717 research outputs found
Inertial Control of the VIRGO Superattenuator
The VIRGO superattenuator (SA) is effective in depressing the seismic noise
below the thermal noise level above 4 Hz. On the other hand, the residual
mirror motion associated to the SA normal modes can saturate the dynamics of
the interferometer locking system. This motion is reduced implementing a
wideband (DC-5 Hz) multidimensional control (the so called inertial damping)
which makes use of both accelerometers and position sensors and of a DSP
system. Feedback forces are exerted by coil-magnet actuators on the top of the
inverted pendulum. The inertial damping is successful in reducing the mirror
motion within the requirements. The results are presented.Comment: 7 pages, 6 figures, Talk at the 3rd Amaldi Conference on
Gravitational Waves Experiment, Caltech, Pasadena, 12-16 July 199
Advanced Virgo. Investigating gravity and the universe in the land of Galileo
Advanced Virgo, rivelatore interferometrico di onde gravitazionali di seconda generazione, è in fase avanzata di costruzione e comincerà a prendere dati nel 2016. Insieme ad Advanced LIGO realizzerà un network mondiale che ha l’ambizione di aprire una nuova finestra osservativa sull’universo.Advanced Virgo, a second-generation interferometric gravitational wave detector, is at an advanced stage of construction and will start taking data in 2016. Together with Advanced LIGO it will constitute a worldwide network, with the ambition of opening a new observation window on the universe
Surface Texturing of n- and p-Doped c-Si Using a Novel Plasma Chemical Texturing Process
Abstract n- and p-doped c-Si (100) are textured by a SF 6 /O 2 plasma chemical etching, under conditions avoiding ion bombardment. The study of the effects of plasma parameters on morphology and on surface reflectance of textured c-Si reveals a strong impact of silicon doping on texturing characteristics. SF 6 /O 2 plasma etches anisotropically n-type c-Si creating a square-based hillock-like morphology with a surface reflectivity of 6%. Conversely, for p-type Si, a H 2 plasma pretreatment is necessary to activate silicon etching and obtain a nano-textured surface with a reflectivity of 16%
Demonstration of improved charge transfer in graphene/Au nanorods plasmonic hybrids stabilized by benzyl thiol linkers
Hybrids based on graphene decorated with plasmonic gold (Au) nanostructures are being investigated as possible materials combination to add to graphene functionalities of tunable plasmon resonance and enhanced absorption at selected wavelength in the visible-near-infrared region of the spectrum. Here, we report a solution drop-casting approach for fabricating stable hybrids based on chemical vapor deposition (CVD) graphene and Au nanorods, which are able to activate effective charge transfer from graphene. We demonstrate that CVD graphene functionalization by benzyl thiol (BZT) provides the linker to strong anchoring, via S-Au bonds, Au nanorods to graphene. Optical measurements by spectroscopic ellipsometry give evidence of the introduction of plasmon resonances at 1.85 and 2.25 eV in the Au nanorods/BZT/graphene hybrids, which enable surface enhanced Raman scattering (SERS) detection. Furthermore, an effective electron transfer from graphene to Au nanorods, resulting in an enhancement of p-type doping of graphene with a consequent decrease of its sheet resistance, is probed by Raman spectroscopy and corroborated by electrical measurements
Noise parametric identification and whitening for LIGO 40-meter interferometer data
We report the analysis we made on data taken by Caltech 40-meter prototype
interferometer to identify the noise power spectral density and to whiten the
sequence of noise. We concentrate our study on data taken in November 1994, in
particular we analyzed two frames of data: the 18nov94.2.frame and the
19nov94.2.frame.
We show that it is possible to whiten these data, to a good degree of
whiteness, using a high order whitening filter. Moreover we can choose to
whiten only restricted band of frequencies around the region we are interested
in, obtaining a higher level of whiteness.Comment: 11 pages, 15 figures, accepted for publication by Physical Review
Brain morphology and immunohistochemical localization of the gonadotropin-releasing hormone in the bluefin tuna, <i>Thunnus thynnus</i>
The present study was focused on the morphology of the
diencephalic nuclei (likely involved in reproductive functions)
as well as on the distribution of GnRH (gonadotropin-releasing
hormone) in the rhinencephalon, telencephalon and the
diencephalon of the brain of bluefin tuna (Thunnus thynnus)
by means of immunohistochemistry. Bluefin tuna has an
encephalization quotient (QE) similar to that of other large
pelagic fish. Its brain exhibits well-developed optic tecta and
corpus cerebelli. The diencephalic neuron cell bodies
involved in reproductive functions are grouped in two main
nuclei: the nucleus preopticus-periventricularis and the
nucleus lateralis tuberis. The nucleus preopticus-periventricularis
consists of the nucleus periventricularis and the nucleus
preopticus consisting of a few sparse multipolar neurons
in the rostral part and numerous cells closely packed and
arranged in several layers in its aboral part. The nucleus lateralis
tuberis is located in the ventral-lateral area of the
diencephalon and is made up of a number of large multipolar
neurones.
