bluuebunny/crossref_metadata_2025 huggingface dataset:
Emergence of Persistent Infection due to Heterogeneity
Authors: Agrawal Vidit , Moitra Promit , Sinha Sudeshna
Published: February 2017

We explore the emergence of persistent infection in a closed region where the disease progression of the individuals is given by the SIRS model, with an individual becoming infected on contact with another infected individual. We investigate the persistence of contagion qualitatively and quantitatively, under increasing heterogeneity in the partitioning of the population into different disease compartments, as well as increasing heterogeneity in the phases of the disease among individuals within a compartment. We observe that when the initial population is uniform, consisting of individuals at the same stage of disease progression, infection arising from a contagious seed does not persist. However when the initial population consists of randomly distributed refractory and susceptible individuals, a single source of infection can lead to sustained infection in the population, as heterogeneity facilitates the de-synchronization of the phases in the disease cycle of the individuals. We also show how the average size of the window of persistence of infection depends on the degree of heterogeneity in the initial composition of the population. In particular, we show that the infection eventually dies out when the entire initial population is susceptible, while even a few susceptibles among an heterogeneous refractory population gives rise to a large persistent infected set.
New evidence of Yangtze delta recession after closing of the Three Gorges Dam
Authors: Luo X. X. , Yang S. L. , Wang R. S. , Zhang C. Y. , Li P.
Published: February 2017

Many deltas are likely undergoing net erosion because of rapid decreases in riverine sediment supply and rising global sea levels. However, detecting erosion in subaqueous deltas is usually difficult because of the lack of bathymetric data. In this study, by comparing bathymetric data between 1981 and 2012 and surficial sediment grain sizes from the Yangtze subaqueous delta front over the last three decades, we found severe erosion and significant sediment coarsening in recent years since the construction of Three Gorges Dam (TGD), the largest dam in the world. We attributed these morphological and sedimentary variations mainly to the human-induced drastic decline of river sediment discharge. Combined with previous studies based on bathymetric data from different areas of the same delta, we theorize that the Yangtze subaqueous delta is experiencing overall (net) erosion, although local accumulation was also noted. We expect that the Yangtze sediment discharge will further decrease in the near future because of construction of new dams and delta recession will continue to occur.
Exploring the links between peptoid antibacterial activity and toxicity
Authors: Bolt H. L. , Eggimann G. A. , Jahoda C. A. B. , Zuckermann R. N. , Sharples G. J. , Cobb S. L.
Published: February 2017

The cytoxicity profiling of a series of linear peptoids against mammalian cell lines has been carried out and correlated against both antibacterial properties and hydrophobicity.
A novel TiO2nanostructure as photoanode for highly efficient CdSe quantum dot-sensitized solar cells
Authors: Lu Y. B. , Li L. , Su S. C. , Chen Y. J. , Song Y. L. , Jiao S. J.
Published: February 2017

For sensitized solar cells, photoanodes combining the advantages of TiO2nanoparticles (high specific surface area) and one-dimensional (1D) nanostructures (fast transport channels) are ideal for obtaining highly efficient sensitized solar cells.
2D Layered non-precious metal mesoporous electrocatalysts for enhanced oxygen reduction reaction
Authors: Huo Lili , Liu Baocang , Zhang Geng , Si Rui , Liu Jian , Zhang Jun
Published: February 2017

2D Layered meso-M/N-C/N-G nanocomposites with high specific surface area, homogeneous distribution of ultra-small M-N-C nanoparticles less than 5 nm, and mesopores with a size of ∼3.6 nm exhibit excellent electrocatalytic activity toward oxygen reduction reaction (ORR) in acidic and alkaline media.
Paraquat disrupts the anti-inflammatory action of cortisol in human macrophages in vitro: therapeutic implications for paraquat intoxications
Authors: Veríssimo Gesiele , Bast Aalt , Weseler Antje R.
Published: February 2017

The herbicide paraquate (1,1′-dimethyl-4,4′-bipyridinium dichloride) induces an inflammatory response in human macrophages which cannot be attenuated by cortisol.
New insights into the role of chitosan oligosaccharide in enhancing growth performance, antioxidant capacity, immunity and intestinal development of weaned pigs
Authors: Wan Jin , Jiang Fei , Xu Qingsong , Chen Daiwen , Yu Bing , Huang Zhiqing , Mao Xiangbing , Yu Jie , He Jun
Published: February 2017

Chitosan oligosaccharide (COS), an oligomer ofd-glucosamine, is a vital growth stimulant in the pig industry.
Antisolvent-assisted powder engineering for controlled growth of hybrid
CH3NH3PbI3 perovskite thin films
Authors: Choi Yong Chan , Lee Se Won , Kim Dae-Hwan
Published: February 2017

We develop antisolvent-assisted powder engineering for the controlled growth of hybrid inorganic-organic CH3NH3PbI3 (MAPbI3) perovskite thin films. The powders, which are used as the precursors for solution processing, are synthesized by pouring a MAPbI3 precursor solution into various antisolvents, such as dichloromethane, chloroform, diethyl ether, and toluene. Two types of powders having different colors are obtained, depending on the antisolvent used. The choice of the antisolvent used for synthesizing the powders strongly influences not only the phases of the powders but also the morphology and structure of the thin films subsequently fabricated by solution processing. This, in turn, affects the photovoltaic performance.
Thickness-induced spin-reorientation originated from competing magnetic shape anisotropies
Authors: Tang Jin , He Wei , Zhang Yong-Sheng , Zhang Wei , Li Yan , Ahmad S.Sheraz , Zhang Xiang-Qun , Cheng Zhao-Hua
Published: February 2017

