Remote sensing of tidal networks and their relation to vegetation

The study of the morphology of tidal networks and their relation to salt marsh vegetation is currently an active area of research, and a number of theories have been developed which require validation using extensive observations. Conventional methods of measuring networks and associated vegetation can be cumbersome and subjective. Recent advances in remote sensing techniques mean that these can now often reduce measurement effort whilst at the same time increasing measurement scale. The status of remote sensing of tidal networks and their relation to vegetation is reviewed. The measurement of network planforms and their associated variables is possible to sufficient resolution using digital aerial photography and airborne scanning laser altimetry (LiDAR), with LiDAR also being able to measure channel depths. A multi-level knowledge-based technique is described to extract networks from LiDAR in a semi-automated fashion. This allows objective and detailed geomorphological information on networks to be obtained over large areas of the inter-tidal zone. It is illustrated using LIDAR data of the River Ems, Germany, the Venice lagoon, and Carnforth Marsh, Morecambe Bay, UK. Examples of geomorphological variables of networks extracted from LiDAR data are given. Associated marsh vegetation can be classified into its component species using airborne hyperspectral and satellite multispectral data. Other potential applications of remote sensing for network studies include determining spatial relationships between networks and vegetation, measuring marsh platform vegetation roughness, in-channel velocities and sediment processes, studying salt pans, and for marsh restoration schemes

Duality for minmax programs

AbstractA duality theory is derived for minimizing the maximum of a finite set of convex functions subject to a convex constraint set generated by both linear and nonlinear inequalities. The development uses the theory of generalised geometric programming. Further, a particular class of minmax program which has some practical significance is considered and a particularly simple dual program is obtained

Glutathione S-transferases YcYfetus and YcYc - kinetic and inhibitor studies relating to their glutathione peroxidase activities

The kinetic properties of the glutathione (GSH) peroxidase activities of GSH S-transferases YcYfetus and YcYc were compared. The catalytic efficiency of the fetal iso-enzyme with cumene hydroperoxide as substrate was approximately four times higher than the other. The effects of the non-substrate ligand rose-Bengal as well as the substrate ligands sulphobromophthalein and acrolein on the GSH peroxidase activity of these two iso-enzymes were also investigated. Depending on the ligand, the inhibition profiles of these two iso-enzymes when measured with either the peroxidase substrate, cumene hydroperoxide or the standard GSH S-transferase substrate 1:chloro-2,4-dinitrobenzene were found to be either very similar (sulphobromophthalein) or markedly different (rose Bengal and acrolein). Significantly, the GSH peroxidase activity of the fetal iso-enzyme was far less susceptible to inhibition by the teratogen, acrolein, than that of the YcYc isoenzyme. It is therefore attractive to suggest that should a similar situation arise in vivo, this resistance to peroxidase inhibition may play a role in preventing the fetotoxic effects of acrolein

Evaluation of biochemical methods for the non-destructive identification of sex in upstream migrating salmon and sea trout

Female-specific markers of reproductive activity (plasma 17β-estradiol, E2; vitellogenin, VTG; alkali-labile phosphoprotein phosphorous, ALP) were measured over 12 months in a captive population of brown trout. During the early months of the reproductive season (February – May) and using the concentration of plasma E2 or plasma ALP as a marker for females the proportion of fish in which sex was misidentified was high (15% - 50%). The misidentification rate was considerably lower (1 – 8%) using plasma VTG. Preliminary evaluation of a commercial immunochromatographic VTG test system as a screen for the presence or absence of VTG in plasma from brown trout provided results that were consistent with those obtained from direct measurement of plasma VTG levels by ELISA. These preliminary conclusions were verified by sampling upstream-migrating sea trout and salmon trapped over a 6 month period. Plasma E2 levels did not satisfactorily discriminate between male and female sea trout and salmon. However, plasma VTG levels in both species were bimodally distributed and it was assumed that this divergence corresponded to male (plasma VTG levels 800 μg ml-1) fish. Plasma ALP provided a more accurate indication of sex in the wild salmon and sea trout than was suggested by the pilot study on captive brown trout. The commercial immunochromatographic VTG test system provided results that were wholly consistent with the data obtained from the trapped fish by direct measurement of plasma VTG

