Calculation Of Energy Transfer Research Articles

Structure and Spectral Properties of Er3+-Doped Bismuth Telluride Near-Infrared Laser Glasses.

TeO2-Bi2O3-B2O3-ZnO laser glasses doped with Er3+ were synthesized through an optimized melt-quenching method. The absorption spectra at 808 nm LD pumping were studied. Various spectral tests and data analyses indicate that the maximum fluorescence emission intensity can be obtained when the Er3+ doping concentration reaches 2%. In this case, the emission cross-section can reach up to 9.12 × 10-21 cm2 and the gain coefficient at 1.55 μm is 6.17 cm-1. Simultaneously, the sample has a lower phonon energy in the high-frequency band at 1077 cm-1, which reduces the probability of non-radiative relaxation. The calculated energy transfer coefficient CD-A is 13.8 × 10-40 cm6/s, reflecting the high cross-relaxation probability of Er3+ in the sample, which promotes the luminescence of 1.55 μm and favors the emission in the near-infrared region. The comprehensive results demonstrate that the prepared Er3+-doped bismuth telluride laser glass can be used as a promising and high-quality gain material for near-infrared lasers.

Deep learning based linear energy transfer calculation for proton therapy

Objective. This study aims to address the limitations of traditional methods for calculating linear energy transfer (LET), a critical component in assessing relative biological effectiveness (RBE). Currently, Monte Carlo (MC) simulation, the gold-standard for accuracy, is resource-intensive and slow for dose optimization, while the speedier analytical approximation has compromised accuracy. Our objective was to prototype a deep-learning-based model for calculating dose-averaged LET (LETd) using patient anatomy and dose-to-water (DW) data, facilitating real-time biological dose evaluation and LET optimization within proton treatment planning systems. Approach. 275 4-field prostate proton Stereotactic Body Radiotherapy plans were analyzed, rendering a total of 1100 fields. Those were randomly split into 880, 110, and 110 fields for training, validation, and testing. A 3D Cascaded UNet model, along with data processing and inference pipelines, was developed to generate patient-specific LETd distributions from CT images and DW. The accuracy of the LETd of the test dataset was evaluated against MC-generated ground truth through voxel-based mean absolute error (MAE) and gamma analysis. Main results. The proposed model accurately inferred LETd distributions for each proton field in the test dataset. A single-field LETd calculation took around 100 ms with trained models running on a NVidia A100 GPU. The selected model yielded an average MAE of 0.94 ± 0.14 MeV cm−1 and a gamma passing rate of 97.4% ± 1.3% when applied to the test dataset, with the largest discrepancy at the edge of fields where the dose gradient was the largest and counting statistics was the lowest. Significance. This study demonstrates that deep-learning-based models can efficiently calculate LETd with high accuracy as a fast-forward approach. The model shows great potential to be utilized for optimizing the RBE of proton treatment plans. Future efforts will focus on enhancing the model’s performance and evaluating its adaptability to different clinical scenarios.

Cyclic energy: the transcendental relevance of respiratory rate. A retrospective observational study with Bayesian analysis

