Radcliffe Institute for Advanced Study

Cambridge, MA, United States

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Cambridge, MA, United States

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News Article | May 23, 2017
Site: www.enr.com

Rene Olivo was promoted to senior vice president of operations for Southern California at Rudolph and Sletten Inc. He will work out of the firm’s Irvine office, which he helped open in 1985. He most recently served as vice president of operations in the firm’s San Diego office. Rudolph & Sletten also hired Ray Polidoro as a vice president in Los Angeles and Jack McMackin as a business development executive in Irvine. Polidoro previously served as manager of design and construction for the Judicial Council of California’s capital program, while McMackin was national business development manager for Petra Integrated Construction Strategies. Jorge Colón was appointed as CO Architects’ first director of interior architecture and design. In addition to previously working for architecture firms in Los Angeles, Phoenix and Boston, Colón ran his own firm, LÓNdesign, and most recently served as project manager and owner’s representative. He holds a master’s degree in architecture from Arizona State University and a master’s in design studies from Harvard University Graduate School of Design. Tim Haile was hired to serve as deputy executive director, projects, for the Contra Costa Transportation Authority. He most recently worked at Michael Baker International as Inland Empire transportation manager. Haile is a past honoree of ENR California’s Top 20 Under 40 competition. Alahe Aldo has joined Carrier Johnson + CULTURE in San Diego as director of higher education. Aldo has worked extensively with campuses across the Northeastern U.S., including projects at Harvard University’s Radcliffe Institute for Advanced Study, MIT and Boston College. Nate Cormier has been added to Los Angeles-based Rios Clementi Hale Studios as principal and landscape architect. He previously worked for SvR in Seattle and AECOM in Los Angeles. In his new role, he will begin working on the Palm Springs City Park, which will provide festival space to downtown Palm Springs. He holds a master’s degree in landscape architecture from Harvard University’s Graduate School of Design. Cormier was elected to the Downtown Los Angeles Neighborhood Council, where he serves on its Planning and Land Use Committee. Balfour Beatty US has named John P. Carpenter chief legal officer for its California operations. Carpenter, based in San Diego, joins the firm after 23 years with Kiewit Corp., where he led the company’s legal and contract procurement and the delivery of a variety of large projects. He serves as an arbitrator for the American Arbitration Association on its national construction panel and is a member of the American Bar Association’s Construction Forum. EwingCole named Joseph Castner as the firm’s director of operations for its Irvine office. He most recently served as principal and managing director at Jacobs/KlingStubbins in Washington, D.C. He previously worked for SOM in Chicago, New York and London. CallisonRTKL’s global architecture practice named Kelly Farrell as executive vice president. She has been global practice group leader for workplace since 2016 and is based in Los Angeles.


Russell H.R.,University of Waterloo | Mcnamara B.R.,University of Waterloo | Mcnamara B.R.,Perimeter Institute for Theoretical Physics | Mcnamara B.R.,Harvard - Smithsonian Center for Astrophysics | And 12 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We present a new 400-ks Chandra X-ray observation of the merging galaxy cluster Abell 2146. This deep observation reveals detailed structure associated with the major merger event including the Mach number M= 2.3 ± 0.2 bow shock ahead of the dense, ram pressure stripped subcluster core and the first known example of an upstream shock in the intracluster medium (ICM) (M= 1.6 ± 0.1). By measuring the electron temperature profile behind each shock front, we determine the time-scale for the electron population to thermally equilibrate with the shock-heated ions. We find that the temperature profile behind the bow shock is consistent with the time-scale for Coulomb collisional equilibration and the post-shock temperature is lower than expected for instant shock heating of the electrons. Although like the Bullet cluster the electron temperatures behind the upstream shock front are hotter than expected, favouring the instant heating model, the uncertainty on the temperature values is greater here and there is significant substructure complicating the interpretation. We also measured the width of each shock front and the contact discontinuity on the leading edge of the subcluster core to investigate the suppression of transport processes in the ICM. The upstream shock is ∼440kpc in length but appears remarkably narrow over this distance with a best-fitting width of only 6 +5 -3 kpc compared with the mean free path of 23 ± 5kpc. The leading edge of the subcluster core is also narrow with an upper limit on the width of only 2kpc separating the cool, multiphase gas at 0.5-2keV from the shock-heated surrounding ICM at ∼6keV. The strong suppression of diffusion and conduction across this edge suggests a magnetic draping layer may have formed around the subcluster core. The deep Chandra observation has also revealed a cool, dense plume of material extending ∼170kpc perpendicular to the merger axis, which is likely to be the disrupted remnant of the primary cluster core. This asymmetry in the cluster morphology indicates the merger has a non-zero impact parameter. We suggest that this also explains why the south-western edge of the subcluster core is narrow and stable over ∼150kpc in length, but the north-eastern edge is broad and being stripped of material. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.


