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Patricia Larsen, Anthony Challinor, Blake D Sherwin, Daisy Mak
Delensing is an increasingly important technique to reverse the gravitational lensing of the cosmic microwave background (CMB) and thus reveal primordial signals the lensing may obscure. We present a first demonstration of delensing on Planck temperature maps using the cosmic infrared background (CIB). Reversing the lensing deflections in Planck CMB temperature maps using a linear combination of the 545 and 857 GHz maps as a lensing tracer, we find that the lensing effects in the temperature power spectrum are reduced in a manner consistent with theoretical expectations...
October 7, 2016: Physical Review Letters
Kimitake Hayasaki, Abraham Loeb
Galaxy mergers produce supermassive black hole binaries, which emit gravitational waves prior to their coalescence. We perform three-dimensional hydrodynamic simulations to study the tidal disruption of stars by such a binary in the final centuries of its life. We find that the gas stream of the stellar debris moves chaotically in the binary potential and forms accretion disks around both black holes. The accretion light curve is modulated over the binary orbital period owing to relativistic beaming. This periodic signal allows to detect the decay of the binary orbit due to gravitational wave emission by observing two tidal disruption events that are separated by more than a decade...
October 21, 2016: Scientific Reports
Dafni Krystallidou, Peter Thompson
Visual input powerfully modulates the dynamics of tactile orientation perception. This study investigated the transfer of the tilt aftereffect (TAE) from vision to somatosensation. In a visual tilt adaptation paradigm, participants were exposed to clockwise or anticlockwise visual tilt, followed by three brief tactile two-point stimuli delivered on their forehead. In a two-alternative forced choice task, participants had to indicate whether the haptic stimulus was tilted to the right or left. Repeated exposure to oriented visual gratings produced a tactile TAE, such that the subsequent tactile stimuli appeared tilted toward the opposite direction...
September 2016: I-Perception
Viktor S Kokhan, Marina I Matveeva, Azat Mukhametov, Andrey S Shtemberg
Space flight factors (SFF) significantly affect the operating activity of astronauts during deep space missions. Gravitational overloads, hypo-magnetic field and ionizing radiation are the main SFF that perturb the normal activity of the central nervous system (CNS). Acute and chronic CNS risks include alterations in cognitive abilities, reduction of motor functions and behavioural changes. Multiple experimental works have been devoted to the SFF effects on integrative functional activity of the brain; however, the model parameters utilized have not always been ideal and consistent...
October 15, 2016: Neuroscience and Biobehavioral Reviews
Wanyue Wang, Natalia Dounskaia
How gravity influences neural control of arm movements remains under debate. We tested three alternative interpretations suggested by previous research: (1) that muscular control includes two components, tonic which compensates for gravity and phasic which produces the movement; (2) that there is a tendency to exploit gravity to reduce muscle effort; and (3) that there is a tendency to use a trailing pattern of joint control during which either the shoulder or elbow is rotated actively and the other joint rotates predominantly passively, and to exploit gravity for control of the passively rotated joint...
October 14, 2016: Neuroscience
M N Chernodub
We show that the scale (conformal) anomaly in field theories leads to new anomalous transport effects that emerge in an external electromagnetic field in an inhomogeneous gravitational background. In inflating geometry the QED scale anomaly locally generates an electric current that flows in opposite direction with respect to background electric field (the scale electric effect). In a static spatially inhomogeneous gravitational background the dissipationless electric current flows transversely both to the magnetic field axis and to the gradient of the inhomogeneity (the scale magnetic effect)...
September 30, 2016: Physical Review Letters
Hugo Chauvet, Olivier Pouliquen, Yoël Forterre, Valérie Legué, Bruno Moulia
Gravity perception plays a key role in how plants develop and adapt to environmental changes. However, more than a century after the pioneering work of Darwin, little is known on the sensing mechanism. Using a centrifugal device combined with growth kinematics imaging, we show that shoot gravitropic responses to steady levels of gravity in four representative angiosperm species is independent of gravity intensity. All gravitropic responses tested are dependent only on the angle of inclination from the direction of gravity...
