RESUMEN
Dragonflies and damselflies, belonging to the order Odonata, are known to be excellent fliers with versatile flight capabilities. The ability to fly over a wide range of speeds, high manoeuvrability and great agility are a few characteristics of their flight. The architecture of the wings and their structural elements have been found to play a major role in this regard. However, the precise influence of individual wing components on the flight performance of these insects remains unknown. The design of the wing basis (so called basal complex) and the venation of this part are responsible for particular deformability and specific shape of the wing blade. However, the wing bases are rather different in representatives of different odonate groups. This presumably reflects the dimensions of the wings on one hand, and different flight characteristics on the other hand. In this article, we develop the first three-dimensional (3D) finite element (FE) models of the proximal part of the wings of typical representatives of five dragonflies and damselflies families. Using a combination of the basic material properties of insect cuticle, a linear elastic material model and a nonlinear geometric analysis, we simulate the mechanical behaviour of the wing bases. The results reveal that although both the basal venation and the basal complex influence the structural stiffness of the wings, it is only the latter which significantly affects their deformation patterns. The use of numerical simulations enabled us to address the role of various wing components such as the arculus, discoidal cell and triangle on the camber formation in flight. Our study further provides a detailed representation of the stress concentration in the models. The numerical analysis presented in this study is not only of importance for understanding structure-function relationship of insect wings, but also might help to improve the design of the wings for biomimetic micro-air vehicles (MAVs).
Asunto(s)
Odonata/anatomía & histología , Alas de Animales/anatomía & histología , Animales , Fenómenos Biomecánicos , Simulación por Computador , Vuelo Animal , Modelos Lineales , Dinámicas no Lineales , Odonata/ultraestructura , Estrés Fisiológico , Alas de Animales/fisiología , Alas de Animales/ultraestructuraRESUMEN
Congenital anomalies of the inferior vena cava (IVC) and its tributaries are increasingly recognized in asymptomatic patients due to the more frequent use of cross-sectional imaging and computed tomography (CT) in particular. IVC development is a complex process involving formation of anastomoses between three pairs of embryonic veins in the 4th to 8th week of gestation. Various permutations occur in the basic venous plan of the abdomen and pelvis resulting in variants such as isolated left IVC, double IVC, and retroaortic left renal vein. The majority of these anomalies are asymptomatic but occasionally present clinically with thromboembolic complications. However, awareness of their existence is important to avoid important diagnostic pitfalls and in preoperative surgical and interventional radiological planning.
Asunto(s)
Vena Cava Inferior/anomalías , Humanos , Tomografía Computarizada por Rayos X , Vena Cava Inferior/embriologíaRESUMEN
Solubility enhancement of the water insoluble bromazepam was studied during the formation of its inclusion complexes with beta-cyclodextrin (beta-CD) and beta-hydroxypropyl-cyclodextrin (beta-HP-CD). The phase solubility technique established by Higuchi and Connors and UV-spectrophotometric methods (zero- and second-order derivative approaches) were used to measure the changes introduced in this chemical system. The amount of time, which was necessary to reach equilibrium between inclusion complexes and their free components, was estimated and found equal to 24 h. The study was carried out at (i) pH 7.0 and 25 degrees C and (ii) pH 7.4 and 37 degrees C. The solubility of bromazepam increased linearly as a function of concentration for both beta-and beta-hydroxypropyl-cyclodextrins. Thus, the phase solubility diagrams were classified as of A(L) type in all cases. Under the above-mentioned conditions, the formation constants of the inclusion complexes were calculated and their stoichiometry was evaluated, found in the range of 69-85 M(-1) and 1:1, respectively.
Asunto(s)
Ansiolíticos/análisis , Bromazepam/análisis , Ciclodextrinas/química , beta-Ciclodextrinas , 2-Hidroxipropil-beta-Ciclodextrina , Algoritmos , Calibración , Concentración de Iones de Hidrógeno , Indicadores y Reactivos , Reproducibilidad de los Resultados , Solubilidad , Soluciones , Espectrofotometría Ultravioleta , TemperaturaAsunto(s)
Aneurisma de la Aorta Abdominal/cirugía , Infecciones Bacterianas/etiología , Prótesis Vascular/efectos adversos , Enfermedades del Colon/etiología , Fístula/etiología , Anciano , Infecciones Bacterianas/diagnóstico , Enfermedades del Colon/cirugía , Colonoscopía , Fístula/cirugía , Humanos , MasculinoRESUMEN
Patients with metastatic rectal cancer precluding curative low anterior resection (LAR) or abdominoperineal resection (APR) can require palliation for impending obstruction. LAR or APR is frequently not optimal because of the associated operative morbidity. Lesser procedures such as diverting colostomy require patients to live with a permanent stoma. Endoscopic transanal resection (ETAR) has been used for excision of rectal lesions. To determine whether ETAR provides palliation equivalent to LAR or APR, we reviewed the outcomes of 49 patients with rectal adenocarcinoma and unresectable liver metastases who required palliative intervention between January 1989 and July 1996. Of these 49 patients, 24 underwent ETAR; the intraluminal tumor was resected using the urologic resectoscope to achieve a hemostatic, patent lumen. The outcomes of these patients were compared to those of the other 25 patients who had palliative LAR, APR, or a Hartmann procedure during the same period. The median distance of the tumors from the anal verge was similar (5 cm; range 1 to 15 cm). ETAR patients had a higher percentage of poorly differentiated tumors (35% vs. 6%, P = 0.034) and higher preoperative alkaline phosphatase values (478 +/- 75 mg/dl vs. 231 +/- 24 mg/dl; P < 0.015), suggesting more aggressive disease and greater hepatic tumor burden, respectively. Despite these differences, overall survival and time spent outside the hospital were similar in the two groups. The median number of debulking procedures required in the 24 ETAR patients was two (range 1 to 17). Resections in the 25 LAR/APR patients included LAR in 20, APR in two, and Hartmann procedures in three. There was a trend toward more stomas in the LAR/APR group (28% vs. 17%). More important, morbidity was significantly higher in the LAR/APR patients (24% vs. 4%; P = 0.049). In conclusion, ETAR is a safe alternative for the palliation of incurable rectal tumors. Compared to transabdominal resection, ETAR provides equivalent palliation as measured by survival and proportion of the patient's life spent outside the hospital, with a lower stoma rate and significantly less morbidity. Therefore, in select patients with metastatic rectal cancer, ETAR is an important palliative option.