The near-threshold behavior of long cracks is studied in this paper using precracked flat dogbone specimens of a commercial aluminum alloy in peak-aged and overaged conditions. After introducing the initial crack in compression precracking, the crack was propagated approximately with the constant range of the stress intensity factor at values just above or below the corresponding threshold values. It was found that there were two major mechanisms which kept the crack from continuous extension. First, the crack front was pinned by primary precipitates. This effect was rather pronounced and lead to significant kinking in the crack front and ductile ridges on the fracture surface. The second mechanism was shear-controlled crack extension of very long cracks with plastic zones ahead of the crack tip, very similar to stage-I small cracks. Interaction with primary precipitates deflected the shear-controlled cracks but did not change the crack extension mode.

This dissertation demonstrates the first of its kind distributed magnetic field sensor based on a fiber optic distributed acoustic sensing (DAS) scheme. Ferromagnetic nickel and Metglas® were dispersed internally within a fiber optic preform and then drawn on an in-house fiber optic draw tower to lengths in the kilometers. Due to the close proximity of the ferromagnetic metals and fiber optic core, the magnetostrictive strain response of the ferromagnetic materials when exposed to a magnetic field would perturbate within the fiber cladding and transfer that strain, internally, to the fiber optic core. Strain resulting from the magnetostrictive effect allows the DAS based sensor to accurately translate strain into readable magnetic field data. Due to the high sensitivity seen in this sensor design, multiparameter sources, acoustic and magnetic fields, were tested and validated and a three dimensional magnetic-field vector sensor was proposed. Numerical analysis of the novel sensor design was first implemented using COMSOL Multiphysics, where inputs such as magnetostrictive element shape, size, distance, and number were first investigated. Upon optimizing system constraints, the sensor design was further modified such that single mode operation was consistent across multiple fiber draws while retaining high strain transfer from the ferromagnetic elements to the fiber optic core. Ferromagnetic material selection was evaluated as a function of the saturation magnetostriction constants and a total of 4 modules were used to fully characterize the complex physics involved in this sensor design. All fabrication and testing were performed in-house using a full scale 3-story fiber draw tower and custom environmental testing stations to imitate naturally occurring events such as magnetic or acoustic point sources. A unique stacking method was used to embed ferromagnetic nickel and Metglas® into a fiber optic preform which when combined with a custom fiber draw process resulted in consistent multi-material fibers drawn to lengths of 1-km. In-house testing facilities included different types of electromagnetic generators, in addition to a soil test bed, and an outdoor test bed which allowed 100 meters of fiber to be tested simultaneously. All tested sensors demonstrated high strain transfer capabilities on the order of 0.01-10 μϵ depending on the materials used, ferromagnetic rod number, and core to metal spacing. Due to the sensitivity of the system the difference between AC and DC was distinct, and directional magnetostriction was studied. Transverse and longitudinal magnetic wave propagation was controlled through a solenoid and rectangular Helmholtz coil, both built in-house. A three-dimensional magnetic field vector sensor was proposed due to the success of the magnetic field sensor, and a design was proposed and initially tested to validate direction as a function of field strength and distance. To summarize, this dissertation explores the first fully distributed magnetic field sensor using DAS based techniques and one of the first multi-material fiber draw processes which can produce consistent single mode fiber up to 1-km. Due to extensive FEA modeling, multiple iterations of the magnetic sensor were fully characterized and an equation describing the relationship between sensor design and strain transfer has been created and validated experimentally. Multi-parameter tests including acoustic and magnetic fields were implemented and an algorithm was developed to separate the mixed signals. Finally, a test was performed to demonstrate the feasibility of sensing magnetic fields directionally. Cumulative results demonstrate a high-quality sensor alternative to current designs which may surpass other magnetic sensors due to innate multi-parameter capabilities, in addition to the inexpensive production cost and extremely long operating lengths. / Doctor of Philosophy / This dissertation demonstrates the first of its kind distributed magnetic field sensor based