Formation of a new solid β tricalcium orthophosphate structure,from reaction between hydroxyapatite and ammonium sulfate

The reaction which occur during heating, from room temperature to 1100°C, of a mixture of hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂ [HAP] and ammonium sulfate (NH₄)₂SO₄ [AS] are studied. The formation of Ca₂(NH₄)₂(SO₄)₃, Ca₂P₂O₇ and Ca(PO₃)₂ is observed between 200°C and 300°C; at 400°C CaSO₄ appears. From 500 to 700°C, Ca(PO₃)₂ reacts with Ca SO₄ and with HAP and gives β-Ca₂P₂O₇. Lastly, from 700°C to 1000°C, β-Ca₂P₂O₇ reacts with HAP and with CaSO₄ and gives β-Ca₃(PO₄)₂ [β-TCP]; From 1000 to 1100°C, β-TCP and CaSO₄ react and form a sulfate ion containing calcium phosphosulfate, the structure of which is β-TCP     

Sensitivity of a wide-band F.I.R. receiver using a Josephson self oscillator mixer

The system temperature of a receiver using a Josephson junction as a self oscillator mixer has been measured in the range 0.6 to 2 THz. The experimental value T_S=53000K (DSB) at 900 GHz is in good agreement with the calculated value. A T_S～12 000 K is predicted with a 30 K i.f. amplifier Possible applications are related to fast frequency tunable receivers (over one octave) with limited spectral resolution.     

Defects in carbon nanotubes

Carbon nanotubes are quasi one-dimensional nanostructures with unique eletrical prroperties that make them prime candidates for molecular electronics, which is certainly a most promising direction in nanotechnology. Early theoretical works predicted that the electronic properties of "ideal" carbon nanotubes depend on their diameter and chirality. However, carbon nanotubes are probably not as perfect as they were once thought to be. Defects such as pentagons, heptagons, vacancies, or dopant are found to modify drastically the electronic properties of these nanosystems. Irradiation processes can lead to interesting, highly defective nanostructures and also to the coalescence of nanotubes within a rope. The introduction of defects in the carbon network is thus an interesting way to tailor its intrinsic properties, to create new potential nanodevices. The aim of the present Acount is to investigate theoretically the effects of different types of defects on the electronic properties of carbon nanotubes, and to propose new potential applications in nanoelectronics.     

氮源用量对杨木白腐菌降解效率的影响

通过调整培养基中氮源的含量,利用白腐菌Phanerochaete chryscoporium和Trametes versicolor对杨木木片处理28 d,分析了木片的质量得率及化学成分的变化.结果表明:当酵母浸出粉的用量为1 g.L-1时白腐菌对原料中的木素降解率最高,在氮源用量相同的情况下,白腐菌Phanerochaete chryscoporium比Tranetes versicolor降解木素的速率更快.     

Leakage Targets and Socio-Economic Efficiency

During the last few years, the introduction of mandatory leakage targets for UK water companies has had the positive effect of reducing levels of leakage, while requiring the companies to operate at an economic level of leakage. Unfortunately, the determination of company-specific economic levels of leakage have been a source of disagreement between the water companies and the Government, with the Government view that water companies are not using the true long-term marginal costs of water abstraction, and therefore are not safeguarding the environment.
This paper (a) reviews the model which was used to define the economic level of leakage, (b) argues the case for resource management based on the impact of water abstractions on the socio-environmental quality of a resource rather than the myopic focus on leakage reductions, (c) presents the concepts of effectiveness and efficiency in relation to socio-environmental quality, and (d) proposes a new methodology which allows the determination of water abstraction rates while maintaining a desired level of socio-environmental quality.     

