3,193 research outputs found
Effects of inhalable particulate matter on blood coagulation.
BACKGROUND: Particulate matter (PM) exposure has been linked to increased risk of cardiovascular disease, possibly resulting from hypercoagulability and thrombosis. Lung and systemic inflammation resulting from PM inhalation may activate blood coagulation, but mechanisms for PM-related hypercoagulability are still largely unknown. OBJECTIVES: To identify coagulation mechanisms activated by PM in a population with well-characterized exposure. METHODS: We measured prothrombin time (PT), activated partial thromboplastin time, endogenous thrombin potentials (ETPs) with/without exogenous triggers and with/without soluble thrombomodulin, tissue-type plasminogen activator (t-PA) antigen, D-dimer and C-reactive protein (CRP) in 37 workers in a steel production plant with well-characterized exposure to PM with aerodynamic diameter of < 1 mum (PM(1)) and coarse PM (PM(10) - PM(1)). Blood samples were collected from each subject on the first (baseline) and last (postexposure) day of a 4-day work week. We analyzed differences between baseline and postexposure levels using a paired Student's t-test. We fitted multivariate mixed-regression models to estimate the associations of interquartile range PM(1) and coarse PM exposure with parameter levels. RESULTS: None of the parameters showed any significant changes from baseline in postexposure samples. However, exposure levels were associated with shorter PT (beta[PM(1)] = -0.33 s, P = 0.08; beta[PM(coarse)] = - 0.33 s, P = 0.01), and higher ETP without exogenous triggers and with thrombomodulin (beta[PM(1)] = + 99 nm min, P = 0.02; beta[PM(coarse)] = + 66 nm min, P = 0.05), t-PA (beta[PM(1)] = + 0.72 ng mL(-1), P = 0.01; beta[PM(coarse)] = + 0.88 ng mL(-1), P = 0.04), and CRP (beta[PM(1)] = + 0.59 mg L(-1), P = 0.03; beta[PM(coarse)] = + 0.48 mg L(-1), P = 0.01). CONCLUSIONS: PM exposure did not show any short-term effect within the week of the study. The association of PM exposure with PT, ETP and CRP provides some evidence of long-term effects on inflammation and coagulation
Phonon Squeezed States Generated by Second Order Raman Scattering
We study squeezed states of phonons, which allow a reduction in the quantum
fluctuations of the atomic displacements to below the zero-point quantum noise
level of coherent phonon states. We investigate the generation of squeezed
phonon states using a second order Raman scattering process. We calculate the
expectation values and fluctuations of both the atomic displacement and the
lattice amplitude operators, as well as the effects of the phonon squeezed
states on macroscopically measurable quantities, such as changes in the
dielectric constant. These results are compared with recent experiments.Comment: 4 pages, REVTE
Propagation of squeezed radiation through amplifying or absorbing random media
We analyse how nonclassical features of squeezed radiation (in particular the
sub-Poissonian noise) are degraded when it is transmitted through an amplifying
or absorbing medium with randomly located scattering centra. Both the cases of
direct photodetection and of homodyne detection are considered. Explicit
results are obtained for the dependence of the Fano factor (the ratio of the
noise power and the mean current) on the degree of squeezing of the incident
state, on the length and the mean free path of the medium, the temperature, and
on the absorption or amplification rate.Comment: 8 pages, 4 figure
Driving the atom by atomic fluorescence: analytic results for the power and noise spectra
We study how the spectral properties of resonance fluorescence propagate
through a two-atom system. Within the weak-driving-field approximation we find
that, as we go from one atom to the next, the power spectrum exhibits both
sub-natural linewidth narrowing and large asymmetries while the spectrum of
squeezing narrows but remains otherwise unchanged. Analytical results for the
observed spectral features of the fluorescence are provided and their origin is
thoroughly discussed.Comment: 13 pages, 5 figures; to be published in Phys. Rev. A Changed title
and conten
Revisiting the Bragg reflector to illustrate modern developments in optics
Copyright © 2014 American Association of Physics TeachersA series of thin layers of alternating refractive index are known to make a good optical mirror over certain bands of frequency. Such a device, often termed the Bragg reflector, is usually introduced to students in isolation from other parts of the curriculum. Here, we show that the basic physics of wave propagation through a stratified medium can be used to illustrate some more modern developments in optics and quantum physics, from transfer matrix techniques to the optical properties of cold trapped atoms and optomechanical cooling. We also show a simple example of how such systems exhibit an appreciable level of optical nonreciprocity.Engineering and Physical Sciences Research Council (EPSRC)National Natural Science Foundation of ChinaNational Basic Research Program of ChinaCRUI-British CouncilAzione Integrata MIURFondo di Ateneo of Brescia Universit
Band theory in the context of the Hamilton-Jacobi formulation
In the one-dimensional periodic potential case, we formulate the condition of
Bloch periodicity for the reduced action by using the relation between the wave
function and the reduced action established in the context of the equivalence
postulate of quantum mechanics. Then, without appealing to the wave function
properties, we reproduce the well-known dispersion relations which predict the
band structure for the energy spectrum in the Kr\"onig-Penney model.Comment: 10 pages, no figure
"Fresnel light drag in a coherently driven moving medium"
We theoretically study how the phase of a light plane wave propagating in a resonant medium under electromagnetically induced transparency (EIT) is affected by the uniform motion of the medium. For cuprous oxide (Cu2O), where EIT can be implemented through a typical pump-probe configuration, the resonant probe beam experiences a phase shift (Fresnel-Fizeau effect) that may vary over a wide range of values, positive or negative, and even vanishing, due to the combined effects of the strong frequency dispersion and anisotropy both induced by the pump. The use of such a coherently driven dragging medium may improve by at least 1 order of magnitude the sensitivity at low velocity in optical drag experiments
Field quantization for open optical cavities
We study the quantum properties of the electromagnetic field in optical
cavities coupled to an arbitrary number of escape channels. We consider both
inhomogeneous dielectric resonators with a scalar dielectric constant
and cavities defined by mirrors of arbitrary shape. Using
the Feshbach projector technique we quantize the field in terms of a set of
resonator and bath modes. We rigorously show that the field Hamiltonian reduces
to the system--and--bath Hamiltonian of quantum optics. The field dynamics is
investigated using the input--output theory of Gardiner and Collet. In the case
of strong coupling to the external radiation field we find spectrally
overlapping resonator modes. The mode dynamics is coupled due to the damping
and noise inflicted by the external field. For wave chaotic resonators the mode
dynamics is determined by a non--Hermitean random matrix. Upon including an
amplifying medium, our dynamics of open-resonator modes may serve as a starting
point for a quantum theory of random lasing.Comment: 16 pages, added references, corrected typo
Three-dimensional quantization of the electromagnetic field in dispersive and absorbing inhomogeneous dielectrics
A quantization scheme for the phenomenological Maxwell theory of the full
electromagnetic field in an inhomogeneous three-dimensional, dispersive and
absorbing dielectric medium is developed. The classical Maxwell equations with
spatially varying and Kramers-Kronig consistent permittivity are regarded as
operator-valued field equations, introducing additional current- and
charge-density operator fields in order to take into account the noise
associated with the dissipation in the medium. It is shown that the equal-time
commutation relations between the fundamental electromagnetic fields
and and the potentials and in the Coulomb gauge
can be expressed in terms of the Green tensor of the classical problem. From
the Green tensors for bulk material and an inhomogeneous medium consisting of
two bulk dielectrics with a common planar interface it is explicitly proven
that the well-known equal-time commutation relations of QED are preserved
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