2,311 research outputs found
Tunable ring resonator filter for OFDM Transmission systems
A novel tunable filter is theoretically demonstrated. It is based on a ring resonator with an amplifier and a noise filter in the loop. This optoelectronic
device has potential as a high-sensitivity receiver and as a tunable demultiplexer in OFDM transmission systems.Publicad
Meteorización de las granulitas de Cabo Ortegal
[Resumen] Se realiza el estudio químico y mineralógico del proceso de alteración, en medios sustractivos, de las granuli tas de Cabo Ortegal, la precipi tación media anual supera los 1.300 mm. y las temperaturas medias mensuales extremas son 23ºC y 4,7ºC. Durante el proceso de meteorizaciór se origina una fuerte pérdida de Ca, Na y Mg y,en menor proporción, de Si con acumulación relativa de Fe y Al. Como productos de alteración aparecen filosilicatos 1:1 dioctaédricos, gibbsita, oxihidróxidos de hierro y micas y cloritas degradadas. La edafogénesis es de tipo fermonosialítico con una tendencia ferralítica, al menos en sus fases iniciales.[Abstract] This paper is a chemical and mineralogical study about the weathering process, in subtr&ctive environments, of the granul i tes in Cabo Ortegal. The mean annual precipitation is over 1.300 mm. and the mean monthly extreme temperatures are 23ºC and 4,7ºC . In the process of weathering there is an intense 10S8 of Ca, Na and Mg and, in a minar level , of Si, with a relative accumulation of Fe and Al. Proqucts of the weathering are 1: 1 dioctahedral phyllosilicates, gibbsi teiron oxyhydroxides and degraded micas and chlorites. The pedogenesis is of fermonosialli tic type wi th a ferrallitic tendence, in the first phases at least
Lipoma intraóseo en fémur proximal.
Se presenta un caso de una mujer de 74 años de edad con antecedente doloroso de la cadera izquierda de una año de evolución. En el estudio radiológico se aprecia una lesión quística en zona proximal del fémur del lado izquierdo asociada a signos de coxartrosis. Se decide legrar la lesión e implantar una prótesis total de cadera cementada, en el estudio histológico se encuentra un lipoma intraóseo sin signos de malignidad. A los dos años de evolución la paciente se encuentra asintomática y sin reaparición de la lesión ósea. Se presenta el caso, se establece un diagnóstico diferencial y se revisa la bibliografía dada la influencia de aparición de esta patología tumoral ósea.We presented a case of a patient seventy and four
years old with a painful left hip during the last 12 months. On
the x-ray exploration, appear a quistic lesion, localizated on
the proximal femur and with arthrosis signs of the coxofemo-
ral joint. We indicated a total hip arthroplasty, cemented, du-
ring the surgery the lesion is legrated, and the histologic study
reveal a intraosseus lipoma, without maling signs. At two ye-
ars, the patient is asintomatic, and no indicius of the femoral
tumor. We presented this case, the intraosseus lipoma, ma-
king the diferential diagnosis and revised the bibliografy of
this rare osseous tumor
Transient Propagation and Scattering of Quasi-Rayleigh Waves in Plates: Quantitative comparison between Pulsed TV-Holography Measurements and FC(Gram) elastodynamic simulations
We study the scattering of transient, high-frequency, narrow-band
quasi-Rayleigh elastic waves by through-thickness holes in aluminum plates, in
the framework of ultrasonic nondestructive testing (NDT) based on full-field
optical detection. Sequences of the instantaneous two-dimensional (2-D)
out-of-plane displacement scattering maps are measured with a self-developed
PTVH system. The corresponding simulated sequences are obtained by means of an
FC(Gram) elastodynamic solver introduced recently, which implements a full
three-dimensional (3D) vector formulation of the direct linear-elasticity
scattering problem. A detailed quantitative comparison between these
experimental and numerical sequences, which is presented here for the first
time, shows very good agreement both in the amplitude and the phase of the
acoustic field in the forward, lateral and backscattering areas. It is thus
suggested that the combination of the PTVH system and the FC(Gram)
elastodynamic solver provides an effective ultrasonic inspection tool for
plate-like structures, with a significant potential for ultrasonic NDT
applications.Comment: 46 pages, 16 figures, corresponding author Jos\'e Carlos
L\'opez-V\'azquez, [email protected]. Changes: 1st, 4th, 5th paragraphs
(intro), 3rd, 4th paragraphs (sec. 4); [59-60] cited only in appendixes; old
ref. [52] removed; misprints corrected in the uncertainty of c_L (subsec.
