Electrometric investigations on the formation of cerium(III) tungstates as a function of PH

The course of reaction between cerium(III) nitrate and different sodium tungstates (Na2WO4, Na10W12O41 and Na6W12O39) has been followed by means of pH and conductometric titrations between the reactants at different pH levels, in aqueous and alcoholic media, with each of the reagents alternatively used as titrant. The electrometric experiments provide definite evidence of the formation of normal-Ce2O3.3WO3 and para- 5Ce2O3.36WO3 tungstates of cerium in the vicinity of pH 6.2 and 5.3. The formation of normal tungstate is almost quantitative and the pH titrations offer a simple means for determination of cerium(III) or tungstate solutions at suitable concentrations and pH range.

Yhdessä ja liikkeellä. Mobiili sosiaalinen media

Sosiaalinen media viittaa verkkopalveluihin, joiden toiminta perustuu käyttäjien ja käyttäjäyhteisöjen aktiiviseen sosiaaliseen vuorovaikutukseen. Matkapuhelimien kautta sosiaalinen media on liikkeellä ja pitää käyttäjät yhdessä ajasta ja paikasta riippumatta. Sosiaalisen median vetovoima perustuu siihen, että ihmiset jakavat tietoja, kuvia, videota ja ääntä sekä kommentoivat ja jatkavat viestiketjuja. Yhdessä ja liikkeellä -kirja tarkastelee sosiaalisen median uusinta ilmiötä, videoiden jakamista kännykkäpalvelun kautta. Mobiilit videot voivat kertoa jaetuista elämyksistä, konserteista, benji-hypyistä tai jazz-festivaalin vessajonosta. Liikkuva kuva kertoo usein enemmän kuin useampi valokuva, ja monen käyttäjän videokuva samasta tapahtumasta voi jo kertoa monipolvisen tarinan. Yhdessä ja liikkeellä esittelee Mobile Social Media -tutkimushankkeen tuloksia. Tavoitteena on ollut tutkia, millaiset tekijät tukevat mobiilin sosiaalisen median käyttöä ja miten sosiaalista mediaa hyödynnetään matkapuhelimilla, miten sosiaalisen median yhteisö voi muodostaa kännykkävideoista yhteisen tarinan, millaisia teknologisia haasteita mobiilin sosiaalisen median käytölle on. Tutkimushanke on CAT - Culture Art and Technology -verkoston yhteistyötä. Verkostoon kuuluvat Aalto-yliopiston, Tampereen teknillisen yliopiston ja Turun yliopiston Porin yksiköt.

About the kinetics and mechanism of the reactions of 4-(2-pyridylazo)-resorcinol, with Zn2+, Cu2+ and Zn2++Cu2+ equimolar mixtures, in aqueous solutions

The kinetics and mechanism of the reactions between 4(2pyridylazo)-resorcinol and Zn2+, Cu2+ and Zn2++Cu2+ equimolar mixtures were studied. The reactions were performed in aqueous solution (pH = 8.5, borate buffer) and monitored spectrophotometrically at 500 nm using stopped-flow technique. Spectral and kinetic data indicate that the Zn2++Cu2+ equimolar mixture behaves as an unique species and it can be attributed to the interactions of Zn2+ and of Cu2+ with water molecules in the aqueous solution. A mechanism is proposed and the rate constants are calculated.

Preparation and electrochemical characterization of Pt nanoparticles dispersed on niobium oxide

Electrodes consisting of Pt nanoparticles dispersed on thin films of niobium oxide were prepared onto titanium substrates by a sol-gel method. The physical characterization of these electrodes was carried out by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The mean size of the Pt particles was found to be 10.7 nm. The general aspects of the electrochemical behavior were studied by cyclic voltammetry in 1 mol L-1 HClO4 aqueous solution. The response of these electrodes in relation to the oxidation of formaldehyde and methanol in acidic media was also studied.

