1,195 research outputs found
Status of the GINGER project
Large frame Ring laser gyroscopes, based on the Sagnac effect, are top
sensitivity instrumentation to measure angular velocity with respect to the
fixed stars. GINGER (Gyroscopes IN GEneral Relativity) project foresees the
construction of an array of three large dimension ring laser gyroscopes,
rigidly connected to the Earth. GINGER has the potentiality to measure general
relativity effects and Lorentz Violation in the gravity sector, once a
sensitivity of , or better, of the Earth rotation rate is obtained.
Being attached to the Earth crust, the array will also provide useful data for
geophysical investigation. For this purpose, it is at present under
construction as part of the multi-components observatory called Underground
Geophysics at Gran Sasso (UGSS). Sensitivity is the key point to determine the
relevance of this instrument for fundamental science. The most recent progress
in the sensitivity measurement, obtained on a ring laser prototype called
GINGERINO, indicates that GINGER should reach the level of 1 part in
of the Earth rotation rate.Comment: 6 pages, 5 figure
Analysis of ring laser gyroscopes including laser dynamics
Inertial sensors stimulate very large interest, not only for their
application but also for fundamental physics tests. Ring laser gyros, which
measure angular rotation rate, are certainly among the most sensitive inertial
sensors, with excellent dynamic range and bandwidth. Large area ring laser
gyros are routinely able to measure fractions of prad/s, with high duty cycle
and bandwidth, providing fast, direct and local measurement of relevant
geodetic and geophysical signals. Improvements of a factor would open
the windows for general relativity tests, as the GINGER project, an Earth based
experiment aiming at the Lense-Thirring test at level. However, it is
well known that the dynamics of the laser induces non-linearities, and those
effects are more evident in small scale instruments. Sensitivity and accuracy
improvements are always worthwhile, and in general there is demand for high
sensitivity environmental study and development of inertial platforms, where
small scale transportable instruments should be used. We discuss a novel
technique to analyse the data, aiming at studying and removing those
non-linearity. The analysis is applied to the two ring laser prototypes GP2 and
GINGERINO, and angular rotation rate evaluated with the new and standard
methods are compared. The improvement is evident, it shows that the
back-scatter problem of the ring laser gyros is negligible with a proper
analysis of the data, improving the performances of large scale ring laser
gyros, but also indicating that small scale instruments with sensitivity of
nrad/s are feasible.Comment: 9 pages and 7 figure
Observational and Experimental Gravity
We indicate the progress of experimental gravity, present an outlook in this
field, and summarise the Observational/Experimental Parallel Session together
with a related plenary talk on gravitational waves of the 2nd LeCosPA
Symposium.Comment: 1 figure, Second LeCosPa Simposium, December 2015, Taipei Taiwa
Sagnac Gyroscopes and the GINGER Project
Large-frame optical Sagnac gyroscopes, more commonly called ring laser gyroscopes, are considered the only device able to provide fast and very high sensitivity measurement of the length of the day (LOD) and of the Earth rotation axis variations. Several large-frame Sagnac gyros are presently operative with a high duty cycle and a sensitivity well below fractions of nrad/s in 1 s measurement. At present, other inertial angular rotation sensors are not competitive with ring laser gyroscopes. The feasibility depends on the so-called hetero-lithic ring lasers. The present state of the art is reported and the feasibility of the main goals for geodesy discussed
Functional and Environmental Performances of Novel Electrolytic Membranes for PEM Fuel Cells: A Lab-Scale Case Study
Despite being the most employed polymer electrolyte for proton exchange membrane fuel
cells (PEMFCs), Nafion® has several limitations: expensiveness, poor performance when exposed to temperatures higher than 80 °C, and its potential as a source of environmentally persistent and toxic compounds (i.e., per- and polyfluoroalkyl substances, known as PFASs) when disposed of. This work explores the functional and environmental performances of three potential PFAS-free alternatives to Nafion® as electrolytic membranes in PEMFCs: sulfonated graphene oxide (SGO), graphene oxide-naphthalene sulfonate (GONS), and borate-reinforced sulfonated graphene oxide (BSGO). Investigated via ATR-FTIR spectroscopy, TGA, and cross-sectional SEM, the membranes show an effective functionalization of GO and good thermal stability. Functional properties are determined via Ion Exchange Capacity (IEC) evaluation, Electrochemical Impedance Spectroscopy, and tensile tests. In terms of IEC, the innovative materials outperform Nafion® 212. Proton conductivities at 80 °C of SGO (1.15 S cm-1) and GONS (1.71 S cm-1) are higher than that of the commercial electrolyte (0.56 S cm-1). At the same time, the membranes are investigated via Life Cycle Assessment (LCA) to uncover potential environmental hotspots. Results show that energy consumption during manufacture is the main environmental concern for the three membranes. A sensitivity analysis demonstrates that the impact could be significantly reduced if the production procedures were scaled up. Among the three alternatives, SGO shows the best trade-off between proton conductivity and environmental impact, even though performance results from real-life applications are needed to determine the actual environmental consequences of replacing Nafion® in PEMFCs
Comparative analysis of local angular rotation between the Ring Laser Gyroscope GINGERINO and GNSS stations
The study of local deformations is a hot topic in geodesy. Local rotations of
the crust around the vertical axis can be caused by deformations. In the Gran
Sasso area the ring laser prototype GINGERINO and the GNSS array are operative.
