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Objective: To study recall of mobile phone usage, including laterality and hands-free use, in young people. Methods: Actual mobile phone use was recorded among volunteers aged between 10 and 24 years from 12 countries by the software application XMobiSense and was compared with self-reported mobile phone use at 6 and 18 months after using the application. The application recorded number and duration of voice calls, number of text messages, amount of data transfer, laterality (% of call time the phone was near the right or left side of the head, or neither), and hands-free usage. After data cleaning, 466 participants were available for the main analyses (recorded vs. self-reported phone use after 6 months). Results: Participants were on average 18.6 years old (IQR 15.2-21.8 years). The Spearman correlation coefficients between recorded and self-reported (after 6 months) number and duration of voice calls were 0.68 and 0.65, respectively. Number of calls was on average underestimated by the participants (adjusted geometric mean ratio (GMR) self-report/recorded = 0.52, 95% CI = 0.47-0.58), while duration of calls was overestimated (GMR=1.32, 95%, CI = 1.15-1.52). The ratios significantly differed by country, age, maternal educational level, and level of reported phone use, but not by time of the interview (6 vs. 18 months). Individuals who reported low mobile phone use underestimated their use, while individuals who reported the highest level of phone use were more likely to overestimate their use. Individuals who reported using the phone mainly on the right side of the head used it more on the right (71.1%) than the left (28.9%) side. Self-reported left side users, however, used the phone only slightly more on the left (53.3%) than the right (46.7%) side. Recorded percentage hands-free use (headset, speaker mode, Bluetooth) increased with increasing self-reported frequency of hands-free device usage. Frequent (≥50% of call time) reported headset or speaker mode use corresponded with 17.1% and 17.2% of total call time, respectively, that was recorded as hands-free use. Discussion: These results indicate that young people can recall phone use moderately well, with recall depending on the amount of phone use and participants’ characteristics. The obtained information can be used to calibrate self-reported mobile use to improve estimation of radiofrequency exposure from mobile phones. © 2018 Elsevier Inc.

Single photon emission is investigated for fast radiative quantum dots. A simple model including capture process shows that the probability that a second photon is emitted increases when decreasing the exciton radiative lifetime. This effect is experimentally demonstrated through photon correlation measurements on single GaAs quantum dots presenting various radiative lifetime. The same model is used to estimate the second order autocorrelation function for an InAs quantum dot experiencing strong Purcell effect. The calculation shows the limitations of using Purcell effect to realize efficient single photon sources. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

To demonstrate strong coupling regime for a single quantum dot inside an optical microcavity, large oscillator strength quantum dots are needed. We show that quantum dots formed by the interface fluctuations of a thin GaAs quantum well are ideal systems for this purpose since they can present an oscillator strength larger than 100. By inserting a GaAs QD inside a state of the art microdisk microcavity, we demonstrate the strong coupling regime with a Rabi splitting of 400 μeV.

We report the observation of the strong coupling regime between a single GaAs quantum dot exciton and a microdisk optical mode. Microphotoluminescence is performed at various temperatures between 4 K and 50 K to tune the exciton through the cavity mode. An anticrossing is observed at 30 K with a Vacuum Rabi splitting of 400 ¹eV, twice as large as the individual linewidths. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on temperature dependent photoluminescence measurements on single monolayer fluctuation GaAs/AlGaAs quantum dots. At low temperature, the exciton lineshape deviates from the expected Lorentzian profile, with the appearance of asymmetric acoustic phonon sidebands. The temperature dependence of the exciton lineshape and its asymmetry, are very well accounted by a model describing the non-perturbative coupling with acoustic phonons. The effect of confinement on these phonon sidebands is finally adressed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on photoluminescence measurements on single GaAs monolayer fluctuation quantum dots. We show that, because the quantum dots have short radiative lifetime, the biexciton line is composed of various contributions originating from the Coulomb interaction with higher energy excitons. This appears as a broad low energy sideband on the biexciton line which appears for an average number of excitons in the system as small as 0.3. A simple model allows us to account for our observations and to show that this sideband is the spectral signature of fast quantum dots in continuous wave measurements.

We report on the observation of the strong-coupling regime between the excitonic transition of a single GaAs quantum dot and a discrete optical mode of a microdisk microcavity. Photoluminescence is performed at various temperatures to tune the quantum dot exciton with respect to the optical mode. At resonance, we observe a clear anticrossing behavior, signature of the strong-coupling regime. The vacuum Rabi splitting amounts to 400 microeV and is twice as large as the individual linewidths.

We report on photoluminescence on single GaAs quantum dots. We show that, because the quantum dots have short radiative lifetime, the biexciton line is composed of various contributions originating from the Coulomb interaction with higher energy excitons. This appears as a broad low energy sideband on the biexciton line, that appears whenever the biexciton is observed. A simple model allows us to account for our observations and to show that this sideband is the spectral signature of ultra fast quantum dots in continuous wave measurements.

We report on the observation of asymmetric phonon sidebands on both the exciton and biexciton emission lines in single GaAs monolayer fluctuation quantum dots. The contribution of phonon sidebands to the emission line is larger for the biexciton than for the exciton. We model the exciton line shape by means of a nonperturbative coupling with acoustic phonons and show that energetic confinement is an important clue to understand why phonon sidebands are sometimes observed and sometimes not. Finally, we discuss the extension of our model to the biexciton case.

The primary risk factor for bladder cancer is cigarette smoking. Using a combined analysis of 11 case-control studies, we have accurately measured the relationship between cigarette smoking and bladder cancer in men. Available smoking information on 2,600 male bladder cancer cases and 5,524 male controls included duration of smoking habit, number of cigarettes smoked per day and time since cessation of smoking habit for ex-smokers. There was a linear increasing risk of bladder cancer with increasing duration of smoking, ranging from an odds ratio (OR) of 1.96 after 20 years of smoking (95% confidence interval [CI] 1.48-2.61) to 5.57 after 60 years (CI 4.18-7.44). A dose relationship was observed between number of cigarettes smoked per day and bladder cancer up to a threshold limit of 15-20 cigarettes per day, OR = 4.50 (CI 3.81-5.33), after which no increased risk was observed. An immediate decrease in risk of bladder cancer was observed for those who gave up smoking. This decrease was over 30% after 1-4 years, OR = 0.65 (0.53-0.79), and was over 60% after 25 years of cessation, OR = 0.37 (0.30-0.45), However, even after 25 years, the decrease in risk did not reach the level of the never-smokers, OR = 0.20. (0.17-0.24). The proportion of bladder cancer cases attributable to ever-smoking was 0.66 (0.61-0.70) for all men and 0.73 (0.66-0.79) for men younger than 60. These estimates are higher than previously calculated. Int. J. Cancer 86: 289-294, 2000. (C) 2000 Wiley-Liss, Inc.

Photon correlation measurements are performed on single GaAs quantum dots with various excitonic radiative lifetimes. A continuous increase of the probability that the quantum dot emits more than one photon per excitation pulse is observed when decreasing the exciton radiative lifetime. The authors show that this increase is due to recapture processes into the quantum dot. A model for the second-order autocorrelation function including relaxation processes is developed and gives good description of the experimental observations.

We report on time resolved measurements on single monolayer fluctuation GaAs quantum dots. We measure radiative lifetimes as short as 100 ps for the exciton. Studying various single quantum dots, we demonstrate that the radiative lifetime of the exciton is controlled by the quantum dot lateral size.