One of the defining features of Bitcoin and the thousands of cryptocurrencies that have been derived from it is a globally visible transaction ledger. While Bitcoin uses pseudonyms as a way to hide the identity of its participants, a long line of research has demonstrated that Bitcoin is not anonymous. This has been perhaps best exemplified by the development of clustering heuristics, which have in turn given rise to the ability to track the flow of bitcoins as they are sent from one entity to another. In this paper, we design a new heuristic that is designed to track a certain type of flow, called a peel chain, that represents many transactions performed by the same entity; in doing this, we implicitly cluster these transactions and their associated pseudonyms together. We then use this heuristic to both validate and expand the results of existing clustering heuristics. We also develop a machine learning-based validation method and, using a ground-truth dataset, evaluate all our approaches and compare them with the state of the art. Ultimately, our goal is to not only enable more powerful tracking techniques but also call attention to the limits of anonymity in these systems.

A novel breathing phantom was designed for being used in conventional and ion-beam radiotherapy as well as for medical imaging. Accurate dose delivery and patient safety are aimed to be verified for four-dimensional (4D) treatment techniques compensating for breathing-induced tumor motion. The phantom includes anthropomorphic components representing an average human thorax. It consists of real tissue equivalent materials to fulfill the requirements for dosimetric experiments and imaging purposes. The different parts of the torso (lungs, chest wall, and ribs) and the tumor can move independently. Simple regular movements, as well as more advanced patient-specific breathing cycles are feasible while a reproducible setup can be guaranteed. The phantom provides the flexibility to use different types of dosimetric devices and was designed in a way that it is robust, transportable and easy to handle. Tolerance levels and the reliability of the phantom setup were determined in combination with tests on motion accuracy and reproducibility by using infrared optical tracking technology. Different imaging was performed including positron emission tomography imaging, 4D computed tomography as well as real-time in-room imaging. The initial dosimetric benchmarking studies were performed in a photon beam where dose parameters are predictable and the dosimetric procedures well established.

ELI-Beamlines (ELI stands for Extreme Light Infrastructure) is a new EU funded laser facility located near Prague, in Czech Republic. It will use laser-driven plasma sources to accelerate particles and host a dedicated proton beamline called ELIMAIA (ELI Multidisciplinary Applications of laser-Ion Acceleration) designed to reach energies up to 250 MeV. This beamline could be exploited to study possible future medical application of laser-driven beams. The first part of this paper introduces the beamline, the corresponding source terms and the complete set-up. The second part of the paper details the evaluation of the ambient dose equivalent and the activation study inside the experimental halls based on Monte-Carlo simulation. These calculations show that the ELIMAIA operation is safe as long as nobody is present in the hall when the beam is on.

Introduction: In recent years extra-corporal application of boron neutron capture therapy (BNCT) was evaluated for liver primary tumors or liver metastases. A prerequisite for such a high-risk procedure is proof of preferential delivery and high uptake of a B-10-pharmaceutical in liver malignancies. In this work we evaluated in a preclinical tumor model if [F-18]FBPA tissue distribution measured with PET is able to predict the tissue distribution of [B-10]L-BPA.Methods: Tumor bearing mice (hepatocellular carcinoma cell line, HuH-7) were either subject of a [F-18]FBPA-PET scan with subsequent measurement of radioactivity content in extracted organs using a gamma counter or injected with [B-10]L-BPA with tissue samples analyzed by prompt gamma activation analysis (PGAA) or quantitative neutron capture radiography (QNCR).The impact of L-tyrosine, L-DOPA and L-BPA preloading on the tissue distribution of [F-18]FBPA and [B-10]L-BPA was evaluated and the pharmacokinetics of [F-18]FBPA investigated by compartment modeling.Results: We found a significant correlation between [F-18]FBPA and [B-10]L-BPA uptake in tumors and various organs as well as high accumulation levels in pancreas and kidneys as reported in previous studies. Tumor-to-liver ratios of [F-18]FBPA ranged from 1.2 to 1.5. Preloading did not increase the uptake of [F-18]FBPA or [B-10]L-BPA in any organ and compartment modeling showed no statistically significant differences in [F-18]FBPA tumor kinetics.Conclusions: [F-18]FBPA-PET predicts [B-10]L-BPA concentration after amino acid preloading in HuH-7 hepatocellular carcinoma models. Preloading had no effect on tumor uptake of [F-18]FBPA.Advances in knowledge: Despite differences in chemical structure and administered dose [F-18]FBPA and [B-10]L-BPA demonstrate an equivalent biodistribution in a preclinical tumor model.Implications for patient care: [F-18]FBPA-PET is suitable for treatment planning and dose calculations in BNCT applications for liver malignancies. However, alternative tracers with more favorable tumor-to-liver ratios should be investigated. (C) 2016 Elsevier Inc. All rights reserved.

