Tile Substrates Research Articles

Does a warmer lake mean smaller benthic algae? Evidence against the importance of temperature-size relationships in natural systems

Ectotherms decrease in size with increasing ambient temperature. Temperature–size relationships (TSR) have been observed experimentally in a wide range of animals, algae, protozoans and bacteria. However, it is still unclear whether temperature is an important factor controlling the size of organisms in natural populations. In this study, we used natural variability in water temperature in the nearshore areas of a single lake to test TSR in populations of benthic diatoms. We deployed standard tile substrates at 5 m depth (similar light availability) at cold and warm sites that were exposed to different hydrodynamic forces. We compared cell sizes of three species of diatoms (Achnanthidium minutissimum, Gomphonema acuminatum and Gyrosigma acuminatum) at these sites. Counter to the TSR, diatom cells at warm sites were either larger (Achnanthidium, Gomphonema) or similar in size (Gyrosigma) compared to those at colder sites. Diatom size was also related to site exposure (hydrodynamic forces), but differently for species with different architectures. TSR were not detectable in the field for these three species of benthic diatom, even when tested within a single ecosystem at a given time of the year. The size of benthic diatoms, however, varied in a predictable way between sites, and such differences could affect the functioning of these primary producers in different parts of the littoral zone.

Photocatalytic activities of Ion doped TiO 2 thin films when prepared on different substrates

Pure and ion doped TiO 2 thin films were prepared by sol–gel dip coating process on metallic and non-metallic substrates. Test metal ion concentration ranged from 0.000002 to 0.4 at.%. The resulting films were annealed in air and characterized by optical spectroscopy and X-ray diffraction. The photodegradation of methyl orange under UV irradiation by pristine and ion-doped TiO 2 films was quantified in a photocatalytic reactor developed in this study. In general, both doped and undoped TiO 2 crystals appeared in anatase phase and the photocatalytic activities of the TiO 2 thin films varied with substrates, calcination temperature, doping ions and their concentrations. The best calcination temperature for different substrates ranged from 450 to 580 °C. Films prepared on the metallic substrates resulted in higher photocatalytic activities, while ion doping lowered their efficiencies. On the contrary, for non-metallic substrates except ceramic the photocatalytic efficiencies of undoped films were much lower (< 30%), while ion doping was shown to increase the photocatalytic efficiencies remarkably in some cases, e.g., Cr 3+ with the tile substrate. Overall, ion doping affected the photocatalytic efficiency of TiO 2 films, and an optimal doping concentration of between 0.0002 and 0.002 at.%, close to an estimate by the Debye length equation, resulted in the highest efficiency for most substrates.

Determination of the photocatalytic activity of TiO2 coatings on clay roofing tile substrates methylene blue as model pollutant

The photocatalytically active mesoporous coatings, based on titanium dioxide sols (Degussa), of the fired clay roofing tiles substrate were prepared by using poly(ethylene glycol) (PEG) M-600 and M-4000, as the structure directing agents. The coatings were deposited using spray technique followed by thermal treatment. Photocatalytic activity of the TiO2 coatings was evaluated by aqueous solution of methylene blue as model dye, deposited on the top of the coatings, after irradiation with UV light. The results were compared with the photocatalytic efficiency of some commercial self-cleaning products (clay roofing tiles, glass). The newly design coatings showed an interesting decolourisation performance (over 30 % after 24 h). It appeared that the procedure of photocatalytic activity determination, in the case of porous substrates, should be renewed by a preadsorption process.

The Potential to Determine a Postmortem Submersion Interval Based on Algal/Diatom Diversity on Decomposing Mammalian Carcasses in Brackish Ponds in Delaware*

Recently botanical evidence has been studied to determine if it is useful in forensic investigations. This study was performed to examine stillborn piglet decomposition in a brackish water environment and to semi-quantitatively document stages of decomposition, degree day accumulation per stage as well as the algal/diatom diversity useful in determining a postmortem submersion interval (PMSI). Piglets and ceramic tiles were submerged in brackish ponds and sampled on a regular basis to document algal diversity and succession between substrates and stages of decomposition. Significantly greater weight was lost from piglet carcasses during the early floating and advanced floating decay stages. Seasonal effects were observed in degree-day accumulations. Diatom diversity was significantly greater on piglet carcasses compared to tile substrates. Algal diversity decreased over time on the piglet carcasses as well as the stage of decomposition. A significant relationship and strong correlation between algal diversity found on the piglet substrate with time was observed. Our results indicate that more research is needed to examine the potential to use diatoms in not only determining manner of death but also the duration of time (PMSI) a victim may have been immersed in an aquatic environment.

