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Voltammetric methods based on the application of simple and contemporary carbonaceousmaterials-based electrodes/sensors for the determination of hydrogen-peroxide in the selected samples
No full textCilj ove doktorske disertacije je bio razvoj brzih i pouzdanih voltametrijskih metoda zasnovanih na primeni jednostavnih i savremenih elektroda/senzora na bazi ugljeničnih materijala (ugljenične paste napravljene od grafitnog praha i parafinskog ulja i štampanih ugljeničnih elektroda) za određivanje H 2O2 u odabranim složenim model i realnim uzorcima. U tu svrhu, ispitana je primenljivost različitih radnih elektroda. Amperometrijska metoda zasnovana na elektrodi od ugljenične paste (CPE) zapreminski modifikovane sa 5% (m:m) MnO2 je, pri optimizovanim uslovima i pri radnom potencijalu od 0,40 V u odnosu na zasićenu kalomelovu elektrodu (ZKE) u fosfatnom puferu pH 7,50 kao pomoćnom elektrolitu, omogućila kvantifikaciju H 2O2 u opsegu koncentracija od 1,4 do 65 µg mL -1 sa relativnom standardnom devijacijom (RSD) manjom od 10%. Ova metoda je primenjena za određivanje sadržaja H 2O2 u uzorcima podzemne vode iz centralnog Banata (Pokrajina Vojvodina, Srbija) tretirane Fentonovim (Fe 2+ i H 2O2 ) i Fentonu-sličnim (Fe 3+ i H 2O2 ) reagensima u cilju uklanjanja prirodnih organskih materija (POM) pri čemu su korišćene različite početne koncentracije gvožđa i različiti odnosi molarnih koncentracija gvožđa i H 2O2 . Utvrđeno je da oksidaciono stanje gvožđe (Fe 2+ ili Fe 3+) i molarni odnos jona Fe i H 2O2 utiču na stepen potrošnje/razgradnje H 2O2 u podzemnoj vodi sa visokim sadržajem POM. Takođe, u slučaju Fentonu-sličnog procesa, za sve početne koncentracije Fe 3+ i H 2O2 , signifikantna količina H 2O2 ostaje neiskorišćena, što ukazuje na nižu efikasnost ovakvog sistema u poređenju sa Fentonovim procesom.Štampana ugljenična elektroda (SPCE) zapreminski modifikovana sa MnO 2 kao medijatorom je primenjena za određivanje sadržaja H 2O2 u toku Fentonovog (Fe 2+ , H2O2 ) i vidljivom svetlošću potpomognutog foto-Fentonovog (Fe 2+ , H 2O2 , hν) procesa uklanjanja neonikotinoidnog insekticida acetamiprida (ACT). Pri optimizovanim uslovima (radni potencijal 0,40 V u odnosu na ZKE, fosfatni pufer pH 7,50 kao pomoćni elektrolit) amperometrijskog određivanja H 2O2 , postignuta je linearnost u opsegu koncentracija 0,01–1,24 mmol L-1(0,34– 42,2 µg mL -1 ) i vrednost RSD nije prelazila 4,2%. U ispitivanimuzorcima (nakon odgovarajućeg podešavanja pH vrednosti od 2,8 do 7,5 odmah nakon uzorkovanja radi stopiranja ili maksimalnog usporavanja procesa oksidacije, filtriranja, zamrzavanja i odmrzavanja neposredno pre merenja) sadržaj H 2O2 je određen metodom standardnog dodatka analiziranjem odgovarajućih amperometrijskih krivi. Paralelna HPLC-DAD merenja su vršena u cilju praćenja koncentracije/uklanjanja ACT. U slučaju foto-Fentonovog procesa (početne koncentracije 0,31; 2,0 i 3,0 mmol L -1 (70,0; 111,7 i 102,1 µg mL -1 ) za ACT, Fe 2+ i H 2O2, redom) nakon 10 min H 2O2 je izreagovao, a može se smatrati da je ACT uklonjen nakon 5 min. U toku Fentonovog procesa ACT je uklonjen nakon 20 min tretmana i oko 10% početne koncentracije H 2O2 je ostalo u sistemu neiskorišćeno.CPE je površinski modifikovane kompozitom na bazi nanočestica Pt (< 5 nm) i grafitizovanog ugljenika (Pt-C, 10% Pt na Vulkanu XC72) etodom nanošenja kapi. Nemodifikovana CPE i modifikovana (Pt-C/CPE) su okarakterisane primenom SEM/EDS i CV merenja. Pt-C/CPE je pokazala izuzetne elektrokatalitičke osobine u pogledu elektrohemijskeredoks reakcije H 2O2 u poređenju sa nemodifikovanom CPE u fosfatnom puferu (0,1 mol L -1 ; pH 7,50), a takođe i u acetatnom puferu (0,1 mol L -1 ; pH 4,50) kao pomoćnim elektrolitima. Prilikom amperometrijskog određivanja H 2O2 primenom Pt-C/CPE u model sistemima, zadovoljavajuća linearnost je postignuta u koncentracionom opseguH2O2od 0,15 do 1,45 µg mL -1 ,dok su vrednosti GO iznosile 0,06 µg mL -1 (pH 7,50, radni potencijal 0,20 V) i 0,10 µg mL -1 (pH 4,50, radni potencijal 0,50 V). Optimizovane analitičke metode su primenjene za određivanje sadržaja H 2O2 u komercijalno dostupnim proizvodima za ličnu negu: rastvoru za dezinfekciju (pH 7,50) i rastvoru za čišćenje kontaktnih sočiva (pH 4,50). Amperometrijski dobijeni rezultati su u dobrom slaganju sa rezultatima dobijenim primenom tradicionalne spektrofotometrijske metode bazirane na titanijum-sulfatu kao reagensu sa određenim koncentracijama 2,91% i 2,94% za dezinfekcioni rastvor i 3,04% i 3,17% za rastvor zakontaktna sočiva, redom. RSD je bila manja od 2%. Postignuti rezultati su u dobrom slaganju sa sadržajem H 2O2 deklarisanim od strane proizvođača (3%) u oba ispitivana uzorka. Pt-C/CPE je takođe testirana za praćenje koncentracije H2O2 u rastvoru za kontaktna sočiva u toku procesa njegove neutralizacije/razgradnje. Nakon 6 h procesa neutralizacije, 24,68 µg mL -1 je bila određena koncentracija H 2O2 , što je ispod dozvoljene H2O2 koncentracije u rastvoru za kontaktna sočiva imajući u vidu granicu koja izaziva iritaciju oka. CPE je površinski modifikovana višezidnim ugljeničnim nanocevima (MWCNT) i kompozitima MnO 2 -MWCNT ili Pt-MWCNT metodom nanošenja kapi radi pripreme jednostavnih, osetljivih i pouzdanih voltametrijskih senzora za određivanje H 2O2 u odabranom uzorku. Rezultati SEM/EDS analize kompozitnih materijala su potvrdili da su medijatori, čestice MnO 2 i Pt, nasumično raspoređeni na površini MWCNT i zastupljeni sa blizu 5% (m:m) u kompozitu izraženo preko Mn i Pt. CV merenja su vršena sa pripremljenim radnim elektrodama u acetatnom (pH 4,50), fosfatnom (pH 7,50) i boratnom (pH 9,18) puferu kako bi se okarakterisalo osnovno elektrohemijsko ponašanje H 2O2 i odabrali pogodni radni potencijali za amperometrijsko određivanje ovog ciljnog analita. Pt- WCNT/CPE je primenljiva za rad kako u fosfatnom puferu pH 7,50 tako i u acetatnom puferu pH 4,50 V kako pri negativnim tako i pri pozitivnim radnim potencijalima, pri čemu su vrednosti RSD uglavnom ispod 2,5%. U slučaju MnO 2 -MWCNT/CPE, na potencijalu 0,30 V i višim vrednostima, oksidacioni