3,662 research outputs found
Antiphosphatidylserine antibody as a cause of multiple dural venous sinus thromboses and ST-elevation myocardial infarction
Objective: Rare disease Background: Antiphospholipid syndrome (APS) is an autoimmune disease characterized by antibodies directed against phos-pholipids on plasma membranes. Through unclear mechanisms, APS confers hypercoagulability. APS may cause recurrent thromboses in the arterial and venous vasculature. We report a case of primary APS resulting in cerebral venous thrombosis and ST-elevation myocardial infarction (STEMI) for which only antiphosphatidylserine (aPS) IgM antibody was positive after extensive investigation. Case Report: A 48-year-old male was admitted after a witnessed generalized seizure with subsequent confusion. Imaging demonstrated thrombosis of multiple central nervous system (CNS) sinuses, including the superior sagittal sinus and bilateral transverse sinuses. The patient was heparinized with aggressive hydration, which proved inadequate, prompting endovascular thrombectomy. Three months later, despite anticoagulation therapy, the patient developed a STEMI when International Normalized Ratio (INR) was 1.8. Echocardiogram (ECHO) and PAN CT scan were normal. Initial coagulation studies demonstrated normal anticardiolipin antibody, prothrombin time, partial thromboplastin time, and platelet count. Outpatient coagulation studies revealed normal an-tithrombin III, protein C/S, hemoglobin electrophoresis, homocysteine, anti-b2 glycoprotein 1 antibodies, and D-Dimer. Factor V Leiden, JAK 2 mutation, prothrombin gene mutation, and tests for paroxysmal nocturnal he-moglobinuria (PNH) were negative. A positive phosphatidylserine IgM was detected. The patient was continued on warfarin (10 mg daily) with a target INR of 3.0–3.5 and clopidogrel (75 mg daily). Conclusions: Despite extensive investigation, this patient only showed evidence of elevated aPS IgM antibodies, likely contributing to his CNS venous sinus thromboses and STEMI. It is important to screen for antiphosphatidylserine antibodies in cases of unprovoked thrombosis when standard thrombophilia analysis is unrevealing. This will assist in identifying pathogenicity and help prevent recurrence of subsequent thromboses. © Am J Case Rep, 2018
Entanglement of mechanical oscillators coupled to a non-equilibrium environment
Recent experiments aim at cooling nanomechanical resonators to the ground
state by coupling them to non-equilibrium environments in order to observe
quantum effects such as entanglement. This raises the general question of how
such environments affect entanglement. Here we show that there is an optimal
dissipation strength for which the entanglement between two coupled oscillators
is maximized. Our results are established with the help of a general framework
of exact quantum Langevin equations valid for arbitrary bath spectra, in and
out of equilibrium. We point out why the commonly employed Lindblad approach
fails to give even a qualitatively correct picture
Fermionic Mach-Zehnder interferometer subject to a quantum bath
We study fermions in a Mach-Zehnder interferometer, subject to a
quantum-mechanical environment leading to inelastic scattering, decoherence,
renormalization effects, and time-dependent conductance fluctuations. Both the
loss of interference contrast as well as the shot noise are calculated, using
equations of motion and leading order perturbation theory. The full dependence
of the shot-noise correction on setup parameters, voltage, temperature and the
bath spectrum is presented. We find an interesting contribution due to
correlations between the fluctuating renormalized phase shift and the output
current, discuss the limiting behaviours at low and high voltages, and compare
with simpler models of dephasing.Comment: 5 pages, 3 figure
Position-squared coupling in a tunable photonic crystal optomechanical cavity
We present the design, fabrication, and characterization of a planar silicon
photonic crystal cavity in which large position-squared optomechanical coupling
is realized. The device consists of a double-slotted photonic crystal structure
in which motion of a central beam mode couples to two high-Q optical modes
localized around each slot. Electrostatic tuning of the structure is used to
controllably hybridize the optical modes into supermodes which couple in a
quadratic fashion to the motion of the beam. From independent measurements of
the anti-crossing of the optical modes and of the optical spring effect, the
position-squared vacuum coupling rate is measured to be as large as 245 Hz to
the fundamental in-plane mechanical resonance of the structure at 8.7MHz, which
in displacement units corresponds to a coupling coefficient of 1 THz/nm.
This level of position-squared coupling is approximately five orders of
magnitude larger than in conventional Fabry-Perot cavity systems.Comment: 11 pages, 6 figure
Quantum Signatures of the Optomechanical Instability
In the past few years, coupling strengths between light and mechanical motion
in optomechanical setups have improved by orders of magnitude. Here we show
that, in the standard setup under continuous laser illumination, the steady
state of the mechanical oscillator can develop a non-classical, strongly
negative Wigner density if the optomechanical coupling is large at the
single-photon level. Because of its robustness, such a Wigner density can be
mapped using optical homodyne tomography. These features are observed near the
onset of the instability towards self-induced oscillations. We show that there
are also distinct signatures in the photon-photon correlation function
in that regime, including oscillations decaying on a time scale
not only much longer than the optical cavity decay time, but even longer than
the \emph{mechanical} decay time.Comment: 6 pages including 1 appendix. 6 Figures. Correcte
Free-space quantum links under diverse weather conditions
Free-space optical communication links are promising channels for
establishing secure quantum communication. Here we study the transmission of
nonclassical light through a turbulent atmospheric link under diverse weather
conditions, including rain or haze. To include these effects, the theory of
light transmission through atmospheric links in the elliptic-beam approximation
presented by Vasylyev et al. [D. Vasylyev et al., Phys. Rev. Lett. 117, 090501
(2016); arXiv:1604.01373] is further generalized.It is demonstrated, with good
agreement between theory and experiment, that low-intensity rain merely
contributes additional deterministic losses, whereas haze also introduces
additional beam deformations of the transmitted light. Based on these results,
we study theoretically the transmission of quadrature squeezing and Gaussian
entanglement under these weather conditions.Comment: 14 pages, 8 figure
The Global Imperative for Teacher Education: Opportunities for Comparative and International Education
In the context of globalization, teacher education has to respond to the global imperative by helping pre-service teachers develop global consciousness and awareness (Apple, 2011; Zhao, 2010). This paper addresses this imperative by first identifying the spaces for global competencies in teacher education standards at the national, regional, state, and institutional levels. Next, we analyze two universities’ attempts to internationalize teacher education programs and demonstrate how the lack of specificity in teacher education standards emerge as gaps in the curriculum and in pre-service teacher learning. We argue that re-fashioned comparative and international education courses could address these gaps by developing students’ conceptual understandings of global processes and their impact on education. The ultimate purpose of such courses will be to challenge pre-service teachers’ ethnocentric assumptions about education and to foster a planetary relational view necessary for the development of a more just modernity on the global scale
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