Individual Protons Research Articles

Towards a complete description of the reaction mechanisms between nitrenium ions and water.

Nitrenium ions are intermediates in the metabolic routes producing the highly carcinogenic nitrosamines and binding to DNA molecules. The reaction mechanism of nitrenium molecules with explicit water molecules is sensibly dependent on the number of waters: when a second molecule is involved, it acts as a catalyst for the reaction, lowering intrinsic activation barriers regardless of the substituent. For all cases, the reaction force constants and reaction electron flux indicate highly synchronous reactions for . Conversely, for highly non-synchronous reactions are obtained, involving two separate proton transfers happening early and late in the reaction path. As a test case, for the simplest reactions, orbital interactions within the NBO paradigm, bond orders, and their derivatives indicate that each individual proton transfer is highly synchronous. Molecular geometries were optimized and characterized at the B3LYP/6-311++G(d, p) level. Intrinsic reaction coordinates were calculated. CCSD(T) single point energies with the same basis were computed on all stationary points. The reaction force, reaction force constant, and reaction electron flux are used to study the evolution of the reacting systems. Natural bond orbitals are used to understand the primitive changes driving the reaction.

Octupole correlations in stable nucleus 153Eu within reflection-asymmetric particle rotor model

Abstract The observed low-lying K=5/2± positive- and negative-parity bands in the stable nucleus 153Eu are investigated by the reflection-asymmetric triaxial particle rotor model. The experimental energy spectra, the energy staggering parameters, as well as the intraband E2 and M1 transition probabilities are well reproduced. It is found that the calculated interband B(E1) values depend sensitively on the octupole deformation parameter β30, although the energy spectra and intraband E2 and M1 transitions can be reproduced without the octupole degree of freedom. The observed enhanced E1 transition probabilities can be reproduced with β30=0.05. The detailed analysis of the intrinsic wave functions shows these nearly degenerate positive- and negative-parity bands are built on two individual proton configurations, i.e., dominated by πg9/2[Ω=5/2] and πh11/2[Ω=5/2], respectively, which differs from the parity doublet bands built on a single parity-mixed configuration.

Proton dose deposition matrix prediction using multi-source feature driven deep learning approach

Proton dose deposition results are influenced by various factors, such as irradiation angle, beamlet energy and other parameters. The calculation of the proton dose deposition matrix (DDM) can be highly complex but is crucial in intensity-modulated proton therapy (IMPT). In this work, we present a novel deep learning (DL) approach using multi-source features for proton DDM prediction. The DL5 proton DDM prediction method involves five input features containing beamlet geometry, dosimetry and treatment machine information like patient CT data, beamlet energy, distance from voxel to beamlet axis, distance from voxel to body surface, and pencil beam (PB) dose. The dose calculated by Monte Carlo (MC) method was used as the ground truth dose label. A total of 40 000 features, corresponding to 8000 beamlets, were obtained from head patient datasets and used for the training data. Additionally, seventeen head patients not included in the training process were utilized as testing cases. The DL5 method demonstrates high proton beamlet dose prediction accuracy, with an average determination coefficient R 2 of 0.93 when compared to the MC dose. Accurate beamlet dose estimation can be achieved in as little as 1.5 milliseconds for an individual proton beamlet. For IMPT plan dose comparisons to the dose calculated by the MC method, the DL5 method exhibited gamma pass rates of γ(2 mm, 2%) and γ(3 mm, 3%) ranging from 98.15% to 99.89% and 98.80% to 99.98%, respectively, across all 17 testing cases. On average, the DL5 method increased the gamma pass rates to γ(2 mm, 2%) from 82.97% to 99.23% and to γ(3 mm, 3%) from 85.27% to 99.75% when compared with the PB method. The proposed DL5 model enables rapid and precise dose calculation in IMPT plan, which has the potential to significantly enhance the efficiency and quality of proton radiation therapy.

Novel radiation quality metrics accounting for proton energy spectra for RBE proton models.

