Dual second harmonic generation and up-conversion photoluminescence emission in highly-optimized LiNbO3 nanocrystals doped and co-doped with Er3+ and Yb3

Preparation from the aqueous alkoxide route of doped and co-doped lithium niobate nanocrystals with Er3+ and Yb3+ ions, and detailed investigations of their optical properties are presented in this comprehensive work. Simultaneous emission under femtosecond laser excitation of second harmonic generation (SHG) and up-conversion photoluminescence (UC-PL) is studied from colloidal suspensions according to the lanthanide ion contents. Special attention has been paid to produce phase pure nanocrystals of constant size (∼20 nm) thus allowing a straightforward comparison and optimization of the Er content for increasing the green UC-PL signals under 800 nm excitation. An optimal molar concentration at about 4 molar% in erbium ions is demonstrated, that is well above the concentration usually achieved in bulk crystals. Similarly, for co-doped LiNbO3 nanocrystals, different lanthanide concentrations and Yb/Er content ratios are tested allowing optimization of the green and red up-conversion excited at 980 nm, and analysis of the underlying mechanisms from excitation spectra. All together, these findings provide valuable insights into the wet-chemical synthesis and potential of doped and co-doped LiNbO3 nanocrystals for advanced applications, combining both SHG and UC-PL emissions from the particle core.

Advanced magnetic resonance imaging (MRI) techniques of the spine and spinal cord in children and adults

Abstract

In this article, we illustrate the main advanced magnetic resonance imaging (MRI) techniques used for imaging of the spine and spinal cord in children and adults. This work focuses on daily clinical practice and aims to address the most common questions and needs of radiologists. We will also provide tips to solve common problems with which we were confronted. The main clinical indications for each MR technique, possible pitfalls and the challenges faced in spine imaging because of anatomical and physical constraints will be discussed. The major advanced MRI techniques dealt with in this article are CSF, (cerebrosopinal fluid) flow, diffusion, diffusion tensor imaging (DTI), MRA, dynamic contrast-enhanced T1-weighted perfusion, MR angiography, susceptibility-weighted imaging (SWI), functional imaging (fMRI) and spectroscopy.

Teaching Points

• DWI is essential to diagnose cord ischaemia in the acute stage.

• MRA is useful to guide surgical planning or endovascular embolisation of AVMs.

• Three Tesla is superior to 1.5 T for spine MR angiography and spectroscopy.

• Advanced sequences should only be used together with conventional morphological sequences.

Selection of native Tunisian microalgae for simultaneous wastewater treatment and biofuel production

This paper focuses on the selection of native microalgae strains suitable for wastewater treatment and biofuel production. Four Chlorophyceae strains were isolated from North-eastern Tunisia. Their performances were compared in continuous mode at a 0.3 1/day dilution rate. The biomass productivity and nutrient removal capacity of each microalgae strain were studied. The most efficient strain was identified as Scenedesmus sp. and experiments at different dilution rates from 0.2 to 0.8 1/day were carried out. Maximal biomass productivity of 0.9 g/L day was obtained at 0.6 1/day. The removal of chemical oxygen demand (COD), ammonium and phosphorus was in the range of 92-94%, 61-99% and 93-99%, respectively. Carbohydrates were the major biomass fraction followed by lipids and then proteins. The saponifiable fatty acid content was in the 4.9-13.2% dry biomass range, with more than 50% of total fatty acids being composed of saturated and monosaturated fatty acids.

Correlation between pre- and postnatal cerebral magnetic resonance imaging

OBJECTIVES

To evaluate the diagnostic accuracy of fetal cerebral magnetic resonance imaging (MRI) on a large cohort and to compare pre- and postnatal MRI data.

METHODS

This prospective study included all cases referred to our unit for fetal cerebral MRI examination between June 2006 and December 2009 and which underwent at least one postnatal MRI examination. Cases in which there was termination of pregnancy, fetal death or stillbirth were excluded. The pre- and postnatal diagnoses established by MRI were compared and divided into five subgroups: same diagnosis on pre- and postnatal MRI (Group 1); same diagnosis but different appearance related to the natural course of the disease (Group 2); different diagnosis (related to limitations of fetal MRI) (Group 3); same diagnosis but with additional findings discovered on postnatal MRI examination (Group 4); or same diagnosis but different appearance related to the natural course of the disease (as in Group 2) and associated with additional findings discovered on postnatal MRI examination (Group 5). The prognostic impact of a possible disagreement between pre- and postnatal findings was evaluated.

RESULTS

One hundred fetuses were included. Fetal MRI was performed at a mean gestational age of 33 (range, 24-39) weeks and postnatal MRI at a mean age of 3.5 months. There were 53 cases classified as Group 1, 32 in Group 2, four in Group 3, 10 in Group 4 and one in Group 5. Thus, in 15 cases (Groups 3-5), there were discrepancies between pre- and postnatal findings (mostly related to corpus callosum anatomy, cortical and migration disorders). The discrepancy was judged to have a prognostic impact in 9/15 cases. Two postnatal MRI examinations were performed in eight cases, in one of which the second examination showed subependymal heterotopia which were not detectable on the first examination.

