3,107 research outputs found
Observational evidence for a spin-up line in the P-Pdot diagram of millisecond pulsars
It is believed that millisecond pulsars attain their fast spins by accreting
matter and angular momentum from companion stars. Theoretical modelling of the
accretion process suggests a spin-up line in the period-period derivative
(-) diagram of millisecond pulsars, which plays an important role
in population studies of radio millisecond pulsars and accreting neutron stars
in X-ray binaries. Here we present observational evidence for such a spin-up
line using a sample of 143 radio pulsars with < 30 ms. We also find that
PSRs~J18233021A and J18242452A, located near the classic spin-up line,
are consistent with the broad population of millisecond pulsars. Finally, we
show that our approach of Bayesian inference can probe accretion physics,
allowing constraints to be placed on the accretion rate and the
disk-magnetosphere interaction.Comment: 10 pages, 4 figures, 2 tables. Accepted for publication by ApJ
Old Story New Tell: The Graphite to Diamond Transition Revisited
Graphite and diamond are two well-known allotropes of carbon with distinct
physical properties due to different atomic connectivity. Graphite has a
layered structure in which the honeycomb carbon sheets can easily glide, while
atoms in diamond are strongly bonded in all three dimensions. The transition
from graphite to diamond has been a central subject in physical science. One
way to turn graphite into diamond is to apply the high pressure and high
temperature (HPHT) conditions. However, atomistic mechanism of this transition
is still under debate. From a series of large-scale molecular dynamics (MD)
simulations, we report a mechanism that the diamond nuclei originate at the
graphite grain boundaries and propagate in two preferred directions. In
addition to the widely accepted [001] direction, we found that the growth along
[120] direction of graphite is even faster. In this scenario, cubic diamond
(CD) is the kinetically favorable product, while hexagonal diamond (HD) would
appear as minor amounts of twinning structures in two main directions.
Following the crystallographic orientation relationship, the coherent interface
t-(100)gr//(11-1)cd + [010]gr//[1-10]cd was also confirmed by high-resolution
transmission electron microscopy (HR-TEM) experiment. The proposed phase
transition mechanism does not only reconcile the longstanding debate regarding
the role of HD in graphite-diamond transition, but also yields the atomistic
insight into microstructure engineering via controlled solid phase transition.Comment: 35 pages, 5 figure
Diniconazole
The asymmetric unit of the title compound [systematic name: (E)-1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pent-1-en-3-ol], C15H17Cl2N3O, contains two molecules in which the dihedral angles between the triazole and benzene rings are 9.4 (2) and 35.0 (2)°. In the crystal, the molecules are linked by O—H⋯N hydrogen bonds, forming C(7) chains propagating in [010]
Experimental Test of Tracking the King Problem
In quantum theory, the retrodiction problem is not as clear as its classical
counterpart because of the uncertainty principle of quantum mechanics. In
classical physics, the measurement outcomes of the present state can be used
directly for predicting the future events and inferring the past events which
is known as retrodiction. However, as a probabilistic theory,
quantum-mechanical retrodiction is a nontrivial problem that has been
investigated for a long time, of which the Mean King Problem is one of the most
extensively studied issues. Here, we present the first experimental test of a
variant of the Mean King Problem, which has a more stringent regulation and is
termed "Tracking the King". We demonstrate that Alice, by harnessing the shared
entanglement and controlled-not gate, can successfully retrodict the choice of
King's measurement without knowing any measurement outcome. Our results also
provide a counterintuitive quantum communication to deliver information hidden
in the choice of measurement.Comment: 16 pages, 5 figures, 2 table
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