Engineering the surface morphology of magnetic film is one of the important methods to tune the magnetic anisotropy of ultrathin magnetic material. However, the influence of competing shape effects on magnetic anisotropy of ultrathin film is still not clearly demonstrated. Here, we investigated the magnetic anisotropy of obliquely deposited Fe films on vicinal Si(111) substrate by using in-situ and ex-situ surface magneto-optical Kerr effect (MOKE). Thickness-induced in-plane spin-reorientation transition, i.e. magnetization easy axis gradually rotates away from the step direction, was observed. MOKE measurements and micromagnetic simulation demonstrate this spin-reorientation transition process largely originated from the competition between step-induced magnetic shape anisotropy and oblique-deposition-induced magnetic shape anisotropy. Our study indicates the possibility of tuning magnetic spin order orientation by the competing magnetic shape anisotropies.
Laser induced ultrafast magnetization reversal in TbCo film
Authors: Cheng Weiming , Li Xing , Wang Haiwei , Cheng Xiaomin , Miao Xiangshui
Published: February 2017

All optical switching is an emerging recording technology by using femtosecond laser to realize ultrafast magnetization manipulation for super-high magnetic storage. TbCo films possess ferrimagnetic structure and large perpendicular anisotropy and thus have the potential to be used as a AOS material. In this paper, we simulate the ultrafast magnetization reversal of TbCo films under 100fs pulse laser with a general theoretical framework and the simulated results show that TbCo films can generate magnetization reversal at the timescale of several ps. Co-sublattice completes demagnetization and subsequently triggers magnetize reversal within 1.0ps, whereas Tb- sublattice begins to magnetize reversal more than 4.0ps. Moreover, large laser power intensity easily induce the complete demagnetization and subsequent magnetization reversal regardless of the composition of TbCo films.
Commentary: Risk Assessment in the Age of Evidence-Based Practice and Policy
Authors: Desmarais Sarah L.
Published: February 2017

Risk assessment has come to be recognized as a key component of evidence-based practice and policy in psychiatric and correctional agencies. At the same time, however, there is significant debate in scientific, policy, and public arenas regarding the role of risk assessment instruments in mental health and criminal justice decision-making, and questions regarding the level of evidence supporting their usefulness. It is in light of these conflicting realities that the current commentary considers Williams, Wormith, Bonta, and Sitarenios' (2017) re-examination of the Singh, Grann, and Fazel (2011) meta-analysis and recommendations made in “The Use of Meta-Analysis to Compare and Select Offender Risk Instruments.” Additional limitations in the extant risk assessment research are identified and their implications for evidence-based practice and policy are discussed.
On the length of fully commutative elements
Authors: Nadeau Philippe
Published: February 2017

In a Coxeter group

W
W

, an element is fully commutative if any two of its reduced expressions can be linked by a series of commutations of adjacent letters. These elements have particularly nice combinatorial properties, and index a basis of the generalized Temperley–Lieb algebra attached to

W
W

.

We give two results about the sequence counting these elements with respect to their Coxeter length. First we prove that this sequence always satisfies a linear recurrence with constant coefficients, by showing that reduced expressions of fully commutative elements form a regular language. Then we classify those groups

W
W

for which the sequence is ultimately periodic, extending a result of Stembridge. These results are applied to the growth of generalized Temperley–Lieb algebras.
Where are the solar magnetic poles?
Authors: Pastor Yabar A. , Martínez González M. J. , Collados M.
Published: February 2017

Regardless of the physical origin of stellar magnetic fields – fossil or dynamo induced - an inclination angle between the magnetic and rotation axes is very often observed. Absence of observational evidence in this direction in the solar case has led to generally assume that its global magnetic field and rotation axes are well aligned. We present the detection of a monthly periodic signal of the photospheric solar magnetic field at all latitudes, and especially near the poles, revealing that the main axis of the Sun's magnetic field is not aligned with the surface rotation axis. This result reinforces the view of our Sun as a common intermediate-mass star. Furthermore, this detection challenges and imposes a strong observational constraint to modern solar dynamo theories.
A New Solid State Beta Dosemeter
Authors: Jones A.R. , Sanders J.M.
Published: February 2017

The use of a metal oxide silicon field effect transistor (MOSFET) as a gamma and X ray dosemeter has been previously reported. This paper reports measurements on the performance of MOSFETS for beta dosimetry. The sensitive area of the sensor is less than 7 mg.cm-2 below the surface of the MOSFET and hence, with the appropriate window thickness, the MOSFET should be energy independent for beta rays. The sensitivity of MOSFETS to beta rays of different energies has been measured for various thicknesses in order to establish the optimum thickness for energy independence. Using a polycarbonate cover, the optimum thickness was about 5.4 mg.cm-2. With this cover the energy dependence was less than ±10% for beta ray spectra with end point energies from 0.23 to 2.2 MeV. The dependence upon direction was less than 20% for angles of incidence up to 45o. The results of these experiments and other dosimetric parameters are presented. The application of MOSFETS to beta dosimetry is discussed in terms of the values of the dosimetric parameters obtained.
The Angular Response of Lithium Fluoride for Several Beta Emitters
Authors: King C.W.
Published: February 2017

