No description available.

Constitués de plusieurs composants (granulats naturels et pâte de ciment adhérente), les GBR ne sont à l’heure actuelle pas utilisés largement dans la formulation de nouveaux bétons. Les propriétés médiocres des GBR compliquent considérablement la détermination de la quantité d’eau efficace dans le béton frais. Tout d’abord, une étude bibliographique va mettre en évidence la grande dispersion des résultats des essais de caractérisation des GBR et des propriétés des bétons recyclés à l’état frais et durci. Ensuite, une étude vise à analyser l’hétérogénéité des GBR et des granulats de béton concassé (GBC) par rapport à différents paramètres : aux impuretés granulaires, à la densité et à la teneur en pâte de ciment, au malaxage du béton parent, et au niveau de la capacité d’absorption d’eau des GBC en fonction de leur état de pré-humidification. Enfin, une dernière partie est destinée à améliorer la maîtrise de l’eau efficace réelle dans la fabrication du béton recyclé. La cinétique d’absorption des GBC dans une pâte de ciment est tout d’abord étudiée. Ensuite, l’évolution de l’eau efficace durant le malaxage de bétons à base de GBC est investiguée au moyen d’une méthode originale basée sur le suivi des courbes de puissance du malaxeur. Finalement, l’effet d’un malaxage sous vide relatif sur les propriétés des bétons à base de granulats naturels et des bétons à base de GBC est étudié. / Composed of several components (natural aggregates and adherent cement paste), RCA are not widely recommended in new concrete formulations. Their poor properties considerably complicate the determination of the effective water in fresh concrete. In a first part, a bibliographic study will highlight the wide dispersion of the results of characterization tests of RCA and the properties of fresh and hardened recycled concrete. In a second part, the heterogeneity of RCA and crushed concrete aggregates (CCA) is studied according to different parameters: granular impurities, density, cement paste content, mixing of parent concrete, and water absorption capacity according to their pre-humidification. The third part consists of three experimental studies that intend to improve effective water control in the manufacture of recycled concrete. The absorption kinetics of CCA in a cement paste is first studied. Then, the evolution of effective water in fresh concrete during mixing is studied using an original method based on the power evolution of the mixer. Finally, the effect of vacuum mixing on the properties of ordinary and recycled concretes is investigated.

The use of recycled concrete aggregates (RCA) has gained increased attention in the past few decades as an alternative to decrease the carbon footprint of concrete construction. Yet, most of the research performed so far demonstrates that RCA concrete displays inferior performance in the fresh and hardened states when compared to conventional concrete (CC). The latter is believed due to the fact that very often the different microstructure of RCA is not accounted for while the mix-proportioning of RCA concrete. Recently, a number of mix-design procedures accounting for RCA microstructure have been proposed. Amongst them, the Equivalent Volume (EV) method seems to be quite promising. The EV method may proportion RCA concrete made of coarse (CRCA) or fine (FRCA) RCA and is based on a companion CC. Previous research has demonstrated that the fresh and hardened properties of EV mix-designed CRCA are suitable for structural applications. Yet, very few research, analysis and quantification have been conducted on the fresh behaviour of EV mix- proportioned FRCA concrete. This work presents a comprehensive study on the rheological behaviour of EV mix-designed CRCA and FRCA concrete presenting distinct features (i.e. inner qualities, mineralogy, fabrication process, etc.) through the use of a planetary rheometer (IBB). Results show that the EV is capable of proportioning low embodied energy CRCA and FRCA concrete with shear thinning profiles. The latter suggests that these mixtures are suitable for applications under high torque regimes such as vibrated or pumped concrete.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Introduction: Regenerative endodontic therapy in immature teeth promotes continuation of root development and likely increases the prognosis of these teeth. The use of double antibiotic paste (DAP), equal parts of ciprofloxacin and metronidazole, followed by the dentin conditioner, ethylenediaminetetraacetic acid (EDTA), has been suggested for canal disinfection and facilitation of stem cell attachment/proliferation, respectively. However, the effect is unknown when all these agents are used on on radicular dentin surfaces to facilitate the level of stem cell proliferation. Objectives: The aim of this in-vitro study is to compare the proliferation of human dental pulp stem cells (hDPSCs) on human radicular dentin treated with two different concentrations of DAP followed by EDTA. Materials and Methods: Human premolars and incisors were prepared into standardized polished 4 mm x4 mm radicular dentin specimens. Groups of specimens were treated with DAP 500 mg/mL, DAP 1 mg/mL, DAP 500 mg/mL followed by 17-percent EDTA, DAP 1 mg/mL followed by 17-percent EDTA; 17% EDTA, or no treatment. All groups treated with antibiotics were incubated with DAP at 37°C for one week. All specimens were washed with distilled water. The hDPSCs were seeded across all specimens and unattached cells were collected after 24 hours. LDH assay was completed on unattached cells for quantification. Three days after attachment, WST viability and LDH cytotoxicity assays were performed. Hypothesis: There is no significant difference in hDPSC viability, unattachment, and cytotoxicity on dentin specimens treated with DAP and 17-percent EDTA. Clinical Significance: These results can be used to help identify the best treatment concentrations when using DAP and/or EDTA to promote endodontic regeneration. Results: The results demonstrated significantly less viability of hDPSCs on specimens treated with 500 mg/mL DAP with and without 17-percent EDTA. Groups treated with 1 mg/mL DAP, 1 mg/mL DAP and 17-percent EDTA, and 17-percent EDTA alone had no statistically significant difference in viability compared with control untreated dentin. The results of the unattached cells from the LDH demonstrated that cells from the specimens treated with solely 500 mg/mL and 1 mg/mL DAP had significantly higher levels of unattached cells when compared with all other groups. The LDH assays in summation with the WST assays showed a trend of a lack of proliferation on groups treated with 500 mg/mL DAP with and without 17-percent EDTA. Conclusions: Paste-like concentrations (500 mg/mL) of DAP are detrimental to hDPSC viability, whereas the present study supports the use of low-concentration antibiotics consistent with current recommendations for intracanal medicaments used during endodontic regenerative procedures.