on a fiber optic distributed acoustic sensing (DAS) scheme. Ferromagnetic nickel and Metglas® were dispersed internally within a fiber optic preform and then drawn on an in-house fiber optic draw tower to lengths in the kilometers. Due to the close proximity of the ferromagnetic metals and fiber optic core, the magnetostrictive strain response of the ferromagnetic materials when exposed to a magnetic field would perturbate within the fiber cladding and transfer that strain, internally, to the fiber optic core. Strain resulting from the magnetostrictive effect allows the DAS based sensor to accurately translate strain into readable magnetic field data. Due to the high sensitivity seen in this sensor design, multiparameter sources, acoustic and magnetic fields, were tested and validated and a three dimensional magnetic-field vector sensor was proposed. Numerical evaluation of the sensing structure was perused before experimental testing using COMSOL Multiphysics. Experimental and numerical evaluations were compared and showed a high degree of certainty which allowed expedited design modifications. Sensor characterization included scanning electron microscopy, and electron diffraction spectroscopy, which provided insight into material composition and fiber polishing quality. Due to the high-quality results attained in the combined acoustic and magnetic field tests, a final design was proposed to gather magnetic field data as a vector, showing both magnitude and direction. The 3D magnetic field vector sensor was partially validated based on a test which compared intensity with distance and a design and methodology was proposed to fully test and characterize this design. To summarize, a novel magnetic field sensor, capable of multi-parameter sensing, was proposed and tested experimentally and numerically resulting in a robust and highly sensitive design. The work presented here provides some of the first insights into multi-material fiber fabrication, an equation which provides an estimated relationship between magnetostrictive strain transfer onto a fiber optic core and the perceived DAS based sensor results, as well as a first of its kind multi-parameter distributed acoustic and magnetic field sensor.

The Common bed bug, Cimex lectularius L., suddenly reappeared in developed countries in the past 15 years. The factor contributing to the sudden resurgence of the bed bugs is insecticide resistance. In this study, we investigated the mechanisms of reduced cuticular penetration type insecticide resistance in bed bugs. First, we determined and compared the lethal dosage (LD50) of a pyrethroid insecticide using topical and injection application. The resistant strain not only had significantly greater resistance ratios, but also demonstrated significantly greater penetration resistance ratios. This provided the evidence of the reduced cuticular penetration in bed bugs. Second, we determined the levels of gene transcription (CPR-type cuticle protein genes) using real-time quantitative polymerase chain reaction (qRT-PCR). We identified 62 putative bed bug cuticle protein-encoding contigs based on the presence of the Chitin-binding 4 (CB4) domain. Based on the qRT-PCR analysis of the mRNAs, we found many of the genes were up-regulated in the resistant strain suggesting thickening of the cuticle or increasing the cuticular proteins might be involved in the reduced cuticular penetration. Third, we identified and described the cuticular proteins using the matrix-assisted laser desorption/ionization (MALDI) time-of-flight/time-of-flight (TOF/TOF) high-resolution tandem mass spectrometry (MALDI-TOF/TOF). The total of 265 peptides were identified, among which 206 belonged to one of 50 confidently identified proteins. We identified the CPRL, CPF, CPFL, TWDL, and CPAP1 family proteins. The profile of the cuticular proteins between the resistant and the susceptible strains bed bugs were almost identical. Fourth, we determined and compared the cuticular thickness using Scanning Electron Microscopy (SEM). We found statistical differences of the cuticular thickness among different strains (populations), however, correlation between the levels of insecticide resistance and cuticular thickness were not found. Finally, we identified and described bed bug cuticular hydrocarbon profiles using Gas-Chromatography and Mass-Spectrometry (GC-MS). The total of 87 compounds in addition to n-alkanes were extracted and identified. There were no correlation found with the concentration and the levels of insecticide resistance. However, several additional compounds exhibited the correlation between the concentration of the compounds and the levels of insecticide resistance. Overall, we found three lines of evidence to support reduced cuticular penetration as a mechanism of insecticide resistance in some bed bug populations. This study provides additional evidence of the reduced cuticular penetration type resistance in bed bugs. / Ph. D.

