Can we determine if the linear nature of quantum mechanics is violated by the perceptual process?

It now appears feasible to be able to subject to experimental test Ghirardi's proposal concerning utilizing superposed photon states to check reduction mechanisms in perceptual processes which may be governed by nonlinear evolution laws. This can be accomplished with existing techniques involving superposed single photon states and living retinal tissue mounted on microelectrode arrays.     

Does the availability of arboreal honeydew determine the prevalence of ecologically dominant ants in restored habitats?

Ants are extensive users of arboreal sugars, but little is known about how ecological dominance or habitat succession influences this interaction. We investigated how the availability and use of arboreal sugar resources by ants changes across a restoration chronosequence. We surveyed the use and availability of hemipteran honeydew and floral nectar on the two dominant plant genera, Eucalyptus and Acacia, in study sites in south eastern Australia. Sugars used by ants are likely to drive their role as ecosystem engineers, while sugars not used by ants remain available to other organisms. We also tested whether the use of sugars differed between ecologically dominant and non-dominant ants; taxa likely to perform different functions in ecosystems. No floral nectar was available on Acacia, but later successional eucalypts supported more floral resources and fewer mutualist hemiptera. Successional stage significantly affected how much sugar remained unexploited by ants, with similar trends for ant use of sugars. Non-dominant ants used mainly floral nectar, while hemipteran honeydew resources were used disproportionately by dominant ants, consistent with the prediction that this group monopolises persistent carbohydrate resources. This pattern was similar across successional stages, but the difference was least in habitats with the greatest availability of floral nectar, suggesting that high sugar availability may reduce the incentive to defend honeydew. Across habitat types, the proportion of dominant ants increased with the availability of hemipteran honeydew. This suggests that honeydew availability may regulate ecological dominance, thus affecting ant-driven ecosystem processes.     

Does resource availability help determine the evolutionary route to multicellularity?

Genetic heterogeneity and homogeneity are associated with distinct sets of adaptive advantages and bottlenecks, both in developmental biology and population genetics. Whereas populations of individuals are usually genetically heterogeneous, most multicellular metazoans are genetically homogeneous. Observing that resource scarcity fuels genetic heterogeneity in populations, we propose that monoclonal development is compatible with the resource‐rich and stable internal environments that complex multicellular bodies offer. In turn, polyclonal development persists in tumors and in certain metazoans, both exhibiting a closer dependence on external resources. This eco‐evo‐devo approach also suggests that multicellularity may originally have emerged through polyclonal development in early metazoans, because of their reduced shielding from environmental fluctuations.     

Is the bioavailability index applicable for trace elements in different types of soil?

Abstract

The bioavailability index (BI) is defined as the proportion of reduction in a plant’s accumulation of an element, caused by the removal of the extractable fraction of the element of interest from the soil. The BI and corresponding experimental methods were quantitatively applied to evaluate the bioavailability of trace elements in five Chinese soils. The soil was first extracted with various reagents (DTPA, HCl and NH₂OH.HCI) separately, to remove the extractable elements. The soil, after extraction, was washed with deionised water to eliminate the extractant used in the fractionation analysis. Then the pH of the soil was re-adjusted with CaO. The soil was then fertilised and incubated in a greenhouse for four weeks. Tests showed that after incubation the pH, cation exchange capacity (CEC) and organic matter (OM) of the treated soil were close to their original values. Wheat (Triticum aestivum L.) was planted in both the untreated and treated soil for eight weeks. After harvest the plant concentrations of the elements Cr, Mn, Co, Ni, Zn, Cu, Cd, and Pb were analysed by inductively coupled plasma mass spectrometry (ICPMS). Trace element accumulation by plants grown in the treated soil was reduced significantly compared with that of plants grown in the untreated soil. The results showed that BI values were in the order BI(DTPA)>BI(HCl)>BI(NH₂OH.HCl). This indicated that the DTPA-extractable fraction represented a highly available fraction of the total content. Variations of BI among different trace elements show that Cr, Mn, Zn and Co have a higher BI, in general for the elements tested, whereas, Cu, Cd and Pb have lower values. There are also slight differences in the BI among soils. However, no significant relationship could be found between the BI and the soil characteristics.     

Can multiple harvest of aboveground biomass enhance removal of trace elements in constructed wetlands receiving municipal sewage?