Dynamic financial planning: Certainty equivalents, stochastic constraints and functional conjugate duality

This paper studies portfolios under risk and stochastic constraints. Certainty equivalents combine risk aversion and exponential utility to form the objective. Budget and stochastic constraints on the account balance are used to ensure a positive net worth over time. These portfolio models are analyzed by functional conjugate duality for general distributions and by conjugate duality for the normal distribution. All the programs are convex. The duals provide insight into this approach and relate it to other stochastic and financial concepts. Copyright © "IIE"

Assessment of the physiological impact of endocrine disrupting chemicals on salmonid fish from selected sites in Scotland and Northern Ireland

1. Recent research in the UK and elsewhere has demonstrated that industrial and domestic effluents may contain compounds of both natural and synthetic origin which are steroid estrogens, or mimic the activity of steroid estrogens. Although present in solution at very low concentrations the sensitivity of the endocrine system of animals to interference is such that these contaminants represent a potentially disruptive threat. 2. A survey of gonadal structure in roach populations in English rivers revealed that a high proportion (25% – 60%) of male fish within the sampled populations displayed evidence of abnormal gonadal development in the form of ovarian tissue within the testes. These effects were most pronounced at sites where discharged effluents represented a high proportion of total flow in the river. The functional significance of these observations has yet to be established. 3. Concerns have been raised regarding the possible susceptibility of valuable salmon and trout populations to endocrine disruptive processes. This report describes the results of a fieldbased investigation of indicators of estrogen exposure in salmonid fish exposed to potentially estrogenic effluent discharges at sites in Scotland and Northern Ireland. 4. This study addressed the possibility that native salmonid populations are being exposed to estrogenic contaminants via both domestic and industrial discharges and that this exposure may result in inappropriate and possibly detrimental physiological effects in exposed fish. 5. This objective was addressed by the sampling of brown trout and Atlantic salmon from sites receiving a STW discharge and from pristine sites. Blood levels of the estrogen-inducible yolk precursor vitellogenin were measured to assess whether there was evidence that the targeted populations were exposed to acute estrogen exposure. In addition, gonadal material sampled from each fish was examined microscopically for evidence of abnormal reproductive development, the presence of which would be indicative of early or possibly chronic exposure to estrogens. 6. A total of 209 fish were examined from four sites in Scotland [R. Teviot, Slitrig Water (tributary of the R. Teviot), Wilson Burn and Ale Water (pristine sites)]. Fish sampled from the R. Teviot were removed downstream of the Hawick STW discharge. In all the fish which were sampled blood vitellogenin levels were low, displaying no evidence of environmental estrogen-induced elevation. The gonadal structure of all the sampled fish was normal, with no evidence of ovarian tissue in male testes and no evidence of unusual ovarian development in female fish. 7. A total of 64 fish were examined from three sites in Northern Ireland (Minnowburn, Collin River and Ravernet River; all tributaries of the R. Lagan). As was the case for the Scottish sites, no evidence of gonadal abnormalities was obtained in fish from any site. 8. In addition to the field sampling, the estrogenicity of the effluents discharged at each site were evaluated by bioassay. In Northern Ireland, rainbow trout were held in cages submerged in the vicinity of the New Holland Sewage Treatment Works (STW) effluent discharge (R. Lagan). An aquarium-based exposure of rainbow trout to Hawick STW (R. Teviot) final effluent, at concentrations up to 100%, was employed. Analysis of blood vitellogenin levels after a period of or 11 – 14 days exposure in aquaria revealed that the Hawick STW effluent was not estrogenic. However, fish exposed to New Holland STW final effluent in situ for 3 weeks displayed elevated blood vitellogenin levels, relative to fish caged at control sites, indicating that the effluent contained estrogenic components. 9. Water samples collected from both study sites were analysed for total alkylphenols and alkylphenol ethoxylates (APEs; ubiquitous environmental contaminants and known estrogen mimics found in high concentrations in English rivers with a high incidence of intersexuality). Samples from the Hawick sites contained very low levels of APEs (< 3 :g l-1). Similar levels were found in samples from the sites in Northern Ireland with the exception of effluent samples taken downstream of the Barbour Campbell Linen Mill which contained 12 :g l-1 total APEs. Steroids were not quantified in these samples. 10. The microscopic examination of gonad structure, and analysis of blood vitellogenin levels, indicated that there was no evidence of exposure to estrogenic contaminants in the salmonid fish populations of the R. Teviot or R. Lagan. 11. A number of factors probably contribute to this result. Salmonid fish exhibit a life-history very different to that of cyprinid fish such as roach in which effluent-related intersexuality has been reported. Trout and salmon normally spawn in clean gravel beds in the upper reaches of a river system and newly-hatched and early juvenile salmonid fish remain in these relatively pristine stretches of river. They are therefore not usually exposed to point-source effluent discharges during critical early developmental stages when the reproductive system is particularly sensitive to external influences. In addition, both salmon and migratory brown trout (sea trout) are anadromous fish, spending a significant proportion of their lives at sea. These factors contrast with the potential for life-long exposure to contaminants displayed by non-migratory cyprinid fish which spawn in the main body of the river. Additionally, salmonid fish are less tolerant of poor water quality than cyprinid fish and even the nonmigratory brown trout are therefore not normally present in rivers subject to high effluent input. Most rivers which support populations of salmonid fish do not pass through heavily populated or industrialised areas. There is therefore less likelihood that these fish populations will encounter high concentrations of endocrine disrupting chemicals (EDCs). 12. Overall, these data do not provide absolute reassurance that salmonid fish are unaffected by estrogens and estrogen mimics present in effluent discharges but they do indicate that if a problem does exist it may be localised and on a smaller scale than has been reported for cyprinid fish. 13. Consideration should be given to a more widespread survey of gonad structure in salmonid fish populations in order to confirm these preliminary conclusions. It should also be considered whether reproductive performance of salmonid fish might be influenced by exposure to EDCs via mechanisms which do not involve alterations in gonadal structure (e.g. alterations in fecundity, gamete quality, behavioural changes). In addition, the possibility that aspects of the salmonid life-history other than reproductive development may be affected by EDCs should be examined. 14. For example, smoltification (pre-migratory sea water adaptation) is a critically important aspect of the salmonid life history. Smoltification is closely regulated by the endocrine system and may be susceptible to interference by chemicals which mimic or interfere with the activity of hormones other than estrogens. 15. It should also be considered whether sources of contamination other than effluent discharges (e.g. agricultural run-off) may expose salmonid fish to endocrine-disrupting chemicals

