathering societies to Neolithic agricultural farmers to modern Westernized societies. PMID:25408692

Quercia, Sara; Candela, Marco; Giuliani, Cristina; Turroni, Silvia; Luiselli, Donata; Rampelli, Simone; Brigidi, Patrizia; Franceschi, Claudio; Bacalini, Maria Giulia; Garagnani, Paolo; Pirazzini, Chiara

2014-01-01

199

DYNAMICAL MASS SEGREGATION ON A VERY SHORT TIMESCALE  

SciTech Connect

We discuss the observations and theory of star cluster formation to argue that clusters form dynamically cool (subvirial) and with substructure. We then perform an ensemble of simulations of cool, clumpy (fractal) clusters and show that they often dynamically mass segregate on timescales far shorter than expected from simple models. The mass segregation comes about through the production of a short-lived, but very dense core. This shows that in clusters like the Orion Nebula Cluster the stars {>=} 4 M{sub sun} can dynamically mass segregate within the current age of the cluster. Therefore, the observed mass segregation in apparently dynamically young clusters need not be primordial, but could be the result of rapid and violent early dynamical evolution.

Allison, Richard J.; Goodwin, Simon P.; Parker, Richard J.; De Grijs, Richard; Kouwenhoven, M. B. N. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Portegies Zwart, Simon F. [Leiden Observatory, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)], E-mail: r.allison@sheffield.ac.uk

2009-08-01

200

Modes of embayed beach dynamics: analysis reveals emergent timescales  

NASA Astrophysics Data System (ADS)

Embayed beaches, or beaches positioned between rocky headlands, exhibit morphologic changes over many length and time scales. Beach sediment is transported as a result of the day-to-day wave forcing, causing patterns of erosion and accretion. We use the Rocky Coastline Evolution Model (RCEM) to investigate how patterns of shoreline change depend on wave climate (the distribution of wave-approach angles) and beach characteristics. Measuring changes in beach width through time allows us to track the evolution of the shape of the beach and the movement of sand within it. By using Principle Component Analysis (PCA), these changes can be categorized into modes, where the first few modes explain the majority of the variation in the time series. We analyze these modes and how they vary as a function of wave climate and headland/bay aspect ratio. In the purposefully simple RCEM, sediment transport is wave-driven and affected by wave shadowing behind the headlands. The rock elements in our model experiments (including the headlands) are fixed and unerodable so that this analysis can focus purely on sand dynamics between the headlands, without a sand contribution from the headlands or cliffs behind the beach. The wave climate is characterized by dictating the percentage of offshore waves arriving from the left and the percentage of waves arriving from high angles (very oblique to the coastline orientation). A high-angle dominated wave climate tends to amplify coastline perturbations, whereas a lower-angle wave climate is diffusive. By changing the headland/bay aspect ratio and wave climate, we can perform PCA analysis of generalized embayed beaches with differing anatomy and wave climate forcings. Previous work using PCA analysis of embayed beaches focused on specific locations and shorter timescales (<30 years; Short and Trembanis, 2004). By using the RCEM, we can more broadly characterize beach dynamics over longer timescales. The first two PCA modes, which explain a majority of the beach width time series variation (typically >70%), are a 'breathing' mode and a 'rotational' mode. The newly identified breathing mode captures the sand movement from the middle of the beach towards the edges (thickening the beach along the headlands), and the rotational mode describes the movement of sand towards one headland or another, both in response to stochastic fluctuations about the mean wave climate. The two main modes operate independently and on different timescales. In a weakly low-angle dominated wave climate, the breathing mode tends to be the first mode (capturing the most variance), but with greater low-angle dominance (greater morphological diffusivity), the rotational mode tends to be first. The aspect ratio of the bay also affects the order of the modes, because wave shadowing affects sediment transport behind the headlands. Previous work has attributed beach rotation to changes in various climate indices such as the North Atlantic Oscillation (Thomas et al., 2011); however, PCA analysis of the RCEM results suggests that embayed beaches can have characteristic timescales of sand movement that result from internal system dynamics, emerging even within a statistically constant wave climate. These results suggest that morphologic changes in embayed beaches can occur independently of readily identifiable shifts in forcing.

Murray, K. T.; Murray, A.; Limber, P. W.; Ells, K. D.

2013-12-01

201

Timescales for localized electron injections to become a thin shell  

NASA Astrophysics Data System (ADS)

Timescales for localized injections of electrons into the Earth's inner magnetosphere to spread into a thin shell are presented. The Radiation Belt Environment (RBE) model is used to numerically examine this topic, initializing the simulations with an MLT-confined Gaussian peak of electrons. Near the slot region, where the numerical experiments are conducted (L=3), the transition from a localized injection into a thin shell is driven by scattering with plasmaspheric hiss, shifting the energy and pitch angle of the particles, and ULF waves, shifting the radial location of the particles, all of which changes the drift speed. This mixing is energy dependent, taking much longer at the lower energies. It is shown that during static driving conditions it takes >3 hours for a narrow-MLT initial distribution of MeV-energy electrons to transform into a uniformly distributed ring, but takes more than 6 hours for < 300 keV electrons to achieve a thin shell state. During a magnetic storm interval, the timescale to reach a thin shell is somewhat shorter as the large-scale fluctuations of the magnetic field diffuse the particles in radial distance, enhancing the mixing. Interestingly, some parts of velocity space take longer with the magnetic fluctuations included, and the influence of the hiss scattering is modified as well. The implication is that localized injections, from the tail or from another source, do not become symmetric in local time for several hours, during which MLT-dependent interactions can play a significant role on the evolution and dynamics of the population.

Liemohn, Michael; Fok, Mei-Ching; Zheng, Qiuhua.; Xu, Shaosui

202

HOST GALAXIES, CLUSTERING, EDDINGTON RATIOS, AND EVOLUTION OF RADIO, X-RAY, AND INFRARED-SELECTED AGNs  

SciTech Connect

We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of AGNs selected in the radio, X-ray, and infrared (IR) wavebands. We study a sample of 585 AGNs at 0.25 < z < 0.8 using redshifts from the AGN and Galaxy Evolution Survey (AGES). We select AGNs with observations in the radio at 1.4 GHz from the Westerbork Synthesis Radio Telescope, X-rays from the Chandra XBooetes Survey, and mid-IR from the Spitzer IRAC Shallow Survey. The radio, X-ray, and IR AGN samples show only modest overlap, indicating that to the flux limits of the survey, they represent largely distinct classes of AGNs. We derive host galaxy colors and luminosities, as well as Eddington ratios, for obscured or optically faint AGNs. We also measure the two-point cross-correlation between AGNs and galaxies on scales of 0.3-10 h {sup -1} Mpc, and derive typical dark matter halo masses. We find that: (1) radio AGNs are mainly found in luminous red sequence galaxies, are strongly clustered (with M {sub halo} {approx} 3 x 10{sup 13} h {sup -1} M {sub sun}), and have very low Eddington ratios {lambda} {approx}< 10{sup -3}; (2) X-ray-selected AGNs are preferentially found in galaxies that lie in the 'green valley' of color-magnitude space and are clustered similar to the typical AGES galaxies (M {sub halo} {approx} 10{sup 13} h {sup -1} M {sub sun}), with 10{sup -3} {approx}< {lambda} {approx}< 1; (3) IR AGNs reside in slightly bluer, slightly less luminous galaxies than X-ray AGNs, are weakly clustered (M {sub halo} {approx}< 10{sup 12} h {sup -1} M {sub sun}), and have {lambda}>10{sup -2}. We interpret these results in terms of a simple model of AGN and galaxy evolution, whereby a 'quasar' phase and the growth of the stellar bulge occurs when a galaxy's dark matter halo reaches a critical mass between {approx}10{sup 12} and 10{sup 13} M {sub sun}. After this event, star formation ceases and AGN accretion shifts from radiatively efficient (optical- and IR-bright) to radiatively inefficient (optically faint, radio-bright) modes.

Hickox, Ryan C.; Jones, Christine; Forman, William R.; Murray, Stephen S.; Brodwin, Mark; Narayan, Ramesh; Kenter, Almus; Caldwell, Nelson; Anderson, Michael E. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kochanek, Christopher S. [Department of Astronomy and Center for Cosmology and Astroparticle Physics, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210-1173 (United States); Eisenstein, Daniel [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Jannuzi, Buell T.; Dey, Arjun [National Optical Astronomy Observatory, Tucson, AZ 85726-6732 (United States); Brown, Michael J. I. [School of Physics, Monash University, Clayton 3800, Victoria (Australia); Stern, Daniel; Eisenhardt, Peter R.; Gorjian, Varoujan [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Cool, Richard J. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544-1001 (United States)], E-mail: rhickox@cfa.harvard.edu

2009-05-01

203

Schwinger's Approach to Einstein's Gravity  

NASA Astrophysics Data System (ADS)

Albert Einstein was one of Julian Schwinger's heroes, and Schwinger was greatly honored when he received the first Einstein Prize (together with Kurt Godel) for his work on quantum electrodynamics. Schwinger contributed greatly to the development of a quantum version of gravitational theory, and his work led directly to the important work of (his students) Arnowitt, Deser, and DeWitt on the subject. Later in the 1960's and 1970's Schwinger developed a new formulation of quantum field theory, which he dubbed Source Theory, in an attempt to get closer contact to phenomena. In this formulation, he revisited gravity, and in books and papers showed how Einstein's theory of General Relativity emerged naturally from one physical assumption: that the carrier of the gravitational force is a massless, helicity-2 particle, the graviton. (There has been a minor dispute whether gravitational theory can be considered as the massless limit of a massive spin-2 theory; Schwinger believed that was the case, while Van Dam and Veltman concluded the opposite.) In the process, he showed how all of the tests of General Relativity could be explained simply, without using the full machinery of the theory and without the extraneous concept of curved space, including such effects as geodetic precession and the Lense-Thirring effect. (These effects have now been verified by the Gravity Probe B experiment.) This did not mean that he did not accept Einstein's equations, and in his book and full article on the subject, he showed how those emerge essentially uniquely from the assumption of the graviton. So to speak of Schwinger versus Einstein is misleading, although it is true that Schwinger saw no necessity to talk of curved spacetime. In this talk I will lay out Schwinger's approach, and the connection to Einstein's theory.

Milton, Kim

2012-05-01

204

Einstein Session of the Pontifical Academy.  

ERIC Educational Resources Information Center

The texts of four speeches, given at the 1979 Einstein Session of the Pontifical Academy held in Rome, are presented. Each address relates to some aspect of the life and times of Albert Einstein. (SA)

Science, 1980

1980-01-01

205

Einstein: The Man of the Century  

NSDL National Science Digital Library

This short biographical sketch of Albert Einstein gives a brief overview of his life and science. The second page gives a brief explanation of Einstein's major contributions to science including relativity and quantum mechanics.

2009-06-09

206

Galileo and Einstein Home Page  

NSDL National Science Digital Library

These lecture notes from Michael Fowler, Physics professor at University of Virginia, explore "two revolutions in our perception of the universe," the impacts of Galileo and then Einstein on our understanding of physics. The 27 lectures included here may be a useful supplement and teaching aid for educators. The lectures begin with the early Greeks and follow the progress of scientific thought through the work of Galileo, Isaac Newton, and Einstein. The lectures themselves are clear and offer interesting historic details and a conversational approach to explaining concepts. Though the lectures were written a few years ago, the content is timeless, and many of the lectures have been recently updated.

207

Galileo and Einstein: Physics Flashlets  

NSDL National Science Digital Library

This is a collection of Flash animations developed to support a course in introductory historical astronomy. The "Flashlets" are presented sequentially, beginning with early Greek science and Galilean motion. The series progresses through the Kepler's and Newton's Laws and culminates in Einstein's theory of special relativity and time dilation. This collection is part of a larger set of curriculum materials developed at the University of Virginia for the course "Galileo and Einstein". See Related Materials for a link to the full index, which includes lecture notes, Java simulations, and historical excerpts.

Fowler, Michael

2008-07-29

208

Einstein: Physicist, Philosopher, Humanitarian Youngstown State March 25, 2009 Albert Einstein: Physicist,  

E-print Network

Einstein: Physicist, Philosopher, Humanitarian ­ Youngstown State ­ March 25, 2009 Albert Einstein and Philosophy of Science University of Notre Dame Youngstown State University March 25, 2009 Einstein as a college student, ca. 1900 #12;Einstein: Physicist, Philosopher, Humanitarian ­ Youngstown State ­ March 25

Howard, Don

209

Einstein Solid Temperature Demon Worksheet and Model  

NSDL National Science Digital Library

A worksheet that considers an Einstein solid in contact with a temperature demon (a single oscillator thermometer that exchanges energy with the Einstein solid). The combined solid-demon system is isolated. The number of energy units in this system can be adjusted by editing the field in the main display. All of this energy is originally in the Einstein solid, but after interaction starts it is shared between the demon and the Einstein solid.

Wheaton, Spencer

2013-08-16

210

winter 2008 I EinstEin EINSTEINwinter 2008  

E-print Network

:Apublicationforfaculty,students,alumni,friendsandsupporters oftheAlbertEinsteinCollegeofMedicineofYeshivaUniversity. Visitusonlineatwww.aecom.yu.edu. ©2008Volume28winter 2008 I EinstEin EINSTEINwinter 2008 THE EINSTEIN EDGE TODAY'S SCIENCE... TOMORROW'S MEDICINE #12; EinstEin I winter 2008 winter 2008 I EinstEin EINSTEINCONTENTSwinter 2008 EINSTEIN

Yates, Andrew

211

The General Introduction of Einstein meets Magritte  

E-print Network

long and exhausting and the press were doing all they could to get Albert Einstein and Ren´e MagritteThe General Introduction of Einstein meets Magritte Diederik Aerts, Center Leo Apostel, Brussels Free University, Brussels, Belgium. The series of books `Einstein meets Magritte' presented here

Aerts, Diederik

212

100 years since Einstein's less known revolution  

E-print Network

) to their microscopic components and interactions with the environment. Albert Einstein made crucial contributions of semi-conductors and the computer revolution that followed. It is amazing that Albert Einstein when he1 100 years since Einstein's less known revolution: From the pollen dance to atoms and back

Andelman, David

213

First strike Sixty years ago, Albert Einstein  

E-print Network

First strike Sixty years ago, Albert Einstein said that the existence of nuclear weapons would physicists, including Einstein, have argued that the first use of nuclear weapons can never again. Einstein's hope of new thinking in a nuclear world may be too much to expect, but I hope

Rhoads, James

214

Einstein Room Reservations Rules and Regulations  

E-print Network

in accordance to Albert Einstein College of Medicine's Alcohol Policy. Before your request is confirmed you mustEinstein Room Reservations Rules and Regulations Before Reservation: Requests are not confirmed Activities, Joan Junger, (718) 430-2105 or student.activities@einstein.yu.edu. A meeting or conversation

Yates, Andrew

215

Albert Einstein: Relativity, War, Daniel J. Kevles  

E-print Network

Albert Einstein: Relativity, War, and Fame Daniel J. Kevles In 1922, Princeton University Press published Albert Einstein's The Meaning of Relativity, a popularization of his theory that has remained as succes- sive editions of his writings appear. Albert Einstein burst upon the world of physics in 1905

Landweber, Laura

216

Albert Einstein, 1905: Ein 3-Gange Menu  

E-print Network

. Albert Einstein, 1905: Ein 3-G¨ange Men¨u In Zusammenarbeit mit dem Deutschen Museum Bonn 6. M: Michael Kortmann, Markus Bernhardt #12;. Albert Einstein, 1905: Ein 3-G¨ange Physik draan #12;Speiseplan Einstein 1905: Biografisches ***** Brownsche Molekularbewegung

Dutz, Hartmut

217

Stability and (quasi)localization of gravitational fluctuations in an Eddington-inspired Born-Infeld brane system  

NASA Astrophysics Data System (ADS)

The stability and localization of the gravitational perturbations for a special brane system in Eddington-inspired Born-Infeld gravity were studied in Liu et al. [Phys. Rev. D 85, 124053 (2012)]. In this paper, we show that the gravitational perturbations for a general brane system are stable, the four-dimensional graviton (massless KK graviton) can be localized on the brane, and the mass spectra of massive KK gravitons are gapless and continuous. Two models are constructed as examples. In the first model, which is a generalization of Liu et al. [Phys. Rev. D 85, 124053 (2012)], the brane has no inner structure and there is no gravitational resonance (quasilocalized KK gravitons). In the second one, the background scalar field is a double kink when the parameter in the model approaches its critical value. Correspondingly, the brane has inner structure and some gravitational resonances appear.

Fu, Qi-Ming; Zhao, Li; Yang, Ke; Gu, Bao-Min; Liu, Yu-Xiao

2014-11-01

218

Host galaxies, clustering, Eddington ratios, and evolution of radio, X-ray, and infrared-selected AGNs  

E-print Network

We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of AGNs selected in the radio, X-ray, and infrared. We study a sample of 585 AGNs at 0.25 10^-2. We interpret these results i n terms of a simple model of AGN and galaxy evolution, whereby a "quasar" phase and the growth of the stellar bulge occurs when a galaxy's dark matter halo reaches a critical mass between ~10^12 and 10^13 M_sun. Subsequently, star formation ceases and AGN accretion shifts from radiatively efficient (optical- and IR- bright) to radiatively inefficient (optically-faint, radio-bright) modes.

Hickox, Ryan C; Forman, William R; Murray, Stephen S; Kochanek, Christopher S; Eisenstein, Daniel; Jannuzi, Buell T; Dey, Arjun; Brown, Michael J I; Stern, Daniel; Eisenhardt, Peter R; Gorjian, Varoujan; Brodwin, Mark; Narayan, Ramesh; Cool, Richard J; Kenter, Almus; Caldwell, Nelson; Anderson, Michael E

2009-01-01

219

Quasar Jets on the kpc scale: Fast and Super-Eddington or Slow and Multi-TeV Accelerators?  

NASA Astrophysics Data System (ADS)

A long-standing debate exists around the nature of the anomalously high X-ray emission from the kpc-scale resolved quasar jet emission, which is related to the question of their speeds on the kpc scale. Are they fast (Lorentz factors ~10-20) and powerful (in many cases super-Eddington) or slow, sub-Eddington, and multi-TeV particle accelerators?. This question has direct bearing on the physics of cluster heating by powerful jets. Also, the slow jet case implies that the beaming-corrected radiated power of the jet on kpc scales may be comparable to, or even exceed that of the blazar (core) emission, with important implications for the GeV background radiation and the heating of intergalactic gas by TeV photons. The widely accepted model for producing the high X-ray emission has been a highly-relativistic kpc-scale jet producing inverse Compton emission by up-scattering the cosmic microwave background (IC/CMB), though the X-rays could also be synchrotron emission from a multi-TeV electron population accelerated in situ, as both models can reproduce the observed radio to X-ray spectra. We present very recent work by our group, showing that IC/CMB model is ruled out in at least two cases. In both 3C 273 PKS 0637-752, the uniquely determined GeV flux predicted by the IC/CMB model overproduces the 99.9% flux limits obtained from recent Fermi gamma-ray observations.

Meyer, Eileen T.; Georganopoulos, Markos; Sparks, William B.

2014-08-01

220

On Conformally Kaehler, Einstein Manifolds  

E-print Network

We prove that any compact complex surface with positive first Chern class admits an Einstein metric which is conformally related to a Kaehler metric. The key new ingredient is the existence of such a metric on the blow-up of the complex projective plane at two distinct points.

Xiuxiong Chen; Claude LeBrun; Brian Weber

2007-05-07

221

Einstein, Black Holes Gravitational Waves  

E-print Network

of physics look and work the same in any inertial frame. · The speed of light is a universal constant for all of Zurich, published 1906. application of kinetic theory to the physical properties of solute sugar molecules ­ Greg Cook ­ (WFU Physics) 3 #12;Goals For This Talk · What is Einstein's Theory of General

Cook, Greg

222

Approaching Bose-Einstein Condensation  

ERIC Educational Resources Information Center

Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…

Ferrari, Loris

2011-01-01

223

Scientific Potential of Einstein Telescope  

Microsoft Academic Search

Einstein gravitational-wave Telescope (ET) is a design study funded by the European Commission to explore the technological challenges of and scientific benefits from building a third generation gravitational wave detector. The three-year study, which concluded earlier this year, has formulated the conceptual design of an observatory that can support the implementation of new technology for the next two to three

B. Sathyaprakash; M. Abernathy; F. Acernese; P. Amaro-Seoane N. Andersson; K. Arun; F. Barone; B. Barr; M. Barsuglia; M. Beker N. Beveridge; S. Birindelli; S. Bose; L. Bosi; S. Braccini; C. Bradaschia; T. Bulik; E. Calloni; G. Cella; E. Chassande. Mottin; S. Chelkowski; A. Chincarini; J. Clark; E. Coccia; C. Colacino; J. Colas; A. Cumming; L. Cunningham; E. Cuoco; S. Danilishin; K. Danzmann; R. De. Salvo; T. Dent; R. De. Rosa; L. Di. Fiore; A. Di. Virgilio; M. Doets; V. Fafone; P. Falferi; R. Flaminio; J. Franc; F. Frasconi; A. Freise; D. Friedrich; P. Fulda; J. Gair; G. Gemme; E. Genin; A. Gennai; A. Giazotto; K. Glampedakis; C. Gräf; M. Granata; H. Grote; G. Guidi; A. Gurkovsky; G. Hammond; M. Hannam; J. Harms; D. Heinert; M. Hendry; I. Heng; E. Hennes; S. Hild; J. Hough; S. Husa; S. Huttner; G. Jones; F. Khalili; K. Kokeyama; K. Kokkotas; B. Krishnan; T. G. F. Li; M. Lorenzini; H. Lück; E. Majorana; I. Mandel; V. Mandic; M. Mantovani; I. Martin; C. Michel; Y. Minenkov; N. Morgado; S. Mosca; B. Mours; H. Müller--Ebhardt; P. Murray; R. Nawrodt; J. Nelson; R. Oshaughnessy; C. D. Ott; C. Palomba; A. Paoli; G. Parguez; A. Pasqualetti; R. Passaquieti; D. Passuello; L. Pinard; W. Plastino; R. Poggiani; P. Popolizio; M. Prato; M. Punturo; P. Puppo; D. Rabeling; I. Racz; P. Rapagnani; J. Read; T. Regimbau; H. Rehbein; S. Reid; L. Rezzolla; F. Ricci; F. Richard; A. Rocchi; S. Rowan; A. Rüdiger; L. Santamaría; B. Sassolas; R. Schnabe; C. Schwarz; P. Seidel; A. Sintes; K. Somiya; F. Speirits; K. Strain; S. Strigin; P. Sutton; S. Tarabrin; A. Thüring; J. van. den. Brand; M. van. Veggel; C. van. den. Broeck; A. Vecchio; J. Veitch; F. Vetrano; A. Vicere; S. Vyatchanin; B. Willke; G. Woan; K. Yamamoto

2011-01-01

224

Spatial Bose-Einstein Condensation.  

ERIC Educational Resources Information Center

Analyzes three examples of spatial Bose-Einstein condensations in which the particles macroscopically occupy the lowest localized state of an inhomogeneous external potential. The three cases are (1) a box with a small square potential well inside, (2) a harmonic oscillator potential, and (3) randomly sized trapping potentials caused by…

Masut, Remo; Mullin, William J.

1979-01-01

225

Schroedinger's cat in Einstein's box  

E-print Network

Using the Einstein's boxes thought experiment, as well as EPR and Heisenberg's ones, the local-realistic hidden-variable interpretation of quantum mechanics is explained. The key hidden variable is the consciousness forecasting the future. It is supposed that atoms and particles are complex products of evolution.

Raoul Nakhmanson

2005-08-19

226

Indian Monsoon-ENSO Relationship on Interdecadal Timescale.  

NASA Astrophysics Data System (ADS)

Empirical evidence is presented to support a hypothesis that the interdecadal variation of the Indian summer monsoon and that of the tropical SST are parts of a tropical coupled ocean-atmosphere mode. The interdecadal variation of the Indian monsoon rainfall (IMR) is strongly correlated with the interdecadal variations of various indices of El Niño-Southern Oscillation (ENSO). It is also shown that the interannual variances of both IMR and ENSO indices vary in phase and follow a common interdecadal variation. However, the correlation between IMR and eastern Pacific SST or between IMR and Southern Oscillation index (SOI) on the interannual timescale does not follow the interdecadal oscillation. The spatial patterns of SST and sea level pressure (SLP) associated with the interdecadal variation of IMR are nearly identical to those associated with the interdecadal variations of ENSO indices. As has been shown earlier in the case of ENSO, the global patterns associated with the interdecadal and interannual variability of the Indian monsoon are quite similar.The physical link through which ENSO is related to decreased monsoon rainfall on both interannual and interdecadal timescales has been investigated using National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis products. The decrease in the Indian monsoon rainfall associated with the warm phases of ENSO is due to an anomalous regional Hadley circulation with descending motion over the Indian continent and ascending motion near the equator sustained by the ascending phase of the anomalous Walker circulation in the equatorial Indian Ocean. It is shown that, to a large extent, both the regional Hadley circulation anomalies and Walker circulation anomalies over the monsoon region associated with the strong (weak) phases of the interdecadal oscillation are similar to those associated with the strong (weak) phases of the interannual variability. However, within a particular phase of the interdecadal oscillation, there are several strong and weak phases of the interannual variation. During a warm eastern Pacific phase of the interdecadal variation, the regional Hadley circulation associated with El Niño reinforces the prevailing anomalous interdecadal Hadley circulation while that associated with La Niña opposes the prevailing interdecadal Hadley circulation. During the warm phase of the interdecadal oscillation, El Niño events are expected to be strongly related to monsoon droughts while La Niña events may not have significant relation. On the other hand, during the cold eastern Pacific phase of the interdecadal SST oscillation, La Niña events are more likely to be strongly related to monsoon floods while El Niño events are unlikely to have a significant relation with the Indian monsoon. This picture explains the observation that the correlations between IMR and ENSO indices on the interannual timescale do not follow the interdecadal oscillation as neither phase of the interdecadal oscillation favors a stronger (or weaker) correlation between monsoon and ENSO indices.

Krishnamurthy, V.; Goswami, B. N.

2000-02-01

227

Complex Processes from Dynamical Architectures with Time-Scale Hierarchy  

PubMed Central

The idea that complex motor, perceptual, and cognitive behaviors are composed of smaller units, which are somehow brought into a meaningful relation, permeates the biological and life sciences. However, no principled framework defining the constituent elementary processes has been developed to this date. Consequently, functional configurations (or architectures) relating elementary processes and external influences are mostly piecemeal formulations suitable to particular instances only. Here, we develop a general dynamical framework for distinct functional architectures characterized by the time-scale separation of their constituents and evaluate their efficiency. Thereto, we build on the (phase) flow of a system, which prescribes the temporal evolution of its state variables. The phase flow topology allows for the unambiguous classification of qualitatively distinct processes, which we consider to represent the functional units or modes within the dynamical architecture. Using the example of a composite movement we illustrate how different architectures can be characterized by their degree of time scale separation between the internal elements of the architecture (i.e. the functional modes) and external interventions. We reveal a tradeoff of the interactions between internal and external influences, which offers a theoretical justification for the efficient composition of complex processes out of non-trivial elementary processes or functional modes. PMID:21347363

Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor

2011-01-01

228

Titan's evaporites structure and their formation time-scale  

NASA Astrophysics Data System (ADS)

Hydrocarbons lakes have been discovered in polar regions of Titan (Stofan et al. 2007) [1]. Already, Stofan et al. (2007) noticed features suggesting the occurence of an evaporation process in the recent past. Barnes et al. (2009) [2] performed a detailed study of shoreline features of Ontario Lacus, they interpreted the 5-?m brigth annulus around this lakes as a dry, low-water ice content zone, possibly corresponding to a deposit of organic condensates. Barnes et al. (2011) [3] used a sample of several lakes and lakebeds located in a region south of the Ligeia Mare. They got a strong correlation between RADAR-empty lakes and 5-?m brigth units interpreted as low-water ice content areas. On the theoretical side, Cordier et al. (2013) [4] elaborated a model for the chemical composition of the external layer of these possible organic evaporite deposits. This model was based on a simplified theory of dissolution (ideal solution and regular solution theory) and all computations were performed using a time-scale which did not enable any estimation for the depth of deposits layers.

Cordier, D.; Barnes, J.; Le Bahers, T.; Cornet, T.; Ferreira, A.

2014-04-01

229

Thermal Timescale Mass Transfer In Binary Population Synthesis  

NASA Astrophysics Data System (ADS)

Studies of binary evolution have, until recently, neglected thermal timescale mass transfer (TTMT). Recent work has suggested that this previously poorly studied area is crucial in the understanding of systems across the compact binary spectrum. We use the state-of-the-art binary population synthesis code BiSEPS (Willems and Kolb, 2002, MNRAS 337 1004-1016). However, the present treatment of TTMT is incomplete due to the nonlinear behaviour of stars in their departure from gravothermal `equilibrium'. Here we show work that should update the ultrafast stellar evolution algorithms within BiSEPS to make it the first pseudo-analytic code that can follow TTMT properly. We have generated fits to a set of over 300 Case B TTMT sequences with a range of intermediate-mass donors. These fits produce very good first approximations to both HR diagrams and mass-transfer rates (see figures 1 and 2), which we later hope to improve and extend. They are already a significant improvement over the previous fits.

Justham, S.; Kolb, U.

2004-07-01

230

Relaxation in polymer electrolytes on the nanosecond timescale  

NASA Astrophysics Data System (ADS)

The relation between mechanical and electrical relaxation in polymer/lithium-salt complexes is a fascinating and still unresolved problem in condensed-matter physics, yet has an important bearing on the viability of such materials for use as electrolytes in lithium batteries. At room temperature, these materials are biphasic: they consist of both fluid amorphous regions and salt-enriched crystalline regions. Ionic conduction is known to occur predominantly in the amorphous fluid regions. Although the conduction mechanisms are not yet fully understood, it is widely accepted that lithium ions, coordinated with groups of ether oxygen atoms on single or perhaps double polymer chains, move through re-coordination with other oxygen-bearing groups. The formation and disruption of these coordination bonds must be accompanied by strong relaxation of the local chain structure. Here we probe the relaxation on a nanosecond timescale using quasielastic neutron scattering, and we show that at least two processes are involved: a slow process with a translational character and one or two fast processes with a rotational character. Whereas the former reflects the slowing-down of the translational relaxation commonly observed in polyethylene oxide and other polymer melts, the latter appears to be unique to the polymer electrolytes and has not (to our knowledge) been observed before. A clear picture emerges of the lithium cations forming crosslinks between chain segments and thereby profoundly altering the dynamics of the polymer network.