October 14, 2016: Scientific Reports
Neville D Gai, Ashkan A Malayeri, David A Bluemke
PURPOSE: To develop and assess a new technique for three-dimensional (3D) full lung T1 and T2* mapping using a single free breathing scan during a clinically feasible time. MATERIALS AND METHODS: A 3D stack of dual-echo ultrashort echo time (UTE) radial acquisition interleaved with and without a WET (water suppression enhanced through T1 effects) saturation pulse was used to map T1 and T2* simultaneously in a single scan. Correction for modulation due to multiple views per segment was derived...
October 11, 2016: Journal of Magnetic Resonance Imaging: JMRI
Soichiro Morisaki, Jun'ichi Yokoyama, Kazunari Eda, Yousuke Itoh
We introduce a new analysis method to deal with stationary non-Gaussian noises in gravitational wave detectors in terms of the independent component analysis. First, we consider the simplest case where the detector outputs are linear combinations of the inputs, consisting of signals and various noises, and show that this method may be helpful to increase the signal-to-noise ratio. Next, we take into account the time delay between the inputs and the outputs. Finally, we extend our method to nonlinearly correlated noises and show that our method can identify the coupling coefficients and remove non-Gaussian noises...
2016: Proceedings of the Japan Academy. Series B, Physical and Biological Sciences
Ue-Li Pen, Neil Turok
We point out a surprising consequence of the usually assumed initial conditions for cosmological perturbations. Namely, a spectrum of Gaussian, linear, adiabatic, scalar, growing mode perturbations not only creates acoustic oscillations of the kind observed on very large scales today, it also leads to the production of shocks in the radiation fluid of the very early Universe. Shocks cause departures from local thermal equilibrium as well as create vorticity and gravitational waves. For a scale-invariant spectrum and standard model physics, shocks form for temperatures 1  GeV<T<10^{7}  GeV...
September 23, 2016: Physical Review Letters
Laura M Pérez, John M Carpenter, Sean M Andrews, Luca Ricci, Andrea Isella, Hendrik Linz, Anneila I Sargent, David J Wilner, Thomas Henning, Adam T Deller, Claire J Chandler, Cornelis P Dullemond, Joseph Lazio, Karl M Menten, Stuartt A Corder, Shaye Storm, Leonardo Testi, Marco Tazzari, Woojin Kwon, Nuria Calvet, Jane S Greaves, Robert J Harris, Lee G Mundy
Gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. However, previous observations that showed spiral structure were not able to probe disk midplanes, where most of the mass is concentrated and where planet formation takes place. Using the Atacama Large Millimeter/submillimeter Array, we detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding the young star Elias 2-27. The arms extend to the disk outer regions and can be traced down to the midplane...
September 30, 2016: Science
C T Russell, C A Raymond, E Ammannito, D L Buczkowski, M C De Sanctis, H Hiesinger, R Jaumann, A S Konopliv, H Y McSween, A Nathues, R S Park, C M Pieters, T H Prettyman, T B McCord, L A McFadden, S Mottola, M T Zuber, S P Joy, C Polanskey, M D Rayman, J C Castillo-Rogez, P J Chi, J P Combe, A Ermakov, R R Fu, M Hoffmann, Y D Jia, S D King, D J Lawrence, J-Y Li, S Marchi, F Preusker, T Roatsch, O Ruesch, P Schenk, M N Villarreal, N Yamashita
On 6 March 2015, Dawn arrived at Ceres to find a dark, desiccated surface punctuated by small, bright areas. Parts of Ceres' surface are heavily cratered, but the largest expected craters are absent. Ceres appears gravitationally relaxed at only the longest wavelengths, implying a mechanically strong lithosphere with a weaker deep interior. Ceres' dry exterior displays hydroxylated silicates, including ammoniated clays of endogenous origin. The possibility of abundant volatiles at depth is supported by geomorphologic features such as flat crater floors with pits, lobate flows of materials, and a singular mountain that appears to be an extrusive cryovolcanic dome...
September 2, 2016: Science
Steven A Balbus
A conserved stress energy tensor for weak field gravitational waves propagating in vacuum is derived directly from the linearized general relativistic wave equation alone, for an arbitrary gauge. In any harmonic gauge, the form of the tensor leads directly to the classical expression for the outgoing wave energy. The method described here, however, is a much simpler, shorter, and more physically motivated approach than is the customary procedure, which involves a lengthy and cumbersome second-order (in wave-amplitude) calculation starting with the Einstein tensor...
