Phosphorus recovery from acidic wastewater by hydroxyapatite precipitation.

Phosphorus recovery from acidic wastewater was carried out using lime milk at various Ca/P molar ratios in the range of 0.6-1.8. A molar ratio of Ca/P of 1.4 and above gives an 80% recovery efficiency of phosphorus from the wastewater. The chemical and phase composition of the precipitated products was analyzed. The phase composition was determined qualitatively and quantitatively by X-ray analysis. Depending on the conditions of the precipitation reaction, impurities and additives (e.g. flocculants), various phase compositions and different mass fractions of the crystalline phase were obtained. The main phase component of the samples obtained by precipitation of phosphorus from effluent at a pH below 10 is brushite, above 10 it is hydroxyapatite. The high Ca/P molar ratio and long reaction time favour the formation of crystalline fractions and larger crystallites. The flocculant aid used in the study, to shorten the solid phase sedimentation time, has adversely affected the degree of crystallinity. A higher degree of crystallinity of the precipitate is beneficial as it promotes the effective separation of the precipitation reaction product from the liquid phase.

Light-induced confinement of electrons in stacked distorted graphene layers - a (TD-)DFT study.

Recently observed white-light emission from graphene ceramics cannot be explained by black body radiation theory because of a relatively low temperature of the sample. Furthermore the intensity of the emission stays at the same level even at temperatures as low as 10 K, indicating the purely electronic nature of the observed emission. In this work a model of light emission from locally interacting stacked graphene layers after intense continuous wave laser excitation is proposed. After a light-induced sp2 to sp3 change of the hybridization sp2-nanodomains surrounded by sp3 carbon atoms could be created and the electrons can be confined. Using DFT and TD-DFT methods followed by a molecular-like approach we examine the electronic structure and the optical properties of graphene (sp2,sp3)-clusters. We show the quantized and well separated energy levels of electrons from the domain's interior and the possibility of emission in the NIR/VIS/UV range.

Broadband anti-Stokes white emission of Sr2CeO4 nanocrystals induced by laser irradiation.

The laser induced white emission (LIWE) from Sr2CeO4 nanocrystals upon irradiation with a focused IR laser beam was investigated. It was observed to be a threshold phenomenon with its intensity increasing exponentially with the excitation power density. This process was investigated under double laser beam simultaneous excitation in the UV range leading to Stokes emission in the visible range and in the IR range leading to anti-Stokes LIWE. With increasing LIWE intensity, the Stokes emission intensity strongly decreased. The LIWE is accompanied by efficient photocurrent generation depending on laser excitation density followed by multiphoton absorption and ionization processes. Photoimpedance measurements showed a sharp increase of the dielectric constant by several orders of magnitude in the Sr2CeO4 nanocrystals during the LIWE process demonstrating a metallic-like behaviour. The mechanisms of LIWE include multiphoton absorption and ionization that lead to the creation of a coupled pair of Ce3+ and Ce4+ ions that allow for the intervalence charge transfer (IVCT) emission transitions in the white light range. A strong decrease of absorption band intensity of Sr2CeO4 with increasing LIWE intensity confirms the creation of (Ce3+, Ce4+) pairs.

Polymeric nanocapsules with up-converting nanocrystals cargo make ideal fluorescent bioprobes.

An innovative approach for up-converting nanoparticles adaptation for bio-related and theranostic applications is presented. We have successfully encapsulated multiple, ~8 nm in size NaYF4 nanoparticles inside the polymeric nanocarriers with average size of ~150 nm. The initial coating of nanoparticles surfaces was preserved due to the hydrophobic environment inside the nanocapsules, and thus no single nanoparticle surface functionalization was necessary. The selection of biodegradable and sugar-based polyelectrolyte shells ensured biocompatibility of the nanostructures, while the choice of Tm(3+) and Yb(3+) NaYF4 nanoparticles co-doping allowed for near-infrared to near-infrared bioimaging of healthy and cancerous cell lines. The protective role of organic shell resulted in not only preserved high up-converted emission intensity and long luminescence lifetimes, without quenching from water environment, but also ensured low cytotoxicity and high cellular uptake of the engineered nanocapsules. The multifunctionality of the proposed nanocarriers is a consequence of both the organic exterior part that is accessible for conjugation with biologically important molecules, and the hydrophobic interior, which in future application may be used as a container for co-encapsulation of inorganic nanoparticles and anticancer drug cargo.

Two blinking mechanisms in highly confined AgInS2 and AgInS2/ZnS quantum dots evaluated by single particle spectroscopy.

Ternary AgInS2 quantum dots (QDs) have been found as promising cadmium-free, red-shifted, and tunable luminescent bio-probes with efficient Stokes and anti-Stokes excitations and luminescence lifetimes (ca. 100 ns) convenient for time resolved techniques like fluorescence life-time imaging. Although the spectral properties of the AgInS2 QDs are encouraging, the complex recombination kinetics in the QDs being still far from understood, limits their full utility. In this paper we report on a model describing the recombination pathways responsible for large deviations from the first-order decay law observed commonly in the ternary chalcogenides. The presented results were evaluated by means of individual AgInS2 QD spectroscopy aided by first principles calculations including the electronic structure and structural reconstruction of the QDs. Special attention was devoted to study the impact of the surface charge state on the excited state relaxation and effect of its passivation by Zn(2+) ion alloying. Two different blinking mechanisms related to defect-assisted charge imbalance in the QD responsible for fast non-radiative relaxation of the excited states as well as surface recharging of the QD were found as the major causes of deviations from the first-order decay law. Careful optimization of the AgInS2 QDs would help to fabricate new red-shifted and tunable fluorescent bio-probes characterized by low-toxicity, high quantum yield, long luminescence lifetime, and time stability, leading to many novel in vitro and in vivo applications based on fluorescence lifetime imaging (FLIM) and time-gated detection.

Atypical femoral neck stress fracture in a marathon runner: a case report and literature review.

BACKGROUND: Femoral neck stress fractures are relatively rare and may present as sports-related injuries. The presentation is variable, and prompt diagnosis facilitates the earliest return to pre-morbid functional activity levels. Delayed detection may precipitate femoral non-union or avascular necrosis, resulting in long-term functional deficit. AIMS: We present the case of a basicervical femoral neck stress fracture occurring in a 23-year-old marathon runner. The pathophysiology and practical management issues related to this unusual injury pattern are discussed. CONCLUSION: The growing interest in amateur athletic activities should raise the index of suspicion for stress fractures of the femoral neck in healthy adults with atypical hip pain. Increased levels of patient education and physician awareness can reduce the incidence of long-term morbidity in cases of this unusual sports-related injury.

Pathogenic and carcinogenic properties of silicon carbide.

The article presents the influence of silicon carbide upon an organism, on the basis of the publications which, according to Chemical Abstracts, appeared on this subject from 1944 until 1987. The insolubility of silicon carbide, in the liquids of an organism and its indigestibility are indicated. A connection is presented between the size and shape of micrograins and the probability of tumor formation in rats; and the difference between silicon carbide and other dusts in the absorption of x-rays, inhibition of the TTC-dehydrogenase activity, collagenisation of lesions, carcinogenicity are also presented. The problem of interpretation of radiological images of lungs in people exposed to the influence of carborundum dust is dealt with. The biological inertness of silicon carbide is questioned.