The angular dependence of the response of thermoluminescent lithium fluoride (TLD-100) solid detectors has been investigated. The angle of incidence was varied from perpendicular to parallel for 147Pm, 204Tl and 90Sr-90Y beta particles. The test dose was 1 mGy (in air) in all cases. The TL detector response is also determined for thin Teflon encapsulation and for attenuating absorber thicknesses from 0 to 75 mg.cm-2. Experimental results are presented in mGy and also in arbitrary units normalised to the perpendicular TL detector response.
A Comparison of Two Methods of Rapidly Heating Thick TLDs
Authors: Jones A.R.
Published: February 2017

To heat a TLD quickly, the process should be limited only by the thermal characteristics of the TLD itself. One method is to bring the TLD into thermal contact with a metal mass, or anvil at a constant temperature which is approached asymptotically by that of the TLD. An alternative is to supply radiant heat to the TLD, for example from a CO2 laser. If this is done quickly, to minimise heat losses, the TLD temperature will rise linearly with time. Measurements have been made with experimental heaters of both types with the following parameters needed for their comparison: the time needed to heat the TLDs and its reproducibility, and the reproducibility of TLD readings when exposed and unexposed to radiation. With a 5 W CO2 laser, the heating time for a 0.9 mm thick TLD was about 10 s compared with about 6 s for the anvil heater. The heating rate for the laser heater was more consistent than for the anvil heater, but the latter provided more reproducibility in dosemeter readings. The use of the laser reduced the residual signal below a detectable level. The performance of both methods was shown to depend upon the methods of mounting the phosphor and the data analysis.
Dosimetric Characteristics of Different TL Phosphors
Authors: Ranogjec-Komor M. , Osvay M.
Published: February 2017

The photon energy dependence of different TL phosphors LiF:Mg,Ti, MgB4O7:Dy, CaF2:Mn, Al2O3:Mg,Y was measured using X ray radiation (48-205 keV) and a 60Co source. The relative sensitivity, linearity, fading and UV light induced TL signal were investigated in the dose range from several mGy to several Gy.
Thermoluminescent Mechanisms in CaSO4:Dy Single Crystals
Authors: Morgan M.D. , Stoebe T.G.
Published: February 2017

ESR studies of gamma-irradiated CaSO4:Dy have shown, in addition to the usual intrinsic defects, four new paramagnetic centres. An analysis of the g values and the g tensors in conjunction with the anhydrite crystal structure indicate that these centres are related to sulphate ions, this structure being stabilised by a neighbouring Ca vacancy. Centre 3b is suggested as a hole associated with one sulphate ion, again stabilised by an adjacent Ca vacancy. Because of the two distinct crystallographic directions in the anhydrite structure, centre 3b was found to consist of two distinguishable defects with slightly differing decay temperatures. The fourth centre appears to be an electron trapping site with structure similar to centre 3b. Decay temperatures of these ESR defects are correlated with the observance of TL peaks in CaSO4:Dy. Thermoluminescence studies as a function of impurity content confirmed the presence of calcium vacancies, which are formed during crystal growth, and that they play an important role in the TL process. TL models are proposed to account for the observed properties of CaSO4:Dy.
The Variation with LET of the Responses of TLD-700 and TLD-600 at Temperatures up to 200 oC
Authors: Douglas J.A. , Perks C.A. , Cotterill D.A.
Published: February 2017

Previous research into the effects of temperature on the responses of the thermoluminescent (TL) material, TLD 700, has been extended to include: (i) the effect on the trap structure of heating before irradiation; (ii) increasing the temperature range to 200 oC; (iii) the influence of LET on the effects by utilising the 6Li(n,a)3H reaction in TLD-600. Slow ramp heating of phosphors which had been stored at temperatures of 120 oC and above before irradiation revealed an additional peak in the glow curve between peaks 3 and 4. The relative heights of peaks also change. The increase in sensitivity with irradiation temperature is less for high LET radiation; however, fading does not depend on LET. The fading of the 240 oC readout of TLD-700 agrees with the theory of Randall and Wilkins (1945) but TLD-600 does not. The changes in response are complex and studies are in progress to separate the effects on individual peaks.
Relationship Between Thermoluminescence and Thermally Stimulated Exoelectron Emission of BeO Thin Film Dosemeters
Authors: Lesz J. , Kriegseis W. , Scharmann A.
Published: February 2017

BeO thin films have been suggested as TSEE dosemeters. Apart from TSEE they also show thermoluminescence. Their TL properties are very similar to those of BeO ceramics with respect to temperature positions of the maxima, spectral distribution of the emitted light, optical fading and mass specific TL sensitivity. For both TSEE and TL optical fading is more pronounced at the low temperature glow peaks. However, TSEE and TL originate from different centres whose relationship to the corresponding centres in ceramic BeO is discussed. Previously emptied emission centres are refilled by phototransfer during UV irradiation. Thus dose reassessment is feasible. The TSEE signal can still be re-established after a dose readout heating cycle up to 600 oC, whereas TL is annealed completely already below 300 oC.
Study of Dose-Response Relationships for Late Somatic Effects of Low Neutron Doses
Authors: Coppola M. , Covelli V. , Di Majo V. , Rebessi S.
Published: February 2017