News Article | December 16, 2016
Site: www.eurekalert.org

MADISON, Wis. - Mother-of-pearl or nacre (pronounced nay-ker), the lustrous, tough-as-nails biomineral that lines some seashells, has been shown to be a faithful record of ancient ocean temperature. Writing online Thursday, Dec. 15, in the journal Earth and Planetary Science Letters, a team led by University of Wisconsin-Madison physics Professor Pupa Gilbert describes studies of the physical attributes of nacre in modern and fossil shells showing that the biomineral provides an accurate record of temperature as the material is formed, layer upon layer, in a mollusk. "We can very accurately correlate nacre tablet thickness with temperature," says Gilbert, explaining that mother-of-pearl is formed as mollusks lay down microscopic polygonal tablets of the mineral aragonite like brickwork to build layers of the shiny biomineral. The work is important because it provides scientists with a new and potentially more accurate method of measuring ancient ocean temperatures, improving on methods now used with other biominerals to tease out the record of the environmental conditions at which the materials formed in the distant past. "Everyone else measures temperatures in the ancient world using chemical proxies," says Gilbert, referencing methods that, for example, use ratios of isotopic oxygen locked into tiny fossil shells made by marine microorganisms known as Foraminifera to get a snapshot of ocean temperatures in the distant past. The method devised by Gilbert and her collaborators is extraordinarily simple: using just a scanning electron microscope and a cross section of shell, it is possible to measure the thickness of the layered microscopic tablets that compose nacre in a shell. The thickness of the tablets, explains Gilbert, correlates with ocean temperature as measured in modern shells when ocean temperatures were known at the time the shells were formed. The new work by the researchers from Wisconsin, Harvard, and the Lawrence Berkeley National Laboratory provides a novel physical approach to measuring past climate, says Gilbert, an expert in biomineral formation. "If what you are measuring is a physical structure, you see it directly," says Gilbert. "You just measure nacre tablet thickness, the spacing of the lines, and it corresponds to temperature. When the temperature is warmer, the layers get thicker." The new study looked at fossil samples of nacre as old as 200 million years from a mollusk in the family Pinnidae, large, fast-growing saltwater clams that live in shallow ocean environments. Today, as in the distant past, the bivalves are widespread in tropical and temperate coastal and shallow continental shelf environments. The new method is potentially more accurate, Gilbert notes, because the chemistry of fossil shells can be altered by diagenesis. Diagenesis occurs over geologic time, during or after sediments rain down on ocean beds to form sedimentary rock. Fossil shells may partially dissolve and re-precipitate as calcite, which fills cracks in aragonite nacre, thus skewing the chemical analysis of a sample, if analyzed as a bulk sample. "If the chemistry changes after the death of a fossil, the formation chemistry isn't necessarily preserved," says Gilbert. On the other hand, "if the physical structure is altered by diagenesis, you will notice immediately that nacre is no longer layered, and so you will know that it's not worth analyzing that area. If just a few nacre tablets are preserved, their thickness can easily be measured" meaning the new technique can augment current geochemical methods used to assess past temperatures, and thus help reconstruct ancient climates, especially the shallow marine environments that preserve most of the world's invertebrate fossil record. The family of mollusks in the new study has lived in the world's oceans for more than 400 million years, potentially leaving a clear record of ocean temperatures into the distant past. For purposes of assessing climate, the record is valuable because not only does it say something about past climate, but the data can also help modelers forecast future climate and environmental change. "The only thing you can do to understand climate in the future is to look at climate in the past," Gilbert notes. The new study was supported by a grant from the U.S. Department of Energy, the National Science Foundation, and the Radcliffe Institute for Advanced Study Fellowship Program.