For proton therapy, a relative biological effectiveness (RBE) of 1.1 is widely applied clinically. However, due to abundant evidence of variable RBE in vitro, and as suggested in studies of patient outcomes, RBE might increase by the end of the proton tracks, as described by several proposed variable RBE models. Typically, the dose averaged linear energy transfer ( ) has been used as a radiation quality metric (RQM) for these models. However, the optimal choice of RQM has not been fullyexplored. This study aims to propose novel RQMs that effectively weight protons of different energies, and assess their predictive power for variable RBE in proton therapy. The overall objective is to identify an RQM that better describes the contribution of individual particles to the RBE of protonbeams. High-throughput experimental set-ups of in vitro cell survival studies for proton RBE determination are simulated utilizing the SHIELD-HIT12A Monte Carlo particle transport code. For every data point, the proton energy spectra are simulated, allowing the calculation of novel RQMs by applying different power levels to the spectra of LET or effective ( ) values. A phenomenological linear-quadratic-based RBE model is then applied to the in vitro data, using various RQMs as input variables, and the model performance is evaluated by root-mean-square-error (RMSE) for the logarithm of cell surviving fractions of each datapoint. Increasing the power level, that is, putting an even higher weight on higher LET particles when constructing the RQM is generally associated with an increased model performance, with dose averaged (i.e., dose averaged cubed LET, ) resulting in a RMSE value 0.31, compared to 0.45 for a model based on (linearly weighted) , with similar trends also observed for track averaged and -basedRQMs. The results indicate that improved proton variable RBE models can be constructed assuming a non-linear RBE(LET) relationship for individual protons. If similar trends hold also for an in vitro-environment, variable RBE effects are likely better described by or tracked averaged cubed LET ( ), or corresponding -based RQM, rather than linearly weighted or which is conventionally applied today.

Optimization of Quantum Nuclei Positions with the Adaptive Nuclear-Electronic Orbital Approach.

The use of multicomponent methods has become increasingly popular over the last years. Under this framework, nuclei (commonly protons) are treated quantum mechanically on the same footing as the electronic structure problem. Under the use of atomic-centered orbitals, this can lead to some complications as the ideal location of the nuclear basis centers must be optimized. In this contribution, we propose a straightforward approach to determine the position of such centers within the self-consistent cycle of a multicomponent calculation, making use of individual proton charge centroids. We test the method on model systems including the water dimer, a protonated water tetramer, and a porphine system. Comparing to numerical gradient calculations, the adaptive nuclear-electronic orbital (NEO) procedure is able to converge the basis centers to within a few cents of an Ångström and with less than 0.1 kcal/mol differences in absolute energies. This is achieved in one single calculation and with a small added computational effort of up to 80% compared to a regular NEO- self-consistent field run. An example application for the human transketolase proton wire is also provided.

OPTIma: simplifying calorimetry for proton computed tomography in high proton flux environments

Objective. Proton computed tomography (pCT) offers a potential route to reducing range uncertainties for proton therapy treatment planning, however the current trend towards high current spot scanning treatment systems leads to high proton fluxes which are challenging for existing systems. Here we demonstrate a novel approach to energy reconstruction, referred to as ‘de-averaging’, which allows individual proton energies to be recovered using only a measurement of their integrated energy without the need for spatial information from the calorimeter. Approach. The method is evaluated in the context of the Optimising Proton Therapy through Imaging (OPTIma) system which uses a simple, relatively inexpensive, scintillator-based calorimeter that reports only the integrated energy deposited by all protons within a cyclotron period, alongside a silicon strip based tracking system capable of reconstructing individual protons in a high flux environment. GEANT4 simulations have been performed to examine the performance of such a system at a modern commercial cyclotron facility using a σ ≈ 10 mm beam for currents in the range 10–50 pA at the nozzle. Main results. Apart from low-density lung tissue, a discrepancy of less than 1% on the Relative Stopping Power is found for all other considered tissues when embedded within a 150 mm spherical Perspex phantom in the 10–30 pA current range, and for some tissues even up to 50 pA. Significance. By removing the need for the calorimeter system to provide spatial information, it is hoped that the de-averaging approach can facilitate clinically relevant, cost effective and less complex calorimeter systems for performing high current pCTs.