Laser printing of enamels on tiles

A Nd:YAG laser beam is used as a tool to print patterns of coloured enamels on tile substrates. For this, the laser beam is scanned over a layer of raw enamel previously sprayed on the tile surface. The possibility to focus the laser energy to heat a small zone without affecting the rest of the piece presents some advantages in front of traditional furnace techniques in which the whole piece has to be heated; among them, energy saving and the possibility to apply enamels with higher melting temperatures than those of the substrate. In this work, we study the effects of laser irradiation of a green enamel, based in chromium oxide pigment and lead frit, deposited on a white tile substrate. Lines obtained with different combinations of laser beam power and scan speeds were investigated with the aim to optimize the process from the point of view of the quality of the patterns. For this purpose, the morphology of the lines and their cross-sections is studied. The results show that lines with good visual properties can be printed with the laser. The characteristics of the marked lines were found to be directly related with the accumulated energy density delivered. Moreover, there is a linear relationship between the accumulated energy density and the volume of melted material. A minimum accumulated energy density is required to melt a shallow zone of the glazed substrate to allow the adhesion of the enamelled lines.

Finite-element modelling of thermo-mechanical stress distribution in laser beam ceramic tile grout sealing process

Laser tile grout sealing is a special process in which voids between the adjoining ceramic tiles are sealed by a laser beam. This process has been developed by Lawrence and Li using a customized grout material and a high power diode laser (HPDL). The process has been optimally carried out at laser powers of 60–120 W and at scanning speeds of 3–15 mm/s. Modelling of the laser tile grout sealing process is a complex task as it involves a moving laser beam and five different materials: glazed enamel, grout material, ceramic tile, epoxy bedding, and ordinary Portland cement substrate. This article presents the finite element model (FEM) of the laser tile grout sealing process. The main aim of this model is to accurately predict the thermo-mechanical stress distribution induced by the HPDL beam in the process. For an accurate representation of the process, the laser was modelled as a moving heat source. A three-dimensional transient thermal analysis was carried out to determine the temperature distribution. Temperature-dependent material properties and latent heat effects, due to melting and solidification of the glazed enamel, were taken into account in the FEM, thereby allowing a more realistic and accurate thermal analysis. The results of the thermal analysis were used as an input for the stress analysis with temperature-dependent mechanical properties. The results obtained from the FEM are compared with the published experimental results.

Effects of warming on benthic communities in a boreal lake: Implications of climate change

We experimentally warmed a series of shallow enclosures by 4.58C and measured responses of the epilithon (biofilm on rocky surfaces) and invertebrates. Maximum rates of net photosynthesis increased by 28‐115% and rates of dark respiration increased by 29‐103% as a result of warming. Long-term analyses using data from unmanipulated Lake 239 corroborated these findings, showing that rates of light-saturated photosynthesis and dark respiration were positively correlated with water temperature. Warming effects differed between communities (on natural and tile substrates, as well as well-developed and early successional communities). Warming consistently led to increased bacterial cell densities, but increases in total algal biovolume and diatom biovolume were seen only in an early successional tile community. Effects on the composition of the invertebrate community (studied only on well-developed tile biofilms) were small. We observed warming-related increases in carbon accrual within one community, and late in the experiment observed a change in carbon : phosphorus ratios of another community, possibly indicative of a degradation of food quality. Our study suggests that climate warming effects on epilithic community composition are likely to be heterogeneous and difficult to predict; however, the agreement between long-term and experimental results suggests that increased temperatures will increase metabolic rates of the epilithon.