Mao, Guomin; Perea, Ricardo Fernandez; Howells, W. Spencer; Price, David L.; Saboungi, Marie-Louise

2000-05-01

231

A multilocus timescale for the origin of extant amphibians.  

PubMed

One of the most hotly debated topics in vertebrate evolution is the origin of extant amphibians (Lissamphibia). The recent contribution of molecular data is shedding new light on this debate, but many important questions still remain unresolved. I have assembled a large and comprehensive multilocus dataset (the largest to date in terms of number and heterogeneity of sequence characters) combining mitogenomic and nuclear information from 23 genes for a sufficiently dense taxon sampling with the key major lineages of extant amphibians. This dataset has been used to infer a robust phylogenetic framework and molecular timescale for the origin of extant amphibians employing the most recent phylogenetic and dating methods, as well as several alternative calibration schemes. The monophyly of each extant amphibian order and the sister group relationship between frogs and salamanders (Batrachia hypothesis) are all strongly supported. Dating analyses (all methods and calibration schemes used) suggest that the origin of extant amphibians (divergence between caecilian and batrachians) occurred in the Late Carboniferous, around 315 Mya, and the divergence between frogs and salamanders occurred in the Early Permian, around 290 Mya. These age estimates are more consistent with the fossil record than previous older estimates, and more in line with the Temnospondyli or the Lepospondyli hypotheses of lissamphibian ancestry (although the polyphyly hypothesis cannot be completely ruled out). PMID:20399871

San Mauro, Diego

2010-08-01

232

On the Chronometry and Metrology of Computer Network Timescales and their Application to the Network Time  

E-print Network

On the Chronometry and Metrology of Computer Network Timescales and their Application, and on calendar metrology, which is the determination of conventional civil time and date according to the modern. Reprinted from: Mills, D.L. On the chronology and metrology of computer network timescales and thei

Mills, David L.

233

On the Chronometry and Metrology of Computer Network Timescales and their Application to the Network Time  

E-print Network

On the Chronometry and Metrology of Computer Network Timescales and their Application, and on calendar metrology, which is the determination of conventional civiltimeand date according to the modern, D.L. On the chronology and metrology of computer network timescales and their application

Mills, David L.

234

Unifying Einstein and Palatini gravities  

SciTech Connect

We consider a novel class of f(R) gravity theories where the connection is related to the conformally scaled metric g{sub {mu}{nu}=}C(R)g{sub {mu}{nu}} with a scaling that depends on the scalar curvature R only. We call them C theories and show that the Einstein and Palatini gravities can be obtained as special limits. In addition, C theories include completely new physically distinct gravity theories even when f(R)=R. With nonlinear f(R), C theories interpolate and extrapolate the Einstein and Palatini cases and may avoid some of their conceptual and observational problems. We further show that C theories have a scalar-tensor formulation, which in some special cases reduces to simple Brans-Dicke-type gravity. If matter fields couple to the connection, the conservation laws in C theories are modified. The stability of perturbations about flat space is determined by a simple condition on the Lagrangian.

Amendola, Luca; Enqvist, Kari; Koivisto, Tomi [Institut fuer Theoretische Physik, University of Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); Physics Department, University of Helsinki, and Helsinki Institute of Physics, FIN-00014 University of Helsinki (Finland); Institute for Theoretical Physics and Spinoza Institute, Leuvenlaan 4, 3584 CE Utrecht (Netherlands)

2011-02-15

235

Albert Einstein, Cosmos and Religion  

NASA Astrophysics Data System (ADS)

We consider Einstein's attitude regarding religious as such, from both cosmological and epistemological points of view. An attempt to put it into a wider socio-historical perspective was made, with the emphasis on ethnic and religious background. It turns out that the great scientist was neither atheist nor believer in the orthodox sense and the closest labels one might stick to him in this respect would be pantheism/cosmism (ontological aspect) and agnosticism (epistemological aspect). His ideas on divine could be considered as a continuation of line traced by Philo of Alexandria, who himself followed Greek Stoics and (Neo-) Platonists and especially Baruch Spinoza. It turns out that Einstein's both scientific (rational aspects) and religious (intuitive aspects) thinking were deeply rooted in the Hellenic culture. His striving to unravel the secrets of the universe and the roots of cosmological order resembles much the ancient ideas of the role of knowledge in fathoming the divine as such, as ascribed to Gnostics.

Djokovic, V.; Grujic, P.

2007-06-01

236

Albert Einstein and Scientific Theology  

E-print Network

In recent centuries the world has become increasingly dominated by empirical evidence and theoretic science in developing worldviews. Advances in science have dictated Roman Catholic doctrine such as the acceptance of Darwinian evolution and Big Bang cosmology. Albert Einstein created an indelible impact on the relationship between science and religion. The question is whether or not his work was deleterious for church doctrine or whether it was compatible with, or even advanced, church dogma. It's my contention that Einstein revived the relationship between science and theology and did not create a bifurcation between the two. Despite his personal religious beliefs, his work has helped to reinforce the harmonious conjunction of science with religion, which cannot be ignored by succeeding scientists and theologians.

Andrews, Max L E

2012-01-01

237

Albert Einstein - a Pious Atheist  

E-print Network

We consider Einstein's attitude with regard to religion both from sociological and epistemological points of view. An attempt to put it into a wider socio-historical perspective has been made, with the emphasis on his ethnic and religious background. The great scientist was neither anatheist nor a believer in the orthodox sense and the closest labels one might apply would be pantheism/cosmism (ontological view) and agnosticism (epistemological view). His ideas on the divine could be considered as a continuation of a line that can be traced back to Philo of Alexandria, who himself followed the Greek Stoics and Neoplatonists and especially Baruch Spinoza. Einstein's scientific (or rational) and religious (or intuitive) thinking was deeply rooted in the Hellenic culture.

V. Djokovic; P. Grujic

2007-06-29

238

Gravitational Lensing - Einstein's Unfinished Symphony  

E-print Network

Gravitational lensing - the deflection of light rays by gravitating matter - has become a major tool in the armoury of the modern cosmologist. Proposed nearly a hundred years ago as a key feature of Einstein's theory of General Relativity, we trace the historical development since its verification at a solar eclipse in 1919. Einstein was apparently cautious about its practical utility and the subject lay dormant observationally for nearly 60 years. Nonetheless there has been rapid progress over the past twenty years. The technique allows astronomers to chart the distribution of dark matter on large and small scales thereby testing predictions of the standard cosmological model which assumes dark matter comprises a massive weakly-interacting particle. By measuring distances and tracing the growth of dark matter structure over cosmic time, gravitational lensing also holds great promise in determining whether the dark energy, postulated to explain the accelerated cosmic expansion, is a vacuum energy density or a...

Treu, Tommaso

2014-01-01

239

Parameterized Beyond-Einstein Growth  

SciTech Connect

A single parameter, the gravitational growth index gamma, succeeds in characterizing the growth of density perturbations in the linear regime separately from the effects of the cosmic expansion. The parameter is restricted to a very narrow range for models of dark energy obeying the laws of general relativity but can take on distinctly different values in models of beyond-Einstein gravity. Motivated by the parameterized post-Newtonian (PPN) formalism for testing gravity, we analytically derive and extend the gravitational growth index, or Minimal Modified Gravity, approach to parameterizing beyond-Einstein cosmology. The analytic formalism demonstrates how to apply the growth index parameter to early dark energy, time-varying gravity, DGP braneworld gravity, and some scalar-tensor gravity.

Linder, Eric; Linder, Eric V.; Cahn, Robert N.

2007-09-17

240

Science at the Time-scale of the Electron  

NASA Astrophysics Data System (ADS)

Replace this text with your abstract Ever since the invention of the laser 50 years ago and its application in nonlinear optics, scientists have been striving to extend coherent laser beams into the x-ray region of the spectrum. Very recently however, the prospects for tabletop coherent sources, with attosecond pulse durations, at very short wavelengths even in the hard x-ray region of the spectrum at wavelengths < 1nm, have brightened considerably. These advances are possible by taking nonlinear optics techniques to an extreme, and are the direct result of a new ability to manipulate electrons on the fastest, attosecond, time-scales of our natural world. My talk will discuss new experimental data that demonstrates high harmonic generation of laser-like, fully coherent, 10 attosecond duration, soft x-ray beams at photon energies around 0.5keV. Several applications will also be discussed, including making a movie of how electron orbitals in a molecule change shape as a molecule breaks apart, following how fast a magnetic material can flip orientation, understanding how fast heat flows in a nanocircuit, or building a microscope without lenses. [4pt] [1] T. Popmintchev et al., ``Phase matched upconversion of coherent ultrafast laser light into the soft and hard x-ray regions of the spectrum'', PNAS 106, 10516 (2009). [0pt] [2] C. LaOVorakiat et al., ``Ultrafast Soft X-Ray Magneto-Optics at the M-edge Using a Tabletop High-Harmonic Source'', Physical Review Letters 103, 257402 (2009). [0pt] [3] M. Siemens et al. ``Measurement of quasi-ballistic heat transport across nanoscale interfaces using ultrafast coherent soft x-ray beams'', Nature Materials 9, 26 (2010). [0pt] [4] K. Raines et al., ``Three-dimensional structure determination from a single view,'' Nature 463, 214 (2010). [0pt] [5] W. Li et al., ``Time-resolved Probing of Dynamics in Polyatomic Molecules using High Harmonic Generation'', Science 322, 1207 (2008).

Murnane, Margaret

2010-03-01

241

Time-scale modelling of the invasive species Robinia pseudoacacia  

NASA Astrophysics Data System (ADS)

Our contribution is part of the TransEcoNet project (Transnational Ecological Networks in Central Europe) that aims to investigate transboundary ecological networks across Central Europe. An objective of this project is to contribute towards awareness rising on the value and role of ecological networks. This poster presents the activities that are carried out in Pomurje region, Slovenia as our case study area. Pomurje region borders with Austria in the north, to Hungary in the east, and to Croatia in the south. We are investigating the spread of the invasive species Robinia pseudacacia and the underlying causes, and assess landscape scale ecological dynamics (e.g. Mura River floodplains) in ecological networks. The study comprises investigation and mapping of the R. pseudacacia spread with time-series analysis to understand its spatial dynamics. The preliminary studies show that the R. pseudacacia had the most expanded in the region since 1980s. Some of the surfaces were cut and converted back to fields. This reflects the socioeconomic situation in the region. The further study will include statistic, GIS (geographical information systems) and remote sensing techniques. We will apply various character data: satellite imagery, IR-orthophotos, digital elevation models, including LIDAR, contemporary and historical maps, and other spatial/non-spatial data sources. The outputs will include reconstruction of R. pseudacacia-dynamics in the recent decade, modelling the distribution of R. pseudacacia in relation to abiotic environmental factors and land use, and modelling (prediction) the expected distribution of R. pseudacacia in case of climate and land use change. Keywords: invasive species, Robinia pseudacacia, spatial analysis, time-scale analysis, remote sensing, land use change, climate change

Tomaž, Podobnikar; Andraž, Ä.?Arni; Imelda, Somodi

2010-05-01

242

Release timescales of solar energetic particles in the low corona  

NASA Astrophysics Data System (ADS)

Aims: We present a systematic study of the timing and duration of the release processes of near-relativistic (NR; >50 keV) electrons in the low corona. Methods: We analyze seven well-observed events using in situ measurements by both the ACE and Wind spacecraft and context electromagnetic observations in soft X-rays, radio, hard X-rays and white light. We make use of velocity dispersion analysis to estimate the release time of the first arriving electrons and compare with the results obtained by using a simulation-based approach, taking interplanetary transport effects into account to unfold the NR electron release time history from in situ measurements. Results: The NR electrons observed in interplanetary space appear to be released during either short (<30 min) or long (>2 h) periods. The observation of NR electron events showing beamed pitch-angle distributions (PADs) during several hours is the clearest observational signature of sustained release in the corona. On the other hand, the in situ observation of PADs isotropizing in less than a couple of hours is a clear signature of a prompt release of electrons in the low corona. Short release episodes appear to originate in solar flares, in coincidence with the timing of the observed type III radio bursts. Magnetic connectivity plays an important role. Only type III radio bursts reaching the local plasma line measured at 1 AU are found to be related with an associated release episode in the low corona. Other type III bursts may also have a release of NR electrons associated with them, but these electrons do not reach L1. Long release episodes appear associated with signatures of long acceleration processes in the low corona (long decay of the soft X-ray emission, type IV radio bursts, and time-extended microwave emission). Type II radio bursts are reported for most of the events and do not provide a clear discrimination between short and long release timescales.

Agueda, N.; Klein, K.-L.; Vilmer, N.; Rodríguez-Gasén, R.; Malandraki, O. E.; Papaioannou, A.; Subirà, M.; Sanahuja, B.; Valtonen, E.; Dröge, W.; Nindos, A.; Heber, B.; Braune, S.; Usoskin, I. G.; Heynderickx, D.; Talew, E.; Vainio, R.

2014-10-01

243

A statistical relation between the X-ray spectral index and Eddington ratio of active galactic nuclei in deep surveys  

NASA Astrophysics Data System (ADS)

We present an investigation into how well the properties of the accretion flow on to a supermassive black hole may be coupled to those of the overlying hot corona. To do so, we specifically measure the characteristic spectral index, ?, of a power-law energy distribution, over an energy range of 2-10 keV, for X-ray selected, broad-lined radio-quiet active galactic nuclei (AGN) up to z ˜ 2 in Cosmic Evolution Survey (COSMOS) and Extended Chandra Deep Field South (E-CDF-S). We test the previously reported dependence between ? and black hole mass, full width at half-maximum (FWHM) and Eddington ratio using a sample of AGN covering a broad range in these parameters based on both the Mg II and H? emission lines with the later afforded by recent near-infrared spectroscopic observations using Subaru/Fibre Multi Object Spectrograph. We calculate the Eddington ratios, ?Edd, for sources where a bolometric luminosity (LBol) has been presented in the literature, based on spectral energy distribution fitting, or, for sources where these data do not exist, we calculate LBol using a bolometric correction to the X-ray luminosity, derived from a relationship between the bolometric correction and LX/L3000. From a sample of 69 X-ray bright sources (>250 counts), where ? can be measured with greatest precision, with an estimate of LBol, we find a statistically significant correlation between ? and ?Edd, which is highly significant with a chance probability of 6.59× 10-8. A statistically significant correlation between ? and the FWHM of the optical lines is confirmed, but at lower significance than with ?Edd indicating that ?Edd is the key parameter driving conditions in the corona. Linear regression analysis reveals that ? = (0.32 ± 0.05) log10?Edd + (2.27 ± 0.06) and ? = (-0.69 ± 0.11) log10(FWHM/km s-1) + (4.44 ± 0.42). Our results on ?-?Edd are in very good agreement with previous results. While the ?-?Edd relationship means that X-ray spectroscopy may be used to estimate black hole accretion rate, considerable dispersion in the correlation does not make this viable for single sources, however could be valuable for large X-ray spectral samples, such as those to be produced by eROSITA.

Brightman, M.; Silverman, J. D.; Mainieri, V.; Ueda, Y.; Schramm, M.; Matsuoka, K.; Nagao, T.; Steinhardt, C.; Kartaltepe, J.; Sanders, D. B.; Treister, E.; Shemmer, O.; Brandt, W. N.; Brusa, M.; Comastri, A.; Ho, L. C.; Lanzuisi, G.; Lusso, E.; Nandra, K.; Salvato, M.; Zamorani, G.; Akiyama, M.; Alexander, D. M.; Bongiorno, A.; Capak, P.; Civano, F.; Del Moro, A.; Doi, A.; Elvis, M.; Hasinger, G.; Laird, E. S.; Masters, D.; Mignoli, M.; Ohta, K.; Schawinski, K.; Taniguchi, Y.

2013-08-01

244

MhringerWeg Albert-Einstein-Allee  

E-print Network

N MähringerWeg Oberer Eselsberg Oberer Eselsberg Albert-Einstein-Allee Helmholtzstr. James-Franck-Ring Staudingerstr. Hans- Krebs- Weg Robert-Koch-Str. Albert- Einstein- Allee W ilhelm -Runge-Str. Berliner Ring Albert- Einstein- Allee Lise- Meitner -Str. Lise-Meitner-Str. 2/1 148 11 8 8 11 5 8/1 8 10 14 12 22 20 18

Pfeifer, Holger

245

Timescales in creep and yielding of attractive gels.  

PubMed

The stress-induced yielding scenario of colloidal gels is investigated under rough boundary conditions by means of rheometry coupled with local velocity measurements. Under an applied shear stress ?, the fluidization of gels made of attractive carbon black particles dispersed in a mineral oil is shown to involve a previously unreported shear rate response ? dot above(t) characterized by two well-defined and separated timescales ?c and ?f. First ? dot above decreases as a weak power law strongly reminiscent of the primary creep observed in numerous crystalline and amorphous solids, coined the "Andrade creep". We show that the bulk deformation remains homogeneous at the micron scale, which demonstrates that whether plastic events take place or whether any shear transformation zone exists, such phenomena occur at a smaller scale. As a key result of this paper, the duration ?c of this creep regime decreases as a power law of the viscous stress, defined as the difference between the applied stress and the yield stress ?c, i.e. ?c ? (? - ?c)(-?), with ? = 2-3 depending on the gel concentration. The end of this first regime is marked by a jump of the shear rate by several orders of magnitude, while the gel slowly slides as a solid block experiencing strong wall slip at both walls, despite rough boundary conditions. Finally, a second sudden increase of the shear rate is concomitant with the full fluidization of the material which ends up being homogeneously sheared. The corresponding fluidization time ?f robustly follows an exponential decay with the applied shear stress, i.e. ?f = ?0?exp(-?/?0), as already reported for smooth boundary conditions. Varying the gel concentration C in a systematic fashion shows that the parameter ?0 and the yield stress ?c exhibit similar power-law dependences with C. Finally, we highlight a few features that are common to attractive colloidal gels and to solid materials by discussing our results in the framework of theoretical approaches of solid rupture (kinetic, fiber bundle, and transient network models). PMID:24651869

Grenard, Vincent; Divoux, Thibaut; Taberlet, Nicolas; Manneville, Sébastien

2014-03-14

246

ASYMPTOTIC SELF-SIMILAR SOLUTIONS WITH A CHARACTERISTIC TIMESCALE  

SciTech Connect

For a wide variety of initial and boundary conditions, adiabatic one-dimensional flows of an ideal gas approach self-similar behavior when the characteristic length scale over which the flow takes place, R, diverges or tends to zero. It is commonly assumed that self-similarity is approached since in the R {yields} {infinity}(0) limit the flow becomes independent of any characteristic length or timescales. In this case, the flow fields f(r, t) must be of the form f(r,t)=t{sup {alpha}}{sub f}F(r/R) with R {proportional_to} ({+-}t){sup {alpha}}. We show that requiring the asymptotic flow to be independent only of characteristic length scales implies a more general form of self-similar solutions, f(r,t)=R{sup {delta}}{sub f}F(r/R) with R-dot {proportional_to}R{sup {delta}}, which includes the exponential ({delta} = 1) solutions, R {proportional_to} e {sup t/{tau}}. We demonstrate that the latter, less restrictive, requirement is the physically relevant one by showing that the asymptotic behavior of accelerating blast waves, driven by the release of energy at the center of a cold gas sphere of initial density {rho} {proportional_to} r {sup -{omega}}, changes its character at large {omega}: the flow is described by 0 {<=} {delta} < 1, R {proportional_to} t {sup 1/(1-{delta})}, solutions for {omega} < {omega}{sub c}, by {delta}>1 solutions with R {proportional_to} (-t){sup 1/({delta}-1)} diverging at finite time (t = 0) for {omega}>{omega}{sub c}, and by exponential solutions for {omega} = {omega}{sub c} ({omega}{sub c} depends on the adiabatic index of the gas, {omega}{sub c} {approx} 8 for 4/3 < {gamma} < 5/3). The properties of the new solutions obtained here for {omega} {>=} {omega}{sub c} are analyzed, and self-similar solutions describing the t>0 behavior for {omega}>{omega}{sub c} are also derived.

Waxman, Eli [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel); Shvarts, Dov [Department of Physics, Nuclear Research Center Negev, P.O. Box 9001, Beer-Sheva 84015 (Israel)

2010-10-01

247

Computing the Delta-Eddington Approximation for Solar Radiation With Hardware Accelerators: Performance and Programmability on GPUs, FPGAs, and Microprocessors.  

NASA Astrophysics Data System (ADS)

The raddedmx routine is a computationally expensive portion of the short-wave radiation calculations in the NCAR Community Climate System Model (CCSM). The routine calculates the Delta-Eddington Approximation on columns of independent data, and executes a high number of floating point operations per byte of data accessed, making it a good candidate for hardware acceleration. We compare several implementation strategies for the raddedmx computation on two hardware acceleration platforms, Graphics Processing Units (GPUs) and Field Programmable Gate Arrays (FPGAs), and analyze the computational speedups that can be realized in addition to programmability and the software engineering effort required on the different platforms. Implementations are found that are able to realize computational speedups in excess of 400x, and overall speedups in excess of 30x including data transfer overhead, versus the microprocessor of the host system. We discuss limitations of the various platforms and implementations, additional features that could improve performance, and the possibility of extending the work to accelerate other portions of the CCSM.

Kelly, R. C.; Garcia, J.

2008-12-01

248

Relationship between X-ray spectral index and X-ray Eddington ratio for Mrk 335 and Ark 564  

E-print Network

We present a comprehensive flux resolved spectral analysis of the bright Narrow line Seyfert I AGNs, Mrk~335 and Ark~564 using observations by XMM-Newton satellite. The mean and the flux resolved spectra are fitted by an empirical model consisting of two Comptonization components, one for the low energy soft excess and the other for the high energy power-law. A broad Iron line and a couple of low energies edges are required to explain the spectra. For Mrk~335, the 0.3 - 10 keV luminosity relative to the Eddington value, L{$_{X}$}/L$_{Edd}$, varied from 0.002 to 0.06. The index variation can be empirically described as $\\Gamma$ = 0.6 log$_{10}$ L{$_{X}$}/L$_{Edd}$ + 3.0 for $0.005 < L{_{X}}/L_{Edd} < 0.04$. At $ L_{{X}}/L_{Edd} \\sim 0.04$ the spectral index changes and then continues to follow $\\Gamma$ = 0.6 log$_{10}$ L$_{{X}}$/L$_{Edd}$ + 2.7, i.e. on a parallel track. We confirm that the result is independent of the specific spectral model used by fitting the data in the 3 - 10 keV band by only a powe...

Sarma, R; Misra, R; Dewangan, G; Pathak, A; Sarma, J K

2015-01-01

249

The relationship between the Eddington limit, the observed upper luminosity limit for massive stars, and the luminous blue variables  

NASA Technical Reports Server (NTRS)

The observed upper luminosity limits in the Galaxy and the LMC are compared with the Eddington limit as estimated for plane-parallel LTE model atmospheres which include the full effects of metal line opacities in the ultraviolet. It is shown that the Humphreys-Davidson (HD) limit corresponds to the locus of extremely low effective gravities. This result suggests that stars approaching the HD limit will suffer high mass-loss rates because of the reduction of the effective gravity due to radiation pressure. These high mass-loss rates ultimtely lead to the core mass fraction reaching its critical value and the reversal of the stellar evolution tracks. It is shown that radiation pressure, as an agent for producing enhanced mass loss near the HD limit, can in a natural way explain the kink in the HD limit near T(eff) roughly 10,000 K and the upper luminosity limit for yellow and red supergiants. The high mass-loss rates of the luminous blue variables, their location in the HR diagram, and their evolutionary stage are also discussed.

Lamers, Henny J. G. L. M.; Fitzpatrick, Edward L.

1988-01-01

250

SYSTEMATIC UNCERTAINTIES IN THE SPECTROSCOPIC MEASUREMENTS OF NEUTRON-STAR MASSES AND RADII FROM THERMONUCLEAR X-RAY BURSTS. II. EDDINGTON LIMIT  

SciTech Connect

Time-resolved X-ray spectroscopy of thermonuclear bursts observed from low-mass X-ray binaries offer a unique tool to measure neutron-star masses and radii. In this paper, we continue our systematic analysis of all the X-ray bursts observed with Rossi X-ray Timing Explorer from X-ray binaries. We determine the events that show clear evidence for photospheric radius expansion and measure the Eddington limits for these accreting neutron stars using the bolometric fluxes attained at the touchdown moments of each X-ray burst. We employ a Bayesian technique to investigate the degree to which the Eddington limit for each source remains constant between bursts. We find that for sources with a large number of radius expansion bursts, systematic uncertainties are at a 5%-10% level. Moreover, in six sources with only pairs of Eddington-limited bursts, the distribution of fluxes is consistent with a {approx}10% fractional dispersion. This indicates that the spectroscopic measurements of neutron-star masses and radii using thermonuclear X-ray bursts can reach the level of accuracy required to distinguish between different neutron-star equations of state, provided that uncertainties related to the overall flux calibration of X-ray detectors are of comparable magnitude.

Guever, Tolga; Oezel, Feryal; Psaltis, Dimitrios [Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

2012-03-01

251

ALBERT EINSTEIN COLLEGE OF MEDICINE STRATEGIC RESEARCH PLAN UPDATE 2010  

E-print Network

1 ALBERT EINSTEIN COLLEGE OF MEDICINE STRATEGIC RESEARCH PLAN UPDATE 2010 Table community of the Albert Einstein College of Medicine have undertaken a dynamic strategic planning process/Multi-Modal Image Analysis.................10 Clinical Research Enterprise/Einstein-Montefiore Interface

Bukauskas, Feliksas

252

A Cosmic Vision Beyond Einstein  

E-print Network

The acceleration of the cosmic expansion is a fundamental challenge to standard models of particle physics and cosmology. The new physics of dark energy may lie in the nature of gravity, the quantum vacuum, or extra dimensions. I give a brief overview of the puzzles and possibilities of dark energy, and discuss the confrontation of a wide variety of "beyond Einstein" models with the latest data, showing what we currently know and what we must seek to learn. Next generation experiments using a variety of cosmological probes will deeply explore dark energy, dark matter, and gravitation.

Eric V. Linder

2008-10-09

253

Einstein's Theory of Special Relativity  

NSDL National Science Digital Library

This concise tutorial from the Physics Classroom explores a phenomenon thatis integral to Einstein's Theory of Special Relativity. This phenomenonis known as "Relativistic Length Contraction" and occurs when "the length of objects moving at relativistic speeds undergo a contraction along the dimension of motion." This may seem complicated, but the animations included in this tutorial will help you understand this intriguing concept in no time. This a great visual resource to include in class, and is helpful for anyone seeking to understand the concept of relativistic length contraction.

2007-11-14

254

Scientific Potential of Einstein Telescope  

E-print Network

Einstein gravitational-wave Telescope (ET) is a design study funded by the European Commission to explore the technological challenges of and scientific benefits from building a third generation gravitational wave detector. The three-year study, which concluded earlier this year, has formulated the conceptual design of an observatory that can support the implementation of new technology for the next two to three decades. The goal of this talk is to introduce the audience to the overall aims and objectives of the project and to enumerate ET's potential to influence our understanding of fundamental physics, astrophysics and cosmology.

Sathyaprakash, B; Acernese, F; Andersson, P Amaro-Seoane N; Arun, K; Barone, F; Barr, B; Barsuglia, M; Beveridge, M Beker N; Birindelli, S; Bose, S; Bosi, L; Braccini, S; Bradaschia, C; Bulik, T; Calloni, E; Cella, G; Mottin, E Chassande; Chelkowski, S; Chincarini, A; Clark, J; Coccia, E; Colacino, C; Colas, J; Cumming, A; Cunningham, L; Cuoco, E; Danilishin, S; Danzmann, K; Salvo, R De; Dent, T; Rosa, R De; Fiore, L Di; Virgilio, A Di; Doets, M; Fafone, V; Falferi, P; Flaminio, R; Franc, J; Frasconi, F; Freise, A; Friedrich, D; Fulda, P; Gair, J; Gemme, G; Genin, E; Gennai, A; Giazotto, A; Glampedakis, K; Gräf, C; Granata, M; Grote, H; Guidi, G; Gurkovsky, A; Hammond, G; Hannam, M; Harms, J; Heinert, D; Hendry, M; Heng, I; Hennes, E; Hild, S; Hough, J; Husa, S; Huttner, S; Jones, G; Khalili, F; Kokeyama, K; Kokkotas, K; Krishnan, B; Li, T G F; Lorenzini, M; Lück, H; Majorana, E; Mandel, I; Mandic, V; Mantovani, M; Martin, I; Michel, C; Minenkov, Y; Morgado, N; Mosca, S; Mours, B; Müller--Ebhardt, H; Murray, P; Nawrodt, R; Nelson, J; Oshaughnessy, R; Ott, C D; Palomba, C; Paoli, A; Parguez, G; Pasqualetti, A; Passaquieti, R; Passuello, D; Pinard, L; Plastino, W; Poggiani, R; Popolizio, P; Prato, M; Punturo, M; Puppo, P; Rabeling, D; Racz, I; Rapagnani, P; Read, J; Regimbau, T; Rehbein, H; Reid, S; Rezzolla, L; Ricci, F; Richard, F; Rocchi, A; Rowan, S; Rüdiger, A; Santamaría, L; Sassolas, B; Schnabe, R; Schwarz, C; Seidel, P; Sintes, A; Somiya, K; Speirits, F; Strain, K; Strigin, S; Sutton, P; Tarabrin, S; Thüring, A; Brand, J van den; Veggel, M van; Broeck, C van den; Vecchio, A; Veitch, J; Vetrano, F; Vicere, A; Vyatchanin, S; Willke, B; Woan, G; Yamamoto, K

2011-01-01

255

Scientific Potential of Einstein Telescope  

E-print Network

Einstein gravitational-wave Telescope (ET) is a design study funded by the European Commission to explore the technological challenges of and scientific benefits from building a third generation gravitational wave detector. The three-year study, which concluded earlier this year, has formulated the conceptual design of an observatory that can support the implementation of new technology for the next two to three decades. The goal of this talk is to introduce the audience to the overall aims and objectives of the project and to enumerate ET's potential to influence our understanding of fundamental physics, astrophysics and cosmology.

