Retrospective dosimetry with alumina substrate from electronic components

Alumina substrate can be found in electronic components used in portable electronic devices. The material is radiation sensitive and can be applied in dosimetry using thermally or optically stimulated luminescence. Electronic portable devices such as mobile phones, USB flash discs, mp3 players, etc., which are worn close to the body, can represent personal dosemeters for members of the general public in situations of large-scale radiation accidents or malevolent acts with radioactive materials. This study investigated dosimetric properties of alumina substrates and aspects of using mobile phones as personal dosemeters. The alumina substrates exhibited favourable dosimetry characteristics. However, anomalous fading had to be properly corrected in order to achieve sufficient precision in dose estimate. Trial dose reconstruction performed by means of two mobile phones proved that mobile phones can be used for reconstruction of personal doses.     

Why drivers use cell phones and support legislation to restrict this practice

The use of cell phones while driving is ubiquitous, particularly in countries where the practice is legal. However, surveys indicate that most drivers favor legislation to limit the use of mobile devices during the operation of a vehicle. A study was conducted to understand this inconsistency between what drivers do and what they advocate for others. Participants completed a survey about their driving attitudes, abilities, and behaviors. Following previous research, drivers reported using cell phones for benefits such as getting work done. The hypocrisy of using cell phones while advocating restrictions appears to stem from differences in the perceived safety risks of self vs. others’ use of cell phones. Many if not most drivers believe they can drive safely while using mobile devices. However, they lack confidence in others’ ability to drive safely while distracted and believe that others’ use of cell phones is dangerous. The threat to public safety of others’ usage of mobile devices was one of the strongest independent predictors of support for legislation to restrict cell phone use.     

A Novel System for Recognizing Recording Devices from Recorded Speech Signals

The field of digital audio forensics aims to detect threats and fraud in audio signals. Contemporary audio forensic techniques use digital signal processing to detect the authenticity of recorded speech, recognize speakers, and recognize recording devices. User-generated audio recordings from mobile phones are very helpful in a number of forensic applications. This article proposed a novel method for recognizing recording devices based on recorded audio signals. First, a database of the features of various recording devices was constructed using 32 recording devices (20 mobile phones of different brands and 12 kinds of recording pens) in various environments. Second, the audio features of each recording device, such as the Mel-frequency cepstral coefficients (MFCC), were extracted from the audio signals and used as model inputs. Finally, support vector machines (SVM) with fractional Gaussian kernel were used to recognize the recording devices from their audio features. Experiments demonstrated that the proposed method had a 93.4% accuracy in recognizing recording devices.     

Recent advances in dosimetry using the optically stimulated luminescence of Al2O3:C

This paper presents an overview of some very recent developments in optically stimulated luminescence (OSL) dosimetry using aluminium oxide (Al(2)O(3):C), with special emphasis given to the work of the research group at Oklahoma State University. Some of the advances are: (i) the development of a real-time optical fibre system for in vivo dosimetry applied to radiotherapy; (ii) the development of a fibre dosimetry system for remote detection of radiological contaminants in soil; (iii) the characterisation of Al(2)O(3):C in heavy charged particle fields and the study of ionisation density dependence of the OSL from Al(2)O(3):C; and (iv) fast and separate assessment of beta and gamma components of the natural dose rate in natural sediments. These achievements highlight the versatility of the OSL technique associated with the high-sensitivity of Al(2)O(3):C for the development of new dosimetry applications.     

Space radiation measurements on-board ISS--the DOSMAP experiment

The experiment 'Dosimetric Mapping' conducted as part of the science program of NASA's Human Research Facility (HRF) between March and August 2001 was designed to measure integrated total absorbed doses (ionising radiation and neutrons), heavy ion fluxes and its energy, mass and linear energy transfer (LET) spectra, time-dependent count rates of charged particles and their corresponding dose rates at different locations inside the US Lab at the International Space Station. Owing to the variety of particles and energies, a dosimetry package consisting of thermoluminescence dosemeter (TLD) chips and nuclear track detectors with and without converters (NTDPs), a silicon dosimetry telescope (DOSTEL), four mobile silicon detector units (MDUs) and a TLD reader unit (PILLE) with 12 TLD bulbs as dosemeters was used. Dose rates of the ionising part of the radiation field measured with TLD bulbs applying the PILLE readout system at different locations varied between 153 and 231 microGy d(-1). The dose rate received by the active devices fits excellent to the TLD measurements and is significantly lower compared with measurements for the Shuttle (STS) to MIR missions. The comparison of the absorbed doses from passive and active devices showed an agreement within +/- 10%. The DOSTEL measurements in the HRF location yielded a mean dose equivalent rate of 535 microSv d(-1). DOSTEL measurements were also obtained during the Solar Particle Event on 15 April 2001.     