O objetivo deste trabalho foi avaliar a influência de dois diferentes ambientes de sinterização (vácuo e argônio) sobre a resistência da união metaloceramica (RUMC) envolvendo diferentes ligas de metais básicos (Co-Cr e Ni-Cr) e uma porcelana odontológica, através do teste de flexão de três pontos, conforme preconizado pela ISO 9693:2012. As ligas estudadas foram Co-Cr: Remanium e Keragen e Ni-Cr: Verabond II e uma liga experimental “SR” . Foram obtidos 80 corpos de prova em forma tiras metálicas medindo 25 X 0,5 X 5 mm. Para esse ensaio, portanto, o número de corpos de prova foi o produto de 4 ligas x 2 condições de atmosfera de sinterização x 10 repetições. A parte metálica de todos os corpos de prova após a fundição foram usinados e jateados com óxido de alumínio (150μm) e a seguir tratados como preconizado pelo fabricante. O corpo cerâmico, com o auxílio de uma matriz, foi confeccionado na área central da tira, 8,0 X 3,0mm, apresentando 1,1mm de espessura, sendo 10 corpos de prova em cada ambiente de sinterização para cada tipo de liga. Os corpos de prova obtidos foram submetidos aos testes de flexão de três pontos na Máquina de Ensaios Mecânicos (EMIC) com velocidade de 1.0mm/min. para determinação da RUMC. Os valores da carga de ruptura obtidos em quilograma-força (Kgf) foram convertidos para Newton (N) e a partir disso foi calculado o valor da RUMC para cada corpo de prova, considerando o coeficiente de elasticidade de cada liga e a espessura exata de cada corpo de prova. Os dados obtidos (MPa) foram submetidos à análise estatística (ANOVA) e Bonferroni. A Análise de Variância indicou diferença estatisticamente significante para os fatores de variação ambiente (P=0,00), liga (P=0,009) e entre as interações ambiente de sinterização e liga (P=0,000). Na sinterização a vácuo as ligas Keragen, SR e Verabond II apresentaram maiores valores de RUMC do que o argônio. Para a liga Remanium, não houve diferença entre a sinterização em argônio e a sinterização a vácuo. Dentre os grupos sinterizados no argônio não houve diferença estatisticamente significante entre as ligas. Entretanto, no vácuo a liga Remanium apresentou menor valor de RUMC do que as demais ligas, que não apresentaram diferença entre si. Os corpos de prova, após os ensaios de flexão, foram submetidos a análise em microscopia optica, MEV e EDS para avaliar e registrar tipo de falha que sofreram. De acordo com a MO, houve predomínio de fraturas mistas. Os corpos de prova de Co-Cr (Remanium e Keragen), independende do ambiente de sinterização, apresentaram uma fina camada de óxido no corpo cerâmico, o que foi comprovado pelo EDS, com maior presença de íons Cr nessas regiões, já os grupos SR e Verabond II, apresentaram maior quantidade de opaco aderido em suas tiras metálicas. A MEV comprovou os achados da MO, onde foi possível encontrar grandes ilhas de material cerâmico nas ligas de Ni-Cr. A sinterização em argônio influenciou negativamente a RUMC dos pares metalocerâmicos confeccionados em Ni-Cr e na liga Keragem / The aim of this study was to evaluate the influence of two different firing atmosphere (vacuum and argon) on the metalceramic bond strength (MCBS) involving different base metal alloys (Co-Cr and Ni-Cr) and a dental porcelain through three-point bending test, as recommended by ISO 9693: 2012. Co-Cr alloys studied were: Remanium and Keragen and Ni-Cr: Verabond II and an experimental alloy \"SR\". 80 specimens were obtained in metallic form strips measuring 25X0.5 X 5.0 mm. For this test, therefore, the number of specimens was the product of 4 x 2 alloy sintering atmosphere conditions x 10 replicates. The metal portion of all specimens were machined after casting and sandblasted with aluminum oxide (100μm) and then treated as recommended by the manufacturer. By using a matrix, the ceramic body was made in the central area of the strip, 8.0 x 3.0 mm, it was made 1.1 mm thickness, 10 specimens in each sintering environment for each type of alloy. The specimens obtained were tested for three-point bending in a universal testing machine with a speed of 1.0mm / min. to determine MCBS. The values of the tensile strength obtained in kilogramforce (kgf) were converted into Newton (N) and from