Bonner Spheres Spectrometry in its high-energy extended version is an established method to quantify neutrons at a wide energy range from several meV up to more than 1 GeV. In order to allow for quantitative measurements, the responses of the various spheres used in a Bonner Sphere Spectrometer (BSS) are usually simulated by Monte Carlo (MC) codes over the neutron energy range of interest. Because above 20 MeV experimental cross section data are scarce, intra-nuclear cascade (INC) and evaporation models are applied in these MC codes. It was suspected that this lack of data above 20 MeV may translate to differences in simulated BSS response functions depending on the MC code and nuclear models used, which in turn may add to the uncertainty involved in Bonner Sphere Spectrometry, in particular for neutron energies above 20 MeV. In order to investigate this issue in a systematic way, EURADOS (European Radiation Dosimetry Group) initiated an exercise where six groups having experience in neutron transport calculations with the MC codes (MCNP, MCNPX, FLUKA, PHITS, MARS, or GEANT4) calculated the responses of a bare He-3 proportional counter, a He-3 proportional counter embedded in the middle of a 9 inch polyethylene sphere, and a He-3 proportional counter centred in a 9 inch polyethylene sphere containing a lead shell, at neutron energies of 1, 10, 100, and 1000 MeV. In general, calculated responses agreed very well for neutron energies below 20 MeV, whatever MC code used. At higher energies, however, certain differences were observed among the different calculations, which may mainly be attributed to the application of different INC models and their parameters. It was found that up to 1 GeV most of the results ranged between calculations previously published that were obtained with MCNP/LAHET using the Bertini INC model and GEANT4 using the Binary and Bertini INC models. These results indicate that use of different MC codes and INC models for the calculation of BSS response functions may result in an uncertainty of unfolded neutron fluences above 20 MeV of about 20%. (C) 2014 Elsevier Ltd. All rights reserved.

This paper represents the first attempt to discuss the use of an artificial single-crystal diamond as a new microdosimeter. The Diamond MicroDosimeter (DMD) detecting region is a thin layer of highly controlled thickness ( <; 5 μm) and high purity intrinsic monocrystalline diamond grown over a backing boron doped monocrystalline diamond. This viable, small, compact and user-friendly device is able to obtain spectra of the energy deposition in sensitive volumes of the order of micrometer. The paper reports the first experimental tests performed to measure the dose distribution in terms of lineal energy and the simulation performed by the Monte Carlo code FLUKA to optimize the design of the new DMD. Advantages and shortcomings of the DMD are discussed.

FLUKA is a general purpose Monte Carlo code capable of handling all radiation components from thermal energies (for neutrons) or 1 key (for all other particles) to cosmic ray energies and can be applied in many different fields. Presently the code is maintained on Linux. The validity of the physical models implemented in FLUKA has been benchmarked against a variety of experimental data over a wide energy range, from accelerator data to cosmic ray showers in the Earth atmosphere. FLUKA is widely used for studies related both to basic research and to applications in particle accelerators, radiation protection and dosimetry, including the specific issue of radiation damage in space missions, radiobiology (including radiotherapy) and cosmic ray calculations.After a short description of the main features that make FLUKA valuable for these topics, the present paper summarizes some of the recent applications of the FLUKA Monte Carlo code in the nuclear as well high energy physics. In particular it addresses such topics as accelerator related applications. (C) 2011 Elsevier B.V. All rights reserved.