<p>Hydrated portland cement provides the solid adhesive matrix necessary to bind aggregate (sand and gravel) into concrete. The hydration reaction requires water, however the products of the reaction limit further diffusion of water to unreacted cement. Superabsorbent polymer (SAP) hydrogel particles absorb mixing water, then subsequently desorb when the relative humidity drops, serving as internal water reservoirs within the cement matrix to shorten diffusion distances and promote the hydration reaction in a process called internal curing. Internally cured cementitious mixtures exhibit an increased degree of hydration and reduced shrinkage and cracking, which can increase concrete service life. Increased service life can, in turn, reduce overall demand for portland cement production, thereby lowering CO2 emissions.</p> <p>This dissertation addresses practical implementation questions key to the translation of SAP hydrogel internal curing technology to from the benchtop to the field in transportation applications, including: (1) What effects do mix design adjustments made to increase mixture flow when using SAP have on cementitious mixture properties? and (2) What effect do cementitious binder characteristics have on SAP performance?</p> <p>The addition of SAP to a cementitious mixture changes the mixture’s flow behavior. Flow behavior is an important aspect of concrete workability and sufficient flow is necessary to place well consolidated and molded samples. Often, additional water is added to mixtures using SAP to account for the absorbed water, however cementitious mixture workability is often tuned using high range water reducing admixtures (e.g., polycarboxylate ester-based dispersants). Fresh and hardened properties of mortars were characterized with respect to flow modification method (using the mortar flow table test; compressive strength at 3, 7, and 28 days; flexural strength at 7 and 28 days; and microstructural characterization of 28-day mortars). At typical doses, it was found that the addition of extra water lowers the resulting compressive and flexural strength, while high range water reducing admixtures administered at doses to achieve sufficient mortar flow did not compromise compressive or flexural strength.</p> <p>The SAPs used in cement are generally poly(acrylamide-acrylic acid) hydrogels and are not chemically inert in high ionic-load environments, such as cement mixtures. The behavior of an industrial SAP formulation with characterized across five different cement binder compositions with respect the cement hydration reaction (using isothermal calorimetry, thermogravimetric analysis of hydration product fraction, and scanning electron microscopy (SEM)/energy dispersive x-ray spectroscopy (EDS) microstructural analysis), the absorption behavior of the SAP, and the fresh and hardened properties of SAP-cement composites (mortar flow and compressive and flexural strength). The change in properties induced by the addition of SAP was similar across ASTM Type I cements from three manufacturing sources, suggesting that SAP internal curing can be implemented predictably over time and geography. Excitingly, in analysis of cement systems meeting different ASTM standards (Type III and Type I with 30% replacement by mass with ground blast furnace slag), synergistic and mitigating reaction behaviors were observed, respectively, in Type III and slag cement, suggesting that further study of SAP with these cement systems could be of particular interest.</p>

<div> <div> <div> <p>Transient liquid phase sintering (TLPS) technologies are potential low-temperature solders for sustainable replacements of lead-based solders and high-temperature lead-free solders. Compared to solid-state sintering and lead-free solders, TLPS uses lower temperatures and is, thus, suitable for assembling temperature-sensitive components. TLPS is a non- equilibrium process and determining the kinetics is critical to the estimation of processing times needed for good joining. The tin-indium (Sn-In) system with a eutectic temperature of 119°C is being considered as the basis for a TLPS system when combined with tin. Most models of TLPS include interdiffusion, dissolution, isothermal solidification, and homogenization and are based on simple binary alloys without intermediate phases. The Sn-In system has two intermediate phases and thus the reaction kinetics require additional terms in the modeling. Differential Scanning Calorimetry (DSC) has been used to measure the response of Sn-In alloys during the transient liquid phase reaction. Preparation of tin indium alloys for microstructural analysis is challenging due to their very low hardness. This study uses freeze-fracturing of the tin indium alloys to obtain sections for microstructural analysis. The combination of DSC and microstructure analysis provides information on the reaction kinetics. It was observed that the solid/liquid reaction does not proceed as quickly as desired, that is, substantial liquid remains after annealing even though the overall composition is in the single-phase region in the phase diagram. </p> </div> </div> </div>

Despote the indisputable advantages of fine-pitch components, is need to calculate with a few trouble during production, especially increased requirements for accuracy of mounting and solder printing. In this work I’m concerned with problems of solder printing for these components and evaluation using SPC. For the evaluation I used 3D paste inspection based on laser scanning of the surface. The output of this work is to describe the principles of solder printing and elaborating of GR&R, SPC analysis and histograms of solder printing for some outputs. I focused in my master thesis on motive design change of problematic components and economic evaluation of the adjustments.