Utilizing social media in software documentation and knowledge management

This Master’s thesis studies the possibilities that social media tools can bring to help knowledge management in software development companies. It will introduce the most popular tools of social media and their usage possibilities in companies, not forgetting the possible downsides. One relevant aspect in this study is to investigate the possibilities of social media to help converting existing tacit knowledge into explicit. The purpose of the work is to create a proposal of social media utilization for a mid-sized software company, which has not utilized social media tools before. To be able to create the proposal, employees of the company are interviewed and a survey is executed to analyze the current situation. In addition a pilot project for trying out new social media tools is executed. The final result of this thesis introduces a tailored solution for the target company to start utilizing social media in its documentation and knowledge sharing processes. This new solution consists of multiple individual suggestions that are categorized and prioritized based on the significance and benefit that they bring to the company.

Sorption kinetics and intrapaticulate diffusivity of As(III) bioremediation from aqueous solution, using modified and unmodified coconut fiber

The pollution and toxicity problems posed by arsenic in the environment have long been established. Hence, the removal and recovery remedies have been sought, bearing in mind the efficiency, cost effectiveness and environmental friendliness of the methods employed. The sorption kinetics and intraparticulate diffusivity of As (III) bioremediation from aqueous solution using modified and unmodified coconut fiber was investigated. The amount adsorbed increased as time increased, reaching equilibrium at about 60 minutes. The kinetic studies showed that the sorption rates could be described by both pseudo-first order and pseudo-second order process with the later showing a better fit with a value of rate constant of 1.16 x 10-4 min-1 for the three adsorbent types. The mechanism of sorption was found to be particle diffusion controlled. The diffusion and boundary layer effects were also investigation. Therefore, the results show that coconut fiber, both modified and unmodified is an efficient sorbent for the removal of As (III) from industrial effluents with particle diffusion as the predominant mechanism.

Immersion enthalpy variation of surface-modified mineral activated carbon in lead (II) aqueous solution adsorption: the relation between immersion enthalpy and adsorption capacity

An activated carbon was obtained by chemical activation with phosphoric acid, CM, from a mineral carbon. Afterwards, the carbon was modified with 2 and 5 molL-1, CMox2 and CMox5 nitric acid solutions to increase the surface acid group contents. Immersion enthalpy at pH 4 values and Pb2+ adsorption isotherms were determined by immersing activated carbons in aqueous solution. The surface area values of the adsorbents and total pore volume were approximately 560 m².g-1 and 0.36 cm³g-1, respectively. As regards chemical characteristics, activated carbons had higher acid sites content, 0.92-2.42 meq g-1, than basic sites, 0.63-0.12 meq g-1. pH values were between 7.4 and 4.5 at the point of zero charge, pH PZC. The adsorbed quantity of Pb2+ and the immersion enthalpy in solution of different pH values for CM activated carbon showed that the values are the highest for pH 4, 15.7 mgg-1 and 27.6 Jg-1 respectively. Pb2+ adsorption isotherms and immersion enthalpy were determined for modified activated carbons and the highest values were obtained for the activated carbon that showed the highest content of total acid sites on the surface.

Adsorption isotherm studies of Cd (II), Pb (II) and Zn (II) ions bioremediation from aqueous solution using unmodified and EDTA-modified maize cob

The need to clean-up heavy metal contaminated environment can not be over emphasized. This paper describes the adsorption isotherm studies of Cd (II), Pb (II) and Zn (II) ions from aqueous solution using unmodified and EDTA-modified maize cob. Maize cob was found to be an excellent adsorbent for the removal of these metal ions. The amount of metal ions adsorbed increased as the initial concentration increased. Also, EDTA - modification enhanced the adsorption capacity of maize cob probably due to the chelating ability of EDTA. Among the three adsorption isotherm tested, Dubinin-Radushkevich gave the best fit with R² value ranging from 0.9539 to 0.9973 and an average value of 0.9819. This is followed by Freundlich isotherm (Ave. 0.9783) and then the Langmuir isotherm (Ave. 0.7637). The sorption process was found to be a physiosorption process as seen from the apparent energy of adsorption which ranged from 2.05KJ\mol to 4.56KJ\mol. Therefore, this study demonstrates that maize cob which is an environmental pollutant could be used to adsorb heavy metals and achieve cleanliness thereby abating environmental nuisance caused by the maize cob.