Complete observation of survival and late pathology was conducted on over 2000 female mice irradiated with single doses of 1.5 MeV neutrons (5, 10, 20, 40, 80, 160 mGy) and X rays (40, 80, 160, 320, 640, 1280, 2560 mGy). The results showed a statistically significant life shortening for neutron doses not lower then 80 mGy. Assuming linear non-threshold dose-effect relationships for both radiation qualities, a neutron RBE of 12.3 was obtained. Solid tumour induction was also significant from a neutron dose of 80 mGy and for X ray doses larger than 1 Gy. No sublinear dependence of the carcinogenic effect on low neutron doses was seen. Separate examination of ovarian tumour indication indicated that a threshold dose is likely to exist, especially for X rays. A trend analysis of the neoplasm incidence confirmed the above findings. Death rate analysis by the Weibull model showed agreement between the shift to earlier times and tumour induction.
Quality Factor: Conceptual Problems and Practical Solutions
Authors: Dennis (INVITED) J.A.
Published: February 2017

In the past ten years a growing divide has become apparent between the dosimetric concepts designed to provide measures of stochastic risks and those designed for the measurement and control of exposures to radiation. Those designed to provide estimates of risk, e.g. effective dose equivalent, might need to be further refined to incorporate the latest scientific beliefs and evidence about the dependence on radiation quality and dose rate as well as on age and sex. It may be anticipated that they will find increasing application in compensation schemes and in the evaluation of the health detriment from different applications of radiation, particularly in the medical field. Both animal and human evidence strongly supports a belief that different tissues and different types of neoplasm will have different dependencies on radiation quality and dose rate, although it is not at present possible to quantify this belief. For practical purposes of risk estimation it is necessary, therefore, to select the same values for all human neoplasms. There are reasons for using life shortening in animals as a basis for this purpose, but the data for the dependence on the whole range of radiation qualities is meagre. There is a resulting requirement for interpolation and extrapolation, and a variety of proposals for doing so. None of these proposals has any clear advantages. To provide some stability for the new concepts of measurement and calibration it may be better to accommodate changing perceptions on radiation risks by specifying different levels of exposure for different types of radiation without changing the current quality factors for the measurement quantities.
Individual Monitoring for Neutrons: Practical Measurements, ICRU Recommended Quantities and Limited Quantities
Authors: Wagner S.R.
Published: February 2017

The metrological properties of the new ICRU recommended quantities for individual monitoring are reviewed in the light of existing practice. Consequences for calibration procedures and for the relevance of monitoring results for radiation protection control are discussed. Response requirements for individual neutron monitors are stated and a formalisation for the direct entry of monitoring results into individual radiation exposure records is suggested. The expedience of the ICRU definition of the individual dose equivalent is thereby questioned.
Albedo Dosimetry System for Routine Personnel Monitoring
Authors: Piesch E. , Burgkhardt B.
Published: February 2017

The universal albedo neutron dosemeter used with automatic thermoluminescence readout systems manufactured by Alnor, Harshaw, Panasonic and Vinten, is a two component neutron dosemeter consisting of an albedo and an additional thermal neutron detector and may also incorporate a recoil etched track detector inside the boron-loaded plastic encapsulation. Within routine monitoring, the variety of neutron fields can be reduced to four: (N1) of reactors, low-energy linear accelerators, (N2) nuclear fuel processing, (N3) radioactive neutron sources, (N4) high energy accelerators. Within one area, the albedo neutron response does not vary by more than a factor of two. The albedo dosemeter system became the official neutron dosemeter in the Federal Republic of Germany, thereby replacing the neutron film dosemeter. The technique of dose estimation, the classification in stray neutron fields, the dosimetric properties, such as dose range, energy and angular response, uncertainties of neutron dose measurement and results of routine applications are all described.
Performance Characteristics of Neutron Personnel Dosemeters used in the Oak Ridge Intercomparison Studies
Authors: Swaja R.E.
Published: February 2017

To provide an opportunity for dosimetrists to test and calibrate their neutron personnel monitoring systems, the staff of the Dosimetry Applications Research Facility at the Oak Ridge National Laboratory (ORNL) has conducted personnel dosimetry intercomparison studies (PDIS) periodically since 1974. During these studies, neutron dosemeters are mailed to ORNL, exposed to low level (less than 15 mSv) dose equivalents in a variety of mixed radiation fields produced using the Health Physics Research Reactor (HPRR), and then returned to the participants for evaluation. Beginning with the Seventh PDIS in 1981, interest and participation in the Oak Ridge intercomparisons increased significantly and consistent and documented methods for determining reference neutron dose equivalents for the HPRR were introduced. This paper presents a summary and analysis of about 3450 neutron dose equivalent measurements reported for PDIS 7 through 12 (1981-1986) with particular emphasis on low dose equivalent sensitivity, accuracy and precision, and performance relative to accreditation standards for the basic types of personnel dosimetry systems.
On the Calibration of Tissue-Equivalent Proportional Counters with Built-in Alpha Particle Sources
Authors: Schrewe U.J. , Brede H.J. , Pihet P. , Menzel H.G.
Published: February 2017