<p>Danas, u raznim analitičkim laboratorijama postoji veći broj analitičkih protokola,<br />zasnovanih bilo na izuzetno sofisticiranim ili jednostavnijim tehnikama, koji služe za<br />određivanje različitih ciljnih analita od farmakolo&scaron;kog značaja. Među tim grupama ciljnih analita pripadaju i antibiotici koji predstavljaju veliko otkriće u oblasti medicine i zahvaljujući njima spa&scaron;eno je vi&scaron;e od sedam miliona života, ali pored navedenih koristi, antibiotici mogu da izazovu&nbsp; veliki broj neželjenih efekata i žučne kiseline zajedno sa svojim derivatima, koji su fiziolo&scaron;ki deterdženti, mogu biti citotoksične za organizam ako se njihova koncentracija ne kontroli&scaron;e. U ovoj doktorskoj disertaciji prikazan je razvoj analitičkih metoda pre svega voltametrijskihmetoda u kombinaciji sa jednostavnim i savremenim elektrodama/senzorima za određivanje&nbsp; odabranih analita kao &scaron;to je antraciklični antibiotik doksorubicin (DOX), makrolidni antibiotici<br />eritromicin-etilsukcinata (EES), azitromicina (AZI), klaritromicina (CLA) i roksitromicina&nbsp; (ROX) i 3-dehidro-deoksiholne kiseline.</p><p>Voltametrijska karakterizacija i određivanje gore navedenih antibiotika primenom obnovljive srebro-amalgam film elektrode (Hg(Ag)FE)rađena je direktnom katodnom&nbsp; voltametrijom sa pravougaonim talasima (SWV) i visoko osetljivom adsorptivnom voltametrijom sa pravougaonim talasima (SW-AdSV) u Briton-Robinson puferu, kao pomoćnom elektrolitu, obuhvatajući &scaron;irok opseg pH vrednosti. Odgovor DOX-a primenom&nbsp; Hg(Ag)FE&nbsp;praćen je u intervalu potencijala od -0,20 do -0,80 V.&nbsp; Za analizu tragova, optimizacija metode ukazuje da su optimalni parametri za analitički pik na potencijalu (Ep ) -0,57 V u odnosu na zasićenu kalomelovu elektrodu (ZKE): pH 6,0, potencijal&nbsp; akumulacije -0,20 V i vreme&nbsp; akumulacije 140 s. U model rastvoru, DOX je određivan u koncentracionom opsegu 4,99-59,64&nbsp; ng mL^-1. Razvijena SW-AdSV metoda je primenjena za određivanje DOX-a u obogaćenom uzorku humanog urina. Niža koncentracija DOX-a 9,89ng mL^-1&nbsp;u voltametrijskoj&nbsp; ćeliji je određivana sa relativnom standardnom devijacijom (RSD) manjom od 6,0%. &Scaron;to se ispitivanih makrolida tiče oni su pokazali redukcione signale u dalekoj negativnoj oblasti potencijala. Ispitivanja direktnom katodnom SWV rađena su u opsegu potencijala od -0,75 V do -2,00 V u odnosu na ZKE, pri čemu su dobijena jedan ili dva redukciona pika u opsegu potencijala od -1,5 V do -1,9 V. Oblik i intenzitet signala zavisi od primenjene pH vrednosti u &scaron;irokoj pH oblasti. Za analitičke svrhe, radi razvoja direktne katodne SWV i adsorptivne inverzne/striping SWV metode, pogodnim su se pokazale neutralna i slabo alkalna sredina tj. pH 7,0 sa&nbsp; E_p na -1,67 V u odnosu na ZKE za ROX i EES i pH 7,2 sa E_p na -1,85 V u odnosu na ZKE za AZI i pH 7,4 sa E_p na -1,64 V u odnosu na ZKE za CLA. Na osnovu snimljenih cikličnih voltamograma na&nbsp; optimalnim pH vrednostima, može se predložiti adsorptivno-kontrolisan kinetički proces na elektrodi u slučaju sva&nbsp; četiri ispitivana jedinjenja. Takođe,&nbsp; ¹H NMR merenja uz potiskivanje&nbsp; signala vode u pH oblasti između pH 6,0 i 10,5 ukazuju na to da su makrolidni molekuli pri optimalnim analitičkim uslovima predominantno u protonovanoj formi preko tercijerne amino grupe &scaron;to potpomaže, u sva&nbsp; četiri slučaja, njihovu adsorpciju na odgovarajuće polarizovanoj Hg(Ag)FE. Optimizovane direktne katodne SWV metode&nbsp; pokazuju dobru linearnost u koncentracionom opsegu 4,81-23,3&nbsp; &micro;g mL^-1 , 4,53-29,8&nbsp; &micro;g mL^-1 , 1,96-28,6&nbsp; &micro;g mL^-1 i 1,48-25,9 &micro;g mL^-1 za AZI, EES, CLA odnosno ROX. Razvijene SW-AdSV metode rezultiraju u linearnom odgovoru pri nižim koncentracionim intervalima 1,0-2,46 &micro;g mL^-1 ,&nbsp; 0,69-2,44&nbsp; &micro;g mL^-1, 0,05-0,99 &micro;g mL^-1 i 0,10-0,99&nbsp; &micro;g mL^-1 , za AZI, EES, CLA i ROX. RSD za sve razvijene metode nije veća od 1,5% izuzev SWV metode u slučaju AZI-a gde je 4,5%. Direktna katodna SWV metoda&nbsp; je uspe&scaron;no primenjena za određivanje EES-a u farmaceutskom proizvodu Eritromicin^&reg; dok SW-AdSV metoda je primenjena u slučaju određivanja EES-a u obogaćenom uzorku humanog urina i&nbsp;za određivanje ROX-a u farmaceutskom proizvodu Runac^&reg; . U svim pomenutim slučajevima, primenjena je metoda standardnog dodatka. Pouzdanost i tačnost elaboriranih procedura u slučaju određivanja EES-a u model sistemu i&nbsp; farmaceutskom proizvodu Eritromicin^&reg; su potvrđena poređenjem sa rezultatima dobijenim primenom HPLC-DAD metode.