4,279 research outputs found
Magnetic ordering and structural phase transitions in strained ultrathin SrRuO/SrTiO superlattice
Ruthenium-based perovskite systems are attractive because their Structural,
electronic and magnetic properties can be systematically engineered.
SrRuO/SrTiO superlattice, with its period consisting of one unit cell
each, is very sensitive to strain change. Our first-principles simulations
reveal that in the high tensile strain region, it transits from a ferromagnetic
(FM) metal to an antiferromagnetic (AFM) insulator with clear tilted octahedra,
while in the low strain region, it is a ferromagnetic metal without octahedra
tilting. Detailed analyses of three spin-down Ru-t orbitals just below
the Fermi level reveal that the splitting of these orbitals underlies these
dramatic phase transitions, with the rotational force constant of RuO
octahedron high up to 16 meV/Deg, 4 times larger than that of TiO.
Differently from nearly all the previous studies, these transitions can be
probed optically through the diagonal and off-diagonal dielectric tensor
elements. For one percent change in strain, our experimental spin moment change
is -0.140.06 , quantitatively consistent with our theoretical value
of -0.1 .Comment: 3 figures, 1 supplementary material, accepted by Phys. Rev. Let
Pure-Past Linear Temporal and Dynamic Logic on Finite Traces
LTLf and LDLf are well-known logics on finite traces. We review PLTLf and PLDLf, their pure- past versions. These are interpreted backward from the end of the trace towards the beginning. Because of this, we can exploit a foundational result on reverse languages to get an exponential improvement, wrt LTLf /LDLf, in computing the corresponding DFA. This exponential improvement is reflected in several forms sequential decision making involving temporal specifications, such as planning and decision problems in non-deterministic and non-Markovian domains. Interestingly, PLTLf (resp. PLDLf ) has the same expressive power as LTLf (resp. LDLf ), but transforming a PLTLf (resp. PLDLf ) formula into its equivalent in LTLf (resp. LDLf ) is quite expensive. Hence, to take advantage of the exponential improvement, properties of interest must be directly expressed in PLTLf /PLTLf
Tunable control of the bandwidth and frequency correlations of entangled photons
We demonstrate experimentally a new technique to control the bandwidth and
the type of frequency correlations (correlation, anticorrelation, and even
uncorrelation) of entangled photons generated by spontaneous parametric
downconversion. The method is based on the control of the group velocities of
the interacting waves. This technique can be applied in any nonlinear medium
and frequency band of interest. It is also demonstrated that this technique
helps enhance the quality of polarization entanglement even when femtosecond
pulses are used as a pump.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Zero and Finite Temperature Quantum Simulations Powered by Quantum Magic
We present a comprehensive approach to quantum simulations at both zero and
finite temperatures, employing a quantum information theoretic perspective and
utilizing the Clifford + Rz transformations. We introduce the "quantum magic
ladder", a natural hierarchy formed by systematically augmenting Clifford
transformations with the addition of Rz gates. These classically simulable
similarity transformations allow us to reduce the quantumness of our system,
conserving vital quantum resources. This reduction in quantumness is essential,
as it simplifies the Hamiltonian and shortens physical circuit-depth,
overcoming constraints imposed by limited error correction. We improve the
performance of both digital and analog quantum computers on ground state and
finite temperature molecular simulations, not only outperforming the
Hartree-Fock solution, but also achieving consistent improvements as we ascend
the quantum magic ladder. By facilitating more efficient quantum simulations,
our approach enables near-term and early fault-tolerant quantum computers to
address novel challenges in quantum chemistry.Comment: 12 pages, 9 figure
Following the best of us to help them: Group member prototypicality and collective action
While considering the role of group-level factors as predictors of collective action, research has overlooked the role of group prototypes in determining willingness to engage in collective action. To begin to investigate this area, we conducted two correlational studies (Ns = 141 and 98) in high schools examining the association between prototypical ingroup members’ desire to engage in collective action and participants’ collective action on behalf of a disadvantaged group (immigrants). Results showed a positive association between these two variables. We also investigated boundaries of this effect, finding that the association emerged when participants lacked personal experiences with the disadvantaged group (cross-group friendships; Study 1) or identified more with their ingroup, an effect also found when including a behavioral measure of collective action (Study 2). Intentions to follow the prototypical ingroup member emerged as the mediator (Study 2). It is worth noting that our methodology allowed us to assess prototypicality in a naturalistic context by calculating a metacontrast ratio for each group member, in line with self-categorization theory’s conceptualization of prototypicality. We discuss the theoretical and practical implications, with reference to the role of prototypicality as a means of social influence and to developing social norms in the context of collective action
Multi-parameter Entanglement in Quantum Interferometry
The role of multi-parameter entanglement in quantum interference from
collinear type-II spontaneous parametric down-conversion is explored using a
variety of aperture shapes and sizes, in regimes of both ultrafast and
continuous-wave pumping. We have developed and experimentally verified a theory
of down-conversion which considers a quantum state that can be concurrently
entangled in frequency, wavevector, and polarization. In particular, we
demonstrate deviations from the familiar triangular interference dip, such as