Introduction The calculation of energy transfer in patients with acute respiratory distress syndrome (ARDS), has multiple interpretations and proposals. The parameters described as safe to minimize mechanical ventilator-associated lung injury (VALI) include only static values in their conception, and dynamic variables have been relegated to a secondary role. Subjects and Methods Analytical, observational, retrospective study of patients hospitalized in a respiratory intensive care unit, with a diagnosis of severe ARDS due to SARS-CoV-2 in whom mechanical ventilator management was guided by the use of esophageal catheter for the calculation of ventilatory variables. Thirty-four patients were included in this study, 23.5 % were women and the mean body mass index was 34.9 kg/m2. The primary objective was to quantify the amount of energy (Mechanical Power MP) transmitted by using multiple known equations and the secondary objective was to find the variables best associated with such energy transfer and with the severity of ARDS using Bayesian analysis. Results A mean of 22.2 days on invasive mechanical ventilation was recorded. Baseline MPGattinoni averaged 21.4 J/min, which did not change significantly at 30 minutes (7.5%) or 24 hours (- 0.4%) from baseline, despite esophageal catheter-guided management. The Bayesian analyses used to calculate the a posteriori inclusion probability showed that respiratory rate was the only variable consistently related to energy transfer, regardless of the equation used for its calculation and the chronological time at which these equations were measured [baseline MPGattinoni: (mean, 0.89; 95% Cred Interval: 0.75 to 1.02), at 30 minutes: (mean, 1.09; 95% Cred Interval: 0.68 to 1.49), at 24 hours: (mean, 0.65; 95% Cred Interval: 0.01 to 1.03)] or [baseline MPModesto: (mean, 0.1; 95% Cred Interval: 0.09 to 0.1), at 30 minutes: (mean, 0.1; 95% Cred Interval: 0.09 to 0.1), at 24 hours: (mean, 0.1; 95% Cred Interval: 0.09 to 0.1)]. Conclusions In severe ARDS, it is essential to minimize VALI. The calculation of energy transfer, regardless of the equation used, should always be a dynamic objective to be measured. Respiratory rate is probably the most relevant dynamic variable in the genesis of VALI. Keywords: mechanical power, elastic power, respiratory rate, ARDS, COVID-19

Effects of nuclear interaction corrections and trichrome fragment spectra modelling on dose and linear energy transfer distributions in carbon ion radiotherapy

Background and PurposeNuclear interaction correction (NIC) and trichrome fragment spectra modelling improve relative biological effectiveness-weighted dose (DRBE) and dose-averaged linear energy transfer (LETd) calculation for carbon ions. The effect of those novel approaches on the clinical dose and LET distributions was investigated. Materials and MethodsThe effect of the NIC and trichrome algorithm was assessed, creating single beam plans for a virtual water phantom with standard settings and NIC + trichrome corrections. Reference DRBE and LETd distributions were simulated using FLUKA version 2021.2.9. Thirty clinically applied scanned carbon ion treatment plans were recalculated applying NIC, trichrome and NIC + trichrome corrections, using the LEM low dose approximation and compared to clinical plans (base RS). Four treatment sites were analysed: six prostate adenocarcinoma, ten head and neck, nine locally advanced pancreatic adenocarcinoma and five sacral chordoma. The FLUKA and clinical plans were compared in terms of DRBE deviations for D98%, D50%, D2% for the clinical target volume (CTV) and D50% in ring-like dose regions retrieved from isodose curves in base RS plans. Additionally, region-based median LETd deviations and global gamma parameters were evaluated. ResultsDose deviations comparing baseRS and evaluation plans were within ± 1% supported by γ-pass rates over 97% for all cases. No significant LETd deviations were reported in the CTV, but significant median LETd deviations were up to 80% for very low dose regions. ConclusionOur results showed improved accuracy of the predicted DRBE and LETd. Considering clinically relevant constraints, no significant modifications of clinical protocols are expected with the introduction of NIC + trichrome.

A structure of the relict phycobilisome from a thylakoid-free cyanobacterium

Phycobilisomes (PBS) are antenna megacomplexes that transfer energy to photosystems II and I in thylakoids. PBS likely evolved from a basic, inefficient form into the predominant hemidiscoidal shape with radiating peripheral rods. However, it has been challenging to test this hypothesis because ancestral species are generally inaccessible. Here we use spectroscopy and cryo-electron microscopy to reveal a structure of a “paddle-shaped” PBS from a thylakoid-free cyanobacterium that likely retains ancestral traits. This PBS lacks rods and specialized ApcD and ApcF subunits, indicating relict characteristics. Other features include linkers connecting two chains of five phycocyanin hexamers (CpcN) and two core subdomains (ApcH), resulting in a paddle-shaped configuration. Energy transfer calculations demonstrate that chains are less efficient than rods. These features may nevertheless have increased light absorption by elongating PBS before multilayered thylakoids with hemidiscoidal PBS evolved. Our results provide insights into the evolution and diversification of light-harvesting strategies before the origin of thylakoids.