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Beam Dynamics Studies for the Target Beamlines of the High Brilliance Neutron Source

The High Brilliance Neutron Source (HBS) belongs to the class of High Current Accelerator based Neutron Sources (Hi-CANS). The driver Linac for the HBS must be able to reliably accelerate a 100 mA proton beam to an energy of 70 MeV [2, 1, 3]. The beam is sent pulse-by-pulse to three different targets via a multiplexer in the High Energy Beam Transfer (HEBT) section. Each individual proton pulse behind the multiplexer has a specific time structure in order to optimally serve the different instruments grouped around one target station. The main development steps of the HEBT are the development of a three-field septum magnet, which is an essential part of the multiplexer magnet system, the beam dynamics integration of the multiplexer magnet system into the beamline, and the ion-optical layout of the individual target beamlines.

(Invited) Crosscutting Materials and Molecular Catalysts in Hybrid Photoelectrodes for Liquid Solar Fuel Production

The Solar Hub entitled the C enter for Hybrid Approaches in Solar Energy to Liquid Fuels, or CHASE, is advancing the quest for liquid fuels from water, nitrogen, and/or carbon dioxide feedstocks with sunlight as the only energy source. To realize this quest, CHASE utilizes hybrid photoelectrodes based on molecular catalysts integrated with visible light absorbing semiconductors with controlled microenvironments to achieve liquid solar fuel production. These crosscutting materials serve as hybrid photoelectrodes in photoelectrochemical cells. This presentation will focus on recent advances on photocatalysis at hybrid Si interfaces with particular attention to the individual electron transfer and proton coupled electron transfer step(s) relevant to water oxidation and carbon dioxide reduction catalysis. The impact of CHASE findings on solar energy conversion and the quest for liquid solar fuels will be discussed.

Study of damped oscillating structures from charged and neutral K-meson electromagnetic form factors data

The damped oscillating structures were recently revealed in the proton “effective” form factor data. For the time being they can neither be confirmed nor disproved by investigations of the individual proton form factors data because the data have not yet achieved the required level of precision. On the other hand, conjectures that the oscillating structures are direct manifestations of the quark-gluon structure of the proton indicate that they should not be specific only to the proton and neutron. This opens a possibility to find these structures also in the data of other hadrons by the same procedure as for the proton. In this paper the oscillatory structures are investigated in the electromagnetic form factor data of the charged and neutral K-mesons. If the charged and neutral K-meson data are described by the three parametric formula by means of which the oscillating structures have been revealed for the proton (although with a large value of chi ^2/ndf) then oscillating structures appear. On the other hand, if the physically well founded Unitary and Analytic model of the K-meson electromagnetic structure is used for the description of the charged K-meson data, no damped oscillating structures are visible. However, in the case of the neutral K-meson data one cannot make a definite conclusion, and more precise data are needed. These results indicate that also the damped oscillating structures obtained from the “effective” proton form factor data are likely an artefact of the three parametric formula, which cannot describe the data with sufficient precision.

Subunit gating resulting from individual protonation events in Kir2 channels

Inwardly rectifying potassium (Kir) channels open at the ‘helix bundle crossing’ (HBC), formed by the M2 helices at the cytoplasmic end of the transmembrane pore. Introduced negative charges at the HBC (G178D) in Kir2.2 channels forces opening, allowing pore wetting and free movement of permeant ions between the cytoplasm and the inner cavity. Single-channel recordings reveal striking, pH-dependent, subconductance behaviors in G178D (or G178E and equivalent Kir2.1[G177E]) mutant channels, with well-resolved non-cooperative subconductance levels. Decreasing cytoplasmic pH shifts the probability towards lower conductance levels. Molecular dynamics simulations show how protonation of Kir2.2[G178D], or the D173 pore-lining residues, changes solvation, K+ ion occupancy, and K+ conductance. Ion channel gating and conductance are classically understood as separate processes. The present data reveal how individual protonation events change the electrostatic microenvironment of the pore, resulting in step-wise alterations of ion pooling, and hence conductance, that appear as ‘gated’ substates.

