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This study investigates how scattering foil materials and sampling holder placement affect electron energy distribution in electron beams from a modified medical linear accelerator for FLASH radiotherapy. We analyze electron energy spectra at various positions—ionization chamber, mirror, and jaw—to evaluate the impact of Cu, Pb-Cu, Pb, and Ta foils. Our findings show that close proximity to the source intensifies the dependence of electron energy distribution on foil material, enabling precise beam control through material selection. Monte Carlo simulations are effective for designing foils to achieve desired energy distributions. Moving the sampling holder farther from the source reduces foil material influence, promoting more uniform energy spreads, particularly in the 0.5–10 MeV range for 12 MeV electron beams. These insights emphasize the critical role of tailored material selection and sampling holder positioning in optimizing electron energy distribution and fluence intensity for FLASH radiotherapy research, benefiting both experimental design and clinical applications. [ABSTRACT FROM AUTHOR]

Definition: Flash radiotherapy (Flash-RT) is an innovative technique used in radiotherapy for cancer treatment because it delivers an extremely high dose of radiation (>40 Gy/s) to the tumour in a very short period of time, typically within a fraction of a second. This ultra-fast delivery of radiation distinguishes Flash-RT from conventional radiotherapy, which typically involves the delivery of radiation over a longer time period, often several minutes. Studies conducted in cell and preclinical models suggested that Flash-RT may spare normal tissues from radiation-related side effects, such as skin toxicity, gastrointestinal complications, and damage to organs-at-risk. This is believed to be due to the unique normal tissue response to the ultra-high dose rate. Nevertheless, while Flash-RT shows promising results in preclinical and early clinical studies, one should note that the technique is still in the early stages of development. This entry provides a comprehensive exploration of the immense potentials of Flash-RT, covering its background, mechanisms, radiation sources, recent experimental findings based on cell and preclinical models, and future prospects. It aims to provide valuable insights into this innovative radiotherapy technology for anyone interested in the subject. [ABSTRACT FROM AUTHOR]

We studied the optical properties of hybrid multilayer microspheres (HMMs). We prepared multilayer particles with alternating radial layers of gold nanoparticles (NPs) and poly(methyl methacrylate) and achieved control over particle size, the thickness of particle layers, and the surface coverage of gold NPs. We showed the ability to tune the spectral characteristics of the HMMs, which was based on frequency dispersion of the dielectric constant of polymer-metal NP structures. Good agreement between experimental and theoretical extinction properties of the HMMs was obtained. In comparison with multilayer structures synthesized solely from polymers, hybrid multilayer microspheres have a larger refractive layer contrast between adjacent layers, which is important for practical applications in optoelectronic devices. Key words: hybrid polymer-inorganic materials, polymer microspheres, gold nanoparticles, optical properties, extinction spectra. On a etudie les proprietes optiques de microspheres multicouches hybrides (MMH). On a prepare les particules a multicouches comportant des couches radiales alternantes de nanoparticules (NP) d'or et de poly(methacrylate de methyle) et on a pu controler la taille des particules des couches et la surface de la couverture des nanoparticules d'or. On a pu controler les caracteristiques spectrales des microspheres multicouches hybrides en ajustant la frequence de dispersion de la constante de dielectrique des structures des nanoparticules polymere-metal. On a obtenu un bon accord entre les proprietes d'extinction experiinentales et theoriques des microspheres multicouches hybrides. Par comparaison avec les structures multicouches synthetisees uniquement a partir de polymeres, les microspheres multicouches hybrides possedent un plus grand contraste de refraction par couche entre les couches, propriete importante pour les applications pratiques dans les appareils optoelectroniques. Mots-cles : materiaux hybrides polymere-inorganique, microspheres de polymere, nanoparticules d'or, proprietes optiques, spectres d'extinction. [Traduit par la Redaction] doi: 10.1139/V09-172, Introduction Polymer microspheres with a multilayer onion-like structure possess optical properties that are useful in photonic crystals, (1-2) optical data storage, (3-4) biometrics, (5,6) and, sensing and single-particle optical limiting. [...]

