We examine the precise radial velocities and chromospheric emission and derive the fundamental parameters of eight K stars - 36 Ophiuchi A, B (K0 V, K1 V), 61 Cygni A, B (K5 V, K7 V), β Geminorum (K0 IIIb ), δ Sagittarii (K2.5 IIIa), α Tauri (K5 III), and ϵ Pegasi (K2 Ib) - through analyses of high quality (S/N > 1000) near-infrared (864-878 nm) spectra. The spectra were obtained as part of the hydrogen fluoride precise (≈ 15 — 30 m s-1) radial velocity (RV) program at the Canada-France-Hawaii 3.6-m telescope (1981- 1992) and the Dominion Astrophysical Observatory 1.22-m telescope (1991- 1995). We define the ∆EW 866.2 index used to quantify changes in the core flux of the Ca II 866.214 nm line and show the index is a sensitive measure of changes in chromospheric emission. We compare the “reference” spectrum for each star with synthetic spectra of the 864.7-867.7 nm region and derive the fundamental parameters: effective temperature [special characters omitted] surface gravity [special characters omitted], metallicity ([M/H]), and microturbulence (ξ). We describe an efficient, time-saving method which identifies and eliminates insignificant lines. Through our comparisons of the narrow spectral region for these “well-known” stars and through our development of a rapid synthesis method, we demonstrate a solid foundation for a broader, more comprehensive study of this region of the H-R diagram. The nearly identical stars 36 Oph A and B have dissimilar chromospheric activity. For these stars, we derived [special characters omitted] = 5125 K, log g = 4.67, [M/H] = -0.25, and ξ = 1.4 km s-1, in excellent agreement with relationships predicted by stellar interior models for [special characters omitted] ≈ 0.75 and [Fe/H] = -0.3. For 61 Cyg A, we detect a rotation period of 36.2 days in the ∆EW 866.2 index and of 37.8 days in the radial velocities, implying that active regions are spatially and temporally coherent over long time scales for this star. For 61 Cyg A, we derived [special characters omitted] = 4545 K, log g = 4.55, [M/H] = -0.40, and ξ = 1.5 km s-1; for 61 Cyg B, [special characters omitted] = 4150 K, log g = 4.55, [M/H] = -0.40, and ξ = 0.7 km s-1. These parameters are in excellent agreement with relationships predicted by stellar interior models for [Fe/H] = -0.4 and [special characters omitted] ≈ 0.65 for 61 Cyg A, and [special characters omitted] ≈ 0.55 for 61 Cyg B. Low-amplitude RV variability is a ubiquitous characteristic of the K giants. For β Gem, we find similar RV {K = 46.23 ± 3.9 m s-1, P = 584.65 ± 3.3 dy) and ∆EW 866.2 index (K = 0.583 ± 1.9 pm, P = 587.7 ± 12 dy) periods. If due to rotation modulation of some surface feature, this period is inconsistent with the most reliable ν sin i value for this star. We detect a long-term (> 12 yr) change in the ∆EW 866.2 index for this star, reminiscent of a solar-type magnetic cycle. For δ Sgr, we find significant long-term trends in the radial velocities and ∆EW 866.2 index, and significant, but aliased, RV periods at 1.98 days (K = 82.1 ± 9.1 m s-1) and 293 days {K = 68.8 ± 9.8 m s-1). α Tauri has a 647.93-dy period (K = 114.9±10.6 m s-1) in the radial velocities, but no corresponding period in the ∆EW 866.2 index. From 1.22- m telescope observations, we find a 1.8358-dy RV period (K = 32.0 ± 5.0 m s-1) consistent with theoretical granulation-driven acoustic modes or a fundamental overtone (n ≈ 4). The supergiant ϵ Peg resembles a semi-regular RV variable. We find multiple RV periods (not aliases) of 65.2 days (K = 415.8 ± 59.0 m s-1), 46.3 days (K = 559.1 ± 57.0 m s-1), perhaps both fundamental overtones, and 10.7 days (K = 410.3 ± 66.0 m s-1), perhaps related to solar-type spicules. The 10.7-dy period is present in the ∆EW866.2 index for this star. / Graduate

