Lentotuhkan fraktiointi sähkösuodattimella ja Ion Blast -menetelmällä

Diplomityö on osa YTI-tutkimuskeskuksessa vuosina 2002 - 2004 toteutettavaa Jätekompostit rakeiksi tuhkaseostuksella -käyttöarvon parantaminen -projektia. Työssä tutkittiin Etelä-Savon Energia Oy:n Pursialan voimalaitoksen lentotuhkan fraktioimista voimalaitoksen nykyisellä 3-kenttäisellä sähkösuodattimella ja pilot-mittakaavaisella Ion Blast -koelaitteistolla. Sähkösuodattimen koeajojen aikana muuteltiin sen ajotapaa mm. CBO -suhteen ja maksimijänniteasetuksen avulla. Ion Blast -koelaitteistolla tutkittiin mahdollisuuksia voimalaitoksen lentotuhkan puhdistamiseksi raskasmetalleista. Lentotuhkan hyötykäyttöä vaikeuttaa sen raskasmetallipitoisuuksien suuri vaihtelu. Ongelmallisin raskasmetalli puuperäisessä lentotuhkassa on kadmium, jonka lannoitelainsäädännön raja-arvo on tällä hetkellä 3 mg/kg. Sähkösuodattimella tehtyjen fraktiointikokeiden perusteella voidaan todeta raskasmetallipitoisuuksien olevan pienimmillään sähkösuodattimen 1-kentässä ja suurimmillaan 3-kentässä. Tämä johtuu siitä, että 1-kenttään kerääntyy hiukkaskooltaan suurimmat lentotuhkahiukkaset ja 3-kentässä on mukana enemmän pienhiukkasia sisältävää tuhkaa. Lannoitteeksi menevän tuhkan Cd-pitoisuutta voidaan vähentää parhaimmillaan jopa 70 % sähkösuodattimella fraktioimalla. Muiden raskasmetallien pitoisuudet eivät vähene aivan yhtä paljon. Sähkösuodattimella voidaan tulosten perusteella fraktioida lentotuhkaa. Sähkösuodattimella ei kuitenkaan voida varmasti saavuttaa alle 3 mg/kg Cd-pitoisuuksia polttoaineen laadunvaihtelun vuoksi. Ion Blast -koelaitteiston tulokset tukevat sähkösuodattimella tehtyjä kokeita. Erottimen jännitteen kasvaessa raskasmetalleja sisältävien hiukkasten erotusaste kasvaa. Ion Blast -laitteistolla tehdyissä kokeissa myös Cd-pitoisuus oli korkeimmillaan pienimmän raeluokan hiukkasissa ja laski sitten raeluokan suurentuessa. Ion Blast -laitteisto ei kuitenkaan sellaisenaan ole hyvä fraktiointiin. Se on liian tehokas, jolloin se puhdistaa tehokkaasti myös raskasmetalleja sisältävät pienhiukkaset. Jos laitetta aiotaan käyttää fraktiointiin, tulisi sen rakennetta muuttaa.

From Full stopping to transparency in a holographic model of heavy ion collisions

We numerically simulate planar shock wave collisions in anti-de Sitter space as a model for heavy ion collisions of large nuclei. We uncover a crossover between two different dynamical regimes as a function of the collision energy. At low energies the shocks first stop and then explode in a manner approximately described by hydrodynamics, in close similarity with the Landau model. At high energies the receding fragments move outwards at the speed of light, with a region of negative energy density and negative longitudinal pressure trailing behind them. The rapidity distribution of the energy density at late times around midrapidity is not approximately boost invariant but Gaussian, albeit with a width that increases with the collision energy.

Use of the dried blood spot sampling process coupled with fast gas chromatography and negative-ion chemical ionization tandem mass spectrometry: application to fluoxetine, norfluoxetine, reboxetine, and paroxetine analysis.

