Air contaminants in a submarine equipped with air independent propulsion.

The Swedish Navy has operated submarines equipped with air independent propulsion for two decades. This type of submarine can stay submerged for periods far longer than other non-nuclear submarines are capable of. The air quality during longer periods of submersion has so far not been thoroughly investigated. This study presents results for a number of air quality parameters obtained during more than one week of continuous submerged operation. The measured parameters are pressure, temperature, relative humidity, oxygen, carbon dioxide, hydrogen, formaldehyde and other volatile organic compounds, ozone, nitrogen dioxide, particulate matter and microbiological contaminants. The measurements of airborne particles demonstrate that air pollutants typically occur at a low baseline level due to high air exchange rates and efficient air-cleaning devices. However, short-lived peaks with comparatively high concentrations occur, several of the sources for these have been identified. The concentrations of the pollutants measured in this study do not indicate a build-up of hazardous compounds during eight days of submersion. It is reasonable to assume that a substantial build-up of the investigated contaminants is not likely if the submersion period is prolonged several times, which is the case for modern submarines equipped with air independent propulsion.

Precision spectroscopy of hydrogen and femtosecond laser frequency combs.

Precision spectroscopy of the simple hydrogen atom has inspired dramatic advances in optical frequency metrology: femtosecond laser optical frequency comb synthesizers have revolutionized the precise measurement of optical frequencies, and they provide a reliable clock mechanism for optical atomic clocks. Precision spectroscopy of the hydrogen 1S-2S two-photon resonance has reached an accuracy of 1.4 parts in 10(14), and considerable future improvements are envisioned. Such laboratory experiments are setting new limits for possible slow variations of the fine structure constant alpha and the magnetic moment of the caesium nucleus mu(Cs) in units of the Bohr magneton mu(B).

Reference wavelengths for strong lines of atomic hydrogen and deuterium.

Wavelengths of the individual fine-structure components of the n = 1-2 (Ly(alpha)), n = 1-3 (Ly(beta)), n = 1-4 (Ly(gamma)), n = 1-5 (Ly(delta)), n = 1-6 (Ly(epsilon)), n = 1-7 (Ly(zeta)), n = 2-3 (H(alpha)), n = 2-4 (H(beta)), n = 2-5 (H(gamma)), n = 2-6 (H(delta)), and n = 2-7 (H(epsilon)) transitions of H and D are determined from theoretical values for the binding energies. Theoretical line strengths are used to obtain recommended values for the peaks of unresolved blends of these components as likely to be observed with discharge light sources and spectrometers with low to moderate resolution.

Referencing strategies and techniques in stable isotope ratio analysis.

Stable isotope ratios are reported in the literature in terms of a deviation from an international standard (delta-values). The referencing procedures, however, differ from instrument to instrument and are not consistent between measurement facilities. This paper reviews an attempt to unify the strategy for referencing isotopic measurements. In particular, emphasis is given to the importance of identical treatment of sample and reference material ('IT principle'), which should guide all isotope ratio determinations and evaluations. The implementation of the principle in our laboratory, the monitoring of our measurement quality, the status of the international scales and reference materials and necessary correction procedures are discussed.