10,075 research outputs found
A kg-mass prototype demonstrator for DUAL gravitational wave detector: opto-mechanical excitation and cooling
The next generation of gravitational wave (gw) detectors is expected to fully
enter into the quantum regime of force and displacement detection. With this
aim, it is important to scale up the experiments on opto-mechanical effects
from the microscopic regime to large mass systems and test the schemes that
should be applied to reach the quantum regime of detection. In this work we
present the experimental characterization of a prototype of massive gw
detector, composed of two oscillators with a mass of the order of the kg, whose
distance is read by a high finesse optical cavity. The mechanical response
function is measured by exciting the oscillators though modulated radiation
pressure. We demonstrate two effects crucial for the next generation of
massive, cryogenic gw detectors (DUAL detectors): a) the reduction of the
contribution of 'local' susceptibility thanks to an average over a large
interrogation area. Such effect is measured on the photo-thermal response
thanks to the first implementation of a folded-Fabry-Perot cavity; b) the
'back-action reduction' due to negative interference between acoustic modes.
Moreover, we obtain the active cooling of an oscillation mode through radiation
pressure, on the described mechanical device which is several orders of
magnitude heavier than previously demonstrated radiation-pressure cooled
systems
Maximum scattered linear sets and MRD-codes
The rank of a scattered -linear set of , rn even, is at most rn / 2 as it was proved by Blokhuis and Lavrauw. Existence results and explicit constructions were given for infinitely many values of r, n, q (rn even) for scattered -linear sets of rank rn / 2. In this paper, we prove that the bound rn / 2 is sharp also in the remaining open cases. Recently Sheekey proved that scattered -linear sets of of maximum rank n yield -linear MRD-codes with dimension 2n and minimum distance . We generalize this result and show that scattered -linear sets of of maximum rank rn / 2 yield -linear MRD-codes with dimension rn and minimum distance n - 1
Atrioventricular canal defect and genetic syndromes: the unifying role of sonic hedgehog
The atrioventricular canal defect (AVCD) is a congenital heart defect (CHD) frequently associated with extracardiac anomalies (75%). Previous observations from a personal series of patients with AVCD and "polydactyly syndromes" showed that the distinct morphology and combination of AVCD features in some of these syndromes is reminiscent of the cardiac phenotype found in heterotaxy, a malformation complex previously associated with functional cilia abnormalities and aberrant Hedgehog (Hh) signaling. Hh signaling coordinates multiple aspects of left-right lateralization and cardiovascular growth. Being active at the venous pole the secondary heart field (SHF) is essential for normal development of dorsal mesenchymal protrusion and AVCD formation and septation. Experimental data show that perturbations of different components of the Hh pathway can lead to developmental errors presenting with partially overlapping manifestations and AVCD as a common denominator. We review the potential role of Hh signaling in the pathogenesis of AVCD in different genetic disorders. AVCD can be viewed as part of a "developmental field," according to the concept that malformations can be due to defects in signal transduction cascades or pathways, as morphogenetic units which may be altered by Mendelian mutations, aneuploidies, and environmental causes
Control of Recoil Losses in Nanomechanical SiN Membrane Resonators
In the context of a recoil damping analysis, we have designed and produced a
membrane resonator equipped with a specific on-chip structure working as a
"loss shield" for a circular membrane. In this device the vibrations of the
membrane, with a quality factor of , reach the limit set by the intrinsic
dissipation in silicon nitride, for all the modes and regardless of the modal
shape, also at low frequency. Guided by our theoretical model of the loss
shield, we describe the design rationale of the device, which can be used as
effective replacement of commercial membrane resonators in advanced
optomechanical setups, also at cryogenic temperatures
Quantum skyrmions and the destruction of long-range antiferromagnetic order in the high-Tc superconductors La(2-x)Sr(x)CuO(4) and YBa(2)Cu(3)O(6+x)
We study the destruction of the antiferromagnetic order in the high-Tc
superconductors La(2-x)Sr(x)CuO(4) and YBa(2)Cu(3)O(6+x) in the framework of
the CP1-nonlinear sigma model formulation of the 2D quantum Heisenberg
antiferromagnet. The dopants are introduced as independent fermions with
appropriate dispersion relations determined by the shape of the Fermi surface.
The energy of skyrmion topological defects, which are shown to be introduced by
doping, is used as an order parameter for antiferromagnetic order. We obtain
analytic expressions for this as a function of doping which allow us to plot
the curves T_N(x_c)\times x_c and M(x)\times x, for both YBCO and LSCO, in good
quantitative agreement with the experimental data.Comment: 4 pages, revtex, 5 embeeded figure
Calibrated quantum thermometry in cavity optomechanics
Cavity optomechanics has achieved the major breakthrough of the preparation
and observation of macroscopic mechanical oscillators in peculiarly quantum
states. The development of reliable indicators of the oscillator properties in
these conditions is important also for applications to quantum technologies. We
compare two procedures to infer the oscillator occupation number, minimizing
the necessity of system calibrations. The former starts from homodyne spectra,
the latter is based on the measurement of the motional sidebands asymmetry in
heterodyne spectra. Moreover, we describe and discuss a method to control the
cavity detuning, that is a crucial parameter for the accuracy of the latter,
intrinsically superior procedure
Dataset of Electoral Volatility in the European Parliament elections since 1979
This dataset provides data on electoral volatility and its internal components in the elections for the European Parliament (EP) in all European Union (EU) countries since 1979 or the date of their accession to the Union. It also provides data about electoral volatility for both the class bloc and the demarcation bloc. This dataset will be regularly updated so as to include the next rounds of the European Parliament elections.
How to cite this dataset?
Emanuele, V., Angelucci, D., Marino, B., Puleo, L., and Vegetti, F. (2019), Dataset of Electoral Volatility in the European Parliament elections since 1979, Rome: Italian Center for Electoral Studies, http://dx.doi.org/10.7802/1905
An empirical analysis of smart contracts: platforms, applications, and design patterns
Smart contracts are computer programs that can be consistently executed by a
network of mutually distrusting nodes, without the arbitration of a trusted
authority. Because of their resilience to tampering, smart contracts are
appealing in many scenarios, especially in those which require transfers of
money to respect certain agreed rules (like in financial services and in
games). Over the last few years many platforms for smart contracts have been
proposed, and some of them have been actually implemented and used. We study
how the notion of smart contract is interpreted in some of these platforms.
Focussing on the two most widespread ones, Bitcoin and Ethereum, we quantify
the usage of smart contracts in relation to their application domain. We also
analyse the most common programming patterns in Ethereum, where the source code
of smart contracts is available.Comment: WTSC 201
Charge pairing, superconducting transition and supersymmetry in high-temperature cuprate superconductors
We propose a model for high-T superconductors, valid for
, that includes both the spin fluctuations of the
Cu magnetic ions and of the O doped holes. Spin-charge separation
is taken into account with the charge of the doped holes being associated to
quantum skyrmion excitations (holons) of the Cu spin background. The
holon effective interaction potential is evaluated as a function of doping,
indicating that Cooper pair formation is determined by the competition between
the spin fluctuations of the Cu background and of spins of the O
doped holes (spinons). The superconducting transition occurs when the spinon
fluctuations dominate, thereby reversing the sign of the interaction. At this
point (), the theory is supersymmetric at short distances
and, as a consequence, the leading order results are not modified by radiative
corrections. The critical doping parameter for the onset of superconductivity
at T=0 is obtained and found to be a universal constant determined by the shape
of the Fermi surface. Our theoretical values for are in good
agreement with the experiment for both LSCO and YBCO.Comment: RevTex, 4 pages, no figure
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