Study to determine the induction of the bystander effect from Fe ion beam compared to X-rays in human keratinocytes

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005.Includes bibliographical references (leaves 62-65).The bystander effect is the observation that non-irradiated cells near a cell traversed by radiation express biological responses such as micronuclei formation and genomic instability. Most published studies of the bystander effect have been conducted using alpha particles, a high LET radiation. A few studies have been done with low LET radiation. This project studies the bystander effect from both low LET x-rays and high LET Fe particle beam irradiation. Using a transwell insert system, the bystander effect was studied in hTERT immortalized human keratinocytes. Cells are plated in a 6-well plate and in a companion permeable membrane insert. Cells in the 6-well plate are irradiated using conventional 250 kVp X-rays or 1000 MeV/nucleon Fe ion beam, LET of 151 keV/pm, from the NASA Space Radiation Laboratory at Brookhaven National Lab. After irradiation, inserts are immediately placed into the 6 well plate so that the irradiated and unirradiated cells are sharing medium but are not in contact. For both beams, frequency of micronuclei, chromatin bridges, and p21 wafl induction as well as cell cycle phase analysis were determined in both directly irradiated and bystander cells from 0.1 Gy to 5 Gy. From x-rays, a two-fold bystander effect at 24 h after irradiation with elevated p21' wafl induction and micronuclei was seen but in Fe ion irradiation, the p21 wafl bystander effect was delayed to 40-50 h after irradiation and no MN bystander effect was observed.(cont.) Cell cycle analysis showed a slight G2 arrest in keratinocytes 5 h after x-rays but a strong G2 arrest until 40-50 h was seen after Fe ion irradiation. Bystander keratinocytes co-cultured with directly irradiated human fibroblasts AGO 1522 cells showed a two-fold p21 wafl and MN bystander effect 24 h after x-rays, and a potential 2-fold MN bystander effect 50 h after Fe ions. Bystander AGO1522 cells co-cultured with directly irradiated keratinocytes showed a two-fold MN bystander effect 24 h after x-rays, but no MN bystander response was seen at any time points studied from Fe ions. Striking differences in the bystander response were shown from the two radiation types, but the reason remains to be clarified.by Vered Anzenberg.S.M

Mass Redistribution Causes the Structural Richness of Ion-Irradiated Surfaces

We show that the “sputter patterning” topographical instability is determined by the effects of ion impact-induced prompt atomic redistribution and that erosion—the consensus predominant cause—is essentially irrelevant. We use grazing incidence small angle x-ray scattering to measure in situ the damping of noise or its amplification into patterns via the linear dispersion relation. A model based on the effects of impact-induced redistribution of those atoms that are not sputtered away explains both the observed ultrasmoothening at low angles from normal incidence and the instability at higher angles.Engineering and Applied Science

Time-resolved measurements of nanoscale surface pattern formation kinetics in two dimensions on ion-irradiated Si

The nanoscale kinetics of surface topography evolution on silicon surfaces irradiated with 1 keV Ar+ ions is examined in both directions perpendicular and parallel to the projection of the ion beam on the surface. We use grazing incidence small angle x-ray scattering to measure in situ the evolution of surface morphology via the linear dispersion relation. We study the transition from surface ultra-smoothening at low angles of deviation from normal ion incidence to a pattern-forming instability at high incidence angles. A model based on the effects of impact-induced redistribution of those atoms that are not sputtered away explains both the observed ultra-smoothening at low angles from normal ion incidence and the instability at higher angles and accounts quantitatively for the measured two-dimensional dispersion relation and its dependence on incidence angle.Physic

Designing hollow nano gold golf balls.

Hollow/porous nanoparticles, including nanocarriers, nanoshells, and mesoporous materials have applications in catalysis, photonics, biosensing, and delivery of theranostic agents. Using a hierarchical template synthesis scheme, we have synthesized a nanocarrier mimicking a golf ball, consisting of (i) solid silica core with a pitted gold surface and (ii) a hollow/porous gold shell without silica. The template consisted of 100 nm polystyrene beads attached to a larger silica core. Selective gold plating of the core followed by removal of the polystyrene beads produced a golf ball-like nanostructure with 100 nm pits. Dissolution of the silica core produced a hollow/porous golf ball-like nanostructure

Technology engagement is associated with higher perceived physical well-being in stroke patients prescribed smartwatches for atrial fibrillation detection

