Development of a Dew-Point Generator for Gases Other than Air and Nitrogen and Pressures up to 6?MPa

A new primary humidity standard is currently being developed at VSL that, in addition to ordinary operation with air and nitrogen at atmospheric pressure, can be operated also with special carrier gases such as natural gas and SF₆ and at pressures up to 6?MPa. In this paper, the design and construction of this new primary dew-point generator and the preliminary tests performed on the generator are reported. The results of the first efficiency tests, performed for the dew-point temperature range from ?50?°C to 20°C, for pressures up to 0.7MPa and for carrier gas flow rates up to 4L·?min^?1, showed satisfactory generator performance when used in the single-pass mode, i.e., with no recirculation of the carrier gas.     

Investigation of the Equivalence of National Dew-Point Temperature Realizations in the ?50?°C to +?20?°C Range

In the field of humidity quantities, the first CIPM key comparison, CCT-K6 is at its end. The corresponding European regional key comparison, EUROMET.T-K6, was completed in early 2008, about 4?years after the starting initial measurements in the project. In total, 24 NMIs from different countries took part in the comparison. This number includes 22 EURAMET countries, and Russia and South Africa. The comparison covered the dew-point temperature range from ?50?°C to +20?°C. It was carried out in three parallel loops, each with two chilled mirror hygrometers as transfer standards in each loop. The comparison scheme was designed to ensure high quality results with evenly spread workload for the participants. It is shown that the standard uncertainty due to the long-term instability was smaller than 0.008?°C in all loops. The standard uncertainties due to links between the loops were found to be smaller than 0.025?°C at ?50?°C and 0.010?°C elsewhere. Conclusions on the equivalence of the dew-point temperature standards are drawn on the basis of calculated bilateral degrees of equivalence and deviations from the EURAMET comparison reference values (ERV). Taking into account 16 different primary dew-point realizations and 8 secondary realizations, the results demonstrate the equivalence of a large number of laboratories at an uncertainty level that is better than achieved in other multilateral comparisons so far in the humidity field.     

Uncertainties in the fate of nitrogen I: An overview of sources of uncertainty illustrated with a Dutch case study

This study focuses on the uncertainties in the fate of nitrogen (N) in the Netherlands. Nitrogen inputs into the Netherlands in products, by rivers, and by atmospheric deposition, and microbial and industrial fixation of atmospheric N₂ amount to about 4450 Gg N y^–1. About 60% of this N is transported out of the Netherlands in products. The fate of the remaining 40%, however, is less clear. We discuss uncertainties in losses to the atmosphere (as ammonia or through denitrification), by leaching and runoff, and in N accumulation in biomass and soils. These processes may account for the fate of about 40% of the N in the Netherlands, and for the fate of about 60% of the N in Dutch agricultural soils. Reducing uncertainties in the estimates of these fluxes is necessary for reducing the impact of excess N in the environment. In particular, monitoring the environmental effects of ammonia emissions and nitrate leaching to groundwater and aquatic systems requires an increased understanding of the fate of N. Uncertainties arise because (1) some N fluxes cannot be measured directly and are usually quantified indirectly as the balance in N budgets, (2) direct measurements of N fluxes have inevitable inaccuracies, (3) lack of experimental data and other information (e.g. statistics) needed for upscaling, (4) large spatial and temporal variability of fluxes, and (5) poor understanding of the processes involved. These uncertainties can be reduced by additional experimental studies and by further development of process-based models and N budget studies. We prioritize these future research needs according to a range of different criteria.     

Canonical bases for cyclotomic fields

It is shown how the use of a certain integral basis for cyclotomic fields enables one to perform the basic operations in their ring of integers efficiently. In particular, from the representation with respect to this basis, one obtains immediately the smallest possible cyclotomic field in which a given sum of roots of unity lies. This is of particular interest when computing with the ordinary representations of a finite group.1980 Mathematics subject classification (1985): 11R, 11Y     

Contribution of job control and other risk factors to social variations in coronary heart disease incidence

BACKGROUND: The first Whitehall Study showed an inverse social gradient in mortality from coronary heart disease (CHD) among British civil servants--namely, that there were higher rates in men of lower employment grade. About a quarter of this gradient could be attributed to coronary risk factors. We analysed 5-year CHD incidence rates from the Whitehall II study to assess the contribution to the social gradient of psychosocial work environment, social support, coronary risk factors, and physical height. METHODS: Data were collected in the first three phases of examination of men and women in the Whitehall II study. 7372 people were contacted on all three occasions. Mean length of follow-up was 5.3 years. Characteristics from the baseline, phase 1, questionnaire, and examination were related to newly reported CHD in people without CHD at baseline. Three self-reported CHD outcomes were examined: angina and chest pain from the Rose questionnaire, and doctor-diagnosed ischaemia. The contribution of different factors to the socioeconomic differences in incident CHD was assessed by adjustment of odds ratios. FINDINGS: Compared with men in the highest grade (administrators), men in the lowest grade (clerical and office-support staff) had an age-adjusted odds ratio of developing any new CHD of 1.50. The largest difference was for doctor-diagnosed ischaemia (odds ratio for the lowest compared with the highest grade 2.27). For women, the odds ratio in the lowest grade was 1.47 for any CHD. Of factors examined, the largest contribution to the socioeconomic gradient in CHD frequency was from low control at work. Height and standard coronary risk factors made smaller contributions. Adjustment for all these factors reduced the odds ratios for newly reported CHD in the lowest grade from 1.5 to 0.95 in men, and from 1.47 to 1.07 in women. INTERPRETATION: Much of the inverse social gradient in CHD incidence can be attributed to differences in psychosocial work environment. Additional contributions were made by coronary risk factors--mainly smoking--and from factors that act early in life, as represented by physical height.     

Job control, personal characteristics, and heart disease

A new anthropometric landmark of the face, called the maxillozygion (mz; right, left) is presented. The bilateral landmark is the most prominent point of the maxillozygomatic suture line, identified by palpation of the most anterior protruding contours on the frontal aspect of the face, located below the lateral third of the right and left bony orbits. The reliability of locating the landmark on both sides of the face by palpation is discussed. Preliminary data determining the position of the maxillozygion in the vertical, sagittal, and horizontal planes in white and Asian sample populations is presented. In general, the Asian face tends to be the same width (zygion [zy]-zy) as the white face; however, the maxillozygion is located more laterally on the Asian face compared with the white face.     

Fish as models for the neuroendocrine regulation of reproduction and growth

Models are essential for the full understanding of neuroendocrine control processes. In this regard fish offer a rich source of biological material. They have diverse growth and reproductive strategies, inhabiting most of the Earth's aquatic ecological niches. Fish possess many of the common vertebrate features but also offer several unique aspects to allow the biologist easy access to the study of hypothalamic and pituitary function. Several key examples of how teleosts, or the bony fish, can offer insight into fundamental mechanisms of vertebrate sex differentiation, growth and reproduction are reviewed.