Dissertations / Theses on the topic 'High sensitivity measurements'

Low level counting techniques are a powerful tools in many different fields including biological and chemical tracer studies, archaeological and geological dating, investigation of natural and induced radioactivities and the study of fundamental particles physics. Since they play a crucial role in many applications, developments are continuously pursue to improve the extreme sensitivity typical of these techniques. The fundamental request of low level counting techniques is the capability to detect feeble signals, characterized by low counting rates, above the background composed of spurious counts; they thus have the capability to measure very low activities of natural and artificial radionuclides. During my PhD work I have focused on two main applications using low level counting systems: the search of rare physics events and the environmental monitoring. Both the studied systems use γ spectroscopy with High Purity Germanium detectors (HPGe). This technique is one of the most sensitive, it exploits the excellent energy resolution typical of such detectors and their low intrinsic background. The first system is composed of two n-type HPGe GMX 100-95 in Low Background configuration, they have been designed with radiopure selected materials to reach an intrinsic background as low as possible. This work has brought to a unique configuration associated to an electrical cooling system, different from the one that was available on market. Since the two GMX detectors have been conceived to work in coincidence I have optimized the measuring system studying different radionuclide decay schemes to consider the most probable coincidences between the γ -rays emitted during the decay of the isotope under study. A dedicated data acquisition has been developed with particular attention to the co- incidence detection efficiency. Furthermore I have developed the analysis software to For some rare physics events experiments the only way to enhance the sensitivity is the background reduction; for this purpose all the materials of the experimental facility should be selected as radiopure as possible. The development and optimization of the low background system composed of the two GMX detectors, working in coincidence, can select suitable materials through the measurement of very low radionuclide concentrations. The other system I have worked on is a Broad Energy Germanium (BEGe5030) in low background configuration. This detector can register with excellent energy resolution and high efficiency a wide energy spectrum, from 3 keV up to 3 MeV, thanks to some of its peculiar features. The thin dead layers surrounding the active volume and the thin entrance window on its top are responsible for its capability to detect very low energy radiations. I have optimized this system using Monte Carlo simulations to detect low contamina- tions of radionuclides in several samples. In particular in the last century, the environmental monitoring has became an impor- tant aspect of radio-protection; nuclear tests, nuclear accidents, wastes and fall-out in general can release a large quantity of radionuclides. Since toxicity and radioactivity of these contaminations are dangerous it is mandatory an environmental monitoring at the area of interest. Plutonium isotopes significantly contribute to the contamination due to nuclear fall- out events in environment; since they are very toxic it is important to quickly monitor a large number of samples in the area of interest. Using the BEGe I have developed a quick and sensitive method to detect Plutonium isotopes concentration in environmental samples through the detection of the X-rays emitted during their decays. This result is a very important improvement in Plutonium detection for monitoring measurements since the counting methods commonly used are characterized by long measuring and sample treatments time.

The objective of this work is to use MOSFET dosimeters to accurately measure surface dose delivered during CT examinations in various scanning conditions. To achieve this, the behaviour of MOSFETs under kilovoltage x-ray irradiation first needed to be investigated. A dose-to-dose reproducibility of 4.5%, and a mean change in sensitivity response of 10.4% with accumulated dose were measured. A Monte Carlo model of the x-ray source of a PQ5000 CT simulator was built and validated in order to investigate the MOSFET response characteristics and perform dose calculations. An over-response of 10% was observed when the beam energy was decreased from 140 to 80 kVp, and a slight anisotropy of 8.5% from the mean value over 360º was observed. The dosimeters were calibrated on a solid water phantom using a method involving MC surface dose calculations. Good agreement was found between measurements and simulations of surface dose on a cylindrical PMMA phantom for a stationary tube technique, single axial scan and multiple contiguous axial scans, with generally less than 7.5% discrepancies. Film and MOSFET measurements were then performed for helical adult brain scan parameters using different pitch and collimator settings. The use of five MOSFETs combined in a linear array was found to be suitable to accurately measure surface dose in helical scans for almost all pitch and collimation combinations.

The development of an experimental apparatus to produce Bose-Einstein condensates (BECs) of 87Rb atoms and their application to magnetometry are discussed. Optical detection of atomic Larmor precession is a widely explored method for high-sensitivity measurements of magnetic fields. In this context, short laser/atom interaction time, atomic thermal diffusion and decoherence effects are among the main limitations. In this thesis, we overcome such problems by using spin-polarised 87Rb ultra-cold atoms as the sensing element. After the atoms are polarised, a resonant pulse of radio-frequency excites Larmor precession, which is sensitive to external magnetic fields. By measuring the perturbations of the radio-frequency induced spin precession, information on the magnetic fields of interest. This is achieved by monitoring the polarisation plane’s rotation of a linearly polarised resonant laser probe. In the first part of this thesis, the building and optimisation of a laser-cooling set up to obtain a BEC in a hybrid trap is reported. In order to achieve the Phase Space Density (PSD) required for BEC, several different stages of trapping and cooling are necessary. Each phase has been implemented and optimised. The first step consists in the magneto-optical trap (MOT). Here a velocity dependent damping force and a spatially dependent confining force give the largest changes in PSD. Then atoms are loaded into a hybrid trap obtained by overlapping a quadrupole magnetic potential and a far detuned optical crossed dipole trap. The final stage for the condensation consists of forced evaporative cooling, both via magnetic and optical evaporation. In the second part of the thesis, a general overview of the principles of optical atomic magnetometry is provided and the advantages of using ultra-cold atoms with respect to conventional thermal vapours are discussed. The implementation, operation and a preliminary characterisation of the ultra-cold atom magnetometer are described along with the preliminary results collected. Finally, a plan for future improvements of its sensitivity is presented.