LiDAR mapping of tidal marshes for ecogeomorphological modelling in the TIDE project

The European research project TIDE (Tidal Inlets Dynamics and Environment) is developing and validating coupled models describing the morphological, biological and ecological evolution of tidal environments. The interactions between the physical and biological processes occurring in these regions requires that the system be studied as a whole rather than as separate parts. Extensive use of remote sensing including LiDAR is being made to provide validation data for the modelling. This paper describes the different uses of LiDAR within the project and their relevance to the TIDE science objectives. LiDAR data have been acquired from three different environments, the Venice Lagoon in Italy, Morecambe Bay in England, and the Eden estuary in Scotland. LiDAR accuracy at each site has been evaluated using ground reference data acquired with differential GPS. A semi-automatic technique has been developed to extract tidal channel networks from LiDAR data either used alone or fused with aerial photography. While the resulting networks may require some correction, the procedure does allow network extraction over large areas using objective criteria and reduces fieldwork requirements. The networks extracted may subsequently be used in geomorphological analyses, for example to describe the drainage patterns induced by networks and to examine the rate of change of networks. Estimation of the heights of the low and sparse vegetation on marshes is being investigated by analysis of the statistical distribution of the measured LiDAR heights. Species having different mean heights may be separated using the first-order moments of the height distribution

