Comincio a cantare. Contributi allo studio degli Inni Omerici

Ce volume collectif édité par Riccardo Di Donato réunit six études sur les Hymnes homériques, écrites par des étudiants de Lettres classiques de l’Université de Pise, qui ont librement choisi le thème de leurs recherches. Résultat d’« une expérience didactique ordinaire », comme le note l’éditeur dans son introduction, les six études adoptent une méthode historique fondée sur des éléments à la fois de langue et de littérature pour formuler des hypothèses sur le contexte de composition et d’ex..

P4Testgen: An Extensible Test Oracle For P4

We present P4Testgen, a test oracle for the P4-16 language that supports automatic generation of packet tests for any P4-programmable device. Given a P4 program and sufficient time, P4Testgen generates tests that cover every reachable statement in the input program. Each generated test consists of an input packet, control-plane configuration, and output packet(s), and can be executed in software or on hardware. Unlike prior work, P4Testgen is open source and extensible, making it a general resource for the community. P4Testgen not only covers the full P4-16 language specification, it also supports modeling the semantics of an entire packet-processing pipeline, including target-specific behaviors-i.e., whole-program semantics. Handling aspects of packet processing that lie outside of the official specification is critical for supporting real-world targets (e.g., switches, NICs, end host stacks). In addition, P4Testgen uses taint tracking and concolic execution to model complex externs (e.g., checksums and hash functions) that have been omitted by other tools, and ensures the generated tests are correct and deterministic. We have instantiated P4Testgen to build test oracles for the V1model, eBPF, and the Tofino (TNA and T2NA) architectures; each of these extensions only required effort commensurate with the complexity of the target. We validated the tests generated by P4Testgen by running them across the entire P4C program test suite as well as the Tofino programs supplied with Intel's P4 Studio. In just a few months using the tool, we discovered and confirmed 25 bugs in the mature, production toolchains for BMv2 and Tofino, and are conducting ongoing investigations into further faults uncovered by P4Testgen

Further Insight into Mechanisms of Ventricular Tachycardia from the Clinical Electrophysiology Laboratory

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72003/1/j.1540-8167.1991.tb01319.x.pd

Direct cooling of the catheter tip increases safety for CMR-guided electrophysiological procedures

<p>Abstract</p> <p>Background</p> <p>One of the safety concerns when performing electrophysiological (EP) procedures under magnetic resonance (MR) guidance is the risk of passive tissue heating due to the EP catheter being exposed to the radiofrequency (RF) field of the RF transmitting body coil. Ablation procedures that use catheters with irrigated tips are well established therapeutic options for the treatment of cardiac arrhythmias and when used in a modified mode might offer an additional system for suppressing passive catheter heating.</p> <p>Methods</p> <p>A two-step approach was chosen. Firstly, tests on passive catheter heating were performed in a 1.5 T Avanto system (Siemens Healthcare Sector, Erlangen, Germany) using a ASTM Phantom in order to determine a possible maximum temperature rise. Secondly, a phantom was designed for simulation of the interface between blood and the vascular wall. The MR-RF induced temperature rise was simulated by catheter tip heating via a standard ablation generator. Power levels from 1 to 6 W were selected. Ablation duration was 120 s with no tip irrigation during the first 60 s and irrigation at rates from 2 ml/min to 35 ml/min for the remaining 60 s (Biotronik Qiona Pump, Berlin, Germany). The temperature was measured with fluoroscopic sensors (Luxtron, Santa Barbara, CA, USA) at a distance of 0 mm, 2 mm, 4 mm, and 6 mm from the catheter tip.</p> <p>Results</p> <p>A maximum temperature rise of 22.4°C at the catheter tip was documented in the MR scanner. This temperature rise is equivalent to the heating effect of an ablator's power output of 6 W at a contact force of the weight of 90 g (0.883 N). The catheter tip irrigation was able to limit the temperature rise to less than 2°C for the majority of examined power levels, and for all examined power levels the residual temperature rise was less than 8°C.</p> <p>Conclusion</p> <p>Up to a maximum of 22.4°C, the temperature rise at the tissue surface can be entirely suppressed by using the catheter's own irrigation system. The irrigated tip system can be used to increase MR safety of EP catheters by suppressing the effects of unwanted passive catheter heating due to RF exposure from the MR scanner.</p

Contact forces during hybrid atrial fibrillation ablation: an in vitro evaluation

PURPOSE: Data on epicardial contact force efficacy in dual epicardial–endocardial atrial fibrillation ablation procedures are lacking. We present an in vitro study on the importance of epicardial and endocardial contact forces during this procedure. METHODS: The in vitro setup consists of two separate chambers, mimicking the endocardial and epicardial sides of the heart. A circuit, including a pump and a heat exchanger, circulates porcine blood through the endocardial chamber. A septum, with a cut out, allows the placement of a magnetically fixed tissue holder, securing porcine atrial tissue, in the middle of both chambers. Two trocars provide access to the epicardium and endocardium. Force transducers mounted on both catheter holders allow real-time contact force monitoring, while a railing system allows controlled contact force adjustment. We histologically assessed different combinations of epi-endocardial radiofrequency ablation contact forces using porcine atria, evaluating the ablation’s diameters, area, and volume. RESULTS: An epicardial ablation with forces of 100 or 300 g, followed by an endocardial ablation with a force of 20 g did not achieve transmurality. Increasing endocardial forces to 30 and 40 g combined with an epicardial force ranging from 100 to 300 and 500 g led to transmurality with significant increases in lesion’s diameters, area, and volumes. CONCLUSIONS: Increased endocardial contact forces led to larger ablation lesions regardless of standard epicardial pressure forces. In order to gain transmurality in a model of a combined epicardial–endocardial procedure, a minimal endocardial force of 30 g combined with an epicardial force of 100 g is necessary

Feasibility of Spectrum Sharing Between Airborne Weather Radar and Wireless Local Area Networks

Emerging technologies such as wireless local area networks and cellular telephones have dramatically increased the use of wireless communications services within the last 10 years. The shortage of available spectrum exists due to increasing demand for wireless services and current spectrum allocation regulations. To alleviate this shortage, Research aims to improve spectral efficiency and to allow spectrum sharing between separately managed and non-coordinating communications systems. This thesis explores the feasibility of spectrum sharing between airborne weather radar and wireless local area networks at 9.3 GHz – 9.5 GHz. Characteristics of flight paths of aircraft using airborne weather radar and the low duty cycle of radar transmissions offer unique opportunities for spectrum sharing. But it was found that the extremely sensitive receivers provide challenges for designing a communications system meant for widespread use. The probability of causing harmful interference to airborne weather radar is too great for most types of wireless local area networks, but a direct sequence spread spectrum scheme could share spectrum with airborne weather radar. Bit errors in wireless local area network links caused by airborne weather radar interference do not significantly decrease the performance of the wireless local area network system. The distribution of interference outside of the airborne weather radar receiver by using direct sequence spread spectrum combined with the acceptable bit error rates indicate that while spectrum sharing between airborne weather radar and wireless local area network at 9.3 GHz – 9.5 GHz is not feasible, direct sequence spread spectrum systems can share spectrum with airborne weather radars under more limited assumptions