2011 - 2012
Earth's surface and interior continuously deform as a result of geological and geophys- ical processes. To study these phenomena and to understand better the rheological properties of the Earth, measurements of Earth's deformation become of fundamental importance, providing a critical link between Earth's structure and dynamics, also in order to optimize the response to natural hazards and identify potential risk areas. The study of crustal deformation is a complex but very important research topic that encompasses several scienti c disciplines, including di erential geometry, theory of elas- ticity, geodynamics and physics in general. The use of di erent kind of geodetic data to study geodynamic phenomena became increasingly important, playing a key role in the knowledge of their temporal and mag- nitude variations at many di erent spatial and time scales. These measurements provide signi cant constraints on the changes in Earth's lithosphere and processes that cause them, like for example movements of magma, changes in strain before, during, and after earthquakes, motion of ice sheets. Yet even today, large portions of the Earth are infrequently monitored, or not at all. Deformation can be measured in several ways, as relative movement of points on the Earth's surface, through measurements of strain and tilt, or by GPS (Global Position- ing System), VLBI (Very Long Base Interferometry) and SLR (Satellite Laser Ranging) measurements. Among the di erent types of instruments, the laser strainmeters (or in- terferometers), measuring the displacement between two points away from a few meters to over a kilometer, are characterized by very high accuracy and long-term stability, necessary to investigate processes of crustal deformation. The analysis of interferomet- ric data allows to study both local and global geodynamic phenomena in a broad band of frequencies. This thesis introduces results related to some analysis of data recorded by two laser interferometers installed at Gran Sasso (Italy) Underground Laboratories and describes the installation of two new laser interferometers in the Canfranc (Spain) Underground Laboratory, at the end of August 2011, with the analysis of their rst sequences. In the rst chapter some general concepts about strain, crustal deformation and their measurements are introduced. The study of the deformation on the Earth's surface improved in the last fty years, changing from mostly descriptive and qualitative to more quantitative. The state and magnitude of the stress in the Earth's lithosphere, and thus of the deformation, play an important role on various geophysical problems, such as the plate mechanisms, energy budget of the Earth, earthquake mechanism and crustal movements. In Chapter 2 there is a description of the Earth's tidal deformation. The body tides, due to a direct e ect of gravitational attraction from the Sun, Moon and other objects, can be modeled very accurately. In addition, there is a part of deformation, known as ocean loading, arising from the mass uctuations of the oceans. These last is also rather well understood, but the modeling of its e ects still needs to be improved. This phenomenon is very signi cant for the interferometric strain sequences because they are clearly dominated by the semidiurnal and diurnal strain tides. Chapter 3 describes the laser interferometry and, in particular, the operating principle of the Gran Sasso (Italy) laser interferometers, which provide very high-sensitivity strain data, by comparing the optical length of a longer measurement arm (about 90 meters in length) and a shorter xed reference arm (about 20 cm in length). Although the interferometers measure strain directly, the presence of cavities, topography, and local inhomogeneities of the crust can modify the strain measurement considerably. Also environmental and anthropic e ects appear as anomalous or noise signals in a broad frequency range, which includes for example the Earth tides. It is necessary to take some or all these possible e ects into account, depending on the phenomenon studied. In Chapter 4 data produced by Gran Sasso interferometers, rst alone and then to- gether with those produced by a third laser interferometer installed in Baksan (Russia) Underground Laboratory, are used to estimate the Free Core Nutation (FCN) param- eters. Even if tidal signal-to-noise ratio for strain is usually lower than for gravity, the analysis of strain data is promising, because relative perturbations in strain tides are about 10 times larger than in gravity tides. The inversion of realistic synthetic tidal parameters (obtained from observed amplitude and phase of eight diurnal tidal components) shows that the resolving power of strain tides is comparable to that of gravity tides if tidal parameters are inverted minimizing the L2 mis t (as usually done). Both resolving powers improve if data are inverted minimizing the L1 mis t, and this improvement is particularly notable for gravity tides. The inversions of strain records have been performed after correcting measured strain for local distortion of the regional strain eld and ocean loading. For estimating the FCR parameters, eight diurnal tidal constituents (Q1, O1, P1, K1, 1, 1, J1 and OO1) have been used, by comparing mea- surements (corrected for ocean loading) and model predictions (corrected for the local strain distortion), minimizing the L1 mis t. The analysis of the only Gran Sasso strain data provides a value for the FCN period (about 429 sidereal days) robust and compa- rable to those from gravity tides, obtained from the joint inversion of data from several stations. The agreement between observations and predictions looks better than in any previous work that makes use of strain tides. The joint analysis of Gran Sasso and Bak- san strain data con rms, but does not improve, these results recently obtained. In both cases the quality factor is not well constrained because of the large uncertainty on the 1 phase; however the results are consistent with recently published values ( 20000). In Chapter 5 the new mode of faulting, discovered in the last decades and referred to as slow slip earthquakes, is examined. Many aspects of slow slip remain unexplained. Here an attempt to describe the characteristics of the rupture propagation through the analysis of strain records from three di erent slow events related to the 1978 Izu- Oshima (Japan) earthquake, the 1999 Durmid Hill (California) slow event and the 2003 Tokachi-oki (Japan) earthquake. The signals recorded during these slow events exhibit the same peculiarities observed in the strain sequences recorded at Gran Sasso during the 6 April 2009 L'Aquila earthquake, rst direct measurement of the di usive character of the rupture propagation. By using two di erent propagation mechanisms along 1D straight paths, namely constant propagation velocity and di usive processes, predicted strain history at both interferometers is fully consistent with di usive slip propagation, but inconsistent with constant velocity propagation. Not all slow earthquakes analysed are consistent with only one of the two models tested. Two of the four slow events (L'Aquila and Izu-Oshima F3 fault) are only consistent with di usive slip propagation. Constant velocity propagation gives much worst t to data, being unable to t the shape of minimum observed on signals recorded by BA interferometer and SHI borehole strainmeter for L'Aquila and Izu-Oshima slow earthquakes, respectively. For both slow events, the seismic moment density decreases about linearly with distance along the path, like the steady-state solution of 1D di usive processes. In the other cases (Durmid Hill, Tokachi-oki and Izu-Oshima F4 fault) it is not possible to discriminate the type of propagation. Observations are consistent with both types of slip propagation but for them the shape of seismic moment seems somewhat unrealistic, being a bell-shaped distribution peaked on the nodal line. These results suggest the necessity to deepen the source features, not well constrained in some cases. Moreover, also the assumption of 1D very thin path might be a source of uncertainty. In the last chapter the installation, occured in August 2011, of two new laser interferom- eters is described and their rst records analysed. These instruments, operating since November 2011, are installed in the Canfranc (Spain) Underground Laboratory (LSC). The LSC is located at depth in one of the most seismically active areas in Western Europe, at the Pyrenean chain that marks the boundary between the European plate and the Iberian microplate. The rst tests on strain data recorded by these interfer- ometers evidence the capability of producing clear records of low-frequency signals, for example relating to seismic waves, Earth free oscillations, and possible local aseismic stress release. A preliminary tidal analysis shows a good agreement between observed and predicted tides in the diurnal tidal band, suggesting that, if any, local strain dis- tortion e ects are small. In the semidiurnal tidal band, discrepancies between observed and predicted tides are noticeable; this might be a consequence of inadequate Earth and/or ocean models. These results deserve further investigation; in particular it would be interesting to deepen the local distortion e ect in the di erent frequency bands and estimate the ocean loading in more detail, especially in the Bay of Biscay which could be the main source of the discrepancies observed in the semidiurnal tidal band. [edited by author]
XI n.s.