Subunit gating resulting from individual protonation events in Kir2 channels

Subunit gating resulting from individual protonation events in Kir2 channels

Subunit gating resulting from individual protonation events in Kir2 channels

Subunit gating resulting from individual protonation events in Kir2 channels

Interaction of Electrons and Positrons with Protons Aligned in One-Dimension Line

We present theoretical studies of electron and positron interaction with protons aligned in a one-dimension periodic line. The equally spaced protons were artificially generated where the individual protons are fixed in a certain position. The incident energies were 500 eV and 1000 eV. The electron and positron trajectories passing through these periodic multiple scattering objects were calculated using a classical trajectory Monte Carlo method. We show that this proton configuration has focusing and defocusing properties depending on the certain initial conditions.

Trends in prescribing volumes and costs of proton pump inhibitors in three outpatient specialties: a three-year retrospective study in a tertiary hospital in Thailand.

The study determined a comparative three-year trend in prescribing volumes and costs of proton pump inhibitors in three outpatient specialties of a tertiary hospital. Prescription data for three consecutive fiscal years (2016-2018) were extracted from a tertiary hospital electronic database, for the gastrointestinal, cardiovascular and orthopaedic outpatient specialties. The data collected were individual proton pump inhibitors, overall and individual prescribing volumes (capsule/tablet) and costs, stratified by specialty and fiscal year. Of the three specialties, the largest volume of proton pump inhibitor prescriptions, mostly for omeprazole, comes from the orthopaedic specialty (46%). In terms of prescribing costs, at the top is the cardiovascular specialty (45.75%). Lansoprazole, which is one of the proton pump inhibitors on in the national list of essential medicines, contributed most to the cost. Prescribing proton pump inhibitors that are not included in the national list of essential medicines were responsible for over 90% of the costs in the cardiovascular and gastrointestinal specialties. An escalating trend in prescribing varied proton pump inhibitors, that is, esomeprazole, lansoprazole, pantoprazole, dexlansoprazole and rabeprazole, all of which were not on the list of essential medicines, was evident in the latter. The highest volume of proton pump inhibitor prescribing-mostly of omeprazole, was issued by the orthopaedic specialty. The cardiovascular specialty was responsible for the largest amount of cost. The increases in the uses and costs of varying proton pump inhibitors which were outside the national list of essential medicines were notable in the gastrointestinal specialty.

Single pulse protoacoustic range verification using a clinical synchrocyclotron

Objective. Proton therapy as the next generation radiation-based cancer therapy offers dominant advantages over conventional radiation therapy due to the utilization of the Bragg peak; however, range uncertainty in beam delivery substantially mitigates the advantages of proton therapy. This work reports using protoacoustic measurements to determine the location of proton Bragg peak deposition within a water phantom in real time during beam delivery. Approach. In protoacoustics, proton beams have a definitive range, depositing a majority of the dose at the Bragg peak; this dose is then converted to heat. The resulting thermoelastic expansion generates a 3D acoustic wave, which can be detected by acoustic detectors to localize the Bragg peak. Main results. Protoacoustic measurements were performed with a synchrocyclotron proton machine over the exhaustive energy range from 45.5 to 227.15 MeV in clinic. It was found that the amplitude of the acoustic waves is proportional to proton dose deposition, and therefore encodes dosimetric information. With the guidance of protoacoustics, each individual proton beam (7 pC/pulse) can be directly visualized with sub-millimeter (<0.7 mm) resolution using single beam pulse for the first time. Significance. The ability to localize the Bragg peak in real-time and obtain acoustic signals proportional to dose within tumors could enable precision proton therapy and hope to progress towards in vivo measurements.

