352 research outputs found
Seismogenesis in Central Apennines, Italy: an integrated analysis of minor earthquake sequences and structural data in the Amatrice-Campotosto area
We present a seismotectonic study of the Amatrice-Campotosto area (Central Italy) based on an integrated
analysis of minor earthquake sequences, geological data and crustal rheology. The area has been affected by
three small-magnitude seismic sequences: August 1992 (M=3.9), June 1994 (M=3.7) and October 1996
(M=4.0). The hypocentral locations and fault plane solutions of the 1996 sequence are based on original data;
the seismological features of the 1992 and 1994 sequences are summarised from literature. The active WSWdipping
Mt. Gorzano normal fault is interpreted as the common seismogenic structure for the three analysed
sequences. The mean state of stress obtained by inversion of focal mechanisms (WSW-ENE-trending deviatoric
tension) is comparable to that responsible for finite Quaternary displacement, showing that the stress field
has not changed since the onset of extensional tectonics. Available morphotectonic data integrated with original
structural data show that the Mt. Gorzano Fault extends for ~28 km along strike. The along-strike displacement
profile is typical of an isolated fault, without significant internal segmentation. The strong evidence
of late Quaternary activity in the southern part of the fault (with lower displacement gradient) is explained in
this work in terms of displacement profile readjustment within a fault unable to grow further laterally. The
depth distribution of seismicity and the crustal rheology yield a thickness of ~15 km for the brittle layer. An
area of ~530 km2 is estimated for the entire Mt. Gorzano Fault surface. In historical times, the northern portion
of the fault was probably activated during the 1639 Amatrice earthquake (I = X, M~ 6.3), but this is not the
largest event we expect on the fault. We propose that a large earthquake might activate the entire 28 km long
Mt. Gorzano Fault, with an expected Mmax up to 6.7
3D-in-2D Displays for ATC.
This paper reports on the efforts and accomplishments
of the 3D-in-2D Displays for ATC project at the end of Year 1.
We describe the invention of 10 novel 3D/2D visualisations that
were mostly implemented in the Augmented Reality ARToolkit.
These prototype implementations of visualisation and interaction
elements can be viewed on the accompanying video. We have
identified six candidate design concepts which we will further
research and develop. These designs correspond with the early
feasibility studies stage of maturity as defined by the NASA
Technology Readiness Level framework. We developed the
Combination Display Framework from a review of the literature,
and used it for analysing display designs in terms of display
technique used and how they are combined. The insights we
gained from this framework then guided our inventions and the
human-centered innovation process we use to iteratively invent.
Our designs are based on an understanding of user work
practices. We also developed a simple ATC simulator that we
used for rapid experimentation and evaluation of design ideas.
We expect that if this project continues, the effort in Year 2 and 3
will be focus on maturing the concepts and employment in a
operational laboratory settings
Modal Analysis and Coupling in Metal-Insulator-Metal Waveguides
This paper shows how to analyze plasmonic metal-insulator-metal waveguides
using the full modal structure of these guides. The analysis applies to all
frequencies, particularly including the near infrared and visible spectrum, and
to a wide range of sizes, including nanometallic structures. We use the
approach here specifically to analyze waveguide junctions. We show that the
full modal structure of the metal-insulator-metal (MIM) waveguides--which
consists of real and complex discrete eigenvalue spectra, as well as the
continuous spectrum--forms a complete basis set. We provide the derivation of
these modes using the techniques developed for Sturm-Liouville and generalized
eigenvalue equations. We demonstrate the need to include all parts of the
spectrum to have a complete set of basis vectors to describe scattering within
MIM waveguides with the mode-matching technique. We numerically compare the
mode-matching formulation with finite-difference frequency-domain analysis and
find very good agreement between the two for modal scattering at symmetric MIM
waveguide junctions. We touch upon the similarities between the underlying
mathematical structure of the MIM waveguide and the PT symmetric quantum
mechanical pseudo-Hermitian Hamiltonians. The rich set of modes that the MIM
waveguide supports forms a canonical example against which other more
complicated geometries can be compared. Our work here encompasses the microwave
results, but extends also to waveguides with real metals even at infrared and
optical frequencies.Comment: 17 pages, 13 figures, 2 tables, references expanded, typos fixed,
figures slightly modifie
Changing lenses to assess biodiversity: patterns of species richness in sub-Antarctic plants and implications for global conservation
Functional ecology of soil microbial communities along a glacier forefield in Tierra del Fuego (Chile)
A previously established chronosequence from Pia Glacier forefield in Tierra del Fuego (Chile) containing soils of different ages (from bare soils to forest ones) is analyzed. We used this chronosequence as framework to postulate that microbial successional development would be accompanied by changes in functionality. To test this, the GeoChip functional microarray was used to identify diversity of genes involved in microbial carbon and nitrogen metabolism, as well as other genes related to microbial stress response and biotic interactions. Changes in putative functionality generally reflected succession-related taxonomic composition of soil microbiota. Major shifts in carbon fixation and catabolism were observed, as well as major changes in nitrogen metabolism. At initial microbial dominated succession stages, microorganisms could be mainly involved in pathways that help to increase nutrient availability, while more complex microbial transformations such as denitrification and methanogenesis, and later degradation of complex organic substrates, could be more prevalent at vegetated successional states. Shifts in virus populations broadly reflected changes in microbial diversity. Conversely, stress response pathways appeared relatively well conserved for communities along the entire chronosequence. We conclude that nutrient utilization is likely the major driver of microbial succession in these soils. [Int Microbiol 19(3):161-173 (2016)]Keywords: Functional genes · antibiotic resistance · GeoChip microarray · primary succession · chronosequenc
Terahertz plasmons in coupled two-dimensional semiconductor resonators
Advances in theory are needed to match recent progress in measurements of coupled semiconductor resonators supporting terahertz plasmons. Here, we present a field-based model of plasmonic resonators that comprise gated and ungated two-dimensional electron systems. The model is compared to experimental measurements of a representative system, in which the interaction between the gated and ungated modes leads to a rich spectrum of hybridized resonances. A theoretical framework is thus established for the analysis and design of gated low-dimensional systems used as plasmonic resonators, underlining their potential application in the manipulation of terahertz frequency range signals
Tracking the coherent generation of polaron pairs in conjugated polymers
The optical excitation of organic semiconductors not only generates charge-neutral electron-hole pairs (excitons), but also charge-separated polaron pairs with high yield. The microscopic mechanisms underlying this charge separation have been debated for many years. Here we use ultrafast two-dimensional electronic spectroscopy to study the dynamics of polaron pair formation in a prototypical polymer thin film on a sub-20-fs time scale. We observe multi-period peak oscillations persisting for up to about 1 ps as distinct signatures of vibronic quantum coherence at room temperature. The measured two-dimensional spectra show pronounced peak splittings revealing that the elementary optical excitations of this polymer are hybridized exciton-polaron-pairs, strongly coupled to a dominant underdamped vibrational mode. Coherent vibronic coupling induces ultrafast polaron pair formation, accelerates the charge separation dynamics and makes it insensitive to disorder. These findings open up new perspectives for tailoring light-to-current conversion in organic materials
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