New millennium frontiers of luminescence dosimetry

What are the new frontiers' facing us in the new millennium with respect to luminescence dosimetry? I suggest that the first is in methodology. The fast, sensitive optically stimulated luminescence (OSL) techniques developed recently have yielded the potential for rapid environmental monitoring, multiple measurements, dose imaging, and fast readout. New vistas of applications in medical dosimetry and remote dosimetry have opened. A second frontier is literally 'out of this world'--namely, space dosimetry. Extended stays in low Earth orbit and the potential for a 1000-day mission to Mars emphasise the challenges of dosimetry in this unique radiation environment. What role does luminescence dosimetry play in this field? This talk explores the possibilities and the challenges as we seek to penetrate these new frontiers.     

CW-OSL measurement protocols using optical fibre Al2O3:C dosemeters

A new system for in vivo dosimetry during radiotherapy has been introduced. Luminescence signals from a small crystal of carbon-doped aluminium oxide (Al2O3:C) are transmitted through an optical fibre cable to an instrument that contains optical filters, a photomultiplier tube and a green (532 nm) laser. The prime output is continuous wave optically stimulated luminescence (CW-OSL) used for the measurement of the integrated dose. We demonstrate a measurement protocol with high reproducibility and improved linearity, which is suitable for clinical dosimetry. A crystal-specific minimum pre-dose is necessary for signal stabilisation. Simple background subtraction only partially removes the residual signal present at long integration times. Instead, the measurement protocol separates the decay curve into three individual components and only the fast and medium components were used.     

Thermal pre-treatment in the OSL dating of quartz: is it necessary?

Thermal treatment before optically stimulated luminescence (OSL) measurement is an important step in all widely accepted OSL dating procedures used with quartz. This is a major constraint on the design of a portable luminescence instrument for estimating ages in the field. Preliminary experiments show that using a standard dating protocol without heating caused a 30-50% underestimation of equivalent dose. This underestimate arises mainly from OSL derived from the 110 degrees C thermoluminescence (TL) trap; because of the thermal instability of this trap, this OSL contribution is only present in unheated laboratory-regenerated signals, but not in the natural signal. An alternative to thermal pre-treatment is investigated, based on the mathematical separation of the stable dosimetry OSL signal from the total OSL; the latter is the sum of signals from several traps, including the 110 degrees C TL trap. Our results show consistency with dose estimates obtained using a standard measurement protocol including pre-heating.     

Evaluation of environmental dose at JCO using luminescence from quartz stimulated by blue light

The environmental dose due to the recent nuclear accident at JCO, Japan, was estimated using luminescence optically stimulated from unheated quartz. Two methods originally developed for dating analysis, the single aliquot additive dose method and the single aliquot regeneration added dose method, were employed to confirm the dose rate. Consistent results were obtained from both methods and from thermoluminescence measurements. Although the dose rate values had lower precision than can be obtained from heated materials, it is suggested that luminescence from sedimentary quartz can usefully be employed in retrosepective dosimetry.     

Preliminary OSL studies on beige sepiolites

Radiation-induced luminescence signals in beige sepiolite samples were investigated using optically stimulated luminescence. A thermally stable, light-sensitive radiation-induced signal was detected, and radiation dose response and thermal properties of this signal were studied. The thermal stability and dose sensitivity of the signal implies the potential of the material for dating and retrospective radiation dosimetry.     

