367 research outputs found
Stripe-like quasi-nondiffracting optical lattices
We introduce stripe-like quasi-nondiffracting lattices that can be generated
via spatial spectrum engineering. The complexity of the spatial shapes of such
lattices and the distance of their almost diffractionless propagation depend on
the width of their ring-like spatial spectrum. Stripe-like lattices are
extended in one direction and are localized in the orthogonal one, thereby
creating either straight or curved in any desired fashion optically-induced
channels that may be used for optical trapping, optical manipulation, or
optical lattices for quantum and nonlinear optics applications. As an
illustrative example, here we show their potential for spatial soliton control.
Complex networks consisting of several intersecting or joining stripe-like
lattices suited to a particular application may also be constructed.Comment: 6 pages, 4 figures, to appear in Optics Expres
A method to generate complex quasi-nondiffracting optical lattices
We put forward a powerful technique that allows generating
quasi-non-diffracting light beams with a variety of complex transverse shapes
and topologies. We show that, e.g., spiraling patterns, patterns featuring
curved or bent bright stripes, or patterns featuring arbitrary combinations of
harmonic, Bessel, Mathieu and parabolic beams occupying different domains in
the transverse plane can be produced. The quasi-non-diffracting patterns open
up a wealth of opportunities for the manipulation of matter and optical waves,
colloidal and living particles, with applications in biophysics, and quantum,
nonlinear and atom optics.Comment: 14 pages, 6 figures, to appear in Physical Review Letter
Tetanus toxin-induced protein kinase C activation and elevated serotonin levels in the perinatal rat brain
AbstractA single intracerebral injection of tetanus toxin (TeTox) is able to produce a time-dependent translocation of Ca2+-phosphatidylserine-dependent protein kinase C (PKC) in close-to-tenn rat brain. TeTox-triggered translocation of PKC is dose- and time-dependent, can be prevented by tetanus antitoxin, and does not occur upon administration of toxin fragments B and C. TeTox-triggered PKC translocation is accompanied by a timedependent increase in brain serotonin (5-HT). Increase of brain 5-HT is independent of monoamine oxidase inhibition by pargyline. Phorbol ester and TeTox cause a significant increase in serotonin while H-7, a kinase inhibitor, does not affect serotonin levels but abolishes the effect of TeTox. Gangliosides prevent TeTox-triggered 5-HT increase. The data are consistent with the possibility that TeTox acts effectively on the serotonergic innervation, presumably in conjunction with PKC to cause accumulation of serotonin
Lattice-supported surface solitons in nonlocal nonlinear media
We reveal that lattice interfaces imprinted in nonlocal nonlinear media
support surface solitons that do not exist in other similar settings, including
interfaces of local and nonlocal uniform materials. We show the impact of
nonlocality on the domains of existence and stability of the surface solitons,
focusing on new types of dipole solitons residing partially inside the optical
lattice. We find that such solitons feature strongly asymmetric shapes and that
they are stable in large parts of their existence domain.Comment: 13 pages, 3 figures, to appear in Optics Letter
General quasi-non-spreading linear three-dimensional wave-packets
We introduce a general approach for generation of sets of three-dimensional
quasi-non-spreading wavepackets propagating in linear media, also referred to
as linear light bullets. The spectrum of rigorously non-spreading wavepackets
in media with anomalous group velocity dispersion is localized on the surface
of a sphere, thus drastically restricting the possible wavepacket shapes.
However, broadening slightly the spectrum affords the generation of a large
variety of quasi-non-spreading distributions featuring complex topologies and
shapes in space and time that are of interest in different areas, such as
biophysics or nanosurgery. Here we discuss the method and show several
illustrative examples of its potential.Comment: 3 pages, 4 figures, to appear in Optics Letter
Generation of arbitrary complex quasi-non-diffracting optical patterns
Due to their unique ability to maintain an intensity distribution upon
propagation, non-diffracting light fields are used extensively in various areas
of science, including optical tweezers, nonlinear optics and quantum optics, in
applications where complex transverse field distributions are required.
However, the number and type of rigorously non-diffracting beams is severely
limited because their symmetry is dictated by one of the coordinate system
where the Helmholtz equation governing beam propagation is separable. Here, we
demonstrate a powerful technique that allows the generation of a rich variety
of quasi-non-diffracting optical beams featuring nearly arbitrary intensity
distributions in the transverse plane. These can be readily engineered via
modifications of the angular spectrum of the beam in order to meet the
requirements of particular applications. Such beams are not rigorously
non-diffracting but they maintain their shape over large distances, which may
be tuned by varying the width of the angular spectrum. We report the generation
of unique spiral patterns and patterns involving arbitrary combinations of
truncated harmonic, Bessel, Mathieu, or parabolic beams occupying different
spatial domains. Optical trapping experiments illustrate the opto-mechanical
properties of such beams.Comment: 11 pages, 7 figures, to be published in Optics Expres
Propagation of solitons in thermal media with periodic nonlinearity
We address the existence and properties of solitons in layered thermal media
made of alternating focusing and defocusing layers. Such structures support
robust bright solitons even if the averaged nonlinearity is defocusing. We show
that non-oscillating solitons may form in any of the focusing domains, even in
those located close to the sample edge, in contrast to uniform thermal media
where light beams always oscillate when not launched exactly on the sample
center. Stable multipole solitons may include more than four spots in layered
media.Comment: 12 pages, 3 figures, to appear in Optics Letter
Exploring working conditions as determinants of job satisfaction: an empirical test among Catalonia service workers
Job satisfaction is particularly important in the service industry since it involves direct contact with customers and thus has a direct influence on company performance. We analyzed the impact of ten working conditions on job satisfaction by means of structural equation modelling in a representative stratified random sample of 1553 service sector employees in Catalonia (Spain). We found significant effects in social aspects (recognition of a job well done and social support), followed by psychological loads (emotional demands and job insecurity) and by task contents (development & meaning and predictability). These variables explained 50% of the variance in job satisfaction
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