Potentiometric and conductometric studies on the system acid-isopolytungstate and the formation of lanthanum tungstates

The stoichiometry of the polyanions formed by the action of nitric acid on sodium tungstate (< 0.01M) has been studied by means of electrometric techniques involving pH-potentiometric and conductometric titrations. The well defined inflections and breaks in the titration curves provide evidence for the existence of the polyanions, para-W12O41(10-) and meta-W12O39(6-) corresponding to the ratio of H+:WO4(2-) as 7:6 and 9:6 in the pH ranges 5.7-6.0 and 3.6-4.1, respectively. The interaction of lanthanum nitrate with sodium tungstate solutions, at specific pH levels 8.0, 5.9 and 4.0 was also studied by pH and conductometric titrations, in aqueous and alcoholic media, with each of the reagents alternatively used as titrant. The electrometric experiments provide definite evidence of the formation of normal-La2O3.3WO3, para-5La2O3.36WO3 and meta-La2O3.12WO3 tungstates in the vicinity of pH 6.3, 5.0 and 4.2, respectively. Analytical investigations on the precipitates formed confirm the results of the electrometric study.

A fluorescence probe study of gemini surfactants in aqueous solution: a comparison between n-2-n and n-6-n series of the alkanediyl-a,w-bis (dimethylalkylammonium bromides)

Two series of alkanediyl-a,w-bis (dimethylalkylammonium bromide (n-2-n and n-6-n; n=8, 10,12, and 16) have been synthesized and their micelles properties studied in aqueous solution using pyrene, pyrenecarboxaldehyde (PCA) and 1,8 anilinonaphtalene sulfonic acid sodium salt (ANS) as fluorescent probes. The micelles from these surfactants have been characterized on the basis of the information provided by micelle-solubilized fluorescent probes. The obtained results indicated that the surfactant concentration at which a marked decrease in l max parameter of pyrenecarboxaldehyde (PCA) occurs corresponds to the CMC determined by conductimetric measurements. Changes in the emission spectra of ANS and PCA observed in the submicellar range for both surfactants series (n-2-n and n-6-n) were interpreted as formation of pre-aggregates. It was found that the dimeric surfactants with long spacer (s= 6) form more hydrated aggregates when compared with those formed by the n-2-n and CnTAB surfactants series. This was attributed to a more difficult packing of n-6-n surfactant molecules to form micelles.

Potentiometric and conductimetric studies of chemical equilibria for pyridoxine hydrochloride in aqueous solutions: simple experimental determination of pKa values and analytical applications to pharmaceutical analysis

The combination of two low-cost classical procedures based on titrimetric techniques is presented for the determination of pyridoxine hydrochloride in pharmaceuticals samples. Initially some experiments were carried out aiming to determine both pKa1 and pKa2 values, being those compared to values of literature and theoretical procedures. Commercial samples containing pyridoxine hydrochloride were electrochemically analysed by exploiting their acid-base and precipitation reactions. Potentiometric titrations accomplished the reaction between the ionizable hydrogens present in pyridoxine hydrochloride, being NaOH used as titrant; while the conductimetric method was based on the chemical precipitation between the chloride of pyridoxine hydrochloride molecule and Ag+ ions from de silver nitrate, changing the conductivity of the solution. Both methods were applied to the same commercial samples leading to concordant results when compared by statistical tests (95 and 98% confidence levels). Recoveries ranging from 99.0 to 108.1% were observed, showing no significant interference on the results.

