Analysis of Different Methodologies to Calculate Bouguer Gravity Anomalies in the Argentine Continental Margin

We have tested and used two methods to determine the Bouguer gravity anomaly in the area of the Argentine continental margin. The first method employs the relationship between the topography and gravity anomaly in the Fourier transform domain using Parker’s expression for different orders of expansion. The second method computes the complete Bouguer correction (Bullard A, B and C) with the Fortran code FA2BOUG2. The Bouguer slab correction (Bullard A), the curvature correction (Bullard B) and the terrain correction (Bullard C) are computed in several zones according to thedistances between the topography and the calculation point. In each zone, different approximations of the gravitationalattraction of rectangular or conic prisms are used according to the surrounding topography. Our calculations show that the anomaly generated by the fourth order in Parker’s expansion is actually compatible with the traditional Bouguer anomaly calculated with FA2BOUG, and that higher orders do not introduce significant changes. The comparison reveals that the difference between both methods in the Argentine continental margin has a quasi bimodal statistical distribution. The main disadvantage in using routines based on Parker's expansion is that an average value of the topography is needed for the calculation and, as the margin has an abrupt change of the topography in the continental slope area, it causes a bimodal distribution. It is worth noticing that, as expected, the most important differences between both methods are located over the continental slope both in complex structures such as part of the shared margin, as well as in isolated points where there are contributions from short wavelength or rugged topography.Fil: Pedraza de Marchi, Ana Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Ghidella, Marta E.. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Tocho, Claudia. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin

Photophysical Processes of Polymethlne Dyes

Laser Hash photolysis, laser induced optoacoustic spectroscopy (LIOAS), and fluorescence data were used for the study of the photophysical deactivation processes of excited 3,3 diethylthiadicarbocyanine iodide (DTDCI). Direct excitation of this molecule in air saturated methanol solutions at room temperature results in the formation of only one transient species, a photoisomer, the spectrum of which was derived for the 600-680 nm spectral range. The energy content difference between the ground state of the stable form and that of the photoisomer was evaluated, $latex \Delta E = 0.15 \pm 0.15 \enspace eV$, as well as limit values for the photoisomer fluorescence quantum efficiency $latex(\Phi _{f} ^{P}) < 0.2$ and for the quantum yield for the back photoisomerization from the first excited singlet state of the photoisomer to the ground state of the stable form $latex(\Phi _{PN}\leq 0.14)$

Analysis of Different Methodologies to Calculate Bouguer Gravity Anomalies in the Argentine Continental Margin

We have tested and used two methods to determine the Bouguer gravity anomaly in the area of the Argentine continental margin. The first method employs the relationship between the topography and gravity anomaly in the Fourier transform domain using Parker’s expression for different orders of expansion. The second method computes the complete Bouguer correction (Bullard A, B and C) with the Fortran code FA2BOUG2. The Bouguer slab correction (Bullard A), the curvature correction (Bullard B) and the terrain correction (Bullard C) are computed in several zones according to thedistances between the topography and the calculation point. In each zone, different approximations of the gravitationalattraction of rectangular or conic prisms are used according to the surrounding topography. Our calculations show that the anomaly generated by the fourth order in Parker’s expansion is actually compatible with the traditional Bouguer anomaly calculated with FA2BOUG, and that higher orders do not introduce significant changes. The comparison reveals that the difference between both methods in the Argentine continental margin has a quasi bimodal statistical distribution. The main disadvantage in using routines based on Parker's expansion is that an average value of the topography is needed for the calculation and, as the margin has an abrupt change of the topography in the continental slope area, it causes a bimodal distribution. It is worth noticing that, as expected, the most important differences between both methods are located over the continental slope both in complex structures such as part of the shared margin, as well as in isolated points where there are contributions from short wavelength or rugged topography.Facultad de Ciencias Astronómicas y Geofísica

