CAD-CAE methods to support restoration and museum exhibition of bronze statues: the “Principe Ellenistico”

Ancient bronze statues mainly require material integrity assessment and restoration. Restoration may include also the update of the museum exhibition, defining new structural frames and fragment re-composition to preserve the statue and improve the interpretation of the original aspect. This paper proves how engineering methods (such as Finite Element Analysis, Computer Aided Design modelling, Reverse Engineering) may assist cultural heritage experts and restorers in these tasks. It presents the activities made together with the Museo Nazionale Romano and the Istituto Superiore per la Conservazione e il Restauro, on the so-called “Principe Ellenistico” (Hellenistic Prince). This bronze was found in pieces (body, left arm and right leg), at the end of 19th century during an excavation made in Rome. No visual or reference sources can say its origin and its final posture was defined by restorers at the end of the 19th century according to their hypothesis and studies. In the 20th century, a further restoration was made on the critical areas of the surface, together with some structural improvement of the inner frame. Nowadays, after a review of its position inside the Museum, new experimental and numerical analyses have been carried out to better understand surface weakness and correct left arm positionin

Quantized Transport in Two-Dimensional Spin-Ordered Structures

We study in detail the transport properties of a model of conducting electrons in the presence of double-exchange between localized spins arranged on a 2D Kagome lattice, as introduced by Ohgushi, Murakami, and Nagaosa (2000). The relationship between the canting angle of the spin texture $\theta$ and the Berry phase field flux per triangular plaquette $\phi$ is derived explicitly and we emphasize the similarities between this model and Haldane's honeycomb lattice version of the quantum Hall effect (Haldane, 1988). The quantization of the transverse (Hall) conductivity $\sigma_{xy}$ is derived explicitly from the Kubo formula and a direct calculation of the longitudinal conductivity $\sigma_{xx}$ shows the existence of a metal-insulator transition as a function of the canting angle $\theta$ (or flux density $\phi$). This transition might be linked to that observable in the manganite compounds or in the pyrochlore ones, as the spin ordering changes from ferromagnetic to canted.Comment: 17 pages, 12 figure

Further Constraints on Thermal Quiescent X-ray Emission from SAX J1808.4-3658

We observed SAX J1808.4-3658 (1808), the first accreting millisecond pulsar, in deep quiescence with XMM-Newton and (near-simultaneously) Gemini-South. The X-ray spectrum of 1808 is similar to that observed in quiescence in 2001 and 2006, describable by an absorbed power-law with photon index 1.74+-0.11 and unabsorbed X-ray luminosity L_X=7.9+-0.7*10^{31} ergs/s, for N_H=1.3*10^{21} cm^{-2}. Fitting all the quiescent XMM-Newton X-ray spectra with a power-law, we constrain any thermally emitting neutron star with a hydrogen atmosphere to have a temperature less than 30 eV and L_{NS}(0.01-10 keV)<6.2*10^{30} ergs/s. A thermal plasma model also gives an acceptable fit to the continuum. Adding a neutron star component to the plasma model produces less stringent constraints on the neutron star; a temperature of 36^{+4}_{-8} eV and L_{NS}(0.01-10 keV)=1.3^{+0.6}_{-0.8}*10^{31} ergs/s. In the framework of the current theory of neutron star heating and cooling, the constraints on the thermal luminosity of 1808 and 1H 1905+000 require strongly enhanced cooling in the cores of these neutron stars. We compile data from the literature on the mass transfer rates and quiescent thermal flux of the largest possible sample of transient neutron star LMXBs. We identify a thermal component in the quiescent spectrum of the accreting millisecond pulsar IGR J00291+5934, which is consistent with the standard cooling model. The contrast between the cooling rates of IGR J00291+5934 and 1808 suggests that 1808 may have a significantly larger mass. This can be interpreted as arising from differences in the binary evolution history or initial neutron star mass in these otherwise similar systems.Comment: ApJ in press, 7 pages, 2 color figure