</p><p>Nakon preliminarnih studija 3-dehidro-deoksiholne&nbsp; kiseline/3-dehidro-deoksiholata primenom elektrode od staklastog ugljenika (GCE), gde je uočeno da ne dolazi do formiranja redukcionog signala u Briton-Robinson puferu između pH 5,0 i 11,8 primenom direktne katodne SWV, bizmut-film je izdvojen&nbsp; <em>ex situ</em> na povr&scaron;ini iste elektrode od staklastog ugljenika (BiF-GCE) iz uobičajeno kori&scaron;ćenog rastvora za elektrodepoziciju (0,02 mol L^-1 Bi(NO₃)₃, 1,0 mol L^-1 HCl i 0,5 mol L^-1 KBr) i tako pripremljena elektroda je primenjena za karakterizaciju i određivanje pomenutog jedinjenja u alkalnoj sredini. Redukcioni signal ispitivanog analita od analitičkog značaja je uočen jedino primenom BiF-GCE u Briton-Robinson puferusa pH vrednostima između 9,5 i 11,8 u režimu adsorptivne inverzne/stripingvoltametrije sa pravougaonim talasima, dok u slučaju direktnih katodnih SWV eksperimentalnih uslova uočen je slab redukcioni pik sa niskom strujom maksimuma pika. Optimizovani eksperimentalni uslovi za određivanje 3-dehidro-deoksiholata obuhvataju odgovarajuće kondicioniranje elektrode uključujući kondicioniranje&nbsp; <em>ex situ</em> pripremljene BiF-GCE u Briton-Robinson pomoćnom elektrolitu pH 11,8 do stabilizacije struje bazne linije elektrohemijskim cikliranjem potencijala radne elektrode u potencijalskom opsegu između -1,00 i -2,00 V u odnosu na ZKE (blizu 15 puta) i primenu dva ključna parametara adsorptivne voltametrije sa pravougaonim talasima: vreme akumulacije od 30 s i potencijal akumulacije&nbsp; -1,00 V u odnosu na ZKE. Zbog relativne asimetričnosti dobijenih redukcionih signala ispitivanog analita sa&nbsp; E_p na -1,35 V u odnosu na ZKE, &scaron;to je takođe prisutno i u slučaju primene SW-AdSV, određivanje ispitivanog analita je zasnovano na linearnoj zavisnosti između povr&scaron;ine pika redukcionog signala&nbsp; spitivanog analita i njegove odgovarajuće koncentracije i postignuta granica detekcije je 1,43 &micro;g mL^-1 sa dva linearna opsega kalibracione krive od 4,76 &micro;g mL^-1 do 13,0 &micro;g mL^-1 i od 13,0 &micro;g mL^-1 do 23,1 &micro;g mL^-1 za razvoj analitičke metode. RSD metode je 3,22%. Dodatni eksperimenti, elektroliza ispitivanog analita na potencijalu -1,55 V (blizu maksimuma pika ciljnog analita) u odnosu na ZKE su rađeni primenom GCE u obliku ploče (povr&scaron;ina 33,52 cm 2 ) modifikovane sa&nbsp; <em>ex situ&nbsp;</em>pripremljenim bizmut-filmom. Rastvor od interesa uzorkovan je na početku eksperimenta, nakon 2,5 h i nakon 4,5 h tretmana. Ovakvi uzorci su analizirani primenom ¹H NMR merenja uz potiskivanje signala vode u puferskom rastvoru pH 11,8. Može se pretpostaviti da tokom elektrolize 3-dehidro-deoksiholata dolazi do redukcije keto grupe prisutne u strukturi ispitivanog analita.</p><p>Na osnovu literaturnih podataka da neki od ciljnihmakrolidnih antibiotika kao &scaron;to je npr. azitromicin pokazuju oksidativno pona&scaron;anje na elektrodi od ugljenične paste i elektrodi od zlata deteljna karakterizacija i određivanje&nbsp; četiri makrolidna antibiotika rađena je primenom&nbsp; asične&nbsp;elektrode od ugljenične paste (CPE) koja se sastoji samo od grafitnog praha i parafinskog ulja sa optimizovanih direktnih anodnih SWV metoda. U slučaju EES-a i AZI-a diferencijalna pulsna voltametrija (DPV) je testirana za iste svrhe. Ključni&nbsp; parametar u slučaju razvoja analitičkih voltametrijskih metoda je odabir pH vrednosti pomoćnog elektrolita gde je oblik/simetričnost i intenzitet oskidacionog pika glavni kriterijum prilikom odabira. Kao odgovarajuće pH vrednosti za voltametrijsko određivanje EES-a primenom SWV metode odabrana je pH 8,0 sa E_p na 0,83<br />V u