Dual laser excitation of a photochromic system: application to DODCI

A technique based on a combination of pump-and-probe fluorescence and absorption detection was developed in order to obtain the emission parameters of the pholoisomeric (P) species of dyes with noncompletely overlapped absorption spectra of P and the starting species (N ). Near total population transfer to the ground state of P was achieved using a continuous wave high fluence pump laser. A pulsed laser probed this population in its absorption region in such a way that the pulsed emission corresponded to fluorescence from P. Absorption measurements allowed us to follow the P population and to establish its relationship with pump fluence and wavelength. The direct monitoring of the P concentration increased the accuracy of the previously reported values for several photophysical parameters. Temperature dependent fluorescence quantum yield and lifetime, emission spectrum, and Arrhenius parameters of the nonradiative decay processes of P from 3,3' diethyloxa dicarbocyanine iodide (DODCI) are given. The mechanism for the direct transformation between N and P through the singlet excited states of DODCI is reevaluated

Dual laser excitation of a photochromic system: application to DODCI

A technique based on a combination of pump-and-probe fluorescence and absorption detection was developed in order to obtain the emission parameters of the pholoisomeric (P) species of dyes with noncompletely overlapped absorption spectra of P and the starting species (N ). Near total population transfer to the ground state of P was achieved using a continuous wave high fluence pump laser. A pulsed laser probed this population in its absorption region in such a way that the pulsed emission corresponded to fluorescence from P. Absorption measurements allowed us to follow the P population and to establish its relationship with pump fluence and wavelength. The direct monitoring of the P concentration increased the accuracy of the previously reported values for several photophysical parameters. Temperature dependent fluorescence quantum yield and lifetime, emission spectrum, and Arrhenius parameters of the nonradiative decay processes of P from 3,3' diethyloxa dicarbocyanine iodide (DODCI) are given. The mechanism for the direct transformation between N and P through the singlet excited states of DODCI is reevaluated.Centro de Investigaciones Óptica

Dual laser excitation of a photochromic system: application to DODCI

A technique based on a combination of pump-and-probe fluorescence and absorption detection was developed in order to obtain the emission parameters of the pholoisomeric (P) species of dyes with noncompletely overlapped absorption spectra of P and the starting species (N ). Near total population transfer to the ground state of P was achieved using a continuous wave high fluence pump laser. A pulsed laser probed this population in its absorption region in such a way that the pulsed emission corresponded to fluorescence from P. Absorption measurements allowed us to follow the P population and to establish its relationship with pump fluence and wavelength. The direct monitoring of the P concentration increased the accuracy of the previously reported values for several photophysical parameters. Temperature dependent fluorescence quantum yield and lifetime, emission spectrum, and Arrhenius parameters of the nonradiative decay processes of P from 3,3' diethyloxa dicarbocyanine iodide (DODCI) are given. The mechanism for the direct transformation between N and P through the singlet excited states of DODCI is reevaluated.Centro de Investigaciones Óptica

Dual laser excitation of a photochromic system: application to DODCI

A technique based on a combination of pump-and-probe fluorescence and absorption detection was developed in order to obtain the emission parameters of the pholoisomeric (P) species of dyes with noncompletely overlapped absorption spectra of P and the starting species (N ). Near total population transfer to the ground state of P was achieved using a continuous wave high fluence pump laser. A pulsed laser probed this population in its absorption region in such a way that the pulsed emission corresponded to fluorescence from P. Absorption measurements allowed us to follow the P population and to establish its relationship with pump fluence and wavelength. The direct monitoring of the P concentration increased the accuracy of the previously reported values for several photophysical parameters. Temperature dependent fluorescence quantum yield and lifetime, emission spectrum, and Arrhenius parameters of the nonradiative decay processes of P from 3,3' diethyloxa dicarbocyanine iodide (DODCI) are given. The mechanism for the direct transformation between N and P through the singlet excited states of DODCI is reevaluated.Centro de Investigaciones Óptica