BackgroundIncreasing ownership of smartphones among Americans provides an opportunity to use these technologies to manage medical conditions. We examine the influence of baseline smartwatch ownership on changes in self-reported anxiety, patient engagement, and health-related quality of life when prescribed smartwatch for AF detection.MethodWe performed a post-hoc secondary analysis of the Pulsewatch study (NCT03761394), a clinical trial in which 120 participants were randomized to receive a smartwatch-smartphone app dyad and ECG patch monitor compared to an ECG patch monitor alone to establish the accuracy of the smartwatch-smartphone app dyad for detection of AF. At baseline, 14 days, and 44 days, participants completed the Generalized Anxiety Disorder-7 survey, the Health Survey SF-12, and the Consumer Health Activation Index. Mixed-effects linear regression models using repeated measures with anxiety, patient activation, physical and mental health status as outcomes were used to examine their association with smartwatch ownership at baseline.ResultsNinety-six participants, primarily White with high income and tertiary education, were randomized to receive a study smartwatch-smartphone dyad. Twenty-four (25%) participants previously owned a smartwatch. Compared to those who did not previously own a smartwatch, smartwatch owners reported significant greater increase in their self-reported physical health (β = 5.07, P < 0.05), no differences in anxiety (β = 0.92, P = 0.33), mental health (β = −2.42, P = 0.16), or patient activation (β = 1.86, P = 0.54).ConclusionsParticipants who own a smartwatch at baseline reported a greater positive change in self-reported physical health, but not in anxiety, patient activation, or self-reported mental health over the study period

Linear energy transfer dependence of radiation-induced bystander effects using human prostate tumor cells

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008."June 2008."Includes bibliographical references (leaves 133-140).In the past fifteen years, evidence provided by many independent research groups have indicated higher numbers of cells exhibiting damage than expected based on the number of cells traversed by the radiation. This phenomenon has been coined as the "bystander effect". The purpose of this study was to characterize the ability of irradiated tumor cells to induce bystander effects in co-cultured cells. Human DU-145 prostate carcinoma cells were grown on a 1.4 [mu]m-thick mylar membrane in specially constructed cell culture dishes for irradiation with alpha particles (average energy 3.14 MeV) from a 241Am source, or in 6-well plates for irradiation with 250 kVp x-rays at 25°C. In parallel experiments, the tumor cells were incubated at 4°C for one hour prior to irradiation and irradiated on ice to test the nature of the bystander signal. Bystander cells were placed into the medium above the irradiated DU-145 and were co-incubated for a length of time. The bystander effect endpoints measured in either DU-145 tumor cells or in normal primary AGO1522 fibroblasts were micronucleus (MN) formation, [gamma]-H2AX double strand break repair foci, and survival fraction. A 1.5-2.0-fold increase in MN formation was observed in both DU-145 and AG01522 bystander cells after either alpha particle or xray irradiation of the DU-145 target cells. A 1.5-fold [gamma]-H2AX bystander increase and a survival fraction reduction to 80% were only detected in AGO1522 cells, and only after xray irradiation of target DU-145 cells. Alpha particle irradiation of the target DU-145 cells produced neither [gamma]-H2AX foci nor survival fraction bystander effect in either cell line. Lowering the temperature to 4°C during the irradiation of the DU-145 tumor cells, with either x-rays or alpha particles, eliminated both the MN formation and the decreased survival fraction bystander effects in the co-cultured AG01522 fibroblasts.(cont.) This study demonstrates that biochemical processes in the directly-irradiated tumor cells are required for initiation of the signaling process. Low temperature during the irradiation inhibited the initiation of a bystander signal. There are also LET-dependent differences in the signal released from DU-145 human prostate carcinoma cells; and that, for some endpoints, bystander AG01522 fibroblasts and bystander DU-145 prostate carcinoma cells respond differently to the same, medium-mediated signal.by Vered Anzenberg.Ph.D

Nanoscale surface structuring during ion bombardment of elemental semiconductors

Thesis (Ph.D.)--Boston University PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at [email protected]. Thank you.Nano-patterning of surfaces with uniform ion bombardment yields a rich phase-space of topographic patterns. Particle irradiation can cause surface ultra-smoothing or selforganized nanoscale pattern formation in surface topography. Topographic pattern formation has previously been attributed to the effects of the removal of target atoms by sputter erosion. In this thesis, the surface morphology evolution of Si(100) and Ge(100) during low energy ion bombardment of Ar+ and Kr+ ions, respectively, is studied. Our facilities for studies of surface processes at the National Synchrotron Light Source (NSLS) allow in-situ characterization of surface morphology evolution during ion bombardment using grazing incidence small angle x-ray scattering (GISAXS). This technique is used to measure in reciprocal space the kinetics of formation or decay of correlated nanostructures on the surface, effectively measuring the height-height correlations. A linear model is used to characterize the early time kinetic behavior during ion bombardment as a function of ion beam incidence angle. The curvature coefficients predicted by the widely used erosive model of Bradley and Harper are quantitatively negligible and of the wrong sign when compared to the observed effect in both Si and Ge. A mass-redistribution model explains the observed ultra-smoothing at low angles, exhibits an instability at higher angles, and predicts the observed 45° critical angle separating these two regimes in Si. The Ge surface evolution during Kr+ irradiation is qualitatively similar to that observed for Ar+ irradiation of Si at the same ion energy. However, the critical angle for Ge cannot be quantitatively reproduced by the simple mass redistribution model. Crater function theory, as developed by Norris et al., incorporates both mass redistributive and erosive effects, and predicts constraining relationships between curvature coefficients. These constraints are compared to experimental data of both Si and Ge. There is good agreement at low incidence angles; however, at higher angles the data disagrees with the predictions of the crater function formalism. This calls into question the ability of crater function theory to model the surface morphology evolution during ion bombardment