odnosu na ZKE, dok u slučaju DPV metode pH 12,0 sa&nbsp; E_p na 0,55 V u odnosu na ZKE je bila najpogodnija za analitičke svrhe. Za određivanje AZI-a, u slučaju obe SWV i DPV metode pH 7,0 se pokazala najpogodnijom sa E_p analitičkog signala na 0,85 V odnosno 0,80 V u odnosu na ZKE, dok u slučaju CLA i ROX koji su ispitivani samo primenom SWV metode za analitičke svrhe pH 12,0 je bila najpogodnija sredina sa E_p analitičkog signala na 0,65 V odnosno na 0,63 V&nbsp;u odnosu na ZKE. Postignute granice detkcije primenom nemodifikovane CPE i direktne anodne SWV su uglavnom u submikrogramskom koncentracionom opsegu 0,17 &micro;g mL^-1 , 0,32&nbsp; &micro;g mL^-1 i 0,30&nbsp; &micro;g mL^-1, u slučaju EES-a, AZI-a i ROX-a i u niskom mikrogramskom koncentracionom opsegu 1,43&nbsp; &micro;g mL^-1 za CLA. Razvijena SWV metoda sa jednostavnom CPE pokazala se pogodnom za određivanje ROX-a u komercijalnom proizvodu Runac^&reg; tableti. U slučaju optimizovanih DPV metoda postignute granice detekcije za EES i AZI su u niskom mikrogramskom&nbsp; koncentracionom opsegu 1,03&nbsp; &micro;g mL^-1 odnosno 1,53&nbsp; &micro;g&nbsp; mL^-1 . U želji da se&nbsp;postigne niža granica detekcije za AZI, DPV metoda&nbsp; je testirana u kombinaciji sa&nbsp; CPE radnom elektrodom povr&scaron;inski modifikovanom sa zlatnim nanočesticama&nbsp; prečnika 10 nm (Au-CPE) i&nbsp; postignuta granica detekcije je 0,95&nbsp; &micro;g mL^-1 sa&nbsp; E_p analitičkog signala na 0,80 V u odnosu na&nbsp; ZKE. RSD metode u slučaju Au-CPE je 3,5%, dok je u slučaju nemodifikovane CPE 6,0%.&nbsp; Linearnost analitičke metode zasnovane na primeni Au-CPE je dva puta &scaron;ira nego u slučaju&nbsp; primene nemodifikovane CPE.</p><p>Na osnovu dobijenih rezultata može se zaključiti da&nbsp; odgovarajuće kombinacije&nbsp; optimizovanih voltametrijskih tehnika sa ekolo&scaron;ki prihvatljivim i lako primenljivim radnim&nbsp; elektrodama, kao &scaron;to su Hg(Ag)FE, BiF-GCE i CPE zajedno sa Au-CPE, rezultuju razvojem&nbsp; pouzdanih analitičkih metoda, kako u oksidacionim tako i u redukcionim proučavanjima, koje&nbsp; često omogućuju&nbsp; određivanje tragova analita od farmakolo&scaron;kog značaja u jednostavnim, a u&nbsp;nekim slučajevima i u složenim sistemima.&nbsp;</p> / <p>Nowadays in different analytical laboratories there is the increasing number of analytical protocols, either based on highly sophisticated or simpler measurements techniques, which serving for determination of different target analytes of pharmacological importance. Among such target groups of the analyte belongs the antibiotics which present a great discovery in the field of medicine and thanks to them were saved more than seven million people but beside to the mentioned great benefits, antibiotics can cause a large number of side effects and bile acids together with their derivatives which are physiological detergents but if their concentration is not<br />controlled they can be cytotoxic to the body. In the present doctoral dissertation the development of analytical methods, primarily analytical voltammetric methods in combination with simple and contemporary electrodes/sensors, for the determination of selected analytes as antracycline antibiotic doxorubicin (DOX), macrolide antibiotics erythromycin ethylsuccinate (EES), azithromycin (AZI), clarithromycin (CLA) and roxithromycin (ROX) and 3-dehydrodeoxycholic acid were performed.</p><p>Voltammetric characterization and determination of the above mentioned antibiotics using a renewable silver-amalgam film electrode (Hg(Ag)FE) was performed by direct cathodic square-wave voltammetry (SWV) and by highly sensitive adsorptive square-wave voltammetry (SW-AdSV) in aqueous Britton-Robinson buffer solutions as supporting electrolyte covering the wider pH range. The Hg(Ag)FE response of DOX was monitored in the potential range between -0.20 and -0.80 V. For the trace level analysis the method optimization showed that the optimal conditions for the analytical peak with peak potential (E_p) at -0.57 V vs. SCE were: the pH 6.0, the accumulation potential -0.20 V, and the accumulation time 140 s. In the model solutions, DOX was determined