3.1), citation to fig. 10 (sec. 4), size of images (caption fig.15);
reference to Lam\'e constants removed in subsec. 3.
The physical structure of the point-symmetric and quadrupolar planetary nebula NGC 6309
We analyse the point-symmetric planetary nebula NGC 6309 in terms of its
three-dimensional structure and of internal variations of the physical
conditions to deduce the physical processes involved in its formation. We used
VLA-D 3.6-cm continuum, ground-based, and HST-archive imaging as well as long
slit high- and low-dispersion spectroscopy. The low-dispersion spectra indicate
a high excitation nebula, with low to medium variations of its internal
physical conditions. In the optical images, the point-symmetric knots show a
lack of [NII] emission as compared with similar features previously known in
other PNe. A rich internal structure of the central region is seen in the HST
images, resembling a deformed torus. Long slit high-dispersion spectra reveal a
complex kinematics in the central region. The spectral line profiles from the
external regions of NGC 6309 indicate expanding lobes (~40 km/s) as those
generally found in bipolar nebulae. Finally, we have found evidence for the
presence of a faint halo, possibly related to the envelope of the AGB-star
progenitor. Our data indicate that NGC 6309 is a quadrupolar nebula with two
pairs of bipolar lobes whose axes are oriented PA=40 and PA=76. Equatorial and
polar velocities for these two pairs of lobes are 29 and 86 km/s for the
bipolar system at PA=40 and 25 and 75 km/s for the bipolar system at PA=76.
There is also a central torus that is expanding at 25 km/s. Kinematical age for
all these structures is around 3700 to 4000 yr. We conclude that NGC 6309 was
formed by a set of well-collimated bipolar outflows (jets), which were ejected
in the initial stages of its formation as a planetary nebula. These jets carved
the bipolar lobes in the previous AGB wind and their remnants are now observed
as the point-symmetric knots tracing the edges of the lobes.Comment: To be published in Astronomy & Astrophysics; 11 pages, 8 figures, 4
table
Sub-arcsecond Morphology of Planetary Nebulae
Planetary nebulae (PNe) can be roughly categorized into several broad
morphological classes. The high quality images of PNe acquired in recent years,
however, have revealed a wealth of fine structures that preclude simplistic
models for their formation. Here we present narrow-band, sub-arcsecond images
of a sample of relatively large PNe that illustrate the complexity and variety
of small-scale structures. This is especially true for bipolar PNe, for which
the images reveal multi-polar ejections and, in some cases, suggest turbulent
gas motions. Our images also reveal the presence or signs of jet-like outflows
in several objects in which this kind of component has not been previously
reported.Comment: 7 pages, 7 figures, Accepted for publication in PAS
Detection of a multi-shell planetary nebula around the hot subdwarf O-type star 2MASS J19310888+4324577
(Abridged) The origin of hot subdwarf O-type stars (sdOs) remains unclear
since their discovery in 1947. Among others, a post-Asymptotic Giant Branch
(post-AGB) origin is possible for a fraction of sdOs. We are involved in a
comprehensive ongoing study to search for and to analyze planetary nebulae
(PNe) around sdOs with the aim of establishing the fraction and properties of
sdOs with a post-AGB origin. We use deep Halpha and [OIII] images of sdOs to
detect nebular emission and intermediate resolution, long-slit optical
spectroscopy of the detected nebulae and their sdO central stars. These data
are complemented with other observations for further analysis of the detected
nebulae. We report the detection of an extremely faint, complex PN around 2MASS
J19310888+4324577 (2M1931+4324), a star classified as sdO in a binary system.