Luminescence properties and energy transfer of Nd3+- Er3+/ Nd3+-Pr3+ co-doped LFP glasses system

The motivation for this research is that the emission spectra using directly pumped laser diodes have not yet been found. We want to explore the luminescence properties of a co-doped laser material utilizing a diode laser as an optical pump. The research method used standard melt-quench and was stimulated by a laser diode (808 and 980 nm). The double doped of Nd3+- Er3+/Nd3+-Pr3+ ions with glasses system of lithium-fluorophosphate (LFP) had a strong band emission at 1056 nm, which transitioned at 4F3/2 → 4I11/2 and showed a drop in intensity from co-doping with Er3+ and Pr3+ ions. The fluorescence width at half maximum (FWHM) of the glasses is calculated to identify whether the sample may be used as a laser application. The FWHM values are found to be 22–28 nm. Decay time values were shown to decrease with increasing concentrations of Er3+ and Pr3+ ions and were used for energy transfer calculations. The Quantum Yields (QYs), efficiency in the transfer of energy and the possibility transfer energy were measured and calculated that confirm the possibility of energy transfer from Nd3+ to Er3+ and Pr3+ ions. Since, the emission spectrum at 1535 nm was found, this is a good reason for it to be used as an optical device.

Judd-Ofelt parameters and energy transfer rates of α-NaYF4:Eu3+– a theoretical and experimental study

We report the analysis of Europium (Eu3+) ion-doped NaYF4 thin films from an experimental and theoretical complementary point of view. The pristine and Eu3+ doped-NaYF4 thin films were obtained by electrochemical deposition in the cubic phase (α-NaYF4), which were fully characterized by X-ray diffraction, scanning electron microscopy, and photoluminescence techniques. The emission spectrum of α-NaYF4:Eu3+ exhibits two intense bands at 610 and 628 nm for 5D0 → 7F2 transition with an excitation energy source at 245 nm. The experimental emission spectrum of α-NaYF4:Eu3+ thin films suggests that the D4h could be the local point symmetry around Eu3+ because of the number of sublevels in 5D0 → 7F1,2 transitions. The LUMPAC software was used to calculate the excited states, Judd-Ofelt (J-O) parameters, and energy transfer rates (ETR) from ligand to Eu3+ semi-empirically, using the local point group symmetry proposed in this work. The obtained J-O parameters are Ω2 = 15.39 × 10−20 cm2, Ω4 = 2.14 × 10−20 cm2, and Ω6 = 0.1275 × 10−20 cm2, where Ω6 was calculated by the QDC method despite of 5D0→7F6 transition is not observed in the experimental emission spectrum. The calculated energy transfer rates give the energy transitions from ligand S1→T (singlet→triplet) to T→Eu3+. Finally, the analysis of molecular orbitals derived from time dependent-DFT calculations confirms that the electronic transfer occurs from F− → Eu3+ (from ligand to Eu3+).

A flaw in applying the FRET technique to evaluate the distance between ligands and tryptophan residues in human serum albumin: Proposal of correction.

Due to its primordial function as a drug carrier, human serum albumin (HSA) is extensively studied regarding its binding affinity with developing drugs. Förster resonance energy transfer (FRET) is frequently applied as a spectroscopic molecular ruler to measure the distance between the binding site and the ligand. In this work, we have shown that most of the published results that use the FRET technique to estimate the distance from ligands to the binding sites do not corroborate the crystallography data. By comparing the binding affinity of dansyl-proline with HSA and ovotransferrin, we demonstrated that FRET explains the quenching provoked by the interaction of ligands in albumin. So, why does the distance calculation via FRET not corroborate the crystallography data? We have shown that this inconsistency is related to the fact that a one-to-one relationship between donor and acceptor is not present in most experiments. Hence, the quenching efficiency used for calculating energy transfer depends on distance and binding constant, which is inconsistent with the correct application of FRET as a molecular ruler. We have also shown that the indiscriminate attribution of 2/3 to the relative orientation of transition dipoles of the acceptor and donor (κ2) generates inconsistencies. We proposed corrections based on the experimental equilibrium constant and theoretical orientation of transition dipoles to correct the FRET results.

Cold Collisions of Ro-Vibrationally Excited D2 Molecules.