One year of data of GINGERINO is compared with the ones from the GNSS stations,
homogeneously selected around the position of GINGERINO, aiming at looking for
rotational signals with period of days common to both systems. At that purpose
the rotational component of the area circumscribed by the GNSS stations has
been evaluated and compared with the GINGERINO data. The coherences between the
signals show structures that even exceed 60 coherence over the 6-60 days
period; to validate this unprecedented analysis two different methods have been
used to evaluate the local rotation using the GNSS stations. The analysis
reveals that the shared rotational signal's amplitude in both instruments is
approximately , an order of magnitude lower than the amplitudes
of the signals examined using the coherence method. The ring laser array GINGER
is at present under construction, and the confrontation of the ring laser data
with GNSS antennas provides evidence of the fruibility and validity of the ring
laser data for very low frequency investigation
Optical response of a misaligned and suspended Fabry-Perot cavity
The response to a probe laser beam of a suspended, misaligned and detuned
optical cavity is examined. A five degree of freedom model of the fluctuations
of the longitudinal and transverse mirror coordinates is presented. Classical
and quantum mechanical effects of radiation pressure are studied with the help
of the optical stiffness coefficients and the signals provided by an FM
sideband technique and a quadrant detector, for generic values of the product
of the fluctuation frequency times the cavity round trip. A
simplified version is presented for the case of small misalignments. Mechanical
stability, mirror position entanglement and ponderomotive squeezing are
accommodated in this model. Numerical plots refer to cavities under test at the
so-called Pisa LF facility.Comment: 14 pages (4 figures) submitted to Phys. Rev.
GINGER: A feasibility study
GINGER (Gyroscopes IN General Relativity) is a proposal for an Earth-based experiment to measure the Lense-Thirring (LT) and de Sitter effects. GINGER is based on ring lasers, which are the most sensitive inertial sensors to measure the rotation rate of the Earth. We show that two ring lasers, one at maximum signal and the other horizontal, would be the simplest configuration able to retrieve the GR effects. Here, we discuss this configuration in detail showing that it would have the capability to test LT effect at 1%, provided the accuracy of the scale factor of the instrument at the level of 1 part in 1012 is reached. In principle, one single ring laser could do the test, but the combination of the two ring lasers gives the necessary redundancy and the possibility to verify that the systematics of the lasers are sufficiently small. The discussion can be generalised to seismology and geodesy and it is possible to say that signals 10-12 orders of magnitude below the Earth rotation rate can be studied; the proposed array can be seen as the basic element of multi-axial systems, and the generalisation to three dimensions is feasible adding one or two devices and monitoring the relative angles between different ring lasers. This simple array can be used to measure with very high precision the amplitude of angular rotation rate (the length of the day, LOD), its short term variations, and the angle between the angular rotation vector and the horizontal ring laser. Finally this experiment could be useful to probe gravity at fundamental level giving indications on violations of Einstein Equivalence Principle and Lorenz Invariance and possible chiral effects in the gravitational field
53BP1 supports immunoglobulin class switch recombination independently of its DNA double-strand break end protection function
Class switch recombination (CSR) is a DNA recombination reaction that diversifies the effector functions of antibodies. CSR occurs via the formation and non-homologous end joining (NHEJ) repair of programmed DNA double-strand breaks (DSBs) at the immunoglobulin heavy chain locus. The DNA repair factors 53BP1 and Rif1 promote NHEJ and CSR by protecting DSBs against resection. However, to what extent repression of DNA end resection contributes to CSR is unknown. Here, we show that B lymphocytes devoid of 53BP1-Rif1-dependent DSB end protection activity undergo robust CSR. Inactivation of specific sets of phospho-sites within 53BP1 N-terminal SQ/TQ motifs abrogates Rif1 recruitment and inhibition of resection but only mildly reduces CSR. Furthermore, mutations within 53BP1 oligomerization domain abolish CSR without substantially affecting DNA end processing. Thus, inhibition of DNA end resection does not correlate with CSR efficiency, indicating that regulation of DSB processing is not a key determinant step in CSR
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