A comparison of the reproducibility of the parameters of the 13C-aminopyrine breath test for the assessment of hepatic function

This study determined the within-subject and between-subject variability of different ways of expressing the results of the ¹³C-aminopyrine breath test (¹³C-ABT) and the effect of shortening the test duration. The ¹³C-ABT was conducted on three separate occasions in 10 healthy volunteers and on a single occasion in 22 patients with established liver cirrhosis. The within-subject variability of cumulative percentage dose recovered (cPDR), using measured CO₂ production rate (VCO₂), in the reference group over three trials was 15% over 120 min. Higher within-subject variability in cPDR would have been evident if the test was terminated at either 30 or 60 min. Substitution of predicted VCO₂ to calculate cPDR yielded comparable values at all time points. Significant differences between cirrhotics and reference group were evident after just 10 min using PDR/h, cPDR or enrichment (all P<0.05). The ABT demonstrates clinically acceptable reproducibility. Shortening of the duration may make the test more acceptable clinically, but it is associated with increasing imprecision.     

Entropy and disorder

A discussion is given of some aspects of the relation between concepts of entropy and intuitive qualitative ideas concerning ‘disorder’.

In this connection, a plea is mado for moderation in the use of such idess in teaching. In particular: (i) They ought not to be so misused as to obscure the status of S as a quantity which can be treated in a purely macroscopic theory. (ii) They do not exhibit a complete correspondence with the concepts of a quantitative treatment on the molecular level.     

Mass‐in‐mass lattices with small internal resonators

We consider the mass‐in‐mass (MiM) lattice when the internal resonators are very small. When there are no internal resonators the lattice reduces to a standard Fermi‐Pasta‐Ulam‐Tsingou (FPUT) system. We show that the solution of the MiM system, with suitable initial data, shadows the FPUT system for long periods of time. Using some classical oscillatory integral estimates we can conclude that the error of the approximation is (in some settings) higher than one may expect.     

Comparisons of ground level measurements of ion concentration and potential gradient upwind and downwind of HV power lines in corona

Simultaneous ion concentration and potential gradient measurements were made at AC high voltage power lines using ion mobility spectrometers and electric field mills. A significant (p < 0.01) change in central tendency and variability of ion concentration and potential gradient can occur downwind of power lines. In 3 out of 8 downwind measurements, there was a discrepancy of sign between the overall mean of these quantities, attributed to ion dispersion and ion–aerosol attachment. While ion concentrations give a greater indication of personal exposure, potential gradient measurements are more appropriate for assessment of the behaviour of a power line.     

Mem-models and state event location algorithm for a prototypical aerospace system

Nonlinear Dynamics - This paper presents a suite of dynamic models enhanced by mem-models. A prototypical pogo stick model might mimic a space hopper or a segmented telescope mirror actuator, while...     

Comparison of GOME-2 UVA Satellite Data to Ground-Based UVA Measurements in South Africa

Satellite estimates of surface ultraviolet A (UVA) (315–400 nm) from the Global Ozone Monitoring Experiment (GOME)-2 were compared to ground-based measurements at four stations in South Africa for 2015. The comparison of daily exposure and daily maximum irradiance was completed for all-sky and clear-sky conditions. There is a strong linear correlation between the satellite and ground-based data with a correlation coefficient (r) between 0.86 and 0.97 for all-sky conditions. However, at three of the stations the satellite data are underestimated compared to ground-based data with a mean bias error (MBE) between −8.7% and −20.6%. A seasonal analysis indicated that there is a link between the bias in ground-based and GOME-2 UVA and cloud fraction. Factors such as aerosols, surface albedo, altitude and data resolution may contribute to the underestimations found at the three sites. These results indicate that satellite estimates of surface UVA over South Africa do not exhibit the same behavior as other stations around the world and therefore require further validation.     

Influence of Surface Scratches on the Flexure Strength of Soda-Lime Silicate and Borosilicate Glass

Borosilicate (BS) and soda-lime silicate (SLS) glasses are being considered for use as the strike-face in transparent armor systems. This effort examined the effect of surface scratches generated with 1, 5, 10, and 30 N scratching loads on the equibiaxial flexure strength of both glasses including versions of each that had been thermally-tempered. At lower scratch loads there is more lateral cracking associated with the scratches in the BS while the scratches in the SLS predominantly exhibit plastic deformation. At the highest scratch load the damage is dominated by chips and lateral cracking within and along the scratch length. The tempered versions of the SLS appear to have less lateral cracking than the tempered version of the BS glass. In all instances the flexure strength decreases significantly when a 1 N scratch is introduced on the tin surface but when the scratch load increases any additional strength loss is minimal.