The objective of this work was to combine the advantages of the dried blood spot (DBS) sampling process with the highly sensitive and selective negative-ion chemical ionization tandem mass spectrometry (NICI-MS-MS) to analyze for recent antidepressants including fluoxetine, norfluoxetine, reboxetine, and paroxetine from micro whole blood samples (i.e., 10 microL). Before analysis, DBS samples were punched out, and antidepressants were simultaneously extracted and derivatized in a single step by use of pentafluoropropionic acid anhydride and 0.02% triethylamine in butyl chloride for 30 min at 60 degrees C under ultrasonication. Derivatives were then separated on a gas chromatograph coupled with a triple-quadrupole mass spectrometer operating in negative selected reaction monitoring mode for a total run time of 5 min. To establish the validity of the method, trueness, precision, and selectivity were determined on the basis of the guidelines of the "Société Française des Sciences et des Techniques Pharmaceutiques" (SFSTP). The assay was found to be linear in the concentration ranges 1 to 500 ng mL(-1) for fluoxetine and norfluoxetine and 20 to 500 ng mL(-1) for reboxetine and paroxetine. Despite the small sampling volume, the limit of detection was estimated at 20 pg mL(-1) for all the analytes. The stability of DBS was also evaluated at -20 degrees C, 4 degrees C, 25 degrees C, and 40 degrees C for up to 30 days. Furthermore, the method was successfully applied to a pharmacokinetic investigation performed on a healthy volunteer after oral administration of a single 40-mg dose of fluoxetine. Thus, this validated DBS method combines an extractive-derivative single step with a fast and sensitive GC-NICI-MS-MS technique. Using microliter blood samples, this procedure offers a patient-friendly tool in many biomedical fields such as checking treatment adherence, therapeutic drug monitoring, toxicological analyses, or pharmacokinetic studies.

New method for measuring longitudinal fuctuations and directed flow in ultrarelativistic heavy ion reactions

It has been shown in recent ALICE@LHC measurements that the odd flow harmonics, in particular, a directed flow v1, occurred to be weak and dominated by random fluctuations. In this work we propose a new method, which makes the measurements more sensitive to the flow patterns showing global collective symmetries. We demonstrate how the longitudinal center of mass rapidity fluctuations can be identified, and then the collective flow analysis can be performed in the event-by-event center of mass frame. Such a method can be very effective in separating the flow patterns originating from random fluctuations, and the flow patterns originating from the global symmetry of the initial state.

Derivation of an observer model adapted to irregular signals based on convolution channels.

Anthropomorphic model observers are mathe- matical algorithms which are applied to images with the ultimate goal of predicting human signal detection and classification accuracy across varieties of backgrounds, image acquisitions and display conditions. A limitation of current channelized model observers is their inability to handle irregularly-shaped signals, which are common in clinical images, without a high number of directional channels. Here, we derive a new linear model observer based on convolution channels which we refer to as the "Filtered Channel observer" (FCO), as an extension of the channelized Hotelling observer (CHO) and the nonprewhitening with an eye filter (NPWE) observer. In analogy to the CHO, this linear model observer can take the form of a single template with an external noise term. To compare with human observers, we tested signals with irregular and asymmetrical shapes spanning the size of lesions down to those of microcalfications in 4-AFC breast tomosynthesis detection tasks, with three different contrasts for each case. Whereas humans uniformly outperformed conventional CHOs, the FCO observer outperformed humans for every signal with only one exception. Additive internal noise in the models allowed us to degrade model performance and match human performance. We could not match all the human performances with a model with a single internal noise component for all signal shape, size and contrast conditions. This suggests that either the internal noise might vary across signals or that the model cannot entirely capture the human detection strategy. However, the FCO model offers an efficient way to apprehend human observer performance for a non-symmetric signal.

Dynamic range extension of SiPM detectors with the time-gated operation

The silicon photomultiplier (SiPM) is a novel detector technology that has undergone a fast development in the last few years, owing to its single-photon resolution and ultra-fast response time. However, the typical high dark count rates of the sensor may prevent the detection of low intensity radiation fluxes. In this article, the time-gated operation with short active periods in the nanosecond range is proposed as a solution to reduce the number of cells fired due to noise and thus increase the dynamic range. The technique is aimed at application fields that function under a trigger command, such as gated fluorescence lifetime imaging microscopy.

Rapid analysis of multiclass antibiotic residues and some of their metabolites in hospital, urban wastewater and river water by ultra-highperformance liquid chromatography coupled to quadrupole-linear ion trap tandem mass spectrometry