The H2 + H2 system has long been considered a benchmark system for ro-vibrational energy transfer in bimolecular collisions. However, most studies thus far have focused on collisions involving H2 molecules in the ground vibrational level or in the first excited vibrational state. While H2 + H2/HD collisions have received wide attention due to the important role they play in astrophysics, D2 + D2 collisions have received much less attention. Recently, Zhou et al. [ Nat. Chem. 2022, 14, 658-663, DOI: 10.1038/s41557-022-00926-z] examined stereodynamic aspects of rotational energy transfer in collisions of two aligned D2 molecules prepared in the v = 2 vibrational level and j = 2 rotational level. Here, we report quantum calculations of rotational and vibrational energy transfer in collisions of two D2 molecules prepared in vibrational levels up to v = 2 and identify key resonance features that contribute to the angular distribution in the experimental results of Zhou et al. The quantum scattering calculations were performed in full dimensionality and using the rigid-rotor approximation using a recently developed highly accurate six-dimensional potential energy surface for the H4 system that allows descriptions of collisions involving highly vibrationally excited H2 and its isotopologues.

An efficient time-domain implementation of the multichromophoric Förster resonant energy transfer method.

The excitation energy transfer (EET) process for photosynthetic antenna complexes consisting of subunits, each comprised of multiple chromophores, remains challenging to describe. The multichromophoric Förster resonance energy transfer theory is a popular method to describe the EET process in such systems. This paper presents a new time-domain method for calculating energy transfer based on the combination of multichromophoric Förster resonance energy transfer theory and the Numerical Integration of the Schrödinger Equation method. After validating the method on simple model systems, we apply it to the Light-Harvesting antenna 2 (LH2) complex, a light harvesting antenna found in purple bacteria. We use a simple model combining the overdamped Brownian oscillators to describe the dynamic disorder originating from the environmental fluctuations and the transition charge from the electrostatic potential coupling model to determine the interactions between chromophores. We demonstrate that with this model, both the calculated spectra and the EET rates between the two rings within the LH2 complex agree well with experimental results. We further find that the transfer between the strongly coupled rings of neighboring LH2 complexes can also be well described with our method. We conclude that our new method accurately describes the EET rate for biologically relevant multichromophoric systems, which are similar to the LH2 complex. Computationally, the new method is very tractable, especially for slow processes. We foresee that the method can be applied to efficiently calculate transfer in artificial systems as well and may pave the way for calculating multidimensional spectra of extensive multichromophoric systems in the future.

Heat-conserving three-temperature model for ultrafast demagnetization in nickel

Multireservoir models are widely used for modeling and interpreting ultrafast magnetization dynamics. Here we introduce an alternative formulation to existing three-temperature models for the treatment of spin, electron, and lattice temperatures in magnetization dynamics simulations. In contrast to most existing models of calculations of energy transfer between reservoirs in these types of simulations, the heat distribution of the spin and lattice subsystems is evaluated during the simulation instead of being calculated a priori. The model is applied to investigate the demagnetization and remagnetization of fcc Ni, when subjected to a strong laser pulse. In particular, our model results in a fast interplay between the electron and spin subsystems which reproduces the main features of experimental data for fcc Ni significantly better than most reported three-temperature models. We also show that the way in which the electron, spin, and lattice heat capacities are described can have a significant impact on the simulated ultrafast dynamics. By introducing spin-lattice couplings in the simulation, it is shown that these explicit interactions only have a marginal impact on the magnetization dynamics of fcc Ni, albeit it is more pronounced for higher laser pulse powers.

Brief Research on the Biophysical Study and Anticancer Behavior of Pt(II) Complexes: Their DNA/BSA Binding, Molecular Docking, and Cytotoxic Property.

