Aspects of the biology of climbers in southern Africa

This study examines factors that may limit the abundance and distribution of climbers and the influence that climbers may have on the regeneration of forests. The abundance of climbing plants (climbers) was established over a soil nutrient gradient, under standardised light conditions. Abundance was found to be positively correlated with the potassium concentration and the soil S-value, but not with other nutrients. Thus, the association between climbers and soil nutrient levels is challenged. Instead the abundance of climbers was found to be positively correlated with tree canopy architecture and trellis availability. More climbers entered host trees with low canopies (< 15 m) than those with high canopies. Trees with low canopies had more climbers entering vertically into the canopy while trees with high canopies had more climbers entering the canopy horizontally. Evidence was found to suggest that climbers facilitate the entry of each other into tree canopies. Tree and climber saplings were grown under three nutrient and two light treatments to compare the relative growth rates of their terminal shoots under the different conditions. While climbers were found to have greater shoot extension rates than trees, they did not grow relatively faster than trees under any of the combination of treatments. Thus light levels and soil nutrient availability may not influence the competitive ability of climbers compared to trees. Three aspects of the carbon gain capacity (maximum photosynthetic rate, leaf nitrogen concentration and leaf water use efficiency) were compared between climbers and trees. While the climbers had a significantly higher leaf nitrogen concentration than trees, as well as higher leaf water use efficiency; the maximum carbon assimilation rates of climbers and trees did not differ. These differences between trees and climbers are slight and suggest that differences in growth rates between the two growth forms are largely due to differences in carbon allocation in trees (to support structures) and in climbers (shoot elongation), rather than carbon gain mechanisms. Patterns of canopy tree regeneration in gaps and sub-canopy plots were determined for lowland and highland forests to determine whether climbers influenced the regeneration of canopy trees. More canopy trees regenerate in the sub-canopy of highland forests, while in lowland forests treefall gaps are the major sites of canopy tree regeneration. These patterns of regeneration were found not to be related to the density of the ground layer, the extent of the lateral infill of the gap-forming trees or the abundance of woody climbers. Instead, a negative correlation was found between the percentage of regenerating canopy species and the density of the herbaceous and shrubby understory layer in both lowland and highland forests. Thus in both forests the understory layer has an important influence on the regeneration of canopy trees. The role of vertebrate herbivores may be important in providing the necessary release from suppressive effect of the dense understory layer and to enable the regeneration of canopy tree species in the lowland forests

Toxicity of the dye stuffs, with special reference to their effects upon the public health, and to river pollution

On the whole it is probable that most of the dye stuffs are passed into streams in such a diluted condition, and there become so much more diluted, that they do not kill the fish. This is borne out by what is found in the river Leven, in Dumbartonshire, which is polluted by effluents from Turkey Red works.. It is said that,in this case, the dye stuffs have no effect on the fish which are injured by caustic and other substances employed in the process. Quite apart from any fatal result however the fish may suffer in health from fungus growth, while deposits are likely to occur, and as it would seem that simple methods can obviate these undesirable effects, their use should be enforced.As is shewn in the experiments with mill effluents and stream waters filtration or simple precipitation apparently renders the effluents innocuous. In the case of the Tweed, trout are frequently caught at a point just below where the mill discharges take place, and no objection can be taken to the condition of the river water, although as will be seen by reference to the tables, the dyes and substances mixed with than are very fatal.Indigo effluents, even when foul smelling, did not kill fish and must be regarded as non toxic; but most of the Yorkshire rivers in the factory districts are in a disgraceful state. Dr Maclean Wilson, Medical Inspector to the West Riding Rivers Board, to whom I am indebted for the samples he sent me, has however devoted attention to the existing state of affairs, and improvement may be looked for. I must also express my thanks to Oscar Schofield Esq. of Littleboro' Lancashire, who sent me samples containing vegetable dyes and mordants. Such a sample was rapidly fatal, but after filtration its toxic properties entirely disappeared. He employe Kremmolite, a form of iron ore for the purpose and from my results it would seem to act admirably.It is.probable therefore that careful filtra¬ tion or precipitation is all that is required, with a sufficient staff of inspectors to see that, what¬ ever process is adopted, it is efficiently carried out. Till this is done, not only in connection with, dye's and mordants, but also with other forms of stream pollution, the great dream of Frank Buckland's life is not likely to be realised

