Keran O'Brien

Dose rate determination for 125I seeds.

Dose rates in water have been determined for the two types of 125I seed currently used in brachytherapy. The need for such determinations became evident when water/air ratios measured with a silicon diode were found to be lower than expected. Extensive measurements using lithium fluoride thermoluminescent dosimeters (TLDs) have been performed in a solid water phantom, at distances from 0.1 to 10 cm from the seed center and at angular increments of 10 degrees, 15 degrees, or 30 degrees within a plane through the seed axis. Dose calibration of the TLDs was accomplished by irradiation in air with 125I seeds of the same type and of strengths traceable to a calibration at the National Institute of Standards and Technology (NIST). Relative calibration of TLDs was monitored by irradiation, in an oven-type x-ray machine, of control dosimeters simultaneously and all dosimeters intercurrently with the 125I irradiations. Values obtained for the dose rate constant, i.e., dose rate per unit air-kerma strength at 1 cm on the transverse axis, were 0.853 and 0.932 cGy h-1 U-1 (1.08 and 1.18 cGy h-1 mCi-1) for the 6711 and 6702 seeds, respectively. Measured data were supplemented with Monte Carlo-calculated relative dose rate data generated using the MORSE code. These calculations used 100 energy groups from 10 to 35.4 keV and involved energy collection bins ranging from 0.025 to 1.2 cm on an edge. Normalized at 1 cm, transverse axis calculated data are not significantly different from measured data (ours or cited literature) at distances either less than 2.5 or greater than 8 cm. Normalized at different distances along the transverse axis, our off-axis calculated and measured distributions agree closely at all angles but differ from literature measured distributions at small (less than or equal to 1 cm) distances and, for small angles, increasingly at larger distances (greater than or equal to 5 cm).

Dosimetry for 125I seed (model 6711) in eye plaques

The effect of eye plaque materials (gold backing and silastic seed-carrier insert) on the dose distribution around a single 125I seed has been measured, using cubic lithium fluoride thermoluminescent dosimeters (TLDs) 1 mm on an edge, in a solid water eye phantom embedded in a solid water head phantom. With an 125I seed (model 6711) positioned in the center slot of the silastic insert for a 20-mm plaque of the design used in the collaborative ocular melanoma study (COMS), dose was measured at 2-mm intervals along the plaque central axis (the seeds transverse axis) and at various off-axis points, both with and without the COMS gold backing placed over the insert. Monte Carlo calculations (MORSE code) were performed, as well, for these configurations and closely the same geometry but assuming a large natural water phantom. Additional Monte Carlo calculations treated the case, both for 20- and 12-mm gold plaques, where the silastic insert is replaced by natural water. Relative to previous measurements taken in homogeneous medium of the same material (without the eye plaque), the dose reduction found by both Monte Carlo and TLD methods was greater at points farther from the seed along the central axis and, for a given central-axis depth, at larger off-axis distances. Removal of the gold backing from the plaque did not make measurable difference in the dose reduction results (10% at 1 cm).

LABORATORY STUDIES ON THE IRRADIATION OF SOLID ETHANE ANALOG ICES AND IMPLICATIONS TO TITAN'S CHEMISTRY

Pure ethane ices (C2H6) were irradiated at 10, 30, and 50 K under contamination-free, ultrahigh vacuum conditions with energetic electrons generated in the track of galactic cosmic-ray (GCR) particles to simulate the interaction of GCRs with ethane ices in the outer solar system. The chemical processing of the samples was monitored by a Fourier transform infrared spectrometer and a quadrupole mass spectrometer during the irradiation phase and subsequent warm-up phases on line and in situ in order to extract qualitative (products) and quantitative (rate constants and yields) information on the newly synthesized molecules. Six hydrocarbons, methane (CH4), acetylene (C2H2), ethylene (C2H4), and the ethyl radical (C2H5), together with n-butane (C4H10) and butene (C4H8), were found to form at the radiation dose reaching 1.4 eV per molecule. The column densities of these species were quantified in the irradiated ices at each temperature, permitting us to elucidate the temperature and phase-dependent production rates of individual molecules. A kinetic reaction scheme was developed to fit column densities of those species produced during irradiation of amorphous/crystalline ethane held at 10, 30, or 50 K. In general, the yield of the newly formed molecules dropped consistently for all species as the temperature was raised from 10 K to 50 K. Second, the yield in the amorphous samples was found to be systematically higher than in the crystalline samples at constant temperature. A closer look at the branching ratios indicates that ethane decomposes predominantly to ethylene and molecular hydrogen, which may compete with the formation ofn-butane inside the ethane matrix. Among the higher molecular products, n-butane dominates. Of particular relevance to the atmosphere of Saturn’s moon Titan is the radiation-induced methane production from ethane—an alternative source of replenishing methane into the atmosphere. Finally, we discuss to what extent the n-butane could be the source of “higher organics” on Titan’s surface thus resembling a crucial sink of condensed ethane molecules.

