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Amanda M Shing, Yulia Tolstova, Nathan S Lewis, Harry A Atwater
ZnSnxGe1-xN2 alloys are chemically miscible semiconductor compounds with potential application as earth-abundant alternatives to InxGa1-xN. Preparation of ZnSnxGe1-xN2 thin-films by reactive RF sputter deposition yield low-mobility, nanocrystalline films. In contrast, the growth of ZnSnxGe1-xN2 films by molecular-beam epitaxy (MBE) on c-plane sapphire and GaN templates is described herein. Epitaxial films exhibited 3D growth on sapphire and 2D single-crystal quality on GaN, exhibiting substantial improvements in epitaxy and crystallinity relative to nanocrystalline sputtered films...
September 20, 2017: Scientific Reports
G Calabrese, S V Pettersen, C Pfüller, M Ramsteiner, J K Grepstad, O Brandt, L Geelhaar, S Fernández-Garrido
We report on plasma-assisted molecular beam epitaxial growth of almost randomly oriented, uniformly tilted, and vertically aligned self-assembled GaN nanowires (NWs), respectively, on different types of polycrystalline Ti foils. The NW orientation with respect to the substrate normal, which is affected by an in situ treatment of the foil surface before NW growth, depends on the crystallinity of the native oxide. Direct growth on the as-received foils results in the formation of ensembles of nearly randomly oriented NWs due to the strong roughening of the surface induced by chemical reactions between the impinging elements and Ti...
September 20, 2017: Nanotechnology
Wouter Crijns, Dirk Adelin Vandenbroucke, Paul Leblans, Tom Depuydt
Purpose Optical stimulated luminescence (OSL) combines reusability, sub-mm resolution, and a linear dose response in a single radiation detection technology. Such a combination is currently lacking in radiotherapy dosimetry. But OSL-films have a strong energy dependent response to keV photons due to a relative high effective atomic number (Zeff). The current work studied the applicability of a 2D OSL-film with a reduced Zeff as (IMRT/VMAT) dosimeter. Methods and Materials Based on their commercial OSL-film experience, Agfa Healthcare N...
September 20, 2017: Physics in Medicine and Biology
Jeffrey R Vieregg, Steven J Martin, Adam P Breeland, Christopher M Weikart, Matthew V Tirrell
For many years, glass has been the default material for parenteral packaging, but the development of advanced plastics such as cyclic olefin polymers (COP) and the rapidly increasing importance of biologic drugs have provided new choices, as well as more stringent performance requirements. In particular, many biologics must be stored at non-neutral pH, where glass is susceptible to hydrolysis, metal extraction, and delamination. Plastic containers are not susceptible to these problems, but suffer from higher gas permeability and a propensity for sterilization-induced radical generation, heightening the risk of oxidative damage to sensitive drugs...
September 19, 2017: PDA Journal of Pharmaceutical Science and Technology
Meng-Meng Xiao, Chenguang Qiu, Zhiyong Zhang, Lianmao Peng
Direct growth of ultra-thin gate dielectric layer with high uniformity and high quality on graphene remains a challenge for developing graphene-based transistors due to the chemical inert surface properties of graphene. Here we develop a method to realize atomic-layer-deposition (ALD) growth of ultra-thin high-k dielectric layer on graphene through pre-modified graphene surface using electron beam irradiation. An amorphous carbon layer induced by electron beam scanning is formed on graphene, and then acts as seed for ALD growth of high-k dielectrics...
September 13, 2017: ACS Applied Materials & Interfaces
G Reggiori, A Stravato, P Mancosu, F Lobefalo, L Paganini, F Zucconi, V Palumbo, A Gaudino, M Scorsetti, S Tomatis
INTRODUCTION: Nanochambers present some advantages in terms of energy independence and absolute dose measurement for small field dosimetry in the SBRT scenario. Characterization of a micro-chamber prototype was carried out both under flattened and flattening-filter-free (FFF) beams with particular focus on stem effect. METHODS: The study included characterization of leakage and stem effects, dose rate and dose per pulse dependence, measurement of profiles, and percentage depth doses (PDDs)...
September 9, 2017: Physica Medica: PM
Duming Zhang, Jeonghoon Ha, Hongwoo Baek, Yang-Hao Chan, Fabian D Natterer, Alline F Myers, Joshua D Schumacher, William G Cullen, Albert V Davydov, Young Kuk, M Y Chou, Nikolai B Zhitenev, Joseph A Stroscio
We report a rectangular charge density wave (CDW) phase in strained 1T-VSe2 thin films synthesized by molecular beam epitaxy on c-sapphire substrates. The observed CDW structure exhibits an unconventional rectangular 4a×√3a periodicity, as opposed to the previously reported hexagonal 4a×4a structure in bulk crystals and exfoliated thin layered samples. Tunneling spectroscopy shows a strong modulation of the local density of states of the same 4a×√3a CDW periodicity and an energy gap of 2ΔCDW = (9.1 ± 0...