Perturbative Prepotential and Monodromies in N=2 Heterotic Superstring

We discuss the prepotential describing the effective field theory of N=2 heterotic superstring models. At the one loop-level the prepotential develops logarithmic singularities due to the appearance of charged massless states at particular surfaces in the moduli space of vector multiplets. These singularities modify the classical duality symmetry group which now becomes a representation of the fundamental group of the moduli space minus the singular surfaces. For the simplest two-moduli case, this fundamental group turns out to be a certain braid group and we determine the resulting full duality transformations of the prepotential, which are exact in perturbation theory.Comment: 39 pages, LaTeX, no figures; section 6 expanded to include explicit construction of the monodromy group in a (4,0) orbifold exampl

Books

Medical audit Audit in Action. Ed. by Richard Smith. Pp. xiv + 245. Illustrated. £10,95. London: British Medical Journal. 1992. Available from Libriger Book Distributors, Bloemfontein.Rheumatology Bailliere's Clinical Rheumatology: Giant Cell Arteritis and Polymyalgia RheuIDatica. Guest eds B. L. Hazleman and B.-A. Bengtsson. Pp. xi + 507. illustrated. £27,50. London: Bailliere Tindall. 1991.AIDS, drugs and sexual risk AIDS, Drugs and Sexual Risk. By N. McKeganey and M. Bamard. Johannesburg: Random Century. 1992.Radiation When is a Dose Not a Dose? By Victor P. Bond. Pp. 39. Illustrated. Bethesda: National Council on Radiation Protection and Measurements. 1992.Autoimmune disease Clinical and Molecular Aspects of Autoimmune Diseases. Vol. 8. Ed. by J. M. Cruse and R. E. Lewis. Pp. x + 258. Illustrated. SFr. 248. Basel: Karger. 1992.Biochemical toxicology Principles of Biochemical Toxicology. 2nd ed. By J. A. Timbrel!. Illustrated. Pp. 415. RI53,73. London: Taylor &amp; Frands. 1991.Advances in pineal research Advances in Pineal Research. Vol. 6. Ed. by Andrew Foldes and R. J. Reiter. pp. viii + 286. illustrated. £32,50. London: John Libbey. 1991.Health care for the future The Future of Health Care. Pp. 83. Illustrated. London: British Medical Journal. 1992.STDs and AIDS School Health Education to Prevent AIDS and Sexually Transmitted Disease. Pp. 79. SFr. 18. Geneva: World Health Organisation. 1992

p21 (WAF1) is component of a positive feedback loop that maintains the p53 transcriptional program

The regulation of p53 activity through the MDM2 negative feedback loop is driven in part by an extrinsic ATM-pulse that maintains p53 oscillations in response to DNA damage. We report here that the p53 pathway has evolved an intrinsic positive feedback loop that is maintained by the p53-inducible gene product p21WAF1. p21-null cancer cells have defects in p53 protein turnover, reductions in MDM2-mediated degradation of p53, and reduced DNA damage-induced ubiquitination of p53. TLR3-IRF1 or ATM-dependent signaling to p53 is defective in p21-null cells and complementation of the p21 gene in p21-null cancer cells restores the p53 transcriptional response. The mechanism of p53 inactivity in p21-null cells is linked to a p53 protein equilibrium shift from chromatin into cytosolic fractions and complementation of the p21 gene into p21-null cells restores the nuclear localization of p53. A loss of p53 transcriptional function in murine B-cells heterozygous or homozygous null for p21 highlights a p21-gene dosage effect that maintains the full p53 transcriptional response. ATM inhibition results in nuclear exclusion of p53 highlighting a positive genetic interaction between ATM and p21. P21 protein oscillates in undamaged proliferating cells, and reductions of p21 protein using siRNA eliminate the DNA damage-induced p53 pulse. The p53 transcription program has evolved a negative feedback loop maintained by MDM2 that is counteracted by a positive feedback loop maintained by ATM-p21 the balance of which controls the specific activity of p53 as a transcription factor