ALBERT

Notes: X-ray studies with femtosecond time resolution will become highly important within the next few years because of a confluence of scientific interest and availability of sources. This poses a challenge to instrumentation: Rapid switches and more elaborate devices for coherent control of x rays will have to be developed, and detectors will have to cope with high intensities and orders of magnitude better time resolution. Especially for detectors, a transition from classical electronics to optical control will become necessary to achieve few-femtosecond time resolution. The purpose of this article is to highlight a few of the challenges and to give a few examples of high-speed purely optical control and detection of x rays. © 2002 American Institute of Physics.

Notes: The lattice orientations near the interface of chemical vapor deposited diamond films on Si(001) have been studied by orientation imaging microscopy. This technique is based on the automated analysis of electron backscatter Kikuchi diffraction patterns. The electron beam has been scanned in discrete steps over the reverse side of the diamond film after having removed the substrate. The obtained data have allowed us to determine the texture and to visualize quantitatively the orientational arrangement of and among individual diamond crystallites in the near-interface region. A comparison with the orientation of the substrate has proved the existence of epitaxially nucleated grains. A high amount of twinned diamond has been deduced from the pole figures and verified by analysis of orientation correlations between neighboring crystallites. Moreover, the grain boundary maps have allowed us to monitor and quantify directly the occurring twin boundaries. © 1994 American Institue of Physics.

Notes: Polymorphism at five microsatellite genetic markers (genotyped n = 496) and mark-recapture tagging data (tagged n = 9813) were used to define the population structure of brook charr, Salvelinus fontinalis from the Indian Bay watershed, Newfoundland, Canada. Despite the absence of physical barriers to migration among lakes, both genetic and tagging data suggest that brook charr in each lake represent reproductively isolated populations. Exact tests comparing allele frequencies, θ (global value = 0·063), Rst (global value = 0·052), individual assignment tests, and Nei's genetic distance provided congruent estimates of population subdivision in agreement with the tagging data (only 2·2% of recaptures were lake-to-lake). The genetic structure of the brook charr populations corresponded with the geographic structure of the drainage basin on a qualitative level, although linear distance over water was not significantly correlated with the tagging data or the genetic distance measures. The agreement between the tagging and the genetic data suggest that microsatellite markers can be useful tools for defining real biological units. The results also suggest that brook charr exhibit microgeographic population structure at the watershed scale, and that this is the scale at which conservation and management of this salmonid might best be implemented.

Notes: . Two factors affecting the centralization of wastewater treatment facilities were investigated; the cost of collection and treatment systems and the performance of treatment plants. Based on computer-generated minimum cost designs, wastewater collection networks were found to be characterized by diseconomies of scale of magnitude similar to the reported economies of scale for wastewater treatment works. The combined costs of collection and treatment are U-shaped functions from which the least cost size of collection and treatment systems were found for particular values of population density. Examination of the day-to-day performance of five metropoitan-area waste-water treatment plants revealed that, for time series shorter than one month, the day-to-day variation in effluent quality was random, although the variation in quantity discharged was distinctly non-random. The performances of all five plants on any given day showed little correlation. This suggests that the decentralization of treatment facilities can produce benefits both through the reduction in quantities of waste discharged at a given point and through in-stream averaging of the varying performances of several treatment plants. Since the cost function of collection and treatment combined is generally flat in the region of the minimum-cost size, little penalty is invoked to gain the potential benefits of treatment plant decentralization.

Notes: A procedure for land-surface zoning, related to the protection of groundwater against both point and diffuse pollution, is described. The procedure is based upon two independent elements:(i) Division of the entire land surface on the basis of the aquifer pollution vulnerability, which relates to protection of groundwater resources; and(ii) A series of special protection areas for individual sources, in which various potentially polluting activities are either prohibited or strictly controlled.The procedure is hydrogeologically based, but not so complex as to be unworkable in practice. For resource protection three classes of formation type are defined, with a further subdivision on the basis of depth to saturated aquifer. In the case of diffuse pollution, it will also be necessary to consider the nature of the soil cover in the area where the polluting activity occurs. For source protection, up to four special protection areas are specified, and the criteria used to define them are discussed.