Vidros dopados com íons de elementos terras−raras são amplamente estudados com o objetivo de obtenção de meios ativos para lasers, amplificadores e sensores ópticos. Dentro desta classe de materiais, o vidro ZBLAN dopado com íons de Er+3, tem recebido grande atenção nos últimos anos. No entanto, nenhum estudo em espectroscopia óptica foi realizado para este sistema vítreo (ZBLAN:Er3+) em temperaturas inferiores a 10 K. Nesta dissertação foi promovida com sucesso, através de medidas de absorção, e luminescência entre os multipletos 4S3⁄2 e 4I15⁄2, uma completa identificação experimental das posições dos níveis de energia dos multipletos excitado (4S3⁄2) e fundamental (4I15⁄2), do íon Er3+,na matriz ZBLAN na temperatura de 2 K. Os resultados obtidos e aqui apresentados são inéditos e indicam a ocupação de sítios muito semelhantes pelos íons Er3+ dentro da matriz vítrea. Também a partir da comparação entre o espectro de luminescência e conversão ascendente de energia foi possível observar um forte acoplamento entre os íons Er3+ e a matriz ZBLAN / Glasses doped with earth−rare elements ions are widely study with the objective of obtains of the active environment for lasers, optics amplifier and optics feeler. Inside this material c1ass, the ZBLAN glass doped with Er3+ ions has received great attention on last years. Meantime, either study in optic spectroscopy ware realized for this system (ZBLAN:Er3+) in temperature below 10 K. In this paper was realized with success, through measures of absorption and luminescence between 4S3⁄2 e 4I15⁄2 multiplets, a complete experimental identification of the stark positions for 4S3⁄2 and 4I15⁄2 multiplets, for Er3+ ions, in ZBLAN glass matrix at 2 K. The resultants obtained here are originals and showed the occupation of environment very similar by Er3+ ions. To finish we show from the comparison between the luminescence and ascendant conversion of energy spectrum was possible observe the existence of an interaction strong between the ZBLAN glass matrix with Er3+ ions.

Thesis advisor: Matthias M. Waegele / The properties of electrified interfaces, such as surface structure of metal catalyst, local pH, coverage of surface-adsorbed intermediates, interfacial electric field, and water structure, influence the activity and selectivity of electrocatalytic reactions. Because these interfacial properties often influence each other and undergo changes with applied potential, it is very challenging to identify the key characteristics of the interface that directly modulate electrocatalytic reactions. In this thesis, we demonstrate in-situ probing of electrochemical interfacial properties by employing surface-enhanced infrared (IR) absorption spectroscopy (SEIRAS) in conjunction with surface-adsorbed CO (COads) as a molecular probe of the Cu/aqueous electrolyte interface. This interface shows potential for the reduction of CO2 and CO to a wide variety of hydrocarbons. The CO and CO2 reduction reactions (CO/CO2RR) feature COads as an intermediate; therefore, this interface is conveniently probed by COads. In the first part if this thesis, we focus on investigating the dynamics of the surface morphology of the electrode during electrocatalysis. We found that the surface morphology of polycrystalline Cu undergoes reconstructions during CO/CO2RR. We determined that these reconstructions can be induced by COads and the local pH. As a result of the surface reconstructions, new specific surface sites form that can effect catalytic activity. For example, we detected an electrochemically inert COads population that appears as a result of reconstruction processes. Further, to form a rigorous connection between the product formation and the atomic-level surface morphology of rough polycrystalline Cu electrodes, we combined SEIRAS with differential electrochemical mass-spectrometry (DEMS). We established the potential-dependence of the line shape of the C≡O stretch band as an indicator of the atomic-level surface morphology. The last part of the thesis focuses on the determination of properties of the electrochemical double layer. Specifically, we elucidated the effects of cation identity on the electrochemical double layer. By evaluating the C≡O stretch frequency in the presence of alkali metal cations (Li+, K+, and Cs+), we determined that the promotion of the CO reduction reaction is associated with a cation-dependent interfacial field. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

The purpose of this research is to explore and investigate the biophysical properties of living cells using microfluidics based electrical impedance sensing (EIS) technique. It provides a non-invasive approach to detect label-free biological markers in the regulation of cellular activities even at a molecular level. We specifically focus on the development, testing, and theoretical modeling of electrical impedance spectroscopy for neuroblastoma cells and endothelial cells. First, we demonstrate that the EIS technique can be used to monitor the progressive mitochondrial fission/fusion modification in genetically modified human neuroblastoma cell lines. Our results characterize quantitatively the abnormal mitochondrial dynamics through the variations in cytoplasm conductivity. Secondly, we employ a real time EIS method to determine the biophysical properties of the junctions which join one endothelial cell with one another in a monolayer of endothelial cells. In particular, we examine the role of the protein, c-MYC oncogene, in the barrier function. Our results show that the downregulation of c-MYC oncogene enhances the endothelial barrier dysfunction associated with inflammation. Finally, we measure and find that the electrical admittance (the reciprocal of the impedance) of the monolayer of endothelial cellular networks exhibits an anomalous power law of the form, Y ∝ ωα, over a wide range of frequency, with the value of the exponent, α, depending on the severity of the inflammation. We attribute the power law to the changes of the intercellular electric permeability between neighboring endothelial cells. Thus, the inflammation gives rise to relatively smaller values of α compared to that of the no-inflammation group. Furthermore, we propose a simple percolation model of a large R-C network to confirm the emergent of power law scaling behavior of the complex admittance, suggesting that the endothelial network behaves as a complex microstructural network and its electrical properties may be simulated by a large R-C network. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

