1,721,059 research outputs found
Fluctuations of Atmospheric Pressure and the Sound of Underground Karst Systems: The Antro del Corchia Case (Apuane Alps, Italy)
Full text linkMountains that contain subterranean voids can inhale fresh and clean air, and their breath is a fascinating natural phenomenon that speleologists know very well. Air flow through the entrances of underground systems is also an interesting geophysical problem. Basically, it is caused by temperature and pressure gradients between the internal and external atmospheres, but the dynamic interplay between these two driving forces is still not well understood. Our contribution dissects the physics of underground winds. Wind velocity, internal and external temperature and pressure have been measured synchronously at two entrances of a vast (∼64 km) underground system beneath the Mount Corchia, Apuane Alps, Italy. The data shows that, within time scales of minutes to days, pressure fluctuations of the external atmosphere primarily force air to flow underground, whereas temperature gradients play only a minor role. We modeled the cave as a system that takes the external atmospheric pressure as the input signal and outputs wind from its entrances. This wind, in turn, contains information about the system’s response, and hence on the structure of the subterranean voids. This information can be extracted using standard signal processing techniques and by using deconvolution methods we identify the same infrasound resonances in signals sampled at both entrances. These are the characteristic frequencies of the cave, and by using the Helmholtz resonance formalism it can be estimated that the explored volume of this important underground system is less than half of its probable real extension
L'eccezionale ambiente della Cueva de los Cristales, Miniera di Naica, Messico: problemi genetici ed esplorativi
No full textChanges in fish assemblages of a previously highly polluted river: The role of environmental recovery and alien fish invasion in the Bormida River (Italy)
No full textResponse of macroinvertebrate and diatom communities to human-induced physical alteration in mountain streams
No full textMonitoraggio biologico di sistemi fluviali in alta quota: un’esperienza nel gruppo del Monte Bianco
No full text
El proyecto Naica (Chihuahua, México)
No full textEl objetivo del proyecto es realizar un conjunto de investigaciones multidisciplinarias que cubra los diferentes campos de interés de las cuevas de Naica y que permita su conservación. En un principio, sin embargo, por el ambiente infernal y la presencia de los cristales se requirió la planeación y el desarrollo de materiales y tecnologías específicas, como los trajes con sistema de refrigeración (fig. 5) para permitir un acceso seguro y prolongado a los investigadores de las diferentes disciplinas Las preguntas a las cuales el proyecto intentará contestar son muchas, entre las cuales las más importantes son seguramente estas:
¿Cómo y por qué se formaron estos cristales gigantes?
¿Hace cuánto tiempo?
¿Hay vida en este ambiente límite, que parece extraterrestre?
Si se llegaran a encontrar formas de vida, ¿tuvieron algún papel en la formación de los
cristales y las mineralizaciones circundantes?
El hombre, sin quererlo, interrumpió el equilibrio milenario entre las aguas profundas y
las rocas que generaron estas maravillas: ¿qué está sucediendo ahora?
¿Cómo varía el clima de las cuevas en el tiempo?
¿Son estables los cristales?
¿Cuánto tiempo durarán?
¿Cómo se comporta la fisiología humana en ambientes extremos como estos
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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