in the concentration range of 4.99-59.64 ng mL^-1. The developed SWAdSV method was applied for the determination of DOX in spiked human urine sample. The lowest concentration of DOX of 9.89 ng mL^-1 in voltammetric vessel was determined with the relative standard deviation (RSD) less than 6%. As for the investigated macrolides, they showed reduction signals in fairly negative potential range. During direct cathodic SWV investigations conducted over the potential range from -0.75 V to -2.00 V vs. SCE, either one or two reduction peaks were obtained in the&nbsp; potential range from -1.5 to -1.9 V. For analytical purposes concerning the development of direct cathodic SWV and adsorptive stripping SWV methods the neutral&nbsp; and slightly alkaline media were suitable as pH 7.0 with E_p at -1.67 V vs.&nbsp; SCE for ROX and EES and pH 7.2 and pH 7.4 with E_p at -1.85 V and -1.64 V vs. SCE for AZI and CLA, respectively. Based on the cyclic voltammograms recorded at these pH values, adsorptioncontrolled electrode kinetics process can be proposed for all four investigated compounds. The water suppressed ¹H NMR measurements in the pH range between 6.0 and 10.5 indicated that the macrolide molecules at the optimal analytical conditions are predominantly in protonated form via their tertiary amino groups which supported in all four cases their adsorption on the appropriately polarized Hg(Ag)FE electrode. The optimized direct cathodic SWV methods showed good linearity in concentration ranges 4.81-23.3 &mu;g mL^-1, 4.53-29.8 &mu;g mL^-1, 1.96-28.6&nbsp; &mu;g mL^-1, and 1.48-25.9 &mu;g mL^-1 for AZI, EES, CLA and ROX, respectively. The SW-AdSV methods resulted in the linear responses at lower concentration ranges as 1.0-2.46 &mu;g mL^-1, 0.69- 2.44 &mu;g mL^-1, 0.05-0.99 &mu;g mL^-1 and 0.10-0.99 &mu;g mL^-1, for AZI, EES, CLA and ROX, respectively. The RSD for all developed methods was not higher than 1.5% except the SWV method for AZI with 4.7%. The direct cathodic SWV method was successfully applied for the determination of EES in the pharmaceutical preparation Eritromicin^&reg;, while SW-AdSV was tested in the case of the spiked urine sample and for determination of ROX in pharmaceutical preparation Runac^&reg;. In all above cases, the standard addition method was used. The reliability and accuracy of the above procedures in the case of EES determination in model system and pharmaceutical preparation Eritromicin^&reg; were validated by comparing them with those obtained by means of HPLC-DAD measurements.</p><p>After initial study of 3-dehydro-deoxycholic acid/3-dehydro-deoxycholate by glassy carbon electrode, where the absence of any reduction peak was observed in the Britton-Robinson buffer solutions between pH 5.0 and 11.8 by direct cathodic SWV, a bismuth-film was electrodeposited ex situ on the same glassy carbon electrode surface (BiF-GCE) from the usually used plating solution (0.02 mol L^-1 Bi(NO₃)₃, 1.0 mol L^-1 HCl and 0.5 mol L^-1 KBr) and such prepared film-electrode was applied for the characterization and determination of the the target analyte in alkaline media. The reduction signal of analytical importance was observed only by BiF-GCE in Britton-Robinson buffer solutions with pH values between 9.5 and 11.8 in adsorptive stripping square-wave voltammetry working regime, while in the case of the direct cathodic SWV experimental protocol only a very poor reduction peak was obtained. The optimized experimental conditions for the 3-dehydro-deoxycholate determination consist of the optimized electrode conditioning including the electrochemical cycling of the <em>ex situ </em>prepared BiF-GCE potentials in the potential span between -1.0 and -2.0 V vs. SCE (nearly 15 times) in the Britton-Robinson supporting electrolyte pH 11.8 till the stabilization of the baseline current, and the application of two key parameters of the adsorptive square-wave voltammetric protocol: the accumulation time as 30 s and accumulation potential as -1.0 V vs. SCE. Because of the relative asymmetry of the obtained reduction signals of the target analyte with peak E_p at -1.35 V vs. SCE, which is still present in the case of