this the value of MCBS for each specimen was calculated, considering the coefficient of elasticity of each league and the exact thickness of each specimen. The data (MPa) were subjected to statistical analysis (ANOVA) and Bonferroni. The analysis of variance indicated statistically significant difference for the environment factors of firing atmosphere (P = 0.00) and alloy (P = 0.009). There was a statistically significant difference in the interaction factors for firing atmosphere x alloy (P = 0.000). In the vacuum Keragen, SR and Verabond II alloys showed higher MCBS than argon. To Remanium, there was no difference between the sintering in argon and vacuum. Among the groups sintered in argon there was no statistically significant difference between the alloys. However, the vacuum Remanium showed the lowest RUMC than other alloys, which showed no difference between them. The specimens after the bending tests, were subjected to analysis in optical microscopy, SEM and EDS to assess and record type of failure they suffered. According to the MO was predominantly mixed fractures. Specimens of Co-Cr (Remanium and Keragen) independende the atmosphere firing, showed a thin oxide layer on the ceramic body, which was confirmed by EDS, with greater presence of Cr in these regions, since the SR groups and Verabond II, presented more opaque stuck in their metal strips. SEM confirmed the findings of MO, where it was possible to find large islands of ceramic material in Ni-Cr alloys. The sintering in argon negatively influenced MCBS metalceramic of pairs made of Ni-Cr alloy and Keragem

O objetivo deste trabalho foi avaliar o efeito do ambiente de sinterização vácuo e argônio na resistência de união (RUMC) de cerâmicas às ligas de Ni-Cr (Fit Cast SB), Co-Cr (Star Loy C) e titânio comercialmente puro (Tritan). A partir de uma matriz de teflon, foram obtidos 60 padrões de resina/cera em forma de cilindro, com 8 mm de comprimento e 5 mm de diâmetro. Os padrões foram incluídos e os anéis foram levados ao forno e submetidos a ciclos térmicos para a expansão do revestimento. Em seguida, os anéis para fundição em Ni-Cr e Co-Cr foram levados à máquina de fundição por indução eletrônica. Os anéis referentes ao titânio foram levados à máquina de fundição por arco voltaico. Após resfriamento dos anéis, as fundições foram desincluídas e jateadas com óxido de alumínio (100 μm). Depois de recortados dos canais de alimentação, os cilindros metálicos foram preparados para aplicação da cerâmica. Em seguida, foi realizada a aplicação e sinterização da cerâmica à vácuo ou em argônio. Para as ligas alternativas, foi utilizada a cerâmica IPS Classic V e para o titânio, a Triceram. Na sequência, os cilindros compostos pelo metal e disco cerâmico (5 mm de diâmetro e 2 mm de espessura) (n=10) foram submetidos aos ensaios de RUMC por cisalhamento na máquina de ensaios universais com célula de carga de 500 Kg e velocidade do travessão móvel de 0,5 mm/min. Após os ensaios, foram realizadas análises das fraturas por meio de microscopia óptica (MO) (15X) e microscopia eletrônica de varredura (MEV). Os dados de RUMC (MPa) obtidos foram analisados estatisticamente pelos testes ANOVA e Tukey (α=0,05). Os resultados demonstraram que a sinterização à vácuo propiciou obtenção de maiores valores (MPa) de RUMC (76,58) que a sinterização em argônio (51,31). Quanto às ligas avaliadas, as de Ni-Cr e Co-Cr apresentaram maiores valores de RUMC (71,32 e 71,28, respectivamente) que o titânio cp (49,23); sendo que entre elas não houve diferença estatística. Não houve interação entre os fatores avaliados. De acordo com a MO, houve predomínio de fraturas mistas. Segundo a MEV, os espécimes de Ni-Cr e titânio sinterizados a vácuo apresentaram maior rugosidade de superfície do que os sinterizados em argônio. Para a liga de Co-Cr não houve diferença na topografia de superfície. A sinterização em argônio influenciou negativamente a RUMC dos pares metalocerâmicos analisados. / The aim of this study was to evaluate the effect of firing atmospheres: vacuum and argon on the bond strength of ceramic to Ni-Cr (Fit Cast SB), Co-Cr (Star Loy C) and commercially pure titanium (Tritan) alloys. 