The volumetric system is a commonly used experimental method for gas adsorption measurements. Starting from the conventional volumetric system (single-branched), the development of differential (double-branched) apparatus has been proposed to overcome some criticalities connected to the original design. The following study is focused on the assessment of the high-pressure differential volumetric apparatus (HP-ADVA) built at the University of Edinburgh in order to discover and characterise system peculiarities at different experimental conditions, in terms of temperature and pressure. To do this, an integrated approach is proposed: an initial experimental campaign has been performed to take confidentiality with the apparatus, then, the experimental results were the starting point for the development of a sensitivity and error analysis aimed at describing the effect of each operating parameter into the final result. In this regard, a different analytical approach, compared to the ones commonly proposed in literature, has been proposed to closely reproduce the real system. Beyond having obtained promising results, some criticalities, matching what originally hypothesized from the experimental campaign, have been noted: valve volume effect and temperature control and measurements have been discovered being crucial aspects, and, supposedly, source of errors leading to explain the unexpected results obtained by the experimental campaign. Moreover, the importance of symmetry maintenance among the branches has been repeatedly confirmed in the analysis. Some recommendations aimed at improving the system set-up have been moved regarding the installation of a temperature control system and more accurate temperature measurement devices. Additionally, an accurate assessment and characterisation of pneumatically-actuated valves, as well as of the differential pressure transducer used for pressure measurement, before the installation, could be useful to reduce inaccuracies.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Um dos casos clínicos mais frequentes na sociedade moderna envolve a localização e extração de projéteis de armas de fogo, que normalmente são feitos de chumbo, um material não ferromagnético. O desenvolvimento de uma técnica que possibilite a localização precisa destes auxiliará o procedimento de remoção cirúrgica, tendo vasta relevância e impactando diretamente no aumento da taxa de sobrevivência de pessoas feridas. Dessa forma, esta dissertação apresenta e discute duas novas abordagens baseadas em técnicas de inteligência computacional, objetivando a localização de projéteis de armas de fogo inseridos no corpo humano, a partir do processamento da informação contida em mapas de campo magnético. Em ambas as abordagens analisadas modela-se o projétil como uma esfera de raio a, localizado em um espaço de busca contido em um plano xy, o qual está situado a uma distância h do sensor no eixo z. As técnicas de localização requerem a geração de um campo magnético primário alternado por meio de um solenoide, o qual incide sobre o espaço de busca. Caso exista um projétil de arma de fogo nesta região, serão induzidas correntes parasitas no projétil, as quais, por sua vez, produzirão um campo magnético secundário, que pode ser medido por um sensor de alta sensibilidade localizado na extremidade do solenoide. Na primeira abordagem analisada, as posições x e y do projétil são determinadas por um algoritmo de janelamento que considera valores máximos e médios pertencentes aos mapas de campo magnético secundário. A determinação da distância h entre a esfera e o sensor foi obtida por meio de uma rede neural, e o raio da esfera a é estimado por um algoritmo genético. Na segunda abordagem, as quatro variáveis de interesse (x, y, h e a) são inferidas diretamente por um algoritmo genético. Os resultados obtidos são avaliados e comparados.
In modern society, one of the most frequent clinical cases involves location and extraction of firearms projectiles, usually made of lead, a non-ferromagnetic material. The development of a technique that allows the precise location of these projectiles will aid their surgical removal, which has a great relevance because it contributes directly to the increase of the survival rate of wounded patients. Thus, this dissertation presents and discusses two new approaches based on computational intelligence techniques, aiming at locating firearm projectiles inserted into the human body, by processing the information contained in magnetic field maps. On both approaches, the projectile is modeled by a sphere with radius a, located on a search space contained in a xy plane that is situated at a distance h from the sensor, along the z axis. The proposed location techniques require the generation of a primary alternating magnetic field by means of a solenoid, which aims at inducing eddy currents in a firearm projectile contained in the search space. In turn, these currents will produce a secondary magnetic field, which can be measured by a high-sensitivity sensor located at the bottom of the solenoid. In the first developed technique, the x and y positions of the projectile were estimated by a windowing algorithm that takes into account maximum and mean values contained on the secondary magnetic field maps. In turn, the distance h between the sphere and the sensor is inferred by a neural network, and the radius of the sphere a is estimated by a genetic algorithm. In the second technique, the four variables of interest (x, y, h and a) are inferred directly by a genetic algorithm. The results obtained are evaluated and compared.