Kharb P.,Rochester Institute of Technology | O'Dea C.P.,Rochester Institute of Technology | O'Dea C.P.,Harvard - Smithsonian Center for Astrophysics | Tilak A.,Smithsonian Astrophysical Observatory | And 6 more authors.
Astrophysical Journal | Year: 2012

We present here the results from new Very Long Baseline Array (VLBA) observations at 1.6 and 5GHz of 19galaxies of a complete sample of 21 Uppasala General Catalog (UGC) Fanaroff-Riley type I (FRI) radio galaxies. New Chandra data of two sources, viz., UGC00408 and UGC08433, are combined with the Chandra archival data of 13 sources. The 5GHz observations of 10 "core-jet" sources are polarization-sensitive, while the 1.6GHz observations constitute second-epoch total intensity observations of nine "core-only" sources. Polarized emission is detected in the jets of seven sources at 5GHz, but the cores are essentially unpolarized, except in M87. Polarization is detected at the jet edges in several sources, and the inferred magnetic field is primarily aligned with the jet direction. This could be indicative of magnetic field "shearing" due to jet-medium interaction, or the presence of helical magnetic fields. The jet peak intensity I ν falls with distance d from the core, following the relation, I νda , where a is typically - 1.5. Assuming that adiabatic expansion losses are primarily responsible for the jet intensity "dimming," two limiting cases are considered: (1) the jet has a constant speed on parsec scales and is expanding gradually such that the jet radius rd 0.4; this expansion is, however, unobservable in the laterally unresolved jets at 5GHz, and (2) the jet is cylindrical and is accelerating on parsec scales. Accelerating parsec-scale jets are consistent with the phenomenon of "magnetic driving" in Poynting-flux-dominated jets. While slow jet expansion as predicted by case (1) is indeed observed in a few sources from the literature that are resolved laterally, on scales of tens or hundreds of parsecs, case (2) cannot be ruled out in the present data, provided the jets become conical on scales larger than those probed by VLBA. Chandra observations of 15 UGC FRIs detect X-ray jets in 9 of them. The high frequency of occurrence of X-ray jets in this complete sample suggests that they are a signature of a ubiquitous process in FRI jets. It appears that the FRI jets start out relativistically on parsec scales but decelerate on kiloparsec scales, with the X-ray emission revealing the sites of bulk deceleration and particle reacceleration. © 2012. The American Astronomical Society. All rights reserved.


Comerford J.M.,University of California at Berkeley | Moustakas L.A.,Jet Propulsion Laboratory | Natarajan P.,Yale University | Natarajan P.,Radcliffe Institute for Advanced Study
Astrophysical Journal | Year: 2010

Scaling relations of observed galaxy cluster properties are useful tools for constraining cosmological parameters as well as cluster formation histories. One of the key cosmological parameters, σ8, is constrained using observed clusters of galaxies, although current estimates of σ8 from the scaling relations of dynamically relaxed galaxy clusters are limited by the large scatter in the observed cluster mass-temperature (M-T) relation. With a sample of eight strong lensing clusters at 0.3 < z < 0.8, we find that the observed cluster concentration-mass relation can be used to reduce the M-T scatter by a factor of 6. Typically only relaxed clusters are used to estimate σ8, but combining the cluster concentration-mass relation with the M-T relation enables the inclusion of unrelaxed clusters as well. Thus, the resultant gains in the accuracy of σ8 measurements from clusters are twofold: the errors on σ8 are reduced and the cluster sample size is increased. Therefore, the statistics on σ8 determination from clusters are greatly improved by the inclusion of unrelaxed clusters. Exploring cluster scaling relations further, we find that the correlation between brightest cluster galaxy (BCG) luminosity and cluster mass offers insight into the assembly histories of clusters. We find preliminary evidence for a steeper BCG luminosity-cluster mass relation for strong lensing clusters than the general cluster population, hinting that strong lensing clusters may have had more active merging histories. © 2010. The American Astronomical Society. All rights reserved.


Pyers J.E.,Wellesley College | Pyers J.E.,Radcliffe Institute for Advanced Study | Shusterman A.,Wesleyan University | Senghas A.,Barnard College | And 2 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2010

Although spatial language and spatial cognition covary over development and across languages, determining the causal direction of this relationship presents a challenge. Here we show that mature human spatial cognition depends on the acquisition of specific aspects of spatial language. We tested two cohorts of deaf signers who acquired an emerging sign language in Nicaragua at the same age but during different time periods: the first cohort of signers acquired the language in its infancy, and 10 y later the second cohort of signers acquired the language in a more complex form.Wefound that the second-cohort signers, now in their 20s, used more consistent spatial language than the first-cohort signers, now in their 30s. Correspondingly, they outperformed the first cohort in spatially guided searches, both when they were disoriented and when an array was rotated. Consistent linguistic marking of left-right relations correlated with search performance under disorientation, whereas consistent marking of ground information correlated with search in rotated arrays. Human spatial cognition therefore is modulated by the acquisition of a rich language.