The calibration procedure for tissue-equivalent proportional counters (TEPC) with built-in collimated a sources was investigated. Pulse height spectra were measured for the a particle sources of several counters which were filled with propane based TE gas at various pressures in order to simulate a tissue layer thickness of 1 µm to 10 µm. The mean pulse height produced by unscattered a particles was determined relative to the maximum measured pulse height. These pulse height ratios were also calculated using tabulated stopping power data for a particles, the experimentally determined detector geometry and measured a source energies. The ratios obtained for various stopping power data are compared with the experimental values. Characteristic edges due to maximum energy losses of secondary protons and a particles over the finite cavity diameter also appear in neutron produced spectra. It is proposed to use the pulse heights related to maximum energy losses of charged particles in the detector cavity to examine the uncertainty of the conventional TEPC calibration techniques.
Determination of the Recombination Index of Quality for Neutrons and Charged Particles Employing High Pressure Ionisation Chambers
Authors: Golnik N. , Wilczynska-Kitowska T. , Zielczynski M.
Published: February 2017

The concept of the recombination index of quality (RIQ) is based on the degree of initial recombination and was introduced to provide a measurable quantity of radiation quality. The RIQR values can be determined employing a high pressure ionisation chamber operated under saturation conditions and at a suitable collecting potential, UR. Experiments were performed with various types of radiation including monoenergetic neutrons with energies of 0.9, 2.1, 5.5 and 14 MeV, polyenergetic neutrons (Pu-Be and 252Cf with different filters), high energy protons and alpha particles from natural uranium. To obtain RIQ values for neutrons alone, the photon component of the total absorbed dose was determined using the twin chamber technique and the photon component was subtracted from the total RIQ. It is shown that RIQ4 values can estimate with good accuracy the quality factor values (ICRP 1973). RIQ1 (or RIQ0.5/1 determined from measurements at saturation and two voltages) can be used for estimation of QF values recently proposed by ICRU. The expected independence of RIQ4 on filling gas pressure was confirmed experimentally for a Pu-Be source.
Measurement of the Neutron Spectrum inside the Containment of a PWR
Authors: Birch R. , Delafield H.J. , Parks C.A.
Published: February 2017

Neutron spectra inside the containment building of a PWR at Gosgen, Switzerland have been measured using a high resolution, transportable, neutron spectrometry system based on proportional counters. Small spherical proportional counters, filled with hydrogen to pressures of 100, 300 and 1000 kPa, were used to cover the energy range from 50 keV to 1.5 MeV. A larger cylindrical counter, filled with 600 kPa of 4He plus 400 kPa Ar was used to extend the measurement range up to 16 MeV. Compact electronics provided simultaneous data acquisition for up to four counters allowing spectrum measurements to be performed in dose equivalent rates down to ~50 µSv.h-1. Supporting measurements were made with a multisphere spectrometer to determine the fraction of neutrons below 50 keV. The neutron spectra measured at two positions show a steady rise in the neutron fluence as the neutron energy decreases, with very few neutrons having energies above 700 keV.
Studies of High Pressure Ionisation Chambers in Neutron and Photon Fields
Authors: Zoetelief J. , Golnik N. , Broerse J.J.
Published: February 2017

The responses from tissue-equivalent (TE) and Al high pressure ionisation chambers at various collecting potentials in dependence upon the pressure of several filling gases, including Ar, Ar with such hydrogen-rich gases as CH4, C2H4, and TE gas, are of practical and theoretical interest. The present investigations are aimed at developing a sensitive system for the determination of total dose and dose equivalent, the photon contribution, and obtaining information on cavity size effects. The use of CH4 in the TE chamber provides the most suitable system as regards sensitivity among the chamber/gas combinations investigated for total dose equivalent determination in the neutron energy region of 0.9 to 15 MeV. The Al/Ar high pressure chamber system is the most suitable as a photon dosemeter. Information on effects due to cavity size can be obtained from measurements with Ar and CH4 in both chambers.
Transfer of 226Ra and 210Pb to Forage and Milk in a Brazilian High Natural Radioactivity Region
Authors: Amaral E.C.S. , Carvalho Z.L. , Godoy J.M.
Published: February 2017

The Pocos de Caldas plateau, where the Brazilian uranium mine and mill facilities are located, is a natural high radioactivity region. A study has been carried out in order to assess the environmental transport of the natural radionuclides in the region. The present work is concerned with the transfer of 226Ra and 210Pb to forage and milk. Similar concentrations for both radionuclides were found in soil samples. In forage 210Pb concentrations are one order of magnitude higher than those of 226Ra, however, the milk samples presented higher values for 226Ra concentrations. The average forage to milk concentration factors are of the order of 10-4 d.l-1 for 226Ra and 10-5 d.l-1 for 210Pb. Regarding transfer mechanisms, the results suggest the foliar deposition as the main pathway for 210Pb uptake by the forage. In contrast, for 226Ra the root uptake appears as the main transfer pathway.
The Feasibility of Using Expert Systems to Cope with the Complexity and Extent of the Indoor Radon Problem
Authors: Raes F. , Poffijn A. , Eggermont (INVITED) G.
Published: February 2017