The potent bidentate carrier ligand 2-picolylamine (pic) has been used to synthesize Pt(II) complexes to know their bioactivity and anticancer property as reflected by PASS prediction software. The dichloro Pt(II) complex [Pt(pic)Cl2], Pt-1, and its hydrolyzed diaqua complex [Pt(pic)(OH2)2]2+, Pt-2, were synthesized. The thiol-containing Pt(II) complexes [Pt(pic)(l-cys)]+, Pt-3, and [Pt(pic)(L-ac-l-cy)]+, Pt-4, were synthesized from Pt-2, which was obtained from hydrolysis of Pt-1. Their biomolecular interactions with BSA and DNA were executed by spectroscopic methods, and their cytototoxic property was tested by the MTT assay. In vitro biomolecular interactions of Pt(II) complexes with BSA and DNA were investigated by different spectroscopic and viscosity measurement methods for their pharmacokinetic and pharmacodynamic importance. The conformational change of BSA in the presence of a drug candidate was studied by Förster resonance energy transfer calculation and synchronous and three-dimensional fluorescence spectroscopic studies. A theoretical approach on optimization structures, highest occupied molecular orbital-lowest unoccupied molecular orbital energy, global reactivity parameters, time-dependent density functional theory, and molecular docking with BSA and DNA was executed to strengthen and support the experimental observations. In vitro cytotoxic profiles of the complexes like the anticancer activity and their level of reactive oxygen species production were brought under consideration on A549 cancer cells and the normal human embryonic kidney cell line HEK-293. The cytotoxic property was compared with that of the recognized anticancer drug cisplatin.

The role of collisional energy transfer in the thermal and prompt dissociation of 1-methyl allyl

Collisional energy transfer plays a pivotal role in a-priori calculations of the pressure-dependent rate constants obtained from a master equation. However, accurate determinations of collisional energy transfer parameters are rare and so most kinetic studies rely on best-fits of these parameters to experimental measurements (if available) or estimates guided from literature studies. In this work, we have quantified the effect of the uncertainty in energy transfer parameters on the thermal and prompt dissociation kinetics of a resonance stabilized radical, 1-methyl allyl (1MA), of relevance to the combustion of 1- and 2-butene isomers. Simulations using literature kinetics models were performed to assess the impact of these uncertainties on flame propagation and speciation data in laminar flames of 1- and 2-butene. Analyses of the uncertainty propagated by the energy transfer parameters for 1MA dissociation to the flame simulations, in particular the laminar flame speed, indicate an intricate coupling between the kinetics of 1MA dissociation (chain propagation) and its reaction with H-atoms (chain-termination). Ab-initio based theoretical calculations were also performed to obtain pressure-dependent kinetics for the reaction of 1MA with H-atoms. Lastly, theoretically calculated energy transfer parameters were used to best characterize the kinetics and branching between the chain propagating 1MA dissociation and the chain-terminating reaction 1MA + H.

(Invited) Photoabsorption and Excitation Energy Transfer in Fluorinated Non-Fullerene Acceptors for Organic Solar Cells

Recently, it was reported that OSCs based on non-fullerene acceptors have shown high photovoltaic performance with over 18% efficiency, being more than the power conversion efficiencies (PCEs) of 13% in OSCs based on fullerene. We considered theoretically the effects of fluorine atoms on the conversion efficiency of organic thin-film solar cells from the electronic analysis of donor/acceptor (D/A) complex interactions for NTz-Teh-FA and FNTz-Teh-FA using DFT. It was confirmed that it differs depending on the side-chain length, and it is necessary to consider the side-chain length. Because the longer the side-chain length, the lighter absorption and increased charge transfer. In the fluorinated acceptor, the polarity around the O atoms at both ends of the main chain was weakened, the twist angle of the molecular structure was reduced, and the light absorption at 600–700 nm was increased in the absorption spectrum. Therefore, it is considered that the fluorinated nonfullerene-type acceptor FNTz-Teh-FA, which has a long side chain, has the best light absorption and charge transfer. Excitation Energy Transfer (EET) calculations show that the Coulomb coupling contributes significantly. In addition, it was confirmed that the fluorinated complex had a higher EET. Therefore, it is considered that the charge separation efficiency is improved. Thus, it is considered that the short-circuit current density (JSC) is improved by improving the internal quantum efficiency (IQE), including the element of the charge separation efficiency.