Daly R.A.,Pennsylvania State University | Sprinkle T.B.,Pennsylvania State University | O'Dea C.P.,Rochester Institute of Technology | O'Dea C.P.,Harvard - Smithsonian Center for Astrophysics | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

Beam power is a fundamental parameter that describes, in part, the state of a supermassive black hole system. Determining the beam powers of powerful classical double radio sources requires substantial observing time, so it would be useful to determine the relationship between beam power and radio power so that radio power could be used as a proxy for beam power. A sample of 31 powerful classical double radio sources with previously determined beam and radio powers is studied; the sources have redshifts between about 0.056 and 1.8. It is found that the relationship between beam power, L j, and radio power, P, is well described by logL j≈ 0.84(±0.14)logP+ 2.15(±0.07), where both L j and P are in units of 10 44ergs -1. This indicates that beam power is converted to radio power with an efficiency of about 0.7per cent. The ratio of beam power to radio power is studied as a function of redshift; there is no significant evidence for redshift evolution of this ratio over the redshift range studied. The relationship is consistent with empirical results obtained by Cavagnolo et al. for radio sources in gas-rich environments, which are primarily Fanaroff-Riley type I sources, and with the theoretical predictions of Willott et al. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.


Compere G.,Harvard University | Compere G.,Free University of Colombia | Song W.,Harvard University | Strominger A.,Harvard University | Strominger A.,Radcliffe Institute for Advanced Study
Journal of High Energy Physics | Year: 2013

Classical two-dimensional Liouville gravity is often considered in conformal gauge which has a residual left and right Virasoro symmetry algebra. We consider an alternate, chiral, gauge which has a residual right Virasoro Kac-Moody algebra, and no left Virasoro algebra. The Kac-Moody zero mode is the left-moving energy. Dirac brackets of the constrained Hamiltonian theory are derived, and the residual symmetries are shown to be generated by integrals of the conserved chiral currents. The central charge and Kac-Moody level are computed. The possible existence of a corresponding quantum theory is discussed. © 2013 SISSA, Trieste, Italy.


Compere G.,Harvard University | Compere G.,Free University of Colombia | Song W.,Harvard University | Strominger A.,Harvard University | Strominger A.,Radcliffe Institute for Advanced Study
Journal of High Energy Physics | Year: 2013

New chiral boundary conditions are found for quantum gravity with matter on AdS3. The associated asymptotic symmetry group is generated by a single right-moving U(1) Kac-Moody-Virasoro algebra with cR=3ℓ/ 2G. The Kac-Moody zero mode generates global left-moving translations and equals, for a BTZ black hole, the sum of the total mass and spin. The level is positive about the global vacuum and negative in the black hole sector, corresponding to ergosphere formation. Realizations arising in Chern-Simons gravity and string theory are analyzed. The new boundary conditions are shown to naturally arise for warped AdS3 in the limit that the warp parameter is taken to zero. © 2013 SISSA, Trieste, Italy.