Pig Decomposition in Lotic Aquatic Systems: The Potential Use of Algal Growth in Establishing a Postmortem Submersion Interval (PMSI)

While algal community composition has been examined as a qualitative indicator of postmortem submersion interval (PMSI), there have been no quantitative studies on using algal growth rates as PMSI estimators. The present study was undertaken to examine pig decomposition in streams and to develop a more quantitative approach to estimate a PMSI. Pigs and ceramic tiles were completely submerged and regularly sampled for periphyton growth. Five stages of decomposition were identified for the submerged pig carcasses according to physical characteristics. Algal growth rates, measured quantitatively as a function of chlorophyll-a concentration, were greater on pigs compared with tiles; however, microhabitat (pools versus riffles) did not significantly influence algal growth. Additionally, there was a strong correlation between algal growth rate and time on pigs and tile substrates. This strong correlation was observed after significant rain events. Our study documents for the first time a quantitative technique to determine the length of time a corpse has been submerged in water. We suggest that algal growth rates may be a useful quantitative indicator in criminal investigations involving corpses that are completely submerged in stream or riverine habitats.

Current velocity and invertebrate grazing regulate stream algae: results of an in situ electrical exclusion

Current velocity is a pervasive feature of lotic systems, yet this defining environmental variable is rarely examined as a factor for regulating stream herbivory. To investigate how current modifies herbivory in the upper Colorado River, U.S.A., loops of electrified fencing wire were used to reduce in situ grazer densities on 30 × 30 cm tile substrates. After 45 d, electrified tiles had significantly fewer grazers (P = 0.03) and >2X more algal biomass than controls (P = 0.0002). Reduced grazing on electrified tiles yielded periphytic assemblages having more diatoms and chlorophytes, as well as greater algal species richness. Current velocity effects alone did not significantly regulate algal abundance; however, the interaction between current velocity and grazer exclusion resulted in more algae in slow vs. fast current (P = 0.02). Grazer abundances were similar between fast and slow current velocities, suggesting that grazers in the Colorado River differ in their ability to regulate algae across the current velocity gradient. Our results indicate that stream current-mediated herbivory in streams may be more important than is generally recognized.

Direct observations of the activity responses of mayfly nymphs to relative light change and light intensity

Studies were conducted in a laboratory stream to examine changes in locomotor activity and vertical movement on tile substrates of Stenonema modestum nymphs (Ephemeroptera: Heptagenidae) in response to relative light decrease and acclimation (adaptation) light intensity. Evening twilight, a period during which activity and location changes of mayfly nymphs including S. modestum occur in nature, was simulated by reducing light at constant rates of relative light decrease using a computer-controlled lighting system. Nymphs were kept at one of two light levels prior to the light reduction to test for changes in their response to light caused by visual adaptation to ambient light intensity. The timing of both increased locomotor activity and changes in vertical location on the substrate of S. modestum was strongly correlated with the strength of the relative decrease in light intensity (light stimulus). Timing of both activities took place earlier for nymphs adapted for 60 min at a constant, but reduced light intensity at the water's surface of 8 μW/cm 2 than for those adapted for 60 min at a constant noon-time light intensity of 800μW/cm 2 . Individual nymph responses to light change were contingent upon their initial activity during the light-adaptation periods. Relative light change was the controlling factor initiating both the photokinetic (the non-directional locomotor activity on the lower substrate surfaces) and phototactic (light-directed vertical movements between the lower and upper substrate surfaces) activity changes in these stream invertebrates.

改良高炉スラグ細骨材を用いたプレミックスドライモルタルについて

The premix dry mortar was used as tile substrate mortar, tiling mortar, joint mortar for tiles and so forth. The granulated blastfurnace slag or the annealed blastfurnace slag could not use as fine aggregate for the premix dry mortar, because of the poor workability.In order to improve of the workability of mortar using the granulated blastfurnace slag as fine aggregate, a disintegration process was applied. The mortar tests using processed blastfurnace slag, non processed one and natural sand as fine aggregate were investigated. The workability of mortar using processed one was better than non processed one, and was similar to natural sand. Bending strength and compressive strength of mortar specimen were higher than non processed one and natural sand one. From these experiments, it was confirm that these processed blastfurnace slag could use as fine aggregate for the premix dry mortar.