The present work describes the development of a fast and robust analytical method for the determination of 53 antibiotic residues, covering various chemical groups and some of their metabolites, in environmental matrices that are considered important sources of antibiotic pollution, namely hospital and urban wastewaters, as well as in river waters. The method is based on automated off-line solid phase extraction (SPE) followed by ultra-high-performance liquid chromatography coupled to quadrupole linear ion trap tandem mass spectrometry (UHPLC–QqLIT). For unequivocal identification and confirmation, and in order to fulfill EU guidelines, two selected reaction monitoring (SRM) transitions per compound are monitored (the most intense one is used for quantification and the second one for confirmation). Quantification of target antibiotics is performed by the internal standard approach, using one isotopically labeled compound for each chemical group, in order to correct matrix effects. The main advantages of the method are automation and speed-up of sample preparation, by the reduction of extraction volumes for all matrices, the fast separation of a wide spectrum of antibiotics by using ultra-high-performance liquid chromatography, its sensitivity (limits of detection in the low ng/L range) and selectivity (due to the use of tandem mass spectrometry) The inclusion of β-lactam antibiotics (penicillins and cephalosporins), which are compounds difficult to analyze in multi-residue methods due to their instability in water matrices, and some antibiotics metabolites are other important benefits of the method developed. As part of the validation procedure, the method developed was applied to the analysis of antibiotics residues in hospital, urban influent and effluent wastewaters as well as in river water samples

Spectroscopic characterization of phases formed by high-dose carbon ion implantation in silicon

High-dose carbon-ion-implanted Si samples have been analyzed by infrared spectroscopy, Raman scattering, and x-ray photoelectron spectroscopy (XPS) correlated with transmission electron microscopy. Samples were implanted at room temperature and 500°C with doses between 1017 and 1018 C+/cm2. Some of the samples were implanted at room temperature with the surface covered by a capping oxide layer. Implanting at room temperature leads to the formation of a surface carbon-rich amorphous layer, in addition to the buried implanted layer. The dependence of this layer on the capping oxide suggests this layer to be determined by carbon migration toward the surface, rather than surface contamination. Implanting at 500°C, no carbon-rich surface layer is observed and the SiC buried layer is formed by crystalline ßSiC precipitates aligned with the Si matrix. The concentration of SiC in this region as measured by XPS is higher than for the room-temperature implantation.

Ion-selective electrodes: historical, mechanism of response, selectivity and concept review

This paper presents a review of the concepts involved in the working mechanism of the ion-selective electrodes, searching a historical overview, moreover to describe the new advances in the area.

Gas-phase ion chemistry of silyl cations obtained from hexamethyldisilazane

The gas-phase ion-molecule reactions of the Me3SiN(H)SiMe2+ ion, obtained by electron ionization from Me3SiN(H)SiMe3, have been studied in a Fourier transform ion cyclotron resonance spectrometer in order to understand the mechanistic details of an important chemical system presently used in film formation. This silyl cation has been observed to undergo addition reactions at electron rich centers to form stable adducts that may undergo further methane elimination in the case of alcohols and amines. The most important feature of these reactions is the fact that a metathesis type reaction can be observed in the presence of H2O, and other hydrogen labile substrates like alcohols, leading to the formation of the corresponding oxygen-containing ion, i.e. Me3SiOSiMe2+. For alcohols (ROH), facile formation of a tertiary product ion, presumably corresponding to an Me3Si-O-Si(Me)=O+-R structure with elimination of an amine reveals the strong tendency of these nitrogen-containing ions to undergo metathesis type reactions with oxygen containing substrates.

Síntese eletroquímica do ion ferrato(VI)

The optimization of ferrate(VI) ion generation has been studied due to its favorable characteristics for application in several fields, including environmental quality control. The paper presents the best conditions for electrolytic generation of ferrate(VI) in alkaline media. An appropriate electrolyte was NaOH, 10 mol/L. Circulation of the electrolyte solution was important to avoid acidification close to the anode surface. An anode pre-cleaning with 10% HCl was more efficient than a cathodic pre-polarization. Among the distinct anode materials tested, pig iron showed the best performance, allowing up to 20 g/L of Na2FeO4, in 10 mol/L NaOH solution to be obtained, after 7 h of reactor operation, which is a concentration higher than those found in literature for alternative processes.

Development and validation of an alternative titration method for the determination of sulfate ion in indinavir sulfate

A simple and rapid precipitation titration method was developed and validated to determine sulfate ion content in indinavir sulfate raw material. 0.1 mol L-1 lead nitrate volumetric solution was used as titrant employing potentiometric endpoint determination using a lead-specific electrode. The United States Pharmacopoeia Forum indicates a potentiometric method for sulfate ion quantitation using 0.1 mol L-1 lead perchlorate as titrant. Both methods were validated concerning linearity, precision and accuracy, yielding good results. The sulfate ion content found by the two validated methods was compared by the statistical t-student test, indicating that there was no statistically significant difference between the methods.