Elimination of Cerenkov interference in a fibre-optic-coupled radiation dosemeter

An optical fibre point dosemeter based on the gated detection of the luminescence from a Cu(1+)-doped fused quartz detector effectively eliminated errors due to Cerenkov radiation and native fibre fluorescence. The gated optical fibre dosemeter overcomes serious problems faced by scintillation and optically stimulated luminescence approaches to optical fibre point dosimetry. The dosemeter was tested using an external beam radiotherapy machine that provided pulses of 6 MV X rays. Gated detection was used to discriminate the signal collected during the radiation pulses, which included contributions from Cerenkov radiation and native fibre fluorescence, from the signal collected between the radiation pulses, which contained only the long-lived luminescence from the Cu(1+)-doped fused quartz detector. Gated detection of the luminescence provided accurate, real-time dose measurements that were linear with absorbed dose, independent of dose rate and that were accurate for all field sizes studied.     

Influence of the stem effect on radioluminescence signals from optical fibre Al2O3:C dosemeters

This paper analyses the influence of the Cerenkov radiation and other noise sources, the so-called stem effect, on radioluminescence (RL) signals generated in optical fibre Al2O3:C dosemeters used in medical dosimetry. The optical fibre dosemeter consists of a sensitive Al2O3:C crystal coupled to an optical fibre cable that carries the RL and optically stimulated luminescence (OSL) signals generated in the Al2O3:C crystal. During irradiation of the dosemeter, the real-time dose rate can be determined from the RL signal and after irradiation the total dose absorbed is determined from the OSL signal stimulated using a focused green solid-state laser. In particular, the components of the stem effect generated in the fibres were analysed to determine their impact on the RL signal.     

Retrospective dose assessment: the measurement of the dose in quartz in dating and accident dosimetry

In retrospective dosimetry using luminescence it is never possible to obtain a sample of the unaltered phosphor as it was at somc time in the past and before radiation exposure. This prevents direct calibration using conventional personnel dosimetry techniques, and so measurement protocols must be devised which allow accurate estimation of the dose using only the exposed phosphor. This has led to the use of complex protocols, requiring many tens of notionally identical subsamples, to obtain one estimate of the unknown dose. More recently, considerable effort has gone into devising protocols which provide an estimate of the unknown dose from only one subsample. These avoid the need to assume homogeneity in the sample. These protocols also allow faster measurement, which for the first time makes it practical to obtain multiple estimates of the unknown dose and thus externally calculated random errors. This paper discusses the development of single-aliquot protocols, with particular reference to those devised for use with quartz, and finally reviews some of their applications in the retrospective assessment of dose.     

Criticality accident dosimetry systems: an international intercomparison at the SILENE reactor in 2002

In criticality accident dosimetry and more generally for high dose measurements, special techniques are used to measure separately the gamma ray and neutron components of the dose. To improve these techniques and to check their dosimetry systems (physical and/or biological), a total of 60 laboratories from 29 countries (America, Europe, Asia) participated in an international intercomparaison, which took place in France from 9 to 21 June 2002, at the SILENE reactor in Valduc and at a pure gamma source in Fontenay-aux-Roses. This intercomparison was jointly organised by the IRSN and the CEA with the help of the NEA/OCDE and was partly supported by the European Communities. This paper describes the aim of this intercomparison, the techniques used by the participants and the two radiation sources and their characteristics. The experimental arrangements of the dosemeters for the irradiations in free air or on phantoms are given. Then the dosimetric quantities measured and reported by the participants are summarised, analysed and compared with the reference values. The present paper concerns only the physical dosimetry and essentially experiments performed on the SILENE facility. The results obtained with the biological dosimetry are published in two other papers of this issue.     

Statistical Inference of User Experience of Multichannel Audio on Mobile Phones

Mobile phones and other handheld electronic devices are now ubiquitous and play an important role in our everyday lives. Over the last decade, we have seen a sharp rise in the sophistication of both hardware and software for these devices, thus significantly increasing their utility and use. Electronic devices are now commonly used for the streaming of audio and video and for the regular playback of music. Multichannel audio has now become a popular format and with recent updates in software, the latest audio codecs that support this format can effectively be played back on most electronic devices. As a result, more audio content that is now compatible with these devices is being produced. It is important to perform subjective quality tests for multichannel audio verses traditional stereo and mono on devices like mobile phones while using headphones. This paper presents the results and analysis of such listening tests that evaluate basic audio quality and quality of experience. The results show that while multichannel audio scores higher than stereo and mono for both of these attributes, the difference in score was less for the ratings of quality of experience. The results were processed using an Analysis of Variance (ANOVA) to show the statistical significance. Calculation of the effect size showed that the audio content had little bearing on the results.     