Bulk Lorentz factors of Gamma-Ray Bursts

Knowledge of the bulk Lorentz factor $\Gamma_{0}$ of GRBs allows us to compute their comoving frame properties shedding light on their physics. Upon collisions with the circumburst matter, the fireball of a GRB starts to decelerate, producing a peak or a break (depending on the circumburst density profile) in the light curve of the afterglow. Considering all bursts with known redshift and with an early coverage of their emission, we find 67 GRBs with a peak in their optical or GeV light curves at a time $t_{\rm p}$. For another 106 GRBs we set an upper limit $t_{\rm p}^{\rm UL}$. We show that $t_{\rm p}$ is due to the dynamics of the fireball deceleration and not to the passage of a characteristic frequency of the synchrotron spectrum across the optical band. Considering the $t_{\rm p}$ of 66 long GRBs and the 85 most constraining upper limits, using censored data analysis methods, we reconstruct the most likely distribution of $t_{\rm p}$. All $t_{\rm p}$ are larger than the time $t_{\rm p,g}$ when the prompt emission peaks, and are much larger than the time $t_{\rm ph}$ when the fireball becomes transparent. The reconstructed distribution of $\Gamma_0$ has median value $\sim$300 (150) for a uniform (wind) circumburst density profile. In the comoving frame, long GRBs have typical isotropic energy, luminosity, and peak energy $\langle E_{\rm iso}\rangle=3(8)\times 10^{50}$ erg, $\langle L_{\rm iso}\rangle=3(15) \times 10^{47}$ erg s$^{-1}$ , and $\langle E_{\rm peak}\rangle =1(2)$ keV in the homogeneous (wind) case. We confirm that the significant correlations between $\Gamma$ and the rest frame isotropic energy ($E_{\rm iso}$), luminosity ($L_{\rm iso}$) and peak energy ($E_{\rm peak}$) are not due to selection effects. Assuming a typical opening angle of 5 degrees, we derive the distribution of the jet baryon loading which is centered around a few $10^{-6} {\rm M_{\odot}}$.Comment: 19 pages, 11 figures, 6 tables. Accepted for publication on Astronomy & Astrophysic

An exploratory study toward the contribution of 3D surface scanning for association of an injury with its causing instrument.

3D surface scanning is a technique brought forward for wound documentation and analysis in order to identify injury-causing tools in legal medicine and forensic science. Although many case reports have been published, little is known about the methodology employed by the authors. The study reported here is exploratory in nature, and its main purpose was to get a first evaluation of the ability of an operator, by means of 3D surface scanning and following a simple methodology, to correctly exclude or associate an incriminated tool as the source of a mock wound. Based on these results, an assessment of the possibility to define a structured methodology that could be suitable for this use was proposed. Blunt tools were used to produce 'wounds' on watermelons. Both wounds and tools were scanned with a non-contact optical surface 3D digitising system. Analysis of the obtained 3D models of wounds and tools was undertaken separately. This analytical phase was followed by a qualitative and a quantitative comparison. Results showed that in more than half of the cases, we obtained a correct association but the prevalence of wrong association was still high due to mark deformation and other limitations. Even if the findings of this exploratory study cannot be generalised, they suggest that the simple and direct comparison process is not reliable enough for a systematic routine application. The article highlights the importance of an analysis phase preceding the comparison step. Limitations of the technique, ensuring needs and possible paths for improvement are also expounded

Three Additional Quiescent Low-Mass X-ray Binary Candidates in 47 Tucanae

We identify through their X-ray spectra one certain (W37) and two probable (W17 and X4) quiescent low-mass X-ray binaries (qLMXBs) containing neutron stars in a long Chandra X-ray exposure of the globular cluster 47 Tucanae, in addition to the two previously known qLMXBs. W37's spectrum is dominated by a blackbody-like component consistent with radiation from the hydrogen atmosphere of a 10 km neutron star. W37's lightcurve shows strong X-ray variability which we attribute to variations in its absorbing column depth, and eclipses with a probable 3.087 hour period. For most of our exposures, W37's blackbody-like emission (assumed to be from the neutron star surface) is almost completely obscured, yet some soft X-rays (of uncertain origin) remain. Two additional candidates, W17 and X4, present X-ray spectra dominated by a harder component, fit by a power-law of photon index ~1.6-3. An additional soft component is required for both W17 and X4, which can be fit with a 10 km hydrogen-atmosphere neutron star model. X4 shows significant variability, which may arise from either its power-law or hydrogen-atmosphere spectral component. Both W17 and X4 show rather low X-ray luminosities, Lx(0.5-10 keV)~5*10^{31} ergs/s. All three candidate qLMXBs would be difficult to identify in other globular clusters, suggesting an additional reservoir of fainter qLMXBs in globular clusters that may be of similar numbers as the group of previously identified objects. The number of millisecond pulsars inferred to exist in 47 Tuc is less than 10 times larger than the number of qLMXBs in 47 Tuc, indicating that for typical inferred lifetimes of 10 and 1 Gyr respectively, their birthrates are comparable.Comment: Accepted for publication in ApJ. 13 pages, 7 figures (2 color