signali H 2O2 su signifikantni u blago alkalnoj sredini (pH 7,50), pri pH 4,50 ova elektroda pokazuje nezadovoljavajuće ponašanje, dok pri pH 9,18 ima prihvatljive performanse. Granice određivanja (GO) su bile u oblasti µg mL -1 . H 2O2 je određen u spajkovanom uzorku mleka metodom standardnog dodatka nakon odgovarajuće pripreme uzorka (pH podešavanje i centrifugiranje) i primenom optimizovane amperometrijske procedure (acetatni pufer pH 4,50, radni potencijal-0,75 V) koristeći Pt-MWCNT/CPE kao radnu elektrodu. RSD za tri ponovljena merenja je iznosila 2,5%, dok je prinos metode bio nešto veći od 71%. Kompozitni materijali koji se sastoje od MWCNT i čestica na bazi Pd (Pd-MWCNT) ili Pt (Pt-MWCNT) su primenjeni za pripremu zapreminski modifikovanih SPCE (Pd-MWCNT-SPCE i Pt-MWCNT-SPCE) i površinski modifikovane SPCE (Pd-MWCNT/SPCE). Ove elektrode, kao i nemodifikovana SPCE i MWCNT-SPCE, su okarakterisane primenom CV i amperometrije u fosfatnom puferu pH 7,50 radi određivanja H 2O2 . Pd-MWCNT-SPCE i Pd-MWCNT/SPCE su se pokazale pogodnim za određivanje H 2O2 na radnim potencijalima između -0,50 i 0,50 V, a PtMWCNT-SPCE na ispitivanim radnim potencijalima od -0,80 do 0,70 V. Ove elektrode su zatim modifikovane enzimom glukoza oksidazom (GOx) metodom nanošenja kapi rastvora GOx i Nafion ® -a na njihovu površinu, pri čemu je optimizovana količina nanetog biofilma. GOx/PdMWCNT-SPCE je pokazala bolje analitičke performanse za određivanje glukoze u poređenju sa GOx/Pd- WCNT/SPCE. Kao optimalan radni potencijal GOx/Pd-MWCNT-SPCE je odabrana vrednost potencijala -0,40 V u odnosu na ZKE, sa zadovoljavajućom linearnošću u ispitivanom opsegu koncentracija glukoze od 0,16 do 0,97 mmol L -1 (od 29,1 do 174 µg mL -1), dok je GO iznosila 0,14 mmol L -1 (25 µg mL -1 ). Optimizovana metoda zasnovana na GOx/Pd-MWCNT-SPCE je uspešno primenjena za određivanje glukoze u uzorku livadskog meda. Dobijeni rezultati su u dobroj saglasnosti sa onima dobijenim primenom komercijalno dostupnog aparata za merenje glukoze. Pogodan radni potencijal za GOx/Pt-MWCNT-SPCE je bio -0,50 V u odnosu na ZKE, pri čemu je zadovoljavajuća linearnost postignuta u ispitivanom opsegu koncentracija glukoze od 65,8 do 260,6 µg mL -1 , sa GO 35 µg mL -1 . Optimizovana metoda zasnovana na GOx/Pt-MWCNT-SPCE je uspešno primenjena za određivanje glukoze u u uzorku belog grožđa i uzorku tableta (Traubenzucker-bonbons), pri čemu su dobijeni rezultati u dobroj saglasnosti sa rezultatima dobijenim primenom Accu-Chek aparata. Na osnovu dobijenih rezultata može se zaključiti da su razvijene analitičke metode pre svega jednostavne, pouzdane i pogodne za dobijanje brzih informacija o sadržaju H 2O2 u različitim tipovima uzoraka. Svakako odabir pogodne radne elektrode, kao i optimizacija eksperimentalnih uslova su ključni faktori za uspešno određivanje H 2O2The aim of this doctoral dissertation was the development of fast and reliable voltammetric methods based on the application of simple and contemporary electrodes/sensors based on carbonaceous materials (carbon paste made of graphite powder and paraffin oil and screen printed carbon electrodes) for the determination of H 2 O2 in the selected complex model and real samples.For this purpose, applicability of different working electrodes was investigated.The amperometric method based on carbon paste electrode (CPE) bulk- modified with 5% (m:m) MnO 2 , under optimized conditions, with a working potential of 0.40 V vs. the saturated calomel elect rode (SCE) and a phosphate buffer solution (pH 7.50) as supporting electrolyte, enabled the quantitation of H 2 O2in the concentration interval from 1.4 to 65 µg mL −1 with a relative standard deviation (RSD) of less than 10%. This meth od was applied for the determination of the H 2 O2 consumption in samples of groundwater fro m the Central Banat region (Province of Vojvodina, Serbia) treated by the Fenton (Fe 2+ and H 2O2 ) and Fenton- like (Fe 3+and H 2O2 ) reagents to remove natural organic matter (NOM) at differentinitial concentrations of iron species, and of their molar ratios to the initial concentration of H2O2 . It was found that the form of Fe (Fe 2+ or Fe 3+ )and the molar ratio to H 2O2influenced the degree of the H 2O2 decomposition in the groundwater with high NOM content. Besides, in the case of the Fenton-like process, for all initial doses of Fe 3+ and H 2 O2, a sign ificant amount of H 2 O2 remained unused, whi ch also indicates a lower efficiency of such system compared to the Fenton process. Screen printed carbon electrode (SPCE) bulk-modified with MnO 2 as a mediator was applied for amperometric determination of the H 2 O2 content during the Fenton (Fe 2+ , H 2 O2 ) and visible light-assisted , photo-Fenton (Fe 2+ , H 2 O2 , hν) based removal of neonicotinoid insecticide acetamiprid (ACT). Under optimized conditions (working potential of 0.40 V vs. SCE, phosphate buffer pH 7.50 as supporting electrolyte) amperometric determination of H 2 O2 showed a linear dynamic range from 0.01 to 1.24 mmol L -1 (from 0.34 to 42.2 µg mL -1) and the RSD did not exceed 4.2%. In the investigated samples (after appropriate pH adjustment from 2.8 to 7.5 instantly after the sampling to stop or maximum decelerate the oxidation processes, filtering, and storage of the deep- frozen sample with defrosting immediately before the measurements) the H 2 O2 contents were determined by the standard addition method by analyzing the corresponding amperometric curves. Parallel HPLC-DAD measurements were performed to monito r the concentration/removal of ACT. In the case of the photo- Fenton process (initial concentrations: 0.31; 2.0 and 3.0 mmol L -1 (70.0; 111.7 and 102.1 µg mL -1 ) of ACT, Fe 2+ and H 2 O2, respec tively) after 10 min of irradiation H 2 O2 was consumed and it can be consi dered that ACT was removed after 5 min. During the Fenton process ACT was removed after 20 min of treatment and around 10% of the initial concentration of the H 2O2 remained still unused. CPE was surface modified with a composite of Pt nanoparticles (< 5 nm) on graphitized carbon (Pt-C, 10% Pt on