Rare earth elements, (REE), at ug g⁻¹ levels are used for studies of petrogenisis of different geological materials. For these studies, the REE must be determined precisely. An analytical program was established using an IL 200 Inductively Coupled Plasma, (ICP), spectrometer for the determination of the REE in various matrices, taking into consideration both matrix and spectral interferences, which were found to be severe in some cases. Dissolution of the sample, (0.4-1.0 g), was carried out using two methods; a microwave heated dissolution using a modified commercial microwave oven and a conventional oven heated closed pressure digestion vessel method. The results of these two methods were compared to determine the viability of using the more rapid microwave heated method. Separation of the REE from matrix elements was investigated using three cation exchange resins; Amber lite IR 120 (H), Zeocarb 225 and Dowex 50-WXS. A gradient acid elution method was established using a 15 cm by 20 mm Zeocarb 225 column. The sample was eluted with 140 ml of a 1.5 M H⁺ solution containing 0.75 M Cl⁻ and 0.75 M NO₃⁻, this fraction containing all the matrix elements. The REE were then eluted from the resin with 100 ml of 3 M HNO₃. The REE containing fraction was then reduced to 5 ml, diluted to 10 ml, and analysed for REE content. Liquid-liquid extraction methods for the separation of REE from matrix elements were investigated. It was found that the REE could be extracted synergistically from various buffered aqueous acidic media into chloroform, (CHCl₃), by hexafluoroacetylacetone, (HHFA), and quinoline. Acetylacetone, ( AcAc), was found to react with hexamethylenetetramine, (hexamine), when hexamine was used to buffer the aqueous phase during extraction procedures. The product of this reaction, 3.5-diacetyl-1.4-dihydro-2.6-dimethyl pyridine, was identified using X-ray crystallography.

Terahertz spectroscopy shows promise in applications including quality control, security and medical imaging, but remains limited by slow data acquisition. This also poses an impediment to the study of samples undergoing irreversible transitions, as typical schemes rely on the assumption that results are consistent from pulse to pulse. In this work, we propose a high-speed terahertz detection technique based on chirped-pulse encoding that can enable single-shot measurements up to laser repetition rates in the MHz. An all-normal dispersion optical fiber is used to create a broadband probe spectrum, onto which the terahertz pulse waveform is encoded as a phase modulation. The sampling process makes use of the dispersive Fourier transform, a technique which maps the spectral features of a pulse into the time domain, in this case via the dispersion of a long commercial optical fiber. The elongated pulse can subsequently be detected with a high-speed photodetector and oscilloscope. We show steps toward implementing the technique by characterizing the components required to shape the probe pulse and providing some proof-of-concept measurements. In addition, fiber optic simulation procedures are detailed including complete coupled generalized nonlinear Schrödinger equations to provide insight into polarization effects that occur during highly nonlinear processes such as supercontinuum generation.

No description available.

Laser-induced breakdown spectroscopy (LIBS) is an efficient tool for identification of elemental composition and characterization of materials. The concept of this technique is to focus a laser pulse of sufficiently high power on to a sample to create a plasma plume of atoms, ions, and molecules. The measurement of the resulting optical emission from these species provides the basis of the spectral analysis. Spectroscopic analysis of the plasma generated by Nd:YAG laser irradiation of wheat flour tortillas was carried out. A careful selection of spectral lines of Ca, Na and K which do not suffer from spectral interference was made. Among the spectral lines selected for analysis, the Na I 589.00 and 589.60-nm doublet lines were found to show the same intensity ratio values. A study on combustion was carried out with the use of LIBS. The main focus of this study was to compare results previously obtained using a rectangular slot burner with new results using a McKenna burner for equivalence ratios measurement in atmospheric premixed methane-air flames with ungated LIBS and also obtaining a temperature profile for our new burner. The Mckenna burner has a steady and less turbulent flame. Fortyive equivalence ratios were calculated. LIBS spectra of helium, argon and nitrogen were acquired using samples of pure gases at low pressures. The spectra from the three species showed continuum contributions which differ from one gas to the other. To better understand LIBS of gaseous samples, we have performed a study of the laser-induced plasmas in three gases, i.e., Ar, He, N2 and their mixtures. The evolution of plasma intensity and electron density, with time was studied at different laser pulse energies. Samples containing cerium, cesium and strontium were made with known concentrations and analyzed using laser-induced breakdown spectroscopy (LIBS). Powder samples are more challenging to analyze using LIBS than pellets. Spectra resulting from these samples under various experimental conditions were compared for possible interferences and other properties, placing particular interest in Ce II 418.65-nm, Cs I 852.11-nm and Sr I 460.73-nm atomic emission spectra lines because these were outstanding strong lines of these three aforementioned elements.

No description available.

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