The relation between the various morphologies and optical properties of ZnSe nanostructures is investigated. Photoluminescence (PL) measurements on crystalline nanowires have shown that the spectrum comprises two characteristic peaks corresponding to strong near band emission and a weaker emission associated with defect states, but the PL spectra of ZnSe nanoribbons containing a high density of structural defects are dominated by defect related emission.

Research describing inductively coupled plasma etching is presented. In particular Indium Phoshide (InP)-based nanostructures are investigated for etching techniques using N2/H2 plasmas.

A new study provides a model for coherent island formation in heteroepitaxial thin films.

The clustering of chlorine chemisorbed on gallium arsenide(001)-c(8x2) surfaces was observed using scanning tunneling microscopy.

A quantum model that uses N two-level atoms within a photonic band-gap material and interacting with a single photon mode under suitable nonequilibrium boundary conditions has been developed. The solution of the eigenvalue problem of the Hamiltonian shows that the total system behaves like any two-level system with the eigenvectors existing in a dual pair of spaces. The interaction of the atoms with the single photon mode does not result in decoherence over the constructed quantum logic gates.

A study was conducted on a specific class of neural network models called quantum cellular neural networks. It employed a subdynamics formula for complex dynamic systems to investigate the eigen value problem of the Hamiltonian for a two-dimensional Ising model coupled with a local external field, regardless of whether the system is or is not in equilibrium state. A Jordan-type spectral decomposition for the hamiltonian operator and the evolution formula of the density operator are presented.

A subdynamics-based general formulation was derived for the construction of the spectral decomposition of the Hamiltonian for N excitons limited by a quantum dot with parabolic potential and mediated by an electromagnetic field. Using the formulation, the spectrum of the Hamiltonian of N excitons can be computed based on recurrence relations for the operators of creation and destruction. Then the spectral decomposition of the Hamiltonian of the system can be constructed using the intermediate operator and the intertwining relation.

GaAs-based semiconductors are useful for fabricating low-power, high-speed, high-frequency semiconductor devices and integrated circuits. However their performance is degraded by surface and interface states, and various passivation approaches are being developed. The role of O on GaAs surfaces during Ga(sub2)O(sub3) passivation has been studied, with particular focus on GaAs(100) Ga-terminated surfaces. Results showed that a reduction in surface-state density comes from the initial near-bridge-bonded O atoms.

The development of lateral interaction force is responsible for the multitude of surface reconstruction for GaAs(III) surfaces. This mechanism is proposed by studying two H3Ga3Ag3H6 and H6Ga3Ag3H3 models. The lateral force increases Ga-As-Ga band angle and reduces As-Ga-As band angle. This mechanism explains the absence of one-quarter of Ga atoms from Ga-terminated (III)A surfaces and the absence of a third of As atoms in As-terminated (III)B surfaces.

Capacitance measurements were made on an array of parallel ZnO nanowires embedded in a polymer matrix and provided with two electrodes perpendicular to the nanowires. The capacitance monotonically increased, and saturated at large negative (depleting) and large positive (accumulating) voltages. A qualitative explanation for this behavior is presented, taking into account specific features of quasi-one-dimensional screening. The increasing or decreasing character of the capacitance-voltage characteristics were determined by the conductivity type of the nanowires, which in our case was n-type. A dispersion of the experimental capacitance was observed over the entire frequency range of 1 kHz to 5MHz. This phenomenon is explained by the slow discharge of the nanowires through the thin dielectric layer that separates them from the top electrode. Separate measurements on individual identical nanowires in a field effect transistor configuration yielded an electron concentration and mobility of approximately 1017 cm-3 and 150 cm2/Vs, respectively, at room temperature. [ABSTRACT FROM AUTHOR]