asymmetry and peaking. These findings improve our capacity to control the
quantum state produced by spontaneous parametric down-conversion, and should
prove useful to those pursuing the many proposed applications of down-converted
light.Comment: submitted to Physical Review
A Spitzer Survey of Novae in M31
We report the results of the first infrared survey of novae in the nearby
spiral galaxy, M31. Both photometric and spectroscopic observations of a sample
of 10 novae (M31N 2006-09c, 2006-10a, 2006-10b, 2006-11a, 2007-07f, 2007-08a,
2007-08d, 2007-10a, 2007-11d, and 2007-11e) were obtained with the Spitzer
Space Telescope. Eight of the novae were observed with the IRAC (all but M31N
2007-11d and 2007-11e) and eight with the IRS (all but 2007-07f and 2007-08a),
resulting in six in common between the two instruments. The observations, which
were obtained between ~3 and ~7 months after discovery, revealed evidence for
dust formation in two of the novae: M31N 2006-10a and (possibly) 2007-07f, and
[Ne II] 12.8 micron line emission in a third (2007-11e). The Spitzer
observations were supplemented with ground-based optical photometric and
spectroscopic data that were used to determine the speed classes and
spectroscopic types of the novae in our survey. After including data for
dust-forming Galactic novae, we show that dust formation timescales are
correlated with nova speed class in that dust typically forms earlier in faster
novae. We conclude that our failure to detect the signature of dust formation
in most of our M31 sample is likely a result of the relatively long delay
between nova eruption and our Spitzer observations. Indeed, the two novae for
which we found evidence of dust formation were the two "slowest" novae in our
sample. Finally, as expected, we found that the majority of the novae in our
sample belong to the Fe II spectroscopic class, with only one clear example of
the He/N class (M31N 2006-10b). Typical of an He/N system, M31N 2006-10b was
the fastest nova in our sample, not detected with the IRS, and just barely
detected in three of the IRAC bands when it was observed ~4 months after
eruption.Comment: 37 pages, 12 figures, accepted for publication in the Astrophysical
Journa
Onychomycosis: Recommendations for Diagnosis, Assessment of Treatment Efficacy, and Specialist Referral. The CONSONANCE Consensus Project
Introduction: Onychomycosis is the most common nail disorder in adults, with high recurrence and relapse rates. Its diagnosis may be difficult by non-experts because the clinical signs may overlap with other dermatoses. The treatment may be challenging, as it should be patient-tailored.
Methods: An online survey was conducted among European Nail Society (ENS) members to provide recommendations on the diagnosis and assessment of distal lateral subungual onychomycosis (DLSO) in non-specialized clinical environments, as well as recommendations for patient referral.
Results: DLSO diagnosis is predominantly based on clinical aspects, and microscopy and fungal culture are commonly employed to establish the diagnosis. Assessment of clinical features is the main method for DLSO follow-up, and the main criterion to define cure is a combination of mycologic cure and clinical cure. The most commonly selected treatments for onychomycosis include oral antifungals, topical antifungals, and nail debridement. According to the nail experts, predisposing factors of DLSO to be evaluated include concurrent tinea pedis diagnosis, immunocompromised status, and diabetes. The minimum clinical aspects to be evaluated for DLSO diagnosis should include subungual hyperkeratosis, white-yellow-orange subungual scales, and absence of salmon-pink coloration. Recommendations for clinical signs that should be evaluated to confirm treatment effectiveness include normal appearance and color of the nail, reduction or absence of scales under the nail, and absence of onycholysis. Recommendations for specialist referral include lack of treatment effectiveness, need of additional therapies, concurrent presence of other diseases or comorbidities, severe DLSO, and presence of a dermatophytoma or involvement of the nail matrix.
Conclusions: According to the surveyed nail experts, after evaluating clinical signs and predisposing factors for DLSO, the diagnosis should include subungual hyperkeratosis, nail color (yellow-orange), and onycholysis and thickening. In cases of severe DLSO, when there is treatment failure, concomitant diseases/comorbidities, presence of a dermatophytoma or involvement of the nail matrix, or involvement of several/all nails, referral should be considered
Hydrogen Two-Photon Continuum Emission from the Horseshoe Filament in NGC 1275
Far ultraviolet emission has been detected from a knot of Halpha emission in
the Horseshoe filament, far out in the NGC 1275 nebula. The flux detected
relative to the brightness of the Halpha line in the same spatial region is
very close to that expected from Hydrogen two-photon continuum emission in the
particle heating model of Ferland et al. (2009) if reddening internal to the
filaments is taken into account. We find no need to invoke other sources of far
ultraviolet emission such as hot stars or emission lines from CIV in
intermediate temperature gas to explain these data.Comment: 9 pages, 8 figures. Accepted for publication in MNRA
How feedback inhibition shapes spike-timing-dependent plasticity and its implications for recent Schizophrenia models
It has been shown that plasticity is not a fixed property but, in fact, changes depending on the location of the synapse on the neuron and/or changes of biophysical parameters. Here we investigate how plasticity is shaped by feedback inhibition in a cortical microcircuit. We use a differential Hebbian learning rule to model spike-timing dependent plasticity and show analytically that the feedback inhibition shortens the time window for LTD during spike-timing dependent plasticity but not for LTP. We then use a realistic GENESIS model to test two hypothesis about interneuron hypofunction and conclude that a reduction in GAD67 is the most likely candidate as the cause for hypofrontality as observed in Schizophrenia
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