Four different polyclonal primary antibodies against salmon
(s)GnRH, chicken (c)GnRH-II (cGnRH-II 675, cGnRH-II 6)
and sea bream (sb)GnRH were employed in the immunohistochemical
experiments. No immunoreactive structures were
found with anti sbGnRH serum. sGnRH and cGnRH-II antisera
revealed immunoreactivity in the perikarya of the olfactory
bulbs, preopticus-periventricular nucleus, oculomotor
nucleus and midbrain tegmentum. The nucleus lateralis
tuberis showed immunostaining only with anti-sGnRH serum.
Nerve fibres immunoreactive to cGnRH and sGnRH sera were
found in the olfactory bulbs, olfactory nerve and neurohypophysis.
The significance of the distribution of the GnRHimmunoreactive
neuronal structures is discussed
On line power spectra identification and whitening for the noise in interferometric gravitational wave detectors
In this paper we address both to the problem of identifying the noise Power
Spectral Density of interferometric detectors by parametric techniques and to
the problem of the whitening procedure of the sequence of data. We will
concentrate the study on a Power Spectral Density like the one of the
Italian-French detector VIRGO and we show that with a reasonable finite number
of parameters we succeed in modeling a spectrum like the theoretical one of
VIRGO, reproducing all its features. We propose also the use of adaptive
techniques to identify and to whiten on line the data of interferometric
detectors. We analyze the behavior of the adaptive techniques in the field of
stochastic gradient and in the
Least Squares ones.Comment: 28 pages, 21 figures, uses iopart.cls accepted for pubblication on
Classical and Quantum Gravit
Spectroscopic ellipsometry and polarimetry for materials and systems analysis at the nanometer scale: state-of-the-art, potential, and perspectives
This paper discusses the fundamentals, applications, potential, limitations, and future perspectives of polarized light reflection techniques for the characterization of materials and related systems and devices at the nanoscale. These techniques include spectroscopic ellipsometry, polarimetry, and reflectance anisotropy. We give an overview of the various ellipsometry strategies for the measurement and analysis of nanometric films, metal nanoparticles and nanowires, semiconductor nanocrystals, and submicron periodic structures. We show that ellipsometry is capable of more than the determination of thickness and optical properties, and it can be exploited to gain information about process control, geometry factors, anisotropy, defects, and quantum confinement effects of nanostructures
Optical and Electronic NOx Sensors for Applications in Mechatronics
Current production and emerging NOx sensors based on optical and nanomaterials technologies are reviewed. In view of their potential applications in mechatronics, we compared the performance of: i) Quantum cascade lasers (QCL) based photoacoustic (PA) systems; ii) gold nanoparticles as catalytically active materials in field-effect transistor (FET) sensors, and iii) functionalized III-V semiconductor based devices. QCL-based PA sensors for NOx show a detection limit in the sub part-per-million range and are characterized by high selectivity and compact set-up. Electrochemically synthesized gold-nanoparticle FET sensors are able to monitor NOx in a concentration range from 50 to 200 parts per million and are suitable for miniaturization. Porphyrin-functionalized III-V semiconductor materials can be used for the fabrication of a reliable NOx sensor platform characterized by high conductivity, corrosion resistance, and strong surface state coupling
First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data
Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of
continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a
fully coherent search, based on matched filtering, which uses the position and rotational parameters
obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-
noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch
between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have
been developed, allowing a fully coherent search for gravitational waves from known pulsars over a
fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of
11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial
outliers, further studies show no significant evidence for the presence of a gravitational wave signal.
Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of
the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for
the first time. For an additional 3 targets, the median upper limit across the search bands is below the
spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried
out so far
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