Monte Carlo dosimetry for 125I and 60Co in eye plaque therapy

Monte Carlo calculations of radiation dosimetry using MORSE code are performed for 125I and 60Co point sources in a cylindrical head phantom that simulates the geometry of eye plaque therapy for choroidal melanoma. We obtain the dose variation in the eye at submillimeter intervals over distances as close as 1 mm and up to 2.5 cm from the source. The calculations for 125I are performed for the phantom media of water, protein, and a homogenized protein-water mixture simulating the composition of the eye. Relative dose functions for 125I for these phantom media are fitted to second-degree polynomials. Agreement is found with published results. The relative dose function for 60Co at eye position in the water head phantom is fitted to a third-degree polynomial and compared with that for 60Co at the center of a large water sphere. A boundary effect due to the head phantom-air interface on the dose distribution for 60Co is demonstrated. The dose falloff with distance is faster for the eye geometry compared with the bulk geometry. We also show that the relative dose distributions within the tumor are comparable for 125I and 60Co by comparing their relative dose functions. This result is consistent with the success of clinical trials of large melanoma treatments with 125I plaques.

Comparison of codes assessing galactic cosmic radiation exposure of aircraft crew

The assessment of the exposure to cosmic radiation onboard aircraft is one of the preoccupations of bodies responsible for radiation protection. Cosmic particle flux is significantly higher onboard aircraft than at ground level and its intensity depends on the solar activity. The dose is usually estimated using codes validated by the experimental data. In this paper, a comparison of various codes is presented, some of them are used routinely, to assess the dose received by the aircraft crew caused by the galactic cosmic radiation. Results are provided for periods close to solar maximum and minimum and for selected flights covering major commercial routes in the world. The overall agreement between the codes, particularly for those routinely used for aircraft crew dosimetry, was better than +/-20 % from the median in all but two cases. The agreement within the codes is considered to be fully satisfactory for radiation protection purposes.

Limitations of the Use of the Vertical Cut-off to Calculate Cosmic-ray Propagation in the Earth's Atmosphere

In the second sentence of page 259, which says ‘However, this will “underestimate” the cosmic-ray flux entering the atmosphere.’ the word ‘underestimate’ should be ‘overestimate’. Also, in the next to last sentence on page 260, which says ‘The use of the vertical cut-off alone over the entire 2-solid angle of incidence of the primary cosmic radiation will “underestimate” the incident cosmic-ray flux, with the “underestimate” largest at the geomagnetic equator’, again ‘underestimate’ should be ‘overestimate’.

IASON-FREE: theory and experimental comparisons

A sophisticated flight code named FREE (acronym for Flight Route Effective Dose Estimation) was built for professional commercial usage. During its creation special precautions have been taken to take correctly into account all existing dependencies and details, so that the best possible result is achieved. Some of these factors are presented in detail and their effect on doses or dose rates is estimated. Detailed comparisons to more recent measurements for both quiescent as well as disturbed conditions are presented. The agreement at undisturbed conditions turns out to be excellent and also the comparisons to measured transient effects are very satisfactory.

