974 research outputs found
Different kinds of long-term variability from Cygnus X-1
We present a study of the long-term variability of Cyg X-1 using data from
the RXTE/ASM and the RXTE/PCA during the time between the two soft states of
1996 and 2001/2002. This period has been characterized by many short ASM
flaring episodes which we have identified as "failed state transitions". The
150 d period which has been seen before and shortly after the 1996 soft state
is not obviously present in the ASM rate during most of this time. Applying
selection criteria from our pointed RXTE/PCA observations to exclude the
flaring episodes we show that the 150 d period can indeed still be
significantly detected in the hard state. Furthermore, while the ~420 d
timescale associated with the flaring is reduced in the selected hard state
count rate, it is still pronounced in the temporal evolution of the
corresponding hardness ratios. The Ryle radio flux is also consistent with the
150 d period being present but distorted during this time.Comment: 4 pages, 6 figures, to appear in Proceedings of "X-ray Timing 2003:
Rossi and Beyond", ed. P. Kaaret, F.K. Lamb, & J.H. Swan
Spontaneous symmetry breaking as a resource for noncritically squeezed light
In the last years we have proposed the use of the mechanism of spontaneous
symmetry breaking with the purpose of generating perfect quadrature squeezing.
Here we review previous work dealing with spatial (translational and
rotational) symmetries, both on optical parametric oscillators and four-wave
mixing cavities, as well as present new results. We then extend the phenomenon
to the polarization state of the signal field, hence introducing spontaneous
polarization symmetry breaking. Finally we propose a Jaynes-Cummings model in
which the phenomenon can be investigated at the single-photon-pair level in a
non-dissipative case, with the purpose of understanding it from a most
fundamental point of view.Comment: Review for the proceedings of SPIE Photonics Europe. 11 pages, 5
figures
Fisiopatología de los Cuerpos Libres Intraarticulares : estudio Experimental
La cubierta cartilaginosa de los cuerpos libres intraarticulares tiene un origen
no bien conocido. Se ha realizado un estudio experimental en conejos, liberando fragmentos osteocondrales
en la cavidad articular de la rodilla, estudiando sus cambios histológicos desde la
primera semana hasta el año. En todos los casos los fragmentos osteocondrales se observaron
adheridos a la membrana sinovial. Hubo una remodelación progresiva del componente óseo y
cartilaginoso, cubriéndose todo el fragmento de una cubierta fibrocartilaginosa, reabsorbiéndose
el hueso central y formándose nuevo hueso en la porción periférica debajo del fibrocartí-
lago. Todos los cambios tisulares dependieron de la actividad de la membrana sinovial. No pudo
demostrarse crecimiento del cartílago articular.It is not well known the origin of the cartilaginous outer layer of the
intrarticular loose bodies. An experimental study has been carried out on rabbits
loosening out osteochondral fragments into the articular cavity of the kne e joint and
studying their histological changes between the first week and the first year. The osteochondral
fragments wer e found adhered to the synovial membrane in all cases.
A proggressive remodeling tood place within the osseous and cartilaginous components,
the whole fragment became covered by a fibrocartilaginous covering, the
central bone was reabsorbed and new bone was formed at the peripheral portion
unde r fibrocartilage. All tissue change s wer e dependent on synovial membrane
activity. Growth of articular cartilage could not be demonstrated
Cicatrización del fibrocartílago meniscal de la Rodilla : estudio Experimental
Para estudiar la cicatrización de las lesiones meniscales se ha realizado un estudio
experimental en conejos. Se han practicado tres tipos de lesiones en el menisco, transversal,
longitudinal parameniscal y longitudinal interna alejeda del paramenisco. Posteriormente
el defecto creado era reparado mediante puntos sueltos con material reabsorvible.
Se ha estudiado el fenómeno de cicatrización desde el punto de vista histológico desde la
semana a los tres meses. Los resultados muestran que la cicatrización es fundamentalmente
extrínseca a partir de la capacidad plástica de la membrana sinovial. Las heridas longitudinales
parameniscales cicatrizaron sin dificultad, las transversales casi en toda su anchura y las
longitudinales en zona avascular cicatrizaron principalmente en su porción anterior gracias a
la invasión de sinovial hiperplásica desde la inserción tibial del ligamento cruzado anterior.To study the healing of meniscal tears, the authors hav e carried out
an experimental work in rabbits. They performed three types of tears in the internal
menisci, radial, peripheral longitudinal (in the parameniscal zone) and longitudinal
within of the parameniscus. The menisci were reparated by suture with
absorbible material.
The healing phenomenon has been histologically studied from the first wee k to
three months after. The results showed that the cicatrization is mainly extrinsic by
the plastic capacity of sinovial membrane. The longitudinal tears in the parameniscus
heal without difficulty, the transversal tears almost in their whol e width and the
longitudinal tears at the avascular zone healed principally in the anterior portion
by the invasion of hyperplasic sinovial from the tibial insertion of the anterior cruciate
ligament
Fibrocartílago meniscal como biomaterial de sustitución en los Defectos Osteocondrales. Estudio experimental en el conejo con injertos homólogos
Los autores presentan un estudio experimental en el cual han empleado homoinjertos
de fibrocartílago meniscal, para reparar defectos osteocondrales localizados
en zona de carga, del cóndilo medial de la rodilla del conejo.
Han sido estudiados 33 animales, realizando un estudio histológico, con periodos
de evolución comprendidos entre una semana y 22 meses.
Los homoinjertos meniscales parecen ser capaces de restaurar una superficie
articular funcional. Conservan su estructura y celularidad a lo largo de toda la
experiencia consiguiendo un perfecto anclaje al lecho óseo, adaptándose a la carga
y sin producir cambios en el cartílago articular vecino.
No se han producido rechazos.The authors report on an experimental study, employing meniscal fibrocartilage
homo grafts to repair osteochondral defects in the weightbearing
area of medial condile of rabbit knee.
Thirty-three animals were studied by histological means for periods of
one week to 22 months.
The meniscal fibrocartilage homograft appeared capable of restoring
a functional articular surface, maintaining its entire histological structure
and celularity throughout the experiment, obtaining a perfect union
with the bone tissue, adapting to the weightbearing and not modifying the
neighboring articular surface. No evidence of rejection was observed
- …