Adsorptive removal of harmful organic compound from aqueous solutions

Adsorption is one of the most commonly used methods in water treatment processes. It is attractive due to it easy operation and the availability of a wide variety of commercial adsorbents. This doctoral thesis focuses on investigating and explaining the influence of external phase conditions (temperature, pH, ionic strength, acidity, presence of cosolutes) on adsorption phenomena. In order to cover a wide range of factors and phenomena, case studies were chosen from various fields where adsorption is applied. These include the adsorptive removal of surface active agents (used in cleaning chemicals, for example) from aqueous effluents, the removal of hormones (estradiol) from drinking water, and the adsorption of antibiotics onto silica. The latter can beused to predict the diffusion of antibiotics in the aquatic system if they are released into the environment. Also the adsorption of living cells on functionalized polymers to purify infected water streams was studied. In addition to these examples, the adsorptive separation of harmful compounds from internal water streams within a chemical process was investigated. The model system was removal of fermentation inhibitors from lignocelluloses hydrolyzates. The detoxification of the fermentation broth is an important step in the manufacture of bioethanol from wood, but has not been studied previously in connection with concentrated acid hydrolyzates. New knowledge on adsorption phenomena was generated for all of the applications investigated. In most cases, the results could be explained by combining classical theories for individual phenomena. As an example, it was demonstrated how liquid phase aggregation could explain abnormal-looking adsorption equilibrium data. In addition to the fundamental phenomena, also process performance was of interest. This aspect is often neglected in adsorption studies. It was demonstrated that adsorbents should not be selected for a target application based on their adsorption properties only, but regeneration of the spent adsorbent must be considered. It was found that using a suitable amount of organic co-solvent in the regeneration can significantly improve the productivity of the process.

Seriedebatt i 1950-talets Finland : en studie i barndom, media och reglering

I avhandlingen granskas den debatt som fördes om seriemediet och serieläsandet i Finland från början av 1950-talet till början av 1960-talet. Serietidningen var då ett nytt medium och föranledde en oro beträffande barns läsvanor. ”Seriefrågan” diskuterades i pressen och problematiken engagerade barnskyddsorganisationer och forskare, behandlades i riksdagen och undersöktes av en statlig kommitté. De olika debattuttrycken analyseras i studien. Avhandlingens teoretiska perspektiv är styrningsanalytiskt och bygger på diskussionen om regementalitet (governmentality). I studien granskas hur seriemediet, barndom och regleringen av dessa kom att definieras i behandlingen av det s.k. serieproblemet. Serierna definierades som ett problematiskt medium på ett flertal sätt. De huvudsakliga argumenten mot serierna var dels att de förstörde barns läsförmåga, dels att de budskap som serierna förmedlade till barnen var av fel slag. Enligt kritiken var serierna språkligt fattiga och innehållsmässigt alltför våldsamma. Följaktligen utgjorde serierna ett hot mot barnen. Barnen kom ur detta perspektiv att definieras som inkompetenta medieanvändare och i behov av skydd. I debatten upplyftes olika sätt att lösa och reglera problemet. Man undersökte problematiken och upplyste allmänheten om den, man försökte påverka serieutgivarna och man påkallade censur. Seriedebatten och den verksamhet som debattörerna ägnade sig åt ledde dock inte till synbara resultat, t.ex. ny lagstiftning eller förändringar i seriemarknaden. Ändå dog debatten i början av 1960-talet. Problemet med de serieläsande barnen hanterades m.a.o. genom själva debatten. Samtidigt uteblev mera drastiska former av reglering. Ett övergripande syfte för analysen av den kunskap som skapades i debatten – dess varierande förståelse av seriemedium, barndom och reglering – är att erbjuda infallsvinklar till aktuella diskussioner om och farhågor angående barns mediebruk. Med fokus på bredden hos debattens uttryck och de diskursiva ramarna för problematiseringen av barns serieläsande ger avhandlingen perspektiv på den med jämna mellanrum uppdykande frågeställningen om barns mediebruk.