RESUMEN
Single crystals of Ca(4)Fe(2)Mn(0.5)Ti(0.5)O(9) have been synthesized using a flux method. The structural characterization using single-crystal X-ray diffraction revealed the space group Amma and unit-cell dimensions of a = 5.3510 (6), b = 26.669 (3), c = 5.4914 (6) Å. The structure is isotypic with Sr(3)NdFe(3)O(9) [Barrier et al. (2005). Chem. Mater. 17, 6619-6623] and exhibits separated brownmillerite-type layers. One-dimensional diffuse scattering shows that the unit cell is doubled along c by alternating the intra-layer order of tetrahedral chains, causing stacking faults along the b direction. A computer simulation was performed, proving that the observed intensity variations along the diffuse scattering rods originates from two different local structures depending on the configuration of the tetrahedral chains. Selected-area electron diffraction experiments exhibit well ordered regions characterized by satellite reflections corresponding to two different superstructures. Both superstructures can be described using the superspace group A2(1)/m(0ßγ)0s, with γ = 0.5 and ß ≃ 0.27 or ß = 0.
RESUMEN
OBJECTIVE: To decrease postoperative morbidity associated with radical hysterectomy Rutledge type III, we identified the parasympathetic innervation of the bladder in the cardinal ligament. METHODS: During laparoscopic dissection of the cardinal ligament, we used 7x magnification on 38 consecutive patients with cervical cancer stages IB1 to IIIA with high risk for parametrial involvement when we performed laparoscopy-assisted radical vaginal hysterectomy type III between August 1997 and January 1999. RESULTS: The middle rectal artery was identified as a landmark separating the vascular from the neural part of the cardinal ligament. The neural part was shown to contain the splanchnic pelvic nerves which anastomose with the pelvic plexus. Following preservation of these neural structures all patients were able to void their bladder spontaneously. Following nerve-sparing technique, patients regained bladder function significantly quicker compared with a control group (n = 28) in which the neural part of the cardinal ligament had not been preserved: suprapubic drainage 11.2 days versus 21.4 days (P = 0.0007). CONCLUSION: Using the middle rectal artery as a landmark the neural part of the cardinal ligament can be preserved, resulting in preservation of the motor function of the bladder.
Asunto(s)
Histerectomía Vaginal/métodos , Laparoscopía/métodos , Vejiga Urinaria/inervación , Neoplasias del Cuello Uterino/cirugía , Femenino , Humanos , Escisión del Ganglio Linfático/métodos , Neuronas Motoras/fisiología , Sistema Nervioso Parasimpático/anatomía & histología , Sistema Nervioso Parasimpático/cirugía , Estudios Prospectivos , Nervios Esplácnicos/cirugía , Vejiga Urinaria/fisiologíaRESUMEN
Six sesquiterpene lactones, two new (3 and 6) and four known (1, 2, 4 and 5) were isolated from the leaves of the Mexican Neurolaena macrocephala (Asteraceae). The furanoheliangolide 6, containing 4beta,5-dihydro-9alpha-hydroxy-atripliciolide as basic structure, was found for the first time in nature. The chemotaxonomic importance of this phytochemical work is discussed.
Asunto(s)
Asteraceae/química , Plantas Medicinales/química , Sesquiterpenos/química , Lactonas/química , Espectroscopía de Resonancia Magnética , México , Modelos Moleculares , Conformación Molecular , Estructura Molecular , Hojas de la Planta/química , Sesquiterpenos/aislamiento & purificaciónRESUMEN
The possibility that subjective contours are an artifact of brightness contrast was explored. In one experiment, inducing luminance was found to have different effects on the clarity of subjective contours and the magnitude of brightness contrast. The results of a second experiment indicated that differences of luminance in a stimulus display are necessary for subjective contours to be sustained, whereas chromatic differences are not. It is concluded that subjective contour and brightness contrast are distinct perceptual phenomena but share a dependency on the processing of edge information transmitted through the achromatic channels of the visual system.