A photochemical model of the dust-loaded ionosphere of Mars

The ionization of the lower Martian atmosphere and the presence of charged species are fundamental in the understanding of atmospheric electricity phenomena, such as electric discharges, large scale electric currents and Schumann resonances. The present photochemical model of the lower ionosphere of Mars (0–70 km) is developed to compute the concentration of the most abundant charged species (cluster-ions, electrons and charged aerosols) and electric conductivity, at the landing site and epoch of the ExoMars 2016 mission. The main sources of ionization are galactic cosmic rays (during daytime as well as nighttime) and photoionization of aerosols due to solar UV radiation during daytime. Ion and electron attachment to aerosols is another major source of aerosol charging. The steady state concentration of charged species is computed by solving their respective balance equations (also known as continuity equations), which include the source and sink terms of their photochemical reactions. Since the amount of suspended dust can vary considerably and it has an important effect on atmospheric properties, several dust scenarios, in addition to the day-night variations, are considered to characterize the variability of the concentration of charged species. It has been found that, during daytime, aerosols tend to become positively charged due to electron photoemission, and during nighttime, tend to charge negatively due to electron attachment. The most dominant day-night variability in ion and electron concentration occurs when the amount of suspended dust is the largest. The electric conductivity has been found to vary in the 10 −13 –10 −7 S/m range, depending on the altitude, dust scenario and local time.

Cosmic Rays In The Solar System

Calculations of cosmic‐ray propagation through the heliosphere, in the terrestrial atmosphere using a combination of a modified version of the adjoint Monte Carlo code, ATROPOS, and a suitably modified version of the deterministic transport code, PLOTINUS. ATROPOS solves the Parker heliospheric transport code in one and two dimensions in a 3‐dimensional heliosphere and provides cosmic‐ray spectra to be used by PLOTINUS to determine the radiation effects of interest. Other cosmic‐ray properties, such as the deceleration time (related to the so‐called deceleration potential) and the angular distribution of cosmic rays at earth orbit will also be described.