B. Sathyaprakash; M. Abernathy; F. Acernese; P. Amaro-Seoane; N. Andersson; K. Arun; F. Barone; B. Barr; M. Barsuglia; M. Beker; N. Beveridge; S. Birindelli; S. Bose; L. Bosi; S. Braccini; C. Bradaschia; T. Bulik; E. Calloni; G. Cella; E. Chassande-Mottin; S. Chelkowski; A. Chincarini; J. Clark; E. Coccia; C. Colacino; J. Colas; A. Cumming; L. Cunningham; E. Cuoco; S. Danilishin; K. Danzmann; R. De. Salvo; T. Dent; R. De. Rosa; L. Di. Fiore; A. Di. Virgilio; M. Doets; V. Fafone; P. Falferi; R. Flaminio; J. Franc; F. Frasconi; A. Freise; D. Friedrich; P. Fulda; J. Gair; G. Gemme; E. Genin; A. Gennai; A. Giazotto; K. Glampedakis; C. Gräf; M. Granata; H. Grote; G. Guidi; A. Gurkovsky; G. Hammond; M. Hannam; J. Harms; D. Heinert; M. Hendry; I. Heng; E. Hennes; S. Hild; J. Hough; S. Husa; S. Huttner; G. Jones; F. Khalili; K. Kokeyama; K. Kokkotas; B. Krishnan; T. G. F. Li; M. Lorenzini; H. Lück; E. Majorana; I. Mandel; V. Mandic; M. Mantovani; I. Martin; C. Michel; Y. Minenkov; N. Morgado; S. Mosca; B. Mours; H. Müller-Ebhardt; P. Murray; R. Nawrodt; J. Nelson; R. Oshaughnessy; C. D. Ott; C. Palomba; A. Paoli; G. Parguez; A. Pasqualetti; R. Passaquieti; D. Passuello; L. Pinard; W. Plastino; R. Poggiani; P. Popolizio; M. Prato; M. Punturo; P. Puppo; D. Rabeling; I. Racz; P. Rapagnani; J. Read; T. Regimbau; H. Rehbein; S. Reid; L. Rezzolla; F. Ricci; F. Richard; A. Rocchi; S. Rowan; A. Rüdiger; L. Santamaria; B. Sassolas; R. Schnabel; C. Schwarz; P. Seidel; A. Sintes; K. Somiya; F. Speirits; K. Strain; S. Strigin; P. Sutton; S. Tarabrin; A. Thüring; J. van den Brand; M van Veggel; C. Van Den Broeck; A. Vecchio; J. Veitch; F. Vetrano; A. Vicere; S. Vyatchanin; B. Willke; G. Woan; K. Yamamoto

2012-06-02

256

Albert Einstein:. Opportunity and Perception  

NASA Astrophysics Data System (ADS)

The year 1905 has been called Albert Einstein's "Annus Mirabilis." It was during that year that he caused revolutionary changes in man's primordial concepts about the physical world: space, time, energy, light and matter. How could a 26-year-old clerk, previously unknown, cause such profound conceptual changes, and thereby open the door to the era of modern scientific technological world? No one, of course, can answer that question. But one can, perhaps, analyze some factors that were essential to his stepping into such a historic role...

Yang, Chen Ning

2013-05-01

257

An extraterrestrial 3 He-based timescale for the PaleoceneEocene  

E-print Network

An extraterrestrial 3 He-based timescale for the Paleocene­Eocene thermal maximum (PETM) from. The extraterrestrial 3 He, 3 HeET, concentrations replicate trends observed at ODP Site 690 by Farley and Eltgroth

Zachos, James

258

Non-convergence of the critical cooling timescale for fragmentation of self-gravitating discs  

NASA Astrophysics Data System (ADS)

We carry out a resolution study on the fragmentation boundary of self-gravitating discs. We perform three-dimensional Smoothed Particle Hydrodynamics (SPH) simulations of discs to determine whether the critical value of the cooling timescale in units of the orbital timescale, ?crit, converges with increasing resolution. Using particle numbers ranging from 31,250 to 16 million (the highest resolution simulations to date) we do not find convergence. Instead, fragmentation occurs for longer cooling timescales as the resolution is increased. These results certainly suggest that ?crit is larger than previously thought. However, the absence of convergence also questions whether or not a critical value exists. In light of these results, we caution against using cooling timescale or gravitational stress arguments to deduce whether gravitational instability may or may not have been the formation mechanism for observed planetary systems.

Meru, Farzana; Bate, Matthew R.

2011-11-01

259

Determining timescales of natural carbonation of peridotite in the Samail Ophiolite, Sultanate of Oman  

E-print Network

Determining timescales of the formation and preservation of carbonate alteration products in mantle peridotite is important in order to better understand the role of this potentially important sink in the global carbon ...

Mervine, Evelyn Martinique

2012-01-01

260

VARIABILITY OF GAMMA-RAY EMISSION FROM BLAZARS ON BLACK HOLE TIMESCALES  

SciTech Connect

We investigate the variability properties of blazars in the GeV band using data from the Fermi/Large Area Telescope (LAT) telescope. We find that blazars exhibit variability down to the minimum timescale resolvable by Fermi; this variability is a function of the peak photon count rate in the LAT. This implies that the real minimum variability timescales for the majority of blazars are typically shorter than those resolvable by the LAT. We find that for several blazars these minimum variability timescales reach those associated with the blazar central engine, the supermassive black hole. At the same time, none of the blazars exhibits variability on a timescale shorter than the black hole horizon light-crossing time and/or the period of rotation around the last stable circular orbit. Based on this fact, we argue that the timing properties of the {gamma}-ray signal could be determined by the processes in the direct vicinity of the supermassive black hole.

Vovk, Ie.; Neronov, A. [ISDC Data Centre for Astrophysics, Ch. d'Ecogia 16, CH-1290, Versoix (Switzerland)

2013-04-20

261

The Albert Einstein College of Medicine of Yeshiva University  

E-print Network

The Albert Einstein College of Medicine of Yeshiva University EMERGENCY PROCEDURES MANUAL Prepared Supporting Services Revised ­ January, 2012 #12;ALBERT EINSTEIN COLLEGE of MEDICINE of YESHIVA UNIVERSITY

Yates, Andrew

262

The Albert Einstein College of Medicine of Yeshiva University  

E-print Network

The Albert Einstein College of Medicine of Yeshiva University EMERGENCY PROCEDURES MANUAL Prepared Resources Security Revised ­ May, 2013 #12;ALBERT EINSTEIN COLLEGE of MEDICINE of YESHIVA UNIVERSITY

Emmons, Scott

263

Laplace operators on Sasaki-Einstein manifolds  

NASA Astrophysics Data System (ADS)

We decompose the de Rham Laplacian on Sasaki-Einstein manifolds as a sum over mostly positive definite terms. An immediate consequence are lower bounds on its spectrum. These bounds constitute a supergravity equivalent of the unitarity bounds in dual superconformal field theories. The proof uses a generalisation of Kähler identities to the Sasaki-Einstein case.

Schmude, Johannes

2014-04-01

264

Einstein Product Metrics in Diverse Dimensions  

E-print Network

We use direct products of Einstein Metrics to construct new solutions to Einstein's Equations with cosmological constant. We illustrate the technique with three families of solutions having the geometries Kerr/de Sitter X de Sitter, Kerr/anti-de Sitter X anti-de Sitter and Kerr X Kerr.

K. R. Koehler

2006-01-27

265

Experimental studies of Bose-Einstein condensation  

E-print Network

Experimental studies of Bose-Einstein condensation Dallin S. Durfee and Wolfgang Ketterle-Einstein condensation in a dilute gas of sodium atoms. These include studies of static and dynamic behavior of the condensate, and of its coherence properties. Ã?1998 Optical Society of America OCIS codes: (020.0020) Atomic

Hart, Gus

266

What Einstein Can Teach Us about Education  

ERIC Educational Resources Information Center

People are more likely to associate Einstein with complex scientific theories and mathematical calculations than with education theory. In fact, Einstein's own experiences of schooling and his reflections on the meaning of life and the significance of education are profound and oddly relevant to the situation that pertains in England today. It is…

Hayes, Denis

2007-01-01

267

Einstein as a Missionary of Science  

ERIC Educational Resources Information Center

The paper reviews Einstein's engagement as a mediator and popularizer of science. It discusses the formative role of popular scientific literature for the young Einstein, showing that not only his broad scientific outlook but also his internationalist political views were shaped by these readings. Then, on the basis of recent detailed…

Renn, Jürgen

2013-01-01

268

Books on Einstein--Collectors' Delight  

ERIC Educational Resources Information Center

A survey of thirteen books on Einstein is presented. Its gives an idea on how much is written about the man and how frequent are the publications. The year 2005 saw the most publications. It is the centenary for the Miraculous Year. Interestingly some books can just sustain their readers' interest with just words. Einstein comes alive with the…

Khoon, Koh Aik; Jalal, Azman; Abd-Shukor, R.; Yatim, Baharudin; Talib, Ibrahim Abu; Daud, Abdul Razak; Samat, Supian

2009-01-01

269

Einstein's Revolutionary Light-Quantum Hypothesis  

Microsoft Academic Search

The paper in which Albert Einstein proposed his light-quantum hypothesis was the only one of his great papers of 1905 that he himself termed ``revolutionary.'' Contrary to widespread belief, Einstein did not propose his light-quantum hypothesis ``to explain the photoelectric effect.'' Instead, he based his argument for light quanta on the statistical interpretation of the second law of thermodynamics, with

Roger H. Stuewer

2005-01-01

270

LOWDIMENSIONAL HOMOGENEOUS EINSTEIN MANIFOLDS CHRISTOPH B  

E-print Network

LOW­DIMENSIONAL HOMOGENEOUS EINSTEIN MANIFOLDS CHRISTOPH B Ë? OHM AND MEGAN M. KERR A closed) of dimension n = 2 or 3 has constant sectional curvature, a space form. Simply connected compact homogeneous Luce Foundation. 1 #12; 2 CHRISTOPH B Ë? OHM AND MEGAN M. KERR Einstein metric [Wo]. The isotropy

Kerr, Megan M.

271

Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic  

NASA Astrophysics Data System (ADS)

Recently reported radioisotopic dates and magnetic anomaly spacings have made it evident that modification is required for the age calibrations for the geomagnetic polarity timescale of Cande and Kent (1992) at the Cretaceous/Paleogene boundary and in the Pliocene. An adjusted geomagnetic reversal chronology for the Late Cretaceous and Cenozoic is presented that is consistent with astrochronology in the Pleistocene and Pliocene and with a new timescale for the Mesozoic.

Cande, S. C.; Kent, D. V.

1995-04-01

272

An improved whitecap timescale for sea spray aerosol production flux modeling using the discrete whitecap method  

NASA Astrophysics Data System (ADS)

The discrete whitecap method (DWM) to model the sea spray aerosol (SSA) production flux explicitly requires a whitecap timescale, which up to now has only considered a whitecap decay timescale, ?decay. A reevaluation of the DWM suggests that the whitecap timescale should account for the total whitecap lifetime (?wcap), which consists of both the formation timescale (?form) and the decay timescale (timescale definitions are given in the text). Here values of ?form for 552 oceanic whitecaps measured at the Martha's Vineyard Coastal Observatory on the east coast of the USA are presented, and added to the corresponding values of ?decay to form 552 whitecap timescales. For the majority of whitecaps, ?form makes up about 20-25% of ?wcap, but this can be as large as 70% depending on the value of ?decay. Furthermore, an area-weighted mean whitecap timescale for use in the DWM (?DWM) is defined that encompasses the variable nature of individual whitecap lifetimes within a given time period, and is calculated to be 5.3 s for this entire data set. This value is combined with previously published whitecap coverage parameterizations and estimates of SSA particle production per whitecap area to form a size-resolved SSA production flux parameterization (dF(r80)/dlog10r80). This parameterization yields integrated sea-salt mass fluxes that are largely within the range of uncertainty of recent measurements over the size range 0.029 µm < r80 < 0.580 µm. Physical factors controlling whitecap lifetime such as bubble plume lifetime and surfactant stabilization are discussed in the context of SSA production from whitecaps.

Callaghan, Adrian H.

2013-09-01

273

Finding Pulsars with Einstein@Home  

NASA Astrophysics Data System (ADS)

The Einstein@Home project is a global distributed computing project and aggregates the computer power of hundreds of thousands of volunteers from 192 countries to "mine" large data sets. Its long-term goal is the detection of continuous gravitational waves in data from the LIGO interferometric gravitational wave detectors. Since March 2009 about a third of Einstein@Home's computation cycles is also used to search for tight binary pulsars in PALFA radio data from the Arecibo observatory. In July 2010, two new pulsars were found by Einstein@Home, J2007+2722 and J1952+26, the latter in a binary system with 9.4 hours orbital period. Here, we present an overview of the status of the Einstein@Home project and describe its search for radio pulsars in binaries with periods larger than 11 minutes. Further, we briefly review Einstein@Home's pulsar discoveries.

Knispel, Benjamin; Allen, B.; Cordes, J.; Deneva, J.; Anderson, D.; Aulbert, C.; Bhat, N. D. R.; Bock, O.; Bogdanov, S.; Brazier, A.; Camilo, F.; Champion, D. J.; Chatterjee, S.; Crawford, F.; Demorest, P. B.; Fehrmann, H.; Freire, P. C. C.; Gonzalez, M. E.; Hammer, D.; Hessels, J. W. T.; Jenet, F. A.; Kasian, L.; Kaspi, V. M.; Kramer, M.; Lazarus, P.; van Leeuwen, J.; Lorimer, D. R.; Lyne, A. G.; Machenschalk, B.; McLaughlin, M. A.; Messenger, C.; Nice, D. J.; Papa, M. A.; Pletsch, H. J.; Prix, R.; Ransom, S. M.; Siemens, X.; Stairs, I. H.; Stappers, B. W.; Stovall, K.; Venkataraman, A.; Desvignes, G.

2011-01-01

274

Albert Einstein's Magic Mountain: An Aarau Education  

NASA Astrophysics Data System (ADS)

For economic reasons, the electrotechnical factory J. Einstein & Cie. (co-owned by Albert Einstein's father Hermann) had to be closed in the summer of 1894. While Albert's parents emigrated to Italy to build a new existence, he remained in Munich to complete his studies at the Gymnasium. Left behind, however, he had a difficult time with what he considered the rigid educational practices at the Munich Luitpold-Gymnasium and quit without a diploma. The present article discusses Einstein's richly winding path to the Aargau Cantonal School (Switzerland), especially its history and educational philosophy during the time of his stay in Aarau. There, Einstein met some outstanding teachers, who could serve him as models of scholars and human beings. In spite of Einstein's distinct independence of mind, these personalities may well have had a significant influence on the alignment of his inner compass.

Hunziker, Herbert

2015-01-01

275

Astrophysical Observations: Lensing and Eclipsing Einstein's Theories  

E-print Network

Albert Einstein postulated the equivalence of energy and mass, developed the theory of special relativity, explained the photoelectric effect, and described Brownian motion in five papers, all published in 1905, 100 years ago. With these papers, Einstein provided the framework for understanding modern astrophysical phenomena. Conversely, astrophysical observations provide one of the most effective means for testing Einstein's theories. Here, I review astrophysical advances precipitated by Einstein's insights, including gravitational redshifts, gravitational lensing, gravitational waves, the Lense-Thirring effect, and modern cosmology. A complete understanding of cosmology, from the earliest moments to the ultimate fate of the universe, will require developments in physics beyond Einstein, to a unified theory of gravity and quantum physics.

Charles L. Bennett

2005-03-15

276

Spatial and seasonal variability of the air-sea equilibration timescale of carbon dioxide  

NASA Astrophysics Data System (ADS)

The exchange of carbon dioxide between the ocean and the atmosphere tends to bring waters within the mixed layer toward equilibrium by reducing the partial pressure gradient across the air-water interface. However, the equilibration process is not instantaneous; in general, there is a lag between forcing and response. The timescale of air-sea equilibration depends on several factors involving the depth of the mixed layer, wind speed, and carbonate chemistry. We use a suite of observational data sets to generate climatological and seasonal composite maps of the air-sea equilibration timescale. The relaxation timescale exhibits considerable spatial and seasonal variations that are largely set by changes in mixed layer depth and wind speed. The net effect is dominated by the mixed layer depth; the gas exchange velocity and carbonate chemistry parameters only provide partial compensation. Broadly speaking, the adjustment timescale tends to increase with latitude. We compare the observationally derived air-sea gas exchange timescale with a model-derived surface residence time and a data-derived horizontal transport timescale, which allows us to define two nondimensional metrics of equilibration efficiency. These parameters highlight the tropics, subtropics, and northern North Atlantic as regions of inefficient air-sea equilibration where carbon anomalies are relatively likely to persist. The efficiency parameters presented here can serve as simple tools for understanding the large-scale persistence of air-sea disequilibrium of CO2 in both observations and models.

Jones, Daniel C.; Ito, Takamitsu; Takano, Yohei; Hsu, Wei-Ching

2014-11-01

277

COMPARISON OF KEPLER PHOTOMETRIC VARIABILITY WITH THE SUN ON DIFFERENT TIMESCALES  

SciTech Connect

We utilize Kepler data to study the precision differential photometric variability of solar-type and cooler stars at different timescales, ranging from half an hour to three months. We define a diagnostic that characterizes the median differential intensity change between data bins of a given timescale. We apply the same diagnostics to Solar and Heliospheric Observatory data that has been rendered comparable to Kepler. The Sun exhibits similar photometric variability on all timescales as comparable solar-type stars in the Kepler field. The previously defined photometric ''range'' serves as our activity proxy (driven by starspot coverage). We revisit the fraction of comparable stars in the Kepler field that are more active than the Sun. The exact active fraction depends on what is meant by ''more active than the Sun'' and on the magnitude limit of the sample of stars considered. This active fraction is between a quarter and a third (depending on the timescale). We argue that a reliable result requires timescales of half a day or longer and stars brighter than M{sub Kep} of 14, otherwise non-stellar noise distorts it. We also analyze main sequence stars grouped by temperature from 6500 to 3500 K. As one moves to cooler stars, the active fraction of stars becomes steadily larger (greater than 90% for early M dwarfs). The Sun is a good photometric model at all timescales for those cooler stars that have long-term variability within the span of solar variability.

Basri, Gibor [Astronomy Department, University of California, Hearst Field Annex, Berkeley, CA 94720 (United States); Walkowicz, Lucianne M. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, 4 Ivy Lane, Princeton NJ 08534 (United States); Reiners, Ansgar [Georg-August-University Goettingen, Institute for Astrophysics, Friedrich-Hund-Platz 1, DE D-37077, Goettingen (Germany)

2013-05-20

278

Six-Degree-of-Freedom Trajectory Optimization Utilizing a Two-Timescale Collocation Architecture  

NASA Technical Reports Server (NTRS)

Six-degree-of-freedom (6DOF) trajectory optimization of a reentry vehicle is solved using a two-timescale collocation methodology. This class of 6DOF trajectory problems are characterized by two distinct timescales in their governing equations, where a subset of the states have high-frequency dynamics (the rotational equations of motion) while the remaining states (the translational equations of motion) vary comparatively slowly. With conventional collocation methods, the 6DOF problem size becomes extraordinarily large and difficult to solve. Utilizing the two-timescale collocation architecture, the problem size is reduced significantly. The converged solution shows a realistic landing profile and captures the appropriate high-frequency rotational dynamics. A large reduction in the overall problem size (by 55%) is attained with the two-timescale architecture as compared to the conventional single-timescale collocation method. Consequently, optimum 6DOF trajectory problems can now be solved efficiently using collocation, which was not previously possible for a system with two distinct timescales in the governing states.

Desai, Prasun N.; Conway, Bruce A.

2005-01-01

279

Temperature and timescale dependence of protein dynamics imethanol:water mixtures  

SciTech Connect

Experimental and computer simulation studies have suggested the presence of a transition in the dynamics of hydrated proteins at around 180-220 K. This transition is manifested by nonlinear behavior in the temperature dependence of the average atomic mean-square displacement which increases at high temperature. Here, we present results of a dynamic neutron scattering analysis of the transition for a simple enzyme: xylanase in water : methanol solutions of varying methanol concentrations. In order to investigate motions on different timescales, two different instruments were used: one sensitive to {approx}100 ps timescale motions and the other to {approx}ns timescale motions. The results reveal distinctly different behavior on the two timescales examined. On the shorter timescale the dynamics are dictated by the properties of the surrounding solvent: the temperature of the dynamical transition lowers with increasing methanol concentration closely following the melting behavior of the corresponding water : methanol solution. This contrasts with the longer (ns) timescale results in which the dynamical transition appears at temperatures lower than the corresponding melting point of the cryosolvent. These results are suggested to arise from a collaborative effect between the protein surface and the solvent which lowers the effective melting temperature of the protein hydration layer. Taken together, the results suggest that the protein solvation shell may play a major role in the temperature dependence of protein solution dynamics.

Tournier, Alexander [Cancer Research UK; Smith, Jeremy C [ORNL; Daniel, R. M. [University of Waikato, New Zealand; Finney, J.L. [University College, London

2005-01-01

280

Einstein's Theory Fights off Challengers  

NASA Astrophysics Data System (ADS)

Two new and independent studies have put Einstein's General Theory of Relativity to the test like never before. These results, made using NASA's Chandra X-ray Observatory, show Einstein's theory is still the best game in town. Each team of scientists took advantage of extensive Chandra observations of galaxy clusters, the largest objects in the Universe bound together by gravity. One result undercuts a rival gravity model to General Relativity, while the other shows that Einstein's theory works over a vast range of times and distances across the cosmos. The first finding significantly weakens a competitor to General Relativity known as "f(R) gravity". "If General Relativity were the heavyweight boxing champion, this other theory was hoping to be the upstart contender," said Fabian Schmidt of the California Institute of Technology in Pasadena, who led the study. "Our work shows that the chances of its upsetting the champ are very slim." In recent years, physicists have turned their attention to competing theories to General Relativity as a possible explanation for the accelerated expansion of the universe. Currently, the most popular explanation for the acceleration is the so-called cosmological constant, which can be understood as energy that exists in empty space. This energy is referred to as dark energy to emphasize that it cannot be directly detected. In the f(R) theory, the cosmic acceleration comes not from an exotic form of energy but from a modification of the gravitational force. The modified force also affects the rate at which small enhancements of matter can grow over the eons to become massive clusters of galaxies, opening up the possibility of a sensitive test of the theory. Schmidt and colleagues used mass estimates of 49 galaxy clusters in the local universe from Chandra observations, and compared them with theoretical model predictions and studies of supernovas, the cosmic microwave background, and the large-scale distribution of galaxies. They found no evidence that gravity is different from General Relativity on scales larger than 130 million light years. This limit corresponds to a hundred-fold improvement on the bounds of the modified gravitational force's range that can be set without using the cluster data. "This is the strongest ever constraint set on an alternative to General Relativity on such large distance scales," said Schmidt. "Our results show that we can probe gravity stringently on cosmological scales by using observations of galaxy clusters." The reason for this dramatic improvement in constraints can be traced to the greatly enhanced gravitational forces acting in clusters as opposed to the universal background expansion of the universe. The cluster-growth technique also promises to be a good probe of other modified gravity scenarios, such as models motivated by higher-dimensional theories and string theory. A second, independent study also bolsters General Relativity by directly testing it across cosmological distances and times. Up until now, General Relativity had been verified only using experiments from laboratory to Solar System scales, leaving the door open to the possibility that General Relativity breaks down on much larger scales. To probe this question, a group at Stanford University compared Chandra observations of how rapidly galaxy clusters have grown over time to the predictions of General Relativity. The result is nearly complete agreement between observation and theory. "Einstein's theory succeeds again, this time in calculating how many massive clusters have formed under gravity's pull over the last five billion years," said David Rapetti of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University and SLAC National Accelerator Laboratory, who led the new study. "Excitingly and reassuringly, our results are the most robust consistency test of General Relativity yet carried out on cosmological scales." Rapetti and his colleagues based their results on a sample of 238 c

2010-04-01

281

Revisiting Einstein's brain in Brain Awareness Week.  

PubMed

Albert Einstein's brain has long been an object of fascination to both neuroscience specialists and the general public. However, without records of advanced neuro-imaging of his brain, conclusions regarding Einstein's extraordinary cognitive capabilities can only be drawn based on the unique external features of his brain and through comparison of the external features with those of other human brain samples. The recent discovery of 14 previously unpublished photographs of Einstein's brain taken at unconventional angles by Dr. Thomas Stoltz Harvey, the pathologist, ignited a renewed frenzy about clues to explain Einstein's genius. Dr. Dean Falk and her colleagues, in their landmark paper published in Brain (2013; 136:1304-1327), described in such details about the unusual features of Einstein's brain, which shed new light on Einstein's intelligence. In this article, we ask what are the unique structures of his brain? What can we learn from this new information? Can we really explain his extraordinary cognitive capabilities based on these unique brain structures? We conclude that studying the brain of a remarkable person like Albert Einstein indeed provides us a better example to comprehensively appreciate the relationship between brain structures and advanced cognitive functions. However, caution must be exercised so as not to over-interpret his intelligence solely based on the understanding of the surface structures of his brain. PMID:25382446

Chen, Hao; Chen, Su; Zeng, Lidan; Zhou, Lin; Hou, Shengtao

2014-01-01

282

STP Einstein Solid Heat Bath Program  

NSDL National Science Digital Library

The STP EinsteinSolidHeatBath program simulates the exchange of energy between an Einstein solid and a heat bath. The purpose of this simulation is to determine the properties of a Einstein solid at different temperature T and to compare our results with analytical calculations of the thermodynamic properties of the Einstein solid. The default state is an Einstein solid of N=20 particles in contact with a heat bath at temperature T = 2. Additional states and parameters can be specified using the Display|Switch GUI menu item. STP EinsteinSolidHeatBath is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double-clicking the stp_EinsteinSolidHeatBath.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-05-28

283

Bed load transport over a broad range of timescales: Determination of three regimes of fluctuations  

NASA Astrophysics Data System (ADS)

paper describes the relationship between the statistics of bed load transport flux and the timescale over which it is sampled. A stochastic formulation is developed for the probability distribution function of bed load transport flux, based on the Ancey et al. (2008) theory. An analytical solution for the variance of bed load transport flux over differing sampling timescales is presented. The solution demonstrates that the timescale dependence of the variance of bed load transport flux reduces to a three-regime relation demarcated by an intermittency timescale (tI) and a memory timescale (tc). As the sampling timescale increases, this variance passes through an intermittent stage (?tI), an invariant stage (tI < t < tc), and a memoryless stage (? tc). We propose a dimensionless number (Ra) to represent the relative strength of fluctuation, which provides a common ground for comparison of fluctuation strength among different experiments, as well as different sampling timescales for each experiment. Our analysis indicates that correlated motion and the discrete nature of bed load particles are responsible for this three-regime behavior. We use the data from three experiments with high temporal resolution of bed load transport flux to validate the proposed three-regime behavior. The theoretical solution for the variance agrees well with all three sets of experimental data. Our findings contribute to the understanding of the observed fluctuations of bed load transport flux over monosize/multiple-size grain beds, to the characterization of an inherent connection between short-term measurements and long-term statistics, and to the design of appropriate sampling strategies for bed load transport flux.

Ma, Hongbo; Heyman, Joris; Fu, Xudong; Mettra, Francois; Ancey, Christophe; Parker, Gary

2014-12-01

284

Dynamic hyporheic exchange at intermediate timescales: testing the relative importance of evapotranspiration and flood pulses  

USGS Publications Warehouse

Hyporheic fluxes influence ecological processes across a continuum of timescales. However, few studies have been able to characterize hyporheic fluxes and residence time distributions (RTDs) over timescales of days to years, during which evapotranspiration (ET) and seasonal flood pulses create unsteady forcing. Here we present a data-driven, particle-tracking piston model that characterizes hyporheic fluxes and RTDs based on measured vertical head differences. We used the model to test the relative influence of ET and seasonal flood pulses in the Everglades (FL, USA), in a manner applicable to other low-energy floodplains or broad, shallow streams. We found that over the multiyear timescale, flood pulses that drive relatively deep (?1 m) flow paths had the dominant influence on hyporheic fluxes and residence times but that ET effects were discernible at shorter timescales (weeks to months) as a break in RTDs. Cumulative RTDs on either side of the break were generally well represented by lognormal functions, except for when ET was strong and none of the standard distributions applied to the shorter timescale. At the monthly timescale, ET increased hyporheic fluxes by 1–2 orders of magnitude; it also decreased 6 year mean residence times by 53–87%. Long, slow flow paths driven by flood pulses increased 6 year hyporheic fluxes by another 1–2 orders of magnitude, to a level comparable to that induced over the short term by shear flow in streams. Results suggest that models of intermediate-timescale processes should include at least two-storage zones with different RTDs, and that supporting field data collection occur over 3–4 years.

Larsen, Laurel G.; Harvey, Judson W.; Maglio, Morgan M.

2014-01-01

285

Star Witness News: Albert Einstein, A Genius... Relatively Speaking  

NSDL National Science Digital Library

This story highlights Albert Einstein’s miracle year when he wrote five scientific papers. Connections are made between Einstein’s work and that of the Hubble Space Telescope. The article is from the Amazing Space science newspaper, The Star Witness, which can be used as a science content reading.

286

An Einstein manuscript on the EPR paradox for spin observables  

Microsoft Academic Search

A formulation by Einstein of the Einstein–Podolsky–Rosen incompleteness argument found in his scientific manuscripts is presented and briefly commented on. It is the only known version in which Einstein discussed the argument for spin observables. The manuscript dates, in all probability, from late 1954 or early 1955 and hence also represents Einstein's latest version of the incompleteness argument and one

Tilman Sauer

2007-01-01

287

Einstein M.D. Program 20132014 applicant guide  

E-print Network

Einstein M.D. Program 2013­2014 applicant guide O F Y E S H I V A U N I V E R S I T Y Albert, I wanted to share with you some of my observations about what makes Albert Einstein College Einstein College of Medicine #12;2 Welcome Explore how Einstein can give you the skills to develop

Yates, Andrew

288

Einstein Light: Galilean Relativity and Newtonian Mechanics  

NSDL National Science Digital Library

This animated tutorial, part of the Einstein Light website, presents the concept of relativity from a situation inspired by Galileo (an inertial reference frame). It shows the motion of a ball being dropped from two reference frames: on a moving train and on a stationary platform. How does the motion appear different to the observer on the platform and the observer on the train? The Einstein Light project is a qualitative introduction to relativity, developed for novice learners and built around the framework of Flash media files with narration, video, and animation. It explores concepts ranging from Galilean relativity through Einstein and quantum mechanics.