Carbon based double layer capacitors with aprotic electrolyte solutions: the possible role of intercalation/insertion processes

The extraordinary stability and cycle life performance of today's electrochemical double-layer capacitors (EDLCs) are generally ascribed to the fact that charge storage in activated carbon (AC) is based on pure double-layer charging. In contrast, Faradaic charge-transfer reactions like those occurring in batteries are often connected with dimensional changes, which can affect the cycle life of these storage devices. Here we report the charge-induced height change of an AC electrode in an aprotic electrolyte solution, 1mol/l (C2H5)4NBF4 (TEABF4) in acetonitrile. The results are compared with those obtained for a graphite electrode in the same electrolyte. For both electrodes, we observe an expansion/contraction of several percent for a potential window of ±2V vs. the immersion potential (ip). For the EDLC electrode, significant expansion starts at about 1V remote from the ip and hence is well within the normal EDLC operation range. For the graphite electrode, the height changes are unambiguously caused by intercalation/deintercalation of both anions and cations. The close analogies between the graphite and the EDLC electrode suggest that ion intercalation or insertion processes might play a major role for charge storage, self discharge, cyclability, and the voltage limitation of EDLC

SIMBOL-X : a new generation hard X-ray telescope

SIMBOL-X is a hard X-ray mission, operating in the 0.5-70 keV range, which is proposed by a consortium of European laboratories for a launch around 2010. Relying on two spacecraft in a formation flying configuration, SIMBOL-X uses a 30 m focal length X-ray mirror to achieve an unprecedented angular resolution (30 arcsec HEW) and sensitivity (100 times better than INTEGRAL below 50 keV) in the hard X-ray range. SIMBOL-X will allow to elucidate fundamental questions in high energy astrophysics, such as the physics of accretion onto Black Holes, of acceleration in quasar jets and in supernovae remnants, or the nature of the hard X-ray diffuse emission. The scientific objectives and the baseline concepts of the mission and hardware design are presented.Comment: 12 pages, 16 fig., Proc. SPIE conf. 5168, San Diego, Aug. 200

Cohomological characterizations of projective spaces and hyperquadrics

We confirm Beauville's conjecture that claims that if the p-th exterior power of the tangent bundle of a smooth projective variety contains the p-th power of an ample line bundle, then the variety is either the projective space or the p-dimensional quadric hypersurface.Comment: Added Lemma 2.8 and slightly changed proof of Lemma 6.2 to make them apply for torsion-free sheaves and not only to vector bundle

Modelling the spectral response of the Swift-XRT CCD camera: Experience learnt from in-flight calibration

(Abbreviated) We show that the XRT spectral response calibration was complicated by various energy offsets in photon counting (PC) and windowed timing (WT) modes related to the way the CCD is operated in orbit (variation in temperature during observations, contamination by optical light from the sunlit Earth and increase in charge transfer inefficiency). We describe how these effects can be corrected for in the ground processing software. We show that the low-energy response, the redistribution in spectra of absorbed sources, and the modelling of the line profile have been significantly improved since launch by introducing empirical corrections in our code when it was not possible to use a physical description. We note that the increase in CTI became noticeable in June 2006 (i.e. 14 months after launch), but the evidence of a more serious degradation in spectroscopic performance (line broadening and change in the low-energy response) due to large charge traps (i.e. faults in the Si crystal) became more significant after March 2007. We describe efforts to handle such changes in the spectral response. Finally, we show that the commanded increase in the substrate voltage from 0 to 6V on 2007 August 30 reduced the dark current, enabling the collection of useful science data at higher CCD temperature (up to -50C). We also briefly describe the plan to recalibrate the XRT response files at this new voltage.Comment: 27 pages, 29 figures (many in colour), accepted for publication in A&