CONCLUSION

Pre- and postnatal MRI data showed good agreement in 85% of cases. There was disagreement with a prognostic impact in 9% of cases.

A comparative study on the anaerobic membrane bioreactor performance during the treatment of domestic wastewaters of various origins

This study examined the practical performance of a cross-flow ultrafiltration membrane coupled to an anaerobic bioreactor, for treatment of raw domestic wastewater (RDW), at a pilot-scale plant. Wastewaters used in this study originated from two different domestic wastewater treatment plans (DWTPs) (Sfax and Ksour Essef). During the treatment in the membrane bioreactor (MBR) of the RDW originating from Sfax DWTP, the bioreactor did not reach its stationary phase because the anaerobic biomass was unable to adapt to the wastewater. This was explained by the considerable fluctuations in the domestic wastewater composition and a possible contamination of Sfax wastewater by industrial discharges. However, the treatment of RDW originating from Ksour Essef (DWTP) was successful. In both cases, the treatment led to a total removal of all tested pathogens. The quality of treated wastewater fits largely with WHO guidelines for unrestricted irrigation. The phytotoxicity and the microtoxicity tests, using Lepidium sativum and Vibrio fischeri respectively, demonstrated that wastewater from Sfax exhibited higher toxicity than that from Ksour Sssef.

Effect of bioaugmentation of activated sludge with white-rot fungi on olive mill wastewater detoxification

AIMS

To test the potential use of Phanerochaete chrysosporium and other white-rot fungi to detoxify olive mill wastewaters (OMW) in the presence of a complex activated sludge. To combine the aerobic with anaerobic treatment to optimize the conversion of OMW in biogas.

METHODS AND RESULTS

A 25-l air lift reactor was used to pretreat OMW by white-rot fungi. Detoxification of the OMW was monitored by size exclusion HPLC analysis, chemical oxygen demand (COD)/biological oxygen demand (BOD(5)) ratio evolution, and bioluminescence toxicity test. Anaerobic treatment of OMW was performed in a 12-l anaerobic filter reactor. Efficiency of the treatment was evaluated by organic matter removal, and biogas production. By comparison with the pretreatment by activated sludge only, the bioaugmentation with Phanerochaete chrysosporium or Trametes versicolor led to high removal of organic matter, decreased the COD/BOD(5) ratio and the toxicity. The subsequent anaerobic digestion of the OMW pretreated with activated sludge-white-rot fungi showed higher biomethanization yields than that pretreated with activated sludge only. Higher loading rates (7 g COD l(-1) day(-1)) were reached without any acidification or inhibition of biomethanization.

CONCLUSIONS

The use of white-rot fungi, even in the presence of complex biological consortia to detoxify OMW, proved to be possible and made the anaerobic digestion of OMW for methane production feasible.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of fungi for OMW reuse and energy production could be adapted to industrial applications.

Olive mill wastewater sludge from evaporation ponds: evolution of physico-chemical parameters during storage and composting process

The evolution of analytical parameters of olive mill waste water sludge stored in evaporation ponds was investigated after one year and two years of storage. It was observed that some of the phenolic monomer compounds resisted removal and the fraction of water soluble phenols was only slightly polymerised. Co-composting of the sludge was carried out with yard trimming as bulking agent ratio and poultry manure to balance the C/N. Three turned piles with three proportions of 35%, 65% and 80% of olive mill waste water sludge were prepared. Co-composting of the sludge was possible in all the cases. Best results were obtained, however, at a proportion of 35% which permitted a shorter composting time, a higher degree of nitrification and a higher rate of total phenols decreasing. A high polymerisation of the fraction of water soluble phenols was observed at the end of composting in all the piles.

Dromedary milk lactic acid fermentation: microbiological and rheological characteristics

The ability of dromedary skim milk to form an acid curd during a lactic acid starter fermentation was investigated. The activity of the starter in dromedary milk was characterized by a longer lag phase ( approximately 5 vs. approximately 1 h) and by an earlier decline phase. This suggests the presence of inhibiting factors. The maximum buffering capacity of dromedary milk as well as its minimum apparent viscosity were obtained at lower pH values. Similarly, its elastic modulus appeared later (pH 5.7 vs. 6.3). Because these rheological and biochemical events took place at lower pH values, dromedary skim milk seems to present a higher physical stability toward the increase of acidity. Determination of the rheological and microscopic characteristics of the dromedary milk coagulum (pH 4.4) did not reveal curd formation but indicated a fragile and heterogeneous structure. This coagulum, which is very different from that of cows' milk, seems to be made up of dispersed casein flakes.