Vulcan XC72) by simply dropcoating method. The unmodified CPE and the modified one (Pt-C/CPE) were characterized by EM/EDS and CV measurements. The PtC/CPE showed remarkable electrocatalytic propertiestoward the electrochemical redox reaction of H 2 O2 compared to modified CPE in phosphate buffer (0.1 mol L -1 ; pH 7.50), as well in acetatebuffer (0.1 mol L -1 ; pH .50) supporting electrolytes. Amperometry of H2O2 in the concentration range from 0.15 to 1.45 µg mL -1 with the Pt-C/CPE showed acceptable linearity, while the obtained values of LOQs were 0.06 µg mL -1 (pH 7.50, working potential 0.20 V) and 0.10 µg mL -1 (pH 4 .50, working potential 0.50 V). The proposed analytical methods were applied to the determination of the H 2O2 content in commercially available personal care products; i.e., disinfection (pH 7.50) and contact lens cleaning solutions (pH 4.50). The obtained amperometric results are in good agreement with those measured by traditional titanium sulfatereagent based spectrophotometric method with determined concentrations as 2.91% and 2.94% for the disinfection product, and 3.04% and 3.17% for the contact lens solution, respectively. RSD was lower than 2%. The obtained results are in a good agreement with the amounts of the H 2 O2 declared by producers (3%) in the both investigated samples. The Pt-C/CPE was also tested for monitoring of the H 2 O2 residual concentration in contact lens solution during its neutralization/decomposition rocess. At 6 h of neutralization treatment 24.68 µg mL -1 of the H 2 O2 was determined which is almost half of the allowedH2 O2 concentration in the case of the contact lens solution concerningthe limit of eye irritation. CPE was surface modified with multiwalled carbon nanotubes (MWCNT) and with composites of MnO 2 -MWCNT or Pt-MWCNT by drop coating method to prepare simply, sensitive and reliable volta mmetric sensors for the determination of H 2 O2 in selected sample. The results of the SEM/ EDS analysis of composite materials have confirmed that the mediators, MnO 2 and Pt articles, are randomly distributed on the surface of MWCNT and represent nearly 5% (m:m) of the composite expressed as Mn and Pt. CV measurements were performed with prepared electrodes in acetate (pH 4.50), phosphate (pH 7.50) and borate (pH 9.18) buffers to characterize the basic electrochemical behavior of H 2 O2 and to select the working potentials suitable for amperometric determination of this target analyte. The Pt-MWCNT/CPE performs well in phosphate buffer pH .50 and acetate buffer solution pH 4.50 in the negative as well as in the positive polarization range with RSD mainly lower than 2.5%. In case of MnO 2 -MWCNT/CPE at 0.30 V and above the H 2 O2 oxidation signal is rem arkable in slightly alkaline media (pH 7.50), at pH 4.50 this electrode showed poor behavior and at pH 9.18 offered acceptable performance. LOQs were in the µg mL -1 concentration range. H 2 O2 was determined in a spiked milk sample by standard addition method after appropriate sample preparation (pH adjustment and centrifugation) and using optimized amperometric p rocedure (acetate buffer pH 4.50, working potential -0.75 V) by Pt-MWCNT/CPE as a working electrode. RSD for three repeated measurements was 2.5%, while the recovery of the method was a bit higher than 71%. The composite materials consisting of MWCNT and Pd (Pd-MWCNT) or Pt containing particles (Pt-WCNT) were applied to the preparation of bulk- modified SPCEs (Pd-MWCNTSPCE and Pt-MWCNT-SPCE) and surface modifiedSPCE (Pd- MWCNT/SPCE). These electrodes, as well as unmodified SPCE and MWCNT-SPCE, were characterized by CV and amperometry in phosphate buffer solution of pH 7.50 for the H 2 O2 determination. Pd-MWCNT-SPCE and PdMWCNT/SPCEare convenient for the etermination of H 2O2 at working potentials from -0.50 to 0.50 V, and Pt-MWCNT-SPCE at investigated working potentials in the range from -0.80 to 0.70 V. These electrodes were then modified with glucose oxidase (GOx) by drop coating a solution of GOxand Nafion ® on their surface, whereby the applied amount of biococktail was optimized. GOx/PdMWCNT-SPCE showed better analytical performance for glucose determination in comparison with GOx/Pd-MWCNT/SPCE. The optimal working potential for GOx/Pd-MWCNT- SPCE was -0.40 V vs. SCE and satisfactory linearity was obtained in the investigated glucose concentration range from 0.16 to 0.97 mmol L -1 (from 29.1 to 174 µg mL -1 ), hile the LOQ was 0.14 mmol L -1 (25 µg mL -1 ). The optimized method based on GOx/Pd-MWCNT-SPCE was successfully applied to the determination of glucose in multifloral honey sample. The results are in a good agreement with those obtained by commercially available equipment for determination of glucose. Optimal working potential for GOx/Pt-MWCNT-SPCE was -0.50 V vs. SCE, and the satisfactory linearity was obtained in the investigated concentration range ofglucose from 65.8 to 260.6 µg mL -1 , with LOQ of 35 µg mL -1 . The optimized method based on GOx/Pt- MWCNT-SPCE was successfully applied for determination of glucose in white grape and glucose tablets (Traubenzucker-bonbons) samples, whereby the obtained results were in a good agreement with the results obtained by Accu-Chek device. Based on the results, the developed analytical methods are first of all simple, reliable and suitable for obtaining fast information about the content of H 2O2 in different types of samples. Certainly the selection of a suitable working electrode, as well as the optimization of experimental conditions are key factors for the successful determination of H2O2
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Voltammetric methods based on the application of simple and contemporary carbonaceousmaterials-based electrodes/sensors for the determination of hydrogen-peroxide in the selected samples