July 2017: Phys Rev Mater
A V Steele, A Schwarzkopf, J J McClelland, B Knuffman
We present measurements of focal spot size and brightness in a focused ion beam system utilizing a laser-cooled atomic beam source of Cs ions. Spot sizes as small as (2.1 ± 0.2) nm (one standard deviation) and reduced brightness values as high as (2.4 ± 0.1) × 10(7) A m(-2) Sr(-1) eV(-1) are observed with a 10 keV beam. This measured brightness is over 24 times higher than the highest brightness observed in a Ga liquid metal ion source. The behavior of brightness as a function of beam current and the dependence of effective source temperature on ionization energy are examined...
June 2017: Nano Futures
Pamela J Boimel, Abigail T Berman, Jonathan Li, Smith Apisarnthanarax, Stefan Both, Kristi Lelionis, Gary L Larson, Ursina Teitelbaum, John N Lukens, Edgar Ben-Josef, James M Metz, John P Plastaras
BACKGROUND: Local recurrence following definitive treatment for pancreatic adenocarcinoma is common and can be associated with significant morbidity and mortality. Retreatment options for these patients are limited. Proton beam reirradiation (PRT) may limit dose and toxicity to previously irradiated normal tissues in patients without evidence of metastatic disease. METHODS: Between 8/2010-2/2015, 15 patients with isolated, locally-recurrent pancreatic cancer were treated with PRT...
August 2017: Journal of Gastrointestinal Oncology
T P O'Leary, A Robertson, P H Chipman, V F Rafuse, R E Brown
Motor problems occur early in some patients with Alzheimer's disease (AD) and as the disease progresses many patients develop motor dysfunction. Motor dysfunction has been reported in some mouse models of AD, including the 5xFAD mouse, thus this model may be particularly useful for studying motor dysfunction in AD. In order to determine the extent of motor dysfunction in these mice, we tested 11-13 month old female 5xFAD and wildtype (WT) control mice in a battery of motor behaviour tasks. The 5xFAD mice showed hind limb clasping, weighed less and had slower righting reflexes than WT mice...
September 7, 2017: Behavioural Brain Research
Anna Varghese, A Devi, Paul V George, Roshan Samuel Livingstone
The purpose of the study was to measure radiation doses and estimate risk from various beam projections in children undergoing cardiac interventions. The dose area product (DAP) was measured for 11 patent ductus arteriosus device closure, PDA; 4 atrial septal defect device closure, ASD and 3 balloon pulmonary valvuloplasty, BPV interventions performed using flat detector system. Total mean DAP for PDA, ASD and BPV were 1.9 Gycm2, 9.8 Gycm2 and 6.2 Gycm2 respectively. The fluoroscopic kerma dose rates increased by 10%, 33% and 92% when changing projection from posterior-anterior to lateral projection for PDA interventions among infants, <5yrs and > 5yrs respectively...
September 8, 2017: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
H Ahmed, S Kar, G Cantono, P Hadjisolomou, A Poye, D Gwynne, C L S Lewis, A Macchi, K Naughton, G Nersisyan, V Tikhonchuk, O Willi, M Borghesi
The characteristics of laser driven proton beams can be efficiently controlled and optimised by employing a recently developed helical coil technique, which exploits the transient self-charging of solid targets irradiated by intense laser pulses. Here we demonstrate a well collimated (<1° divergence) and narrow bandwidth (~10% energy spread) proton beamlet of ~10(7) particles at 10 ± 0.5 MeV obtained by irradiating helical coil targets with a few joules, sub-ps laser pulses at an intensity of ~2 × 10(19) W cm(-2)...
September 7, 2017: Scientific Reports
A Schiavi, M Senzacqua, S Pioli, A Mairani, G Magro, S Molinelli, M Ciocca, G Battistoni, V Patera
Ion beam therapy is a rapidly growing technique for tumor radiation therapy. Ions allow for a high dose deposition in the tumor region, while sparing the surrounding healthy tissue. For this reason, the highest possible accuracy in the calculation of dose and its spatial distribution is required in treatment planning. On one hand, commonly used treatment planning software solutions adopt a simplified beam-body interaction model by remapping pre-calculated dose distributions into a 3D water-equivalent representation of the patient morphology...
September 5, 2017: Physics in Medicine and Biology
Giuliano Angella, Giuseppe Barbieri, Riccardo Donnini, Roberto Montanari, Maria Richetta, Alessandra Varone
Electron Beam (EB) welding has been used to realize seams on 2 mm-thick plates of directionally solidified (DS) IN792 superalloy. The first part of this work evidenced the importance of pre-heating the workpiece to avoid the formation of long cracks in the seam. The comparison of different pre-heating temperatures (PHT) and pass speeds (v) allowed the identification of optimal process parameters, namely PHT = 300 °C and v = 2.5 m/min. The microstructural features of the melted zone (MZ); the heat affected zone (HAZ), and base material (BM) were investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), electron back-scattered diffraction (EBSD), X-ray diffraction (XRD), and micro-hardness tests...
