RESUMEN
(57)Fe Mössbauer spectroscopy has been used to investigate the structural and magnetic phase transitions of CaFe2As2 (T(N) = 173 K) single crystals. For this compound we found that V(ZZ) is positive and parallel to the c-axis of the tetragonal structure. For CaFe2As2 a magnetic hyperfine field B(hf) was observed at the (57)Fe nucleus below T(N) ~173 K. Analysis of the temperature dependence of B(hf) data using the Bean-Rodbell model shows that the Fe spins undergo a first-order magnetic transition at ~173 K. A collinear antiferromagnetic structure is established below this temperature with the Fe spin lying in the (a, b) plane. Below T(N) the paramagnetic fraction of Fe decreases down to 150 K and for lower temperatures all the Fe spins are magnetically ordered.
RESUMEN
The aim of this paper is to find a relationship between alternating sequential filters (ASF) and the morphological sampling theorem (MST) developed by Haralick et al. (1987). The motivation behind this approach is to take advantage of the computational efficiency offered by the MST to implement morphological operations. First, we show alternative proofs for opening and closing in the sampled and unsampled domain using the basis functions. These proofs are important because they show that it possible to obtain any level of a morphological pyramid in one step rather than the traditional two-step procedure. This decomposition is then used to show the relationship of the open-closing in the sampled and unsampled domain. An upper and a lower bound, for the above relationships, are presented. Under certain circumstances, an equivalence is shown for open-closing between the sampled and the unsampled domain. An extension to more complicated algorithms using a union of openings and an intersection of closings is also proposed. Using the Hausdorff metric, it is shown that a morphologically reconstructed image cannot have a better accuracy than twice the radius of the reconstruction structuring element. Binary and gray scale examples are presented.
RESUMEN
Complications of laparoscopic cholecystectomy were evaluated by a survey of surgical department chairpersons at 4,292 US hospitals. The 77,604 cases were reported by 1,750 respondents. Laparotomy was required for treatment of a complication in 1.2% of patients. The mean rate of bile duct injury (exclusive of cystic duct) was 0.6% and was significantly lower at institutions that had performed more than 100 cases. Bile duct injuries were recognized postoperatively in half of the cases and most frequently required anastomotic repair. Intraoperative cholangiography was practiced selectively by 52% of the respondents and routinely by 31%. Bowel and vascular injuries, which occurred in 0.14% and 0.25% of cases, respectively, were the most lethal complications. Postoperative bile leak was recognized in 0.3% of patients, most commonly originating from the cystic duct. Eighteen of 33 postoperative deaths resulted from operative injury. These data demonstrate that laparoscopic cholecystectomy is associated with low rates of morbidity and mortality but a significant rate of bile duct injury.