Predicting Severity of Radiation Induced Lymphopenia in Individual Proton Therapy Patients for Varying Dose Rate and Fractionation Using Dynamic 4-Dimensional Blood Flow Simulations

PurposeRadiation-induced lymphopenia has gained attention recently as the result of its correlation with survival in a range of indications, particularly when combining radiation therapy (RT) with immunotherapy. The purpose of this study is to use a dynamic blood circulation model combined with observed lymphocyte depletion in patients to derive the in vivo radiosensitivity of circulating lymphocytes and study the effect of RT delivery parameters. Methods and MaterialsWe assembled a cohort of 17 patients with hepatocellular carcinoma treated with proton RT alone in 15 fractions (fx) using conventional dose rates (beam-on time [BOT], 120 seconds) for whom weekly absolute lymphocyte counts (ALCs) during RT and follow-up were available. We used HEDOS, a time-dependent, whole-body, blood flow computational framework, in combination with explicit liver blood flow modeling, to calculate the dose volume histograms for circulating lymphocytes for changing BOTs (1 second-300 seconds) and fractionations (5 fx, 15 fx). From this, we used the linear cell survival model and an exponential model to determine patient-specific lymphocyte radiation sensitivity, α, and recovery, σ, respectively. ResultsThe in vivo–derived patient-specific α had a median of 0.65 Gy−1 (range, 0.30-1.38). Decreasing BOT to 1 second led to an increased average end-of-treatment ALC of 27.5%, increasing to 60.3% when combined with the 5-fx regimen. Decreasing to 5 fx at the conventional dose rate led to an increase of 17.0% on average. The benefit of both increasing dose rate and reducing the number of fractions was patient specificࣧpatients with highly sensitive lymphocytes benefited most from decreasing BOT, whereas patients with slow lymphocyte recovery benefited most from the shorter fractionation regimen. ConclusionsWe observed that increasing dose rate at the same fractionation reduced ALC depletion more significantly than reducing the number of fractions. High-dose-rates led to an increased sparing of lymphocytes when shortening the fractionation regimen, particularly for patients with radiosensitive lymphocytes at elevated risk.

Uncovering individual protonation events in Kir2 channels.

Inwardly rectifying potassium (Kir) channels play a critical role in stabilizing the membrane potential, thus controlling numerous physiological phenomena in various tissues. Channel conductance can be activated by cytoplasmic modulators that open the channel at the ‘helix bundle crossing’ (HBC), formed by the coming together of the M2 helix from each of the four subunits, at the cytoplasmic end of the transmembrane pore.

Measuring the Beam Energy in Proton Therapy Facilities Using ATLAS IBL Pixel Detectors

The accurate measurement of the beam range in the frame of quality assurance (QA) is a requirement for clinical use of a proton therapy machine. Conventionally used detectors mostly estimate the range by measuring the depth dose distribution of the protons. In this paper, we use pixel detectors designed for individual particle tracking in the high-radiation environment of the ATLAS experiment at LHC. The detector measures the deposited energy in the sensor for individual protons. Due to the limited dynamic energy range of the readout chip, several ways to measure the proton energy or range are examined. A staircase phantom is placed on the detector to perform an energy calibration relative to the NIST PSTAR stopping power database. In addition, track length measurements are performed using the detector aligned parallel with the beam axis to investigate the Linear Energy Transfer (LET) per pixel along the trajectory of individual protons. In this proof-of-principle study, we show that this radiation hardness detector can successfully be used to determine the initial proton energy for protons impinging on the sensor with an energy below 44 MeV after the range shifters. It becomes clear that an improvement of the energy resolution of the readout chip is required for clinical use.

Photoionization of Oriented HD(1Σ+) Yields Vibrating HD+(2Σ+) with Charge Breathing and Small Charge Transfer.

The eigenfunctions of the Hamiltonian associated with the oriented vibrating HD+(2Σ+) ion are calculated beyond the Born-Oppenheimer approximation in the nuclear frame. This makes it possible to study the fully correlated electron-nuclear dynamics of the HD+(2Σ+) after ionization of the HD(1Σ+) molecule. The dynamics is then characterized by the time-dependent probability densities and flux densities of the individual particles, i.e., deuteron, proton, and electron. The flux densities confirm that, although the electric dipole moment changes over time, there is no charge migration, as might be expected from the separation of energy levels of the vibronic states. Instead, the variations of the electric dipole moment over time are caused by small charge transfer and asymmetric charge vibration. Fourier transforms of the time-dependent probability and flux densities uncover the net asymmetric effective potential acting on the electron.