Wolfe, Joe; Hatsidimitris, George

2007-12-20

289

Sasaki-Einstein and paraSasaki-Einstein metrics from (?,?)-structures  

NASA Astrophysics Data System (ADS)

We prove that every contact metric (?,?)-space admits a canonical ?-Einstein Sasakian or ?-Einstein paraSasakian metric. An explicit expression for the curvature tensor fields of those metrics is given and we find the values of ? and ? for which such metrics are Sasaki-Einstein and paraSasaki-Einstein. Conversely, we prove that, under some natural assumptions, a K-contact or K-paracontact manifold foliated by two mutually orthogonal, totally geodesic Legendre foliations admits a contact metric (?,?)-structure. Furthermore, we apply the above results to the geometry of tangent sphere bundles and we discuss some geometric properties of (?,?)-spaces related to the existence of Einstein-Weyl and Lorentzian-Sasaki-Einstein structures.

Cappelletti-Montano, Beniamino; Carriazo, Alfonso; Martín-Molina, Verónica

2013-11-01

290

Timescales of quartz crystallization and the longevity of the Bishop giant magma body.  

PubMed

Supereruptions violently transfer huge amounts (100 s-1000 s km(3)) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted ~760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of <10,000 years, more typically within 500-3,000 years before eruption. We conclude that large-volume, crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies. PMID:22666359

Gualda, Guilherme A R; Pamukcu, Ayla S; Ghiorso, Mark S; Anderson, Alfred T; Sutton, Stephen R; Rivers, Mark L

2012-01-01

291

Timescales of Quartz Crystallization and the Longevity of the Bishop Giant Magma Body  

PubMed Central

Supereruptions violently transfer huge amounts (100 s–1000 s km3) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted ?760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of <10,000 years, more typically within 500–3,000 years before eruption. We conclude that large-volume, crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies. PMID:22666359

Gualda, Guilherme A. R.; Pamukcu, Ayla S.; Ghiorso, Mark S.; Anderson, Alfred T.; Sutton, Stephen R.; Rivers, Mark L.

2012-01-01

292

A MODEL FOR THE CORRELATION OF HARD X-RAY INDEX WITH EDDINGTON RATIO IN BLACK HOLE X-RAY BINARIES  

SciTech Connect

Observations show that there is a positive correlation between the Eddington ratio {lambda} and hard X-ray index {Gamma} for {lambda} {approx}> 0.01, and there is an anti-correlation between {lambda} and {Gamma} for {lambda} {approx}< 0.01 in black hole X-ray binaries (with {lambda} = L {sub bol}/L {sub Edd}). In this work, we theoretically investigate the correlation between {Gamma} and {lambda} within the framework of a disk-corona model. We improve the model by taking into account all cooling processes, including synchrotron and self-Compton radiations in the corona, Comptonization of the soft photons from the underlying accretion disk, and the bremsstrahlung radiations. Presuming that the coronal flow above the disk can reach up to the 0.1 Eddington rate at the outer region, we calculate the structure of the two-phase accretion flows and the emergent spectra for accretion rates from 0.003 to 0.1. We find that at accretion rates larger than bsim0.01 Eddington rate, a fraction of coronal gas condenses into the disk and an inner disk can be sustained by condensation. In this case, the X-ray emission is dominated by the scattering of the soft photon from the underlying disk in the corona. The emission from the inner disk and corona can produce the positive correlation between {lambda} and {Gamma}. While at accretion rates lower than bsim0.01 Eddington accretion rate, the inner disk vanishes completely by evaporation, and the accretion is dominated by advection-dominated accretion flows (ADAFs), in which the X-ray emission is produced by the Comptonization of the synchrotron and bremsstrahlung photons of ADAF itself. The emission from ADAFs can produce the anti-correlation between {lambda} and {Gamma}. We show that our model can roughly explain the observed evolution of {Gamma}{sub 3-25keV} with L {sub 0.5-25keV}/L {sub Edd} for the black hole X-ray transient H1743-322 in the decay of 2003 from the thermal-dominated state to low/hard state.

Qiao, Erlin; Liu, B. F., E-mail: qiaoel@nao.cas.cn [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2013-02-10

293

Albert Einstein and Archenhold Observatory 1905 - 2005 (German Title: Albert Einstein und die Archenhold-Sternwarte 1905 -- 2005)  

Microsoft Academic Search

After Einstein came to Berlin, he gave his first popular lecture in the Archenhold Observatory, in 1915, on the special and the general theories of relativity. From then on, friendly relations grew between Archenhold and Einstein, which led to a permanent connection between the Observatory and Einstein's achievement. This contribution presents the background of the connection between Archenhold and Einstein,

Dieter B. Herrmann

2005-01-01

294

Boundary conditions for the Einstein-Christoffel formulation of Einstein's equations  

E-print Network

Specifying boundary conditions continues to be a challenge in numerical relativity in order to obtain a long time convergent numerical simulation of Einstein's equations in domains with artificial boundaries. In this paper, we address this problem for the Einstein--Christoffel (EC) symmetric hyperbolic formulation of Einstein's equations linearized around flat spacetime. First, we prescribe simple boundary conditions that make the problem well posed and preserve the constraints. Next, we indicate boundary conditions for a system that extends the linearized EC system by including the momentum constraints and whose solution solves Einstein's equations in a bounded domain.

Douglas N. Arnold; Nicolae Tarfulea

2006-11-02

295

Einstein's Concept of Rationality in Science and Religion  

E-print Network

as standing in a dynamic or dialectical relationship to each other. 33 NOTES Albert Einstein, "Science and Religion," in Out of My Later Years (henceforth OLY) (Totowa, New Jersey: Littlefield, Adams and Co., 1967), p. 30. 2 Albert Einstein and Leopold... Infeld, The Evolution of Physics (henceforth EOPJ (New York: Simon and Schuster, 1930), p. 51. 3Einstein and Infeld, EOF, p. 292. 4 . . . . Einstein, "Science and Religion," OLY, p. 28. ^Albert Einstein, "Clerk Maxwell's Influence on Hie Evolution...

Fleming, Richard

296

Perturbed Einstein field equations using Maple  

E-print Network

We obtain the perturbed components of affine connection and Ricci tensor using algebraic computation. Naturally, the perturbed Einstein field equations for the vacuum can be written. The method can be used to obtain perturbed equations of the superior order.

M. de Campos

2003-06-19

297

STP Temperature Measurement Einstein Solid Program  

NSDL National Science Digital Library

The STP DemonEinsteinSolid program displays a histogram of the energy of a demon that exchanges energy with an ideal gas of particles. The purpose of this simulation is to understand how the demon acts as an ideal thermometer. The default system is an Einstein solid of N=40 particles. Additional states and parameters can be specified using the Display|Switch GUI menu item. STP DemonEinsteinSolid is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double-clicking the stp_DemonEinsteinSolid.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-05-28

298

Overview of Special Relativity Einstein's Two Postulates  

E-print Network

Overview of Special Relativity Einstein's Two Postulates Relativistic mechanics modify Newton transformations Relativistic equations for mechanics Principle of relativity: the laws of physics apply in all vectors: antisymmetric tensor (4-d) 3 #12;Galilean versus Special Relativity Galilean Relativity Special

Hart, Gus

299

Gyromagnetic ratio of Einstein-Maxwell fields  

Microsoft Academic Search

It is shown that the gyromagnetic factor is g=2 for electrovac solutions of Einstein's equations obtained by the prescription introduced by Ernst. This generalizes Carter's result for the Kerr-Newman metric.

C. Reina; A. Treves

1975-01-01

300

Einstein/Roosevelt Letters: A Unit.  

ERIC Educational Resources Information Center

The letters in this unit of study intended for secondary students are facsimile reproductions of the correspondence between Albert Einstein and President Roosevelt on the possibility of constructing an atomic bomb. Classroom activities are also suggested. (RM)

Bodle, Walter S.

1985-01-01

301

How History Helped Einstein in Special Relativity  

NASA Astrophysics Data System (ADS)

I will discuss how the German intellectual movement known as ``critical history'' motivated several physicists in the late 1900s to radically analyze the fundamental principles of mechanics, leading eventually to Einstein's special theory of relativity. Eugen Karl Dühring, Johann Bernhard Stallo, Ludwig Lange, and Ernst Mach wrote critical histories of mechanics, some of which emphasized notions of relativity and observation, in opposition to old metaphysical concepts that seemed to infect the foundations of physics. This strand of critical history included the ``genetic method'' of analyzing how concepts develop over time, in our minds, by way of ordinary experiences, which by 1904 was young Albert Einstein's favorite approach for examining fundamental notions. Thus I will discuss how history contributed in Einstein's path to relativity, as well as comment more generally on Einstein's views on history.

Martinez, Alberto

2013-04-01

302

The creativity of Einstein and astronomy  

NASA Technical Reports Server (NTRS)

A discussion of Einstein's scientific achievements for the 100th anniversary of his birth is presented. His works dealing with thermodynamics are described, along with his quantum theory of radiation. Most of the article discusses his general theory of relativity.

Zeldovich, Y. B.

1980-01-01

303

Bose-Einstein Condensation in Microgravity  

NASA Astrophysics Data System (ADS)

Albert Einstein’s insight that it is impossible to distinguish a local experiment in a “freely falling elevator” from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.

van Zoest, T.; Gaaloul, N.; Singh, Y.; Ahlers, H.; Herr, W.; Seidel, S. T.; Ertmer, W.; Rasel, E.; Eckart, M.; Kajari, E.; Arnold, S.; Nandi, G.; Schleich, W. P.; Walser, R.; Vogel, A.; Sengstock, K.; Bongs, K.; Lewoczko-Adamczyk, W.; Schiemangk, M.; Schuldt, T.; Peters, A.; Könemann, T.; Müntinga, H.; Lämmerzahl, C.; Dittus, H.; Steinmetz, T.; Hänsch, T. W.; Reichel, J.

2010-06-01

304

Hierarchical maximum entropy principle for generalized superstatistical systems and Bose-Einstein condensation of light.  

PubMed

A principle of hierarchical entropy maximization is proposed for generalized superstatistical systems, which are characterized by the existence of three levels of dynamics. If a generalized superstatistical system comprises a set of superstatistical subsystems, each made up of a set of cells, then the Boltzmann-Gibbs-Shannon entropy should be maximized first for each cell, second for each subsystem, and finally for the whole system. Hierarchical entropy maximization naturally reflects the sufficient time-scale separation between different dynamical levels and allows one to find the distribution of both the intensive parameter and the control parameter for the corresponding superstatistics. The hierarchical maximum entropy principle is applied to fluctuations of the photon Bose-Einstein condensate in a dye microcavity. This principle provides an alternative to the master equation approach recently applied to this problem. The possibility of constructing generalized superstatistics based on a statistics different from the Boltzmann-Gibbs statistics is pointed out. PMID:23005064

Sob'yanin, Denis Nikolaevich

2012-06-01

305

Microphysical Timescales in Clouds and their Application in Cloud-Resolving Modeling  

NASA Technical Reports Server (NTRS)

Computational phenomena (i.e., spurious supersaturation and negative mixing ratio of cloud water) usually exist in cloud-resolving models when the time step for explicit integration is larger than a microphysical timescale in clouds. In this paper, the microphysical timescales in clouds are studied, showing that the timescale of water vapor condensation (or cloud water evaporation) is smaller than 10 s - the order of a typical time step for cloud-resolving models. To avoid spurious computational phenomena in cloud-resolving modeling, it is suggested that moist entropy be used as a prognostic thermodynamic variable, and temperature be diagnosed from that and other prognostic variables. A simple numerical model with moist entropy as a prognostic variable, for example, is presented to show that spurious computational phenomena are removed when moist entropy is used as a prognostic variable.

Zeng, Xi-Ping; Tao, Wei-Kuo; Simpson, Joanne

2004-01-01

306

A Search for Short Timescale Microvariability in Active Galactic Nuclei in the Ultraviolet  

NASA Technical Reports Server (NTRS)

We observed four AGNs (the type-1 Seyfert systems 3C249.1, NGC 6814 and Mrk 205, and the BL Lac object 3C371) using the High Speed Photometer on the Hubble Space Telescope to search for short timescale microvariability in the W. Continuous observations of 3 0 0 0 s duration were obtained for each system on several consecutive HST orbits using a 1 s sample time in a 1400 - 3000 2 bandpass. variability > 0.3 % (0 . 003 mag) was detected in any AGN on timescales shorter than 1500 s. The distribution of photon arrival times observed from each source was consistent with Poisson statistics. Because of HST optical problems, the limit on photometric variability at longer timescales is less precise. These results restrict models of supermassive black holes as the central engine of an AGN and the diskoseismology oscillations of any accretion disk around such a black hole.

Dolan, Joseph F.; Clark, L. Lee

2003-01-01

307

Einstein's Biggest Blunder: A Cosmic Mystery Story  

ScienceCinema

The standard model of cosmology built up over 20 years is no longer accepted as accurate. New data suggest that most of the energy density of the universe may be contained in empty space. Remarkably, this is exactly what would be expected if Einstein's cosmological constant really exists. If it does, its origin is the biggest mystery in physics and presents huge challenges for the fundamental theories of elementary particles and fields. Krauss explains Einstein's concept and describes its possible implications.

Lawrence Krauss

2010-09-01

308

Human dynamics: Darwin and Einstein correspondence patterns  

Microsoft Academic Search

In an era when letters were the main means of exchanging scientific ideas and results, Charles Darwin (1809-82) and Albert Einstein (1879-1955) were notably prolific correspondents. But did their patterns of communication differ from those associated with the instant-access e-mail of modern times? Here we show that, although the means have changed, the communication dynamics have not: Darwin's and Einstein's

João Gama Oliveira; Albert-László Barabási

2005-01-01

309

Response of vegetation to drought time-scales across global land biomes  

PubMed Central

We evaluated the response of the Earth land biomes to drought by correlating a drought index with three global indicators of vegetation activity and growth: vegetation indices from satellite imagery, tree-ring growth series, and Aboveground Net Primary Production (ANPP) records. Arid and humid biomes are both affected by drought, and we suggest that the persistence of the water deficit (i.e., the drought time-scale) could be playing a key role in determining the sensitivity of land biomes to drought. We found that arid biomes respond to drought at short time-scales; that is, there is a rapid vegetation reaction as soon as water deficits below normal conditions occur. This may be due to the fact that plant species of arid regions have mechanisms allowing them to rapidly adapt to changing water availability. Humid biomes also respond to drought at short time-scales, but in this case the physiological mechanisms likely differ from those operating in arid biomes, as plants usually have a poor adaptability to water shortage. On the contrary, semiarid and subhumid biomes respond to drought at long time-scales, probably because plants are able to withstand water deficits, but they lack the rapid response of arid biomes to drought. These results are consistent among three vegetation parameters analyzed and across different land biomes, showing that the response of vegetation to drought depends on characteristic drought time-scales for each biome. Understanding the dominant time-scales at which drought most influences vegetation might help assessing the resistance and resilience of vegetation and improving our knowledge of vegetation vulnerability to climate change. PMID:23248309

Vicente-Serrano, Sergio M.; Gouveia, Célia; Camarero, Jesús Julio; Beguería, Santiago; Trigo, Ricardo; López-Moreno, Juan I.; Azorín-Molina, César; Pasho, Edmond; Lorenzo-Lacruz, Jorge; Revuelto, Jesús; Morán-Tejeda, Enrique; Sanchez-Lorenzo, Arturo

2013-01-01

310

Conical Kähler-Einstein Metrics Revisited  

NASA Astrophysics Data System (ADS)

In this paper we introduce the "interpolation-degeneration" strategy to study Kähler-Einstein metrics on a smooth Fano manifold with cone singularities along a smooth divisor that is proportional to the anti-canonical divisor. By "interpolation" we show the angles in (0, 2?] that admit a conical Kähler-Einstein metric form a connected interval, and by "degeneration" we determine the boundary of the interval in some important cases. As a first application, we show that there exists a Kähler-Einstein metric on with cone singularity along a smooth conic (degree 2) curve if and only if the angle is in (?/2, 2?]. When the angle is 2?/3 this proves the existence of a Sasaki-Einstein metric on the link of a three dimensional A 2 singularity, and thus answers a question posed by Gauntlett-Martelli-Sparks-Yau. As a second application we prove a version of Donaldson's conjecture about conical Kähler-Einstein metrics in the toric case using Song-Wang's recent existence result of toric invariant conical Kähler-Einstein metrics.

Li, Chi; Sun, Song

2014-11-01

311

On the mode switching timescales of pulsar PSR B0329+54  

NASA Astrophysics Data System (ADS)

Chen et al. (2011) found that the durations (timescales) of the normal and abnormal modes of PSR B0329+54 follow a gamma distribution, and constrained the parameters of the distribution function. In this paper, we perform a further analysis on the relationship between the timescales of the two modes. The ratio between the durations of a normal mode and the succeeding abnormal mode is calculated for 54 such pairs. It is found that the cumulative distribution function (CDF) of the ratio is consistent with the CDF obtained by assuming random mode switching, suggesting that the two modes work independently.

Wang, Hong-Guang; Chen, Jian-Ling; Wen, Zhi-Gang; Pi, Fei-Peng

2013-03-01

312

Multiparticle Bose-Einstein correlations  

NASA Astrophysics Data System (ADS)

Multiparticle symmetrization effects are contributions to the spectra of Bose-symmetrized states which are not the product of pairwise correlations. Usually they are neglected in particle interferometric calculations which aim at determining the geometry of the boson emitting source from the measured momentum distributions. Based on a method introduced by Zajc and Pratt, we give a calculation of all multiparticle symmetrization effects to the one- and two-particle momentum spectra for a Gaussian phase-space distribution of emission points. Our starting point is an ensemble of N-particle Bose-symmetrized wave functions with specified phase-space localization. In scenarios typical for relativistic heavy-ion collisions, multiparticle effects steepen the slope of the one-particle spectrum for realistic particle phase-space densities by up to 20 MeV, and they broaden the relative momentum dependence of the two-particle correlations. We discuss these modifications and their consequences in quantitative detail. Also, we explain how multiparticle effects modify the normalization of the two-particle correlator. The resulting normalization conserves event probabilities, which is not the case for the commonly used pair approximation. Finally, we propose a method of calculating Bose-Einstein weights from the output of event generators, taking multiparticle correlations into account.

Wiedemann, Urs Achim

1998-06-01

313

Einstein und der Eötvös-Versuch: Ein Brief Albert Einsteins an Willy Wien  

Microsoft Academic Search

Das Aequivalenzprinzip wurde von Einstein erst 1907 in Worte gefasst. Er wendete sich 1912 brieflich an W. Wien mit der Bitte, den Unterschied der Schwingungsdauer eines Uranpendels und eines Bleipendels sowie die Proportionalität der trägen und schweren Massen eines Blei- und eines Urangewichts auszumessen, und zwar mit einer Drehwage. Der Brief macht es klar, dass Einstein bei der Aufstellung des

József Illy

1989-01-01

314

Liver transplantation at Hospital Israelita Albert Einstein Transplante de fígado no Hospital Israelita Albert Einstein  

Microsoft Academic Search

Objective: To present patients and results of liver transplantation performed by the Liver Unit team at the Hospital Israelita Albert Einstein. Methods: The medical records of all patients transplanted by the team at the Liver Unit of the Hospital Israelita Albert Einstein, from January 2002 to June 2005, were analyzed. Results: During this period, 328 transplants were performed and 64.3%

Sergio Mies

315

Einstein's Revolutionary Light-Quantum Hypothesis  

NASA Astrophysics Data System (ADS)

The paper in which Albert Einstein proposed his light-quantum hypothesis was the only one of his great papers of 1905 that he himself termed ``revolutionary.'' Contrary to widespread belief, Einstein did not propose his light-quantum hypothesis ``to explain the photoelectric effect.'' Instead, he based his argument for light quanta on the statistical interpretation of the second law of thermodynamics, with the photoelectric effect being only one of three phenomena that he offered as possible experimental support for it. I will discuss Einstein's light-quantum hypothesis of 1905 and his introduction of the wave-particle duality in 1909 and then turn to the reception of his work on light quanta by his contemporaries. We will examine the reasons that prominent physicists advanced to reject Einstein's light-quantum hypothesis in succeeding years. Those physicists included Robert A. Millikan, even though he provided convincing experimental proof of the validity of Einstein's equation of the photoelectric effect in 1915. The turning point came after Arthur Holly Compton discovered the Compton effect in late 1922, but even then Compton's discovery was contested both on experimental and on theoretical grounds. Niels Bohr, in particular, had never accepted the reality of light quanta and now, in 1924, proposed a theory, the Bohr-Kramers-Slater theory, which assumed that energy and momentum were conserved only statistically in microscopic interactions. Only after that theory was disproved experimentally in 1925 was Einstein's revolutionary light-quantum hypothesis generally accepted by physicists---a full two decades after Einstein had proposed it.

Stuewer, Roger H.

2005-05-01

316

Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano  

E-print Network

1 Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano T of Santorini Volcano, Greece4 . The results provide insights into how rapidly large silicic systems may pass to unrest at long-dormant, but potentially active, caldera systems such as Yellowstone or Campi Flegrei2

Boyer, Edmond

317

Accuracy evaluation of weather data generation and disaggregation methods at finer timescales  

Microsoft Academic Search

Availability of weather data at finer timescales such as hourly is vital in the application of dynamic physical and biological models. In this study, we have examined the suitability of various approaches (deterministic periodic versus stochastic) of disaggregating daily weather data into hourly data in the Cedar Creek watershed, TX, USA. We found the cosine function suitable to disaggregate daily

Bekele Debele; R. Srinivasan; J. Yves Parlange

2007-01-01

318

Optimal structured feedback policies for ABR flow control using two-timescale SPSA  

Microsoft Academic Search

Optimal structured feedback control policies for rate-based flow control of available bit rate service in asynchronous transfer mode networks are obtained in the presence of information and propagation delays, using a numerically efficient two-timescale simultaneous perturbation stochastic approximation algorithm. Models comprising both a single bottleneck node and a network with multiple bottleneck nodes are considered. A convergence analysis of the

Shalabh Bhatnagar; Michael C. Fu; Steven I. Marcus; Pedram J. Fard

2001-01-01

319

Erosion Rates Over Millennial and Decadal Timescales at Caspar Creek and Redwood  

E-print Network

Erosion Rates Over Millennial and Decadal Timescales at Caspar Creek and Redwood Creek, Northern California1 Ken L. Ferrier,2 James W. Kirchner,3 and Robert C. Finkel4 Erosion rate measurements ecosystems. Traditionally, erosion rates have been determined by measuring stream sediment fluxes over

Standiford, Richard B.

320

A sensitivity study of fast outlet glaciers to short timescale cyclical perturbations  

NASA Astrophysics Data System (ADS)

The dynamic response of outlet glaciers on short (annual to decadal) timescales is affected by various external forcings, such as basal or oceanic conditions. Understanding the sensitivity of the dynamic response to such forcings can help assess more accurate ice volume projections. In this work, we investigate the spatiotemporal sensitivity of outlet glaciers to fast cyclical forcings using a one-dimensional depth and width-averaged heuristic model. Our results indicate that even on such short timescales, nonlinearities in ice dynamics may lead to an asymmetric response, despite the forcing functions being symmetric around each reference value. Results also show that such short-timescale effects become more pronounced as glaciers become closer to flotation. While being qualitatively similar for both downsloping and upsloping bed geometries, the results indicate higher sensitivity for upsloping ("West Antarctica-like") beds. The range in asymmetric response for different configurations motivate parameterizing or including short-timescale effects in models while investigating the dynamic behavior of outlet glaciers.

Aykutlug, E.; Dupont, T. K.

2015-01-01

321

Charge transfer at surfaces on femtosecond timescales: New information from electron spectroscopies  

Microsoft Academic Search

Charge transfer (CT) between an adsorbed atom or molecule and its substrate is of direct importance for the understanding of photochemical surface processes and more generally of the adsorbate-substrate coupling. A direct measurement of its timescales is difficult as it is extremely fast (from less than a fs to some or some tens of fs, as deduced from indirect evidence).

D. Menzel; W. Wurth

2000-01-01

322

Nonequilibrium, multiple-timescale simulations of ligand-receptor interactions in structured protein systems  

Microsoft Academic Search

Predicting the long-time, nonequi- librium dynamics of receptor-ligand interactions for structured proteins in a host fluid is a formi- dable task, but of great importance to predicting and analyzing cell-signaling processes and small molecule drug efficacies. Such processes take place on timescales on the order of milliseconds to sec- onds, so \\

Ying Zhang; Michael H. Peters; Yaohang Li

2003-01-01

323

Processes and timescales in the evolution of a chemically zoned trachyte: Fogo A, Sao Miguel, Azores  

Microsoft Academic Search

U-series disequilibria analyses have been combined with chemical and petrographic analyses in order to assess both the timescales and processes involved in the formation of the chemically zoned Fogo A trachytes. Least squares major element modelling demonstrates that the mafic trachytes could have evolved from a parental alkali basalt via trachybasalt with ~70% fractionation of augite (35–36%), plagioclase (23%), magnetite

E. Widom; H.-U. Schmincke; J. B. Gill

1992-01-01

324

Photoelectrons as a tool to evaluate spectral variations in solar EUV irradiance over solar cycle timescales  

Microsoft Academic Search

There is limited information about the relative magnitude of the spectral variations in the ionizing component of solar irradiance on solar cycle timescales. We found that the Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED)\\/Solar Extreme Ultraviolet Experiment (SEE) Version 9 irradiance values predict relatively more ionospheric heating at solar minimum than those from Version 8. These changes have direct impacts

W. K. Peterson; E. N. Stavros; P. G. Richards; P. C. Chamberlin; T. N. Woods; S. M. Bailey; S. C. Solomon

2009-01-01

325

Quantification of the role of orbital and millennial timescale processes on ?18O and 17? signals  

NASA Astrophysics Data System (ADS)

The triple isotope composition of atmospheric oxygen (?18O, 17?) integrates the signature of various processes, both on orbital and millennial timescales: changes in global seawater, hydrological cycle, relative humidity, vegetation distribution and C3/C4 plants partition. At the orbital timescale, tropospheric ?18O bears a strong orbital precession signal with a minimum in ?18O shifted by 6 ka relatively to the minimum of precession while at the millennial timescale, ?18O depicts a clear decrease in phase with Greenland InterStadial events. 17? (ln(?17O+1)-?*ln( ?18O+1)) is more directly related to variations in the global biospheric productivity with a main variability associated with the glacial - interglacial changes. Here we make use of a global model integrating changes in climate, biosphere productivity, water isotopic composition to quantify the contribution of the different processes to ?18O and 17? signals. The model accounts for the latest fractionation ratios between 18O /16O and 17O/16O associated with oxygen respiration processes and leaf transpiration, oceanic net primary production (simulated by PISCES model), the spatial and temporal variation of vegetation distribution (simulated by ORCHIDEE model), climatic conditions and isotopic composition of meteoric water and water vapor (LMDZ global circulation model). The model is applied at relevant orbital periods (snapshots of pre-industrial period, Last Glacial Maximum (LGM), Heinrich event and Eemian interglacial) and allow us to further explore the role of orbital and millennial timescale processes on ?18O and 17? signals.

Reutenauer, C.; Landais, A.; Woillez, M.-N.; Risi, C.; Braconnot, P.; Blunier, T.; Mariotti, V.; Kageyama, M.

2012-04-01

326

Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic  

Microsoft Academic Search

Recently reported radioisotopic dates and magnetic anomaly spacings have made it evident that modification is required for the age calibrations for the geomagnetic polarity timescale of Cande and Kent (1992) at the Cretaceous\\/Paleogene boundary and in the Pliocene. An adjusted geomagnetic reversal chronology for the Late Cretaceous and Cenozoic is presented that is consistent with astrochronology in the Pleistocene and

S. C. Cande; D. V. Kent

1995-01-01

327

New time-scale criteria for model simplification of bio-reaction systems  

PubMed Central

Background Quasi-steady state approximation (QSSA) based on time-scale analysis is known to be an effective method for simplifying metabolic reaction system, but the conventional analysis becomes time-consuming and tedious when the system is large. Although there are automatic methods, they are based on eigenvalue calculations of the Jacobian matrix and on linear transformations, which have a high computation cost. A more efficient estimation approach is necessary for complex systems. Results This work derived new time-scale factor by focusing on the problem structure. By mathematically reasoning the balancing behavior of fast species, new time-scale criteria were derived with a simple expression that uses the Jacobian matrix directly. The algorithm requires no linear transformation or decomposition of the Jacobian matrix, which has been an essential part for previous automatic time-scaling methods. Furthermore, the proposed scale factor is estimated locally. Therefore, an iterative procedure was also developed to find the possible multiple boundary layers and to derive an appropriate reduced model. Conclusion By successive calculation of the newly derived time-scale criteria, it was possible to detect multiple boundary layers of full ordinary differential equation (ODE) models. Besides, the iterative procedure could derive the appropriate reduced differential algebraic equation (DAE) model with consistent initial values, which was tested with simple examples and a practical example. PMID:18694523

Choi, Junwon; Yang, Kyung-won; Lee, Tai-yong; Lee, Sang Yup

2008-01-01

328

Timescales of mixing and mobilisation in the Bishop Tuff magma body: perspectives from diffusion chronometry  

NASA Astrophysics Data System (ADS)

We present two-feldspar thermometry and diffusion chronometry from sanidine, orthopyroxene and quartz from multiple samples of the Bishop Tuff, California, to constrain the temperature stratification within the pre-eruptive magma body and the timescales of magma mixing prior to its evacuation. Two-feldspar thermometry yields estimates that agree well with previous Fe-Ti oxide thermometry and gives a ~80 °C temperature difference between the earlier- and later-erupted regions of the magma chamber. Using the thermometry results, we model diffusion of Ti in quartz, and Ba and Sr in sanidine as well as Fe-Mg interdiffusion in orthopyroxene to yield timescales for the formation of overgrowth rims on these crystal phases. Diffusion profiles of Ti in quartz and Fe-Mg in orthopyroxene both yield timescales of <150 years for the formation of overgrowth rims. In contrast, both Ba and Sr diffusion in sanidine yield nominal timescales 1-2 orders of magnitude longer than these two methods. The main cause for this discrepancy is inferred to be an incorrect assumption for the initial profile shape for Ba and Sr diffusion modelling (i.e. growth zoning exists). Utilising the divergent diffusion behaviour of Ba and Sr, we place constraints on the initial width of the interface and can refine our initial conditions considerably, bringing Ba and Sr data into alignment, and yielding timescales closer to 500 years, the majority of which are then within uncertainty of timescales modelled from Ti diffusion in quartz. Care must be thus taken when using Ba in sanidine geospeedometry in evolved magmatic systems where no other phases or elements are available for comparative diffusion profiling. Our diffusion modelling reveals piecemeal rejuvenation of the lower parts of the Bishop Tuff magma chamber at least 500 years prior to eruption. Timescales from our mineral profiling imply either that diffusion coefficients currently used are uncertain by 1-2 orders of magnitude, or that the minerals concerned did not experience a common history, despite being extracted from the same single pumice clasts. Introduction of the magma initiating crystallisation of the contrasting rims on sanidine, quartz, orthopyroxene and zircon was prolonged, and may be a marker of other processes that initiated the Bishop Tuff eruption rather than the trigger itself.

