26 research outputs found
The Economic Archaeology of Roman Economic Performance
Recent years have witnessed a paradigm shift in the study of the Roman economy. Methodologically modern economic analysis is now far more acceptable than it once was, and archaeology has become the major source of empirical data for many questions. On the substantive side there is now a far clearer appreciation of the major changes that the Roman economy underwent, with substantial growth of population and aggregate production and even some improvements in standard of living, but followed by equally dramatic decline. This economic success was not limited to the imperial core, but also extended to the provinces
General observation of n-type field-effect behaviour in organic semiconductors
10.1038/nature03376Nature4347030194-199NATU
39 Years of Geochemical Monitoring of Laguna Caliente Crater Lake, Poás: Patterns from the Past as Keys for the Future
Since 1978 water chemistry of the Laguna
Caliente crater lake has been used to monitor
volcanic activity at Poás, Costa Rica, making
it arguably the best studied hyper-acidic crater
lake on Earth. During these 39 years, three of water of Laguna Caliente, independent on
previous deterministic research and resulting
conceptual models. Common patterns of chemical parameters in relation with phreatic
eruptive activity for the period 1978–Septem-
ber 2014 are sought, applying the objective
statistical method of Pattern Recognition. This
resulted in the definition of the strongest
precursory signals and their respective thresh-
olds. Numerical outcomes often confirm find-
ings based on geochemical models (e.g. SO4,
SO4/Cl and pH are strong monitoring param-
eters). However, some surprising parameters
(opposite behavior of Mg/Cl ratios, decreases
in Ca and Mg concentrations, increasing
Al/Mg ratios) still need a geochemical expla-
nation and should be a focus for future
research strategies. The obtained parameters
and thresholds were retrospectively applied
for the “test period” of the Pattern Recognition
method (November 2014–February 2016).
This test provided hints that suggested that
eruptive activity at Poás was not yet over,
despite apparent quiescence in early 2016.
Indeed, after new phreatic eruptions since
May 2016, the 2006–2016 phreatic eruptive
cycle culminated in phreatomagmatic activity
in April 2017. We conclude that evaluating
time series of chemical composition of crater
lakes framed in the Pattern Recognition
method can be a useful monitoring approach.
Moreover, increased sampling frequency can
provide more details and more adequate
phases of unrest occurred, manifested through
frequent phreatic eruptions, with each a dura-
tion of several years to over a decade (1978–
1980, 1986–1996, 2006–2016). We here
present a novel technique to deal with the
long time series of the chemical compositionPublished213-2334V. Processi pre-eruttiv