The main problems in predicting the average radon concentration in a single house are: (1) to obtain specific high resolution information about the house, and (2) to handle qualitative but relevant information. We introduce the idea of using an expert system to obtain high resolution data by interrogating the inhabitants about their house, as well as to interpret the qualitative information obtained in this way. To study the feasibility of this approach, a prototype expert system has been written which was given the obvious name Radon Expert System (RAES). RAES derives a radon index starting from information obtained from geological maps and other data bases. It subsequently refines this information and focusses on a single house by asking for information from the inhabitants. With the help of RAES, we interrogated the inhabitants of a number of houses where radon measurements had previously been performed. The correspondence between prediction and measurement is encouraging.
The Flow and Diffusion of Radon Isotopes in Fractured Porous Media: Part 2, Semi-infinite Media
Authors: Schery S.D. , Holford D.J. , Wilson J.L. , Phillips F.M.
Published: February 2017

The release of radon isotopes under conditions of combined diffusion and flow from a fractured, semi-infinite medium such as soil is analysed. Relations are developed to indicate when flow from fractures will dominate overall transport and when the radon released from fractures will have the concentration characteristic of great depths. The presence of pressure-driven flow from fractures can greatly enhance transport of radon, but narrow or shallow fractures are not necessarily important due to the strong diffusive exchange with the surrounding porous medium and a reduced vertical pressure gradient in the surrounding medium. Results should be of use in estimating whether fractures are important in transporting radon to air spaces where pollution from radon is a concern.
Uncertainties in Radon Daughter Measurement Arising from Fluctuations in Room Parameters
Authors: Vanmarcke H. , Berkvens P. , Poffijn A. , Raes (INVITED) F.
Published: February 2017

A Monte Carlo simulation model is described to evaluate the uncertainties induced, on the one hand, by assuming constant daughter concentrations and a constant flow rate during sampling and, on the other hand, in calculating the different physical parameters of the radon decay products, using the room model. It is found that, in general the uncertainties due to counting statistics and due to the fluctuations in the pump flow rate are small compared to the uncertainties induced by the fluctuations of the parameters of the room model. With the model a number of realistic situations, such as smoking cigarettes, opening or closing a window, etc. are simulated. Sampling half an hour after smoking a cigarette, for instance, under-estimates the steady state value of the 214Bi concentration by 35%. The uncertainties in the determination of the deposition rate of the unattached daughters are also evaluated. It is shown that, without special precautions to keep a steady state situation in the room, the error easily exceeds 50%.
Radon 222 Concentrations in the United States - Results of Sample Surveys in Five States
Authors: Ronca-Battista M. , Moon M. , Bergsten J. , White S.B. , Alexander B. , Holt N.
Published: February 2017

During the winter of 1986-1987, the United States Environmental Protection Agency (EPA) provided assistance to ten states to begin state-wide radon surveys. This paper presents survey results from the five states that completed a survey using a probability sample of housing units. Radon concentrations in six thousand homes in Alabama, Kentucky, Tennessee, Wisconsin, and Wyoming were measured. The data recorded from detectors placed in those houses have been compiled into the first multi-state survey of radon levels that allows valid extrapolation to the population at large. The target population was ground level, owner occupied residences with listed telephone numbers. Each state was partitioned into strata according to geologic characteristics relevant to radon levels. A systematic random sample of telephone numbers was selected within each stratum, and the telephone numbers together with associated names and addresses were supplied to each state. Charcoal canisters were deployed for a two-day period in each sample home, following the EPA screening measurement protocol. Strict procedures were followed to ensure randomness of the sample and the accuracy of the measurements. The results were analysed to produce estimates of the frequency distribution of radon concentrations throughout each state and for areas within states. A smaller sample of residences which were volunteered by their owners in each state also received detectors. The radon data from these houses were analysed separately. Estimates from the two northern states were significantly higher than those from the more southerly states and estimates for volunteers tended to be higher than the estimates from the random sample of homes. In the former case, the differences were influenced by the proportion of homes with basements.
Survey of the Natural Radiation of Belgium Territory as Determined by Different Methods
Authors: Deworm J.P. , Slegers W. , Gillard J. , Flemal J.M. , Culst J.P.
Published: February 2017

Measurement of the environmental exposure to natural radiation was performed by the Institute of Hygiene and Epidemiology and the Nuclear Research Centre in Mol. The aim of the study was the estimation of the external doses from natural radioactivity, received by the Belgian population and the setting up on a map of the territory of natural exposure rates measured using different methods.
House Characteristics Associated with Gamma Radiation and Radon Daughter Working Levels in Eastern Pennsylvania
Authors: Stebbings J.H. , Dignam J.J. , Reilly M.A. , Gerusky T.M. , Hartman T.T. , Anast G.A.
Published: February 2017

Working levels (WL) of radon daughters and ? measurements in basements are described for ~1200 houses near the Reading Prong. House variables included condition and construction materials of basement floors and walls, basement heights and areas, heating systems, air conditioning, water supply, and presence of drains and sump pumps. WLs were poorly predicted by house characteristics or ? measurements, while ? levels were well predicted by house characteristics and WL. Factors predicting high ? levels tended to be associated with low WLs and vice versa. Dirt basement floors and fieldstone basement walls were strongly associated with high ? levels, as were poor wall conditions in multivariate analyses. Gamma levels were low in electrically heated homes. High WLs were strongly associated with electric heat, low WLs with basement walls of fieldstone and/or in poor condition. Large house volumes and well water supply were also associated with higher WLs.
Reducing Radon Risks: The Approach in the United States
Authors: Guimond (INVITED) R.J.
Published: February 2017