Constructed wetlands for wastewater treatment in the Czech Republic are commonly planted with reed canarygrass (Phalaris arundinacea). Phalaris is a fast-growing grass which may be cut several times during the growing season. During 2005, the experiments were carried out at horizontal sub-surface flow constructed wetland B?ehov to evaluate whether multiple harvest may increase the amount of 23 trace elements removable via mowing. The plants were cut in mid-June and re-harvested in mid-August. The single harvest was carried out at the end of July during the peak standing crop of this species. The biomass of Phalaris cut once and twice during the year was nearly identical but analyses of the biomass indicated that the amount (standing stock) of trace elements varied. For 13 elements (As, Ba, Co, Cr, Cu, Fe, Ga, Hg, Mn, Ni, Pb, Sb and U) the standing stock was higher for single harvest, indicating that these trace elements are transported to the aboveground biomass later in the growing season. Standing stock found in the biomass harvested at the peak standing crop as percentage of the cumulative standing stock from two harvests was highest for Hg (385%), Pb (249%) and U (244%). On the other hand, for 10 elements (Al, Cd, Li, Mo, Rb, Se, Sn, Sr, Tl and Zn) cumulative standing stock was higher than the standing stock for one harvest, indicating high accumulation during the early growth stages. For those elements, multiple harvest could be beneficial for element removal from wastewater.     

Do trace elements modify the activity of erythrocyte sodium-proton exchanger in hemodialyzed patients?

The kinetics (V _max and K _m ) of the erythrocyte Na⁺−H⁺ exchanger was studied in a group of 21 patients undergoing regular hemodialysis (HD) and in 21 control subjects. The activity of antioxidative enzymes—superoxide dismutase and glutathione peroxidase—as well as the concentrations of their cofactors—zinc, copper, and selenium—in plasma and in erythrocytes were determined. The thiobarbituric acid-reactive substances (TBARS) concentration served as an indicator of oxidative stress intensity in plasma and erythrocytes. It was found that in the control group the concentration of copper in erythrocytes was positively correlated with K _m and V _max. When the concentration of copper increased, the shape of the kinetic curve changed from sigmoidal to hyperbolic. In the control group, the concentration of zinc in erythrocytes also correlated with K _m . However, the results obtained for the group of hemodialyzed patients were the opposite: when the erythrocyte concentration of copper increased, a K _m decline was observed and the shape of the curve changed from hyperbolic to sigmoidal. In the group of hemodialyzed patients, we also found a positive correlation between K _m and the concentration of selenium in erythrocytes, and a negative correlation between K _m and erythrocyte TBARS.     

Can the size of the epiphysis determine the number of secondary ossification centers? A mathematical approach

Previous studies have concluded that the chemical feedback (loop) between two reagent molecular factors through a reaction-diffusion mechanism could explain the stable spatial pattern found in the origin of the secondary ossification centres (SOCs). Furthermore, the emergence of the SOC may depend on the size and shape of the head of the bone, as observed in different animals. In this paper, we develop new computer simulations that study the effect of the size of the epiphysis on the emergence of the SOC. This study determines two or more SOCs, that may appear in the head of long bones, depending on the size of the epiphysis.     

Can the size of the epiphysis determine the number of secondary ossification centers? A mathematical approach

Previous studies have concluded that the chemical feedback (loop) between two reagent molecular factors through a reaction–diffusion mechanism could explain the stable spatial pattern found in the origin of the secondary ossification centres (SOCs). Furthermore, the emergence of the SOC may depend on the size and shape of the head of the bone, as observed in different animals. In this paper, we develop new computer simulations that study the effect of the size of the epiphysis on the emergence of the SOC. This study determines two or more SOCs, that may appear in the head of long bones, depending on the size of the epiphysis.     

Can sequence determine function?

The functional annotation of proteins identified in genome sequencing projects is based on similarities to homologs in the databases. As a result of the possible strategies for divergent evolution, homologous enzymes frequently do not catalyze the same reaction, and we conclude that assignment of function from sequence information alone should be viewed with some skepticism.     

Can we ever identify the Urmetazoan?

Unraveling the root of the metazoan tree of life has been adifficult task since the time of Haeckel and the invention ofphylogenetics. Even considerable amounts of recent moleculardata have not provided a generally accepted answer. Here, wereview the major problems of this phylogenetic conundrum andprovide some directions for solving it.     

Can a minority of informed leaders determine the foraging movements of a fish shoal?