Chamberlain, Katy J.; Morgan, Daniel J.; Wilson, Colin J. N.

2014-07-01

329

Integrating timescales with time-transfer functions: a practical approach for an INTIMATE database  

NASA Astrophysics Data System (ADS)

The purpose of the INTIMATE project is to integrate palaeo-climate information from terrestrial, ice and marine records so that the timing of environmental response to climate forcing can be compared in both space and time. One of the key difficulties in doing this is the range of different methods of dating that can be used across different disciplines. For this reason, one of the main outputs of INTIMATE has been to use an event-stratigraphic approach which enables researchers to co-register synchronous events (such as the deposition of tephra from major volcanic eruptions) in different archives (Blockley et al., 2012). However, this only partly solves the problem, because it gives information only at particular short intervals where such information is present. Between these points the ability to compare different records is necessarily less precise chronologically. What is needed therefore is a way to quantify the uncertainties in the correlations between different records, even if they are dated by different methods, and make maximum use of the information available that links different records. This paper outlines the design of a database that is intended to provide integration of timescales and associated environmental proxy information. The database allows for the fact that all timescales have their own limitations, which should be quantified in terms of the uncertainties quoted. It also makes use of the fact that each timescale has strengths in terms of describing the data directly associated with it. For this reason the approach taken allows users to look at data on any timescale that can in some way be related to the data of interest, rather than specifying a specific timescale or timescales which should always be used. The information going into the database is primarily: proxy information (principally from sediments and ice cores) against depth, age depth models against reference chronologies (typically IntCal or ice core), and time-transfer functions that relate different timescales to each other, through the use of event stratigraphies or global phenomena such as cosmogenic isotope production rate variations.

Bronk Ramsey, Christopher; Albert, Paul; Blockley, Simon; Hardiman, Mark; Lane, Christine; Macleod, Alison; Matthews, Ian P.; Muscheler, Raimund; Palmer, Adrian; Staff, Richard A.

2014-12-01

330

Einstein's equivalence principle in cosmology  

E-print Network

We study physical consequences of the Einstein equivalence principle (EEP) for a Hubble observer in FLRW universe. We introduce the local inertial coordinates with the help of a special conformal transformation. The local inertial metric is Minkowski-flat and materialized by a congruence of time-like geodesics of static observers. The static observers are equipped with the ideal clocks measuring the proper time that is synchronized with the clocks of the Hubble observer. The local inertial metric is used for physical measurements of spacetime intervals with the ideal clocks and rulers. The special conformal transformation preserves null geodesics but does not keep invariant time-like geodesics. Moreover, it makes the rate of the local time coordinate dependent on velocity of the particle which makes impossible to rich the uniform parameterization of the world lines of static observers and light geodesics with a single parameter - they differ by the conformal factor of FLRW metric. It tells us that the metric on the light cone is not Minkowski-flat but depends on the scale factor of FLRW universe and it can be interpreted as a weak violation of EEP for photons. The importance of this violation for gravitational physics is that some of local experiments conducted with freely-propagating electromagnetic waves may be sensitive to the Hubble expansion. We show that the Hubble constant H can be measured within the solar system by means of high-precision spacecraft Doppler tracking as a blue shift of frequency of radio waves circulating in the Earth-spacecraft radio link. We also analyze the behavior of the standing wave in a microwave resonator and show that the standing wave is insensitive to the Hubble expansion.

Sergei M. Kopeikin

2014-02-18

331

U-series constraints on sediment residence timescales in semi-arid Australia  

NASA Astrophysics Data System (ADS)

Fractionation of uranium isotopes (234U and 238U) in fine-grained sediment (< 50 ?m) can be used to quantify timescales of sediment residence i.e. storage in soils and associated transport in fluvial or aeolian systems. This information is invaluable for understanding the relationships between climate, tectonics and landscape evolution. In particular, how sediment transport and the landscape have responded to climate change over the past 100,000 yrs. (234U/238U) activity ratios have been measured in the fine fraction (2-50 ?m) of palaeochannel sediments from the Katipiri Formation of the Cooper Creek in the Strzelecki Desert (south Australia). Cooper Creek is one of three major rivers feeding the Lake Eyre Basin, one of the largest internally-drained catchments in the world. Sediments were collected from six palaeochannels with depositional ages ranging from 119±11 to 22± ka (optically-stimulated luminescence (OSL) dating). U-series and OSL data are combined in order to constrain the time elapsed between production by physical weathering of the source bedrock (comminution age) and the deposition age, to give an average residence time of the sediment in the catchment. Preliminary work yields sediment residence timescales between 66±10 to 107±17 ka. The inferred residence timescales for Cooper Creek sediments, in what today is a semi-arid environment, are comparable to sediment residence timescales (of similar depositional age) in temperate Australia. This suggests that the strong links observed between climate change and sediment transport during the last glacial cycle in temperate Australia maybe be witnessed Australia-wide. Future research is required to assess the contribution of wind-blown dust and its effect on calculated sediment residence timescales.

Handley, Heather; Dosseto, Anthony; Suresh, P. O.; Cohen, Tim; Turner, Simon

2010-05-01

332

Einstein's vierbein field theory of curved space  

E-print Network

General Relativity theory is reviewed following the vierbein field theory approach proposed in 1928 by Einstein. It is based on the vierbein field taken as the "square root" of the metric tensor field. Einstein's vierbein theory is a gauge field theory for gravity; the vierbein field playing the role of a gauge field but not exactly like the vector potential field does in Yang-Mills theory--the correction to the derivative (the covariant derivative) is not proportional to the vierbein field as it would be if gravity were strictly a Yang-Mills theory. Einstein discovered the spin connection in terms of the vierbein fields to take the place of the conventional affine connection. To date, one of the most important applications of the vierbein representation is for the derivation of the correction to a 4-spinor quantum field transported in curved space, yielding the correct form of the covariant derivative. Thus, the vierbein field theory is the most natural way to represent a relativistic quantum field theory in curved space. Using the vierbein field theory, presented is a derivation of the the Einstein equation and then the Dirac equation in curved space. Einstein's original 1928 manuscripts translated into English are included.

Jeffrey Yepez

2011-06-10

333

On (ab)normality: Einstein's fusiform gyrus.  

PubMed

Recently, Hines (2014) wrote an evocative paper challenging findings from both histological and morphological studies of Einstein's brain. In this discussion paper, I extend Hines' theoretical point and further discuss how best to determine 'abnormal' morphology. To do so, I assess the sulcal patterning of Einstein's fusiform gyrus (FG) for the first time. The sulcal patterning of the FG was unconsidered in prior studies because the morphological features of the mid-fusiform sulcus have only been clarified recently. On the one hand, the sulcal patterning of Einstein's FG is abnormal relative to averages of 'normal' brains generated from two independent datasets (N=39 and N=15, respectively). On the other hand, within the 108 hemispheres used to make these average brains, it is not impossible to find FG sulcal patterns that resemble those of Einstein. Thus, concluding whether a morphological pattern is normal or abnormal heavily depends on the chosen analysis method (e.g. group average vs. individual). Such findings question the functional meaning of morphological 'abnormalities' when determined by comparing an individual to an average brain or average frequency characteristics. These observations are not only important for analyzing a rare brain such as that of Einstein, but also for comparing macroanatomical features between typical and atypical populations. PMID:25562419

Weiner, Kevin S

2015-03-01

334

Einstein, Ethics and the Atomic Bomb  

NASA Astrophysics Data System (ADS)

Einstein voiced his ethical views against war as well as fascism via venues and alliances with a variety of organizations still debated today. In 1939, he signed a letter to President Roosevelt (drafted by younger colleagues Szilard, Wigner and others) warning the U.S.government about the danger of Nazi Germany gaining control of uranium in the Belgian-controlled Congo in order to develop atomic weapons, based on the discovery of fission by Otto Hahn and Lise Meitner. In 1945, he became a member of the Princeton-based ``Emergency Committee for Atomic Scientists'' organized by Bethe, Condon, Bacher, Urey, Szilard and Weisskopf. Rare Einstein slides will illustrate Dr.Rife's presentation on Albert Einstein's philosophic and ethical convictions about peace, and public stance against war (1914-1950).

Rife, Patricia

2005-03-01

335

Lovelock Tensor as Generalized Einstein Tensor  

E-print Network

We show that the splitting feature of the Einstein tensor, as the first term of the Lovelock tensor, into two parts, namely the Ricci tensor and the term proportional to the curvature scalar, with the trace relation between them is a common feature of any other homogeneous terms in the Lovelock tensor. Motivated by the principle of general invariance, we find that this property can be generalized, with the aid of a generalized trace operator which we define, for any inhomogeneous Euler-Lagrange expression that can be spanned linearly in terms of homogeneous tensors. Then, through an application of this generalized trace operator, we demonstrate that the Lovelock tensor analogizes the mathematical form of the Einstein tensor, hence, it represents a generalized Einstein tensor. Finally, we apply this technique to the scalar Gauss-Bonnet gravity as an another version of string-inspired gravity.

M. Farhoudi

2011-04-03

336

Coherence, Abstraction, and Personal Involvement: Albert Einstein, Physicist and Humanist.  

ERIC Educational Resources Information Center

Reviews Einstein's main contributions to physics, and analyzes the importance of a coherent body of theory. Einstein's involvement in nonscientific issues such as nuclear disarmament is also included. (HM)

Ne'eman, Yuval

1979-01-01

337

Collisions of Einstein-Conformal Scalar Waves  

E-print Network

A large class of solutions of the Einstein-conformal scalar equations in D=2+1 and D=3+1 is identified. They describe the collisions of asymptotic conformal scalar waves and are generated from Einstein-minimally coupled scalar spacetimes via a (generalized) Bekenstein transformation. Particular emphasis is given to the study of the global properties and the singularity structure of the obtained solutions. It is shown, that in the case of the absence of pure gravitational radiation in the initial data, the formation of the final singularity is not only generic, but is even inevitable.

C. Klim?{\\'?}k; P. Koln{\\'?}k

1992-12-18

338

Bose-Einstein Condensation of Erbium  

E-print Network

We report on the achievement of Bose-Einstein condensation of erbium atoms and on the observation of magnetic Feshbach resonances at low magnetic field. By means of evaporative cooling in an optical dipole trap, we produce pure condensates of $^{168}$Er, containing up to $7 \\times 10^{4}$ atoms. Feshbach spectroscopy reveals an extraordinary rich loss spectrum with six loss resonances already in a narrow magnetic-field range up to 3 G. Finally, we demonstrate the application of a low-field Feshbach resonance to produce a tunable dipolar Bose-Einstein condensate and we observe its characteristic d-wave collapse.

Aikawa, K; Mark, M; Baier, S; Rietzler, A; Grimm, R; Ferlaino, F

2012-01-01

339

Human dynamics: Darwin and Einstein correspondence patterns  

NASA Astrophysics Data System (ADS)

In an era when letters were the main means of exchanging scientific ideas and results, Charles Darwin (1809-82) and Albert Einstein (1879-1955) were notably prolific correspondents. But did their patterns of communication differ from those associated with the instant-access e-mail of modern times? Here we show that, although the means have changed, the communication dynamics have not: Darwin's and Einstein's patterns of correspondence and today's electronic exchanges follow the same scaling laws. However, the response times of their surface-mail communication is described by a different scaling exponent from e-mail communication, providing evidence for a new class of phenomena in human dynamics.

Oliveira, João Gama; Barabási, Albert-László

2005-10-01

340

Non-convergence of the critical cooling time-scale for fragmentation of self-gravitating discs  

NASA Astrophysics Data System (ADS)

We carry out a resolution study on the fragmentation boundary of self-gravitating discs. We perform three-dimensional Smoothed Particle Hydrodynamics simulations of discs to determine whether the critical value of the cooling time-scale in units of the orbital time-scale, ?crit, converges with increasing resolution. Using particle numbers ranging from 31 250 to 16 million (the highest resolution simulations to date) we do not find convergence. Instead, fragmentation occurs for longer cooling time-scales as the resolution is increased. These results suggest that at the very least, the critical value of the cooling time-scale is longer than previously thought. However, the absence of convergence also raises the question of whether or not a critical value exists. In light of these results, we caution against using cooling time-scale or gravitational stress arguments to deduce whether gravitational instability may or may not have been the formation mechanism for observed planetary systems.

Meru, Farzana; Bate, Matthew R.

2011-02-01

341

Einstein M.D. Program 20112012 applicant guide  

E-print Network

Einstein M.D. Program 2011­2012 applicant guide O F Y E S H I V A U N I V E R S I T Y Albert. tHe Big pictuRe tHe inSide StORY #12;MeSSage FROM tHe dean WelcOMe At Albert Einstein College of Medicine Einstein College of Medicine #12;2 Welcome Explore how Einstein can give you the skills to develop

Jenny, Andreas

342

Einstein M.D. Program 20132014 applicant guide  

E-print Network

Einstein M.D. Program 2013­2014 applicant guide O F Y E S H I V A U N I V E R S I T Y Albert and our accomplishments. tHe inSide StoRY #12;WelcoMe At Albert Einstein College of Medicine, compassion Einstein College of Medicine #12;2 Welcome Explore how Einstein can give you the skills to develop

Emmons, Scott

343

REVIEW ARTICLE FOCUS BoseEinstein condensation in  

E-print Network

REVIEW ARTICLE FOCUS Bose­Einstein condensation in magnetic insulators The Bose­Einstein condensate produce very rich physics compared with the canonical BEC. Studies of magnon condensation in a growing . It is thus natural to ask whether these bosons can undergo Bose­ Einstein condensation and become superfluid

Loss, Daniel

344

BoseEinstein Condensation of Atomic Hydrogen Dale G. Fried  

E-print Network

Bose­Einstein Condensation of Atomic Hydrogen by Dale G. Fried B.S. Physics Washington State by . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thomas J. Greytak Chairman, Department of Physics Graduate Committee #12; #12; Bose­Einstein Condensation the observation and study of Bose­Einstein condensation (BEC) of magnetically trapped atomic hydrogen. The sample

345

Conceptual Development of Einstein's Mass-Energy Relationship  

ERIC Educational Resources Information Center

Einstein's special theory of relativity was published in 1905. It stands as one of the greatest intellectual achievements in the history of human thought. Einstein described the equivalence of mass and energy as "the most important upshot of the special theory of relativity" (Einstein, 1919). In this paper, we will discuss the evolution of the…

Wong, Chee Leong; Yap, Kueh Chin

2005-01-01

346

Einstein 1905-1955: His Approach to Physics  

NASA Astrophysics Data System (ADS)

We review Einstein's epistemological conceptions, and indicate their philosophical roots. The particular importance of the ideas of Hume, Kant, Mach, and Poincaré is highlighted. The specific characteristics of Einstein's approach to physics are underlined. Lastly, we consider the practical application of Einstein's methodological principles to the two theories of relativity, and to quantum theory. We emphasize a Kantian approach to quantum theory.

Damour, Thibault

347

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY approved in lieu of an additional COGME policy. Revised: Sept. 2004 N.B. The Albert Einstein College on Graduate Medical Education of the Albert Einstein College of Medicine has established written policies

Yates, Andrew

348

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY RESIDENT program sponsored by the Albert Einstein College of Medicine must assess resident performance and use to support the care of patients. 1 N.B. The Albert Einstein College of Medicine serves as the ACGME

Yates, Andrew

349

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY on SEXUAL of residents in the programs sponsored by the Albert Einstein College of Medicine, have established employment that no employee is subjected to such conduct. Originated 9/05 Approved 10/05 1 N.B. The Albert Einstein College

Yates, Andrew

350

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY for residents transferring to an other program. (Revised May 2002) 1 N.B. The Albert Einstein College on Graduate Medical Education of the Albert Einstein College of Medicine has established written policies

Yates, Andrew

351

Albert Einstein In the spring of 1921, five  

E-print Network

Albert Einstein In the spring of 1921, five years after the appear- ance of his comprehensive paper Study, Albert Einstein toured the United States to help raise funds for the establishment of a Hebrew; the remaining three, more technical in nature, formed the rest of the book. In subsequent editions, Einstein

Landweber, Laura

352

The Albert Einstein College of Medicine of Yeshiva University  

E-print Network

The Albert Einstein College of Medicine of Yeshiva University EMERGENCY PROCEDURES MANUAL Prepared Resources Security Revised ­ October, 2014 #12;ALBERT EINSTEIN COLLEGE of MEDICINE of YESHIVA UNIVERSITY............................................................................................................................. 44 #12;ALBERT EINSTEIN COLLEGE of MEDICINE of YESHIVA UNIVERSITY EMERGENCY PROCEDURES MANUAL CIVIL

Jenny, Andreas

353

EINSTEINSpring 2007 spring 2007 I EinstEin  

E-print Network

: A publication for faculty, students, alumni, friends and supporters of the Albert einstein College of Medicine that cover the full spectrum of research currently performed by faculty of the Albert einstein College;spring 2007 I EinstEin eInSTeInCONTENTs 3 A meSSAge from the deAn 4 Children with AidS: the remarkable

Yates, Andrew

354

ALBERT EINSTEIN COLLEGE OF MEDICINE OF YESHIVA UNIVERSITY  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE OF YESHIVA UNIVERSITY JACK AND PEARL RESNICK CAMPUS · 1300: Mr/Ms , social security # , who is presently associated with the Albert Einstein College of Medicine radiation exposure records be released to the Albert Einstein College of Medicine's Radiation Safety Office

Emmons, Scott

355

Albert Einstein College of Medicine Center for Experimental Therapeutics  

E-print Network

Albert Einstein College of Medicine Center for Experimental Therapeutics A Bold New Initiative that afflict humanity. For more than five decades, the Albert Einstein College of Medicine has been one Bringing Hope and Help to Patients #12;Disease Target ID Assay Development HTS* Einstein Center

Kenny, Paraic

356

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY sponsored by the Albert Einstein College of Medicine must not be required to engage in "Moonlighting." 7 May 2002 N.B. The Albert Einstein College of Medicine serves as the ACGME-accredited Institutional

Yates, Andrew

357

ALBERT EINSTEIN COLLEGE OF MEDICINE OF YESHIVA UNIVERSITY  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE OF YESHIVA UNIVERSITY JACK AND PEARL RESNICK CAMPUS · 1300's Responsibility E-MAIL ­ peter.babin@einstein.yu.edu PHONE: (718) 430-2243 Dosimeter/Film Badge Request: Female: 1. Did the Employee/Student have a previous badge at Einstein? 2. Has the Employee

Emmons, Scott

358

Albert Einstein College of Medicine Global Health Center  

E-print Network

Albert Einstein College of Medicine Global Health Center Complete and send to Denise Giocondo at that the funds being sent to the account indicated above belong to Albert Einstein College of Medicine: denise.giocondo@einstein.yu.edu Request to wire funds internationally: Name

Yates, Andrew

359

Einstein 2013-2014 Edition Student to Student  

E-print Network

. This guide does not represent the policies of the Albert Einstein College of Medicine or its affiliated, sexual orientation, or citi- zenship status. Upon hearing of this, Albert Einstein wrote a letter, March 14, 1953, Albert Einstein agreed to lend his name to the medi- cal school, the only institution

Yates, Andrew

360

Einstein M.D. Program 20142015 APPLICANT GUIDE  

E-print Network

Einstein M.D. Program 2014­2015 APPLICANT GUIDE O F Y E S H I V A U N I V E R S I T Y Albert research and our accomplishments. THE INSIDE STORY #12;WELCOME At Albert Einstein College of Medicine experiences available at Montefiore, the University Hospital and academic medical center for Albert Einstein

Emmons, Scott

361

August 5, 2009 How Hume and Mach Helped Einstein  

E-print Network

, Albert Einstein: A Biographical Portrait. New York: Albert and Charles Boni, 1930. p.55 #12;2 endeavor1 August 5, 2009 Addendum How Hume and Mach Helped Einstein Find Special Relativity John D. Norton that it overlooked some material that further illuminated Einstein's attitude to David Hume.1 A revealing remark

362

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY), as the employers of residents in the programs sponsored by the Albert Einstein College of Medicine have established of LOA should be filed with the Office of GME. Revised May 2002 N.B. The Albert Einstein College

Yates, Andrew

363

Albert Einstein College of Medicine of Yeshiva University  

E-print Network

4 1 Strategic Research Plan Albert Einstein College of Medicine of Yeshiva University Jack and Pearl Resnick Campus 1300 Morris Park Avenue Bronx, New York 10461 Albert Einstein College of Medicine.A. Cissell Consulting Design: GRAPHIC ARTS CENTER Creative Director: Peter Dama Albert Einstein College

Emmons, Scott

364

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY), as the employers of residents in the programs sponsored by the Albert Einstein College of Medicine, have each Process Policies of the employing institution. Revised Sept. 2004 1 N.B. The Albert Einstein College

Yates, Andrew

365

PHYSICS BEFORE AND AFTER EINSTEIN This page intentionally left blank  

E-print Network

since he died. There is no question that Albert Einstein with his work on relativity and quantum theoryPHYSICS BEFORE AND AFTER EINSTEIN #12;This page intentionally left blank #12;Physics Before and After Einstein Edited by Marco Mamone Capria University of Perugia, Department of Mathematics

Mamone Capria, Marco

366

Rapid Dust Formation in Novae: Speed Class and Grain Formation Timescale  

NASA Astrophysics Data System (ADS)

Observations show that the time of onset of dust formation in classical novae depends strongly on their speed class, with dust typically taking longer to form in slower novae. Using empirical relationships of speed class, luminosity and ejection velocity, it can be shown that dust formation timescale is expected to be essentially independent of speed class. However, following a nova outburst the spectrum of the central hot source evolves, with an increasing proportion of the radiation being emitted blue-wards of the Lyman limit. The rate at which the spectrum evolves depends on the speed class. We have therefore refined the simple model by assuming photons at wavelengths shorter than the Lyman limit are absorbed by neutral hydrogen gas internal to the dust formation sites. We find that the dust formation timescale is then dependent on speed class and the predicted relationship agrees well with the observations.

Williams, S. C.; Bode, M. F.; Darnley, M. J.; Zubko, V.; Evans, A.; Shafter, A. W.

2014-12-01

367

Elucidation of the timescales and origins of quantum electronic coherence in LHCII  

NASA Astrophysics Data System (ADS)

Photosynthetic organisms harvest sunlight with near unity quantum efficiency. The complexity of the electronic structure and energy transfer pathways within networks of photosynthetic pigment-protein complexes often obscures the mechanisms behind the efficient light-absorption-to-charge conversion process. Recent experiments, particularly using two-dimensional spectroscopy, have detected long-lived quantum coherence, which theory suggests may contribute to the effectiveness of photosynthetic energy transfer. Here, we present a new, direct method to access coherence signals: a coherence-specific polarization sequence, which isolates the excitonic coherence features from the population signals that usually dominate two-dimensional spectra. With this polarization sequence, we elucidate coherent dynamics and determine the overall measurable lifetime of excitonic coherence in the major light-harvesting complex of photosystem II. Coherence decays on two distinct timescales of 47 fs and ~800 fs. We present theoretical calculations to show that these two timescales are from weakly and moderately strongly coupled pigments, respectively.

Schlau-Cohen, Gabriela S.; Ishizaki, Akihito; Calhoun, Tessa R.; Ginsberg, Naomi S.; Ballottari, Matteo; Bassi, Roberto; Fleming, Graham R.

2012-05-01

368

Estimating Black Carbon Aging Time-Scales with a Particle-Resolved Aerosol Model  

SciTech Connect

Understanding the aging process of aerosol particles is important for assessing their chemical reactivity, cloud condensation nuclei activity, radiative properties and health impacts. In this study we investigate the aging of black carbon containing particles in an idealized urban plume using a new approach, the particleresolved aerosol model PartMC-MOSAIC. We present a method to estimate aging time-scales using an aging criterion based on cloud condensation nuclei activation. The results show a separation into a daytime regime where condensation dominates and a nighttime regime where coagulation dominates. For the chosen urban plume scenario, depending on the supersaturation threshold, the values for the aging timescales vary between 0.06 hours and 10 hours during the day, and between 6 hours and 20 hours during the night.

Riemer, Nicole; West, Matt; Zaveri, Rahul A.; Easter, Richard C.

2010-01-13

369

Time-scale separation: Michaelis and Menten's old idea, still bearing fruit  

PubMed Central

Michaelis and Menten introduced to biochemistry the idea of time-scale separation, in which part of a system is assumed to be operating sufficiently fast compared to the rest that it may be assumed to have reached a steady state. This allows, in principle, the fast components to be eliminated, resulting in a simplified description of the system's behaviour. Similar ideas have been widely used in different areas of biology, including enzyme kinetics, protein allostery, receptor pharmacology, gene regulation and post-translational modification. However, the methods used have been independent and ad hoc. Here, we review the use of time-scale separation as a means to simplify the description of molecular complexity and discuss recent work which sets out a single framework which unifies these separate calculations. The framework offers new capabilities for mathematical analysis and helps to do justice to Michaelis and Menten's insights about individual enzymes in the context of multi-enzyme biological systems. PMID:24103070

Gunawardena, Jeremy

2013-01-01

370

Book Review: A. P. French (ed.): "Einstein: A Centenary Volume" and Gerald Tauber (ed.): "Albert Einstein's Theory of General Relativity"  

E-print Network

A. P. French (ed.): Einstein: A Centenary Volume. Pp. v > 332. Cambridge, Massachusetts: Harvard University Press, 1979. Cloth, $20.00. GeraJd Tauber (ed.): Albert Einstein's Theory of Cenerai Relativity. Pp. 6 + 351. New York: Crown Publishers..., 1979. Cloth, $14.95. Joe D. Van Zandt Theie is much irony in the publication of memorial volumes in honor of Albert Einstein. Einstein repeatedly showed astonishment at the celebrity status his work had brought and often made gently rebuking...

Van Zandt, Joe D.

371

Magnetic vortex dynamics on a picosecond timescale in a hexagonal permalloy pattern  

SciTech Connect

We have observed a motion of magnetic vortex core in a hexagonal Permalloy pattern by means of Soft X-ray microscopy. Pump-probe stroboscopic observation on a picosecond timescale has been carried out after exciting a ground state vortex structure by an external field pulse of 1 ns duration. Vortex core is excited off from the center position of the hexagonal pattern but the analysis of the core trajectory reveals that the motion is nongyrotropic.

Shim, J.-H.; Kim, D.-H.; Mesler, B.; Moon, J.-H.; Lee, K.-J.; Anderson, E. H.; Fischer, P.

2009-12-02

372

Naturally rare versus newly rare: demographic inferences on two timescales inform conservation of Galápagos giant tortoises.  

PubMed

Long-term population history can influence the genetic effects of recent bottlenecks. Therefore, for threatened or endangered species, an understanding of the past is relevant when formulating conservation strategies. Levels of variation at neutral markers have been useful for estimating local effective population sizes (N e ) and inferring whether population sizes increased or decreased over time. Furthermore, analyses of genotypic, allelic frequency, and phylogenetic information can potentially be used to separate historical from recent demographic changes. For 15 populations of Galápagos giant tortoises (Chelonoidis sp.), we used 12 microsatellite loci and DNA sequences from the mitochondrial control region and a nuclear intron, to reconstruct demographic history on shallow (past ?100 generations, ?2500 years) and deep (pre-Holocene, >10 thousand years ago) timescales. At the deep timescale, three populations showed strong signals of growth, but with different magnitudes and timing, indicating different underlying causes. Furthermore, estimated historical N e of populations across the archipelago showed no correlation with island age or size, underscoring the complexity of predicting demographic history a priori. At the shallow timescale, all populations carried some signature of a genetic bottleneck, and for 12 populations, point estimates of contemporary N e were very small (i.e., < 50). On the basis of the comparison of these genetic estimates with published census size data, N e generally represented ?0.16 of the census size. However, the variance in this ratio across populations was considerable. Overall, our data suggest that idiosyncratic and geographically localized forces shaped the demographic history of tortoise populations. Furthermore, from a conservation perspective, the separation of demographic events occurring on shallow versus deep timescales permits the identification of naturally rare versus newly rare populations; this distinction should facilitate prioritization of management action. PMID:25691990

Garrick, Ryan C; Kajdacsi, Brittney; Russello, Michael A; Benavides, Edgar; Hyseni, Chaz; Gibbs, James P; Tapia, Washington; Caccone, Adalgisa

2015-02-01

373

Timescale effects in the interaction between a large and a small herbivore  

Microsoft Academic Search

In the short term, grazing will mainly affect plant biomass and forage quality. However, grazing can affect plant species composition by accelerating or retarding succession at longer time-scales. Few studies concerning interactions among herbivores have taken the change in plant species composition into account. In a salt-marsh system, the long-term effects of exclusion of a large herbivore (cattle) on the

D. P. J. Kuijper; P. Beek; S. E. van Wieren; J. P. Bakker

2008-01-01

374

Naturally rare versus newly rare: demographic inferences on two timescales inform conservation of Galápagos giant tortoises  

PubMed Central

Long-term population history can influence the genetic effects of recent bottlenecks. Therefore, for threatened or endangered species, an understanding of the past is relevant when formulating conservation strategies. Levels of variation at neutral markers have been useful for estimating local effective population sizes (Ne) and inferring whether population sizes increased or decreased over time. Furthermore, analyses of genotypic, allelic frequency, and phylogenetic information can potentially be used to separate historical from recent demographic changes. For 15 populations of Galápagos giant tortoises (Chelonoidis sp.), we used 12 microsatellite loci and DNA sequences from the mitochondrial control region and a nuclear intron, to reconstruct demographic history on shallow (past ?100 generations, ?2500 years) and deep (pre-Holocene, >10 thousand years ago) timescales. At the deep timescale, three populations showed strong signals of growth, but with different magnitudes and timing, indicating different underlying causes. Furthermore, estimated historical Ne of populations across the archipelago showed no correlation with island age or size, underscoring the complexity of predicting demographic history a priori. At the shallow timescale, all populations carried some signature of a genetic bottleneck, and for 12 populations, point estimates of contemporary Ne were very small (i.e., < 50). On the basis of the comparison of these genetic estimates with published census size data, Ne generally represented ?0.16 of the census size. However, the variance in this ratio across populations was considerable. Overall, our data suggest that idiosyncratic and geographically localized forces shaped the demographic history of tortoise populations. Furthermore, from a conservation perspective, the separation of demographic events occurring on shallow versus deep timescales permits the identification of naturally rare versus newly rare populations; this distinction should facilitate prioritization of management action.