the SW-AdSV, the quantification of the target analyte was based on the linear correlation between peak area of the reduction signal and its appropriate concentrations, and reached limit of detection is 1.43 &mu;g mL^-1 and with two linear ranges of calibration curve from 4,76 &mu;g mL^-1 to 13.0 &mu;g mL^-1 and from 13,0 &mu;g mL^-1 to 23,1 &mu;g mL^-1 for the development of analytical method. The RSD of the method&nbsp; was 3.22%. Additional experiments were performed applying GCE with rectangular form (area 35.32 cm²) modified with ex situ prepared bismuth-film for the electrolysis of the target analyte which was performed at the potential -1.55 V (nearly the peak maxima of the target analyte) vs. SCE. The solution of interest was sampled at the beginning of the experiment, after 2.5 h and after 4.5 h of treatment. Such samples were analysed by simply water suppressing ¹H NMR measurements in the buffered solution at pH 11.8. It can be assumed that during electrolysis of 3-dehydrodeoxycholate the reduction of the keto group present in the structure of the target analyte can be occurred.</p><p>Driven by earlier literature data about the fact that some of the target macrolide antibiotics as e.g. azithromycin showed oxidation behavior at a carbon paste and gold working electrodes detailed characterization and determination of four target macrolide antibiotics were performed on classical carbon paste electrode (CPE) constituted only from graphite powder and paraffin oil with optimized direct anodic SWV methods. In the cases of EES and AZI differential pulse voltammetric (DPV) methods were tested for the same purpose as well. The key parameter in the case of the development of the analytical voltammetric methods is the selection of the pH value of the supporting electrolyte where the shape/simmetry and intensity of the oxidation peak were the criteria. As the appropriate pH value for determination of EES by SWV method the pH 8.0 was selected with E_p at 0.83 V vs. SCE while in the case of the DPV method the pH 12.0 with E_p at 0.55 V vs. SCE was the most suitable for analytical&nbsp; purpose. As for AZI determination, in the case of both SWV and DPV methods the pH 7.0 was the most appropriate supporting electrolyte with the Ep of analytical signal at 0.85 V and 0.80 V vs. SCE, respectively, while in the case of CLA and ROX which were investigated only with SWV method for the analytical purposes the pH 12.0 was the most suitable with E_p at 0.65 V and at 0.63 V vs. SCE. The obtained detection limits applying the bare CPE and the direct anodic SWV are mainly&nbsp; in submicrogram concentration range as 0.17 &mu;g mL^-1; 0.32 &mu;g mL^-1 and 0.30 &mu;g mL^-1 for EES, AZI, and ROX and in the low microgram concentration range as 1.43 &mu;g mL^-1 for the CLA, respectively. The developed method succesfully tested for the determination of ROX in the commercial formulation, Runac^&reg; tablet. In the case of the optimized DPV methods the obtained detection limits for EES and AZI are in the low microgram concentration range 1.03 &mu;g mL^-1 and 1.53 &mu;g mL^-1, respectively. For the improvement of the sensitivity for AZI the DPV method was tested in combination with a&nbsp; CPE working electrode surface modified with gold nanoparticles with diameter of 10 nm (Au-CPE) and reached the limit of detection was 0.95 &mu;g mL^-1 at E_p of 0.80 V vs. SCE. The RSD of the method in the case of the Au-CPE is 3.5% while in the case of the native CPE 6.0%. The linearity of the Au-CPE based analytical method is twice wider then it is case with the bare CPE applying protocol.</p><p>Based on the obtained results it can be conclude that the appropriate combination of the optimized voltammetric pulse techniques and the environmentally friendly and easy to use working electrodes as Hg(Ag)FE, BiF-GCE and CPE together with Au-CPE resulted in the development of reliable analytical method either in the oxidation or reduction studies, often allowing trace level determination of pharmacological importance target analytes in simpler and in some case complexes systems.</p>

