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[en] The chemi-ionization rate coefficients of La, Pr, Tb, and Ho with O have been measured from 200 to 450 K using a thermalized flow tube apparatus. Both La and Tb were found to react near the calculated hard sphere collision limit, while the Pr and Ho reactions proceeded at roughly 40% of that limit at all temperatures. The efficiencies of these reactions are considered and the near thermoneutral character of the reaction with Ho can explain this case, whereas an explanation for the inefficiency of the Pr reaction remains elusive. The chemi-ionization reaction of La with N2O was also studied and found to proceed roughly 2 orders of magnitude slower than the competing neutral oxidation pathway. The latter result disagrees with previous literature reports.
[en] The form and reproducibility of pantographic tracings under the influence of relaxant drugs and in patients with muscle dysfunction and TMJ disorders, tend to emphasize the dominance of the neuromuscular factors. The purpose of this study was to demonstrate the effect of nitrous oxide induced psychosedation, on the reproducibility of pantographic tracings of border movements of the mandible. This study included four male subjects (with no signs and symptoms of muscular dysfunction and temporomandibular joint problems). Operator guided border tracings were recorded using the Denar pantograph. Three sets of tracings were recorded: (1) three tracings prior to sedation (Tracing I); (2) one tracing prior to sedation and two after sedation (Tracing II); (3) three tracings after psychosedation (Tracing III). The coincidence of tracings I, II, and 111 were statistically analyzed applying the chi-square (X2) analysis. There was a significant difference in the coincidence of tracings between Tracings 1 and II (X2 = 14.892). There was no significant difference in the coincidence of tracings between Tracings I and III (X2 = 1.338). This suggests that nitrous oxide psychosedation produces a centrally induced relaxation of the musculature, by possibly eliminating the extraneous anxiety producing factors. (author)
[en] The results of the time series analysis of N2O concentration in the urban atmosphere, taken between 1 January and 31 December 1996 at Nagoya University are presented here. A power spectrum obtained by an FFT (Fast Fourier Transform) roughly shows a 1/f dependence, except for several particular periodic irregularities. One of these is a group of several peaks, quasi-periodic in structure, spreading over a three day (2-5 days) time span. In order to search for periodic trends more clearly, a folding method in the frequency range equivalent to a 1-10 day period was tested. Consequently, a significant periodicity at 1 day with a small amplitude (∼1%) was observed. A minimum and a maximum appeared at around 9 a.m. and 9 p.m., which suggests a correlation with human activities. On the other hand, the primary reasons for high N2O concentrations, with an amplitude of >10% in the atmosphere, are rather due to meteorological processes, such as wind or rain in the urban environment, and possibly the Heat-Island effect during the summer season. (author)
[en] N2O emissions were investigated at two sites in the Swiss Alps, Alptal (SZ) and Piora Valley (TI), using the closed, vented chamber method during the snow-free period and the snowpack diffusion method during snow cover. Significant spatial variations in surface N2O effluxes between different sampling subsites were observed in both summer and winter. While in winter N2O fluxes from a raw humus site in Alptal and from a site of neutral pH in the Piora Valley were very low (0.01-0.02 mg N2O-N/m2/d) and similar to other published values, N2O emissions for acidic and alder-covered sites were 0.3-0.4mg N2O-N/m2/d and reached 1.7-1.9 mg N2O-N/m2/d for nutrient-rich sites. This suggests that the soil temperatures close to the freezing point were not limiting microbial activity under snow. Snow-covered soils are insulated from extreme air temperatures and stay constant between -0. 3 and -1 deg C. They represent an environment where micro-organisms may remain active while vegetation is dormant. N2O liberation is repressed at neutral and raw humus sites, as nitrification is the main source of N2O. During summer the soil microbial activity is strongly related to water availability and temperature: in contrast, in winter both factors are rather constant and the controlling factors of heterotrophic activity are unknown. Our data show that N2O is a significant component of alpine N cycling and that winter N2O fluxes should not be neglected in the calculation of the annual budget for alpine ecosystems, considering that snow covers (sub-) alpine regions for a large part of the year
[en] In this paper, three unregulated components, ammonia, nitrous oxide and hydrogen cyanide, emitted from five passenger vehicles are investigated. With focus upon emission factors from existing production technology, vehicles produced between 1989 and 1998 with considerable mileage (7000 to 280,000) are chosen. Among the five vehicles, four were sold in the European market, whereas one was sold in the US market. The vehicles are tested on a chassis dynamometer. An EU2000 Driving Cycle (NEDC) and a US Urban Driving Cycle (UDC) of the Federal Test Procedure 75 (FTP-75) are used in the study. The regulated emissions are measured using a Horiba Mexa series. Unregulated emissions, ammonia (NH3), nitrous oxide (N2O) and hydrogen cyanide (HCN) are analysed by mass spectrometer, gas chromatography and CNT-NA, TIM315-74W method, respectively. Both the unregulated emissions and the regulated emissions show driving cycle dependency; and they are also improved with newer vehicle and emission control technology. However, a gasoline direct injection vehicle (relatively new technology in this study) has rather high regulated emissions, whereas the NH3, N2O and HCN emissions are low