60 wax/acrylic resin cylinder patterns (8 mm high and 5 mm in diameter) were prepared on a plastic custom mold for metalceramic bond strength (MCBS) test. The patterns were invested in phosphated investment and manipulated on vacuum. The rings were placed in a furnace to burn out patterns and thermally expand the molds. Then, the rings of Ni-Cr and Co-Cr were placed in an electronic machine to cast. The rings related to titanium were positioned in the casting machine with a voltaic arc. After the rings have cooled, the castings were divested manually and abraded with aluminum oxide particles (100 μm). Then, the cylinders were prepared for applying of the ceramic veneering disks. The ceramic was applied and fired in vacuum and argon atmospheres. IPS-Classic ceramic was used for alternative alloys and for titanium, Triceram ceramic. Then, the cylinders composed of metal and ceramic disk (5 mm diameter and 2 mm height) (n=10) were submitted to metal-ceramic bond strength (MCBS) shear tests on an universal testing machine with load cell of 500 Kg at a crosshead speed of 0.5 mm/min. After the tests, there were made fracture analysis by optic microscopy (OM) and scanning electron microscopy (SEM). The MCBS data (MPa) were statistically analyzed by the ANOVA and Tukey test (α=0.05). The results indicated that the vacuum firing (76.58) promoted higher MCBS values than argon firing (51.31). Among the metals, Ni-Cr and Co-Cr alloys presented higher MCBS (71.32 e 71.28, respectively) than titanium (49.23); between two base alloys there was no statistical difference. There was no interaction between the evaluated factors. According to MO analysis, there was predominance of mixed fractures. According SEM, the Ni-Cr and titanium specimens submitted to vacuum presented higher surface roughness than the specimens submitted to argon. For Co-Cr, there was no difference of surface topography. The argon firing influenced negatively the MCBS of metal-ceramic evaluated pairs.

O objetivo deste trabalho foi avaliar a influência de dois diferentes ambientes de sinterização (vácuo e argônio) sobre a resistência da união metaloceramica (RUMC) envolvendo diferentes ligas de metais básicos (Co-Cr e Ni-Cr) e uma porcelana odontológica, através do teste de flexão de três pontos, conforme preconizado pela ISO 9693:2012. As ligas estudadas foram Co-Cr: Remanium e Keragen e Ni-Cr: Verabond II e uma liga experimental “SR” . Foram obtidos 80 corpos de prova em forma tiras metálicas medindo 25 X 0,5 X 5 mm. Para esse ensaio, portanto, o número de corpos de prova foi o produto de 4 ligas x 2 condições de atmosfera de sinterização x 10 repetições. A parte metálica de todos os corpos de prova após a fundição foram usinados e jateados com óxido de alumínio (150μm) e a seguir tratados como preconizado pelo fabricante. O corpo cerâmico, com o auxílio de uma matriz, foi confeccionado na área central da tira, 8,0 X 3,0mm, apresentando 1,1mm de espessura, sendo 10 corpos de prova em cada ambiente de sinterização para cada tipo de liga. Os corpos de prova obtidos foram submetidos aos testes de flexão de três pontos na Máquina de Ensaios Mecânicos (EMIC) com velocidade de 1.0mm/min. para determinação da RUMC. Os valores da carga de ruptura obtidos em quilograma-força (Kgf) foram convertidos para Newton (N) e a partir disso foi calculado o valor da RUMC para cada corpo de prova, considerando o coeficiente de elasticidade de cada liga e a espessura exata de cada corpo de prova. Os dados obtidos (MPa) foram submetidos à análise estatística (ANOVA) e Bonferroni. A Análise de Variância indicou diferença estatisticamente significante para os fatores de variação ambiente (P=0,00), liga (P=0,009) e entre as interações ambiente de sinterização e liga (P=0,000). Na sinterização a vácuo as ligas Keragen, SR e Verabond II apresentaram maiores valores de RUMC do que o argônio. Para a liga Remanium, não houve diferença entre a sinterização em argônio e a sinterização a vácuo. Dentre os grupos sinterizados no argônio não houve diferença estatisticamente significante entre as ligas. Entretanto, no vácuo a liga Remanium apresentou menor valor de RUMC do que as demais ligas, que não apresentaram diferença entre si. Os corpos de prova, após os ensaios de flexão, foram