The effect of flight line spacing on radioactivity inventory and spatial feature characteristics of airborne gamma-ray spectrometry data

Airborne Gamma Spectrometry (AGS) is well suited to the mapping of radioactivity in the environment. Flight parameters (e.g. speed and line spacing) directly affect the rate of area coverage, cost, and data quality of any survey. The influences of line spacing have been investigated for data from inter‐tidal, coastal and upland environments with a range of <sup>137</sup>Cs activity concentrations and depositional histories. Estimates of the integrated <sup>137</sup>Cs activity (‘inventory’) within specified areas and the shapes of depositional features were calculated for subsets of the data at different line spacings. Features with dimensions greater than the line spacing show variations in inventory and area of less than 3%, and features with dimensions less than the line spacing show larger variations and a decreased probability of detection. The choice of line spacing for a task is dependent on the dimensions of the features of interest and required edge definition. Options for line spacing for different tasks are suggested. It is noted that for regional mapping, even 5–10 km line spacing can produce useful data

Histidine nutrition and genotype affect cataract development in Atlantic salmon, Salmo salar L.

The aim of this study was to investigate effects of dietary levels of histidine (His) and iron (Fe) on cataract development in two strains of Atlantic salmon monitored through parr-smolt transformation. Three experimental diets were fed: (i) a control diet (CD) with 110 mg kg-1 Fe and 11.7 g kg-1 His; (ii) CD supplemented with crystalline His to a level of 18 g kg-1 (HD); and (iii) HD with added iron up to 220 mg kg-1 (HID). A cross-over design, with two feeding periods was used. A 6-week freshwater (FW) period was followed by a 20-week period, of which the first three were in FW and the following 17 weeks in sea water (SW). Fish were sampled for weighing, cataract assessment and tissue analysis at five time points. Cataracts developed in all groups in SW, but scores were lower in those fed high His diets (P < 0.05). This effect was most pronounced when HD or HID was given in SW, but was also observed when these diets were given in FW only. Histidine supplementation had a positive effect on growth performance and feed conversion ratio (P < 0.05), whereas this did not occur when iron was added. Groups fed HD or HID had higher lens levels of His and N-acetyl histidine (NAH), the latter showing a marked increase post-smoltification (P < 0.05). The HD or HID groups also showed higher muscle concentrations of the His dipeptide anserine (P < 0.05). There was a strong genetic influence on cataract development in the CD groups (P < 0.001), not associated with tissue levels of His or NAH. The role of His and His-related compounds in cataractogenesis is discussed in relation to tissue buffering, osmoregulation and antioxidation

Influence of convective transport on tropospheric ozone and its precursors in a chemistry-climate model

The impact of convection on tropospheric O₃ and its precursors has been examined in a coupled chemistry-climate model. There are two ways that convection affects O₃. First, convection affects O₃ by vertical mixing of O₃ itself. Convection lifts lower tropospheric air to regions where the O₃ lifetime is longer, whilst mass-balance subsidence mixes O₃-rich upper tropospheric (UT) air downwards to regions where the O₃ lifetime is shorter. This tends to decrease UT O₃ and the overall tropospheric column of O₃. Secondly, convection affects O₃ by vertical mixing of O₃ precursors. This affects O₃ chemical production and destruction. Convection transports isoprene and its degradation products to the UT where they interact with lightning NO_x to produce PAN, at the expense of NO_x. In our model, we find that convection reduces UT NO_x through this mechanism; convective down-mixing also flattens our imposed profile of lightning emissions, further reducing UT NO_x. Over tropical land, which has large lightning NO_x emissions in the UT, we find convective lofting of NO_x from surface sources appears relatively unimportant. Despite UT NO_x decreases, UT O₃ production increases as a result of UT HO_x increases driven by isoprene oxidation chemistry. However, UT O₃ tends to decrease, as the effect of convective overturning of O₃ itself dominates over changes in O₃ chemistry. Convective transport also reduces UT O₃ in the mid-latitudes resulting in a 13% decrease in the global tropospheric O₃ burden. These results contrast with an earlier study that uses a model of similar chemical complexity. Differences in convection schemes as well as chemistry schemes &ndash; in particular isoprene-driven changes are the most likely causes of such discrepancies. Further modelling studies are needed to constrain this uncertainty range

Barriers to the use of a diagnostic oral microbiology laboratory by general dental practitioners

OBJECTIVE: To identify barriers on the use of diagnostic microbiology facilities in general dental practice. DESIGN: A cross-sectional survey using a postal questionnaire. SETTING: Primary/secondary care interface between the diagnostic oral microbiology laboratory, University of Glasgow Dental Hospital and School, Glasgow and dental practitioners within the surrounding health boards, 1998. SUBJECTS: All GDPs (797) within Argyll and Clyde, Ayrshire and Arran, Lanarkshire and Greater Glasgow Health Boards. MAIN OUTCOME MEASURES: The responses were expressed as both absolute and relative frequencies. RESULTS: Responses were received from 430 (55%). The most frequent reason for failure to use the service was lack of information, with more than half of the respondents claiming to be unaware of the facility. Lack of request forms and sampling equipment were also viewed as barriers to using the service. CONCLUSIONS: The laboratory is failing to successfully communicate its role in addressing the growing burden of antibiotic resistance in the community and must be more proactive in encouraging appropriate use and increasing accessibility of the service to GDPs

2MASS J06164006-6407194: The First Outer Halo L Subdwarf

We present the serendipitous discovery of an L subdwarf, 2MASS J06164006-6407194, in a search of the Two Micron All Sky Survey for T dwarfs. Its spectrum exhibits features indicative of both a cool and metal poor atmosphere including a heavily pressured-broadened K I resonant doublet, Cs I and Rb I lines, molecular bands of CaH, TiO, CrH, FeH, and H2O, and enhanced collision induced absorption of H2. We assign 2MASS 0616-6407 a spectral type of sdL5 based on a comparison of its red optical spectrum to that of near solar-metallicity L dwarfs. Its high proper motion (mu =1.405+-0.008 arcsec yr-1), large radial velocity (Vrad = 454+-15 km s-1), estimated uvw velocities (94, -573, 125) km s-1 and Galactic orbit with an apogalacticon at ~29 kpc are indicative of membership in the outer halo making 2MASS 0616-6407 the first ultracool member of this population.Comment: Accepted for publication in Ap

Following basal stem rot in young oil palm plantings

The PCR primer GanET has previously been shown to be suitable for the specific amplification of DNA from Ganoderma boninense. A DNA extraction and PCR method has been developed that allows for the amplification of the G. boninense DNA from environmental samples of oil palm tissue. The GanET primer reaction was used in conjunction with a palm-sampling programme to investigate the possible infection of young palms through cut frond base surfaces. Ganoderma DNA was detected in frond base material at a greater frequency than would be expected by comparison with current infection levels. Comparisons are made between the height of the frond base infected, the number of frond bases infected, and subsequent development of basal stem rot. The preliminary results suggest that the development of basal stem rot may be more likely to occur when young lower frond bases are infected