Bioactive hydroxyapatite coating on titanium-niobium alloy through a sol-gel process

Hydroxyapatite (HA) was coated on the surface of a titanium-niobium (Ti-Nb) alloy by a sol-gel process. Triethyl phosphite and calcium nitrate were used as the phosphorus (P) and calcium (Ca) precursors respectively to prepare a Ca/P sol solution. The Ti-Nb alloy was dip-coated in the sol and heated at 600°C for 30 minutes. X-ray diffraction (XRD) analysis indicated the major phase constituent of the coating after heat treatment was HA. Scanning electron microscopy (SEM) observation showed that a few cracks were distributed on the HA coating. The in-vitro bioactivity of the HA coated Ti-Nb alloy was assessed using a cell culture of SaOS-2 osteoblast-like cells. The density of cell attachment was determined by MTT assay; the cell morphology was observed by SEM. Results indicated that the density of cell attachment on the surface of the Ti-Nb alloy was significantly increased by HA coating. Cell morphology observation showed that cells attached, spread and grew well on the HA coated surface. It can be concluded that the HA coating improved the in-vitro bioactivity of Ti-Nb alloy effectively.

Quantification of allochthonous nutrient input into freshwater bodies by herbivorous waterbirds

1. Waterbirds are considered to import large quantities of nutrients to freshwater bodies but quantification of these loadings remains problematic. We developed two general models to calculate such allochthonous nutrient inputs considering food intake, foraging behaviour and digestive performance of waterbirds feeding in terrestrial habitats: an intake model (IM), mainly based on an allometric relationship for energy requirements and a dropping model (DM), based on allometric relationships for defaecation.

2. Reviewed data of nitrogen (N) and phosphorus (P) content of herbivorous food varied according to diet type (foliage, seeds and roots), season and fertilization. For model parameterization average foliage diet contained 38.20 mg N gp>−1p> and 3.21 mg P gp>−1p> (dry weight), whereas mean faeces composition was 45.02 mg N gp>−1p> and 6.18 mg P gp>−1p>.

3. Daily allochthonous nutrient input increased with body mass ranging from 0.29 g N and 0.03 g P in teals Anas crecca to 5.69 g N and 0.57 g P in mute swans Cygnus olor. Results from IM differed from those of DM from ducks to swans by 63–108% for N and by −4 to 23% for P. Model uncertainty was lowest for the IM and mainly caused by variation in estimates of food retention time (RT). In DM food RT and dropping mass determined model uncertainty in similar extent.

4. Exemplarily applying the models to Dutch wetlands resulted in mean annual contribution of herbivorous waterbirds to allochthonous nutrient loading of 382.8 ± 167.1 tonnes N ap>−1p>and 34.7 ± 2.3 tonnes P ap>−1p>, respectively, which corresponds to annual surface-water loadings of 1.07 kg N hap>−1p> and 0.10 kg P hap>−1p>.

5. There was a distinct seasonal pattern with peak loadings in January, when bird abundances were highest. Lowest inputs were in August, when bird abundance and nutrient content in food was low and birds foraged less in terrestrial habitats. Three-quarters of all nutrient input was contributed by greater white-fronted goose Anser albifrons, greylag goose Anser anser, wigeon Anas penelope and barnacle goose Branta leucopsis alone.

6. We provide general, easy to use calculation methods for the estimation of allochthonous nutrient inputs by waterbirds, which are applicable to a range of waterbird species, a variety of potential diets and feeding behaviours, and across spatial scales. Such tools may greatly assist in the planning and execution of management actions for wetland nutrient budgets.

Estimating the contribution of carnivorous waterbirds to nutrient loading in freshwater habitats

1. We estimated nitrogen (N) and phosphorus (P) loading into wetlands by carnivorous waterbirds with alternative physiological models using a food-intake and an excreta-production approach. The models were applied for non-breeding and breeding Dutch inland carnivorous waterbird populations to quantify their contribution to nutrient loading on a landscape scale.

2. Model predictions based on food intake exceeded those based on excretion by 59–62% for N and by 2–36% for P, depending on dietary assumptions. Uncertainty analysis indicated that the intake model was most affected by errors in energy requirement, while the excretion model was dependent on faecal nutrient composition.

3. Per capita loading rate of non-breeders increased with body mass from 0.3–0.8 g N dayp>−1p> and 0.15 g P dayp>−1p> in little gulls Larus minutus to 4.5–11.5 g N dayp>−1p> and 2.1–3.2 g P dayp>−1p> in great cormorants Phalacrocorax carbo. For breeding birds, the estimated nutrient loading by a family unit over the entire breeding period ranged between 17.6–443.0 g N and 8.6 g P for little tern Sterna albifrons to 619.6–1755.6 g N and 316.2–498.1 g P for great cormorants.

4. We distinguished between external (i.e. importing) and internal (i.e. recycling) nutrient loading by carnivorous waterbirds. For the Netherlands, average external-loading estimates ranged between 38.1–91.5 tonnes N and 16.7–18.2 tonnes P per year, whilst internal-loading estimates ranged between 53.1–140.5 tonnes N and 25.2–39.2 tonnes P and per year. The average contribution of breeding birds was estimated to be 17% and 32% for external and internal loading respectively. Most important species were black-headed gull Larus ridibundus and mew gull Larus canus for external loading, and great cormorant and grey heron Ardea cinerea for internal loading.