A laboratory system for examining the influence of light on diel activity of stream macro-invertebrates

I describe a laboratory system for investigating the role of light as a proximate cue for diel changes in locomotor activity and vertical location on the substrate of stream macro-invertebrates. The system consisted of computercontrolled halogen lamps positioned over a laboratory stream in which video-recordings were made of Stenonema modestum mayfly nymphs located on the undersides of unglazed tile substrates. Locomotor activity of study organisms in response to light changes were quantified during computer-programmed and reproducible light/dark (LD) cycles. The system provided the flexibility to simulate a variety of light environments so that the separate influences of light intensity and light change on diel activities of individuals and populations could be examined, which is difficult under natural light conditions. As a group, nymphs responded similarly to simulated twilight (light decrease from 7.9 × 10 2 to 6.9 × 10 −2 µ Wc m −2 at a constant –1.9 × 10 −3 s −1 rate of relative light change) and to natural twilight, suggesting that proposed mechanisms of light control of diel activities in nature can be adequately tested in the simulated environment. However, locomotor activity and vertical movements among individual mayflies were highly variable under controlled conditions, suggesting that physiological differences influence their responses to environmental conditions.

RAIN FOREST CANOPY COVER, RESOURCE AVAILABILITY, AND LIFE HISTORY EVOLUTION IN GUPPIES

Life history traits in guppies (Poecilia reticulata) vary geographically along a predator assemblage gradient, and field experiments have indicated that the association may be causal; guppies introduced from high predation sites to low predation sites have evolved the phenotype associated with low predation in as few as seven generations. It has long been recognized, however, that low predation sites tend to have greater forest canopy cover than high predation sites. Stream differences in canopy cover could translate into stream differences in resource availability, another theoretically potent agent of selection on life history traits. Moreover, new computer simulations indicate that the high predation phenotype would outcompete the low predation phenotype under both mortality regimes. Thus, predation alone may not be sufficient to explain the observed life history patterns. Here we show that food availability for guppies decreases as forest canopy cover increases, among six low predation streams in the Northern Range of Trinidad. Streams with less canopy cover received more photosynthetically active light and contained a larger standing crop of algae (the primary food of guppies), as measured by algal pigments (chlorophylls and carotenoids) on both natural cobble and artificial tile substrates, but did not contain a greater biomass of guppies (per square meter of streambed). Consequently, algae availability for guppies (in micrograms of algal pigments per milligram of guppy) increased with decreasing canopy cover. The biomass of guppies and algae both decreased after a series of floods, with no net effect on algae availability. Field mark–recapture studies revealed that female and juvenile guppies grew faster, and that the asymptotic size of mature males was larger, in streams with less canopy cover. Canopy cover explained 84% of the variation among streams in algae availability which, in turn, explained 93% of the variation in guppy growth rates. Laboratory “common garden” experiments indicated that the stream differences in growth and adult male size in the field were largely environmental (nongenetic). These results strongly suggest that stream differences in canopy cover result in consistent stream differences in food availability, independent of predation. Our preliminary data indicate that some life history traits (offspring size and litter size) vary genetically along the canopy cover gradient, among low predation streams, in the same direction as along the predation gradient. Another recent study shows that food availability is higher at high predation sites than at low predation sites, partly as an indirect effect of predators reducing guppy densities. Further research is required to disentangle the direct effects of predation from those of resource availability in the evolution of life histories.

O 2 erosion of graphite tile substrates

The removal of codeposited tritiated carbon films from the next generation of fusion reactors may rely on the use of baking in an O 2 environment to remove the films. In the present study, we have investigated the effect of baking in O 2 on graphite tile substrate materials. After baking five types of graphite in 2.1 kPa O 2 for 100 h at 623 K, no change in mass was observed. An upper limit on the erosion rate was calculated to be ∼ 4×10 −10 C/ O 2 , whereas the codeposited films obtained from tokamaks have erosion rates as high as 10 −5 C/ O 2 .