No full textCilj ove doktorske disertacije je bio razvoj brzih i pouzdanih voltametrijskih metoda zasnovanih na primeni jednostavnih i savremenih elektroda/senzora na bazi ugljeničnih materijala (ugljenične paste napravljene od grafitnog praha i parafinskog ulja i štampanih ugljeničnih elektroda) za određivanje H 2O2 u odabranim složenim model i realnim uzorcima. U tu svrhu, ispitana je primenljivost različitih radnih elektroda. Amperometrijska metoda zasnovana na elektrodi od ugljenične paste (CPE) zapreminski modifikovane sa 5% (m:m) MnO2 je, pri optimizovanim uslovima i pri radnom potencijalu od 0,40 V u odnosu na zasićenu kalomelovu elektrodu (ZKE) u fosfatnom puferu pH 7,50 kao pomoćnom elektrolitu, omogućila kvantifikaciju H 2O2 u opsegu koncentracija od 1,4 do 65 µg mL -1 sa relativnom standardnom devijacijom (RSD) manjom od 10%. Ova metoda je primenjena za određivanje sadržaja H 2O2 u uzorcima podzemne vode iz centralnog Banata (Pokrajina Vojvodina, Srbija) tretirane Fentonovim (Fe 2+ i H 2O2 ) i Fentonu-sličnim (Fe 3+ i H 2O2 ) reagensima u cilju uklanjanja prirodnih organskih materija (POM) pri čemu su korišćene različite početne koncentracije gvožđa i različiti odnosi molarnih koncentracija gvožđa i H 2O2 . Utvrđeno je da oksidaciono stanje gvožđe (Fe 2+ ili Fe 3+) i molarni odnos jona Fe i H 2O2 utiču na stepen potrošnje/razgradnje H 2O2 u podzemnoj vodi sa visokim sadržajem POM. Takođe, u slučaju Fentonu-sličnog procesa, za sve početne koncentracije Fe 3+ i H 2O2 , signifikantna količina H 2O2 ostaje neiskorišćena, što ukazuje na nižu efikasnost ovakvog sistema u poređenju sa Fentonovim procesom.Štampana ugljenična elektroda (SPCE) zapreminski modifikovana sa MnO 2 kao medijatorom je primenjena za određivanje sadržaja H 2O2 u toku Fentonovog (Fe 2+ , H2O2 ) i vidljivom svetlošću potpomognutog foto-Fentonovog (Fe 2+ , H 2O2 , hν) procesa uklanjanja neonikotinoidnog insekticida acetamiprida (ACT). Pri optimizovanim uslovima (radni potencijal 0,40 V u odnosu na ZKE, fosfatni pufer pH 7,50 kao pomoćni elektrolit) amperometrijskog određivanja H 2O2 , postignuta je linearnost u opsegu koncentracija 0,01–1,24 mmol L-1(0,34– 42,2 µg mL -1 ) i vrednost RSD nije prelazila 4,2%. U ispitivanimuzorcima (nakon odgovarajućeg podešavanja pH vrednosti od 2,8 do 7,5 odmah nakon uzorkovanja radi stopiranja ili maksimalnog usporavanja procesa oksidacije, filtriranja, zamrzavanja i odmrzavanja neposredno pre merenja) sadržaj H 2O2 je određen metodom standardnog dodatka analiziranjem odgovarajućih amperometrijskih krivi. Paralelna HPLC-DAD merenja su vršena u cilju praćenja koncentracije/uklanjanja ACT. U slučaju foto-Fentonovog procesa (početne koncentracije 0,31; 2,0 i 3,0 mmol L -1 (70,0; 111,7 i 102,1 µg mL -1 ) za ACT, Fe 2+ i H 2O2, redom) nakon 10 min H 2O2 je izreagovao, a može se smatrati da je ACT uklonjen nakon 5 min. U toku Fentonovog procesa ACT je uklonjen nakon 20 min tretmana i oko 10% početne koncentracije H 2O2 je ostalo u sistemu neiskorišćeno.CPE je površinski modifikovane kompozitom na bazi nanočestica Pt (< 5 nm) i grafitizovanog ugljenika (Pt-C, 10% Pt na Vulkanu XC72) etodom nanošenja kapi. Nemodifikovana CPE i modifikovana (Pt-C/CPE) su okarakterisane primenom SEM/EDS i CV merenja. Pt-C/CPE je pokazala izuzetne elektrokatalitičke osobine u pogledu elektrohemijskeredoks reakcije H 2O2 u poređenju sa nemodifikovanom CPE u fosfatnom puferu (0,1 mol L -1 ; pH 7,50), a takođe i u acetatnom puferu (0,1 mol L -1 ; pH 4,50) kao pomoćnim elektrolitima. Prilikom amperometrijskog određivanja H 2O2 primenom Pt-C/CPE u model sistemima, zadovoljavajuća linearnost je postignuta u koncentracionom opseguH2O2od 0,15 do 1,45 µg mL -1 ,dok su vrednosti GO iznosile 0,06 µg mL -1 (pH 7,50, radni potencijal 0,20 V) i 0,10 µg mL -1 (pH 4,50, radni potencijal 0,50 V). Optimizovane analitičke metode su primenjene za određivanje sadržaja H 2O2 u komercijalno dostupnim proizvodima za ličnu negu: rastvoru za dezinfekciju (pH 7,50) i rastvoru za čišćenje kontaktnih sočiva (pH 4,50). Amperometrijski dobijeni rezultati su u dobrom slaganju sa rezultatima dobijenim primenom tradicionalne spektrofotometrijske metode bazirane na titanijum-sulfatu kao reagensu sa određenim koncentracijama 2,91% i 2,94% za dezinfekcioni rastvor i 3,04% i 3,17% za rastvor zakontaktna sočiva, redom. RSD je bila manja od 2%. Postignuti rezultati su u dobrom slaganju sa sadržajem H 2O2 deklarisanim od strane proizvođača (3%) u oba ispitivana uzorka. Pt-C/CPE je takođe testirana za praćenje koncentracije H2O2 u rastvoru za kontaktna sočiva u toku procesa njegove neutralizacije/razgradnje. Nakon 6 h procesa neutralizacije, 24,68 µg mL -1 je bila određena koncentracija H 2O2 , što je ispod dozvoljene H2O2 koncentracije u rastvoru za kontaktna sočiva imajući u vidu granicu koja izaziva iritaciju oka. CPE je površinski modifikovana višezidnim ugljeničnim nanocevima (MWCNT) i kompozitima MnO 2 -MWCNT ili Pt-MWCNT metodom nanošenja kapi radi pripreme jednostavnih, osetljivih i pouzdanih voltametrijskih senzora za određivanje H 2O2 u odabranom uzorku. Rezultati SEM/EDS analize kompozitnih materijala su potvrdili da su medijatori, čestice MnO 2 i Pt, nasumično raspoređeni na površini MWCNT i zastupljeni sa blizu 5% (m:m) u kompozitu izraženo preko Mn i Pt. CV merenja su vršena sa pripremljenim radnim elektrodama u acetatnom (pH 4,50), fosfatnom (pH 7,50) i boratnom (pH 9,18) puferu kako bi se okarakterisalo osnovno elektrohemijsko ponašanje H 2O2 i odabrali pogodni radni potencijali za amperometrijsko određivanje ovog ciljnog analita. Pt- WCNT/CPE je primenljiva za rad kako u fosfatnom puferu pH 7,50 tako i u acetatnom puferu pH 4,50 V kako pri negativnim tako i pri pozitivnim radnim potencijalima, pri čemu su vrednosti RSD uglavnom ispod 2,5%. U slučaju MnO 2 -MWCNT/CPE, na potencijalu 0,30 V i višim vrednostima, oksidacioni signali H 2O2 su signifikantni u blago alkalnoj sredini (pH 7,50), pri pH 4,50 ova elektroda pokazuje nezadovoljavajuće ponašanje, dok pri pH 9,18 ima prihvatljive performanse. Granice određivanja (GO) su bile u oblasti µg mL -1 . H 2O2 je određen u spajkovanom uzorku mleka metodom standardnog dodatka nakon odgovarajuće pripreme uzorka (pH podešavanje i centrifugiranje) i primenom optimizovane amperometrijske procedure (acetatni pufer pH 4,50, radni potencijal-0,75 V) koristeći Pt-MWCNT/CPE kao