Abstract In this work, the homogeneity of both the B0 and B1 fields was studied. Both B0 and B1 field homogeneities are the basic assumptions of high resolution liquid state NMR. Although some inhomogeneity of both of the fields is always present, the spectrometers can be operated, with the help of the developed spectral purging techniques, without giving any thought to the field inhomogeneities or the necessary actions to minimize their adverse effects. Although the effect of B0 inhomogeneity can occasionally be seen, the B1 fieldin a modern probe head is often assumed to be sufficiently homogenous for any practical purpose. By using the method used in this study the B1 field strength along one axis, typically the z-axis, can be easily mapped. Based on the information gathered from a single experiment, one can obtain reliable and valuable information about the B1 field distribution, e.g. homogeneity of the coil. From such information, the degree of required artifact suppressing methods for successful NMR experiments can be determined. Since normal pulse length calibration also requires the acquisition of several 1-D spectra, the required experimentation time is not increased. Although the maximum amount of signal from an NMR experiment is obtained when the signal is acquired from a maximum number of resonating spins, the results presented show that significantly more homogenous B1 field along the active sample volume is achieved by rejection of the signal originating from the outer parts of the coil length. Although the total amount of signal obtained from the outer parts of the RF-coil is not very high, some loss of signal is associated with the spatially selective acquisition. The rejected signal, however, is a significant source of artifacts, and if no precautions were taken, the artifacts would severely decrease the quality of the acquired data. If the sample concentration can be increased, it would be advantageous to dissolve the amount of sample available in as small an amount of solvent as is possible and place the sample in the most B1 homogenous part of the probe-head RF-coil. With the same amount of nuclear spins concentrated into a smaller volume, the sensitivity of an NMR experiment can be increased manifold. As an application of a spatially selective data acquisition, a versatile method capable of producing a map of the B0 field strength and its variation along the sample volume is presented.