Cosmic-ray generation, propagation and atmospheric effects

C rays, produced by high-energy extra-solar events, ionize the earth’s atmosphere. Ionized aerosol particles can combine and form “seed” particles for cloud formation. In addition, cosmic-ray ionization increases the atmospheric conductivity. Variations of these quantities would be expected to have an effect on climate, and they do vary. The solar corona has a temperature of one million degrees and is continually “boiling off,” producing “the solar wind.” The solar wind is plasma that fills the solar system to a distance of about 90 times the earth-sun distance. The cosmic rays that fill the galaxy must do work against the solar wind to reach the earth’s orbit and hence lose intensity. The work done is measured in hundreds of megavolts. The intensity of the solar wind, and hence the intensity of cosmic-rays at earth orbit varies irregularly over an approximately 11-year cycle and sometimes, falls to deep minima. The 17th century “Maunder Minimum,” when solar modulation, the energy necessary to reach earth orbit, fell nearly to zero, was accompanied by what has been known as the “Little Ice Age,” causing much hardship in Europe. This is evidence that changes in cosmic-rays intensity can be associated with an impact on climate. Another important climatological consideration due to cosmic-ray impacts on the terrestrial atmosphere is the production of 1.5 million-year Be-10 by the spallation process. Radioactive Be-10 is used to date sections of Greenland and Antarctic ice cores to analyze past climates. Calculations of these quantities from basic principles are presented.Floods are becoming increasingly common in Nepal resulting in a huge loss of life and damage to settlements, agriculture land and infrastructures in various parts of the country. Most recent research findings suggest that climate change has accelerated the intensity and frequency of flood hazards in most parts of the country. Communities are however, making use of options that increase their preparedness for these flood hazards. The random sampling (for household survey), focus group discussion, key informant interviews and field observations were employed for data collection. Based on field data, this paper intends to assess the indigenous knowledge on flood forecasting and flood management practices at the community level those are being in practiced in the plain region of West Rapti River Basin of Nepal and its relevance under climate change induced flood disaster. The research findings indicate that there are some very effective local flood forecasting practices such as identifying the position of clouds; monitoring the extent of rainfall in upper catchments; analyzing the mobility of ants; analyzing the magnitude of thunderstorms and wind blows; analyzing the magnitude of hotness; and hearing strange sounds from river/torrents. Synthesis and analysis of these indicators helps communities to prepare for potential flood events. These include preparation of search and rescue related materials; the creation of small drainage structures in each plot of land and storage of the valuable material at a safer location; and being psychologically prepared for floods. This paper argues that these indigenous flood forecasting and management practices could be particularly useful for migrants, who are in flood prone areas but are not familiar with those practices.T of past earth system states are preserved in an array of biogeochemical archives. Extracting information from these archives produces valuable data that reveal time progression of environmental conditions. Covarying measurements entice cause-effect explanations, but establishing causal relationships from observational studies requires a rigorous epistemology. Correlation is necessary for hypothesizing a causal relationship, but insufficient for forming conclusions. Common-cause explanations, such as independent orbital forcing of correlated measurements, must be rejected based on characteristics of the data. Determining amplitude and phase response over a range of frequencies provides a test of cause-effect scenarios: measured cause must precede proportionate effect in a manner consistent with direct forcing theory. Amplitude and phase persistence (coherence) through time provides a method for quantifying probabilistic confidence in a cause-effect conclusion. In this presentation, methods are described, and then applied to ice core proxies for air temperature and atmospheric carbon dioxide concentration.T ‘100ky problem’ (1ky=1000 years) of the astronomical theory of the ice ages questions how the almost negligible ~100ky eccentricity forcing could power the ten massive glaciations of the last million years while the stronger ~400ky eccentricity forcing is nearly absent from the proxy records. Further, the astronomical theory does not explain how, without change in forcing, climatic oscillations switched from 41ky to 100ky at the mid-Pleistocene transition (MPT) 1.2 million years ago (1.2 Ma), or what caused the strong climatic response at the marine isotope stage (MIS) 11, the presence of power at frequencies absent in the external forcing, or the timing of glacial terminations. To resolve these inconsistencies many explanations have been put forward, from internal climatic oscillations without external forcing to external forcing other than the Milankovitch cycles, but the ultimate cause(s) remain elusive. I will introduce a unifying explanation that resolves all the above inconsistencies through a single process: nonlinear synchronization of the climate system’s internal oscillations to the eccentricity forcing. Synchronization is a fundamental nonlinear phenomenon and one basic mechanism of self-organization in complex system. The evidence suggests that after at least four million years of slow evolution, the climate system first synchronized to eccentricity at ~1.2Ma and has remained synchronized ever since. Synchronization powered the late Pleistocene glaciations, forced the frequency switch at the MPT, and caused the strong short-lived response at the MIS11 (~400ka).The study was conducted in July 2011 to June 2012 at the Isabela State University watershed experimental. Primary goal is to evaluate the performance and adaptability of the Water Erosion Prediction Project (WEPP) model in estimating the rate of soil erosion and run-off under upland rice cultivation. The research involves establishment of automatic weather station, small farm reservoir and erosion plots with three conservation management as treatments. Analysis was undertaken to characterize rainfall events in terms of amount, intensity, duration and frequency in relation to erosion data. Comparison of actual and simulated data and sensitivity analysis of scenarios for different types of rainfall, slope, and conservation