Indoor radon levels in excess of 100,000 Bq.m-3 have been measured in homes in various areas in the United States. Thousands of homes have been identified with radon levels exceeding 1000 Bq.m-3. To respond to this serious public health problem, the United States has initiated a programme to assess the health risks posed by radon throughout the country and reduce unnecessary exposures from indoor radon. This paper provides an overview of the key elements that make up the strategy as implemented by the US Environmental Protection Agency. Some of the critical projects are described. These include national and regional surveys, health studies, geological mapping and characterisation studies, land evaluation activities, mitigation and prevention activities, and issuing health guidelines. The paper also reviews the recent legislation passed by the US Congress regarding indoor radon.
Reduction of Radon Progeny Concentration in Ordinary Room Due to a Mixing Fan
Authors: Abu-Jarad F. , Sextro R.G.
Published: February 2017

Three experiments were carried out at the Indoor Air Quality Research House (IAQRH) at Lawrence Berkeley Laboratory, University of California, to study the effect on the radon progeny of operating a mixing fan. At the beginning of every experiment, about 15 kBq.m-3 of radon was injected into a 36 m3 ordinary room. Measurements were conducted with three different aerosol particle concentrations of about 102, 104 and 105 per cm3. Real-time measurements of radon and progeny concentrations, particles and environmental parameters, were made throughout the experiments. Measurements of plated out activity on the surfaces of internal walls of the room and fan blades were measured directly by filter papers and CR-39 nuclear track detectors placed on the surfaces. The ratio of plated out activity to the total progeny activity in the room varied from 17% to 84%, in inverse relation to the particle concentrations. More than 99% of the plateout activity was found on walls and less than 1% on the fan blades.
Non-Homogeneous Kinetics in Irradiated Matter: An Appraisal of Computational Strategies
Authors: Klots C.E. , Hamm R.N. , Wright H.A. , Turner J.E.
Published: February 2017

The Monte Carlo method may be used to simulate chemical reactions occurring in the track of a charged particle. We compare these simulations with predictions of solutions to the diffusion equation. Conditions are delineated when the latter may be used.
Energy Migration in DNA Irradiated in the Solid State
Authors: Adams G.E. , Al-Kazwini A.T. , O'Neill P. , Fielden (INVITED) E.M.
Published: February 2017

Evidence for the role of energy migration in irradiated DNA is considered. In particular, data from fast time-resolved spectroscopy of DNA, in the solid state, irradiated with high energy pulsed electrons is discussed. The hydration layer in DNA has only a small effect on the intensity of the fluorescence emitted during pulse irradiation, but does influence post-irradiation changes as measured by diffuse reflectance spectroscopy. The short-lived fluorescence spectra from pulse-irradiated solid mixtures of DNA containing relatively low concentrations of the electron-affinic compound misonidazole, are reduced in intensity compared with the spectrum of pure DNA. These rapid quenching effects are interpreted in terms of the migration of energy liberated during irradiation.
On Possible Limitations of Experimental Nanodosimetry
Authors: Amols H.I. , Wuu C.S. , Zaider M.
Published: February 2017

Experimental microdosimetry is based on the assumption that energy deposited in a simulated volume can be approximated by the product of the number of ionisations detected and the W value. Energy deposited, however, is a stochastic variable representing the energy transfer expended in ionisation and excitation events. The proportionality between energy transfer and ionisation is only valid for large numbers of interactions per event, a condition usually satisfied in microdosimetry but not necessarily in nanodosimetry. Monte Carlo computer simulations of particle tracks in water vapour show that minimum ionising electrons traversing 1 nm spheres produce on average, 1.4 energy transfers per event. Simulated proportional chamber measurements of single event spectra are dominated by ion counting statistics rather than true energy deposition, with subsequent determination of average lineal energy being more than two times the true value. The interpretation of such data is discussed, as are conditions for which meaningful experimental data can be obtained.
Dose Mean Lineal Energy for Neutrons
Authors: Leuthold G. , Burger G.
Published: February 2017

Several proposals have been presented recently (ICRU 40, Zaider and Brenner, Kellerer) on the definition of the quality factor for charged particles on lineal energy density rather than on LET. The models of ICRU 40 and Kellerer result in a direct proportionality of the quality factor to y in the lower range of y up to about 100 keV.µm-1 with q(y) = 0.3 y. From this the neutron quality factor is derived to be Qn = 0.3 yD. The version of Zaider and Brenner results in a expression Qn = 0.03 + 0.24 yD. A similar expression was used by Bengtson in 1969. Without the knowledge of the f(y) distribution, yD can be calculated using the proximity function approach by Kellerer applied on calculated ion event tracks. Such calculations were performed for protons, a particles and heavy recoils in the energy range of 0.2 MeV.amu-1 up to 15 MeV.amu-1 in water vapour. From the charged particle data yD is then calculated as a function of neutron energy in soft tissue from thermal energy up to 14.1 MeV. The new proposals are related to the f(y) distribution in a sphere of 1 µm diameter. Smaller target sizes have, however, been proven to be relevant in quantitative radiation biology. The variation of yD with target size (1 nm up to 1 µm) is shown as a function of neutron energy and the deviation from the LET approximation is discussed, which is caused by straggling effects and d ray escape and is most pronounced at small target sizes. Results of the several new concepts are compared with each other and with old ones, based on q(L), and the impact on neutron radiation protection is discussed.
Implications of Radiobiological and Dosimetric Studies of DNA-Incorporated 123I: The Use of the Auger Effect as a Biological Probe at the Nanometre Level
Authors: Kassis A.I. , Makrigiorgos G.M. , Adelstein S.J.
Published: February 2017