Many biological specimens are transparent and in weak intensity contrast, making it invisible using conventional bright field microscopes. Therefore, the phase-based optical microscopy techniques play important roles in the development of the modern biomedical science. Furthermore, the ability to achieve quantitative phase measurement of the tiny structures of biomedical specimens is of great importance for many biomedical applications. Thus, quantitative phase imaging becomes an important technique to measure the phase variations due to the difference of refractive index and geometric thickness of various structures and materials within the biomedical specimens. In this thesis, a spectral modulation interferometry (SMI) is developed to achieve quantitative phase imaging. In SMI, the phase and amplitude information will simultaneously be modulated onto the interference spectrum of the broadband light. Full-field phase images can be obtained by scanning along the orthogonal direction only. SMI incorporates the advantages of low coherence from broadband light source, high sensitivity from spectral domain interferometry and the high speed from the spectral modulation technique to achieve quantitative phase measurement with free of speckle, high temporal sensitivity (~0.1nm) and fast imaging rate. The principles of SMI system and programming as well as some important image processing methods will be discussed in detail. Besides, the quantitative phase measurement of the reflective object (USAF resolution target) and the transmitted biological objects (Peranema, human cheek cells) will be shown.
Master of Science

This effort is focused on the design, calibration, and implementation of a high temperature heat flux sensor for thermal systems research and testing. The High Temperature Heat Flux Sensor (HTHFS) was designed to survive in the harsh thermal environments typically encountered in hypersonic flight, combustion and propulsion research, and large-scale fire testing. The sensor is capable of continuous use at temperatures up to 1000 â ¦C. Two methods for steady-state calibration of the HTHFS at elevated temperatures have been developed as a result of this research. The first method employs a water-cooled heat flux sensor as a reference standard for the calibration. The second method utilizes a blackbody radiant source and a NIST calibrated optical pyrometer as the calibration standard. The HTHFS calibration results obtained from both methods compare favorably with the theoretical sensitivity versus temperature model. Implementation of the HTHFS in several types of transient thermal testing scenarios is also demonstrated herein. A new data processing technique is used to interpret the measurements made by the HTHFS. The Hybrid Heat Flux (HHF) method accounts for the heat flow through the sensor and the heat storage in the sensor, and thus renders the HTHFS virtually insensitive to the material on which it is mounted. The calibrated output of the HTHFS versus temperature ensures accuracy in the measurements made by the sensor at high operating temperatures.
Ph. D.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Esta Tese teve por objetivo desenvolver um magnetômetro de alta sensibilidade, baseado nas características de fase do efeito da Magnetoimpedância Gigante (GMI – Giant Magnetoimpedance), para medição de campos magnéticos ultra-fracos. Elementos sensores GMI apresentam grande potencial na fabricação de magnetômetros que conciliem alta sensibilidade e elevada resolução espacial com baixo custo. A otimização da sensibilidade do transdutor magnético é diretamente afetada pela sensibilidade de seus elementos sensores GMI, cuja maximização é um processo intrinsecamente multivariável. Consequentemente, a metodologia experimental empregada iniciou-se pelo desenvolvimento de um sistema automático de caracterização das amostras GMI, de modo a se garantir a agilidade do processo de caracterização, possibilitando a obtenção de um volume significativo de informações experimentais. A análise minuciosa dos dados provenientes das medições experimentais permitiu a definição do ponto ótimo de operação das amostras GMI estudadas. Em todas as medições experimentais realizadas foram obtidas e avaliadas as curvas de histerese das amostras GMI. Na sequência, foram idealizados circuitos eletrônicos para condicionamento das amostras GMI e leitura das características de fase de sua impedância, destacandose a configuração eletrônica desenvolvida para a amplificação da sensibilidade de fase. Foram, inclusive, depositadas patentes nacionais e internacionais referentes ao método proposto e ao novo transdutor magnético GMI (PI 0902770-0; PI 1004686-0; WO/2010/094096 e WO/2012/048395). As caracterizações e ensaios experimentais realizados indicaram a eficácia da abordagem proposta, evidenciando o grande potencial do magnetômetro GMI desenvolvido, o qual apresentou uma elevada sensibilidade de 5 mV/nT. A resolução do magnetômetro foi limitada pelo ruído magnético ambiental, indicando que sua capacidade de medição de campos inferiores aos níveis de ruído poderá ser claramente evidenciada quando for avaliada em ambiente magneticamente blindado. Os estudos teórico-experimentais realizados indicam o potencial do transdutor magnético GMI desenvolvido, caracterizado por seu baixo custo e elevada sensibilidade, para aplicação na medição de campos magnéticos ultra-fracos.
This Thesis aimed at developing a high sensitivity magnetometer, based on the phase characteristics of the Giant Magnetoimpedance effect (GMI), for measuring ultra-weak magnetic fields. GMI sensor elements have great potential to implement magnetometers that combine high sensitivity and high spatial resolution with low cost. The optimization of the magnetic transducer sensitivity is directly affected by the sensitivity of its GMI sensor elements, whose maximization is inherently multivariate. Consequently, the first step of the experimental methodology employed was to develop an automatic system for the characterization of GMI samples, so as to ensure the agility of the characterization process, allowing the gathering of a significant amount of experimental data. A thorough analysis of the experimental data led to the definition of the optimal operation point of the analyzed GMI samples. The hysteresis curves of the GMI samples were obtained and evaluated, in all of the performed experimental measurements. Based on the characterization studies results, electronic circuits were designed for conditioning the GMI samples and reading their impedance phase characteristics, highlighting the new electronic configuration developed for enhancing the phase sensitivity. National and international patents were filed, related to the proposed method, for sensitivity enhancement, and to the new GMI magnetometer (PI 0902770-0; PI 1004686-0; WO/2010/094096 e WO/2012/048395). The performed experimental characterizations and assays indicated the effectiveness of the proposed approach, showing the great potential of the developed GMI magnetometer, which presents a high sensitivity of 5 mV/nT. The magnetometer resolution was limited by the environmental magnetic noise, pointing out their capability in measuring fields below the environmental noise level, which can be clearly evidenced only when evaluated in a magnetically shielded room. The theoretical and experimental studies carried out indicate the potential of the developed GMI magnetic transducer, characterized by its low cost and high sensitivity, for applications involving the measurement of ultra-weak magnetic fields.