submetidos a análise em microscopia optica, MEV e EDS para avaliar e registrar tipo de falha que sofreram. De acordo com a MO, houve predomínio de fraturas mistas. Os corpos de prova de Co-Cr (Remanium e Keragen), independende do ambiente de sinterização, apresentaram uma fina camada de óxido no corpo cerâmico, o que foi comprovado pelo EDS, com maior presença de íons Cr nessas regiões, já os grupos SR e Verabond II, apresentaram maior quantidade de opaco aderido em suas tiras metálicas. A MEV comprovou os achados da MO, onde foi possível encontrar grandes ilhas de material cerâmico nas ligas de Ni-Cr. A sinterização em argônio influenciou negativamente a RUMC dos pares metalocerâmicos confeccionados em Ni-Cr e na liga Keragem / The aim of this study was to evaluate the influence of two different firing atmosphere (vacuum and argon) on the metalceramic bond strength (MCBS) involving different base metal alloys (Co-Cr and Ni-Cr) and a dental porcelain through three-point bending test, as recommended by ISO 9693: 2012. Co-Cr alloys studied were: Remanium and Keragen and Ni-Cr: Verabond II and an experimental alloy \"SR\". 80 specimens were obtained in metallic form strips measuring 25X0.5 X 5.0 mm. For this test, therefore, the number of specimens was the product of 4 x 2 alloy sintering atmosphere conditions x 10 replicates. The metal portion of all specimens were machined after casting and sandblasted with aluminum oxide (100μm) and then treated as recommended by the manufacturer. By using a matrix, the ceramic body was made in the central area of the strip, 8.0 x 3.0 mm, it was made 1.1 mm thickness, 10 specimens in each sintering environment for each type of alloy. The specimens obtained were tested for three-point bending in a universal testing machine with a speed of 1.0mm / min. to determine MCBS. The values of the tensile strength obtained in kilogramforce (kgf) were converted into Newton (N) and from this the value of MCBS for each specimen was calculated, considering the coefficient of elasticity of each league and the exact thickness of each specimen. The data (MPa) were subjected to statistical analysis (ANOVA) and Bonferroni. The analysis of variance indicated statistically significant difference for the environment factors of firing atmosphere (P = 0.00) and alloy (P = 0.009). There was a statistically significant difference in the interaction factors for firing atmosphere x alloy (P = 0.000). In the vacuum Keragen, SR and Verabond II alloys showed higher MCBS than argon. To Remanium, there was no difference between the sintering in argon and vacuum. Among the groups sintered in argon there was no statistically significant difference between the alloys. However, the vacuum Remanium showed the lowest RUMC than other alloys, which showed no difference between them. The specimens after the bending tests, were subjected to analysis in optical microscopy, SEM and EDS to assess and record type of failure they suffered. According to the MO was predominantly mixed fractures. Specimens of Co-Cr (Remanium and Keragen) independende the atmosphere firing, showed a thin oxide layer on the ceramic body, which was confirmed by EDS, with greater presence of Cr in these regions, since the SR groups and Verabond II, presented more opaque stuck in their metal strips. SEM confirmed the findings of MO, where it was possible to find large islands of ceramic material in Ni-Cr alloys. The sintering in argon negatively influenced MCBS metalceramic of pairs made of Ni-Cr alloy and Keragem

<p>The main hypothesis in this study is the development of a nanocomposite mediated amperometric biosensor for detection of hydrogen peroxide. The aim is to combine the electrochemical properties of both polyaniline and ferrocenium hexafluorophosphate into highly conductive nano composites capable of exhibiting electrochemistry in non acidic media / shuttling electrons between HRP and GCE for biosensor applications.</p>