Garrick, Ryan C; Kajdacsi, Brittney; Russello, Michael A; Benavides, Edgar; Hyseni, Chaz; Gibbs, James P; Tapia, Washington; Caccone, Adalgisa

2015-01-01

375

Fast stratocumulus adjustment timescale due to entrainment-liquid flux feedback  

NASA Astrophysics Data System (ADS)

We use a mixed-layer model (MLM) and large eddy simulation (LES) to analyze the response timescales of a stratocumulus-topped boundary layer. From the MLM, we find three separate time scales: a slow adjustment timescale associated with boundary layer deepening (on the order of several days); an intermediate timescale associated with thermodynamic adjustment of the boundary layer (approximately one day); and a fast timescale (6-12 hours) associated with entrainment rate feedbacks. We show that the fast scale is due to entrainment-liquid flux (ELF) adjustment, an internal cloud-regulating feedback between entrainment rate and the cloud liquid water path (LWP). A thicker cloud generates more turbulent kinetic energy and an increased entrainment rate which tends to warm and dry the boundary layer, thereby decreasing the cloud thickness (a negative feedback). Through this mechanism, the cloud base quickly adjusts until the entrainment rate and LWP stabilize as entrainment warming balances boundary-layer radiative cooling. We use two cases based on past model intercomparison studies to investigate the fast time scale. The first (DYCOMS RF01) involves a nocturnal stratocumulus-capped mixed layer with idealized radiative forcing. A perturbation to the free tropospheric relative humidity is shown to induce fast adjustment of cloud thickness in the MLM and also in an LES. A second case with realistic radiation used in past for cloud feedback studies (CGILS S12) is used to show that an instantaneous CO2 increase does not elicit a fast response in cloud thickness. However, an instantaneous temperature increase to the whole atmosphere-ocean column induces a cloud thinning with a few hours in both MLM and LES that largely explains the equilibrium response of the cloud layer to this forcing. This fast ELF adjustment suggests that stratocumulus cloud changes likely have a positive feedback on greenhouse warming.

Jones, C. R.; Bretherton, C. S.; Blossey, P. N.

2013-12-01

376

A Theorizing Evolution of Inter-organizational Information Systems on Long Timescales  

Microsoft Academic Search

Inter-organizational Information Systems (IOIS) are computer-based systems shared by, or connecting, several organizations. The on-going use and evolution on long timescales of these large scale socio-technical systems so far cannot be satisfactorily explained on the basis of existing theories of IS adoption, implementation and use. In this paper, we present a theory of IOIS in which the on-going use and

Kai Reimers

2008-01-01

377

Suborbital timescale variability of North Atlantic Deep Water during the past 200,000 years  

Microsoft Academic Search

We generated ~200-kyr-long proxy records of surface and deepwater variability from a subpolar North Atlantic core (V29-202), enabling us to assess the linkage between surface and deepwater changes on suborbital timescales. In particular, we use a benthic delta13C record to evaluate the deep water response to Dansgaard-Oeschger temperature oscillations and to Heinrich events, times of massive iceberg delivery to the

Delia W. Oppo; Scott J. Lehman

1995-01-01

378

Suborbital timescale variability of North Atlantic Deep Water during the past 200,000 years  

Microsoft Academic Search

We generated ?200-kyr-long proxy records of surface and deepwater variability from a subpolar North Atlantic core (V29–202), enabling us to assess the linkage between surface and deepwater changes on suborbital timescales. In particular, we used a benthic ?13C record to evaluate the deep water response to Dansgaard-Oeschger temperature oscillations and to Heinrich events, times of massive iceberg delivery to the

Delia W. Oppo; Scott J. Lehman

1995-01-01

379

North–South Precipitation Patterns in Western North America on Interannual-to-Decadal Timescales  

Microsoft Academic Search

The overall amount of precipitation deposited along the West Coast and western cordillera of North America from 258 to 558N varies from year to year, and superimposed on this domain-average variability are varying north-south contrasts on timescales from at least interannual to interdecadal. In order to better understand the north-south precipitation contrasts, their interannual and decadal variations are studied in

Michael D. Dettinger; Daniel R. Cayan; Henry F. Diaz; David M. Meko

1998-01-01

380

Oceanic Climate Variability at Millennial Time-Scales: Models of Climate Connections  

Microsoft Academic Search

One of the most exciting questions in palaeoclimatology is the study of the complex interactions between the different components\\u000a of the climate system in order to understand how climate changes occur at Milankovitch as well as at millennial and centennial\\u000a time-scales. The primary objective of this paper is to place the PEP III transect palaeo-data within a global climate context

Laurence Vidal; Helge Arz

381

Vacuumless cosmic strings in Einstein Cartan theory  

E-print Network

The gravitational fields of vacuumless global and gauge strings have been investigated in the context of Einstein Cartan theory under the weak field assumption of the field equations. It has been shown that global string and gauge string can have only repulsive gravitational effect on a test particle.

F. Rahaman; B. C. Bhui; A Ghosh; R. Mondal

2006-10-20

382

Skyrme-Einstein closed cosmic chiral strings  

SciTech Connect

Within the theory of general relativity, the configuration of a closed string (vortex) characterized by a topological charge of the degree type is described for the Skyrme-Einstein SU (2) chiral model. In the approximation of a large vortex-closure radius (a), a solution to equations of motion is obtained, along with estimates for the vortex energy and radius.

Rybakov, Yu. P., E-mail: soliton4@mail.ru; Ivanova, I. S. [Peoples' Friendship University (Russian Federation)

2007-07-15

383

Soliton resonance in Bose–Einstein condensate  

Microsoft Academic Search

A new phenomenon in nonlinear dispersive systems, including a Bose–Einstein condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and “eigen-solitons” of the homogeneous cubic Schrödinger equation. There have been shown that a moving source of positive\\/negative potential induces bright\\/dark solitons in an attractive\\/repulsive Bose condensate.

Michail Zak; Igor Kulikov

2003-01-01

384

New Information about Albert Einstein's Brain  

PubMed Central

In order to glean information about hominin (or other) brains that no longer exist, details of external neuroanatomy that are reproduced on endocranial casts (endocasts) from fossilized braincases may be described and interpreted. Despite being, of necessity, speculative, such studies can be very informative when conducted in light of the literature on comparative neuroanatomy, paleontology, and functional imaging studies. Albert Einstein's brain no longer exists in an intact state, but there are photographs of it in various views. Applying techniques developed from paleoanthropology, previously unrecognized details of external neuroanatomy are identified on these photographs. This information should be of interest to paleoneurologists, comparative neuroanatomists, historians of science, and cognitive neuroscientists. The new identifications of cortical features should also be archived for future scholars who will have access to additional information from improved functional imaging technology. Meanwhile, to the extent possible, Einstein's cerebral cortex is investigated in light of available data about variation in human sulcal patterns. Although much of his cortical surface was unremarkable, regions in and near Einstein's primary somatosensory and motor cortices were unusual. It is possible that these atypical aspects of Einstein's cerebral cortex were related to the difficulty with which he acquired language, his preference for thinking in sensory impressions including visual images rather than words, and his early training on the violin. PMID:19597545

Falk, Dean

2009-01-01

385

Gravity: An Introduction to Einstein's General Relativity  

NSDL National Science Digital Library

This text is an introductory textbook to general relativity at the upper undergraduate level using a 'physics first' approach. The simplest solutions of the Einstein equation are presented first without derivation and are applied to astrophysical situations like black holes, gravitational radiation, and the big bang.

Hartle, James B.

2009-06-12

386

Soliton resonance in bose-einstein condensate  

NASA Technical Reports Server (NTRS)

A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.

Zak, Michail; Kulikov, I.

2002-01-01

387

The Einstein All-Sky Slew Survey  

NASA Technical Reports Server (NTRS)

The First Einstein IPC Slew Survey produced a list of 819 x-ray sources, with f(sub x) approximately 10(exp -12) - 10(exp -10) erg/sq cm s and positional accuracy of approximately 1.2 feet (90 percent radius). The aim of this program was to identify these x-ray sources.

Elvis, Martin S.

1992-01-01

388

Einstein Observations of Galactic supernova remnants  

NASA Technical Reports Server (NTRS)

This paper summarizes the observations of Galactic supernova remnants with the imaging detectors of the Einstein Observatory. X-ray surface brightness contours of 47 remnants are shown together with gray-scale pictures. Count rates for these remnants have been derived and are listed for the HRI, IPC, and MPC detectors.

Seward, Frederick D.

1990-01-01

389

Einstein Slew Survey: Data analysis innovations  

NASA Technical Reports Server (NTRS)

Several new methods were needed in order to make the Einstein Slew X-ray Sky Survey. The innovations which enabled the Slew Survey to be done are summarized. These methods included experimental approach to large projects, parallel processing on a LAN, percolation source detection, minimum action identifications, and rapid dissemination of the whole data base.

Elvis, Martin S.; Plummer, David; Schachter, Jonathan F.; Fabbiano, G.

1992-01-01

390

Einstein's Revolutionary Light--Quantum Hypothesis  

Microsoft Academic Search

Albert Einstein's light-quantum paper was the only one of his great papers of 1905 that he himself called ``very revolutionary''. I sketch his arguments for light quanta, his analysis of the photoelectric effect, and his introduction of the wave-particle duality into physics in 1909. I show that Robert Andrews Millikan, in common with almost all physicists at the time, rejected

R. H. Stuewer

2006-01-01

391

A Science of Sig-Einstein, Inertia,  

E-print Network

12 A Science of Sig- nals: Einstein, Inertia, and the Postal System Jimena Canales What do) with communications me- dia, and, in particular, with their speed. Could love be sent through the mail?, wondered in general. In the process, he learned that neither love nor time could travel at speeds faster than

Canales, Jimena

392

An operationalistic reformulation of Einstein's equivalence principle  

E-print Network

The Einstein's equivalence principle is formulated in terms of the accuracy of measurements and its dependence of the size of the area of measurement. It is shown that different refinements of the statement 'the spacetime is locally flat' lead to different conculsions about the spacetime geometry.

Vladik Kreinovich; R. R. Zapatrin

1997-05-30

393

Albert Einstein and the Quantum Riddle  

ERIC Educational Resources Information Center

Derives a systematic structure contributing to the solution of the quantum riddle in Einstein's sense by deducing quantum mechanics from the postulates of symmetry, correspondence, and covariance. Indicates that the systematic presentation is in agreement with quantum mechanics established by Schroedinger, Born, and Heisenberg. (CC)

Lande, Alfred

1974-01-01

394

DESIGN ANALYSIS OF THE EINSTEIN REFRIGERATION CYCLE  

Microsoft Academic Search

After developing the theory of relativity, Albert Einstein spent several years working with Leo Szilard on absorption refrigeration cycles. In 1930, they obtained a U.S. patent for a unique single pressure absorption cycle. The single pressure eliminates the need for a solution pump. Their cycle has only recently been rediscovered. The cycle u tilizes butane as its refrigerant, ammonia as

Sam V. Shelton; Andrew Delano; Laura A. Schaefer

1998-01-01

395

Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing - Part 2  

NASA Technical Reports Server (NTRS)

Evaluation of metals to predict service life of metal-based structures in corrosive environments has long relied on atmospheric exposure test sites. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions similar to those of the corrosive environment. Their reliability to correlate to atmospheric exposure test results is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated corrosion testing has yet to be universally accepted as a useful tool in predicting the long-term service life of a metal, despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard, and their use is crucial, a method that correlates timescales from accelerated testing to atmospheric exposure would be very valuable. This paper presents work that began with the characterization of the atmospheric environment at the Kennedy Space Center (KSC) Beachside Corrosion Test Site. The chemical changes that occur on low carbon steel, during atmospheric and accelerated corrosion conditions, were investigated using surface chemistry analytical methods. The corrosion rates and behaviors of panels subjected to long-term and accelerated corrosion conditions, involving neutral salt fog and alternating seawater spray, were compared to identify possible timescale correlations between accelerated and long-term corrosion performance. The results, as well as preliminary findings on the correlation investigation, are presented.

Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerome C.; Kolody, Mark R.

2012-01-01

396

THE RESPONSE OF GIANT STARS TO DYNAMICAL-TIMESCALE MASS LOSS  

SciTech Connect

We study the response of giant stars to mass loss. One-dimensional simulations of red and asymptotic giant branch stars with mass loss rates from 10{sup -3} up to a few M {sub Sun }yr{sup -1} show in no case any significant radius increase. The largest radius increase of 0.2% was found in the case with the lowest mass loss rate. For dynamical-timescale mass loss rates that may be encountered during a common envelope phase, the evolution is not adiabatic. The superadiabatic outer layer of the giant's envelope has a local thermal timescale comparable to the dynamical timescale. Therefore, this layer has enough time to readjust thermally. Moreover, the giant star is driven out of hydrostatic equilibrium and evolves dynamically. In these cases no increase of the stellar radius with respect to its initial value is found. If the mass loss rate is high enough, the superadiabaticity of the outer layer is lost progressively and a radiative zone forms due to a combination of thermal and dynamical readjustment. Conditions for unstable mass transfer based on adiabatic mass loss models that predict a significant radius increase may need to be re-evaluated.

Passy, Jean-Claude; Herwig, Falk [Department of Physics and Astronomy, University of Victoria, Victoria, BC (Canada); Paxton, Bill [Kavli Institute for Theoretical Physics, UC Santa Barbara, CA (United States)

2012-11-20

397

Time-scale and state dependence of the carbon-cycle feedback to climate  

NASA Astrophysics Data System (ADS)

Climate and atmospheric CO2 concentration are intimately coupled in the Earth system: CO2 influences climate through the greenhouse effect, but climate also affects CO2 through its impact on the amount of carbon stored on land and in the ocean. The change in atmospheric CO2 as a response to a change in temperature () is a useful measure to quantify the feedback between the carbon cycle and climate. Using an ensemble of experiments with an Earth system model of intermediate complexity we show a pronounced time-scale dependence of . A maximum is found on centennial scales with values for the model ensemble in the range 5-12 ppm °C-1, while lower values are found on shorter and longer time scales. These results are consistent with estimates derived from past observations. Up to centennial scales, the land carbon response to climate dominates the CO2 signal in the atmosphere, while on longer time scales the ocean becomes important and eventually dominates on multi-millennial scales. In addition to the time-scale dependence, modeled show a distinct dependence on the initial state of the system. In particular, on centennial time-scales, high values are correlated with high initial land carbon content. A similar relation holds also for the CMIP5 models, although for computed from a very different experimental setup. The emergence of common patterns like this could prove to usefully constrain the climate-carbon cycle feedback.

Willeit, Matteo; Ganopolski, Andrey; Dalmonech, Daniela; Foley, Aideen M.; Feulner, Georg

2014-04-01

398

Layered decomposition for the model order reduction of timescale separated biochemical reaction networks.  

PubMed

Biochemical reaction networks tend to exhibit behaviour on more than one timescale and they are inevitably modelled by stiff systems of ordinary differential equations. Singular perturbation is a well-established method for approximating stiff systems at a given timescale. Standard applications of singular perturbation partition the state variable into fast and slow modules and assume a quasi-steady state behaviour in the fast module. In biochemical reaction networks, many reactants may take part in both fast and slow reactions; it is not necessarily the case that the reactants themselves are fast or slow. Transformations of the state space are often required in order to create fast and slow modules, which thus no longer model the original species concentrations. This paper introduces a layered decomposition, which is a natural choice when reaction speeds are separated in scale. The new framework ensures that model reduction can be carried out without seeking state space transformations, and that the effect of the fast dynamics on the slow timescale can be described directly in terms of the original species. PMID:24732263

Prescott, Thomas P; Papachristodoulou, Antonis

2014-09-01

399

Match and mismatch: conservation physiology, nutritional ecology and the timescales of biological adaptation  

PubMed Central

Conservation physiology (CP) and nutritional ecology (NE) are both integrative sciences that share the fundamental aim of understanding the patterns, mechanisms and consequences of animal responses to changing environments. Here, we explore the high-level similarities and differences between CP and NE, identifying as central themes to both fields the multiple timescales over which animals adapt (and fail to adapt) to their environments, and the need for integrative models to study these processes. At one extreme are the short-term regulatory responses that modulate the state of animals in relation to the environment, which are variously considered under the concepts of homeostasis, homeorhesis, enantiostasis, heterostasis and allostasis. In the longer term are developmental responses, including phenotypic plasticity and transgenerational effects mediated by non-genomic influences such as parental physiology, epigenetic effects and cultural learning. Over a longer timescale still are the cumulative genetic changes that take place in Darwinian evolution. We present examples showing how the adaptive responses of animals across these timescales have been represented in an integrative framework from NE, the geometric framework (GF) for nutrition, and close with an illustration of how GF can be applied to the central issue in CP, animal conservation. PMID:22566672

Raubenheimer, David; Simpson, Stephen J.; Tait, Alice H.

2012-01-01

400

Exchanged ridge demodulation of time-scale manifold for enhanced fault diagnosis of rotating machinery  

NASA Astrophysics Data System (ADS)

The vibration or acoustic signal from rotating machinery with localized fault usually behaves as the form of amplitude modulation (AM) and/or frequency modulation (FM). The demodulation techniques are conventional ways to reveal the fault characteristics from the analyzed signals. One of these techniques is the time-scale manifold (TSM) ridge demodulation method with the merits of good time-frequency localization and in-band noise suppression properties. However, due to the essential attribute of wavelet ridge, the survived in-band noise on the achieved TSM will still disturb the envelope extraction of fault-induced impulses. This paper presents an improved TSM ridge demodulation method, called exchanged ridge demodulation of TSM, by combining the benefits of the first two TSMs: the noise suppression of the first TSM and the noise separation of the second TSM. Specifically, the ridge on the second TSM can capture the fault-induced impulses precisely while avoiding the in-band noise smartly. By putting this ridge on the first TSM, the corresponding instantaneous amplitude (IA) waveform can represent the real envelope of pure faulty impulses. Moreover, an adaptive selection method for Morlet wavelet parameters is also proposed based on the smoothness index (SI) in the time-scale domain for an optimal time-scale representation of analyzed signal. The effectiveness of the proposed method is verified by means of a simulation study and applications to diagnosis of bearing defects and gear fault.

Wang, Jun; He, Qingbo

2014-05-01

401

Multiple time-scales and the developmental dynamics of social systems.  

PubMed

To build a theory of social complexity, we need to understand how aggregate social properties arise from individual interaction rules. Here, I review a body of work on the developmental dynamics of pigtailed macaque social organization and conflict management that provides insight into the mechanistic causes of multi-scale social systems. In this model system coarse-grained, statistical representations of collective dynamics are more predictive of the future state of the system than the constantly in-flux behavioural patterns at the individual level. The data suggest that individuals can perceive and use these representations for strategical decision-making. As an interaction history accumulates the coarse-grained representations consolidate. This constrains individual behaviour and provides the foundations for new levels of organization. The time-scales on which these representations change impact whether the consolidating higher-levels can be modified by individuals and collectively. The time-scales appear to be a function of the 'coarseness' of the representations and the character of the collective dynamics over which they are averages. The data suggest that an advantage of multiple timescales is that they allow social systems to balance tradeoffs between predictability and adaptability. I briefly discuss the implications of these findings for cognition, social niche construction and the evolution of new levels of organization in biological systems. PMID:22641819

Flack, Jessica C

2012-07-01

402

Long-timescale motions in glycerol-monopalmitate lipid bilayers investigated using molecular dynamics simulation.  

PubMed

The occurrence of long-timescale motions in glycerol-1-monopalmitate (GMP) lipid bilayers is investigated based on previously reported 600ns molecular dynamics simulations of a 2×8×8 GMP bilayer patch in the temperature range 302-338K, performed at three different hydration levels, or in the presence of the cosolutes methanol or trehalose at three different concentrations. The types of long-timescale motions considered are: (i) the possible phase transitions; (ii) the precession of the relative collective tilt-angle of the two leaflets in the gel phase; (iii) the trans-gauche isomerization of the dihedral angles within the lipid aliphatic tails; and (iv) the flipping of single lipids across the two leaflets. The results provide a picture of GMP bilayers involving a rich spectrum of events occurring on a wide range of timescales, from the 100-ps range isomerization of single dihedral angles, via the 100-ns range of tilt precession motions, to the multi-?s range of phase transitions and lipid-flipping events. PMID:25437095

Laner, Monika; Horta, Bruno A C; Hünenberger, Philippe H

2015-02-01

403

Multi-timescale event-scheduling in multi-agent immune simulation models.  

PubMed

Multi-agent (or MA) -based design approaches have received much research attention lately for modeling immunological systems due to their efficacy in representing non-heterogeneous behaviors in the population under dynamic environmental and topological conditions. The update scheme of a MA model refers to the frequency of agent state updates and how these are related in temporal order. In contrast to verifiable agent behavioral rules at the individual level, the update scheme is a design decision made by the model developer at the systems level that is subject to realism and computational efficiency issues that directly affect the credibility and the usefulness of the simulation results. Previous works have mainly focused on the issue of realism with respect to synchrony of updates but have often overlooked the necessary heterogeneity in update frequencies due to multi-timescales in immunological phenomena. To incorporate such multi-timescales for realism, the efficiency of the update scheme arises as a nontrivial issue. An event-scheduling based asynchronous update scheme has the advantage of allowing arbitrary smaller timescales for realism and avoiding unnecessary execution and delays to achieve efficiency. In this paper we present the application of the event-scheduling update scheme to realistically model the B cell life cycle, and empirically compare its simulation performance with the widely adopted uniform time-step update scheme. The simulation results show a significantly reduced execution time (40 times faster) and also reveal the conditions where the event-scheduling update scheme is superior. PMID:17919809

Guo, Zaiyi; Tay, Joc Cing

2008-01-01

404

Interpolation methods for Antarctic ice-core timescales: application to Byrd, Siple Dome and Law Dome ice cores  

NASA Astrophysics Data System (ADS)

Antarctic ice cores have often been dated by matching distinctive features of atmospheric methane to those detected in annually dated ice cores from Greenland. Establishing the timescale between these tie-point ages requires interpolation. While the uncertainty at tie points is relatively well described, uncertainty of the interpolation is not. Here we assess the accuracy of three interpolation schemes using data from the WAIS Divide ice core in West Antarctica; we compare the interpolation methods with the annually resolved timescale for the past 30 kyr. Linear interpolation yields large age errors (up to 380 years) between tie points, abrupt changes in duration of climate events at tie points, and an age bias. Interpolations based on the smoothest accumulation rate (ACCUM) or the smoothest annual-layer thickness (ALT) yield timescales that more closely agree with the annually resolved timescale and do not have abrupt changes in duration at tie points. We use ALT to assess the uncertainty in existing timescales for the past 30 kyr from Byrd, Siple Dome, and Law Dome. These ice-core timescales were developed with methods similar to linear interpolation. Maximum age differences exceed 1000 years for Byrd and Siple Dome, and 500 years for Law Dome. For the glacial-interglacial transition (21 to 12 kyr), the existing timescales are, on average, older than ALT by 40 years for Byrd, 240 years for Siple Dome, and 150 years for Law Dome. Because interpolation uncertainty is often not considered, age uncertainties for ice-core records are often underestimated.

Fudge, T. J.; Waddington, E. D.; Conway, H.; Lundin, J. M. D.; Taylor, K.

2014-06-01

405

Timescales and topographic expression of lithospheric extension in the western Great Basin, NV, USA  

NASA Astrophysics Data System (ADS)

One of the goals of the Plate Boundary Observatory is to determine how continental lithosphere responds to changes in driving forces. Because many geodynamic processes occur on timescales much longer than geodetic recording time intervals, longer term deformation measurements are required. On what timescale, however, should these longer term (geological) measurements be made to allow a meaningful integration with geodetic time series? Traditional geological and tectonic studies appear to indicate that continental fault systems are active continuously for millions of years, whereas more precise paleoseismological measurements often document irregular fault displacement. In order to study the evolution of individual fault systems, measurements are needed on an intermediate timescale: long enough to average over many seismic cycles, but short enough to provide the incremental strain history. For continental fault systems such as those of the Basin and Range Province (c. 10 nstrain at present, e.g., Bennett et al., TECTONICS 2003, Friedrich et al., JGR 2003), the expected time interval is on the order of a few hundred thousand years and the expected signal size should range from several to a few hundred meters. In climatically sensitive regions, such as the Great Basin, such surface deformation features (fault trace in alluvial sediments, triangular facets, etc.) may, on one hand, be preserved extremelly well over several hundred thousand years; On the other hand, however, such regions are also sensitive to weather extremes and medium-term climatic variations (tens of ka) as exhibited during wet periods. In the Great Basin, both cases are represented. For example, (1) on the 10 ka timescale, many internally drained basins filled to large lakes (Bonneville and Lahontan) which left thick sedimentary sections covering most pre-existing fault traces; and (2) on the 500 ka timescale, growth or reactivation of faults affected drainage, erosion and deposition patterns. We document such tectonogeomorphic features along the W-flank of the Shoshone Range and Cortez Mountains and surrounding region. We speculate that these features are the expression of active crustal or lithospheric thinning.

Friedrich, A. M.; Gaudemer, Y.; King, G.; Armijo, R.; Strecker, M.

2004-12-01

406

The Global Water Cycle Drives Volcanism on Seasonal to Millennial Timescales  

NASA Astrophysics Data System (ADS)

Global rates of occurrence of volcanic eruptions show periodic behaviour on timescales ranging from <1 yr (seasonal) to >106 years. At long timescales (>106 to 107 years), rates of eruption are controlled by plate tectonics. At shorter timescales, the periodic nature of volcanism is forced by the global water cycle. Historical records of the rates of onset of eruption for the past 300 years are dominated by small-scale activity at a number of persistently, or repeatedly, active volcanoes around the world. This record shows statistically significant evidence for `seasonality': globally, rates of eruption are about 18% higher during northern hemisphere winter than northern hemisphere summer. This pattern of seasonality is strong for volcanoes at high northern latitudes; but also exists for volcanic regions in the southern hemisphere (e.g. Chile) and at specific volcanoes (e.g. Sakurajima, Japan). Seasonality is weak at certain ocean-island volcanoes (e.g. Hawaii), and certain volcanic regions (e.g. Mediterranean). The only external parameters that account for the periodic nature of small-scale volcanism (i.e. the observation that eruption rates peak between November and March in both hemispheres) are those related to the global water cycle. Movement of water (including atmospheric vapour; soil moisture; snow and ice) between the northern-hemisphere continents and the world's oceans is responsible for an annual deformation of Earth's surface that is weakly defined in equatorial regions, and stronger at higher latitudes. This external modulation of the Earth's surface has an amplitude of the order of centimetres, and an associated (vertical) strain rate of ~ 10-16 s-1. This deformation is slow enough to be felt by the Earth's interior, and is of the same order of magnitude as the (horizontal) strain rates experienced in tectonically active continental regions. This modulation effectively applies a time-dependence to the `threshold' point at which a volcano will begin to erupt. In this way, the subtle, small-magnitude but long-wavelength changes associated with the annual hydrological cycle leads to clustering of volcanic eruptions. Peaks of eruption onset are associated with periods of changing sea-level or atmospheric pressure, rather than with the maxima or minima. Longer timescale (> 103 year) variability in rates of volcanism during the Pleistocene, associated with large scale climatic changes, is evident in long-term terrestrial and ice-core records of volcanism. Linkage between the global hydrological cycle and volcanism over annual to millennial timescales plays an important role in land-atmosphere coupling by modulating volcanic emissions and, thereby, the volcanic component of climate forcing.

Pyle, D. M.; Mason, B. G.; Jupp, T. E.; Dade, W. B.

2005-05-01

407

Filling a 30 Million Year Gap: Radioisotopic Age Constraints for the Late Triassic Timescale  

NASA Astrophysics Data System (ADS)

The Triassic Period records a critical interval of Phanerozoic Earth history, including major paleoenvironmental changes in a greenhouse world, recovery from one mass extinction and the onset of another, and the origin of modern terrestrial ecosystems. Recent efforts have been instrumental in calibrating the timing of these events by producing numerous high resolution radioisotopic ages from Early and Middle Triassic marine strata that facilitate building of a robust 20 Ma chronostratigraphic framework. This contrasts starkly with the Late Triassic (Carnian, Norian, and Rhaetian stages), where ~30 Ma of the timescale is virtually uncalibrated by high-resolution radioisotopic data. This is the only interval of such long duration in the Mesozoic or Cenozoic that remains so poorly constrained by reliable absolute ages, despite the occurrence of major events such as the origin and early diversification of dinosaurs, major reef building episodes in marine ecosystems, key paleoenvironmental changes (e.g., Carnian Pluvial Event), and large extraterrestrial bolide impacts (e.g., Manicouagan). An additional challenge is that the biostratigraphically-defined marine timescale cannot be applied globally, so that other areas (e.g., New Zealand) have independent timescales that cannot be confidently correlated to classic Laurasian sections. All of these problems preclude formulating robust first-order hypotheses about the Late Triassic world. We present new CA-TIMS U-Pb zircon data from volcaniclastic units within both marine and terrestrial strata that aim at calibrating the timescale itself and as a result constrain the timing of some of these major events in Earth history. Several preliminary ages support the hypothesis that the Norian Stage was very long, ~20 Ma. Our new data from marine sequences in New Zealand demonstrate that the timescale divisions there do not correlate directly with biostratigraphic boundaries in the Tethys; specifically, the Ladinian-Carnian boundary is somewhere within the Kaihikuan biozone, and the lower Otamitan biozone is correlative with the mid-Norian. Our new data from the terrestrial Chinle Formation in the southwestern US demonstrate that all of this formation is Norian in age or later, younger than South American sequences it had previously been correlated with. This supports the hypothesis that the rise of dinosaurs was diachronous, occurring later in North America than in Argentina and Brazil. These new ages also constrain a major faunal turnover event in the middle Chinle Fm to the mid-Norian, close in age to the Manicouagan impact event. Correlation and calibration of these major events will be further strengthened by the unambiguous superposition provided by core samples, such as the forthcoming Colorado Plateau Coring Project.

Irmis, R. B.; Mundil, R.

2011-12-01

408

Biographies of Albert Einstein -- Mastermind of Theoretical Physics  

E-print Network

Over the years many have written biographies of Einstein. They all based their biographies on primary sources, archival material: memories and letters of people who were in contact with Einstein, Einstein's own recollections; interviews that Einstein had given over the years, and letters of Einstein to his friends - youth friends like Marcel Grossman and Michele Besso and later friends and colleagues like Heinrich Zangger; and especially his love letters with Mileva Mari\\'c. One can demarcate between two types of biographies, namely, Documentary biographies, and, Non-documentary biographies. Non-documentary biographies were written by people who based themselves on documentary biographies and on other non-documentary biographies. Documentary biographies were written by people who knew Einstein personally, and received information from him and from other people who were in personal contact with him. This type can be further divided into two subgroups: books that were written while Einstein was still alive, and...