radnu elektrodu. RSD za tri ponovljena merenja je iznosila 2,5%, dok je prinos metode bio nešto veći od 71%. Kompozitni materijali koji se sastoje od MWCNT i čestica na bazi Pd (Pd-MWCNT) ili Pt (Pt-MWCNT) su primenjeni za pripremu zapreminski modifikovanih SPCE (Pd-MWCNT-SPCE i Pt-MWCNT-SPCE) i površinski modifikovane SPCE (Pd-MWCNT/SPCE). Ove elektrode, kao i nemodifikovana SPCE i MWCNT-SPCE, su okarakterisane primenom CV i amperometrije u fosfatnom puferu pH 7,50 radi određivanja H 2O2 . Pd-MWCNT-SPCE i Pd-MWCNT/SPCE su se pokazale pogodnim za određivanje H 2O2 na radnim potencijalima između -0,50 i 0,50 V, a PtMWCNT-SPCE na ispitivanim radnim potencijalima od -0,80 do 0,70 V. Ove elektrode su zatim modifikovane enzimom glukoza oksidazom (GOx) metodom nanošenja kapi rastvora GOx i Nafion ® -a na njihovu površinu, pri čemu je optimizovana količina nanetog biofilma. GOx/PdMWCNT-SPCE je pokazala bolje analitičke performanse za određivanje glukoze u poređenju sa GOx/Pd- WCNT/SPCE. Kao optimalan radni potencijal GOx/Pd-MWCNT-SPCE je odabrana vrednost potencijala -0,40 V u odnosu na ZKE, sa zadovoljavajućom linearnošću u ispitivanom opsegu koncentracija glukoze od 0,16 do 0,97 mmol L -1 (od 29,1 do 174 µg mL -1), dok je GO iznosila 0,14 mmol L -1 (25 µg mL -1 ). Optimizovana metoda zasnovana na GOx/Pd-MWCNT-SPCE je uspešno primenjena za određivanje glukoze u uzorku livadskog meda. Dobijeni rezultati su u dobroj saglasnosti sa onima dobijenim primenom komercijalno dostupnog aparata za merenje glukoze. Pogodan radni potencijal za GOx/Pt-MWCNT-SPCE je bio -0,50 V u odnosu na ZKE, pri čemu je zadovoljavajuća linearnost postignuta u ispitivanom opsegu koncentracija glukoze od 65,8 do 260,6 µg mL -1 , sa GO 35 µg mL -1 . Optimizovana metoda zasnovana na GOx/Pt-MWCNT-SPCE je uspešno primenjena za određivanje glukoze u u uzorku belog grožđa i uzorku tableta (Traubenzucker-bonbons), pri čemu su dobijeni rezultati u dobroj saglasnosti sa rezultatima dobijenim primenom Accu-Chek aparata. Na osnovu dobijenih rezultata može se zaključiti da su razvijene analitičke metode pre svega jednostavne, pouzdane i pogodne za dobijanje brzih informacija o sadržaju H 2O2 u različitim tipovima uzoraka. Svakako odabir pogodne radne elektrode, kao i optimizacija eksperimentalnih uslova su ključni faktori za uspešno određivanje H 2O2The aim of this doctoral dissertation was the development of fast and reliable voltammetric methods based on the application of simple and contemporary electrodes/sensors based on carbonaceous materials (carbon paste made of graphite powder and paraffin oil and screen printed carbon electrodes) for the determination of H 2 O2 in the selected complex model and real samples.For this purpose, applicability of different working electrodes was investigated.The amperometric method based on carbon paste electrode (CPE) bulk- modified with 5% (m:m) MnO 2 , under optimized conditions, with a working potential of 0.40 V vs. the saturated calomel elect rode (SCE) and a phosphate buffer solution (pH 7.50) as supporting electrolyte, enabled the quantitation of H 2 O2in the concentration interval from 1.4 to 65 µg mL −1 with a relative standard deviation (RSD) of less than 10%. This meth od was applied for the determination of the H 2 O2 consumption in samples of groundwater fro m the Central Banat region (Province of Vojvodina, Serbia) treated by the Fenton (Fe 2+ and H 2O2 ) and Fenton- like (Fe 3+and H 2O2 ) reagents to remove natural organic matter (NOM) at differentinitial concentrations of iron species, and of their molar ratios to the initial concentration of H2O2 . It was found that the form of Fe (Fe 2+ or Fe 3+ )and the molar ratio to H 2O2influenced the degree of the H 2O2 decomposition in the groundwater with high NOM content. Besides, in the case of the Fenton-like process, for all initial doses of Fe 3+ and H 2 O2, a sign ificant amount of H 2 O2 remained unused, whi ch also indicates a lower efficiency of such system compared to the Fenton process. Screen printed carbon electrode (SPCE) bulk-modified with MnO 2 as a mediator was applied for amperometric determination of the H 2 O2 content during the Fenton (Fe 2+ , H 2 O2 ) and visible light-assisted , photo-Fenton (Fe 2+ , H 2 O2 , hν) based removal of neonicotinoid insecticide acetamiprid (ACT). Under optimized conditions (working potential of 0.40 V vs. SCE, phosphate buffer pH 7.50 as supporting electrolyte) amperometric determination of H 2 O2 showed a linear dynamic range from 0.01 to 1.24 mmol L -1 (from 0.34 to 42.2 µg mL -1) and the RSD did not exceed 4.2%. In the investigated samples (after appropriate pH adjustment from 2.8 to 7.5 instantly after the sampling to stop or maximum decelerate the oxidation processes, filtering, and storage of the deep- frozen sample with defrosting immediately before the measurements) the H 2 O2 contents were determined by the standard addition method by analyzing the corresponding amperometric curves. Parallel HPLC-DAD measurements were performed to monito r the concentration/removal of ACT. In the case of the photo- Fenton process (initial concentrations: 0.31; 2.0 and 3.0 mmol L -1 (70.0; 111.7 and 102.1 µg mL -1 ) of ACT, Fe 2+ and H 2 O2, respec tively) after 10 min of irradiation H 2 O2 was consumed and it can be consi dered that ACT was removed after 5 min. During the Fenton process ACT was removed after 20 min of treatment and around 10% of the initial concentration of the H 2O2 remained still unused. CPE was surface modified with a composite of Pt nanoparticles (< 5 nm) on graphitized carbon (Pt-C, 10% Pt on Vulcan XC72) by simply dropcoating method. The unmodified CPE and the modified one (Pt-C/CPE) were characterized by EM/EDS and CV measurements. The PtC/CPE showed remarkable electrocatalytic propertiestoward the electrochemical redox reaction of H 2 O2 compared to modified CPE in phosphate buffer (0.1 mol L -1 ; pH 7.50), as well in acetatebuffer (0.1 mol L -1 ; pH .50) supporting electrolytes. Amperometry of H2O2 in the concentration range from 0.15 to 1.45 µg mL -1 with the Pt-C/CPE showed acceptable