The PN shows a bipolar and an elliptical shell, whose major axes are oriented
perpendicular to each other, and high-excitation structures outside the two
shells. WISE archive images show faint, extended emission at 12 and 22 microns
in the inner nebular regions. The internal nebular kinematics is consistent
with a bipolar and a cylindrical/ellipsoidal shell, in both cases with the main
axis mainly perpendicular to the line of sight. The nebular spectrum only
exhibits Halpha, Hbeta and [OIII]4959,5007 emission lines, but suggests a very
low-excitation ([OIII]/Hbeta = 1.5), in strong contrast with the absence of
low-excitation emission lines. The spectrum of 2M1931+4324 presents narrow,
ionized helium absorptions that confirm the previous sdO classification and
suggest an effective temperature >= 60000 K. The binary nature of 2M1931+4324,
its association with a complex PN, and several properties of the system provide
strong support for the idea that binary central stars are a crucial ingredient
in the formation of complex PNe.Comment: 8 pages, 7 figures, accepted in Astronomy and Astrophysic
Numerical modeling and measurement by pulsed television holography of ultrasonic displacement maps in plates with through-thickness defects
We present a novel numerical modeling of ultrasonic Lamb and Rayleigh wave propagation and scattering by through-thickness defects like holes and slots in homogeneous plates, and its experimental verification in both near and far field by a self-developed pulsed TV holography system. In contrast to rigorous vectorial formulation of elasticity theory, our model is based on the 2-D scalar wave equation over the plate surface, with specific boundary conditions in the defects and plate edges. The experimental data include complex amplitude maps of the out-of-plane displacements of the plate surface, obtained by a two-step spatiotemporal Fourier transform method. We find a fair match between the numerical and experimental results, which allows for quantitative characterization of the defects
Cyanobacterial diversity in extreme environments in Baja California, Mexico: a polyphasic study
Cyanobacterial diversity from two geographical areas of Baja California Sur, Mexico, were studied: Bahia Concepcion, and Ensenada de Aripez. The sites included hypersaline ecosystems, sea bottom, hydrothermal springs, and a shrimp farm. In this report we describe four new morphotypes, two are marine epilithic from Bahia Concepcion, Dermocarpa sp. and Hyella sp. The third, Geitlerinema sp., occurs in thermal springs and in shrimp ponds, and the fourth, Tychonema sp., is from a shrimp pond. The partial sequences of the 16S rRNA genes and the phylogenetic relationship of four cyanobacterial strains (Synechococcus cf. elongatus, Leptolyngbya cf. thermalis, Leptolyngbya sp., and Geitlerinema sp.) are alsopresented. Polyphasic studies that include the combination of light microscopy, cultures and the comparative analysis of 16S rRNA gene sequences provide the most powerful approach currently available to establish the diversity of these oxygenic photosynthetic microorganisms in culture and in nature
La técnica de Spaso para reducción de la luxación anterior de hombro.
Hemos revisado retrospectivamente los pacientes con luxación anterior de hombro que hemos tratado con la maniobra de reducción conocida como la técnica de Spaso. Hemos evaluado a 23 pacientes con luxación glenohumeral antero-inferior. En diecinueve casos era el primer episodio de luxación, mientras que cuatro casos correspondían a luxación recidivante. En todos los pacientes, menos en dos casos, se pudo conseguir la reducción de manera sencilla e indolora sin necesidad de medicación.
La técnica consiste en disponer al paciente en decúbito supino, se coloca el miembro superior afectado, en extensión completa del codo y dirigido al cenit, se realiza tracción suave mientras se realiza una rotación externa del miembro. Presentamos esta técnica dada su sencillez, su fiabilidad, su reproducibilidad y su baja tasa de complicaciones.We have reviewed retrospectively a group of
patients with previous traumatic dislocation of shoulder trea-
ted with of Spaso maneuver. We have evaluated 23 patients
with antero-inferior glenohumeral dislocation. In nineteen
cases it was the first episode of dislocation, whereas four
cases refered recurrent instability. In all patients, except in
two cases, the reduction was simple and painless with no
need of medication. The Spaso technique consists of arran-
ging the patient in supine position, with the affected superior
member, in complete extension of elbow, to the cenit, while
traction is exerced, with mild external rotation of the arm. We
presented this technique that we consider simple, safe and
reproductible with a low rate of complications
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