ABSTRACT
INTRODUCTION AND OBJECTIVES: Bariatric surgery is the most effective treatment for weight loss, with comorbidity control. With low complication rates, the reasons for reoperation are major complications or weight loss failure/weight regain. Nonsurgical problems can also present, such as anemia, dehydration, chronic pain, and malnutrition, among others. Our aim was to analyze the main causes of revisional surgery, reoperation, and hospital readmission, at a specialized bariatric center. METHODS: A retrospective study was conducted on patients that underwent bariatric surgery within the time frame of 2012 and 2019. The baseline analysis included demographic, anthropometric, and perioperative data, as well as a sub-analysis of the main readmission causes and complications. RESULTS: A total of 776 primary surgeries were performed (649 RYGBP, 127 SG, and 10 revisional surgeries), and 99 patients were identified for the study: 10 revisional surgeries, 44 reoperations, and 45 readmissions. The incidence of revisional surgery was 1.2%, reoperation was 5.6%, and readmission 5.8%. Fifty percent of the revisional surgeries were performed due to insufficient weight loss or weight regain; the most frequent causes of reoperation were cholecystitis (38.6%) and internal hernias (9.1%); and the most common causes of readmission were nonspecific abdominal pain (35.5%) and dehydration (24.4%). CONCLUSION: The most frequent causes of postoperative readmission were nonsurgical events, followed by non-bariatric reoperations, and finally revisional surgeries. There was a low incidence of early reoperations. Knowledge of the abovementioned data is important for identifying higher-risk patients, to prevent major complications.
ABSTRACT
Granular self-assembly of confined non-Brownian spheres under gravity is studied by molecular dynamics simulations. Starting from a disordered phase, dry or cohesive spheres organize, by vibrational annealing, into body-centered-tetragonal or face-centered-cubic structures, respectively. During the self-assembling process, isothermal and isodense points are observed. The existence of such points indicates that both granular temperature and packing fraction undergo an inversion process that may be in the core of crystal nucleation. Around the isothermal point, a sudden growth of granular clusters having the maximum coordination number takes place, indicating the outcome of a first-order phase transition. We propose a heuristic equation that successfully describes the dynamic evolution of the local packing fraction in terms of the local granular temperature, along the entire crystallization process.
ABSTRACT
Dedicated bond force constant and bulk modulus of C n fullerenes (n = 20, 28, 36, 50, 60) are computed using density functional theory (DFT). DFT predicts bond force constants of 611, 648, 675, 686, and 691 N/m, for C20, C28, C36, C50, and C60, respectively, indicating that the bond force constant increases for larger fullerenes. The bulk modulus predicted by DFT increases with decreased fullerene diameter, from 0.874 TPa for C60 to 1.830 TPa for C20. The bond force constants predicted by DFT are then used as an input for finite element analysis (FEA) of the fullerenes, considered as spatial frames in structural models where the bond stiffness is represented by the DFT-computed bond force constant. In agreement with DFT, FEA predicts that smaller fullerenes are stiffer, and underestimates the bulk modulus with respect to DFT. The difference between the FEA and DFT predictions of the bulk modulus decreases as the size of the fullerene increases, from 20.9% difference for C20 to only 4% difference for C60. Thus, it is concluded that knowing the appropriate bond force constant, FEA can be used as a plausible approximation to model the elastic behavior of small fullerenes.
Subject(s)
Finite Element Analysis , Fullerenes/chemistry , Models, TheoreticalABSTRACT
Thermal properties of solids are obtained by fitting the exact complex photothermal model to the normalized photoacoustic (PA) signal in the front configuration. Simple closed-form expressions for the amplitude and phase are presented in all frequency ranges. In photoacoustic it has been common practice to assume that all the absorptions of radiation take place in the sample. However, in order to obtain the accurate thermal properties it is necessary to consider the PA signal contributions produced at the cell walls. Such contributions were considered in our study. To demonstrate the usefulness of the proposed methodology, commercial stainless steel layers AISI 302 were analyzed. It is shown that using our approach the obtained thermal diffusivity and effusivity were in good agreement with those reported in the literature. Also, a detailed procedure for the calculation of the standard error in the thermal properties is discussed.