Weinstein, Galina

2012-01-01

409

From Navier-Stokes to Einstein  

NASA Astrophysics Data System (ADS)

We show by explicit construction that for every solution of the incompressible Navier-Stokes equation in p + 1 dimensions, there is a uniquely associated "dual" solution of the vacuum Einstein equations in p + 2 dimensions. The dual geometry has an intrinsically flat timelike boundary segment ?c whose extrinsic curvature is given by the stress tensor of the Navier-Stokes fluid. We consider a "near-horizon" limit in which ?c becomes highly accelerated. The near-horizon expansion in gravity is shown to be mathematically equivalent to the hydrodynamic expansion in fluid dynamics, and the Einstein equation reduces to the incompressible Navier-Stokes equation. For p = 2, we show that the full dual geometry is algebraically special Petrov type II. The construction is a mathematically precise realization of suggestions of a holographic duality relating fluids and horizons which began with the membrane paradigm in the 70's and resurfaced recently in studies of the AdS/CFT correspondence.

Bredberg, Irene; Keeler, Cynthia; Lysov, Vyacheslav; Strominger, Andrew

2012-07-01

410

Bose-Einstein Condensation of Pions  

E-print Network

Particle number fluctuations are studied in the ideal pion gas approaching Bose-Einstein condensation. Two different cases are considered: Bose condensation of pions at large charge densities $\\rho_Q$ and Bose condensation at large total densities of pions $\\rho_{\\pi}$. Calculations are done in grand canonical, canonical and microcanonical ensembles. At high collision energy, in the samples of events with a fixed number of all pions, $N_{\\pi}$, one may observe a prominent signal. When $N_{\\pi}$ increases the scaled variances for particle number fluctuations of both neutral and charged pions increase dramatically in the vicinity of the Bose-Einstein condensation line. As an example, the estimates are presented for $p+p$ collisions at the beam energy of 70 GeV.

Viktor Begun; Mark Gorenstein

2007-09-10

411

The Geroch group in Einstein spaces  

NASA Astrophysics Data System (ADS)

Geroch's solution-generating method is extended to the case of Einstein spaces, which possess a Killing vector and are thus asymptotically (locally) (anti) de Sitter. This includes the reduction to a three-dimensional coset space, the description of the dynamics in terms of a sigma-model and its transformation properties under the SL(2,{R}) group, and the reconstruction of new four-dimensional Einstein spaces. The detailed analysis of the space of solutions is performed using the Hamilton-Jacobi method in the instance where the three-dimensional coset space is conformal to {R}× {{S}2}. The cosmological constant appears in this framework as a constant of motion and transforms under SL(2,{R}).

Leigh, Robert G.; Petkou, Anastasios C.; Marios Petropoulos, P.; Tripathy, Prasanta K.

2014-11-01

412

Axions: Bose Einstein Condensate or Classical Field?  

E-print Network

The axion is a motivated dark matter candidate, so it would be interesting to find features in Large Scale Structures specific to axion dark matter. Such features were proposed for a Bose Einstein condensate of axions, leading to confusion in the literature (to which I contributed) about whether axions condense due to their gravitational interactions. This note argues that the Bose Einstein condensation of axions is a red herring: the axion dark matter produced by the misalignment mechanism is already a classical field, which has the distinctive features attributed to the axion condensate (BE condensates are described as classical fields). This note also estimates that the rate at which axion particles condense to the field, or the field evaporates to particles, is negligeable.

Sacha Davidson

2014-05-06

413

Taming the Nonlinearity of the Einstein Equation  

NASA Astrophysics Data System (ADS)

Many of the technical complications associated with the general theory of relativity ultimately stem from the nonlinearity of Einstein's equation. It is shown here that an appropriate choice of dynamical variables may be used to eliminate all such nonlinearities beyond a particular order: Both Landau-Lifshitz and tetrad formulations of Einstein's equation are obtained that involve only finite products of the unknowns and their derivatives. Considerable additional simplifications arise in physically interesting cases where metrics become approximately Kerr or, e.g., plane waves, suggesting that the variables described here can be used to efficiently reformulate perturbation theory in a variety of contexts. In all cases, these variables are shown to have simple geometrical interpretations that directly relate the local causal structure associated with the metric of interest to the causal structure associated with a prescribed background. A new method to search for exact solutions is outlined as well.

Harte, Abraham I.

2014-12-01

414

Two Versions of Gravity: Newton and Einstein  

NSDL National Science Digital Library

The goal of this lesson is for two groups of students to exchange information (e.g., through poster presentations, Podcasts, debates, or PowerPoint presentations) about how two different theories explain a natural phenomenon: Newton's Law of Gravitation and Einstein's General Theory of Relativity. The lesson will also illustrate how the scientific process allows a new, more complete theory to take the place of an older theory that does not produce accurate results for a new discovery. Students will need to have either studied both Newton's Law of Gravitation and Einstein's Theory of Relativity or be given the time and resources to look up this information. This lesson is part of the Cosmic Times teachers guide and is intended to be used in conjunction with the 1919 Cosmic Times Poster.

415

Proper conformal symmetries in SD Einstein spaces  

E-print Network

Proper conformal symmetries in self-dual (SD) Einstein spaces are considered. It is shown, that such symmetries are admitted only by the Einstein spaces of the type [N]x[N]. Spaces of the type [N]x[-] are considered in details. Existence of the proper conformal Killing vector implies existence of the isometric, covariantly constant and null Killing vector. It is shown, that there are two classes of [N]x[-]-metrics admitting proper conformal symmetry. They can be distinguished by analysis of the associated anti-self-dual (ASD) null strings. Both classes are analyzed in details. The problem is reduced to single linear PDE. Some general and special solutions of this PDE are presented.

Adam Chudecki; Michal Dobrski

2014-03-07

416

Taming the nonlinearity of the einstein equation.  

PubMed

Many of the technical complications associated with the general theory of relativity ultimately stem from the nonlinearity of Einstein's equation. It is shown here that an appropriate choice of dynamical variables may be used to eliminate all such nonlinearities beyond a particular order: Both Landau-Lifshitz and tetrad formulations of Einstein's equation are obtained that involve only finite products of the unknowns and their derivatives. Considerable additional simplifications arise in physically interesting cases where metrics become approximately Kerr or, e.g., plane waves, suggesting that the variables described here can be used to efficiently reformulate perturbation theory in a variety of contexts. In all cases, these variables are shown to have simple geometrical interpretations that directly relate the local causal structure associated with the metric of interest to the causal structure associated with a prescribed background. A new method to search for exact solutions is outlined as well. PMID:25615299

Harte, Abraham I

2014-12-31

417

Albert Einstein - Chief Engineer of the Universe: 100 Authors for Einstein Essays  

NASA Astrophysics Data System (ADS)

In 1905, Albert Einstein published five scientific articles that fundamentally changed the world-view of physics: The Special Theory of Reativity revolutionized our concept of space and time, E=mc² became the best-known equation in physics. On the occasion of the 100th aniversary of his "annus mirabilis" 1905, the UNESCO declared the year 2005 the "World Year of Physics", in order to draw attention to the impact of physics. The Max Planck Institute for the history of science dedicates an exhibition in the Kronprinzenpalais in Berlin to the probably most important scientist of the 20th century. In this book, 100 authors explain the historical background of Einstein's life and work, shed light on many different aspects of his biography, and on the scientific fields and topics that are connected to Einstein's work. The authors are some of the most renowned Einstein researchers in the world, such as Jürgen Ehlers, Peter Galison, Zeev Rosenkranz, John Stachel and Robert Schulmann. The essays form a bridge between scientific and cultural history, opening up a perspective on Einstein's biography which goes beyond the traditional picture of the exceptional science genius.

Renn, Jürgen

2005-09-01

418

Scattering amplitudes in Maxwell-Einstein and Yang-Mills/Einstein supergravity  

NASA Astrophysics Data System (ADS)

We expose a double-copy structure in the scattering amplitudes of the generic Jordan family of Maxwell-Einstein and Yang-Mills/Einstein supergravity theories in four and five dimensions. The Maxwell-Einstein supergravity amplitudes are obtained through the color/kinematics duality as a product of two gauge-theory factors; one originating from pure super-Yang-Mills theory and the other from the dimensional reduction of a bosonic higher-dimensional pure Yang-Mills theory. We identify a specific symplectic frame in four dimensions for which the on-shell fields and amplitudes from the double-copy construction can be identified with the ones obtained from the supergravity Lagrangian and Feynman-rule computations. The Yang-Mills/Einstein supergravity theories are obtained by gauging a compact subgroup of the isometry group of their Maxwell-Einstein counterparts. For the generic Jordan family this process is identified with the introduction of cubic scalar couplings on the bosonic gauge-theory side, which through the double copy are responsible for the non-abelian vector interactions in the supergravity theory. As a demonstration of the power of this structure, we present explicit computations at tree-level and one loop. The double-copy construction allows us to obtain compact expressions for the supergravity superamplitudes, which are naturally organized as polynomials in the gauge coupling constant.

Chiodaroli, Marco; Günaydin, Murat; Johansson, Henrik; Roiban, Radu

2015-01-01

419

Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano.  

PubMed

Caldera-forming volcanic eruptions are low-frequency, high-impact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days, with devastating effects on local and global scales. Because no such eruption has been monitored during its long build-up phase, the precursor phenomena are not well understood. Geophysical signals obtained during recent episodes of unrest at calderas such as Yellowstone, USA, and Campi Flegrei, Italy, are difficult to interpret, and the conditions necessary for large eruptions are poorly constrained. Here we present a study of pre-eruptive magmatic processes and their timescales using chemically zoned crystals from the 'Minoan' caldera-forming eruption of Santorini volcano, Greece, which occurred in the late 1600s BC. The results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption. Despite the large volume of erupted magma (40-60 cubic kilometres), and the 18,000-year gestation period between the Minoan eruption and the previous major eruption, most crystals in the Minoan magma record processes that occurred less than about 100 years before the eruption. Recharge of the magma reservoir by large volumes of silicic magma (and some mafic magma) occurred during the century before eruption, and mixing between different silicic magma batches was still taking place during the final months. Final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period, with major growth phases immediately before eruption. These observations have implications for the monitoring of long-dormant, but potentially active, caldera systems. PMID:22297973

Druitt, T H; Costa, F; Deloule, E; Dungan, M; Scaillet, B

2012-02-01

420

An 8 h characteristic time-scale in submillimetre light curves of Sagittarius A*  

NASA Astrophysics Data System (ADS)

We compile and analyse long-term (?10 yr) submillimetre (submm - 1.3, 0.87, 0.43 mm) wavelength light curves of the Galactic Centre black hole, Sagittarius A*. The 0.87 and 0.43 mm data are taken from the literature, while the majority of the 1.3 mm light curve is from previously unpublished SMA and CARMA data. We show that on minute to a few hour time-scales, the variability is consistent with a red noise process with a 230 GHz power-spectrum slope of ? =2.3^{+0.8}_{-0.6} at 95 per cent confidence. The light curve is decorrelated (white noise) on long (month to year) times. We measure a transition time between red and white noise of ? = 8_{-4}^{+3} h at 230 GHz at 95 per cent confidence, with consistent results at 345 and 690 GHz. This corresponds to ?10 orbital times or ?1 inflow (viscous) time at R = 3Rs, a typical radius producing the 230 GHz emission as measured by very long baseline interferometry and found in theoretical accretion flow and jet models. This time-scale is shorter (longer) than those measured by some analyses of radio (near-infrared) light curves. It is roughly consistent with the analogous time-scale inferred in studies of quasar optical light curves after accounting for the difference in emission radius. We find evidence that the submm variability persists at least down to the innermost stable circular orbit, if not the event horizon. These results can be compared quantitatively with similar analyses at different wavebands to test for connections between the variability mechanisms, and with light curves from theoretical models of accreting black holes.

Dexter, Jason; Kelly, Brandon; Bower, Geoffrey C.; Marrone, Daniel P.; Stone, Jordan; Plambeck, Richard

2014-08-01

421

Timescales of bubble coalescence, outgassing, and foam collapse in decompressed rhyolitic melts  

NASA Astrophysics Data System (ADS)

The timescale of degassing and outgassing in hydrous rhyolitic melts is investigated in a wide range of conditions by means of decompression experiments. The evolution of vesicularity, bubble diameter, and number density is characterized as a function of time either of decompression or spent at final pressure, in order to determine the effect of final pressure, temperature, syn- versus post-decompression degassing, melt composition, and microlites, on the timescale of bubble growth, coalescence, and outgassing. The result suggests that different bubble evolution and degassing-outgassing timescale corresponding to explosive and effusive eruption regimes can be cast in bulk viscosity (melt + bubbles; ?bulk) versus decompression time (rather than path) space. The ?bulk-time relationship defines three domains of (i) bubble nucleation and growth, restricted to short durations and high ?bulk (< ? 0.03 h for ?bulk ?105-6 Pas), (ii) equilibrium degassing with coalescence increasing from negligible (permeability >10-13m2) to extensive (permeability ?10 - 11- 12m2), and (iii) outgassing, restricted to long durations and low ?bulk (> ? 10 h for ?bulk <106 Pas; permeability >10-10m2) that eventually leads to foam collapse. These findings are applied to the case studies of Mt Pelée and Mt Pinatubo to infer the transition from pumice to dense pyroclasts in volcanic eruptions and the possibility of evolving from an explosive Plinian eruption to an effusive dome-growth event by giving the vesicular magma enough time to outgas and collapse (i.e. hundreds to tens of hours for ?bulk ?105 to 104 Pas, respectively). We also show the drastic effect of microlites on re-arranging preexistent bubbles and potentially triggering a late nucleation event.

Martel, Caroline; Iacono-Marziano, Giada

2015-02-01

422

On the time-scales of magmatism at island-arc volcanoes.  

PubMed

Precise information on time-scales and rates of change is fundamental to an understanding of natural processes and the development of quantitative physical models in the Earth sciences. U-series isotope studies are revolutionizing this field by providing time information in the range 10(2)-10(4) years, which is similar to that of many modern Earth processes. I review how the application of U-series isotopes has been used to constrain the time-scales of magma formation, ascent and storage beneath island-arc volcanoes. Different elements are distilled-off the subducting plate at different times and in different places. Contributions from subducted sediments to island-arc lava sources appear to occur some 350 kyr to 4 Myr prior to eruption. Fluid release from the subducting oceanic crust into the mantle wedge may be a multi-stage process and occurs over a period ranging from a few hundred kyr to less than one kyr prior to eruption. This implies that dehydration commences prior to the initiation of partial melting within the mantle wedge, which is consistent with recent evidence that the onset of melting is controlled by an isotherm and thus the thermal structure within the wedge. U-Pa disequilibria appear to require a component of decompression melting, possibly due to the development of gravitational instabilities. The preservation of large (226)Ra disequilibria permits only a short period of time between fluid addition and eruption. This requires rapid melt segregation, magma ascent by channelled flow and minimal residence time within the lithosphere. The evolution from basalt to basaltic andesite probably occurs rapidly during ascent or in magma reservoirs inferred from some geophysical data to lie within the lithospheric mantle. The flux across the Moho is broadly andesitic, and some magmas subsequently stall in more shallow crustal-level magma chambers, where they evolve to more differentiated compositions on time-scales of a few thousand years or less. PMID:12626270

Turner, S P

2002-12-15

423

What controls the variability of the South American summer monsoon on paleoclimate timescales? (Invited)  

NASA Astrophysics Data System (ADS)

In most of tropical South America south of the equator, including much of the Amazon basin, the Altiplano and central Andes, the Chaco, and the Pantanal, the majority of precipitation arrives as a result of the South American summer monsoon (SASM) system. Along the northeastern coast of Brazil, the majority of precipitation results from convection in the ITCZ, and the peak of this activity is delayed by about one season from that of the SASM. During the past century or so, which encompasses the entire instrumental period, a significant fraction (but not the majority) of the inter-annual precipitation variability in these regions was extrinsically forced, and ENSO, PDO, and tropical Atlantic variability have been implicated as major forcing factors. On lower frequency timescales, using paleoclimatic proxies, one can identify far larger changes in precipitation amount than those observed in the instrumental period. The spatial patterns of this precipitation variability and the dependence of these patterns on temporal scale (orbital or millennial) are becoming known. We posit that three major extrinsic climate-forcing factors can explain most of the observed (or not yet observed) precipitation variability on paleoclimate timescales: top-of-the atmosphere southern subtropical summer insolation, north-south Atlantic sea-surface temperature (SST) gradients, and east-west equatorial Pacific SST gradients. Using the best available paleo-SST data sets, the calculated values of insolation, and a subjective spatial weighting, we construct a simple spatio-temporal forcing model that we believe represents the history of precipitation over the region on millennial timescales for the past ca. 4,000,000 years. Our model effectively explains precipitation in the heart of the SASM region as inferred from speleothem records that span the last ~100,000 years BP and eventually will be tested using much older speleothem records dated by U-Pb chronologies.

Baker, P. A.; Fritz, S. C.; Rigsby, C. A.

2010-12-01

424

Decadal-timescale estuarine geomorphic change under future scenarios of climate and sediment supply  

USGS Publications Warehouse

Future estuarine geomorphic change, in response to climate change, sea-level rise, and watershed sediment supply, may govern ecological function, navigation, and water quality. We estimated geomorphic changes in Suisun Bay, CA, under four scenarios using a tidal-timescale hydrodynamic/sediment transport model. Computational expense and data needs were reduced using the morphological hydrograph concept and the morphological acceleration factor. The four scenarios included (1) present-day conditions; (2) sea-level rise and freshwater flow changes of 2030; (3) sea-level rise and decreased watershed sediment supply of 2030; and (4) sea-level rise, freshwater flow changes, and decreased watershed sediment supply of 2030. Sea-level rise increased water levels thereby reducing wave-induced bottom shear stress and sediment redistribution during the wind-wave season. Decreased watershed sediment supply reduced net deposition within the estuary, while minor changes in freshwater flow timing and magnitude induced the smallest overall effect. In all future scenarios, net deposition in the entire estuary and in the shallowest areas did not keep pace with sea-level rise, suggesting that intertidal and wetland areas may struggle to maintain elevation. Tidal-timescale simulations using future conditions were also used to infer changes in optical depth: though sea-level rise acts to decrease mean light irradiance, decreased suspended-sediment concentrations increase irradiance, yielding small changes in optical depth. The modeling results also assisted with the development of a dimensionless estuarine geomorphic number representing the ratio of potential sediment import forces to sediment export forces; we found the number to be linearly related to relative geomorphic change in Suisun Bay. The methods implemented here are widely applicable to evaluating future scenarios of estuarine change over decadal timescales. ?? The Author(s) 2009.

Ganju, N.K.; Schoellhamer, D.H.

2010-01-01

425

Timescales for Reequilibration of Major Elements in Olivine-Hosted Melt Inclusions  

NASA Astrophysics Data System (ADS)

Geochemical evidence demonstrates that near-fractional partial melts form over a range of upper mantle conditions from peridotites with variable bulk compositions. The importance of determining the initial compositions of melt inclusions lies in the ability of the major elements to record information about the conditions at which melt generation takes place, and the involvement of exotic lithologies in the melt generation process. However, before the major-element compositions of melt inclusions can be interpreted reliably, the effects of post-entrapment processes must be quantitatively understood. Diffusive reequilibration of olivine-hosted melt inclusions during cooling, magma mixing, or decompression can produce irreversible compositional changes in response to changes to the melt outside of the host olivine. Factors that influence the timescales for reequilibration of major elements in olivine-hosted melt inclusions are the sizes of the inclusion and the host olivine, which control the diffusion lengthscale, and the olivine-melt partition coefficient and diffusivity, which control the flux through the olivine grain. Among the major elements, Fe, Mg and Ca have the greatest potentials for undergoing diffusive reequilibration. The concentration of H2O in olivine-hosted melt inclusions must also be evaluated with care. Based on experimentally determined diffusivities and partition coefficients, reequilibration of Fe and Mg occurs on a timescale of years, while Ca reequilibrates over a few decades. Diffusion of H in olivine is rapid enough to allow reequilibration in a matter of hours. Important questions the must be answered in order to fully assess the reliability of the melt inclusion compositions are whether the history of Fe/Mg transport through the olivine can be uniquely determined, whether there are factors that rate limit transport of H, and whether gradients in slower diffusing elements can be used to constrain re-equilibration timescales.

Gaetani, G. A.; Hauri, E. H.

2008-12-01

426

Twisted phonons in Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

We consider elementary excitations in a Bose-Einstein condensate, carrying a finite amount of angular momentum. We show that these elementary excitations are modified Bogoliubov oscillations or phonons with a helical wave structure. These twisted phonon modes can contribute to the total vorticity in a quantum fluid, thus complementing the contribution of the traditional quantum vortices. Linear and nonlinear versions of twisted phonon modes will be discussed. New envelope soliton solutions are shown to exist in a condensate.

Mendonça, J. T.; Gammal, A.

2014-03-01

427

The einstein observatory medium sensitivity survey  

Microsoft Academic Search

Results are presented from an X-ray survey of ~50 square degrees of the high galactic latitude sky at sensitivities in the range 7·10-14 – 5·10-12 erg\\/cm2 sec (0·3–3·5 keV) carried out with the Imaging Proportional Counter (IPC) aboard the Einstein Observatory. The extragalactic sample consists of 48 sources which have been used to determine the number flux relation. The content

T. Maccacaro; E. D. Feigelson; R. Giacconi; I. M. Gioia; R. E. Griffiths; J. Liebert; S. S. Murray; J. Stocke; G. Zamorani

1981-01-01

428

Einstein manifolds in Ashtekar variables: explicit examples  

E-print Network

We show that all solutions to the vacuum Einstein field equations may be mapped to instanton configurations of the Ashtekar variables. These solutions are characterized by properties of the moduli space of the instantons. We exhibit explicit forms of these configurations for several well-known solutions, and indicate a systematic way to get new ones. Some interesting examples of these new solutions are described.

Lay Nam Chang; Chopin Soo

1992-07-30

429

Cosmic Axion Bose-Einstein Condensation  

E-print Network

QCD axions are a well-motivated candidate for cold dark matter. Cold axions are produced in the early universe by vacuum realignment, axion string decay and axion domain wall decay. We show that cold axions thermalize via their gravitational self-interactions, and form a Bose-Einstein condensate. As a result, axion dark matter behaves differently from the other proposed forms of dark matter. The differences are observable.

Banik, Nilanjan

2015-01-01

430

Gravity Probe B: Testing Einstein's Universe  

NSDL National Science Digital Library

Gravity Probe B is the relativity gyroscope experiment being developed by NASA and Stanford University to test two extraordinary, unverified predictions of Albert Einstein's general theory of relativity. The experiment will use changes in the direction of spin of four gyroscopes contained in an Earth satellite to measure how space and time are warped by the presence of the Earth, and, more profoundly, how the Earth's rotation drags spacetime around with it.

Everitt, C. W.

2003-10-10

431

General Relativity; An Einstein Centenary Survey  

NSDL National Science Digital Library

Written in honor of Albert Einstein's 100th birthday, this text was created by 21 experts in the theory of relativity to present the current state of research in the subject. Written at a very high level, especially in the mathematics, the survey tracks the history, development, and consequences of the theory of general relativity. This book is out of print, but is available from used-book sellers.

2009-02-19

432

ON THE NATURE OF THE PROTOTYPE LUMINOUS BLUE VARIABLE AG CARINAE. II. WITNESSING A MASSIVE STAR EVOLVING CLOSE TO THE EDDINGTON AND BISTABILITY LIMITS  

SciTech Connect

We show that the significantly different effective temperatures (T{sub eff}) achieved by the luminous blue variable AG Carinae during the consecutive visual minima of 1985-1990 (T{sub eff} {approx_equal} 22,800 K) and 2000-2001 (T{sub eff} {approx_equal} 17,000 K) place the star on different sides of the bistability limit, which occurs in line-driven stellar winds around T{sub eff} {approx} 21,000 K. Decisive evidence is provided by huge changes in the optical depth of the Lyman continuum in the inner wind as T{sub eff} changes during the S Dor cycle. These changes cause different Fe ionization structures in the inner wind. The bistability mechanism is also related to the different wind parameters during visual minima: the wind terminal velocity was 2-3 times higher and the mass-loss rate roughly two times smaller in 1985-1990 than in 2000-2003. We obtain a projected rotational velocity of 220 {+-} 50 km s{sup -1} during 1985-1990 which, combined with the high luminosity (L{sub *} = 1.5 x 10{sup 6} L{sub sun}), puts AG Car extremely close to the Eddington limit modified by rotation ({Omega}{Gamma} limit): for an inclination angle of 90{sup 0}, {Gamma}{sub {Omega}} {approx}> 1.0 for M{sub sun} {approx}< 60. Based on evolutionary models and mass budget, we obtain an initial mass of {approx}100 M{sub sun} and a current mass of {approx}60-70 M{sub sun} for AG Car. Therefore, AG Car is close to, if not at, the {Omega}{Gamma} limit during visual minimum. Assuming M = 70 M{sub sun}, we find that {Gamma}{sub {Omega}} decreases from 0.93 to 0.72 as AG Car expands toward visual maximum, suggesting that the star is not above the Eddington limit during maximum phases.

Groh, J. H. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Hillier, D. J. [Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260 (United States); Damineli, A., E-mail: jgroh@mpifr.de [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, 05508-900, Sao Paulo, SP (Brazil)

2011-07-20

433

Interferometric Testbed for Nanometer Level Stabilization of Environmental Motion Over Long Timescales  

NASA Technical Reports Server (NTRS)

We developed an interferometric testbed to stabilize environmental motions over timescales of several hours and a lengthscale of 1m. Typically, thermal and seismic motions on the ground are larger than 1 micron over these scales, affecting the precision of more sensitive measurements. To suppress such motions, we built an active stabilization system composed of interferometric sensors, a hexapod actuator, and a frequency stabilized laser. With this stabilized testbed, environmental motions were suppressed down to nm level. This system will allow us to perform sensitive measurements, such as ground testing of LISA (Laser Interferometer Space Antenna), in the presence of environmental noise.

Numata, Kenji; Camp, Jordan

2008-01-01

434

Microphysical Timescales in Clouds and their Application in Cloud-Resolving Modeling  

NASA Technical Reports Server (NTRS)

Independent prognostic variables in cloud-resolving modeling are chosen on the basis of the analysis of microphysical timescales in clouds versus a time step for numerical integration. Two of them are the moist entropy and the total mixing ratio of airborne water with no contributions from precipitating particles. As a result, temperature can be diagnosed easily from those prognostic variables, and cloud microphysics be separated (or modularized) from moist thermodynamics. Numerical comparison experiments show that those prognostic variables can work well while a large time step (e.g., 10 s) is used for numerical integration.

Zeng, Xiping; Tao, Wei-Kuo; Simpson, Joanne

2007-01-01

435

Observation of Optical Pulse and Material Dynamics on the Femtosecond Time-Scale  

SciTech Connect

The widespread availability of lasers that generate pulses on the femtosecond scale has opened new realms of investigation in the basic and applied sciences, rendering available excitations delivering intensities well in excess of 10{sup 21} W/cm{sup 2}, and furnishing probes capable of resolving molecular relaxation timescales. As a consequence and a necessity, sophisticated techniques to examine the pulse behavior on the femtosecond scale have been developed and are of crucial importance to gain insight on the behavior of physical systems. These techniques will be discussed with specific application to guided pulse propagation and ionization dynamics of noble gases.

Omenetto, F.; Luce, B.; Siders, C.W.; Taylor, A.J.

1999-09-13

436

Einstein Gravity as an emergent phenomenon?  

E-print Network

In this essay we marshal evidence suggesting that Einstein gravity may be an emergent phenomenon, one that is not ``fundamental'' but rather is an almost automatic low-energy long-distance consequence of a wide class of theories. Specifically, the emergence of a curved spacetime ``effective Lorentzian geometry'' is a common generic result of linearizing a classical scalar field theory around some non-trivial background. This explains why so many different ``analog models'' of general relativity have recently been developed based on condensed matter physics; there is something more fundamental going on. Upon quantizing the linearized fluctuations around this background geometry, the one-loop effective action is guaranteed to contain a term proportional to the Einstein--Hilbert action of general relativity, suggesting that while classical physics is responsible for generating an ``effective geometry'', quantum physics can be argued to induce an ``effective dynamics''. This physical picture suggests that Einstein gravity is an emergent low-energy long-distance phenomenon that is insensitive to the details of the high-energy short-distance physics.

Carlos Barcelo; Matt Visser; Stefano Liberati

2001-06-01

437

Thermodynamic structure of the Einstein tensor  

SciTech Connect

We analyze the generic structure of Einstein tensor projected onto a 2D spacelike surface S defined by a unit timelike and spacelike vectors u and n, respectively, which describe an accelerated observer (see text). Assuming that flow along u defines an approximate Killing vector {xi}, we then show that near the corresponding Rindler horizon, the flux j{sup a}=G{sub b}{sup a{xi}b} along the ingoing null geodesics k, i.e., j{center_dot}k, has a natural thermodynamic interpretation. Moreover, change in the cross-sectional area of the k congruence yields the required change in area of S under virtual displacements normal to it. The main aim of this paper is to clearly demonstrate how, and why, the content of Einstein equations under such horizon deformations, originally pointed out by Padmanabhan, is essentially different from the result of Jacobson, who employed the so-called Clausius relation in an attempt to derive Einstein equations from such a Clausius relation. More specifically, we show how a very specific geometric term (reminiscent of Hawking's quasilocal expression for energy of spheres) corresponding to change in gravitational energy arises inevitably in the first law: dE{sub G}/d{lambda}{proportional_to}Hd{sup 2}x{radical}({sigma}){sup (2)}R (see text)--the contribution of this purely geometric term would be missed in attempts to obtain area (and hence entropy) change by integrating the Raychaudhuri equation.

Kothawala, Dawood [Department of Mathematics and Statistics, University of New Brunswick, Fredericton, NB, E3B 5A3 (Canada)

2011-01-15

438

Einstein's Revolutionary Light--Quantum Hypothesis  

NASA Astrophysics Data System (ADS)

Albert Einstein's light-quantum paper was the only one of his great papers of 1905 that he himself called ``very revolutionary''. I sketch his arguments for light quanta, his analysis of the photoelectric effect, and his introduction of the wave-particle duality into physics in 1909. I show that Robert Andrews Millikan, in common with almost all physicists at the time, rejected Einstein's light-quantum hypothesis as an interpretation of his photoelectric-effect experiments of 1915. I then trace the complex experimental and theoretical route that Arthur Holly Compton followed between 1916 and 1922 that led to his discovery of the Compton effect, a discovery that Peter Debye also made virtually simultaneously and independently. Compton's discovery, however, was challenged on experimental grounds by William Duane and on theoretical grounds by Niels Bohr in the Bohr--Kramers--Slater theory of 1924, and only after that theory was disproved experimentally the following year by Walther Bothe and Hans Geiger in Berlin and by Compton and Alfred W. Simon in Chicago was Einstein's light-quantum hypothesis generally accepted by physicists.