A high-precision mixed-signal mismatch measurement technique for metal-oxide metal (MoM) capacitors as well as the design of a 13-GHz 5-bit 360-degree phase shifter are presented. This thesis presents a high-precision, mixed-signal mismatch measurement technique for metal-oxide–metal capacitors. The proposed technique incorporates a switched-capacitor op amp within the measurement circuit to significantly improve the measurement precision while relaxing the resolution requirement on the backend analog-to-digital converter (ADC). The proposed technique is also robust against multiple types of errors. A detailed analysis is presented to quantify the sensitivity improvement of the proposed technique over the conventional one. In addition, this thesis proposes a multiplexing technique to measure a large number of capacitors in a single chip and a new layout to improve matching. A prototype fabricated in 180 nm CMOS technology demonstrates the ability to sense capacitor mismatch standard deviation as low as 0.045% with excellent repeatability, all without the need of a high-resolution ADC. The 13-GHz 5-bit 360-degree phase shifter consists of 2 stages. The first stage utilizes a delay line for 4-bit 180-degree phase shift. A second stage provides 1-bit 180-degree phase shift. The phase shifter includes gain tuning so as to allow a gain variation of less than 1 dB. The design has been fabricated in 180 nm CMOS technology and measurement results show a complete 360◦ phase shift with an average step size of 10.7◦ at 13-GHz. After calibration the phase shifter presented an output gain S21 of 0.5 dB with a gain variation of less than 1 dB across all codes at 13-GHz. The remaining s-parameter testing showed a S22 and S11 below -11 dB and a S12 below -49 dB at 13 GHz.

The diagnostic and pharmaceutical industries rely on tools for characterizing, discovering, and developing bio-molecular interactions. Diagnostic assays require high affinity capture probes and binding specificity for accurate detection of biomarkers. Selection of drug candidates depends on the drug residency time and duration of drug action. Further, biologic drugs can induce anti-drug antibodies, which require characterization to determine the impact on the drug safety and efficacy. Label-free biosensors are an attractive solution for analyzing these and other bio-molecular interactions because they provide information based on the characteristics of the molecules themselves, without disturbing the native biological systems by labeling. While label-free biosensors can analyze a broad range of analytes, small molecular weight analytes (molecular weight < 1kDa) are the most challenging. Affinity measurements for small molecular weight targets require high sensitivity and long-term signal stability. Additional difficulties occur with different liquid refractive indices that result from to temperature, composition, or matrix effects of sensor surfaces. Some solutions utitlize strong solvents to increase the solubility of small molecules, which also alter the refractive index. Moreover, diagnostics require affinity measurements in relevant solutions, of various refractive indices. When a refractive index difference exists between the analyte solution and the wash buffer, a background signal is generated, referred to as the bulk effect, obscuring the small signal due to surface binding in the presence of large fluctuations due to variations of the optical refractive index of the solutions. The signal generated by low molecular weight analytes is small, and conventional wisdom tends toward signal amplification or resonance for detection of these small signals. With this approach, Surface Plasmon Resonance (SPR) has become the gold standard in affinity measurement technologies. SPR is an expensive and complex technology that is highly susceptible to the bulk effect. SPR uses a reference channel to correct for the bulk effect in post-processing, which requires high precision and sophisticated temperature control, further increasing the cost and complexity. Additionally, multiplexing is desirable as it allows for simultaneous measurements of multiple ligands; however, multiplexing is only possible in the imaging modality of SPR, which has lower sensitivity and difficulty with referencing. The Interferometric Reflectance Imaging Sensor (IRIS) is a low-cost, optical label-free bio-molecular interaction analysis technology capable of providing precise binding affinity measurements; however, limitations in sensitivity and usability have previously prevented its widespread adaptation. Overcoming these limitations requires the implementation of automation, compact and easy-to-use instrumentation, and increased sensitivity. Here, we explore methods for improved sensitivity and usability. We achieve noise reduction and elimination of solution artifacts (bulk effect) through engineered illumination uniformity and temporal and spatial image processing. To validate these methods, we experimentally analyze small molecule molecular interactions to demonstrate highly sensitive kinetic binding measurements, independent of solution refractive index.
2023-09-24T00:00:00Z

