1,550 research outputs found
Phase asymmetry effect in longitudinal offset coupled resonator optical waveguides
We show that the implementation of the longitudinal displacement technique
for adjusting the coupling coefficients in microring waveguides is subject to a
phase asymmetry effect. This issue is shown to substantially alter the system
response in apodized filters and cannot be ignored in the design stage
Fast and slow light in zig-zag microring resonator chains
We analyze fast and slow light transmission in a zig-zag microring resonator
chain. This novel device permits the operation in both regimes. In the
superluminal case, a new ubiquitous light transmission effect is found whereby
the input optical pulse is reproduced in an almost simultaneous manner at the
various system outputs. When the input carrier is tuned to a different
frequency, the system permits to slow down the propagating optical signal.
Between these two extreme cases, the relative delay can be tuned within a broad
range
Proyecto de acondicionamiento de la carretera LV-9123 de Gavet de la Conca a Sant SernÃ
El presente proyecto tiene por objeto el acondicionamiento de la carretera LV-9123, en el tramo de 3.246,14 m
desde Gavet de la Conca hasta Sant SernÃ, mediante actuaciones de mejora del pavimento y del drenaje de la vÃa, además de la mejora de la seguridad de la vÃa en tramos concretos donde ésta es especialmente baja
Faint calcium-rich transient from the double-detonation of a carbon-oxygen white dwarf star
We have computed a three-dimensional hydrodynamic simulation of the merger
between a massive () helium white dwarf (He WD) and a low-mass
() carbon-oxygen white dwarf (CO WD). Despite the low mass of the
primary, the merger triggers a thermonuclear explosion as a result of a double
detonation, producing a faint transient and leaving no remnant behind. This
type of event could also take place during common-envelope mergers whenever the
companion is a CO WD and the core of the giant star has a sufficiently large He
mass. The spectra show strong Ca lines throughout the first few weeks after the
explosion. The explosion only yields of Ni, resulting
in a low-luminosity SN Ia-like lightcurve that resembles the Ca-rich transients
within this broad class of objects, with a peak magnitude of mag and a rather slow decline rate of mag. Both, its lightcurve-shape and spectral
appearance, resemble the appearance of Ca-rich transients, suggesting such
mergers as a possible progenitor scenario for this class of events.Comment: Submitted to A&A letters, posted on ArXiv after positive referee
report. 7 pages, 4 figure
The origin of the Acheulean: the 1.7 million-year-old site of FLK West, Olduvai Gorge (Tanzania)
The appearance of the Acheulean is one of the hallmarks of human evolution. It represents the
emergence of a complex behavior, expressed in the recurrent manufacture of large-sized tools, with
standardized forms, implying more advance forethought and planning by hominins than those required
by the precedent Oldowan technology. The earliest known evidence of this technology dates back to
c. 1.7 Ma. and is limited to two sites (Kokiselei [Kenya] and Konso [Ethiopia]), both of which lack fauna.
The functionality of these earliest Acheulean assemblages remains unknown. Here we present the
discovery of another early Acheulean site also dating to c. 1.7 Ma from Olduvai Gorge. This site provides
evidence of the earliest steps in developing the Acheulean technology and is the oldest Acheulean site in
which stone tools occur spatially and functionally associated with the exploitation of fauna. Simple and
elaborate large-cutting tools (LCT) and handaxes co-exist at FLK West, showing that complex cognition
was present from the earliest stages of the Acheulean. Here we provide a detailed technological study
and evidence of the use of these tools on the butchery and consumption of fauna, probably by early
Homo erectus sensu lato
Transient analysis of a nonlinear fiber ring resonator
In this letter we study the transient behavior of a nonlinear fiber ring resonator operating both as an optical bistable and as a differential amplifier. The speed of response of the structure is investigated, and some general considerations on the performance of these kinds of devices are presented.Peer Reviewe
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