The use of mouthguards in contact sports effectively prevents oral injury and preserves oral structures. We investigated oral injuries and awareness concerning mouthguards among Japanese high school soccer and rugby players. Athletes were asked a series of questions concerning their history of oral injury while participating in sports, and their pattern of mouthguard use was determined. The data were evaluated statistically using chi-square analysis. The incidence of oral injuries was 32.3% for soccer athletes and 56.5% for rugby athletes, with 0.8% and 24.1% of the respective groups having mouthguards. There were significant differences between the soccer and rugby groups (P < 0.001). Although 81.8% of soccer athletes thought mouthguards were unnecessary, only 26.2% of rugby athletes shared this opinion and there was a significant difference between the soccer and rugby groups. Many soccer athletes had insufficient knowledge about mouthguards and were not concerned about preventing oral injury, although it was in fact a common problem in their sport. Athletes as well as coaches must be made aware of the high risk of oral injury when playing soccer, rugby, and other contact sports.

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H-D exchange was observed in the methyl group during the formation of sulfones in the reaction of dimethyl sulfide-d 6 or thioanisole-R,R,R-d 3 with singlet oxygen in aprotic solvents. No exchange was observed in the sulfoxides obtained. The proton in the sulfones was shown to come from adventitious water, since the oxidation of C 6 H 5 SCH 3 in the presence of D 2 O lead to the formation of sulfones with monodeuteriation. The 16 O 2 -18 O 2 tracer study demonstrated no oxygen scrambling in the sulfones. All the results indicate that the sulfones are formed intramolecularly via an intermediate possessing one activated proton exchangeable with trace water, a suggested structure for which is S-hydroperoxysulfonium ylides (RS + (OOH)CH 2 -). Kinetic isotope effects (k H /k D ) 2-4) observed for methyl protons in the sulfone formation suggest that the rate-determining step is the intramolecular proton abstraction in the persulfoxides (RS + (OO -)CH 3 ) generating S-hydroperoxysulfonium ylides. The conversion of the ylide intermediates to sulfones is shown to be facile on the basis of PM3 theoretical calculations.

Optical reflectivity spectra of La 1−x Sr x MnO 3 (0≤x≤0.30) were measured on cleavage surfaces of single crystals. The optical conductivity σ(ω) of ferromagnetic-metal La 0.70 Sr 0.30 MnO 3 is characterized by a Drude-like − but not simple-Drude − component with large spectral weight below ∼1.6 eV, which yields a large effective carrier number N * eff consistent with the results of Hall coefficient and specific heat measurements. The present result demonstrates that the previous result of "small Drude weight" originates from the damage of the sample surface. The Sr-substitution effect on the electronic structure and the origin of the unconventional σ(ω) are also discussed. PACS numbers: 71.27.+a, 71.30.+h, 78.30.−j Typeset using REVT E X 1 The motivation of the renewed interest in the double-exchange ferromagnetic-metal manganites has two − fundamental and practical − aspects: study on anomalous metallic phase near Mott transition and industrial application of the intriguing phenomena induced by a magnetic field such as "colossal" magnetoresistance (CMR) [1]. Optical reflectivity study can make an essential role in the both stages because it enables us to not only deduce dielectric function but also examine separately two key-elements of charge transport − carrier density (or Drude weight) and scattering time. The charge transport is one of the central concerns among the both fields. The previous reflectivity studies on La 1−x A x MnO 3 (A = Sr [2], Ca [3-5]) have revealed the outline of the systematic change of the electronic structure with Sr(Ca)-substitution and the conspicuous transfer of spectral weight over a wide energy range of 0-3 eV accompanied by the spin polarization of conducting e g electrons. However, a quantitative conclusion is difficult to be drawn on the far-infrared response and on the estimation of optical (dielectric) functions because the experiments were made using polycrystals or/and did not cover the sufficient energy region. Especially, the origin or truth of "small Drude weight" − pointed out by Okimoto et al. [2] but contradictory to the results of Hall coefficient [6], specific heat [7,8], and optical absorption studies [9] − is still not well-investigated. We report the optical reflectivity spectra R(ω) of La 1−x Sr x MnO 3 (0≤x≤0.30) measured on the cleavage surfaces of single crystals for a wide energy range covering far-infrared(far-IR) region down to 5 meV. Our careful experiment enables us to obtain the established optical functions − optical conductivity σ(ω) and Drude weight − for this prototypical double-exchange system. Especially the Drude weight estimated for x=0.30 is large and consistent with the results of Hall effect and specific heat studies.Single crystals of La 1−x Sr x MnO 3 were grown by a floating zone method. The details of the growth condition and characterization were described elsewhere [10]. In order to obtain defect-free surfaces we cleaved the single-crystalline rod. The typical size of the cleavage surface was 0.2 mm×0.2 mm, which was sufficient for opt...

The formation of dimer radical cations from aromatic sulfides has been studied by photochemical one-electron oxidation in acetonitrile. When dicyanonaphthalene and thioanisole in acetonitrile were irradiated with nanosecond laser flash (308 nm), two types of dimer radical cations were detected at 470 and 800 nm at the expense of the monomer radical cation (520 nm). The intramolecular formation of similar radical ion complexes was observed for the cases of 1,n-bis(phenylthio)alkanes with n ) 3 and 4, while bissulfides with n ) 2, 6, and 8 showed radical cation spectra quite different from the above cases of n ) 3 and 4. These facts indicate that dimer radical cations absorbing at around 460-500 nm are assigned as the σ-type complex of the sulfur-sulfur three-electron bond and that radical cations absorbing at around 800 nm are of the π-type complex associated with two phenylthio groups. For the case of p-methylthioanisole the formation of π-type dimer was shown to be reduced owing to the steric hindrance of two methyl groups. No formation of dimer radical cations was observed for cases of p-methoxythioanisole and diphenyl sulfide where the corresponding monomer radical cations are stabilized by the delocalization of positive charge on the sulfur atom. The density functional BLYP/6-31G* calculations on thioanisole predicted the existence of σand π-type dimer radical cations, in accordance with the experimental observation of approximately equal stability.