There is no information on whether the daily foraging movements of fish shoals are the result of chance, the collective will of all shoalmates, or the leadership of a few individuals. This study tested the latter possibility. Shoals of 12 golden shiners, Notemigonus crysoleucas, were trained to expect food around midday in one of the brightly lit corners of their tank. They displayed daily food-anticipatory activity by leaving the shady area of their tank and spending more and more time in the food corner up to the normal time of feeding. Past this normal time they remained in the shade, even on test days when no food was delivered. Most of these experienced individuals were then replaced by na?ve ones. The resulting ratio of experienced:na?ve fish could be 5:7, 3:9 or 1:11. On their own, na?ve individuals would normally spend the whole day in the shade, but in all tests the experienced individual(s) were able to entrain these more numerous na?ve fish out of the shade and into the brightly lit food corner at the right time of day. Entrainment was stronger in the 5:7 than in the 1:11 experiment. The test shoals never split up and were always led by the same fish, presumably the experienced individuals. These results indicate that in a strongly gregarious species, such as the golden shiner, a minority of informed individuals can lead a shoal to food, either through social facilitation of foraging movements or by eliciting following behaviour. Copyright 2000 The Association for the Study of Animal Behaviour.     

Can we model the probability of presence of species without absence data?

In ecological studies, it is useful to estimate the probability that a species occurs at given locations. The probability of presence can be modeled by traditional statistical methods, if both presence and absence data are available. However, the challenge is that most species records contain only presence data, without reliable absence data. Previous presence‐only methods can estimate a relative index of habitat suitability, but cannot estimate the actual probability of presence. In this study, we develop a presence and background learning algorithm (PBL) that is successful in modeling the conditional probability of presence of a simulated species. The model is trained by two completely separate sets: observed presence and background data. Assuming that the probability of presence is one for ‘prototypical presence’ locations where the habitats are maximally suitable for a species, we can estimate a constant that can calibrate the trained model into the actual probability of presence. Experimental results show that the PBL method performs similarly to a presence‐absence method, and significantly better than the widely used maximum entropy method. The new algorithm enables us to model the probability that a species occurs conditional on environmental covariates without absence data. Hence, it has potential to improve modeling of the geographical distributions of species.     

Can we predict biological activity of antimicrobial peptides from their interactions with model phospholipid membranes?

Cationic antibacterial peptides are produced in all living organisms and possess either selective activity toward a certain type of cell or microorganism, or a broad spectrum of activity toward several types of cells including prokaryotic and mammalian cells. In order to exert their activity, peptides first interact with and traverse an outer barrier, e.g., mainly LPS and peptidoglycan in bacteria or a glycocalix layer and matrix proteins in mammalian cells. Only then, can the peptides bind and insert into the cytoplasmic membrane. The mode of action of many antibacterial peptides is believed to be the disruption of the lipidic plasma membrane. Therefore, model phospholipid membranes have been used to study the mode of action of antimicrobial peptides. These studies have demonstrated that peptides that act preferentially on bacteria are also able to interact with and permeate efficiently anionic phospholipids, whereas peptides that lyse mammalian cells bind and permeate efficiently both acidic and zwitterionic phospholipids membranes, mimicking the plasma membranes of these cells. It is now becoming increasingly clear that selective activity of these peptides against different cells depends also on other parameters that characterize both the peptide and the target cell. With respect to the peptide's properties, these include the volume of the molecule, its structure, and its oligomeric state in solution and in membranes. Regarding the target membrane, these include the structure, length, and complexity of the hydrophilic polysaccharide found in its outer layer. These parameters affect the ability of the peptides to diffuse through the cell's outer barrier and to reach its cytoplasmic plasma membrane.     

Can measures of prey availability improve our ability to predict the abundance of large marine predators?

Apex marine predators can structure marine communities, so factors underlying their abundance are of broad interest. However, such data are almost completely lacking for large sharks. We assessed the relationship between tiger shark abundance, water temperature, and the availability of a variety of known prey over 5 years in Western Australia. Abundance of sharks in four size categories and the density of prey (cormorants, dugongs, sea snakes, sea turtles) were indexed using daily catch rates and transects, respectively. Across all sizes, thermal conditions were a determinant of abundance, with numerical peaks coinciding with periods of high water temperature. However, for sharks exceeding 300 cm total length, the inclusion of dugong density significantly improved temperature-based models, suggesting that use of particular areas by large tiger sharks is influenced by availability of this sirenian. We conclude that large marine predator population models may benefit from the inclusion of measures of prey availability, but only if such measures consider prey types separately and account for ontogenetic shifts in the diet of the predator in question. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.