linearity, while the obtained values of LOQs were 0.06 µg mL -1 (pH 7.50, working potential 0.20 V) and 0.10 µg mL -1 (pH 4 .50, working potential 0.50 V). The proposed analytical methods were applied to the determination of the H 2O2 content in commercially available personal care products; i.e., disinfection (pH 7.50) and contact lens cleaning solutions (pH 4.50). The obtained amperometric results are in good agreement with those measured by traditional titanium sulfatereagent based spectrophotometric method with determined concentrations as 2.91% and 2.94% for the disinfection product, and 3.04% and 3.17% for the contact lens solution, respectively. RSD was lower than 2%. The obtained results are in a good agreement with the amounts of the H 2 O2 declared by producers (3%) in the both investigated samples. The Pt-C/CPE was also tested for monitoring of the H 2 O2 residual concentration in contact lens solution during its neutralization/decomposition rocess. At 6 h of neutralization treatment 24.68 µg mL -1 of the H 2 O2 was determined which is almost half of the allowedH2 O2 concentration in the case of the contact lens solution concerningthe limit of eye irritation. CPE was surface modified with multiwalled carbon nanotubes (MWCNT) and with composites of MnO 2 -MWCNT or Pt-MWCNT by drop coating method to prepare simply, sensitive and reliable volta mmetric sensors for the determination of H 2 O2 in selected sample. The results of the SEM/ EDS analysis of composite materials have confirmed that the mediators, MnO 2 and Pt articles, are randomly distributed on the surface of MWCNT and represent nearly 5% (m:m) of the composite expressed as Mn and Pt. CV measurements were performed with prepared electrodes in acetate (pH 4.50), phosphate (pH 7.50) and borate (pH 9.18) buffers to characterize the basic electrochemical behavior of H 2 O2 and to select the working potentials suitable for amperometric determination of this target analyte. The Pt-MWCNT/CPE performs well in phosphate buffer pH .50 and acetate buffer solution pH 4.50 in the negative as well as in the positive polarization range with RSD mainly lower than 2.5%. In case of MnO 2 -MWCNT/CPE at 0.30 V and above the H 2 O2 oxidation signal is rem arkable in slightly alkaline media (pH 7.50), at pH 4.50 this electrode showed poor behavior and at pH 9.18 offered acceptable performance. LOQs were in the µg mL -1 concentration range. H 2 O2 was determined in a spiked milk sample by standard addition method after appropriate sample preparation (pH adjustment and centrifugation) and using optimized amperometric p rocedure (acetate buffer pH 4.50, working potential -0.75 V) by Pt-MWCNT/CPE as a working electrode. RSD for three repeated measurements was 2.5%, while the recovery of the method was a bit higher than 71%. The composite materials consisting of MWCNT and Pd (Pd-MWCNT) or Pt containing particles (Pt-WCNT) were applied to the preparation of bulk- modified SPCEs (Pd-MWCNTSPCE and Pt-MWCNT-SPCE) and surface modifiedSPCE (Pd- MWCNT/SPCE). These electrodes, as well as unmodified SPCE and MWCNT-SPCE, were characterized by CV and amperometry in phosphate buffer solution of pH 7.50 for the H 2 O2 determination. Pd-MWCNT-SPCE and PdMWCNT/SPCEare convenient for the etermination of H 2O2 at working potentials from -0.50 to 0.50 V, and Pt-MWCNT-SPCE at investigated working potentials in the range from -0.80 to 0.70 V. These electrodes were then modified with glucose oxidase (GOx) by drop coating a solution of GOxand Nafion ® on their surface, whereby the applied amount of biococktail was optimized. GOx/PdMWCNT-SPCE showed better analytical performance for glucose determination in comparison with GOx/Pd-MWCNT/SPCE. The optimal working potential for GOx/Pd-MWCNT- SPCE was -0.40 V vs. SCE and satisfactory linearity was obtained in the investigated glucose concentration range from 0.16 to 0.97 mmol L -1 (from 29.1 to 174 µg mL -1 ), hile the LOQ was 0.14 mmol L -1 (25 µg mL -1 ). The optimized method based on GOx/Pd-MWCNT-SPCE was successfully applied to the determination of glucose in multifloral honey sample. The results are in a good agreement with those obtained by commercially available equipment for determination of glucose. Optimal working potential for GOx/Pt-MWCNT-SPCE was -0.50 V vs. SCE, and the satisfactory linearity was obtained in the investigated concentration range ofglucose from 65.8 to 260.6 µg mL -1 , with LOQ of 35 µg mL -1 . The optimized method based on GOx/Pt- MWCNT-SPCE was successfully applied for determination of glucose in white grape and glucose tablets (Traubenzucker-bonbons) samples, whereby the obtained results were in a good agreement with the results obtained by Accu-Chek device. Based on the results, the developed analytical methods are first of all simple, reliable and suitable for obtaining fast information about the content of H 2O2 in different types of samples. Certainly the selection of a suitable working electrode, as well as the optimization of experimental conditions are key factors for the successful determination of H2O2
Visual Basic 2012 Programmer's Reference
No full textRod Stephens is a VB programming guru and the author of more than two dozen programming books, including Stephens' Visual Basic Programming 24-Hour Trainer. He also writes frequently for such magazines as Visual Basic Developer, Visual Basic Programmer's Journal, and Dr. Dobb's Journal. Rod's VB Helper website (vb-helper.com) provides thousands of pages of tips, tricks, and code examples for VB programmer
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
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Basic writing (un)written : a critical discourse analysis and genealogy of developmental English in Texas
