2,578 research outputs found
The intricate Galaxy disk: velocity asymmetries in Gaia-TGAS
We use the Gaia-TGAS data to compare the transverse velocities in Galactic
longitude (coming from proper motions and parallaxes) in the Milky Way disk for
negative and positive longitudes as a function of distance. The transverse
velocities are strongly asymmetric and deviate significantly from the
expectations for an axisymmetric Galaxy. The value and sign of the asymmetry
changes at spatial scales of several tens of degrees in Galactic longitude and
about 0.5 kpc in distance. The asymmetry is statistically significant at 95%
confidence level for 57% of the region probed, which extends up to ~1.2 kpc. A
percentage of 24% of the region studied shows absolute differences at this
confidence level larger than 5 km/s and 7% larger than 10 km/s. The asymmetry
pattern shows mild variations in the vertical direction and with stellar type.
A first qualitative comparison with spiral arm models indicates that the arms
are unlikely to be the main source of the asymmetry. We briefly discuss
alternative origins. This is the first time that global all-sky asymmetries are
detected in the Milky Way kinematics, beyond the local neighbourhood, and with
a purely astrometric sample.Comment: Accepted for publication in A&A Letter
Quantum disentanglers
It is not possible to disentangle a qubit in an unknown state from a
set of (N-1) ancilla qubits prepared in a specific reference state . That
is, it is not possible to {\em perfectly} perform the transformation
. The question is then how well we can do? We consider a number of
different methods of extracting an unknown state from an entangled state formed
from that qubit and a set of ancilla qubits in an known state. Measuring the
whole system is, as expected, the least effective method. We present various
quantum ``devices'' which disentangle the unknown qubit from the set of ancilla
qubits. In particular, we present the optimal universal disentangler which
disentangles the unknown qubit with the fidelity which does not depend on the
state of the qubit, and a probabilistic disentangler which performs the perfect
disentangling transformation, but with a probability less than one.Comment: 8 pages, 1 eps figur
Optimal Universal Disentangling Machine for Two Qubit Quantum States
We derive the optimal curve satisfied by the reduction factors, in the case
of universal disentangling machine which uses only local operations.
Impossibility of constructing a better disentangling machine, by using
non-local operations, is discussed.Comment: 15 pages, 2 eps figures, 1 section added, 1 eps figure added, minor
corrections, 2 reference numbers correcte
Interpretation Bias Characterizes Trait Rumination
Background and Objectives: Rumination, a maladaptive cognitive style of responding to negative mood, is thought to be maintained by a variety of cognitive biases. However, it is unknown whether rumination is characterized by interpretation biases.
Methods: Two experiments examined the link between rumination and interpretation biases, revealed in lexical-decision tasks (LDT). A homograph with both benign and ruminative or otherwise negative meaning was presented on each trial and followed by a letter string, to which participants responded by judging whether it was a word or a non-word. Letter strings were nonwords or words related or unrelated to one meaning of the homograph.
Results: In both experiments, faster latencies to respond to targets related to the ruminative meaning of the homographs were produced by students with higher scores on self-report measures of rumination. Moreover, these biases were associated with both brooding, the maladaptive form of rumination, and reflection, the more adaptive component. No measure of rumination was significantly correlated with general biases toward negative meaning (Experiment 1) or with threatening interpretations of homographs (Experiment 2).
Limitations: The paucity of available rumination-related homographs dictated the use of nonfully randomized stimuli presentation (Experiment 1) or the use of only one set of the meanings associated with the homographs (Experiment 2).
Conclusions: Rumination is associated with a tendency to interpret ambiguous information in a rumination-consistent manner. This tendency may exacerbate ruminative thinking and can possibly be a target for future intervention
Gaia DR2 view of the Lupus V-VI clouds: the candidate diskless young stellar objects are mainly background contaminants
Extensive surveys of star-forming regions with Spitzer have revealed
populations of disk-bearing young stellar objects. These have provided crucial
constraints, such as the timescale of dispersal of protoplanetary disks,
obtained by carefully combining infrared data with spectroscopic or X-ray data.