碩士
國立臺灣師範大學
地球科學系
93
Uranium isotopic composition and concentration have been widely applied to various fields in the earth sciences. This work focused on the improvement of analytical technique for uranium isotopic ratio and concentration measurements by Quadrupole Inductively Coupled Plasma Mass Spectrometer (Q-ICPMS). To approach the goal of permil-level analytical precision with only ng-U sample sizes, three strategies were applied. First, the Q-ICPMS was connected to a micro-concentric nebulization (MCN) introduction system to amplify sensitivity and to reduce required sample size. Standard deviation filters were then used to remove outliers to improve precision and accuracy. Finally, the 233U-236U double spikes were added and then data were processed with the standard bracketing method to correct mass fractionation and ratio drifting and, therefore, higher precision and accuracy could be achieved. The results showed that the overall sensitivity (ion detected/ atoms introduced) was about 0.3~0.4. Oxide and hydride levels are less than 0.3% and 2 ppm, respectively. Under measurement time of 15-20 minutes, U standards with 30 ng of U give within-run precisions better than 3.3 (±2 R.S.D.) for 234U and better than 3.1 (±2 R.S.D.) for [238U]. Replicate measurements made on standards reveal that between-run precision of 4.1 (±2 R.S.D.) for 234U and 2.4 (±2 R.S.D.) for [238U] can be achieved. Measurements of U isotopic ratios and concentrations in coral, sea water, and speleothem samples show averaged 234U and [238U] within-run precisions of 5 and 5.5, respectively. All measurements made by this work reveal no significant difference from the values measured by High Resolution ICPMS (Li et al., 2005; X. Wang unpublished data) in the 95% confidence interval.

碩士
輔仁大學
營養科學系
99
The purpose of this study was to assay the relationship between high sensitivity C-reactive protein (hs-CRP) and anthropometric measurements, blood biochemistry and dietary intakes in diabetic patients with metabolic syndrome. From May to December, 2008, 40 outpatients with diagnosed metabolic syndrome, 12 male and 28 females, the average age of 55±12 year were recruited from Cathay General Hospital Endocrine Branch in this study. The dietary investigation included 3-day dietary record and 24-hour diet recall by the dietitian, and the blood biochemistry values, blood pressure, as well as the anthropometric measurements were examined. The results showed that there were inverse correlation between blood hs-CRP values and the systolic pressure, hs-CRP and the diastolic pressure (r = - 0.416 and - 0.371, p=0.022 and 0.044, respectively). However, there is a positive correlation between fat intake and hs-CRP (r=0.405, p=0.009), especially polysaturated fatty acid(r=0.344, p=0.03). If participants were divided into 3 groups based on their hs-CRP levels, i.e. Low: hs-CRP< 1 mg/L, Medium: 1 mg/L 3 mg/L, medium and high groups have higher body fat and the blood triglyceride (TG) concentrations than low hs-CRP group. Based on the BMI, participants with ideal body weight had higher LDL-C and lower hs-CRP than the overweights.

碩士
國立彰化師範大學
機電工程學系所
104
This thesis designs a small displacement sensor based on highly sensitive total internal reflection (TIR) interferometry. A heterodyne light beam reflected by a plane mirror penetrates into a high-sensitivity TIR apparatus (composed of a half- and two quarter- wave plates and an analyzer) at an angle larger than a critical angle. When the azimuth angles of these wave plates and the analyzer are properly selected, the final phase difference between p- and s- polarizations emerging from the apparatus can be greatly enhanced A small displacement of the mirror causes the light beam incident on the TIR apparatus to be deflected, thereby inducing a phase difference variation of the light beam emerging from the TIR apparatus. The experiment results demonstrates that the sensitivity and the resolution of 4.1°/mm and 20 nm can be achieved.