Initial results of remediation activities to restore hypereutrophic Villerest Reservoir (Roanne, France)

We examined the impacts of remediation activities aimed at improving the water quality of hypereutrophic Villerest Reservoir, in which Microcystis aeruginosa dominated during the summer. We also compared nutrients and chlorophyll a data from this study with the results of a previous study on the reservoir. Between the two studies, the nitrogen and phosphorus loads into the reservoir from the main tributary decreased by 70% and 80%, respectively. Within the reservoir, the quantities of ammonia‐nitrogen were similar in the two studies, and the total nitrogen was significantly higher in this study compared to the initial study. Both the phosphate‐phosphorus and total phosphorus concentrations decreased significantly between the two studies. However, the statistically significant decrease in phosphate‐phosphorus and total phosphorus did not always lead to a significant decrease in chlorophyll a concentrations. The nitrogen/phosphorus mass ratio during the present study remained well above five, the critical value below which summer blooms of Microcystis aeruginosa were observed in Villerest Reservoir. These study results indicated that the remediation activities being used to improve the water quality of Villerest Reservoir were off to a good start.     

Organotin levels in seafood and its implications for health risk in high-seafood consumers

Fish and fishery products are considered as the main source of organotin compounds (OTC). Unfortunately, little national contamination data is available to assess food exposure of organotins from French consumers. To provide a more accurate estimate of risks to human health, the butyltin, phenyltin and octyltin compounds sampling in four French coastal areas were measured in 159 composite samples (96 fresh and frozen fish, 28 mollusks, 14 crustaceans, 1 echinoderm, 11 canned foods, 4 smoked fish, 5 prepared seafood-based dishes) by capillary gas chromatography coupled with a microwave induced plasma atomic-emission spectrometer (CGC-MIP-AES). In these samples, butyltins were usually predominant and the range of the contamination levels was generally below those of earlier studies (fish: mean 5.6; min-max 1.1-23 microg/kg; fishery products: mean 6; min-max 0.8-14 microg/kg). Fish, especially tuna, salmon, mackerel, saithe/coalfish and cod were largely the main contributors (38%) to the total organotin exposure. With the supplementary contribution of great scallop, surimi, squid and oysters, the exposure exceeded 50% in all. However, the utmost OTC exposure was lesser than 47% of the provisional tolerable weekly intake [EFSA (European Food Safety Agency). Opinion of the Scientific Panel on Contaminants in the food chain on a request from the Commission to assess the health risks to consumers associated with exposure to organotins in foodstuffs. (Question N EFSA-Q-2003-110). The EFSA Journal, 102, 1-119, 2004. http://www.efsa.eu.int]. Nobody would exceed this limit. Finally, as this study has some limitations and since some other sources and health effects have not been clearly evaluated, it appears rational from public health and environmental viewpoints to continue to reduce the OTC levels in the environment.     

High resolution profiles of thallium, manganese and iron assessed by DET and DGT techniques in riverine sediment pore waters

High resolution profiles of Mn, Tl and Fe concentrations have been assessed in the pore waters of river Leie sediments at Warneton and Menen (at the border of Belgium and France) by DET (Diffusive Equilibrium in Thin Films) and DGT (Diffusive Gradients in Thin Films) techniques. The oxidized, solid Mn (IV), Tl (III) and Fe (III) compounds were reduced in the suboxic (+255 to -20 mV versus Standard Hydrogen Electrode (SHE)) riverine sediments and since these reduced species are much more soluble also they are released into the pore waters. The highest DET (total dissolved) concentrations of Fe (76 mg l(-1)), Mn (2 mg l(-1)) were observed at the station of Menen, while Tl maxima differed only slightly between the 3 surveys (21 to 27 microg l(-1)). The average ratios of Fe/Mn/Tl in the pore waters at the 3 sampling stations are fairly constant for both the DET and DGT samplings. However, the results indicate that compared to Fe and Tl a greater proportion of the Mn measured by DET is accumulated by DGT, reflecting the ready supply of Mn from solid phase to solution.     

Oxidized copper phase precipitation in ammoniacal leaching — the influence of ammonium salt additions

In oxidative ammoniacal leaching of some copper sulfides, the dissolution of copper is slowed down by the precipitation of an oxidized phase which is identified as a hydrated tenorite.A simple set of mass balance equations permits determination of the stability limits of the copper ions in ammoniacal solutions with or without acidic ammonium salts.