Stuewer, R. H.

2006-03-01

439

Timescales Of The Influence Of IMF Clock Angle In Controlling The Characteristics Of Magnetospheric Dynamics  

NASA Astrophysics Data System (ADS)

We exploit a database of high-latitude ionospheric electric potential patterns, derived from radar observations of plasma convection in the northern hemisphere from the years 2000 - 2006, to investigate the timescales of interplanetary magnetic field (IMF) penetration into the magnetosphere. We parameterise the convection observations by IMF clock angle, ? (the angle between geocentric solar magnetic (GSM) north and the projection of the IMF vector onto the GSM Y-Z plane), and by an IMF timescale, ?B (the length of time that a similar clock angle has been maintained prior to the convection observations being made). We find that the nature of the ionospheric convection changes with IMF clock angle, as expected from previous time-averaged studies, and that for ?B ~ 30 mins the convection patterns closely resemble their time-averaged counterparts. However, we also find that for certain IMF clock angles, in particular those with a northward BZ component and significant BY (dusk-dawn) component, the patterns evolve with increasing ?B to less resemble their time-averaged counterparts, showing a marked enhancement in dusk-dawn asymmetry as ?B approaches 10 hours. We discuss these findings in terms of the effects of the persistent penetration of a quasi-steady IMF into the magnetosphere, and its implications for understanding different modes of magnetospheric dynamics.

Grocott, A.; Milan, S. E.

2013-12-01

440

Rapid Dust Formation in Novae: The Speed Class—Formation Timescale Correlation Explained  

NASA Astrophysics Data System (ADS)

Observations show that the time of onset of dust formation in classical novae depends strongly on their speed class, with dust typically taking longer to form in slower novae. Using empirical relationships between speed class, luminosity and ejection velocity, it can be shown that dust formation timescale is expected to be essentially independent of speed class. However, following a nova outburst the spectrum of the central hot source evolves, with an increasing proportion of the radiation being emitted short-ward of the Lyman limit. The rate at which the spectrum evolves also depends on the speed class. We have therefore refined the simple model by assuming photons at energies higher than the Lyman limit are absorbed by neutral hydrogen gas internal to the dust formation sites, therefore preventing these photons reaching the nucleation sites. With this refinement the dust formation timescale is theoretically dependent on speed class and the results of our theoretical modification agree well with the observational data. We consider two types of carbon-based dust, graphite and amorphous carbon, with both types producing similar relationships. Our results can be used to predict when dust will form in a nova of a given speed class and hence when observations should optimally be taken to detect the onset of dust formation.

Williams, S. C.; Bode, M. F.; Darnley, M. J.; Evans, A.; Zubko, V.; Shafter, A. W.

2013-11-01

441

Short timescale variation in the ENA flux emanating from the heliospheric poles: IBEX observations  

NASA Astrophysics Data System (ADS)

The Interstellar Boundary Explorer (IBEX) completes a full sweep of the sky once every six months; thus in general, if we seek evidence for temporal variation in the heliospheric ENA flux, we must wait six months before revisiting the same part of the sky [see McComas, et al., “Time variations of the ENA flux observed by IBEX: Is the outer heliosphere evolving?”, this session]. However, due to the constant sun-pointing orientation of the IBEX spin axis, two points on the sky, the ecliptic poles, are observed continuously. Thus we can examine if the heliosphere is changing on timescales shorter than six months at the poles, by tracking the evolution of ENA flux emanating from these regions. Our preliminary findings suggest that on timescales of ~50 days, temporal variations at the poles may be present; however, the statistical certainty is small. Due to time dispersion within the IBEX energy passbands, this is at the limit of achievable time resolution. The presence of time variability at the poles would be surprising, since solar variability is presumably the main driver of fluctuations at the interstellar boundary, and solar activity has been nearly absent over the current extended solar minimum.

Reisenfeld, D. B.; Abell, T. R.; Allegrini, F.; Crew, G. B.; Demajestre, B.; Frisch, P. C.; Funsten, H. O.; Fuselier, S. A.; Janzen, P.; Kucharek, H.; McComas, D. J.; Roelof, E. C.; Schwadron, N. A.

2009-12-01

442

Bridging physiological and evolutionary time-scales in a gene regulatory network.  

PubMed

Gene regulatory networks (GRNs) govern phenotypic adaptations and reflect the trade-offs between physiological responses and evolutionary adaptation that act at different time-scales. To identify patterns of molecular function and genetic diversity in GRNs, we studied the drought response of the common sunflower, Helianthus annuus, and how the underlying GRN is related to its evolution. We examined the responses of 32,423 expressed sequences to drought and to abscisic acid (ABA) and selected 145 co-expressed transcripts. We characterized their regulatory relationships in nine kinetic studies based on different hormones. From this, we inferred a GRN by meta-analyses of a Gaussian graphical model and a random forest algorithm and studied the genetic differentiation among populations (FST ) at nodes. We identified two main hubs in the network that transport nitrate in guard cells. This suggests that nitrate transport is a critical aspect of the sunflower physiological response to drought. We observed that differentiation of the network genes in elite sunflower cultivars is correlated with their position and connectivity. This systems biology approach combined molecular data at different time-scales and identified important physiological processes. At the evolutionary level, we propose that network topology could influence responses to human selection and possibly adaptation to dry environments. PMID:24786523

Marchand, Gwenaëlle; Huynh-Thu, Vân Anh; Kane, Nolan C; Arribat, Sandrine; Varès, Didier; Rengel, David; Balzergue, Sandrine; Rieseberg, Loren H; Vincourt, Patrick; Geurts, Pierre; Vignes, Matthieu; Langlade, Nicolas B

2014-07-01

443

BROAD ABSORPTION LINE DISAPPEARANCE ON MULTI-YEAR TIMESCALES IN A LARGE QUASAR SAMPLE  

SciTech Connect

We present 21 examples of C IV broad absorption line (BAL) trough disappearance in 19 quasars selected from systematic multi-epoch observations of 582 bright BAL quasars (1.9 < z < 4.5) by the Sloan Digital Sky Survey-I/II (SDSS-I/II) and SDSS-III. The observations span 1.1-3.9 yr rest-frame timescales, longer than have been sampled in many previous BAL variability studies. On these timescales, Almost-Equal-To 2.3% of C IV BAL troughs disappear and Almost-Equal-To 3.3% of BAL quasars show a disappearing trough. These observed frequencies suggest that many C IV BAL absorbers spend on average at most a century along our line of sight to their quasar. Ten of the 19 BAL quasars showing C IV BAL disappearance have apparently transformed from BAL to non-BAL quasars; these are the first reported examples of such transformations. The BAL troughs that disappear tend to be those with small-to-moderate equivalent widths, relatively shallow depths, and high outflow velocities. Other non-disappearing C IV BALs in those nine objects having multiple troughs tend to weaken when one of them disappears, indicating a connection between the disappearing and non-disappearing troughs, even for velocity separations as large as 10,000-15,000 km s{sup -1}. We discuss possible origins of this connection including disk-wind rotation and changes in shielding gas.

Filiz Ak, N.; Brandt, W. N.; Schneider, D. P. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Hall, P. B. [Department of Physics and Astronomy, York University, 4700 Keele St., Toronto, Ontario M3J 1P3 (Canada); Anderson, S. F.; Gibson, R. R. [Astronomy Department, University of Washington, Seattle, WA 98195 (United States); Lundgren, B. F. [Department of Physics, Yale University, New Haven, CT 06511 (United States); Myers, A. D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Petitjean, P. [Institut d'Astrophysique de Paris, Universite Paris 6, F-75014, Paris (France); Ross, Nicholas P. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420 (United States); Shen Yue [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States); York, D. G. [Department of Astronomy and Astrophysics, and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States); Bizyaev, D.; Brinkmann, J.; Malanushenko, E.; Oravetz, D. J.; Pan, K.; Simmons, A. E. [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); Weaver, B. A., E-mail: nfilizak@astro.psu.edu [Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States)

2012-10-01

444

Hydrodynamic timescales in a hyper-tidal region of freshwater influence  

NASA Astrophysics Data System (ADS)

This study uses a three-dimensional hydrodynamic model to investigate transport timescales in Liverpool Bay, a shallow hyper-tidal Region of Freshwater Influence (ROFI) with a density-driven baroclinic residual circulation. Flushing time, residence time and age are evaluated, providing rigorously defined parameters to describe the rate of offshore freshwater transport and basin replenishment. Additional challenges encountered when assessing these timescales in a tidally mixed regime are highlighted by idealised models. Climatological river gauge data reveals that the numerous local rivers contribute an average of 203 m3 s-1 of freshwater to Liverpool Bay. Based upon the mean salinity distribution, this would suggest a flushing time of approximately 136 days. The mean residence time of the region is approximately 103 days although small concentrations of water are retained over several years due to vigorous tidal mixing. Age in the region is highly variable with regular oscillations caused by tidal advection, whilst long term fluctuations are governed by river flow rates. The mean age gradient is directed offshore, approximately parallel to both the salinity gradient and the major axis of the tidal ellipse, with basin wide average magnitude of 6 days km-1. It is shown that salinity may be used to estimate the age of freshwater, which is not directly observable in practice.

Phelps, Jack J. C.; Polton, Jeff A.; Souza, Alejandro J.; Robinson, Leonie A.

2013-07-01

445

PROTOTYPING NON-EQUILIBRIUM VISCOUS-TIMESCALE ACCRETION THEORY USING LMC X-3  

SciTech Connect

Explaining variability observed in the accretion flows of black hole X-ray binary systems remains challenging, especially concerning timescales less than, or comparable to, the viscous timescale but much larger than the inner orbital period despite decades of research identifying numerous relevant physical mechanisms. We take a simplified but broad approach to study several mechanisms likely relevant to patterns of variability observed in the persistently high-soft Roche-lobe overflow system LMC X-3. Based on simple estimates and upper bounds, we find that physics beyond varying disk/corona bifurcation at the disk edge, Compton-heated winds, modulation of total supply rate via irradiation of the companion, and the likely extent of the partial hydrogen ionization instability is needed to explain the degree, and especially the pattern, of variability in LMC X-3 largely due to viscous dampening. We then show how evaporation-condensation may resolve or compound the problem given the uncertainties associated with this complex mechanism and our current implementation. We briefly mention our plans to resolve the question, refine and extend our model, and alternatives we have not yet explored.

Cambier, Hal J.; Smith, David M. [Physics Department, University of California, Santa Cruz, CA 95064 (United States)] [Physics Department, University of California, Santa Cruz, CA 95064 (United States)

2013-04-10

446

Mechanism of transient force augmentation varying with two distinct timescales for interacting vortex rings  

NASA Astrophysics Data System (ADS)

The dynamics of dual vortex ring flows is studied experimentally and numerically in a model system that consists of a piston-cylinder apparatus. The flows are generated by double identical strokes which have the velocity profile characterized by the sinusoidal function of half the period. By calculating the total wake impulse in two strokes in the experiments, it is found that the average propulsive force increases by 50% in the second stroke for the sufficiently small stroke length, compared with the first stroke. In the numerical simulations, two types of transient force augmentation are revealed, there being the transient force augmentation for the small stroke lengths and the absolute transient force augmentation for the large stroke lengths. The relative transient force augmentation increases to 78% for L/D = 1, while the absolute transient force augmentation for L/D = 4 is twice as much as that for L/D = 1. Further investigation demonstrates that the force augmentation is attributed to the interaction between vortex rings, which induces transport of vortex impulse and more evident fluid entrainment. The critical situation of vortex ring separation is defined and indicated, with vortex spacing falling in a narrow gap when the stroke lengths vary. A new model is proposed concerning the limiting process of impulse, further suggesting that apart from vortex formation timescale, vortex spacing should be interpreted as an independent timescale to reflect the dynamics of vortex interaction.

Fu, Zhidong; Qin, Suyang; Liu, Hong

2014-01-01

447

RAPID DUST FORMATION IN NOVAE: THE SPEED CLASS—FORMATION TIMESCALE CORRELATION EXPLAINED  

SciTech Connect

Observations show that the time of onset of dust formation in classical novae depends strongly on their speed class, with dust typically taking longer to form in slower novae. Using empirical relationships between speed class, luminosity and ejection velocity, it can be shown that dust formation timescale is expected to be essentially independent of speed class. However, following a nova outburst the spectrum of the central hot source evolves, with an increasing proportion of the radiation being emitted short-ward of the Lyman limit. The rate at which the spectrum evolves also depends on the speed class. We have therefore refined the simple model by assuming photons at energies higher than the Lyman limit are absorbed by neutral hydrogen gas internal to the dust formation sites, therefore preventing these photons reaching the nucleation sites. With this refinement the dust formation timescale is theoretically dependent on speed class and the results of our theoretical modification agree well with the observational data. We consider two types of carbon-based dust, graphite and amorphous carbon, with both types producing similar relationships. Our results can be used to predict when dust will form in a nova of a given speed class and hence when observations should optimally be taken to detect the onset of dust formation.

Williams, S. C.; Bode, M. F.; Darnley, M. J. [Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom)] [Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom); Evans, A. [Astrophysics Group, Lennard Jones Laboratory, Keele University, Keele, Staffordshire ST5 5BG (United Kingdom)] [Astrophysics Group, Lennard Jones Laboratory, Keele University, Keele, Staffordshire ST5 5BG (United Kingdom); Zubko, V. [Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)] [Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Shafter, A. W., E-mail: S.C.Williams@2010.ljmu.ac.uk [Department of Astronomy, San Diego State University, San Diego, CA 92182 (United States)

2013-11-10

448

Long-timescale dynamics and regulation of Sec-facilitated protein translocation  

PubMed Central

Summary We present a coarse-grained modeling approach that spans the nanosecond- to minute-timescale dynamics of co-translational protein translocation. The method enables direct simulation of both integral membrane protein topogenesis and transmembrane domain (TM) stop-transfer efficiency. Simulations reveal multiple kinetic pathways for protein integration, including a mechanism in which the nascent protein undergoes slow-timescale reorientation, or flipping, in the confined environment of the translocon channel. Competition among these pathways gives rise to the experimentally observed dependence of protein topology on ribosomal translation rate and protein length. We further demonstrate that sigmoidal dependence of stop-transfer efficiency on TM hydrophobicity arises from local equilibration of the TM across the translocon lateral gate, and it is predicted that slowing ribosomal translation yields decreased stop-transfer efficiency in long proteins. This work reveals the balance between equilibrium and non-equilibrium processes in protein targeting, and it provides new insight into the molecular regulation of the Sec translocon. PMID:23084746

Zhang, Bin; Miller, Thomas F.

2012-01-01

449

Einstein-Podolsky-Rosen Correlations via Dissociation of a Molecular Bose-Einstein Condensate  

SciTech Connect

Recent experimental measurements of atomic intensity correlations through atom shot noise suggest that atomic quadrature phase correlations may soon be measured with a similar precision. We propose a test of local realism with mesoscopic numbers of massive particles based on such measurements. Using dissociation of a Bose-Einstein condensate of diatomic molecules into bosonic atoms, we demonstrate that strongly entangled atomic beams may be produced which possess Einstein-Podolsky-Rosen (EPR) correlations in field quadratures in direct analogy to the position and momentum correlations originally considered by EPR.

Kheruntsyan, K.V.; Drummond, P.D. [ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Qld 4072 (Australia); Olsen, M.K. [ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Qld 4072 (Australia); Instituto de Fisica da Universidade Federal Fluminense, Boa Viagem 24210-340, Niteroi - Rio de Janeiro (Brazil)

2005-10-07

450

Ultraluminous X-ray Sources Powered by Radiatively Efficient Two-Phased Super-Eddington Accretion onto Stellar Mass Black holes  

E-print Network

The radiation spectra of many of the brightest ultraluminous X-ray sources (ULXs) are dominated by a hard power law component, likely powered by a hot, optically thin corona that Comptonizes soft seed photons emitted from a cool, optically thick black hole accretion disk. Before its dissipation and subsequent conversion into coronal photon power, the randomized gravitational binding energy responsible for powering ULX phenomena must separate from the mass of its origin by a means other than, and quicker than, electron scattering-mediated radiative diffusion. Therefore, the release of accretion power in ULXs is not necessarily subject to Eddington-limited photon trapping, as long as it occurs in a corona. Motivated by these basic considerations, we present a model of ULXs powered by geometrically thin accretion onto stellar mass black holes. We argue that the radiative efficiency of the flow remains high if the corona is magnetized or optically thin and the majority of the accretion power escapes in the form of radiation rather than an outflow. Within the context of the current black hole X-ray binary paradigm, our ULX model may be viewed as an extension of the very high state observed in Galactic sources. (abridged)

Aristotle Socrates; Shane W. Davis

2005-11-18

451

A local existence theorem for the Einstein–Dirac equation  

Microsoft Academic Search

We studied the Einstein–Dirac equation as well as the weak Killing equation on Riemannian spin manifolds with codimension one foliation. We prove that, for any manifold Mn admitting real Killing spinors (resp. parallel spinors), there exist warped product metrics ?? on Mn×R such that (Mn×R,??) admit Einstein spinors (resp. weak Killing spinors). To prove the result we split the Einstein–Dirac

Eui Chul Kim

2002-01-01

452

Extended Horava gravity and Einstein-aether theory  

SciTech Connect

Einstein-aether theory is general relativity coupled to a dynamical, unit timelike vector. If this vector is restricted in the action to be hypersurface orthogonal, the theory is identical to the IR limit of the extension of Horava gravity proposed by Blas, Pujolas and Sibiryakov. Hypersurface orthogonal solutions of Einstein-aether theory are solutions to the IR limit of this theory, hence numerous results already obtained for Einstein-aether theory carry over.

Jacobson, Ted [Center for Fundamental Physics, University of Maryland, College Park, Maryland 20742-4111 (United States)

2010-05-15

453

Einstein centennial review article \\/ Article de synthèse commémoratif du centenaire de l'année miraculeuse d'Einstein A second century of Einstein? Bose-Einstein condensation and quantum information1  

Microsoft Academic Search

A century ago Albert Einstein transformed classical physics with his seminal papers on Brownian motion, the Photoelectric effect, and, of course, special and later general relativity. Lesser well-known are his contributions to Bose-Einstein Condensation and the Einstein-Podolsky-Rosen paradox, the latter being a criticism of Quantum Mechanics. These later works were regarded even by physicists for decades as mere Gedanken or

William Arie van Wijngaarden

454

Derivation of Einstein-Cartan theory from general relativity  

E-print Network

General relativity cannot describe exchange of intrinsic and orbital angular momentum. Einstein Cartan theory, which includes affine torsion, resolves this problem. All early approaches to Einstein Cartan theory treated inclusion of torsion as an independent assuption. In 1986 the author published a derivation of Einstein Cartan theory from general relativity with classical spin, with no additional assumptions or parameters. This paper adds simpler explanations, correction of a factor of 2, more computational details, a discussion of relevance to cosmic inflation, a summary of the evidence in support of Einstein Cartan theory, and a discussion of limitations of the derivation.

R. J. Petti

2014-12-03

455

Forming stars on a viscous time-scale: the key to exponential stellar profiles in disc galaxies?  

NASA Astrophysics Data System (ADS)

We argue for implementing star formation on a viscous time-scale in hydrodynamical simulations of disc galaxy formation and evolution. Modelling two-dimensional isolated disc galaxies with the Bhatnagar-Gross-Krook (BGK) hydrocode, we verify the analytic claim of various authors that if the characteristic time-scale for star formation is equal to the viscous time-scale in discs, the resulting stellar profile is exponential on several scalelengths whatever the initial gas and dark matter profile. This casts new light on both numerical and semi-analytical disc formation simulations that either (a) commence star formation in an already exponential gaseous disc, (b) begin a disc simulation with conditions known to lead to an exponential, i.e. the collapse of a spherically symmetric nearly uniform sphere of gas in solid-body rotation under the assumption of specific angular momentum conservation, or (c) in simulations performed in a hierarchical context, tune their feedback processes to delay disc formation until the dark matter haloes are slowly evolving and without much substructure so that the gas has the chance to collapse under conditions known to give exponentials. In such models, star formation follows a Schmidt-like law, which for lack of a suitable time-scale, resorts to an efficiency parameter. With star formation prescribed on a viscous time-scale, however, we find gas and star fractions after ~12Gyr that are consistent with observations without having to invoke a `fudge factor' for star formation. Our results strongly suggest that despite our gap in understanding the exact link between star formation and viscosity, the viscous time-scale is indeed the natural time-scale for star formation.

Slyz, Adrianne D.; Devriendt, Julien E. G.; Silk, Joseph; Burkert, Andreas

2002-07-01

456

Revisiting the Einstein-Bohr Dialogue Einstein and Bohr No names loom larger in the history of twentieth-century physics, and  

E-print Network

in the history of twentieth-century physics, and rightly so, Albert Einstein and Niels Bohr being the figuresRevisiting the Einstein-Bohr Dialogue Don Howard Einstein and Bohr ­ No names loom larger identified complementarity as the chief novelty in the quantum description of nature, Einstein for having

Howard, Don

457

GRAVITATION & DARK ENERGY Part One (of 3) : Einstein's Theory of General Relativity  

E-print Network

of the human race. Let's see how easy it was for Albert Einstein to discoverGRAVITATION & DARK ENERGY 1 Part One (of 3) : Einstein's Theory General Relativity. Einstein's truly brilliant idea was that the presence

458

Albert Einstein - Chief Engineer of the Universe: 100 Authors for Einstein Essays  

Microsoft Academic Search

In 1905, Albert Einstein published five scientific articles that fundamentally changed the world-view of physics: The Special Theory of Reativity revolutionized our concept of space and time, E=mc² became the best-known equation in physics. On the occasion of the 100th aniversary of his \\

Jürgen Renn

2005-01-01

459

Transfer of Satellite Rainfall Uncertainty from Gauged to Ungauged Regions at Regional and Seasonal Timescales  

NASA Technical Reports Server (NTRS)

Hydrologists and other users need to know the uncertainty of the satellite rainfall data sets across the range of time/space scales over the whole domain of the data set. Here, uncertainty' refers to the general concept of the deviation' of an estimate from the reference (or ground truth) where the deviation may be defined in multiple ways. This uncertainty information can provide insight to the user on the realistic limits of utility, such as hydrologic predictability, that can be achieved with these satellite rainfall data sets. However, satellite rainfall uncertainty estimation requires ground validation (GV) precipitation data. On the other hand, satellite data will be most useful over regions that lack GV data, for example developing countries. This paper addresses the open issues for developing an appropriate uncertainty transfer scheme that can routinely estimate various uncertainty metrics across the globe by leveraging a combination of spatially-dense GV data and temporally sparse surrogate (or proxy) GV data, such as the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar and the Global Precipitation Measurement (GPM) mission Dual-Frequency Precipitation Radar. The TRMM Multi-satellite Precipitation Analysis (TMPA) products over the US spanning a record of 6 years are used as a representative example of satellite rainfall. It is shown that there exists a quantifiable spatial structure in the uncertainty of satellite data for spatial interpolation. Probabilistic analysis of sampling offered by the existing constellation of passive microwave sensors indicate that transfer of uncertainty for hydrologic applications may be effective at daily time scales or higher during the GPM era. Finally, a commonly used spatial interpolation technique (kriging), that leverages the spatial correlation of estimation uncertainty, is assessed at climatologic, seasonal, monthly and weekly timescales. It is found that the effectiveness of kriging is sensitive to the type of uncertainty metric, time scale of transfer and the density of GV data within the transfer domain. Transfer accuracy is lowest at weekly timescales with the error doubling from monthly to weekly.However, at very low GV data density (<20% of the domain), the transfer accuracy is too low to show any distinction as a function of the timescale of transfer.

Tang, Ling; Hossain, Faisal; Huffman, George J.

2010-01-01

460

Bose-Einstein condensation on quantum graphs  

E-print Network

We present results on Bose-Einstein condensation (BEC) on general compact quantum graphs, i.e., one-dimensional systems with a (potentially) complex topology. We first investigate non-interacting many-particle systems and provide a complete classification of systems that exhibit condensation. We then consider models with interactions that consist of a singular part as well as a hardcore part. In this way we obtain generalisations of the Tonks-Girardeau gas to graphs. For this we find an absence of phase transitions which then indicates an absence of BEC.

Jens Bolte; Joachim Kerner

2014-03-02

461

Nonequilibrium version of the Einstein relation.  

PubMed

The celebrated Einstein relation between the diffusion coefficient D and the drift velocity v is violated in nonequilibrium circumstances. We analyze how this violation emerges for the simplest example of a Brownian motion on a lattice, taking into account the interplay between the periodicity, the randomness, and the asymmetry of the transition rates. Based on the nonequilibrium fluctuation theorem the v/D ratio is found to be a nonlinear function of the affinity. Hence it depends in a nontrivial way on the microscopics of the sample. PMID:25314417

Hurowitz, Daniel; Cohen, Doron

2014-09-01

462

Multimessenger astronomy with the Einstein Telescope  

E-print Network

Gravitational waves (GWs) are expected to play a crucial role in the development of multimessenger astrophysics. The combination of GW observations with other astrophysical triggers, such as from gamma-ray and X-ray satellites, optical/radio telescopes, and neutrino detectors allows us to decipher science that would otherwise be inaccessible. In this paper, we provide a broad review from the multimessenger perspective of the science reach offered by the third generation interferometric GW detectors and by the Einstein Telescope (ET) in particular. We focus on cosmic transients, and base our estimates on the results obtained by ET's predecessors GEO, LIGO, and Virgo.

Eric Chassande-Mottin; Martin Hendry; Patrick J. Sutton; Szabolcs Márka

2010-05-11

463

Einstein-Yang-Mills-Lorentz Black Holes  

E-print Network

Different black hole solutions of the coupled Einstein-Yang-Mills equations are well known from long time. They have attracted much attention from mathematicians and physicists from their discovery. In this work, we analyze black holes associated with the gauge Lorentz group. In particular, we study solutions which identify the gauge connection with the spin connection. This ansatz allows to find exact solutions to the complete system of equations. By using this procedure, we show the equivalence between the Yang-Mills-Lorentz model in curved space-time and a particular set of extended gravitational theories.

Cembranos, Jose A R

2015-01-01

464

Color superconductivity in the static Einstein Universe  

E-print Network

We study the behavior of quark and diquark condensates in dense quark matter under the influence of a gravitational field adopting as a simple model the static $D-$dimensional Einstein Universe. Calculations are performed in the framework of the extended Nambu--Jona-Lasinio model at finite temperature and quark density on the basis of the thermodynamic potential and the gap equations. Quark and diquark condensates as functions of the chemical potential and temperature at different values of the curvature have been studied. Phase portraits of the system have been constructed.

D. Ebert; A. V. Tyukov; V. Ch. Zhukovsky

2007-03-23

465

Extragalactic counterparts to Einstein slew survey sources  

NASA Technical Reports Server (NTRS)

The Einstein slew survey consists of 819 bright X-ray sources, of which 636 (or 78 percent) are identified with counterparts in standard catalogs. The importance of bright X-ray surveys is stressed, and the slew survey is compared to the Rosat all sky survey. Statistical techniques for minimizing confusion in arcminute error circles in digitized data are discussed. The 238 slew survey active galactic nuclei, clusters, and BL Lacertae objects identified to date and their implications for logN-logS and source evolution studies are described.

Schachter, Jonathan F.; Elvis, Martin; Plummer, David; Remillard, Ron

1992-01-01

466

Superfluidity of spinor Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

We consider a spin-1/2 Bose-Einstein condensate initially prepared in a single-spin projection. The two channels of dynamical excitations existing in such a system (density and spin waves) are discussed and we show how pure spin waves can be excited in the presence of local magnetic defects. We analyze the role played by spin excitations on the Landau superfluidity criterion and demonstrate the absence of absolute superfluidity for the antiferromagnetic condensate. In the ferromagnetic case, we identify two critical velocities for the breakdown of superfluidity.

Flayac, H.; Terças, H.; Solnyshkov, D. D.; Malpuech, G.

2013-11-01

467

Fall detection and classifications based on time-scale radar signal characteristics  

NASA Astrophysics Data System (ADS)

Unattended catastrophic falls result in risk to the lives of elderly. There are growing efforts and rising interest in detecting falls of the aging population, especially those living alone. Radar serves as an effective non-intrusive sensor for detecting human activities. For radar to be effective, it is important to achieve low false alarms, i.e., the system can reliably differentiate between a fall and other human activities. In this paper, we discuss the time-scale based signal analysis of the radar returns from a human target. Reliable features are extracted from the scalogram and are used for fall classifications. The classification results and the advantages of using a wavelet transform are discussed.

Gadde, Ajay; Amin, Moeness G.; Zhang, Yimin D.; Ahmad, Fauzia

2014-05-01

468

The neuronal response at extended timescales: long-term correlations without long-term memory  

PubMed Central

Long term temporal correlations frequently appear at many levels of neural activity. We show that when such correlations appear in isolated neurons, they indicate the existence of slow underlying processes and lead to explicit conditions on the dynamics of these processes. Moreover, although these slow processes can potentially store information for long times, we demonstrate that this does not imply that the neuron possesses a long memory of its input, even if these processes are bidirectionally coupled with neuronal response. We derive these results for a broad class of biophysical neuron models, and then fit a specific model to recent experiments. The model reproduces the experimental results, exhibiting long term (days-long) correlations due to the interaction between slow variables and internal fluctuations. However, its memory of the input decays on a timescale of minutes. We suggest experiments to test these predictions directly. PMID:24744724

Soudry, Daniel; Meir, Ron

2014-01-01

469

Transmembrane Exchange of Hyperpolarized 13C-Urea in Human Erythrocytes: Subminute Timescale Kinetic Analysis  

PubMed Central

The rate of exchange of urea across the membranes of human erythrocytes (red blood cells) was quantified on the 1-s to 2-min timescale. 13C-urea was hyperpolarized and subjected to rapid dissolution and the previously reported (partial) resolution of 13C NMR resonances from the molecules inside and outside red blood cells in suspensions was observed. This enabled a stopped-flow type of experiment to measure the (initially) zero-trans transport of urea with sequential single-pulse 13C NMR spectra, every second for up to ?2 min. Data were analyzed using Bayesian reasoning and a Markov chain Monte