Efficient deformable motion correction for 3-D abdominal MRI using manifold regression

We present a novel framework for efficient retrospective respiratory motion correction of 3-D abdominal MRI using manifold regression. K-space data are continuously acquired under free breathing using the stack-of-stars radial gold-en-angle trajectory. The stack-of-profiles (SoP) from all temporal positions are embedded into a common manifold, in which SoPs that were acquired at similar respiratory states are close together. Next, the SoPs in the manifold are clustered into groups using the k-means algorithm. One 3-D volume is reconstructed at the central SoP position of each cluster (a.k.a. key-volumes). Motion fields are estimated using deformable image registration between each of these key-volumes and a reference end-exhale volume. Subsequently, the motion field at any other SoP position in the manifold is derived using manifold regression. The regressed motion fields for each of the SoPs are used to deter-mine a final motion-corrected MRI volume. The method was evaluated on realistic synthetic datasets which were generated from real MRI data and also tested on an in vivo dataset. The framework enables more accurate motion correction compared to the conventional binning-based approach, with high computational efficiency

High-resolution self-gated dynamic abdominal MRI using manifold alignment

We present a novel retrospective self-gating method based on manifold alignment (MA), which enables reconstruction of free-breathing, high spatial and temporal resolution abdominal MRI sequences. Based on a radial golden-angle (RGA) acquisition trajectory, our method enables a multi-dimensional self-gating signal to be extracted from the k-space data for more accurate motion representation. The k-space radial profiles are evenly divided into a number of overlapping groups based on their radial angles. MA is then used to simultaneously learn and align the low dimensional manifolds of all groups, and embed them into a common manifold. In the manifold, k-space profiles that represent similar respiratory positions are close to each other. Image reconstruction is performed by combining radial profiles with evenly distributed angles that are close in the manifold. Our method was evaluated on both 2D and 3D synthetic and in vivo datasets. On the synthetic datasets, our method achieved high correlation with the ground truth in terms of image intensity and virtual navigator values. Using the in vivo data, compared to a state-of-the-art approach based on centre of k-space gating, our method was able to make use of much richer profile data for self-gating, resulting in statistically significantly better quantitative measurements in terms of organ sharpness and image gradient entropy

Haemophilus influenzae type b reemergence after combination immunization

An increase in Haemophilus influenzae type b (Hib) in British children has been linked to the widespread use of a diphtheria/tetanus/acellular pertussis combination vaccine (DTaP-Hib). We measured anti-polyribosyl-ribitol phos- phate antibody concentration and avidity before and after a Hib booster in 176 children 2–4 years of age who had received 3 doses of DTP-Hib (either DT whole cell pertus- sis-Hib or DTaP-Hib) combination vaccine in infancy. We also measured pharyngeal carriage of Hib. Antibody con- centrations before and avidity indices after vaccination were low (geometric mean concentration 0.46μg/mL, 95% confidence interval [CI] 0.36–0.58; geometric mean avidity index 0.16, 95% CI 0.14–0.18) and inversely related to the number of previous doses of DTaP-Hib (p = 0.02 and p<0.001, respectively). Hib was found in 2.1% (95% CI 0.7%–6.0%) of study participants. Our data support an association between DTaP-Hib vaccine combinations and clinical Hib disease through an effect on antibody concen- tration and avidit

Incorporation by coordination and release of the iron chelator drug deferiprone from zinc-based metal–organic frameworks

A series of new zinc-based metal–organic framework materials has been prepared in which deferiprone is incorporated as a chelating ligand on infinite or tri-zinc secondary building units following deprotonation. Deferiprone is immediately released from the MOFs on treatments with 1 N hydrochloric acid or buffer, but slow release is observed in ethanoic acid