The Impact of Grain Boundary Diffusion on the Low Temperature Reoxidation Mechanism in Nanocrystalline TiO2−δ Films

The redox reaction TiO₂ TiO_2- + /2O_2(gas) can modify the oxygen deficiency and electrical conductivity of TiO_2– upon changing the ambient oxygen pressure. It is found that in nanocrystalline films this leads to significant changes in even at relatively low temperatures (200–325°C) that were previously considered too low to modify TiO₂ defect chemistry. This unusual phenomenon is attributed to the fine-grained structure and the important role of grain boundary (GB) diffusion in these films. A phenomenological model of the low temperature redox mechanism in nanocrystalline TiO_2– films is elaborated. Taking into account the impact of GB diffusion and considering time-dependent decay of the volume fraction of GB diffusion sites, we derive a modified parabolic law for the redox reaction kinetics. It is demonstrated that this law describes very well the electrical response kinetics of nanocrystalline TiO_2– thin films during exposure to oxygen between 200 and 325°C. From the fitting between the experimental results and this formula the activation energy of chemical diffusion in TiO_2– bulk and GBs is evaluated, obtaining 0.69 and 0.52 eV, respectively.     

Annoyance and self-reported sleep disturbances due to structurally radiated noise from railway tunnels

In Norway, the requirement for structure borne noise from tunnels is L_pAFmax = 32 dB inside dwellings. According to the Norwegian Standard 8175 it is expected that up to 20% of the exposed population are disturbed by the noise at this level. However, the scientific basis for this noise limit is poor. The aim of this study was to determine the degree of annoyance and self-reported sleep disturbances as a function of L_pAFmax. In the present study, 521 dwellings exposed to structural sound from railway rock-tunnels were identified. A questionnaire was sent to one randomly selected person above 18 years of age from each dwelling. The results showed that both noise induced annoyance and reported sleep disturbances were significantly related to L_pAFmax. Other factors that increased the annoyance were high pass-by frequency of freight trains per day, and degree of sound insulation of the windows. At L_pAFmax = 32 dB, 20% were slightly or more than slightly annoyed, and 4% were moderately or more than moderately annoyed. According to the pre-existing assumption that up to 20% of the exposed population are disturbed by the noise at this level, the present results give support to the Norwegian noise limit L_pAFmax = 32 dB inside dwellings of structure borne noise from railway tunnels.     

On the stability of steady states in a granuloma model

We consider a free boundary problem for a system of two semilinear parabolic equations. The system represents a simple model of granuloma, a collection of immune cells and bacteria filling a 3-dimensional domain Ω(t)$\Omega (t)$ which varies in time. We prove the existence of stationary spherical solutions and study their linear asymptotic stability as time increases to infinity.     

Molecular assessment of UVC radiation-induced DNA damage repair in the stromatolitic halophilic archaeon, Halococcus hamelinensis

The halophilic archaeon Halococcus hamelinensis was isolated from living stromatolites in Shark Bay, Western Australia, that are known to be exposed to extreme conditions of salinity, desiccation, and UV radiation. Modern stromatolites are considered analogues of very early life on Earth and thus inhabitants of modern stromatolites, and Hcc. hamelinensis in particular, are excellent candidates to examine responses to high UV radiation. This organism was exposed to high dosages (up to 500 J/m(2)) of standard germicidal UVC (254 nm) radiation and overall responses such as survival, thymine-thymine cyclobutane pyrimidine dimer formation, and DNA repair have been assessed. Results show that Hcc. hamelinensis is able to survive high UVC radiation dosages and that intact cells give an increased level of DNA protection over purified DNA. The organism was screened for the bacterial-like nucleotide excision repair (NER) genes uvrA, uvrB, uvrC, as well as for the photolyase phr2 gene. All four genes were discovered and changes in the expression levels of those genes during repair in either light or dark were investigated by means of quantitative Real-Time (qRT) PCR. The data obtained and presented in this study show that the uvrA, uvrB, and uvrC genes were up-regulated during both repair conditions. The photolyase phr2 was not induced during dark repair, yet showed a 20-fold increase during repair in light conditions. The data presented is the first molecular study of different repair mechanisms in the genus Halococcus following exposure to high UVC radiation levels.