September 5, 2017: Materials
O L Ermolaeva, N S Gusev, E V Skorohodov, Yu V Petrov, M V Sapozhnikov, V L Mironov
We present the results of magnetic force microscopy investigations of domain structures in multilayer [Co (0.5 nm)/Pt (1 nm)]₅ thin film structures (denoted hereafter as Co/Pt) modified by additional Co capping layers and by ion irradiation. It is demonstrated that a Co capping layer essentially changes the domain structure and decreases the threshold of magnetization reversal, due to the formation of noncollinear magnetization in Co/Pt. It is shown that local irradiation with a focused He⁺ ion beam enables the formation of regions with decreased easy-axis anisotropy (magnetic bubbles) that have the inverse magnetization direction in the demagnetized state of Co/Pt...
September 5, 2017: Materials
George R Deeb, Riley K Allen, V Patrick Hall, Daniel Whitley, Daniel M Laskin, Sompop Bencharit
PURPOSE: The use of tooth-supported static stereolithographic guides has greatly improved the ability to ideally place implants. This study was designed to determine the accuracy of in office-printed implant surgical guides. MATERIALS AND METHODS: Using 3shape Implant Studio, a treatment plan for implant placement for tooth 8 was developed using a digital intraoral scan from a Trios scanner and cone-beam computed tomography. Ten stereolithographic guides were printed using a Form2 3-dimensional printer...
August 5, 2017: Journal of Oral and Maxillofacial Surgery
Rajnish Kumar, Dharmraj V Ghodke, Vinod K Senecha
A cold cathode arc discharge filament based multicusp H(-) ion source (HNIS) has been developed using an innovative low power igniter system working in a glow discharge regime to achieve a longer lifetime of the filament. This HNIS is cesium-free and its experimental prototype generates a maximum H(-) ion beam (HNIB) current of 12 mA at 50 keV beam energy in pulse mode with a peak arc power of 27 kW using the triode extraction system. This article presents the results of initial commissioning of the HNIS and steering magnetic field used to separate out the co-extracted electrons from HNIB, verified through experiments and 3-D ion beam simulations...
August 2017: Review of Scientific Instruments
Hyung Taek Kim, V B Pathak, Ki Hong Pae, A Lifschitz, F Sylla, Jung Hun Shin, C Hojbota, Seong Ku Lee, Jae Hee Sung, Hwang Woon Lee, E Guillaume, C Thaury, Kazuhisa Nakajima, J Vieira, L O Silva, V Malka, Chang Hee Nam
The achievable energy and the stability of accelerated electron beams have been the most critical issues in laser wakefield acceleration. As laser propagation, plasma wave formation and electron acceleration are highly nonlinear processes, the laser wakefield acceleration (LWFA) is extremely sensitive to initial experimental conditions. We propose a simple and elegant waveform control method for the LWFA process to enhance the performance of a laser electron accelerator by applying a fully optical and programmable technique to control the chirp of PW laser pulses...
August 31, 2017: Scientific Reports
Estiak Ahmad, Md Rezaul Karim, Shihab Bin Hafiz, C Lewis Reynolds, Yang Liu, Shanthi Iyer
Self-catalyzed growth of axial GaAs1-xSbx nanowire (NW) arrays with bandgap tuning corresponding to the telecommunication wavelength of 1.3 µm poses a challenge, as the growth mechanism for axial configuration is primarily thermodynamically driven by the vapor-liquid-solid growth process. A systematic study carried out on the effects of group V/III beam equivalent (BEP) ratios and substrate temperature (Tsub) on the chemical composition in NWs and NW density revealed the efficacy of a two-step growth temperature sequence (initiating the growth at relatively higher Tsub = 620 °C and then continuing the growth at lower Tsub) as a promising approach for obtaining high-density NWs at higher Sb compositions...
August 31, 2017: Scientific Reports
J Mraček, J Mork, T Svoboda, J Ferda, V Přibáň
BACKGROUND: Radiation necrosis in eloquent areas of the central nervous system (CNS) is one of the most serious forms of toxicity from radiation therapy. The occurrence of radiation necrosis in the CNS is described in a wide range of 3 months to 13 years after radiation therapy. The incidence of this complication covers a wide range of 3-47%. The potential advantage of proton therapy is the ability to reduce dose to normal tissue and escalate tumor dose. Proton beams enter and pass through the tissue with minimal dose deposition until they reach the end of their paths, where the peak of dose, known as the Bragg peak, occurs...
2017: Klinická Onkologie: Casopis Ceské a Slovenské Onkologické Spolecnosti
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