Imitation of archeological artifacts or replacing the authentic ones with fake replicates is a universal problem / it is particularly important in Turkey for historical metal objects. Traditionally used visual inspection methods alone are not sufficient for the solution of contemporary problems. In this study, chemical characterization has been used to determine the differences between the authentic and fake objects. The non-destructive analyses were carried out by Portable X-ray Fluorescence Spectrometry (P-XRF). Silver Roman Coins (27 B.C. to 244 A.D.) were the objects handled in this research. In particular the concentrations of Zr, Pt, Pb and Bi were used for differentiation / it has been observed that the concentrations have different trends in the authentic and fake silver coins. In authentic coins the average Pb concentration was found to be 0.77%, while this value was 0.055% for the fake ones. Bi could be determined in 86% of the authentic coins while it could not be detected in any fake coin. It has been generally observed that the silver and copper concentrations could not be utilized in authenticity tests. Another approach was the use of Line Scanning Electron Microscopy-Energy Dispersive X-Ray Fluorescence Spectrometry (LSEM-EDX). Using LSEM-EDX technique, it was observed that the concentration changes near the interface between the matrix and the copper-rich locations exhibits difference behaviors for the authentic and fake objects. This difference is originated by the fact that a newly formed copper amalgam contains copper-rich phases while with extended time concentration changes at interfaces become more gradual or not detectable. Pearson correlation was used in order to elucidate the relations between the element concentrations determined by P-XRF. In order to see whether the authentic and silver fake coins can form separate groups, dendograms have been constructed utilizing SPSS 16.0 software and Euclidian Square Distance method. It has been observed that the authentic and fake coins can be successfully grouped when the proper statistical choices are used. It has been observed that these groups have significant differences using t-test. The selected and used technology is proposed for use by museums and entities keeping archaeological collections in order to prevent forgeries.

<p>The main hypothesis in this study is the development of a nanocomposite mediated amperometric biosensor for detection of hydrogen peroxide. The aim is to combine the electrochemical properties of both polyaniline and ferrocenium hexafluorophosphate into highly conductive nano composites capable of exhibiting electrochemistry in non acidic media / shuttling electrons between HRP and GCE for biosensor applications.</p>

Incorporation of monoacetylferrocene to the sulfonated polystyrene ionomers imparted some changes in the properties of sulfonated polystyrene. Sulfonation was carried out by acetic anhydride and concentrated sulphuric acid. The sulfonation reaction and the degree of sulfonation were determined by analytical titration and adiabatic bomb calorimeter . For this purpose, sulfonated polystyrene (SPS) samples with varying percentages of sulfonation were prepared between 0.85% and 6.51%. Monoacetyl ferrocene was used in equivalent amount of sulfonation through addition procedure. FTIR Spectroscopy was one of the major techniques used to support the successful addition of AcFe to the SPS samples. Altering the sulfonation degree did not change the characteristic peak positions, but increased the peak intensities with increasing the degrees of sulfonation. Mechanical properties of resultant polymers were investigated. As a result, elastic modulus of polymers decreased by the amount of monoacetylferrocene. Thermal characteristic were found by Differential Scanning Calorimeter (DSC). Thermal analysis revealed that sulfonated polystyrene samples after addition of monoacetylferrocene displayed lower values of Tg. Microscopic analysis were made by Scanning Electron Microscopy (SEM) and single phase for each sample was observed. Besides, energy dispersed micro analysis showed an increase in the intensity of the iron (II) peaks that is related to the amount of monoacetylferrocene added to the SPS samples. Flame retardancy for each polymer was also examined and found that addition of monoacetylferrocene to sulfonated polystyrene does not change the Limiting Oxygen Index value (LOI)(17). However, LOI value for polystyrene is 18.