October 3, 2016: Proceedings of the National Academy of Sciences of the United States of America
C Pfister, J Kaniewski, M Tomamichel, A Mantri, R Schmucker, N McMahon, G Milburn, S Wehner
Quantum mechanics and the theory of gravity are presently not compatible. A particular question is whether gravity causes decoherence. Several models for gravitational decoherence have been proposed, not all of which can be described quantum mechanically. Since quantum mechanics may need to be modified, one may question the use of quantum mechanics as a calculational tool to draw conclusions from the data of experiments concerning gravity. Here we propose a general method to estimate gravitational decoherence in an experiment that allows us to draw conclusions in any physical theory where the no-signalling principle holds, even if quantum mechanics needs to be modified...
October 3, 2016: Nature Communications
Eric Braaten, Abhishek Mohapatra, Hong Zhang
If the dark matter particles are axions, gravity can cause them to coalesce into axion stars, which are stable gravitationally bound systems of axions. In the previously known solutions for axion stars, gravity and the attractive force between pairs of axions are balanced by the kinetic pressure. The mass of these dilute axion stars cannot exceed a critical mass, which is about 10^{-14}M_{⊙} if the axion mass is 10^{-4}  eV. We study axion stars using a simple approximation to the effective potential of the nonrelativistic effective field theory for axions...
September 16, 2016: Physical Review Letters
Dariusz Świerad, Sebastian Häfner, Stefan Vogt, Bertrand Venon, David Holleville, Sébastien Bize, André Kulosa, Sebastian Bode, Yeshpal Singh, Kai Bongs, Ernst Maria Rasel, Jérôme Lodewyck, Rodolphe Le Targat, Christian Lisdat, Uwe Sterr
The increasing performance of optical lattice clocks has made them attractive for scientific applications in space and thus has pushed the development of their components including the interrogation lasers of the clock transitions towards being suitable for space, which amongst others requires making them more power efficient, radiation hardened, smaller, lighter as well as more mechanically stable. Here we present the development towards a space-compatible interrogation laser system for a strontium lattice clock constructed within the Space Optical Clock (SOC2) project where we have concentrated on mechanical rigidity and size...
September 26, 2016: Scientific Reports
Jenifer N Saldanha, Santosh Pandey, Jo Anne Powell-Coffman
As we seek to recognize the opportunities of advanced aerospace technologies and spaceflight, it is increasingly important to understand the impacts of hypergravity, defined as gravitational forces greater than those present on the earth's surface. The nematode Caenorhabditis elegans has been established as a powerful model to study the effects of altered gravity regimens and has displayed remarkable resilience to space travel. In this study, we investigate the effects of short-term and defined hypergravity exposure on C...
August 2016: Life Sciences in Space Research
Otmar Bock, Nils Bury
INTRODUCTION: To flip a switch "down," our motor system can normally rely on concordant visual, gravitational, and egocentric cues about the vertical. However, divers must sometimes perform this task while visual cues are limited and gravitational cues are misaligned with egocentric cues. Astronauts must also flip switches "down" in absence of gravitational cues. Our study evaluates this ability using a laboratory simulation. METHODS: The subjects were 24 healthy volunteers who were blindfolded, tilted into different angles of roll, and asked to silence an alarm by flipping a switch "down...
2016: Aerospace Medicine and Human Performance
Henning Vahlbruch, Moritz Mehmet, Karsten Danzmann, Roman Schnabel
Squeezed states of light belong to the most prominent nonclassical resources. They have compelling applications in metrology, which has been demonstrated by their routine exploitation for improving the sensitivity of a gravitational-wave detector since 2010. Here, we report on the direct measurement of 15 dB squeezed vacuum states of light and their application to calibrate the quantum efficiency of photoelectric detection. The object of calibration is a customized InGaAs positive intrinsic negative (p-i-n) photodiode optimized for high external quantum efficiency...
September 9, 2016: Physical Review Letters
Ramona Ritzmann, Kathrin Freyler, Anne Krause, Albert Gollhofer
On our astronomical neighbours Mars and the Moon, bouncing movements are the preferred locomotor techniques. During bouncing, the stretch-shortening cycle describes the muscular activation pattern. This study aimed to identify gravity-dependent changes in kinematic and neuromuscular characteristics in the stretch-shortening cycle. Hence, neuromuscular control of limb muscles as well as correlations between the muscles' pre-activation, reflex components, and the force output were assessed in lunar, Martian, and Earth gravity...
September 22, 2016: Journal of Applied Physiology
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