Stochastic background of gravitational waves generated by a cosmological population of young, rapidly rotating neutron stars

We estimate the spectral properties of the stochastic background of gravitational radiation emitted by a cosmological population of hot, young, rapidly rotating neutron stars. Their formation rate as a function of redshift is deduced from an observation-based determination of the star formation history in the Universe, and the gravitational energy is assumed to be radiated during the spin-down phase associated to the newly discovered r-mode instability. We calculate the overall signal produced by the ensemble of such neutron stars, assuming various cosmological backgrounds. We find that the spectral strain amplitude has a maximum $\approx (2-4)\times 10^{-26} {Hz}^{-1/2}$, at frequencies $\approx (30-60)$ Hz, while the corresponding closure density, $h^2 \Omega_{GW}$, has a maximum amplitude plateau of $\approx (2.2-3.3) \times 10^{-8}$ in the frequency range $(500-1700)$ Hz. We compare our results with a preliminary analysis done by Owen et al. (1998), and discuss the detectability of this background.Comment: 8 pages, 9 figures, accepted for publication in MNRA

Gravitational Wave Background from a Cosmological Population of Core-Collapse Supernovae

We analyse the stochastic background of gravitational radiation emitted by a cosmological population of core-collapse supernovae. The supernova rate as a function of redshift is deduced from an observation-based determination of the star formation rate density evolution. We then restrict our analysis to the range of progenitor masses leading to black hole collapse. In this case, the main features of the gravitational-wave emission spectra have been shown to be, to some extent, independent of the initial conditions and of the equation of state of the collapsing star, and to depend only on the black hole mass and angular momentum. We calculate the overall signal produced by the ensemble of black-hole collapses throughout the Universe, assuming a flat cosmology with vanishing cosmological constant. Within a wide range of parameter values, we find that the spectral strain amplitude has a maximum at a few hundred Hz with an amplitude between $10^{-28}$ and $10^{-27} Hz^{-1/2}$; the corresponding closure density, $\Omega_{GW}$, has a maximum amplitude ranging between $10^{-11}$ and $10^{-10}$ in the frequency interval $\sim 1.5-2.5$ kHz. Contrary to previous claims, our observation-based determination leads to a duty cycle of order 0.01, making our stochastic backgound a non-continuous one. Although the amplitude of our background is comparable to the sensitivity that can be reached by a pair of advanced LIGO detectors, the characteristic shot-noise structure of the predicted signal might be in principle exploited to design specific detection strategies.Comment: 12 pages, LaTeX (uses mn.sty), 13 figures, 2 tables, accepted for publication in MNRA

Stochastic Backgrounds of Gravitational Waves from Cosmological Populations of Astrophysical Sources

Astrophysical sources of gravitational radiation are likely to have been formed since the beginning of star formation. Realistic source rates of formation throughout the Universe have been estimated from an observation-based determination of the star formation rate density evolution. Both the radiation emitted during the collapse to black holes and the spin-down radiation, induced by the r-mode instability, emitted by hot, young rapidly rotating neutron stars have been considered. We have investigated the overall signal produced by the ensemble of sources exploring the parameter space and discussing its possible detectability.Comment: 9 pages, 7 figures, to appear in the proceedings of the 19th Texas Symposium on Relativistic Astrophysics and Cosmology, Paris, December 14-18, 199

Il bimillenario dell’acquedotto augusteo di Serino

Una galleria romana poco nota, posta in località Scalandrone (comune di Bacoli – NA), contiene un’iscrizione parietale che celebra l’apertura di un cunicolo di collegamento fra la galleria stessa ed un ramo dell’antico acquedotto augusteo di Serino. L’iscrizione riporta una data corrispondente al 30 dicembre 10 d.C. Si tratta del più antico riferimento ante quem relativo all’acquedotto augusteo. Grazie ad una collaborazione fra A.R.I.N. S.p.A (Azienda Risorse Idriche Napoli) e la Soprintendenza Speciale ai Beni Archeologici di Napoli e Pompei, è stato ideato e realizzato un progetto comprendente l’esecuzione di un modello digitale della galleria e dell’iscrizione con tecnologie laser-scan ed a luce strutturata; dal modello sono state ricavate due copie su pietra dell’iscrizione, che sono state esposte nel Museo Archeologico dei Campi Flegrei e nella sede di Napoli dell’A.R.I.N. Infine, il 30 dicembre 2010 è stato organizzato un evento-convegno di celebrazione del bimillenario, culminato nel taglio di una spettacolare torta-monumento. Gli autori hanno partecipato all’ideazione ed alla realizzazione del progetto in veste di consulenti operativi e scientifici.A little known roman tunnel is placed in the municipality of Bacoli (Naples, Italy), in an area historically called Scalandrone. Bacoli is part of the renowned Phlegraean Field, visited by thousands of foreigners as part of a Grand Tour in the XVI-XIX centuries. However, the Scalandrone tunnel was not mentioned in local guides and foreign reports. The tunnel contains an inscription which celebrates the opening of an Haustus (passage intended as a water catchment) connected to the Augustean aqueduct. The date of the event is reported as December 30th 10 A.D. So, on last December we celebrated the bimillennial birthday of the Haustus. Thanks to the cooperation between A.R.I.N. (Naples water resources company) and the Special Archaeological Superintendency of Naples and Pompei, an event was planned in order to celebrate the tunnel and the inscription at the same time. The on-field work was performed by the ASAstudio company, with laser-scan and structured light techniques. A digital model of the inscription was produced, together with a 3D model of the main tunnel. Finally, on December 30th 2010 the birthday celebration summed up with a monumental cake inspired to the renowned Piscina mirabilis. The authors acted as designers and promoters of the project; in the on-field work the authors acted as operative and scientific consultants

