Difference In Tube Length Research Articles

A shift in long-proboscid fly pollinators and floral tube length among populations of Erica junonia (Ericaceae)

Macroevolutionary studies frequently emphasize the importance of pollinator shifts for driving speciation within the angiosperms. Pollinators have been identified as a driver of diversification in the mega-diverse genus Erica in the Cape Floristic Region of South Africa, but basic information on pollinator-driven divergence at the initial stages of speciation in this genus is lacking. We focus on two populations of Erica junonia (var. junonia and var. minor) that occur on adjacent mountain ranges separated by c. 10 km and which differ in floral tube length, and ask whether these differences in tube length are associated with a shift between pollinators with different proboscis lengths. In addition, we assess whether the two forms differ in their ability to reproduce in the absence of pollinators. Our findings show that different Erica junonia varieties are visited by different nemestrinid fly species in the genus Moegistorhynchus, and that their floral tube lengths correspond to the proboscis lengths of these flies. Pollinator exclusion experiments show that the short-tubed var. minor is capable of producing seeds in the absence of pollinators, whereas the long-tubed var. junonia depends fully on pollinators. Our study provides an example of pollinator-driven divergence on a small spatial scale and contributes to an understanding of diversification of the genus Erica.

Comparative In Vitro Flow Study of 3 Different Ex-PRESS Miniature Glaucoma Device Models

To determine the flow characteristics of the 3 different models of the Ex-PRESS miniature glaucoma device in a controlled laboratory study. The 3 different Ex-PRESS models (P-50, R-50, and P-200; Optonol Ltd; now Alcon Lab) were tested using a gravity-driven flow test. Three samples of each of the 3 Ex-PRESS models were subjected to a constant gravitational force of fluid at 5 different pressure levels (5 to 25 mm Hg). Four measurements per sample were taken at each pressure level. The main outcome measure was flow rate (Q) (µL/min). Resistance (R) was calculated by dividing pressure (P) by the measured flow (Q). The flow rate was primarily pressure dependent. The P-200 model (internal diameter 200 µm) showed a statistically significant higher flow rate and lower resistance compared with both the P-50 and R-50 models (internal diameter 50 µm) (P<0.0001). The P-50 and R-50 models demonstrated similar flow rates (P=0.08) despite their difference in tube length (2.64 vs. 2.94 mm). The 3 models of the Ex-PRESS mini shunt behaved in vitro as simple flow resistors by creating a relatively constant resistance to flow. Tube diameter was the only parameter with significant impact on flow and resistance. All models demonstrated flow rates per unit of pressure much higher than the outflow facility of a healthy human eye.

Hyper-specialization for long-billed bird pollination in a guild of South African plants: the Malachite Sunbird pollination syndrome

A large diversity of floral morphological types exists within the bird pollination syndrome in the Cape Floral Region of South Africa. Here we focus on species with tubular flowers and ask: “Do differences in tube length among plant species correspond to differences in bill length among the birds that serve as pollinators?” To answer this question, we observed 1669 bird–plant interactions at thirteen bird-pollinated plant species across a spectrum of tube lengths. Only three nectar feeding bird species pollinated the focal plant species. The relatively short-billed species were the Southern Double-collared Sunbird ( Cinnyris chalybea) and Orange-breasted Sunbird ( Anthobaphes violacea); the only long-billed species was the Malachite Sunbird ( Nectarinia famosa). We found that the groups of plant species pollinated by the long- and short-billed birds differed significantly in floral tube length. Short-billed sunbirds nevertheless often robbed long-tubed flowers by piercing the corolla, and there was a significant difference in floral tube length among those species that were robbed, and those that were pollinated by short-billed sunbirds. The presence of territorial Malachite Sunbirds depressed robbing rates by short-billed sunbirds at long-tubed flowers. In turn, the absence of Malachite Sunbirds from short-tubed plant species might be explained by the observed positive correlation between tube length and nectar volume. Together, these data suggest that there is a subset of the bird-pollinated plants at the Cape that are pollinated solely by the long-billed Malachite Sunbird, a pollination service irreplaceable by the more abundant, short-billed sunbird species. To extrapolate this finding to a greater subset of species in the Cape Floral Region, we measured flowers on herbarium specimens of all tubular putatively bird-pollinated plants. We find that floral tube length has a bimodal distribution with 37 Cape species potentially dependent on pollination by Malachite Sunbirds.

Anodic oxide nanotube layers on Ti–Ta alloys: Substrate composition, microstructure and self-organization on two-size scales

The present work reports the self-ordered formation of nanotubular oxide layers on Ti–Ta alloys of different compositions (Ti–13Ta, Ti–25Ta, Ti–50Ta, and Ti–80Ta) by anodization in 1 M H 2SO 4 + 0.15 wt.% HF. Depending on the alloy composition, nanoporous or highly ordered nanotube structures can be formed. The homogeneity of the nanotubular surface layers is strongly affected by the microstructure of the alloys. Over a wide composition range the alloys exhibit a two-phase structure, and this results in two distinct tube morphologies formed on the different phases. In particular, on the chemically less stable phase, the top of nanotube layers is etched, which results in a disordered top morphology of the tubes on Ti–13Ta and Ti–25Ta, whereas this effect yields a difference in tube length on the two phases on Ti–50Ta. For the Ti–50Ta alloy, a bimodal self-organization can be observed, i.e. ordered patterns of oxide tubes with two distinct diameters are formed where larger tubes are surrounded by smaller tubes with a regularity that depends on the chemical composition of the two phases.

Danish experience with fireside corrosion

AbstractFireside corrosion has not been a severe problem in Danish power plants.Furnace wall corrosion has only been seen in one unit caused by insufficient control of the burners.High temperature corrosion has only been seen in units, where the final stage of superheater/reheater was placed in gas temperatures above 1300°C or where the difference in tube length was too big. Since 1970 the final stages of superheater and reheater are made of X20 CrMo V 12.1, which has showed excellent behavior.For estimation of the remaining service life of superheater/reheater, they are examined after 100,000 h in service.