Driver performance while text messaging using handheld and in-vehicle systems

This study presents an evaluation of driver performance while text messaging via handheld mobile phones and an in-vehicle texting system. Participants sent and received text messages while driving with an experimenter on a closed-road course, using their personal mobile phones and the vehicle's system. The test vehicle was an instrumented 2010 Mercury Mariner equipped with an OEM in-vehicle system that supports text messaging and voice control of mobile devices via Bluetooth, which was modified to allow text message sending during driving. Twenty participants were tested, 11 younger (19–34) and 9 older (39–51). All participants were regular users of the in-vehicle system, although none had experience with the texting functions.Results indicated that handheld text message sending and receiving resulted in higher mental demand, more frequent and longer glances away from the roadway, and degraded steering measures compared to baseline. Using the in-vehicle system to send messages showed less performance degradation, but still had more task-related interior glance time and higher mental demand than baseline; using the system's text-to-speech functionality for incoming messages showed no differences from baseline. These findings suggest that using handheld phones to send and receive text messages may interfere with drivers’ visual and steering behaviors; the in-vehicle system showed improvement, but performance was not at baseline levels during message sending.     

Unsupervised clustering approaches to color classification for color-based image code recognition

Color-vision-based applications for mobile phones has become a subject of special interest lately. It would be interesting to investigate an unsupervised, adaptive, and fast algorithm that can classify color components into color clusters. We propose a hierarchical clustering approach using a single-linkage algorithm and a k-means clustering approach to color classification for color-based image code recognition in mobile computing environments. We also measured the performance of the proposed algorithms by color channel stretch, which is a simple color-correction method. Experimental results show that the single-linkage method is more robust than previous algorithms used in experiments with varying cameras and print materials. In particular the k-means-based method with color channel stretching has the highest performance and is the most robust under varying environment conditions such as illuminants, cameras, and print materials.     

Dosimetry at 28 keV synchrotron radiation for cell irradiations

Accurate dosimetry is a prerequisite for reliable comparisons between radiobiological irradiation experiments. Parameters affecting the determination of absorbed dose to cells in the shape of a small cell pellet in a centrifuge tube, irradiated by 28 keV mono-energetic photons from a synchrotron, were investigated. Thermoluminescent dosimeter (TLD), diode and ion chambers were utilized to monitor the irradiations. The distribution of the absorbed dose and such parameters as scatter, attenuation and interface dosimetry in the target, which influence the dose, were studied. A method for inter-calibrations of two different calibration sources by using TLD and TLD readers is given. Characteristics of the TLD, that is, fading, supralinearity, energy response, self-attenuation and mini-dosimetry were considered for the dosimetry. A method for correcting photon fluence attenuation in cylindrical TLDs is presented. The study shows that the absorbed dose to cells irradiated at low photon energy at a synchrotron irradiation facility can, using accurate dosimetry protocol, be correctly and reproducibly determined.     

How people access the internet and the democratic divide: Evidence from the Chilean region of Valparaiso 2017, 2018 and 2019

The Internet has been often described as a tool that fosters the inclusion of traditionally marginalized people in the democratic process. Yet, if the type of device used by people to access the Internet impacts their online democratic engagement, uneven Internet penetration and differences in the devices used by social groups will result in a deeper democratic divide. After discussing the impact of the types of internet use and type of access devices on civic engagement, we postulate 3 hypotheses on how democratic values and type of access to the Internet—place and devices—are related to the civic use of social media. We use data from a Valparaíso Regional poll in Chile in 2017, 2018 and 2019 to test those hypotheses. People who access the Internet via mobile phones are less likely to use social media with a civic purpose, while those who access the Internet at home or work are more likely to do so. Since low-income sectors primarily access the Internet via mobile phones while higher income groups have a wider array of Internet connection options, the rapid growth of cell phone use for accessing the Internet risks deepening social and income gaps in civic engagement.