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Terremotos , Geología/normas , Difusión de la Información , Colorado , Agencias Internacionales , TiempoRESUMEN
Continuous developments in inorganic mass spectrometry techniques, including a combination of an inductively coupled plasma ion source and a magnetic sector-based mass spectrometer equipped with a multiple-collector array, have revolutionized the precision of isotope ratio measurements, and applications of inorganic mass spectrometry for biochemistry, geochemistry, and marine chemistry are beginning to appear on the horizon. Series of pioneering studies have revealed that natural stable isotope fractionations of many elements heavier than S (e.g., Fe, Cu, Zn, Sr, Ce, Nd, Mo, Cd, W, Tl, and U) are common on Earth, and it had been widely recognized that most physicochemical reactions or biochemical processes induce mass-dependent isotope fractionation. The variations in isotope ratios of the heavy elements can provide new insights into past and present biochemical and geochemical processes. To achieve this, the analytical community is actively solving problems such as spectral interference, mass discrimination drift, chemical separation and purification, and reduction of the contamination of analytes. This article describes data calibration and standardization protocols to allow interlaboratory comparisons or to maintain traceability of data, and basic principles of isotope fractionation in nature, together with high-selectivity and high-yield chemical separation and purification techniques for stable isotope studies.
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Isótopos/análisis , Espectrometría de Masas/métodos , Metales Pesados/análisis , Animales , Fraccionamiento Químico/instrumentación , Fraccionamiento Químico/métodos , Geología/instrumentación , Geología/métodos , Geología/normas , Humanos , Espectrometría de Masas/instrumentación , Espectrometría de Masas/normas , Metabolómica/instrumentación , Metabolómica/métodos , Metabolómica/normasAsunto(s)
Terremotos , Geología/métodos , Geología/normas , Códigos de Edificación , Terremotos/mortalidad , Geología/ética , Humanos , Italia , Factores de RiesgoAsunto(s)
Ecología/métodos , Ingeniería/métodos , Geología/métodos , Calentamiento Global/prevención & control , Guías como Asunto , Meteorología/métodos , Ecología/ética , Ecología/normas , Ingeniería/ética , Ingeniería/normas , Estudios de Evaluación como Asunto , Miedo , Geología/ética , Geología/normas , Meteorología/ética , Meteorología/normasRESUMEN
The surface velocity of sand inside a large PVC container, induced by the sound pressure from either a large loudspeaker radiating into an inverted cone and pipe or a Bruel and Kjaer point source loudspeaker mounted with its axis vertical, has been measured using accelerometers. Results of white noise and stepped frequency excitation are presented. Without any buried object the mass loading of an accelerometer creates resonances in the spectral ratio of sand surface velocity to incident acoustic pressure, i.e., the acoustic-to-seismic (A/S) admittance spectra. The A/S responses above a buried compliant object are larger and distinctive. The linear A/S admittance spectra in the presence of a buried electronic components box have been studied as a function of burial depth and sand state. The nonlinear responses above the buried box have been studied as a function of depth, sand state, and amplitude. Predictions of a modified one-dimensional lumped parameter model have been found to be consistent with the observed nonlinear responses. Also the modified model has been used to explain features of the A/S responses observed when using an accelerometer without any buried object.
Asunto(s)
Aceleración , Acústica/instrumentación , Geología/instrumentación , Ruido , Cloruro de Polivinilo , Dióxido de Silicio , Amplificadores Electrónicos , Calibración , Geología/normas , Modelos Lineales , Modelos Teóricos , Movimiento (Física) , Dinámicas no Lineales , Presión , Espectrografía del Sonido , Factores de Tiempo , VibraciónAsunto(s)
Arqueología , Cronología como Asunto , Extinción Biológica , Geología , Paleontología , Arqueología/historia , Arqueología/instrumentación , Arqueología/métodos , Arqueología/normas , Arqueología/tendencias , Evolución Biológica , Fósiles , Geología/historia , Geología/instrumentación , Geología/métodos , Geología/normas , Geología/tendencias , Historia del Siglo XIX , Historia del Siglo XX , Paleontología/historia , Paleontología/instrumentación , Paleontología/métodos , Paleontología/normas , Paleontología/tendenciasRESUMEN
Large systematic discrepancies currently exist among the carbon data reported for oceanic basalts by different laboratories. These discrepancies are likely attributable both to non-uniform criteria for the removal of carbon contamination from the samples, and to systematic errors in analytical procedures. In order to solve these problems, investigators must agree upon effective criteria for the removal of carbon contamination, and they must create an accurately calibrated set of balsaltic glass carbon standards.