Notes: There is a widely held belief that, over the last few decades, many rivers and wetlands have been significantly degraded. Clearly, groundwater abstraction has had a detrimental effect. However, other pressures such as channelisation, sedimentation, reduced rainfall, poor site management or land-use change can be contributing factors. Various policy responses are reviewed and some examples are given. It is concluded that, whilst groundwater abstraction does cause river and wetland degradation, the degree of degradation often depends upon the individual perspective; therefore a rigorous approach is required in quantifying such degradation and its actual causes, beginning with the establishment of clear objectives and the collection of appropriate data.

Notes: The influence of the growth photon flux density (PFD) on the size and composition of the carotenoid pool and the size of the reduced ascorbate pool was determined across a light gradient from the forest floor to the canopy and the forest edge of a sub-tropical rainforest in New South Wales, Australia. Nineteen plant species (most collected from multiple sites) representing a broad taxonomic range consistently possessed larger total carotenoid pools when found growing in more exposed sites. There was a significant positive correlation between β-carotene content and growth PFD and a significant negative correlation between α-carotene content and growth PFD. Neoxanthin content exhibited no significant trend while the trend in lutein content varied with mode of expression. The pigments of the xanthophyll cycle (violaxanthin, antheraxanthin and zeaxanthin) exhibited the most pronounced response to growth PFD; they comprised a much greater portion of the total carotenoid pool in high light-acclimated plants. The pool of reduced ascorbate was also several-fold greater in high light-acclimated plants. These acclimatory changes in carotenoid and ascorbate content are consistent with a need for a greater capacity to dissipate excessive absorbed light energy in high light-acclimated plants.

Notes: The carotenoid composition of sun leaves of nine species of annual crop plants (some with several varieties) was compared with sun and shade leaves of several other groups of plants, among those sun and shade leaves of several species of perennial shrubs and vines and deep-shade leaves of seven rainforest species. All sun leaves contained considerably greater amounts of the components of the xanthophyll cycle violaxanthin, antheraxanthin and zeaxanthin as well as of β-carotene than the shade leaves, as had previously been reported for a variety of other species by Thayer & Björkman (Photosynthesis Research, 1990, 23, 331–343). Therefore, high light specifically stimulated β,β-carotenoid synthesis. The sun leaves of these crop species did not contain α-carotene which was, however, present in large amounts in all shade leaves and in smaller amounts in sun leaves of three of the four species of perennial shrubs and vines. There was no difference in neoxanthin content on a chlorophyll basis between sun and shade leaves, and there was no consistent general difference in the lutein content between all sun and all shade leaves. The zeaxanthin (and antheraxanthin) content at peak irradiance and the xanthophyll cycle pool size were compared for sun leaves from the different groups of plants with different life forms and different metabolic activities. When growing in full sunlight the annual crop species and a perennial mesophyte had high rates of photosynthesis whereas the perennial shrubs and vines had relatively low photosynthesis rates. More zeaxanthin (and antheraxanthin) were accumulated at noon in full sunlight in those species with the lower photosynthesis rates. However, it was not such that those species also possessed the larger pools of violaxanthin + antheraxanthin + zeaxanthin. Instead, the xanthophyll cycle pools of sun leaves of the annual crop species and the perennial mesophyte were not smaller, and were even possibly larger, than those of sun leaves of the perennial shrubs and vines with low photosynthesis rates. This was so in spite of the fact that the crop species experienced much lesser degrees of excessive light at full sun than the shrubs and vines. Thus, many of the crop species converted only about 30–50% of their xanthophyll cycle pool to zeaxanthin at noon, whereas the shrubs and vines typically converted more than 80% of their pool into zeaxanthin. The crop species also had larger pools of β-carotene than the shrubs and vines but smaller pools of lutein than the majority of the latter species.