No full texttextThe purpose of this study was to investigate the discourses that author basic writing in Texas and question how instructors of basic writing at a community college are constructed as well as constructive through discursive practices. Elements of Critical Discourse Analysis (Luke, 1995-1996; Faircloth, 2000) were employed to analyze primary source documents, publications, presentations, meeting minutes, public forum transcripts, professional literature and policies pertaining to the practice of developmental English since the adoption of the Texas Academic Skills Program and the Texas Success Initiative. The discourses of failure, economy and science were identified as authoritative systems of conventions and norms that operate through the practice of basic writing. A Foucaultian genealogical lens was then applied both to explore the power relations and categorizations processes that undergird the material consequences (Valle, 2005) of the discourses as well as to identify how the narratives of basic writing faculty intersect with the discourses. Findings suggest that the discourses of failure, economy, and science function in a reciprocal manner to promote distorted truth claims about students and basic coursework that effectively limit possibilities for and lend to increased governmental control over the future practice of developmental education. The instructors’ stories, however, provide critical disruptions to the discourses. Viewing their alternative understandings of basic writing alongside the recurrent statements that have constructed popular understandings of developmental English, this study foregrounds the urgent need for more research from practitioners within the field and better channels of communicating their scholarship and professional experiences in the public arena.Curriculum and Instructio
Creating of individual education programs: did we understand the law?
No full textKreiranje Individualnih obrazovnih planova (IOP), u našoj zemlji,
nema jasno izrađenu metodologiju, a zakonodavna osnova nije dovoljno
precizna i uvodi veliki broj dilema, kako kod nastavnika redovne nastave,
tako i kod defektologa. U radu se analiziraju odgovori nastavnika predmetne
nastave i defektologa, u vezi sa osnovama izrade Individualnih obrazovnih
planova, sa ciljem da se ukaže na značaj izrade precizne metodologije za
kreiranje ovog dokumenta. Uzorak za istraživanje činilo je 72 defektologa i
24 nastavnika predmetne nastave, zaposlenih u 31 osnovnoj školi u Srbiji. U
istraživanju je korišćen upitnik Likertovog tipa, sastavljen od sedam tvrdnji.
Tvrdnje su se odnosile na definisanje svrhe IOP-a, potrebe za kreiranjem,
ciljeve, neophodne članove tima, kao i ocenjivanje učenika, prema ovom
dokumentu. Pored distribucije odgovora, praćena je i korelacija odgovora
nastavnika predmetne nastave i defektologa, kao i doslednost u odgovorima
koji su se ticali definisanja svrhe IOP-a, za koga se on izrađuje, prioriteta
u postavljanju ciljeva i ocenjivanja. Statističke analize ukazuju da 13,54%
ispitanika nije moglo da odgovori na svaku od zadatih tvrdnji. Najveće nedoumice
odnosile su se na tvrdnje koje su se ticale prioriteta u kreiranju
IOP-a, kao i tvrdnje da li defektolog može da realizuje nastavu prema IOP-u
u redovnoj školi (po 20,8% ispitanika je bez odgovora). Beleži se statistički
visoko značajna razlika u odgovorima nastavnika predmetne nastave i defektologa
(p=0,000) na tvrdnje da se IOP, bez razlike, izrađuje za svu decu
sa smetnjama u učenju i razvoju, da je akademsko postignuće prioritetni cilj
u IOP-u i na tvrdnju da nastavu za učenika koji radi prema IOP-u realizuje
isključivo nastavnik redovne nastave. Ne beleži se dosledan stav u pogledu
definisanja svrhe IOP-a i ostalih praćenih varijabli.Rezultati jasno ukazuju
na, još uvek, prisutne probleme u razumevanju i tumačenju izrade i svrhe
individualnog obrazovnog plana, kao i na neophodnost kreiranja precizne
metodologije njegove izrade i implementacije.The precise methodology for creating Individual Education Programs (IEP) still
missing in our country. Thus, teachers in regular classroms, as much as special education
teachers cope with many dificulties in understanding the law and creating IEP. The
answers of regular classrom professors and special education teachers about the bases
of Individual Education Plan`s creating process were analised in this paper. Necesisity
of good and precise methodology for creating IEP were pointed out.Seventytwo special
education teachers and 24 professors from 31 Elementary schools in Serbia answered
on seven items structered as claims. The claims were related to defining the aim of IEP,
reasons for its creating, structure of a team, and assessment in IEP. We were interested in
distribution of answeres as much as in correlation between answers of special education
teachers and professors, but in concistency of respons between claim about definig the
aim of IEP and following claims: Do we create IEP for all children with special needs,
without exceptions; What is priority to be done in IEP; Is mark „excellent five“ allowed
if child has IEP. According to statistic, 13,54% of a sample, in averige, colud not give the
answer on each claim. The most dificulties were in answering the claim about priority
to be done in IEP, and about the possibility for special education teachers to realise class
in regular schools (20,8% of sample colud not answer the claim). There are high statistic
diferences between special education teacher and professors (p=0,000) when answering
the claim about creatin IEP for all children with special needs; about priority to be done
in IEP; and when answering the claim about possibility for special education teachers to
realise class school.s. There isn`t concistency of respons between claim about defining
the aim of IEP and all other variables. The results of this research confirm hypothesis
that the legal bases for creating IEP in Republic of Serbia must be reconstructed. At the
same time, precise metgodology base for developmenting IEP must be done
INTEGRATION OF IMMIGRANT CHILDREN INTO SLOVENIAN BASIC SCHOOLS: THE DIFFERENCES BETWEEN URBAN AND RURAL BASIC SCHOOLS
No full textDanašnji svet je poln številnih različnih družb in kultur. Tudi ljudje smo si med seboj različni. Na podlagi teh različnosti se predsodki lahko razvijejo zelo hitro. Zato težko rečemo, da v današnjem svetu nestrpnosti ni ter da predsodki ne obstajajo.
