50 research outputs found
Interaction induced fractional Bloch and tunneling oscillations
We study the dynamics of few interacting bosons in a one-dimensional lattice
with dc bias. In the absence of interactions the system displays single
particle Bloch oscillations. For strong interaction the Bloch oscillation
regime reemerges with fractional Bloch periods which are inversely proportional
to the number of bosons clustered into a bound state. The interaction strength
is affecting the oscillation amplitude. Excellent agreement is found between
numerical data and a composite particle dynamics approach. For specific values
of the interaction strength a particle will tunnel from the interacting cloud
to a well defined distant lattice location.Comment: 4 pages, 4 figure
Detection of the tagged or untagged photons in acousto-optic imaging of thick highly scattering media by photorefractive adaptive holography
We propose an original adaptive wavefront holographic setup based on the
photorefractive effect (PR), to make real-time measurements of acousto-optic
signals in thick scattering media, with a high flux collection at high rates
for breast tumor detection. We describe here our present state of art and
understanding on the problem of breast imaging with PR detection of the
acousto-optic signal
Theoretical study of Acousto-optical coherence tomography using random phase jumps on US and light
Acousto-Optical Coherence Tomography (AOCT) is variant of Acousto Optic
Imaging (called also ultrasonic modulation imaging) that makes possible to get
z resolution with acoustic and optic Continuous Wave (CW) beams. We describe
here theoretically the AOCT e ect, and we show that the Acousto Optic tagged
photons remains coherent if they are generated within a speci c z region of the
sample. We quantify the z selectivity for both the tagged photon eld, and for
the M. Lesa re et al. photorefractive signal
Heterodyne detection of multiply scattered monochromatic light with a multipixel detector
International audienceA new technique is presented for measuring the spectral broadening of light that has been multiply scattered from scatterers in motion. In our method the scattered light is detected by a heterodyne receiver that uses a CCD as a multipixel detector. We obtain the frequency spectrum of the scattered light by sweeping the heterodyne local oscillator frequency. Our detection scheme combines a high optical etendue (product of the surface by the detection solid angle) with an optimal detection of the scattered photons (shot noise). Using this technique, we measure, in vivo, the frequency spectrum of the light scattered through the breast of a female volunteer
Acousto-optic laser optical feedback imaging
We present a photon noise and diffraction limited imaging method combining
the imaging laser and ultrasonic waves. The laser optical feedback imaging
(LOFI) technique is an ultrasensitive imaging method for imaging objects
through or embedded within a scattering medium. However, LOFI performances are
dramatically limited by parasitic optical feedback occurring in the
experimental setup. In this work, we have tagged the ballistic photons by an
acousto-optic effect in order to filter the parasitic feedback effect and to
reach the theoretical and ultimate sensitivity of the LOFI technique. We
present the principle and the experimental setup of the acousto-optic laser
optical feedback imaging (AO-LOFI) technique, and we demonstrate the
suppression of the parasitic feedback
A Novel Mechanism for Zika Virus Host-Cell Binding
Zika virus (ZIKV) recently emerged in the Western Hemisphere with previously unrecognized or unreported clinical presentations. Here, we identify two putative binding mechanisms of ancestral and emergent ZIKV strains featuring the envelope (E) protein residue asparagine 154 (ASN154) and viral phosphatidylserine (PS). Synthetic peptides representing the region containing ASN154 from strains PRVABC59 (Puerto Rico 2015) and MR_766 (Uganda 1947) were exposed to neuronal cells and fibroblasts to model ZIKV E protein/cell interactions and bound MDCK or Vero cells and primary neurons significantly. Peptides significantly inhibited Vero cell infectivity by ZIKV strains MR_766 and PRVABC59, indicating that this region represents a putative binding mechanism of ancestral African ZIKV strains and emergent Western Hemisphere strains. Pretreatment of ZIKV strains MR_766 and PRVABC59 with the PS-binding protein annexin V significantly inhibited replication of PRVABC59 but not MR_766, suggesting that Western hemisphere strains may additionally be capable of utilizing PS-mediated entry to infect host cells. These data indicate that the region surrounding E protein ASN154 is capable of binding fibroblasts and primary neuronal cells and that PS-mediated entry may be a secondary mechanism for infectivity utilized by Western Hemisphere strains
High resolution infrared absorption spectra, crystal field, and relaxation processes in CsCdBr_3:Pr^3+
High resolution low-temperature absorption spectra of 0.2% Pr^3+ doped
CsCdBr_3 were measured in the spectral region 2000--7000 cm-1. Positions and
widths of the crystal field levels within the 3H5, 3H4, 3F2, and 3F3 multiplets
of the Pr^3+ main center have been determined. Hyperfine structure of several
spectral lines has been found. Crystal field calculations were carried out in
the framework of the semiphenomenological exchange charge model (ECM).
Parameters of the ECM were determined by fitting to the measured total
splittings of the 3H4 and 3H6 multiplets and to the observed in this work
hyperfine splittings of the crystal field levels. One- and two-phonon
relaxation rates were calculated using the phonon Green's functions of the
perfect (CsCdBr_3) and locally perturbed (impurity dimer centers in
CsCdBr_3:Pr^3+) crystal lattice. Comparison with the measured linewidths
confirmed an essential redistribution of the phonon density of states in
CsCdBr_3 crystals doped with rare-earth ions.Comment: 16 pages, 5 tables, 3 figure
Biophotonique Générale Optique & Imageries pour le Diagnostic dans les Sciences du Vivant et en Médecine
International audienc
Fast wavefront adaptive holography in Nd:YVO4 for ultrasound optical tomography imaging
International audienceSeveral approaches exist to perform acousto-optic imaging of multiple-scattering media such as biological samples. Up to now, most of the coherent detection methods use holographic setup based on photore-fractive crystals such as BSO or SPS. One of the issue of these techniques is the moderate response time compared to the speckle decorrelation time in biological sample. We introduce a new approach for the holographic detection based on two-wave mixing in a Nd:YVO 4 gain medium enabling us to perform a fast wavefront adaption (50 ”s) of the speckle field from a multiple-scattering sample