Surgical Strategy in Midline Tumours of the Anterior Cranial Fossa

Midline tumors of the anterior cranial fossa (ACF) are mostly represented by olfactory groove menigiomas (OGM). There are many different approaches to this complex anatomical area but only a few that allow from the beginning dural implant removal: purely endoscopic transnasal (EA), transcranial/transfrontal sinus (TFA), and combined EA-TFA (CA) approach. Despite the improvement of EA, the optimal treatment strategy for the surgical treatment of OGM is still a matter of debate. The most advocate advantages of the EA are the absence of cerebral retraction and the possibility to resect the dural implant of the tumor, thus reducing its vascularization. On the other hand, it presents several limits: an important sinonasal morbidity, the loss of olfaction as default, increased risk of postoperative CSF leakage (5-10% in referral centers), especially in anteriorly located tumors. Moreover, the EA is contraindicated in case of lateral (above the orbital floor) or anterior extension (posterior wall of frontal sinus), cerebral parenchima involvment, or in case of major nerves or artery encasement. Consequently, only little tumors extended to the tuberculum sellae or planum sphenoidalis could be safely resected through a purely EA. The TFA is performed by a bicoronal incision, creating a craniotomy on the anterior wall of the frontal sinus and drilling the posterior wall of the frontal sinus. It gives direct access to the dural attachment of the tumor and avoids any cerebral retraction. In case of bulky or far posterior tumors, the interhemispheric route is usually very effective. The TFA permits to remove OGM of any dimension, to deal with nerves of vessel encasement, and to respect meningohypophyseal arteries. The incidence of postoperative CSF leakage is minimal since the closure with the galea is of the utmost effectiveness (0% in our experience). In case of sinonasal involvement, a CA is usually preferred

Surgical Strategy in Midline Tumours of the Anterior Cranial Fossa

Midline tumors of the anterior cranial fossa (ACF) are mostly represented by olfactory groove menigiomas (OGM). There are many different approaches to this complex anatomical area but only a few that allow from the beginning dural implant removal: purely endoscopic transnasal (EA), transcranial/transfrontal sinus (TFA), and combined EA-TFA (CA) approach. Despite the improvement of EA, the optimal treatment strategy for the surgical treatment of OGM is still a matter of debate. The most advocate advantages of the EA are the absence of cerebral retraction and the possibility to resect the dural implant of the tumor, thus reducing its vascularization. On the other hand, it presents several limits: an important sinonasal morbidity, the loss of olfaction as default, increased risk of postoperative CSF leakage (5-10% in referral centers), especially in anteriorly located tumors. Moreover, the EA is contraindicated in case of lateral (above the orbital floor) or anterior extension (posterior wall of frontal sinus), cerebral parenchima involvment, or in case of major nerves or artery encasement. Consequently, only little tumors extended to the tuberculum sellae or planum sphenoidalis could be safely resected through a purely EA. The TFA is performed by a bicoronal incision, creating a craniotomy on the anterior wall of the frontal sinus and drilling the posterior wall of the frontal sinus. It gives direct access to the dural attachment of the tumor and avoids any cerebral retraction. In case of bulky or far posterior tumors, the interhemispheric route is usually very effective. The TFA permits to remove OGM of any dimension, to deal with nerves of vessel encasement, and to respect meningohypophyseal arteries. The incidence of postoperative CSF leakage is minimal since the closure with the galea is of the utmost effectiveness (0% in our experience). In case of sinonasal involvement, a CA is usually preferred

Influences of urban fabric on pyroclastic density currents at Pompeii (Italy): 1. Flow direction and deposition

To assess ways in which the products of explosive eruptions interact with human settlements, we performed volcanological and rock magnetic analyses on the deposits of the A.D. 79 eruption at the Pompeii excavations (Italy). During this eruption the Roman town of Pompeii was covered by 2.5 m of fallout pumice and then partially destroyed by pyroclastic density currents (PDCs). Anisotropy of magnetic susceptibility measurements performed on the fine matrix of the deposits allowed the quantification of the variations in flow direction and emplacement mechanisms of the parental PDCs that entered the town. These results, integrated with volcanological field investigations, revealed that the presence of buildings, still protruding through the fallout deposits, strongly affected the distribution and accumulation of the erupted products. All of the PDCs that entered the town, even the most dilute ones, were density stratified currents in which interaction with the urban fabric occurred in the lower part of the current. The degree of interaction varied mainly as a function of obstacle height and density stratification within the current. For examples, the lower part of the EU4pf current left deposits up to 3 m thick and was able to interact with 2- to 4-m-high obstacles. However, a decrease in thickness and grain size of the deposits across the town indicates that even though the upper portion of the current was able to decouple from the lower portion, enabling it to flow over the town, it was not able to fully restore the sediment supply to the lower portion in order to maintain the deposition observed upon entry into the town.PublishedB052134.3. TTC - Scenari di pericolosità vulcanica3.6. Fisica del vulcanismoJCR Journalreserve