News Article | November 4, 2016
Site: phys.org

On a recent morning, the University of Arizona professor of astronomy and physics toggled between a recipe for French pancakes and a series of complex computer simulations tracing the outline of a black hole. "Life goes on," said Psaltis, the 2016–2017 Shutzer Fellow at Harvard's Radcliffe Institute for Advanced Study, who is working on capturing the first-ever image of the massive dark void at the center of the Milky Way, the one scientists think is sucking up any matter or radiation that wanders too close to its event horizon, or point of no return. "In the morning, you do black holes," said Psaltis, "in the evening, you make Nutella crepes for your kids." Prioritizing his time is second nature for Psaltis, a lead scientist on the Event Horizon Telescope (EHT) project, a multinational effort involving more than 100 researchers, including his wife, former Radcliffe fellow Feryal Özel, and a series of super-powered radio telescopes scattered around the globe. Next spring those telescopes will turn the Earth into one giant eye when they all point to Sagittarius A*—the black hole at the center of the galaxy first forecast by Albert Einstein and his theory of general relativity, and since then the subject of study by countless theoretical physicists, among them the famous cosmic detective Stephen Hawking. During his fellowship, Psaltis will refine the computer simulations he and his team will use when analyzing EHT data to determine the black hole's size and shape. Their results could prove that Einstein's theory—the notion that gravity is due to the curvature of the continuum known as space-time—is exact. Or, perhaps, just a little bit off. "What we are looking for is not a description of gravity," he said, "but the description that happens to be the one that describes our universe." To make those calculations, researchers will need to see what has thus far been invisible. But how exactly do you capture the image of a spinning, giant black abyss? You don't, said Psaltis. You take a picture of its shadow. Swirling around Sagittarius A* are charged particles that have been ejected from the surface of nearby stars. Moving at supersonic speeds, those particles heat up millions of degrees to form a shining mass of plasma, or "accretion disk," around the edge of the black hole before they are engulfed. "The plasma is so hot that it is actually glowing in the radio waves detected by the telescopes," said Psaltis. "You put a black hole in front of that glowing plasma and you get a shadow, you get a silhouette." But, as the special effects team for the movie "Interstellar" discovered, producing a realistic image of a black hole is hugely time-consuming. (Some individual frames of the film reportedly took 100 hours to render.) Eager to accelerate the process, Psaltis and his team hacked into their computer's graphics card, the circuit board that controls how images appear on the screen, and gave it a little something extra. "We made it program those chips to do the rendering in the presence of a black hole. … Our codes are so fast that now we use a type of Xbox to control the process with our hands because there's no way to type fast enough to do it." If the image Psaltis and his colleagues produce is perfectly round, it will indicate Einstein was entirely correct. But if the image starts to warp and bend, it means his theory might need some tweaking. "That nice circle that you see here has a particular size, has a particular shape only because Einstein's theory told us so," said Psaltis, pointing to a simulation on his screen. "If the theory is different, both the size and the shape will be different. "The shape of the shadow can be used to tell us exactly what that gravitational field looks like outside that black hole," he added. "And by measuring that, either we will be able to say if Einstein's theory predicts it 100 percent, or if there are small tweaks that we need to add in order to get it right … this is the smoking gun as far as Einstein's gravity is concerned." Psaltis' current project has deep Harvard roots. In the 1990s, he and Özel were both on campus, Psaltis doing postdoctoral research, his future wife pursuing her Ph.D. Together they collaborated with Ramesh Narayan, the Thomas Dudley Cabot Professor of the Natural Sciences, on early simulations that explored what happens to the plasma around a black hole. That research helped determine that the radio wavelength that would give them the best chance at seeing the black hole's event horizon was roughly one millimeter long. "We found that the plasma becomes more and more transparent as you go to a higher and higher frequency and that's what we calculated, where you need to make that observation in order to be able to peer through the plasma," said Psaltis. At one millimeter you "see the black hole's shadow," he said. The work builds on research by Sheperd Doeleman, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics and principal investigator for the Event Horizon project. It was Doeleman who first measured the size of the emitting region of the accretion disk, in 2008. Skeptics persist. Despite its potential to advance understanding of black holes and render a key scientific judgment on Einstein's work, research like Psaltis' leaves some doubting an effect for life on Earth when Sagittarius A* is 26,000 light-years away. The native of Greece, who said he gets that question "all the time," dons his philosopher's hat to answer it. Such endeavors have a foot in both the past and future, he noted, and can also illuminate specific events and ideas, from the Big Bang to investigations into parallel universes. Equally important is the notion that today's research might have its greatest impact tomorrow, Psaltis said. To make his case, he cited the work of the German mathematician Bernhard Riemann, who challenged the accepted model of Euclidian geometry in the 1800s by imagining a world in which two parallel lines ultimately crossed. Einstein would go on to base general relativity on Riemann's mathematical framework. "Not even in his wildest dreams could Riemann have predicted that," said Psaltis. "But if he had not asked in the 1800s, 'Is there any way to make two parallel lines cross?' we would not have Einstein's theories, or GPS, since your phone makes calculations based on Einstein's theories to determine where you are. "Abstract thought is good for intellectual curiosity," he added. "You never can tell where that can take you." Explore further: Black holes come to the big screen

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