Giovanni Michelucci: i Nuovi Istituti di Matematica e Geometria

Il volume descrive il progetto più interessante realizzato a Bologna dall'architetto pistoiese Giovanni Michelucci (1891-1990) negli anni 1955-1965: i Nuovi Istituti di Matematica e Geometria, attuale sede del Dipartimento di Matematica in piazza di Porta San Donato. Raccoglie gli studi degli autori svolti per le rispettive Tesi di Dottorato

Constraining modified theories of gravity with gravitational wave stochastic background

The direct discovery of gravitational waves has finally opened a new observational window on our Universe, suggesting that the population of coalescing binary black holes is larger than previously expected. These sources produce an unresolved background of gravitational waves, potentially observables by ground-based interferometers. In this paper we investigate how modified theories of gravity, modeled using the ppE formalism, affect the expected signal, and analyze the detectability of the resulting stochastic background by current and future ground-based interferometers. We find the constraints that AdLIGO would be able to set on modified theories, showing that they may significantly improve the current bounds obtained from astrophysical observations of binary pulsars.Comment: Results updated to match the version accepted on Phys. Rev. Let

Low-fidelity simulators for the training of medical students in basic endovascular skills

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Transport Properties of Natural and Artificial Smart Fabrics Impregnated by Graphite Nanomaterial Stacks

none4noIn this work, we studied the transport properties (thermal and electrical conductivity) of smart fabric materials treated with graphite nanomaterial stacks–acetone suspensions. An innovative and easy method to produce graphite nanomaterial stacks–acetone-based formulations, starting from a low-cost expandable graphite, is proposed. An original, economical, fast, and easy method to increase the thermal and electrical conductivity of textile materials was also employed for the first time. The proposed method allows the impregnation of smart fabric materials, avoiding precoating of the fibers, thus reducing costs and processing time, while obtaining a great increase in the transport properties. Two kinds of textiles, cotton and Lycra®, were selected as they represent the most used natural and artificial fabrics, respectively. The impact of the dimensions of the produced graphite nanomaterial stacks–acetone-based suspensions on both the uniformity of the treatment and the transport properties of the selected textile materials was accurately evaluated using several experimental techniques. An empirical relationship between the two transport properties was also successfully identified. Finally, several theoretical models were applied to predict the transport properties of the developed smart fabric materials, evidencing a good agreement with the experimental data.openCarola Esposito Corcione; Francesca Ferrari; Raffaella Striani; Antonio GrecoESPOSITO CORCIONE, Carola; Ferrari, Francesca; Striani, Raffaella; Greco, ANTONIO STEFAN

Laparoscopic treatment of splenic artery aneurysms

OBJECTIVES: The purpose of this study was to report a series of 16 consecutive patients who underwent laparoscopic treatment of splenic artery aneurysms. METHODS: Over a period of 8 years, patients were selected for the laparoscopic option by a team of specialists that included the vascular surgeon, the interventional radiologist, and the laparoscopic surgeon. The mean size of the aneurysm was 32 mm and most was located at the splenic hilum. They were twice as common in females as in males. Ultrasonography with color Doppler function was used to define intraoperative strategy. RESULTS: The laparoscopic treatment entailed excision of the aneurysm or its exclusion, usually reserved for distally located lesions. In one patient, laparoscopic resection and robotic anastomosis of the splenic artery was performed to re-establish flow to the spleen. In two patients, the intraoperative decision was added to combine a laparoscopic splenectomy due to insufficient residual arterial flow to the spleen. There was no conversion, or need for re-operation or related mortality. Analysis of intraoperative arterial flow data avoided unnecessary splenectomy following noncritical reduction of flow to the spleen. CONCLUSIONS: The use of intraoperative color Doppler ultrasonography is essential in deciding the appropriate procedure and whether the spleen should be removed or saved. Early control of the splenic artery proximal to the aneurysm can limit the risk of conversion due to intraoperative bleeding. Distally located aneurysms are more difficult to manage and entail a higher risk of associated splenectomy. The laparoscopic option offers some advantages over the endovascular treatment in selected patients. A multidisciplinary approach is the key to a successful treatment of this uncommon disease

Stochastic background of gravitational waves emitted by magnetars

Two classes of high energy sources in our galaxy are believed to host magnetars, neutron stars whose emission results from the dissipation of their magnetic field. The extremely high magnetic field of magnetars distorts their shape, and causes the emission of a conspicuous gravitational waves signal if rotation is fast and takes place around a different axis than the symmetry axis of the magnetic distortion. Based on a numerical model of the cosmic star formation history, we derive the cosmological background of gravitational waves produced by magnetars, when they are very young and fast spinning. We adopt different models for the configuration and strength of the internal magnetic field (which determines the distortion) as well as different values of the external dipole field strength (which governs the spin evolution of magnetars over a wide range of parameters). We find that the expected gravitational wave background differs considerably from one model to another. The strongest signals are generated for magnetars with very intense toroidal internal fields ($\sim 10^{16}$ G range) and external dipole fields of $\sim 10^{14}$, as envisaged in models aimed at explaining the properties of the Dec 2004 giant flare from SGR 1806-20. Such signals should be easily detectable with third generation ground based interferometers such as the Einstein Telescope.Comment: 9 pages, 5 figures, accepted for publication in MNRA