The Austrian Institute of Technology coordinates the project MATSIM (MATROSHKA Simulation) in collaboration with the Vienna University of Technology and the German Aerospace Center, to perform FLUKA Monte Carlo simulations of the MATROSHKA numerical phantom under the radiation environment at the International Space Station (ISS). MATSIM is carried as co-investigation of the ESA ELIPS project MATROSHKA, an international collaboration of more than 18 research institutes and space agencies from all over the world, under the science and project lead of the German Aerospace Center. MATROSHKA is an ESA facility designed to determine the radiation exposure of an astronaut during an extravehicular activity at the ISS. During the project MATSIM a computer tomography scan of the MATROSHKA phantom has been converted into a high resolution 3-dimensional voxel model. The imparted energy and dose inside the model is determined. Part of the project is the phantom validation under reference radiation conditions. Investigations are carried out under ISS cosmic radiation conditions. The aim of the MATSIM project is the provision of comprehensive risk assessment of radiation hazard to humans in space due to ionising high energy particle radiation.

The assessment of radiation damage to electronics is a complex process and requires a detailed description of the full particle energy spectra, as well as a clear characterization of the quantities used to predict radiation damage.FLUKA, a multi-purpose particle interaction and transport code, is capable of calculating proton-proton and heavy ion collisions at LHC energies and beyond.It correctly describes the entire hadronic and electromagnetic particle cascade initiated by secondary particles from TeV energies down to thermal neutrons, and provides direct scoring capabilities essential to estimate in detail the possible risk of radiation damage to electronics.This paper presents the FLUKA capabilities for applications related to radiation damage to electronics, providing benchmarking examples and showing the practical applications of FLUKA at CERN facilities such as CNGS and LHC.Related applications range from the study of device effects, the detailed characterization of the radiation field and radiation monitor calibration, to the input requirements for important mitigation studies including shielding, relocation or other options.

In recent years, many ionizing radiation detectors based upon artificial diamond have been proposed and applied in many fields and at various energy ranges. Single Crystal Diamond (SCD) have not been used, so far, in microdosimetry and this paper represents one of the first attempts to obtain spectra of the energy deposition in artificial-diamond sensitive volumes of the order of the micrometer. The new Diamond MicroDosimeter (DMD) is based upon a layered structure with a detecting region of less then 5 μm. This prototype is fabricated at Rome “Tor Vergata” University using a Chemical Vapour Deposition (CVD) technique depositing a thin layer of highly controlled thickness. The paper reports the comparison between simulations performed by the Monte Carlo code FLUKA and first experimental tests performed with alphas to measure the dose distribution in terms of lineal energy.

The multi-purpose particle interaction and transport code FLUKA is integral part of all radiation protection studies for the design and operation of the Large Hadron Collider (LHC) at CERN.It is one of the very few codes available for this type of calculations which is capable to calculate in one and the same simulation proton-proton and heavy ion collisions at LHC energies as well as the entire hadronic and electromagnetic particle cascade initiated by secondary particles in detectors and beam-line components from TeV energies down to energies of thermal neutrons.The present paper reviews these capabilities of FLUKA in sketching the relevant physics models along with examples of radiation protection studies for the LHC such as shielding studies for underground areas occupied by personnel during LHC operation and the simulation of induced radioactivity around beam loss points.Integral part of the FLUKA development is a careful benchmarking of specific models as well as the code performance in actual, complex applications which is demonstrated with examples of studies relevant to radiation protection at the LHC.

Using protons for the treatment of ocular melanoma (especially of posterior pole tumours), the radiation quality of the beam must be precisely assessed to preserve the vision and to minimise the damage to healthy tissue. The radiation quality of a therapeutic proton beam at the Centre Antoine Lacassagne in Nice (France) was measured using microdosimetric techniques, i.e. a miniaturised version of a tissue-equivalent proportional counter. Measurements were performed in a 1-µm site at different depths in a Lucite phantom. Experimental data showed a significant increase in the beam quality at the distal edge of the spread-out Bragg peak (SOBP). In this paper, the numerical simulation of the experimental setup is done with the FLUKA Monte Carlo radiation transport code. The calculated microdosimetric spectra are compared with the measured ones at different depths in tissue for a monoenergetic proton beam (E=62 MeV) and for a modulated SOBP. Numerically and experimentally predicted relative biological effectiveness values are in good agreement. The calculated frequency-averaged and dose-averaged lineal energy mean values are consistent with measured data.