In recent years, the interest for mid infrared radiation has increased for both fundamental research and industrial applications, thanks to the development of continuous-wave room-temperature sources, such as quantum cascade lasers, which fulfill the requests for relatively high power, narrow emission and compact size. The main absorption lines of simple molecules lie in this spectral region and the study of their absorption spectra can give precise information on their concentration. Both these aspects enabled widespread applications of tunable laser absorption spectroscopy for real-time, in-situ and non-invasive gas sensing. Trace gas detection by optical spectroscopy plays a key role in applications that demand quantitative measurements of extremely small amounts of molecular gases. The enormous relevance and the complex interplay between climate change and anthropogenic influence, has focused the attention on mitigation of the greenhouse gases effects, the well-known increase in the average planetary temperature and the increase in atmospheric concentrations of climatically active gases, including CO2. In this context, the scientific and industrial debate focuses on possible methods for measuring and quantifying CO2 emissions from fossil sources, since the identification of markers to control and monitor the reduction of these sources is a necessary step to implement any mitigation politics. In this respect, radiocarbon method represents the most promising approach to validate the estimations provided by single nations or companies. Indeed, radiocarbon is a natural clock, with a lifetime of about 5,700 years, and the measurement of its concentration is an optimal approach to distinguish "young" samples from very old ones, like fossil fuels, completely depleted in radiocarbon. However, ultra-high detection sensitivity is required to quantify radiocarbon due to its extremely low natural abundance being about one part per trillion (10-12) in the biosphere. Thanks to the combination of continuous wave-cavity ring down spectroscopy (CW-CRDS) and strong absorption from fundamental ro-vibrational molecular transitions in the midinfrared, we can overcome the detection limit imposed by the small amount of molecular gases. Nevertheless, state of-the-art conventional CW-CRD spectrometers in the mid IR cannot reach the minimum detectable absorption level required to detect 14CO2, mainly because of the empty-cavity decay rate fluctuations. To overcome this limitation, about ten years ago a novel high-resolution and high-sensitivity spectroscopic technique was proposed: Saturated-Absorption Cavity Ringdown (SCAR) spectroscopy. This technique has shown to improve by more than one order of magnitude the limits of conventional linear-absorption CRDS, thanks to a sample absorption measurement which is independent from the other cavity losses during the same cavity decay event. Indeed, SCAR, benefiting from both CW-CRDS and saturation spectroscopy, overcomes the limits of linear CRD by measuring in each and every single decay event both the "empty" and the "full" cavity contribution. Thanks to the achieved sensitivity, detection of rare molecular species, such as radiocarbon dioxide, was demonstrated. With this work, we describe disruptive applications of this technique, by accurately measuring radiocarbon dioxide concentrations. In particular, these three application areas were targeted: the biogenic fraction in biofuel and bioplastics; parts of concrete walls from nuclear power plants for decommissioning purposes; dating of archaeological samples from Sumer settlements. Specific, customized sample purification processes as well as measurements schemes have been devised.

碩士
國立彰化師範大學
機電工程學系
106
In this thesis, a high-sensitivity total-internal-reflection (TIR) phase-shifting interferometry is proposed for measuring the two-dimensional (2D) refractive index distribution of a material. A linearly-polarized expanding beam after traveling through a Soleil-Babinet compensator and a spatial filter enters into a high-sensitivity TIR apparatus. The TIR apparatus consists of a phase shifter (formed by combining a half-wave plate and a quarter-wave plate that display specific optic-axis azimuths), an isosceles right-angle prism whose base is directly contacted with a tested material, and an analyzer. The interference signal of the TIR beam output from the apparatus is captured by a CCD camera. Based on the four-step phase-shifting method by modulating the Soleil-Babinet compensator, the 2D phase difference used to determine the refractive index distribution of the material is obtained. Since the 2D phase difference displayed by therefractive indexof the material is linked to the azimuth angle of the quarter-wave plate axis and analyzer transmission axis, the high sensitivity measurement are achievable by adjusting the transmission axis. The experiment demonstrated that the sensitivity and the resolution of 8.96×103 /RIU and 4.46×10-6 RIU can be achieved. In addition to high, tunable sensitivity and excellent resolution, the designedmethod also offers the merit of high stability due to its common-path configuration.

Student Number : 9102778K - MSc(Eng) dissertation - School of Chemical and Metallurgical Engineering - Faculty of Engineering and the Built Environment
Strain ageing anisotropy, a surprising property of iron, implies that interstitials, which are non-lattice obstacles, can give non-symmetrical opposition to glide. Al- though this has been investigated by others, it is shown that it is di±cult to eliminate extraneous residual stresses during testing. An Avery torsion machine was adapted for the study of strain ageing anisotropy through the design of a torque and twist measurement system. This required the optimization of sensitivity, stiffness and me- chanical stability criteria, while ensuring practicality. When a ¯ne-grained sample with circumferential groove was tested a sharp yield point and lack of yield after ageing in the reverse direction was observed. Although more testing is required, it con¯rms the results of other researchers. In testing it was found that the quality of the sample machining was critical in achieving an accurate yield, and the groove design must be reviewed and improved. While the system measured to the required torque resolution, the strain measurement system could be improved by redesign and better calibration statistics.