Synthesis of SrSiO3:Tb3+, Eu3+, Li+ red phosphors for WLED and study of their luminescence properties

A series of Tb3+, Eu3+, Li+ co-doped SrSiO3 phosphors were prepared using the high-temperature solid-phase method. The X-ray diffraction results showed that Tb3+ and Eu3+ successfully entered into the SrSiO3 matrix lattice. Strong energy transfer from Tb3+ to Eu3+ is exhibited with a calculated energy transfer efficiency of 94.7%. Doping of the charge compensator Li+ increased the luminescence intensity of the SrSiO3:6%Tb3+, 6%Eu3+, 3%Li+ phosphor at a wavelength of 614 nm by 4.2 times and significantly improved the color purity of this phosphor (C p = 85.9%). Based on color coordinate analysis, the phosphor color coordinates are located near (0.615, 0.365), which belongs to the red region. The phosphor was integrated into a white LED. The resultant package exhibited a color temperature of 6479 K and a color rendering index of 93.8. Its luminous performance was also very stable under different drive currents.

Spectroscopic analysis of 2-(5-mercapto-1,3,4-oxadiazol-2-yl)-6-methylquinolin-4-ol binding to blood plasma albumin.

Binding of 2-(5-mercapto-1,3,4-oxadiazol-2-yl)-6-methylquinolin-4-ol (C1), a biologically active substance, to bovine blood plasma albumin (BSA) at 293, 298, and 303 K was studied using fluorescence (steady state, synchronous, excitation/emission matrix) and FT-IR spectroscopy methods. The experimental results showed that C1 causes fluorescence quenching of BSA through both static and dynamic quenching mechanisms. The thermodynamic parameters, enthalpy and entropy change, for the static quenching were calculated to be − 35.73 kJ mol−1 and − 35.34 J mol−1 K−1, which indicated that hydrogen bonding and van der Waals interactions were the predominant intermolecular forces regulating C1–BSA interactions. Distance between donor and acceptor (2.14, 2.26, and 2.30 nm) depending on the temperature, obtained from intrinsic Förster resonance energy transfer calculations, revealed the static quenching mechanism of BSA fluorescence in 0–3.0 × 10−5 mol/dm3 concentration range of C1. The micro-environmental and conformational changes in BSA structure, established by synchronous, excitation/emission matrices and FT-IR spectra showed the changes in the BSA secondary structure.Graphical abstract

Exploring the Role of Msh2‐Msh6 in Processing Holliday Junction DNA

Msh2‐Msh6 is a eukaryotic ATP‐dependent mismatch repair (MMR) protein that plays a key role in maintaining the fidelity of the genetic code. The protein recognizes and initiates repair for single base pair mismatches and short insertion deletion loops (IDL). Msh2‐Msh6 functions via a molecular switch mechanism, whereby ATP hydrolysis and ADP/ATP exchange facilitates the binding and release of the protein from the mismatch. Previous research has revealed that the protein binds G:T mismatch DNA with the highest affinity. Interestingly, in‐solution binding assays have revealed that Msh2‐Msh6 binds Holliday Junction DNA, a key recombination intermediate, with 1:1 stoichiometry and a similarly high affinity. However, the functional importance and structural details of this interaction are unclear. Thus far, X‐ray crystallography and Molecular Dynamics (MD) simulations are limited to the protein’s interactions with mismatch DNA only. To address the lack of structural information, we modeled the Msh2‐Msh6‐HJ interaction using the human Msh2‐Msh6 crystal structure in which we have docked in junction DNA instead of the mismatched DNA. The junction DNA used in all experiments and simulations is J3, a non‐migrating junction with 17 base pair long arms. These MD simulations will help refine the structural model and assess significant interactions between the protein and DNA. Furthermore, ATPase assays and equilibrium binding assays are used to elucidate the protein’s ATP hydrolysis activity and binding affinity in the presence of G:T mismatch DNA, J3 junction DNA, and J3 junction DNA containing a G:T mismatch. Preliminary experiments show that relative to the apoprotein’s basal ATPase activity, ATP hydrolysis is weakly stimulated when Msh2‐Msh6 is bound to G:T mismatch and J3. Gel mobility shift assays (GMSA) reveal binding affinities in the range of 9.1±2.6 nM to 23.5±11.8 nM for G:T mismatch, J3 junction, and mismatched J3 junction. These data illustrate that Msh2‐Msh6 not only binds G:T mismatch and J3 with similarly high affinity, but also that introducing a mismatch in J3 does not modulate the protein’s affinity for the junction. In addition, the GMSA data suggest that Msh2‐Msh6‐HJ binding may take on multiple conformations, consistent with previous Förster resonance energy transfer (FRET) calculations that show Msh2‐Msh6 opening the junction after binding.