In 2007, the European Space Agency (ESA) initiated the development of European Crew Personal Active Dosimeters. The hardware development objective is to produce an active personal dosimeter which shows absorbed dose and dose equivalent spectra similar to a Tissue Equivalent Proportional Counter (TEPC), but which is based on more robust silicon detector devices. Several detector/dosimeter components have been investigated – by computer simulations – for their performance in the radiation field at the ISS position.

Motivated by differences in the predicted fragmentation of heavy ions at energies around 5 GeV/A as employed in the event generators used by the FLUKA Monte Carlo Code [1], a set of measurements were carried out at the AGS facility at the Brookhaven National Laboratory to determine as much information as possible about the cross sections to allow harmonization of those event generators for these incident lab energies. The FLUKA Code employs the RQMD event generator of Sorge [2] for heavy ion interactions starting at 100 MeV/A and extending into the region around 5 GeV/A. Above those energies the DPMJET code of Ranft and Roesler [3] is typically employed to simulate such interactions. The detailed predictions of these event generators had some disagreement in the vicinity of this crossover energy and in order to tune these codes to be in closer harmony at the transition, and of course to be simulating nature as closely as possible, data were taken at 3, 5 and 10 GeV/A with beams of Fe, Si and C on a variety of targets including C, A1. Fe and Cu. The Fe data have not been fully analyzed, but results from the C and Si beams are available and the forward fragment spectrum along with a measurement of the charged particle angular distribution in a set of Si strip detectors out to about 45 degrees in the lab are available. These include sufficient statistics to provide the charged particle distributions as a function of the major projectile fragment. The detectors used in this measurement were based on what were reasonably available to us, and as such were limited in capability, and required separate data acquisition systems. Nevertheless, spectra were obtained that should be sufficient to enable the harmonization of the event generator codes at the crossover energy. This paper discusses only the experimental results and not the impact of those results on the FLUKA code.

In the past few years, miniaturized tissue-equivalent gas detectors (mini TEPCs) have been developed for application of microdosimetry in radiotherapy. These mini-TEPCs are characterised by millimetric dimensions. They are equipped neither with an internal calibration source nor with electric field tubes, which would properly define the sensitive volume hence the simulated site size. In spite of these lacks, mini TEPCs working in gas flow conditions have proven to be precise and reliable detectors. However, for future therapeutic plans including microdosimetric data, consistency between experimental and calculated data is important. Existing general-purpose Monte Carlo codes have proven to be very useful to calculate the energy deposition due to ionization in macroscopic targets, even in various complex radiation fields. However, theoretical models implemented in these codes for simulating electron transport and straggling are valid only for energies above a few keV. This restricts their applicability for simulating radiation transport at a micrometric level, where low-energy electrons play a dominant role. In this work, we calculate frequency distributions of deposited energy in a mini TEPC (with sizes equivalent to 1 and 2 pm) due to photons using the Monte Carlo code FLUKA. Comparisons between simulated and experimental data show a rather good agreement. Differences due to different FLUKA settings are discussed. (C) 2010 Published by Elsevier Ltd.

The assessment of the exposure to cosmic radiation onboard aircraft is one of the preoccupations of bodies responsible for radiation protection. Cosmic particle flux is significantly higher onboard aircraft than at ground level and its intensity depends on the solar activity. The dose is usually estimated using codes validated by the experimental data. In this paper, a comparison of various codes is presented, some of them are used routinely, to assess the dose received by the aircraft crew caused by the galactic cosmic radiation. Results are provided for periods close to solar maximum and minimum and for selected flights covering major commercial routes in the world. The overall agreement between the codes, particularly for those routinely used for aircraft crew dosimetry, was better than +/- 20 % from the median in all but two cases. The agreement within the codes is considered to be fully satisfactory for radiation protection purposes.