1,341 research outputs found
Polarization measurements and their perspectives: PVLAS Phase II
We sketch the proposal for a "PVLAS-Phase II" experiment. The main physics
goal is to achieve the first direct observation of non-linear effects in
electromagnetism predicted by QED and the measurement of the photon-photon
scattering cross section at low energies (1-2 eV). Physical processes such as
ALP and MCP production in a magnetic field could also be accessible if
sensitive enough operation is reached. The short term experimental strategy is
to compact as much as possible the dimensions of the apparatus in order to
bring noise sources under control and to attain a sufficient sensitivity. We
will also briefly mention future pespectives, such as a scheme to implement the
resonant regeneration principle for the detection of ALPs.Comment: Paper submitted to the proceedings of the "4th Patras Workshop on
Axions, WIMPs and WISPs", DESY, Hamburg Site /Germany, 18-21 June 200
Frequency locking to a high-finesse Fabry-Perot cavity of a Frequency doubled Nd:YAG laser used as the optical phase modulator
We report on the frequency locking of a frequency doubled Nd:YAG laser to a
45 000 finesse, 87-cm-long, Fabry-Perot cavity using a modified form of the
Pound-Drever-Hall technique. Necessary signals, such as light phase modulation
and frequency correction feedback, are fed direcly to the infrared pump laser.
This is sufficient to achieve a stable locking of the 532 nm visible beam to
the cavity, also showing that the doubling process does not degrade laser
performances.Comment: submitted to Review of Scientific Instrument
Optical production and detection of dark matter candidates
The PVLAS collaboration is at present running, at the Laboratori Nazionali di
Legnaro of I.N.F.N., Padova, Italy, a very sensitive optical ellipsometer
capable of measuring the small rotations or ellipticities which can be acquired
by a linearly polarized laser beam propagating in vacuum through a transverse
magnetic feld (vacuum magnetic birefringence). The apparatus will also be able
to set new limits on mass and coupling constant of light scalar/pseudoscalar
particles coupling to two photons by both producing and detecting the
hypothetical particles. The axion, introduced to explain parity conservation in
strong interactions, is an example of this class of particles, all of which are
considered possible dark matter candidates. The PVLAS apparatus consists of a
very high finesse (> 140000), 6.4 m long, Fabry-Perot cavity immersed in an
intense dipolar magnetic field (~6.5 T). A linearly polarized laser beam is
frequency locked to the cavity and analysed, using a heterodyne technique, for
rotation and/or ellipticity acquired within the magnetic field.Comment: presented at "Frontier Detectors for Frontier Physics - 8th Pisa
Meeting on Advanced Detectors - May 21-27, 2000" to appear in: Nucl.Instr.
and Meth.
KWISP: an ultra-sensitive force sensor for the Dark Energy sector
An ultra-sensitive opto-mechanical force sensor has been built and tested in
the optics laboratory at INFN Trieste. Its application to experiments in the
Dark Energy sector, such as those for Chameleon-type WISPs, is particularly
attractive, as it enables a search for their direct coupling to matter. We
present here the main characteristics and the absolute force calibration of the
KWISP (Kinetic WISP detection) sensor. It is based on a thin Si3N4
micro-membrane placed inside a Fabry-Perot optical cavity. By monitoring the
cavity characteristic frequencies it is possible to detect the tiny membrane
displacements caused by an applied force. Far from the mechanical resonant
frequency of the membrane, the measured force sensitivity is 5.0e-14
N/sqrt(Hz), corresponding to a displacement sensitivity of 2.5e-15 m/sqrt(Hz),
while near resonance the sensitivity is 1.5e-14 N/sqrt(Hz), reaching the
estimated thermal limit, or, in terms of displacement, 7.5e-16 N/sqrt(Hz).
These displacement sensitivities are comparable to those that can be achieved
by large interferometric gravitational wave detectors.Comment: 9 pages, 8 figures in colo
Confocal laser scanning microscope, raman microscopy and western blotting to evaluate inflammatory response after myocardial infarction
Cardiac muscle necrosis is associated with inflammatory cascade that clears the infarct from dead
cells and matrix debris, and then replaces the damaged tissue with scar, through three overlapping phases: the
inflammatory phase, the proliferative phase and the maturation phase.
Western blotting, laser confocal microscopy, Raman microscopy are valuable tools for studying the inflammatory
response following myocardial infarction both humoral and cellular phase, allowing the identification and
semiquantitative analysis of proteins produced during the inflammatory cascade activation and the topographical distribution
and expression of proteins and cells involved in myocardial inflammation. Confocal laser scanning microscopy
(CLSM) is a relatively new technique for microscopic imaging, that allows greater resolution, optical sectioning of the
sample and three-dimensional reconstruction of the same sample. Western blotting used to detect the presence of a specific
protein with antibody-antigen interaction in the midst of a complex protein mixture extracted from cells, produced
semi-quantitative data quite easy to interpret. Confocal Raman microscopy combines the three-dimensional optical resolution
of confocal microscopy and the sensitivity to molecular vibrations, which characterizes Raman spectroscopy.
The combined use of western blotting and confocal microscope allows detecting the presence of proteins in the sample
and trying to observe the exact location within the tissue, or the topographical distribution of the same. Once demonstrated
the presence of proteins (cytokines, chemokines, etc.) is important to know the topographical distribution, obtaining in this
way additional information regarding the extension of the inflammatory process in function of the time stayed from the
time of myocardial infarction. These methods may be useful to study and define the expression of a wide range of inflammatory
mediators at several different timepoints providing a more detailed analysis of the time course of the infarct
Detecting solar chameleons through radiation pressure
Light scalar fields can drive the accelerated expansion of the universe.
Hence, they are obvious dark energy candidates. To make such models compatible
with tests of General Relativity in the solar system and "fifth force" searches
on Earth, one needs to screen them. One possibility is the so-called
"chameleon" mechanism, which renders an effective mass depending on the local
matter density. If chameleon particles exist, they can be produced in the sun
and detected on Earth exploiting the equivalent of a radiation pressure. Since
their effective mass scales with the local matter density, chameleons can be
reflected by a dense medium if their effective mass becomes greater than their
total energy. Thus, under appropriate conditions, a flux of solar chameleons
may be sensed by detecting the total instantaneous momentum transferred to a
suitable opto-mechanical force/pressure sensor. We calculate the solar
chameleon spectrum and the reach in the chameleon parameter space of an
experiment using the preliminary results from a force/pressure sensor,
currently under development at INFN Trieste, to be mounted in the focal plane
of one of the X-Ray telescopes of the CAST experiment at CERN. We show, that
such an experiment signifies a pioneering effort probing uncharted chameleon
parameter space.Comment: revised versio
Solution processible organic transistors and circuits based on a C-70 methanofullerene
Published versio
Pro bono models in law schools and the student experience: Challenges and opportunities moving forward
Pro Bono and Clinical Legal Education during periods of disruption: Challenges and opportunities
- …