While observations in various regions agree with the general trend of
decreasing disk fraction with age, the Lupus V and VI regions appeared to have
been at odds, having an extremely low disk fraction. Here we show, using the
recent Gaia data release 2 (DR2), that these extremely low disk fractions are
actually due to a very high contamination by background giants. Out of the 83
candidate young stellar objects (YSOs) in these clouds observed by Gaia, only
five have distances of 150 pc, similar to YSOs in the other Lupus clouds, and
have similar proper motions to other members in this star-forming complex. Of
these five targets, four have optically thick (Class II) disks. On the one
hand, this result resolves the conundrum of the puzzling low disk fraction in
these clouds, while, on the other hand, it further clarifies the need to
confirm the Spitzer selected diskless population with other tracers, especially
in regions at low galactic latitude like Lupus V and VI. The use of Gaia
astrometry is now an independent and reliable way to further assess the
membership of candidate YSOs in these, and potentially other, star-forming
regions.Comment: Accepted for publication on Astronomy&Astrophysics Letter
Realization of Optimal Disentanglement by Teleportation via Separable Channel
We discuss here the best disentanglement processes of states of two two-level
systems which belong to (i) the universal set, (ii) the set in which the states
of one party lie on a single great circle of the Bloch sphere, and (iii) the
set in which the states of one party commute with each other, by teleporting
the states of one party (on which the disentangling machine is acting) through
three particular type of separable channels, each of which is a mixture of Bell
states. In the general scenario, by teleporting one party's state of an
arbitrary entangled state of two two-level parties through some mixture of Bell
states, we have shown that this entangled state can be made separable by using
a physically realizable map , acting on one party's states, if
, where
(for ), and .Comment: 20 pages Late
Nonlinear Qubit Transformations
We generalise our previous results of universal linear manipulations [Phys.
Rev. A63, 032304 (2001)] to investigate three types of nonlinear qubit
transformations using measurement and quantum based schemes. Firstly, nonlinear
rotations are studied. We rotate different parts of a Bloch sphere in opposite
directions about the z-axis. The second transformation is a map which sends a
qubit to its orthogonal state (which we define as ORTHOG). We consider the case
when the ORTHOG is applied to only a partial area of a Bloch sphere. We also
study nonlinear general transformation, i.e. (theta,phi)->(theta-alpha,phi),
again, applied only to part of the Bloch sphere. In order to achieve these
three operations, we consider different measurement preparations and derive the
optimal average (instead of universal) quantum unitary transformations. We also
introduce a simple method for a qubit measurement and its application to other
cases.Comment: minor corrections. To appear in PR
Std fimbriae-fucose interaction increases Salmonella-induced intestinal inflammation and prolongs colonization
Author summary The intestinal epithelium is a crucial biological interface, interacting with both commensal and pathogenic microorganisms. It’s lined with heavily glycosylated proteins and glycolipids which can act as both attachment sites and energy sources for intestinal bacteria. Fut2, the enzyme governing epithelial α1,2-fucosylation, has been implicated in the interaction between microbes and intestinal epithelial cells. Salmonella is one of the most important bacterial gastrointestinal pathogens affecting millions of people worldwide. Salmonella possesses fimbrial and non-fimbrial adhesins which can be used to adhere to host cells. Here we show that Salmonella expresses Std fimbriae in the gastrointestinal tract in vivo and exploit Std fimbriae to bind fucosylated structures in the mucus and on the intestinal epithelium. Furthermore, we demonstrate that the Std fimbriae-fucose interaction is necessary for bacterial colonization of the intestine and for triggering intestinal inflammation. These data lend new insights into bacterial adhesion-epithelial interactions which are essential for bacterial pathogenesis and key factors in determining tissue tropism and host susceptibility to infectious disease
Probabilistic teleportation of unknown two-particle state via POVM
We propose a scheme for probabilistic teleportation of unknown two-particle
state with partly entangled four-particle state via POVM. In this scheme the
teleportation of unknown two-particle state can be realized with certain
probability by performing two Bell state measurements, a proper POVM and a
unitary transformation.Comment: 5 pages, no figur
Learning design studio: educational practice as design inquiry of learning
Recently we are urged to transform education into an evidence based profession, and promote scientific standards or practice. These calls are not new – they seem to emerge every few years. We do not argue with their goal, but we contend that the suitable frame of reference is the paradigm of design science, rather than the common metaphor of medical research. This paper proposes Design Inquiry of Learning as a projection of educational design science into a professional domain, and offers the Learning Design Studio as a pedagogical manifestation of this approach. The learning design studio is a collaborative, blended, project based framework for training educators in effective and evidence-based use of educational technology. We present its theoretical underpinnings, note its fundamental principles and structures, and review three independent cases where it has been trialed. The results show that this model is effective in developing learners’ theoretical knowledge as well as their practical skills, and allows them to link the two. However, it requires a considerable commitment of both learners and tutors, and may not be applicable in more casual settings
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