4,229 research outputs found
The origin of pointing: Evidence for the touch hypothesis
Pointing gestures play a foundational role in human language, but up to now, we have not known where these gestures come from. Here, we investigated the hypothesis that pointing originates in touch. We found, first, that when pointing at a target, children and adults oriented their fingers not as though trying to create an “}arrow{” that picks out the target but instead as though they were aiming to touch it; second, that when pointing at a target at an angle, participants rotated their wrists to match that angle as they would if they were trying to touch the target; and last, that young children interpret pointing gestures as if they were attempts to touch things, not as arrows. These results provide the first substantial evidence that pointing originates in touch
Planning assistance for the NASA 30/20 GHz program. Network control architecture study.
Network Control Architecture for a 30/20 GHz flight experiment system operating in the Time Division Multiple Access (TDMA) was studied. Architecture development, identification of processing functions, and performance requirements for the Master Control Station (MCS), diversity trunking stations, and Customer Premises Service (CPS) stations are covered. Preliminary hardware and software processing requirements as well as budgetary cost estimates for the network control system are given. For the trunking system control, areas covered include on board SS-TDMA switch organization, frame structure, acquisition and synchronization, channel assignment, fade detection and adaptive power control, on board oscillator control, and terrestrial network timing. For the CPS control, they include on board processing and adaptive forward error correction control
Thermalization and the chromo-Weibel instability
Despite the apparent success of ideal hydrodynamics in describing the
elliptic flow data which have been produced at Brookhaven National Lab's
Relativistic Heavy Ion Collider, one lingering question remains: is the use of
ideal hydrodynamics at times t < 1 fm/c justified? In order to justify its use
a method for rapidly producing isotropic thermal matter at RHIC energies is
required. One of the chief obstacles to early isotropization/thermalization is
the rapid longitudinal expansion of the matter during the earliest times after
the initial nuclear impact. As a result of this expansion the parton
distribution functions become locally anisotropic in momentum space. In
contrast to locally isotropic plasmas anisotropic plasmas have a spectrum of
soft unstable modes which are characterized by exponential growth of transverse
chromo-magnetic/-electric fields at short times. This instability is the QCD
analogue of the Weibel instability of QED. Parametrically the chromo-Weibel
instability provides the fastest method for generation of soft background
fields and dominates the short-time dynamics of the system.Comment: 8 pages, 4 figures, Invited plenary talk given at the 19th
International Conference on Ultrarelativistic Nucleus-Nucleus Collisions:
Quark Matter 2006 (QM 2006), Shanghai, China, 14-20 Nov 200
Letter, D. B. Strickland to Elizabeth Champion, December 28, 1838
This handwritten letter, dated December 28, 1838, is written from D. B. Strickland to Elizabeth Champion informing her that he has arrived at his destination. Strickland goes on to tell her all the places he\u27s visited in Illinois and how busy he expects to be while in Vandalia. Strickland compares Illinois to New England, deciding that he prefers New England because of it\u27s health and luxuries. He goes on to describe two deaths he\u27s aware of since being in Vandalia, that of a legislator and that of citizen. The conclusion of the letter is written cross-hatch across the first three pages in a lighter ink and is difficult to read.https://scholarsjunction.msstate.edu/fvw-manuscripts-original-manuscripts/1199/thumbnail.jp
Collective modes of an Anisotropic Quark-Gluon Plasma II
We continue our exploration of the collective modes of an anisotropic quark
gluon plasma by extending our previous analysis to arbitrary Riemann sheets. We
demonstrate that in the presence of momentum-space anisotropies in the parton
distribution functions there are new relevant singularities on the neighboring
unphysical sheets. We then show that for sufficiently strong anisotropies that
these singularities move into the region of spacelike momentum and their effect
can extend down to the physical sheet. In order to demonstrate this explicitly
we consider the polarization tensor for gluons propagating parallel to the
anisotropy direction. We derive analytic expressions for the gluon structure
functions in this case and then analytically continue them to unphysical
Riemann sheets. Using the resulting analytic continuations we numerically
determine the position of the unphysical singularities. We then show that in
the limit of infinite contraction of the distribution function along the
anisotropy direction that the unphysical singularities move onto the physical
sheet and result in real spacelike modes at large momenta for all
"out-of-plane" angles of propagation.Comment: 13 pages, 8 figure
QGP collective effects and jet transport
We present numerical simulations of the SU(2) Boltzmann-Vlasov equation
including both hard elastic particle collisions and soft interactions mediated
by classical Yang-Mills fields. We provide an estimate of the coupling of jets
to a hot isotropic plasma, which is independent of infrared cutoffs. In
addition, we investigate jet propagation in anisotropic plasmas, as created in
heavy-ion collisions. The broadening of jets is found to be stronger along the
beam line than in azimuth due to the creation of field configurations with
B_t>E_t and E_z>B_z via plasma instabilities.Comment: 4 pages, 5 figures. Presented at the 20th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions: Quark Matter 2008 (QM2008),
Jaipur, India, 4-10 Feb 200
On the Physical Origin of OVI Absorption-Line Systems
We present a unified analysis of the O{\sc vi} absorption-lines seen in the
disk and halo of the Milky Way, high velocity clouds, the Magellanic Clouds,
starburst galaxies, and the intergalactic medium. We show that these disparate
systems define a simple relationship between the O{\sc vi} column density and
absorption-line width that is independent of the Oxygen abundance over the
range O/H 10% to twice solar. We show that this relation is exactly that
predicted theoretically as a radiatively cooling flow of hot gas passes through
the coronal temperature regime - independent of its density or metallicity (for
O/H 0.1 solar). Since most of the intregalactic O{\sc vi} clouds obey
this relation, we infer that they can not have metallicities less than a few
percent solar. In order to be able to cool radiatively in less than a Hubble
time, the intergalactic clouds must be smaller than 1 Mpc in size. We
show that the cooling column densities for the O{\sc iv}, O{\sc v}, Ne{\sc v},
and Ne{\sc vi} ions are comparable to those seen in O{\sc vi}. This is also
true for the Li-like ions Ne{\sc viii}, Mg{\sc x}, and Si{\sc xii} (if the gas
is cooling from K). All these ions have strong resonance lines
in the extreme-ultraviolet spectral range, and would be accessible to at
0.2 to 0.8. We also show that the Li-like ions can be used to probe
radiatively cooling gas at temperatures an order-of-magnitude higher than where
their ionic fraction peaks. We calculate that the H-like (He-like) O, Ne, Mg,
Si, and S ions have cooling columns of cm. The O{\sc vii},
O{\sc viii}, and Ne{\sc ix} X-ray absorption-lines towards PKS 2155-304 may
arise in radiatively cooling gas in the Galactic disk or halo.Comment: 25 pages, 5 figure
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