Tryptophan capped gold-aryl nanoparticles for energy transfer study with SARS-CoV-2 spike proteins

ABSTRACT Current research on coronavirus 2 disease (SARS-CoV-2) has been focused on developing reliable gold nanomaterials and methods for the detection of viral spike protein (S-proteins). Here, we describe the fluorescence quenching of spike proteins in the presence of robust gold-aryl nanoparticles. The obtained results demonstrated a strong binding affinity between S-proteins and tryptophan immobilized on gold-carbon nanoparticles (Trp-AuNPs) based on the binding constant value of 11.098 M−1. Förster non-radiative energy transfer (FRET) calculations showed an average binding distance of r = 3.06 nm and a critical energy transfer distance of R0 = 2.5 nm. Time-resolved fluorescence studies of conjugated S-proteins onto Trp-AuNPs revealed a short fluorescence lifetime and dynamic quenching.

Superquadric DEM-SPH coupling method for interaction between non-spherical granular materials and fluids

The research on the coupling method of non-spherical granular materials and fluids aims to predict the particle–fluid interaction in this study. A coupling method based on superquadric elements is developed to describe the interaction between non-spherical solid particles and fluids. The discrete element method (DEM) and the smoothed particle hydrodynamics (SPH) are adopted to simulate granular materials and fluids. The repulsive force model is adopted to calculate the coupling force and then a contact detection method is established for the interaction between the superquadric element and the fluid particle. The contact detection method captures the shape of superquadric element and calculates the distance from the fluid particle to the surface of superquadric element. Simulation cases focusing on the coupling force model, energy transfer, and large-scale calculations have been implemented to verify the validity of the proposed coupling method. The coupling force model accurately represents the water entry process of a spherical solid particle, and reasonably reflects the difference of solid particles with different shapes. In the water entry process of multiple solid particles, the total energy of the water entry process of multiple solid particles tends to be stable. The collapse process of the partially submerged granular column is simulated and analyzed under different parameters. Therefore, this coupling method is suitable to simulate fluid–particle systems containing solid particles with multiple shapes.

Comparison between the results of a recently-developed biological weighting function (V79-RBE10 BWF) and the in vitro clonogenic survival RBE10 of other repair-competent asynchronized normoxic mammalian cell lines and ions not used for the development of the model

728 simulated microdosimetric lineal energy spectra (26 different ions between 1H and 238U, 28 energy points from 1 to 1000 MeV/n) were used in combination with a recently-developed biological weighting function (Parisi et al 2020 Phys. Med. Biol. 1361–6560) and 571 published in vitro clonogenic survival curves in order to: (1) assess prediction intervals for the in silico results by deriving an empirical indication of the experimental uncertainty from the dispersion in the in vitro hamster lung fibroblast (V79) data used for the development of the biophysical model; (2) explore the possibility of modeling the relative biological effectiveness (RBE) of the 10% clonogenic survival of asynchronized normoxic repair-competent mammalian cell lines other than the one used for the development of the model (V79); (3) investigate the predictive power of the model through a comparison between in silico results and in vitro data for 10 ions not used for the development of the model. At first, different strategies for the assessment of the in silico prediction intervals were compared. The possible sources of uncertainty responsible for the dispersion in the in vitro data were also shortly reviewed. Secondly, also because of the relevant scatter in the in vitro data, no statistically-relevant differences were found between the RBE10 of the investigated different asynchronized normoxic repair-competent mammalian cell lines. The only exception (Chinese Hamster peritoneal fibroblasts, B14FAF28), is likely due to the limited dataset (all in vitro ion data were extracted from a single publication), systematic differences in the linear energy transfer calculations for the employed very-heavy ions, and the use of reference photon survival curves extracted from a different publication. Finally, the in silico predictions for the 10 ions not used for the model development were in good agreement with the corresponding in vitro data.