An Analytical Approach for the Design of Class-E Resonant DC-DC Converters

We present a new approach to design resonant dc-dc converters, that allows us to achieve both a more accurate implementation and a simpler architecture, by reducing the number of required passive components. The approach is applied to a class-E topology, and it is based on the analytic solution of the system of differential equations regulating the converter evolution. Our technique is also capable of taking into account the most important circuit nonidealities. This represents an important breakthrough with respect to the state of the art, where class-E circuit analysis is based on strong simplifying assumptions, and the final circuit design is achieved by means of numerical simulations after many time-consuming parametric sweeps. The developed methodology is dimensionless, and the achieved design curves can be denormalized to easily get the desired circuit design. Measurements on two different prototypes confirm an extremely high adherence to the developed mathematical approach.We present a new approach to design resonant dc-dc converters, that allows us to achieve both a more accurate implementation and a simpler architecture, by reducing the number of required passive components. The approach is applied to a class-E topology, and it is based on the analytic solution of the system of differential equations regulating the converter evolution. Our technique is also capable of taking into account the most important circuit nonidealities. This represents an important breakthrough with respect to the state of the art, where class-E circuit analysis is based on strong simplifying assumptions, and the final circuit design is achieved by means of numerical simulations after many time-consuming parametric sweeps. The developed methodology is dimensionless, and the achieved design curves can be denormalized to easily get the desired circuit design. Measurements on two different prototypes confirm an extremely high adherence to the developed mathematical approach

Phase-Change Memory in Neural Network Layers with Measurements-based Device Models

The search for energy efficient circuital implementations of neural networks has led to the exploration of phase-change memory (PCM) devices as their synaptic element, with the advantage of compact size and compatibility with CMOS fabrication technologies. In this work, we describe a methodology that, starting from measurements performed on a set of real PCM devices, enables the training of a neural network. The core of the procedure is the creation of a computational model, sufficiently general to include the effect of unwanted non-idealities, such as the voltage dependence of the conductances and the presence of surrounding circuitry. Results show that, depending on the task at hand, a different level of accuracy is required in the PCM model applied at train-time to match the performance of a traditional, reference network. Moreover, the trained networks are robust to the perturbation of the weight values, up to 10% standard deviation, with performance losses within 3.5% for the accuracy in the classification task being considered and an increase of the regression RMS error by 0.014 in a second task. The considered perturbation is compatible with the performance of state-of-the-art PCM programming techniques

XIPE: the X-ray Imaging Polarimetry Explorer

X-ray polarimetry, sometimes alone, and sometimes coupled to spectral and temporal variability measurements and to imaging, allows a wealth of physical phenomena in astrophysics to be studied. X-ray polarimetry investigates the acceleration process, for example, including those typical of magnetic reconnection in solar flares, but also emission in the strong magnetic fields of neutron stars and white dwarfs. It detects scattering in asymmetric structures such as accretion disks and columns, and in the so-called molecular torus and ionization cones. In addition, it allows fundamental physics in regimes of gravity and of magnetic field intensity not accessible to experiments on the Earth to be probed. Finally, models that describe fundamental interactions (e.g. quantum gravity and the extension of the Standard Model) can be tested. We describe in this paper the X-ray Imaging Polarimetry Explorer (XIPE), proposed in June 2012 to the first ESA call for a small mission with a launch in 2017 but not selected. XIPE is composed of two out of the three existing JET-X telescopes with two Gas Pixel Detectors (GPD) filled with a He-DME mixture at their focus and two additional GPDs filled with pressurized Ar-DME facing the sun. The Minimum Detectable Polarization is 14 % at 1 mCrab in 10E5 s (2-10 keV) and 0.6 % for an X10 class flare. The Half Energy Width, measured at PANTER X-ray test facility (MPE, Germany) with JET-X optics is 24 arcsec. XIPE takes advantage of a low-earth equatorial orbit with Malindi as down-link station and of a Mission Operation Center (MOC) at INPE (Brazil).Comment: 49 pages, 14 figures, 6 tables. Paper published in Experimental Astronomy http://link.springer.com/journal/1068

Lunar Gravitational-Wave Antenna

Monitoring of vibrational eigenmodes of an elastic body excited by gravitational waves was one of the first concepts proposed for the detection of gravitational waves. At laboratory scale, these experiments became known as resonant-bar detectors first developed by Joseph Weber in the 1960s. Due to the dimensions of these bars, the targeted signal frequencies were in the kHz range. Weber also pointed out that monitoring of vibrations of Earth or Moon could reveal gravitational waves in the mHz band. His Lunar Surface Gravimeter experiment deployed on the Moon by the Apollo 17 crew had a technical failure rendering the data useless. In this article, we revisit the idea and propose a Lunar Gravitational-Wave Antenna (LGWA). We find that LGWA could become an important partner observatory for joint observations with the space-borne, laser-interferometric detector LISA, and at the same time contribute an independent science case due to LGWA's unique features. Technical challenges need to be overcome for the deployment of the experiment, and development of inertial vibration sensor technology lays out a future path for this exciting detector concept.Comment: 29 pages, 17 figure

MAORY: adaptive optics module for the E-ELT

MAORY is one of the four instruments for the E-ELT approved for construction. It is an adaptive optics module offering two compensation modes: multi-conjugate and single-conjugate adaptive optics. The project has recently entered its phase B. A system-level overview of the current status of the project is given in this paper

The MAORY first-light adaptive optics module for E-ELT

The MAORY adaptive optics module is part of the first light instrumentation suite for the E-ELT. The MAORY project phase B is going to start soon. This paper contains a system-level overview of the current instrument design