5. On a landscape scale, loading by carnivorous waterbirds was of minor importance for freshwater habitats in the Netherlands with 0.26–0.65 kg N hap>−1p> ap>−1p> and 0.12–0.16 kg P hap>−1p> ap>−1p>. However, on a local scale, breeding colonies may be responsible for significant P loading.

Evaluation of salmon farming effects on marine systems in the inner seas of southern Chile : a large-scale mensurative experiment

The impact of salmon farming on the environment has been widely studied; there is, however, no consensus on the magnitude and quality of these effects and little information on their extent over large salmon farming areas. Forty-three salmon farm sites of which 29 are in full operation and grouped in nine locations in southern Chile were evaluated. Using statistical methods (two-way anova), no effects were found on water column variables such as nitrate, ammonia, orthophosphate and chlorophyll, whereas they were significant on sediment variables such as nitrogen (N), phosphorus (P) and organic carbon (OC), among others. Natural variability evaluation of some parameters revealed that P in sediments had the lowest coefficient of variation (23.2%) when compared with N (65.2%), particulate organic matter (POM) (139%) and OC (39%), and showed more marked salmon farming effects with no locality effects. Four of the nine locations showed stronger effects on sediments, with average P values ranging from 150 to 230 mmol that were six to nine times higher than in control sites (25 mmol). Nitrogen and carbon in sediments, while showing significant effects on salmon farming, also showed locality effects that revealed other biogenic processes influencing sediment composition. Thus, P in sediments was proposed as a promising indicator of impact on salmon farming, although the relationship with fauna in sediments was not linear and somewhat variable; more research is therefore needed to understand such connections. Considering entire geographical locations, no relationship was found between sediment conditions under salmon cages and the condition of the water column at a farm. This may indicate the possibility of high dilution rates and recycling processes, which so far preclude the detection of more global impacts beyond the cages shadow.

Toward design of synergistically active carbon-based catalysts for electrocatalytic hydrogen evolution

Replacement of precious Pt catalyst with cost-effective alternatives would be significantly beneficial for hydrogen production via electrocatalytic hydrogen evolution reaction (HER). All candidates thus far are exclusively metallic catalysts, which suffer inherent corrosion and oxidation susceptibility during acidic proton-exchange membrane electrolysis. Herein, based on theoretical predictions, we designed and synthesized nitrogen (N) and phosphorus (P) dual-doped graphene as a nonmetallic electrocatalyst for sustainable and efficient hydrogen production. The N and P heteroatoms could coactivate the adjacent C atom in the graphene matrix by affecting its valence orbital energy levels to induce a synergistically enhanced reactivity toward HER. As a result, the dual-doped graphene showed higher electrocatalytic HER activity than single-doped ones and comparable performance to some of the traditional metallic catalysts.

Estimation of nitrogen and phosphorus in effluent from the striped catfish farming sector in the Mekong Delta, Vietnam

In this study an attempt is made to estimate nitrogen and phosphorus discharged to the environment from the striped catfish (Pangasianodon hypophthalmus) farming sector in the Mekong Delta (8°33̕–10°55̕ N, 104°30̕–106°50̕ E), South Vietnam. The sector accounted for 687,000 t production in 2007 and 1,094,879 t in 2008, with over 95% of the produce destined for export to over 100 countries. Commercial and farm-made feeds are used in catfish farming, currently the former being more predominant. Nitrogen discharge levels were similar for commercial feeds (median 46.0 kg/t fish) and farm-made feeds (median 46.8 kg/t fish); whilst, phosphorus discharge levels for commercial feeds (median 14.4 kg/t fish) were considerably lower than for farm-made feeds (median 18.4 kg/t fish). Based on the median nutrient discharge levels for commercial feeds, striped catfish production in the Mekong Delta discharged 31,602 t N and 9,893 t P, and 50,364 t N and 15,766 t P in 2007 and 2008, respectively. However, the amount of nutrients returned directly to the Mekong River may be substantially less than this as a significant proportion of the water used for catfish farming as well as the sludge is diverted to other agricultural farming systems. Striped catfish farming in the Mekong Delta compared favourably with other cultured species, irrespective of the type of feed used, when the total amounts of N and P discharged in the production of a tonne of production was estimated.

Different complexation behavior of P-functionalized ferrocene derivatives towards SnCl2 , SnCl4 and SnPh2 Cl2 : auto-ionization and redox-type reactions

The novel phosphonyl-substituted ferrocene derivatives [Fe(η(5) -Cp)(η(5) -C5 H3 {P(O)(O-iPr)2 }2 -1,2)] (Fc(1,2) ) and [Fe{η(5) -C5 H4 P(O)(O-iPr)2 }2 ] (Fc(1,1') ) react with SnCl2 , SnCl4 , and SnPh2 Cl2 , giving the corresponding complexes [(Fc(1,2) )2 SnCl][SnCl3 ] (1), [{(Fc(1,1') )SnCl2 }n ] (2), [(Fc(1,1') )SnCl4 ] (3), [{(Fc(1,1') )SnPh2 Cl2 }n ] (4), and [(Fc(1,2) )SnCl4 ] (5), respectively. The compounds are characterized by elemental analyses, (1) H, (13) C, (31) P, (119) Sn NMR and IR spectroscopy, (31) P and (119) Sn CP-MAS NMR spectroscopy, cyclovoltammetry, electrospray ionization mass spectrometry, and single-crystal as well as powder X-ray diffraction analyses. The experimental work is accompanied by DFT calculations, which help to shed light on the origin for the different reaction behavior of Fc(1,1') and Fc(1,2) towards tin(II) chloride.