Effects of fish predation in erosional and depositional habitats in a temperate stream

Combined effects of predation by benthic and drift-foraging fish (prickly sculpin (Cottus asper) and coho salmon (Onchorhynchus kisutch) parr) on benthic invertebrate community and trophic structure were evaluated in Mayfly Creek, a previously fishless stream in the Coast Range Mountains of British Columbia. The role of microhabitat (substrate) in mediating predation effects was assessed by comparing invertebrate community structure on unglazed ceramic tiles and gravel baskets nested within enclosures. The role of macrohabitat was evaluated by placing enclosures in pool and riffle habitats. Effects of fish predation were most pronounced on tile substrate and in riffle habitat and least pronounced on gravel substrate in pool habitat. The presence of fish caused a decrease in abundance of larger-bodied herbivores (primarily the mayflies Ameletus and Baetis) and had positive indirect effects on algae and smaller invertebrates (primarily Orthocladiinae chironomids and nemourid stoneflies), probably through competitive release. In contrast with herbivores, detritivorous invertebrates were less influenced by fish predation and more highly correlated with the abundance of organic detritus. The distribution and abundance of detritivores in Mayfly Creek appear to be primarily influenced by bottom-up forces (implying resource limitation), while grazers in algal-based food chains are more strongly influenced by top-down effects (fish predation).

Changes in Solar Input, Water Temperature, Periphyton Accumulation, and Allochthonous Input and Storage after Canopy Removal along Two Small Salmon Streams in Southeast Alaska

Changes in solar radiation, water temperature, periphyton accumulation, and allochthonous inputs and storage were measured after we removed patches of deciduous, second-growth riparian vegetation bordering two small streams in southeast Alaska that produce coho salmon Oncorhynchus kisutch. Solar radiation and leaf litter input were measured at the water surface at random locations dispersed through six alternating closed- and open-canopy stream sections. Water temperature, periphyton, and stored organic samples were collected near the downstream end of each section. Solar radiation intensity was measured with digital daylight integrators and pyronometers, periphyton biomass and chlorophyll a were measured on red clay tile substrates, allochthonous input was measured with leaf litter baskets, and benthic organic matter was measured with a Hess sampler. Average intensity of solar radiation that reached the water surface of open-canopy sections was significantly higher than in closed-canopy sections of two streams measured during daylight hours in summer 1988 and of one stream measured day and night in summer 1989. Average daily water temperature was similar in the two canopy types in summer 1988, but was higher in open- than in closed-canopy sections in 1989. Accumulation of periphyton biomass was significantly higher in open- than in closed-canopy sections of the two streams studied in the summer of 1988 and of the one stream sampled in 1989. Accrual of periphyton biomass on tiles placed in the stream for 30-d colonization periods during the summer months of 1989 was also significantly higher in the open than closed sections. Accumulation of chlorophyll a was significantly higher in the open- than in closed-canopy sections of the two streams in 1988 but did not differ significantly between canopy types in 1989. Thirty-day accrual of chlorophyll a was greater in open- than in closed-canopy sections of the one stream studied in 1989. Allochthonous input to the streams decreased after canopy removal, but the amount of organic material stored in the substrate did not differ significantly between open- and closed-canopy sections. Weather was predominantly overcast and rainy in summer 1988 and mostly sunny with infrequent rain in 1989. We speculate that advective heat transfer and high stream discharge from frequent rains moderated the effect of canopy removal and increased solar radiation on water temperatures in open-canopy stream sections in 1988. In 1989, solar radiation was a significant factor in regulating water temperature, especially when streamflows were low. Using a model, we predicted that water temperatures would change little in a 160-m open-canopy reach of Eleven Creek during any weather condition when flows were high. With low flows, however, stream temperatures in open sections of Eleven Creek were predicted to exceed the optimum for growth of juvenile coho salmon in about 20 m during clear sunny weather and in about 50 m when cloudy and overcast.

Predator-prey interactions in a benthic stream community: a field test of flow-mediated refuges.