Slovenija ima, tako kot druge države, svojo zgodovino priseljevanja drugih narodov, ki se vključujejo v slovensko okolje, njihovi otroci pa v slovenski vzgojno-izobraževalni sistem. V šolski prostor se tako vključujejo učenci, ki prihajajo iz drugih držav in iz drugega kulturnega prostora, zato je izredno pomembno, da vzgojno-izobraževalne institucije ter zaposleni v njih težijo k enakovrednemu obravnavanju vseh učencev.
Namen magistrskega dela je bil raziskati, kako se izvaja vključevanje otrok priseljencev v slovenske osnovne šole, ter ugotoviti, ali pri tem obstaja razlika med mestnimi in podeželskimi osnovnimi šolami v Sloveniji. Pri tem so bile osnova raziskovalnega dela magistrske naloge Smernice za vključevanje otrok priseljencev v vrtce in šole (2011), ki jih je izdal Zavod Republike Slovenije za šolstvo.
Z anketnim vprašalnikom, ki smo ga poslali strokovnim delavcem, zaposlenim v svetovalnih službah na osnovnih šolah v Sloveniji, smo raziskali, koliko in do katere mere svetovalne službe v osnovnih šolah poznajo naveden dokument, kako pogosto se z njim srečujejo in ali pri vključevanju otrok priseljencev dokument uporabljajo kot pomoč. Ugotavljali smo tudi, s katero dokumentacijo si pri vključevanju otrok priseljencev še pomagajo. Ob tem smo prav tako raziskali, če obstaja razlika pri vključevanju otrok priseljencev med mestnimi in podeželskimi osnovnimi šolami.
Rezultati so pokazali, da večina anketiranih dokument sicer pozna natančno ali delno, vendar ga kot pomoč v določenih primerih dejansko uporablja le približno polovica. Ugotovili smo tudi, da razlike pri uspešnem vključevanju učencev priseljencev med osnovnimi šolami v mestu in na podeželju ne obstajajo. Na podlagi rezultatov smo sklenili, da lokacija osnovne šole torej ni toliko pomembna za uspešno vključevanje učencev priseljencev v slovenske osnovne šole. Pomembnejše so zainteresiranost, predanost delu, lojalnost in strokovnost zaposlenih v osnovnih šolah.Today\u27s world is full of many different societies and cultures. Even the people, we are all different. Based on these differences, the prejudices can develop very quickly. It is therefore difficult to say that in today\u27s world there is no existing intolerance and prejudices.
Slovenia has, like other countries, its own history of immigrations of other nations, which are becoming involved in the Slovenian environment and their children are included in Slovenian educational system. The school system includes students who are coming from other countries and from other cultural backgrounds, so it is very important that educational institutions and their employees treat all students equally.
The purpose of the master thesis was to explore how the integration of immigrant children is carried out in Slovenian basic schools and to determine whether there is a signifficant difference between urban and rural basic schools in Slovenia. The basis of the research was the document Guidelines for the integration of immigrant children in kindergartens and schools (2011), which was published by the Institute of Education of the Republic of Slovenia.
With the survey questionnaire, which was sent to proffesional workers, who are employed in school guidance service at basic schools in Slovenia, we have analysed how much the guidance service workers in basic schools are familiar with the mentioned document, how closely they know it and how often they make use of the document. Also we have analysed the documentation they also help themselves with in the matter of integration of immigrant children. At the same time we have also investigated if there is a difference in the integration of immigrant children between urban and rural basic schools in Slovenia.
The results indicated that the majority of respondents know the mentioned document exactly or partially, but for help in certain situations actually use it only about half of respondents. We have also found out that the differences in the successful integration of immigrant children do not exist between basic schools in urban and rural areas. Based on these results, we concluded that the location of basic schools, therefore, is not so much important for the successful integration of immigrant children in Slovenian basic schools. More important is the desirability, dedication to work, loyalty and professionalism of employees in basic schools
Dance and movement therapy ‒ comparative analysis of basic methodological concepts
No full textU radu su tretirane i analizarane mogućnosti komparacije različitih
metodskih postupaka i pristupa tretmanu i rehabilitaciji dece, adolescenata i
odraslih sa različitim vrstama razvojnih smetnji sa akcentom na intelektualnoj
ometenosti i oštećenjima sluha. Ukazano je na posebne vrednosti primene novih
rehabilitacionih postupaka i strategija osposobljavanja osoba sa smetnjama i
poremećajima razvoja u svakodnevnom životu kao i mogućnostima primene ovih,
do sada manje poznatih i nedovoljno primenjivanih rehabilitacinih strategija
tretmana i edukacije u specijalnoj edukaciji i rehabilitaciji kod nas, a prema
razrađenim modelima i iskustvima zemanja u okruženju kao i inostranih zemalja.The paper discusses the possibility of comparing different methodological
approaches to the treatment and rehabilitation of the children and youth with
different disabilities of different degree of complexity, with special emphasis on
the analysis of intellectual disabilities and hearing impairments. We point out
special values of the implementation of new rehabilitation strategies in the
population with different developmental disabilities in everyday life, as well as the
possibility of implementing these strategies in special education and rehabilitation
in our environment, defined through the conceptual frame abroad
Neural network based pattern recognition of technical trading indicators, statistical evaluation of their predictive value and an historical overview of the field
No full textThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 149-156).We revisit the kernel regression based pattern recognition algorithm designed by Lo, Mamaysky, and Wang (2000) to extract nonlinear patterns from the noisy price data, and develop an analogous neural network based one. We argue that, given the natural flexibility of neural network models and the extent of parallel processing that they allow, our algorithm is a step forward in the automation of technical analysis. More importantly, following the approach proposed by Lo, Mamaysky, and Wang, we apply our neural network based model to examine empirically the ability of the patterns under consideration to add value to the investment process. We discover overwhelming support for the validity of these indicators, just like Lo, Mamaysky, and Wang do. Moreover, this basic conclusion appears to remain valid across different levels of smoothing and insensitive to the nuances of pattern definitions present in the technical analysis literature. This confirms that Lo, Mamaysky, and Wang's results are not an artifact of their kernel regression model, and suggests that the kinds of nonlinearities that technical indicators are designed to capture constitute some underlying properties of the financial time series itself. Finally, we complement our empirical analysis with a historical one, focusing on the origins of trading and speculation in general, and technical analysis in particular.by Jasmina Hasanhodzic.S.M
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