Comparative growth rates and internal banding periodicity of maerl species (Corallinales, Rhodophyta) from northern Europe

Maerl is a type of rhodolith, found in ecologically important beds of high conservation value; a major conservation objective is to establish growth rates. Maerl shows internal banding of controversial periodicity that may contain a high-resolution record of palaeoceanographic-palaeoclimatic data. To investigate growth rates and banding periodicity, we used the vital stain Alizarin Red in combination with scanning electron microscopy (SEM). Three maerl species, Phymatolithon calcareum, Lithothamnion corallioides and L. glaciale, were collected from maerl beds in Ireland. Following staining, maerl was grown in three controlled temperature treatments and at two depths in the field (P. calcareum only), with Corallina officinalis as a control for the stain. Alizarin Red was shown to be a suitable marker for growth in European maerl species and for C. officinalis. The average tip growth rate of P. calcareum from Northern Ireland at 10 m depth and under constant laboratory conditions was c. 0.9 mm yr(-1), double the rates observed at 5 m depth and in L. corallioides. Our measurements and re-examination of reported data allow us to conclude that the three most abundant maerl species in Europe grow about 1 (0.5-1.5) mm per tip per year under a wide range of field and artificial conditions. Internal banding in temperate European maerl revealed by SEM is a result of regular changes in wall thickness; the approximately monthly periodicity of bands in field-grown specimens is consistent with previous suggestions that they may be lunar. The potential for maerl banding to be a high-resolution record of palaeoclimatic and palaeoenvironmental change could be realized with this vital stain in conjunction with isotopic or microgeochemical analyses.

Internal model control for shape memory alloy actuators using fuzzy based Preisach model

This paper investigates a possible application of Preisach model to control shape memory alloy (SMA) actuators using an internal model control strategy. The developed strategy consists in including the Preisach hysteresis model of SMA actuator and the inverse Preisach model within the control structure. In this work, an extrema input hystory and a fuzzy inference is utilized to replace the classical Preisach model. This allows to reduce a large amount of experimental parameters and computation time of the classical Preisach model. To demonstrate the effectiveness of the proposed controller in improving control performance and hysteresis compensation of SMA actuators, experimental results from real time control are presented.

Flanking and internal regions of chromosomal genes mediating aerobactin iron uptake systems in enteroinvasive Escherichia coli and Shigella flexneri

We have investigated the presence of the aerobactin system and the location of the aerobactin genes in enteroinvasive strains of Escherichia coli. Also, we cloned the aerobactin region and its flanking sequences from the chromosome of a strain of Shigella flexneri and compared the molecular organization of the aerobactin genes in the two genera. Of the 11 enteroinvasive E. coli strains studied, 5 possessed the aerobactin genes, which were located on the chromosome in each case. These strains produced and utilized aerobactin and also were susceptible to the bacteriocin cloacin-DF13. Restriction endonuclease mapping and hybridization experiments showed that the regions corresponding to the aerobactin-specific sequences were very similar in both enteroinvasive E. coli and S. flexneri. However, differences were found in the region corresponding to the aerobactin receptor gene. The regions flanking the aerobactin system in enteroinvasive E. coli and S. flexneri exhibited some similarities but were different from those in pColV-K30. Under iron-limiting conditions, aerobactin-producing enteroinvasive E. coli and S. flexneri synthesized outer-membrane proteins of 76 and 77 kDa, respectively, which cross-reacted immunologically with rabbit antiserum raised against the 74 kDa pColV-K30-encoded ferric aerobactin receptor.

Response of red blood cell folate to intervention: implications for folate recommendations for the prevention of neural tube defects

Committees worldwide have set almost identical folate recommendations for the prevention of the first occurrence of neural tube defects (NTDs). We evaluate these recommendations by reviewing the results of intervention studies that examined the response of red blood cell folate to altered folate intake. Three options are suggested to achieve the extra 400 mu g folic acid/d being recommended by the official committees: increased intake of folate-rich foods, dietary folic acid supplementation, and folic acid fortification of food. A significant increase in foods naturally rich in folates was shown to be a relatively ineffective means of increasing red blood cell folate status in women compared with equivalent intakes of folic acid-fortified food, presumably because the synthetic form of the vitamin is more stable and more bioavailable. Although folic acid supplements are highly effective in optimizing folate status, supplementation is not an effective strategy for the primary prevention of NTDs because of poor compliance. Thus, food fortification is seen by many as the only option likely to succeed. Mandatory folic acid fortification of grain products was introduced recently in the United States at a level projected to provide an additional mean intake of 100 mu g folic acid/d, but some feel that this policy does not go far enough. A recent clinical trial predicted that the additional intake of folic acid in the United States will reduce NTDs by >20%, whereas 200 mu g/d would be highly protective and is the dose also shown to be optimal in lowering plasma homocysteine, with possible benefits in preventing cardiovascular disease. Thus, an amount lower than the current target of an extra 400 mu g/d may be sufficient to increase red blood cell folate to concentrations associated with the lowest risk of NTDs, but further investigation is warranted to establish the optimal amount.