Ecological theory suggests that the impact of predation can be strongly modified by the existence of regions of the environment in which prey are less accessible to predators, which underscores the need for empirical studies examining the factors influencing the availability and importance of such prey refuges. Our study tested whether benthic microhabitats with high flows provide suspension-feeding larval black flies (Simulium␣vittatum) with a spatial refuge in which the negative impact of predatory flatworms (Dugesia dorotocephala) is reduced. We conducted a short-term field experiment in Chester Creek (southeastern Pennsylvania, United States) to examine how the number of black fly larvae inhabiting tile substrates responded to manipulated variations in flatworm abundance and current speed. The abundance of flatworms declined with increasing current speed, thereby creating the potential for sites with high flows to provide larvae with a refuge from these predators. Multiple regression analysis revealed that the final abundance of larvae exhibited a significant negative relationship to flatworm abundance and a significant positive relationship to current speed. After adjusting for variations in elapsed time and initial larval abundance, flow and predators explained 38% of the variation in the rate of change in larval abundance. The positive correlation between larval abundance and flow had two components: a positive, direct effect of flow on larvae, which arises because these food-limited consumers prefer to reside within sites with faster flows where they can feed at higher rates; and a negative effect of flow on predators, and of predators on larvae, which combine to yield a positive indirect effect of flow on larvae. This indirect effect demonstrates the existence of flow-mediated refuges (i.e., microhabitats in which the impact of predation is reduced due to high flows), although the effect accounts for a small proportion of total variation in larval abundance. A consideration of biomechanical relationships suggests that microhabitats with high flows are likely to create prey refuges in a wide range of freshwater and marine benthic environments. In particular, predators will often experience greater dislodgement forces than prey because of their larger size and because they project farther above the bed where current speeds are faster. Moreover, the ability to resist a given dislodgement force may be greater for many prey, especially those that are sessile or semi- sessile.

Plant—herbivore interactions in streams near Mount St Helens

SUMMARY1. In four separate field experiments near Mount St Helens (Washington, U.S.A.) during 1986, the grazing effects of two large benthic herbivores, tadpoles of the tailed frog Ascaphus truei and larvae of the caddisfly Dicosmoecus gilvipes, were investigated using streamside channels and in‐stream manipulations. In the experimental channels, abundances of periphyton and small benthic invertebrates declined significantly with increasing density of these larger herbivores.2. In eleven small, high‐gradient streams affected to varying degrees by the May 1980 eruption, in‐stream platforms were used to reduce grazing by A, truei tadpoles on tile substrates. Single platforms erected in each tributary and compared to grazed controls revealed only minor grazing effects, and no significant differences among streams varying in disturbance intensity (and, consequently, tadpole density). However, results probably were confounded by high variability among streams in factors other than tadpole abundance.3. Grazing effects were further examined in two unshaded streams with different tadpole densities, using five platforms per stream. In the stream with five tadpoles m−2, grazing reduced periphyton biomass by 98% and chlorophyll a by 82%. In the stream lacking tadpoles, no significant grazing effects were revealed. Low algal abundance on both platforms and controls, and high invertebrate density in that stream (c. 30000m−2) suggests that grazing by small, vagile invertebrates was approximately equivalent to that of tadpoles.4. The influence of large benthic herbivores on algal and invertebrate communities in streams of Mount St Helens can be important, but reponses vary spatially in relation to stream disturbance history, local environmental factors, and herbivore distributional patterns and abundance.

Spawning Success of Fathead Minnows on Selected Artificial Substrates

Abstract Spawning success of fathead minnows (Pimephales promelas) on six different substrates was tested and evaluated. Egg adhesiveness was equally good on cement-asbestos tile and sand-coated stainless steel substrates, but was poor on unaltered stainless steel, shot-peened stainless steel, stainless steel screen, and glass substrates. Viability and number of eggs spawned were not significantly different for any of the substrates tested.

An optimized hard surface cleaning test

AbstractPreliminary investigation of several test procedures resulted in the selection of the Liss‐Hilton reflectance method. A white vinyl tile substrate was selected and the test method optimized at cleaning efficiencies of approximately 30% for water and 80% for selected detergent compositions. Within‐series and between‐series variations, in general, met a required 2% maximum. Between‐laboratories data were slightly more variable. Utilizing the corresponding confidence limit factor, as few as three test panels per detergent may be used to compare detergent cleaning efficiencies.