practices were made. Validation result demonstrated statistical acceptability of the WEPP model. Actual and simulated data indicated that 50% soil loss is reduced when contour planting with hedgerow are practiced. The rate of sedimentation is linearly affected by increasing slopes and length, such that, the rate of soil removal ranges 1.2 t/ha to 48.46 t/ha across treatments at 10%-50% slope and 10 m-40 m slope length. The model can be use to develop decision support tools for conservation, optimization and utilization of farm resources in agricultural watershed units to improved productivity of upland areas in sustainable way.E though anomalous behaviors of liquid water around 4oC have long been studied by many different authors up to now, it is not still cleared what thermodynamic mechanisms induce them. The thermodynamic properties of substances are determined by inter-particle interactions. We analyze what characteristics of pair potential cause density anomaly using a thermodynamically Self-Consistent Ornstein-Zernike Approximation (SCOZA). The SCOZA is known to provide a very good description of the overall thermodynamics and a remarkably accurate critical point and coexistence curve. We consider a fluid of spherical particles with a pair potential given by a hard-core repulsion plus a Lennard-Jones type tail (HC-LJ system). We show that the soft-repulsion near the hard-core contact determines the behavior of excess internal energy which plays a crucial role in the anomalous behaviors of the system. Our results show that even though such models as second critical point hypothesis, a twostate model, liquid-liquid phase transition model, clathrate model, network model, and orientation-dependent potential would be important to some properties of water, those are not the immediate cause of the density anomaly in liquid water. We present also a core-softened potential which reproduces experimentally measured density-temperature curve in the wide temperature range much better compared to other models presented up to now. Although our study is restricted to liquid phases of water, it provides us with important insights into the thermodynamic properties of solid water. Makoto Yasutomi, J Earth Sci Climate Change 2013, 4:4 http://dx.doi.org/10.4172/2157-7617.S1.009S green tea (GT) and Peppermint (PM) teabags were used as adsorbents of dyes to purify aqueous solutions. Basic Yellow 57 (BY) and Crystal Violet (CV) were chosen as model dyes due to their widespread use in the scientific and cosmetics industries. Equilibrium parameters such as pH, mass of adsorbent, initial dye concentration, salinity and presence of heavy metals were studied to maximize the adsorption of the dyes from aqueous solution in discontinuous experiments at room temperature. Experimental data indicate that adsorption of BY is maximized at pH 6, with optimum adsorbent masses of 100 mg and 75 mg for GT and PM respectively. The adsorbents also reached their highest adsorption in the absence of salts and heavy metal with maximum initial concentrations of 0.085 g/L and 0.2 g/L for GT and PM, respectively. On the other hand, CV was greatly adsorbed at pH 4 with adsorbent masses of 75 mg and 25 mg of GT and PM, respectively. Both adsorbents were able to adsorb CV dye concentrations of up to 0.075 g/L. The presence of salts and heavy metals also had negative effects on the adsorption. Finally, desorption of the dyes were studied to recycle the adsorbents in repetitive adsorption cycles. BY was surprisingly desorbed by using diluted HCl and ethanol solutions, while CV showed better desorption in front of ethanol and acetone solutions. We believe this “clean” technology will educate us to take advantage of inexpensive waste materials to improve water quality.Sulphur is essential in healthy plant and crop yields. Rapidly, largely due to emission controls, soils are becoming depleted in sulphur. Soils also act as a significant carbon sink but suggest that soil carbon is largely released back into the atmosphere. Here we examine the potential of soil microorganisms in the sequestration of atmospheric CO2 whilst examining the role sulphur has to play on the fixation of CO2. Agricultural soils were incubated in a carbon dioxide incubation chamber (ECIC) for 12 weeks where CO2 or CO2 was added at 400 ppm. One sample-soil A-had elemental sulphur added as a supplement. Total microbial DNA obtained from CO2 and CO2 experiments were subjected to Isopycnic centrifugation. Labelled DNA fractions and total microbial DNA extractsfollowing incubationwere subjected to Pyrosequencing. RubisCO genes were quantified by qPCR over the course of the experiment. Phospholipid fatty acid analysis and DGGE was used to monitor the microbial community structure over the duration of the experiment. To track the fate of labelled carbon into the soil throughout the incubation NMR analysis was performed on soil samples at defined time points. We established that the addition of sulphur to soil, as a fertilizer, has a significant impact on the microbial community structure. The sequestration of atmospheric CO2 by soil microorganisms was stimulated through the addition of sulphur whilst Rubis CO gene copy numbers increased significantly following its addition to soil.This project aims at detecting variabilities and trends in outputs of a three dimensional hydro dynamical numerical model based on a version of the Princeton Ocean Model (POM), covering the region between 85°S-30°N and 70°W-25°E, with 0.5° x 0.5° resolution. Surface data of temperature and salinity, from Climate Forecast System Reanalysis (CFSR), together with meteorological data of winds and surface fluxes, generated by reanalyzes of NCEP / NCAR global model, were analyzed and used as model forcing. The temperature salinity data, meteorological data and the model results cover the period from 1980 to 2009 (30 years). The model was validated through comparisons of outputs with oceanic buoy data from the project PIRATA. Model results and sea surface temperature data from PIRATA display strong correlations, both in the annual and higher frequencies signals. Harmonic and statistical analyses of selected points, applied to meteorological parameters, sea surface elevation, temperature, salinity and currents provide information on the variabilities and trends in the Tropical and South Atlantic Ocean, in the period 1980-2009. Biography Joseph Harari has completed his M.Sc. in Physical Oceanography in 1978, Ph.D. in Meteorology in 1985 and postdoctoral studies in Physical Oceanography in 1991, from the University of Sao Paulo (SP, Brazil). His research is on Numerical Modeling applied to the ocean dynamics and he is an Associate Professor in the Postgraduate Programs in Oceanography and in the Post Graduate Program in Environmental Sciences, at the University of Sao Paulo (SP, Brazil).