Parameters that determine the wavelength of a passive mode-locked dye laser

We introduce a new stability criterion that should be added to previous theoretical models of passive mode locked lasers in order to predict emission wavelength, which is to require that the pulse spectrum reproduces itself after one transit. The CPM laser consisting of rhodamine 6G as gain medium and DODCI as saturable absorber is studied. The relative population balance of the fundamental and photoisoner species of the DODCI are computed as a function of the pulse energy and wavelength. The necessity of a spectral stability criterion follows from the dependence of the gain profile on the pulse parameters. Use of the criterion is shown to agree with previous experimental results, such as the red spectral region of emission and dependence of emission wavelength on absorber concentration. This criterion is expected to be an useful tool in order to select other dye combinations and predict the laser behavior. Parameters that determine the wavelength of a passive mode-locked dye laser

Photoacoustic characterization of phase transitions in amorphous metal alloys

In this work a pulsed laser photoacoustic technique is employed in amorphous alloys for the characterization of crystallization temperatures and the determination of the activation energies for the transitions. It is shown that the changes produced in the photoacoustic signal generated by low energy laser pulses (< 200 μJ), is a sensitive probe for detecting the crystallization of a metallic amorphous sample. A piezoelectric transducer attached to the sample by means of a glass substrate was used for the acoustic detection. The developed technique has the advantages of requiring a minimum amount of sample, with no special sample preparation or conditioning. In order to demonstrate the validity of the technique, it was applied to the study of the crystallization processes of the amorphous Mg-Zn alloy, comparing the result with respect to resistivity measurements

Reconstrucción de espectros de irradiancia solar global UV a partir de mediciones con radiómetro de banda angosta

La medición de la región ultravioleta (UV) de la radiación solar ha sido motivo de sumo interés desde la aparición del fenómeno de adelgazamiento global de la capa de ozono. Diferentes propuestas tecnológicas fueron utilizadas para tal fin, desde radiómetros de banda ancha, hasta los costosos espectrorradiómetros. Los radiómetros de ancho de banda moderado (típicamente 10 nm) con canales centrados en las regiones UVA y UVB, son una solución intermedia entre las dos anteriores y están ampliamente distribuidos. En este trabajo se describe un método para realizar la reconstrucción del espectro UV entre 290 y 400 nm a partir de las mediciones de un instrumento de este tipo y de la utilización conjunta de un modelo de transferencia radiativa. A partir de la reconstrucción del espectro solar UV en superficie con una resolución de 1 nm es posible monitorear la estabilidad de los distintos canales de los radiómetros a lo largo del tiempo, y también calcular diferentes subproductos, como la irradiancia eritémica y el índice UV. Se presentan resultados para instrumentos GUV de Biospherical Instruments Inc., instalados en el país. También se comparan los valores de la radiación biológicamente efectiva (irradiancia eritémica) calculada por este método con la medida directa de diferentes biómetros de la estación de sensado remoto que el CEILAP tiene instalado en el sitio SOLAR en la ciudad patagónica de Rio Gallegos.The measurement of ultraviolet (UV) solar radiation has been a subject of great interest since the emergence of the global depletion of the ozone layer phenomenon. Different technological proposals were used to this purpose, from broadband radiometers to expensive spectroradiometers. Moderate ubandwidth uradiometers u(typically u10 unm) uwith uchannels uon uregions uUVA uand uUVB, uare ua intermediate usolution ubetween uthe utwo previous instruments, and they are widely distributed. This paper describes a method to carry out the reconstruction of the UV spectrum between 290 and 400 nm from measurements of this kind of instrument and the joint use of a radiative transfer model. From the reconstruction of UV solar spectrum in surface with a resolution of 1 nm it is possible to monitor the stability of the various channels of the radiometers over time, and also to calculate different subproducts, as erythemical irradiance and UV index. The results for GUV instruments from Biospherical Instruments Inc. installed in the country are presented. The values of biologically effective radiation (erythemical irradiance) calculated by this method with direct measurement from different biometers CEILAP has installed in the SOLAR site in the Patagonian city of Rio Gallegos, are also compared