Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores

Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500 degrees C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35 degrees to 80 degrees C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The block copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140 degrees C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water.     

Productivity is a poor predictor of plant species richness

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters(-2)) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness.     

First-principles theory for the H + H2O, D2O reactions

A full quantum dynamical study of the reactions of a hydrogen atom with water, on an accurate ab initio potential energy surface, is reported. The theoretical results are compared with available experimental data for the exchange and abstraction reactions in H + D2O and H + H2O. Clear agreement between theory and experiment is revealed for available thermal rate coefficients and the effects of vibrational excitation of the reactants. The excellent agreement between experiment and theory on integral cross sections for the exchange reaction is unprecedented beyond atom-diatom reactions. However, the experimental cross sections for abstraction are larger than the theoretical values by more than a factor of 10. Further experiments are required to resolve this.     

Acute Toxicity and Anesthetic Effects of Clove Oil in Penaeus semisulcatus under Various Water Quality Conditions

Acute toxicity and anesthetic effects of clove oil were studied in P. semisulcatus (1.8–2.1 g body weight). The EC₅₀ 1-h (the concentration effective for 50% of test animals), LC₅₀ 1-h (the concentration lethal to 50% of test animals after 1 h) and LC₅₀ 24-h (the concentration lethal to 50% of test animals after 24 h) were calculated at concentrations of 25, 130 and 30 mg/l, respectively, at 30°C, salinity 40 ppt, pH 8.6 and dissolved oxygen >6 mg/l. Generally, with increasing concentrations of clove oil, the times required for sedation and anesthesia decreased, while the recovery times increased. At concentrations 50, 100, 150 and 200 mg/l under temperature of 30°C and salinity of 40 ppt, the times required for sedation were 6 ± 0.2, 2.5 ± 0.3, 2 ± 0.08 and 0.5 ± 0.08 min, while times required for complete recovery were calculated to be 4.5 ± 0.3, 5.5 ± 0.17, 6.5 ± 0.25 and 11 ± 0.38 min, respectively. Also, the times required for deep anesthesia were 20 ± 1, 5 ± 0.5, 3 ± 0.4 and 2.2 ± 0.5 min in the above concentrations, while the times required for complete recovery were 10 ± 1, 11 ± 1.5, 14 ± 2.2 and 16 ± 3 min, respectively. Furthermore, considering the times to sedation, deep anesthesia and recovery at different temperatures of 20°C, 25°C, 30°C and 35°C and salinities of 25, 30, 35, 40 and 48 ppt; the combinations of salinity plus temperature and clove oil concentration plus salinity had the greatest and the least effects.     

A dietary modification approach to improve the osmoregulatory capacity of Litopenaeus vannamei cultured in the Arizona desert

A modified diet was formulated for Arizona inland shrimp farming and tested as a method for reducing moult‐associated mortalities presumed due to trace mineral deficiencies. The experimental diet was supplemented with additional dietary magnesium, potassium, phospholipids and cholesterol to a commercial shrimp feed (Rangen 45/10, which was also used as the control diet). The modified diet was tested at Arizona Mariculture Associates (AMA), while the control diet was used at a nearby inland shrimp farm, Desert Sweet Shrimp Farm (DSSF). Both feeds were used throughout the culture season of 2001. Earthen pond‐reared Litopenaeus vannamei at intermoult stages (C‐D₀) and ranging from 7 to 30 g were sampled at intervals for determination of haemolymph osmolality (HO). Results showed that the modified diet had not only resulted in larger size shrimp at harvest, but also improved osmoregulatory capacity (OC). HO of DSSF shrimp decreased as shrimp grew bigger, whereas HO of AMA shrimp was maintained at a stable level, or showed a slightly positive linear relationship with weight. The hyper‐OC of shrimp from AMA (462 mOsm kg^?1) was greater than that from DSSF (398 mOsm kg^?1). Shrimp at AMA fed the experimental diet presented no mass moult‐associated mortalities. To further investigate the iso‐osmotic point of shrimp reared in AMA, a group of six salinity gradients were designed by mixing oceanic salts into the well water to form 5, 8.5, 11.4, 14.4, 17.8, 20.7 p.p.t. medium. HO of subadult shrimp (25 g in average) were then evaluated 48 h after they had been transferred from 5 p.p.t. pond water to the medium. Shrimp HO increased with external salinity, and a plateau formed as salinity reached at 11.4 p.p.t. and higher. The iso‐osmotic point of shrimp was estimated to be 695.5 mOsm kg^?1, equivalent to 26.1 p.p.t. in AMA well water.     

Generation of Paramoeba perurans clonal cultures using flow cytometry and confirmation of virulence

Amoebic gill disease (AGD) in farmed Atlantic salmon is caused by the amoeba Paramoeba perurans. The recent establishment of in vitro culture techniques for P. perurans has provided a valuable tool for studying the parasite in detail. In this study, flow cytometry was used to generate clonal cultures from single‐sorted amoeba, and these were used to successfully establish AGD in experimental Atlantic salmon. The clonal cultures displayed differences in virulence, based on gill scores. The P. perurans load on gills, determined by qPCR analysis, showed a positive relationship with gill score, and with clonal virulence, indicating that the ability of amoebae to proliferate and/or remain attached on gills may play a role in virulence. Gill scores based on gross signs and histopathological analysis were in agreement. No association between level of gill score and specific gill arch was observed. It was found that for fish with lower gill scores based on histopathological examination, gross examination and qPCR analysis of gills from the same fish were less successful in detecting lesions and amoebae, respectively.     

A qPCR MGB probe based eDNA assay for European freshwater pearl mussel (Margaritifera margaritifera L.)

1. Environmental (e)DNA assays are becoming increasingly used to detect rare or invasive aquatic species. 2. The Critically Endangered freshwater pearl mussel Margaritifera margaritifera is undergoing range‐wide reduction in population numbers and distribution. 3. An eDNA assay to detect the presence of M. margaritifera was developed, based on the mitochondrial cytochrome oxidase I gene, utilizing species‐specific primers, a minor groove binding (MGB) probe and quantitative (q)PCR approaches. 4. The results from this pilot study demonstrated high sensitivity both in laboratory and field trials, and provide a valuable non‐invasive tool for detecting M. margaritifera.     

A conceptual production model for freshwater crayfish pond culture incorporating detrital forage

A production model is presented for semi-intensive freshwater crayfish culture ponds incorporating detrital forage. The conceptual model is developed from five submodels of trophic-dynamic interactions within the pond ecosystem. The model includes microbially enhanced detrital forage (MEDF) produced from plant matter grown in the pond as a significant component of nutrition. The model is proposed as an aid to understanding pond-based aquaculture techniques that rely upon manipulating the characteristics of MEDF. The significance of MEDF as a source of nutrition in aquaculture is discussed.     

Amplification of surface temperature trends and variability in the tropical atmosphere

The month-to-month variability of tropical temperatures is larger in the troposphere than at Earth's surface. This amplification behavior is similar in a range of observations and climate model simulations and is consistent with basic theory. On multidecadal time scales, tropospheric amplification of surface warming is a robust feature of model simulations, but it occurs in only one observational data set. Other observations show weak, or even negative, amplification. These results suggest either that different physical mechanisms control amplification processes on monthly and decadal time scales, and models fail to capture such behavior; or (more plausibly) that residual errors in several observational data sets used here affect their representation of long-term trends.