Availability of digital cameras in various forms and user-friendly image editing softwares has enabled people to create and manipulate digital images easily. While image editing can be used for enhancing the quality of the images, it can also be used to tamper the images for malicious purposes. In this context, it is important to question the originality of digital images. Digital image forensics deals with the development of algorithms and systems to detect tampering in digital images. This thesis presents some simple algorithms which can be used to detect tampering in digital images. Out of the various kinds of image forgeries possible, the discussion is restricted to photo compositing (Photo montaging) and copy-paste forgeries. While creating photomontage, it is very likely that one of the images needs to be resampled and hence there will be an inconsistency in some of its underlying characteristics. So, detection of resampling in an image will give a clue to decide whether the image is tampered or not. Two pixel domain techniques to detect resampling have been presented. The rest of them exploits the property of periodic zeros that occur in the second divergences due to interpolation during resembling. It requires a special condition on the resembling factor to be met. The second technique is based on the periodic zero-crossings that occur in the second divergences, which does not require any special condition on the resembling factor. It has been noted that this is an important property of revamping and hence the decay of this technique against mild counter attacks such as JPEG compression and additive noise has been studied. This property has been repeatedly used throughout this thesis. It is a well known fact that interpolation is essentially low-pass filtering. In case of photomontage image which consists of resample and non resample portions, there will be an in consistency in the high-frequency content of the image. This can be demonstrated by a simple high-pass filtering of the image. This fact has also been exploited to detect photomontaging. One approach involves performing block wise DCT and reconstructing the image using only a few high-frequency coercions. Another elegant approach is to decompose the image using wavelets and reconstruct the image using only the diagonal detail coefficients. In both the cases mere visual inspection will reveal the forgery. The second part of the thesis is related to tamper detection in colour filter array (CFA) interpolated images. Digital cameras employ Bayer filters to efficiently capture the RGB components of an image. The output of Bayer filter are sub-sampled versions of R, G and B components and they are completed by using demosaicing algorithms. It has been shown that demos icing of the color components is equivalent to resembling the image by a factor of two. Hence, CFA interpolated images contain periodic zero-crossings in its second differences. Experimental demonstration of the presence of periodic zero-crossings in images captured using four digital cameras of deferent brands has been done. When such an image is tampered, these periodic zero-crossings are destroyed and hence the tampering can be detected. The utility of zero-crossings in detecting various kinds of forgeries on CFA interpolated images has been discussed. The next part of the thesis is a technique to detect copy-paste forgery in images. Generally, while an object or a portion if an image has to be erased from an image, the easiest way to do it is to copy a portion of background from the same image and paste it over the object. In such a case, there are two pixel wise identical regions in the same image, which when detected can serve as a clue of tampering. The use of Scale-Invariant-Feature-Transform (SIFT) in detecting this kind of forgery has been studied. Also certain modifications that can to be done to the image in order to get the SIFT working effectively has been proposed. Throughout the thesis, the importance of human intervention in making the final decision about the authenticity of an image has been highlighted and it has been concluded that the techniques presented in the thesis can effectively help the decision making process.