Polytechnic University of Milan

About: Polytechnic University of Milan is a education organization based out in Milan, Italy. It is known for research contribution in the topics: Finite element method & Population. The organization has 18231 authors who have published 58416 publications receiving 1229711 citations. The organization is also known as: PoliMi & L-NESS.

Secondary neutron dose during proton therapy using spot scanning

Abstract: Purpose: During proton radiotherapy, secondary neutrons are produced by nuclear interactions in the material in the beam line before and after entering the patient. The dose equivalent deposited by these neutrons is usually not considered in routine treatment planning. In this study, we estimated the neutron dose in patients from a spot scanning beam line by performing measurements and Monte Carlo simulations. Methods and Materials: Measurements of the secondary neutron dose were performed during irradiation of a water phantom with 177-MeV protons using a Bonner sphere and CR39 etch detectors. Additionally, Monte Carlo simulations were performed using the FLUKA code. Results: A comparison of our measurements with measurements taken at a beam line using the scatter foil technique shows a dose advantage of at least 10 for the spot scanning technique. In the region of the Bragg peak, the neutron dose equivalent can reach for a medium-sized target volume approximately 1% of the treatment dose. Neutron doses expected in healthy tissues of the patient (in the not-treated volume) are for large and medium target volumes, approximately 0.004 Sv and 0.002 Sv per treatment Gy, respectively. Conclusions: We conclude from the measurements and simulations that the dose deposited by secondary neutrons during proton radiotherapy using the spot scanning technique can be neglected in the treatment region. In the healthy tissue, the dose coming from neutrons (0.002 Sv per treatment Gy) is approximately a factor of two larger than during photon treatment (0.001 Sv). These contributions to the integral dose from neutrons are still very low when compared to the dose sparing that can be achieved by using a proton beam instead of photons.

C-SPARQL : A Continuous Query Language for RDF Data Streams

Abstract: This article defines C-SPARQL, an extension of SPARQL whose distinguishing feature is the support of continuous queries, i.e. queries registered over RDF data streams and then continuously executed. Queries consider windows, i.e. the most recent triples of such streams, observed while data is continuously flowing. Supporting streams in RDF format guarantees interoperability and opens up important applications, in which reasoners can deal with evolving knowledge over time. C-SPARQL is presented by means of a full specification of the syntax, a formal semantics, and a comprehensive set of examples, relative to urban computing applications, that systematically cover the SPARQL extensions. The expression of meaningful queries over streaming data is strictly connected to the availability of aggregation primitives, thus C-SPARQL also includes extensions in this respect.

Experimental scattershot boson sampling

Abstract: Boson sampling is a computational task strongly believed to be hard for classical computers, but efficiently solvable by orchestrated bosonic interference in a specialized quantum computer. Current experimental schemes, however, are still insufficient for a convincing demonstration of the advantage of quantum over classical computation. A new variation of this task, scattershot boson sampling, leads to an exponential increase in speed of the quantum device, using a larger number of photon sources based on parametric down-conversion. This is achieved by having multiple heralded single photons being sent, shot by shot, into different random input ports of the interferometer. We report the first scattershot boson sampling experiments, where six different photon-pair sources are coupled to integrated photonic circuits. We use recently proposed statistical tools to analyze our experimental data, providing strong evidence that our photonic quantum simulator works as expected. This approach represents an important leap toward a convincing experimental demonstration of the quantum computational supremacy.