A quantitative comparison of the radiotoxicity in V79 cells of the DNA-incorporated thymidine analogue, 5-iodo/bromo-2'-deoxyuridine labelled with 123I (123IUdR), 125I (125IUdR) and 77Br (77BrUdR) is presented. The total number of decays in the cell nucleus corresponding to a survival level of 37% (D37) is in the ratio of 2.2:1.0:3.0 for 123I, 125I and 77Br, respectively. The number of atoms that must be incorporated to produce a certain level of survival is radically different for the three nuclides because of their very different physical half-lives. However, the radiation dose to the nucleus (DN required to produce the D37 is approximately the same for all radionuclides (about 0.8 Gy) within the experimental uncertainty limits and, therefore, appears to be a good macroscopic parameter to describe radiotoxicity provided that the Auger electron emitters have identical intracellular localisation. The dose rate to the nucleus and its variation during the experiments is also about the same in the three cases. Dosimetric analysis at the microscopic level shows for the three isotopes that the number of decays needed to produce a certain level of survival is inversely proportional to the energy deposited per decay in 5 nm diameter volumes. This leads to considerations that preclude chemical identity, electron excitation energy, or nuclear recoil energy of the daughter atom as being important to the observed effects. In addition, it reveals that each of the two steps involved in the 125I decay is equally efficient in causing biological damage and that no saturation effects are present following the decay of 125IUdR in the DNA of V79 cells. Conclusions are reached regarding repair of sub-lethal damage caused by the Auger decay and the level of minimum energy required to be dissipated in 5 nm diameter sites in order to cause cell death (threshold for lethal radiation action).
Transient Dose Distribution in LiF Single Crystals Irradiated with High Energy Pulsed Electrons
Authors: Yamamoto T. , Oda K.
Published: February 2017

The build-up stage of short-lived excitons corresponds to the accumulating stage of the absorbed dose at the same region. Hence sequential observation of the former stage would make it possible to pursue the temporal variation of the accumulating absorbed dose. A pulse radiolysis system enables one to obtain the transient depth-dose profile in a sample irradiated with high energy electrons of 20 ps pulse duration by measuring the build-up process of the optical density through the sample. It has been observed that the electron energy is deposited to a certain depth in about 100 ps after the primary electrons have passed through that region. This means that the energy deposition is mainly attributed not to the primary electrons but to the slower secondary ones.
UV Induced Trapping in Powder and in Sintered CaSO4:Tm and CaSO4:Dy
Authors: Chakrabarti K. , Mathur V.K. , Abbundi R.J. , Hill M.D.
Published: February 2017

CaSO4:Tm and CaSO4:Dy are both known to possess a dosimetric peak at approximately 220 oC. A TL peak at a temperature higher than this dosimetric peak is observed on UV irradiation in powder CaSO4:Tm and CaSO4:Dy and on UV and ? irradiation in sintered CaSO4:Tm and CaSO4:Dy. This peak is at ~330 oC and ~280 oC in powder CaSO4:Dy and CaSO4:Tm respectively and at ~330 oC in the sintered pellets of both the materials. It is observed that UV light causes charge trapping as well as phototransfer involving this peak.
On the Thermoluminescence Mechanism of Non-Doped Corundum Monocrystals with Defect Structure
Authors: Gimadova T.I. , Bessonova T.S. , Tale I.A. , Avvakumova L.A. , Bodyachevsky S.V.
Published: February 2017

An investigation was carried out into the distribution of optical absorption, radioluminescence and thermostimulated luminescence (TSL) in large corundum crystals with defects. The dependence of energetic and stochastic parameters of the TSL process on stimulation temperature was analysed for detectors cut from fixed crystal points. TSL, proceeding by the mechanism of structural thermally initiated rearrangements and pure centre structures, was shown to provide for the occurrence of a unique set of operating parameters for ionising thermoluminescent detectors made of this material.
Dependence of Thermoluminescence Response of CaSO4:Dy and CaSO4:Tm on Grain Size and Activator Concentration
Authors: Kása I.
Published: February 2017

The influence of several factors on the thermoluminescence (TL) sensitivity and the shape of the glow curves of CaSO4:Dy and CaSO4:Tm phosphors have been investigated. The factors investigated are: quality of starting materials, activator concentration and grain size. The TL sensitivity and the height of low temperature peaks (LTP) are influenced by the impurity of the starting chemical (CaSO4.2H2O) and the concentration of activators (Dy and Tm). Sensitive CaSO4:Dy and CaSO4:Tm phosphors having small LTP were prepared by using purified starting chemical (CaSO4.2H2O). The measurement data from our samples were compared with the results of samples prepared in different laboratories.