Interface formed between visceral peritoneum and experimental polypropylene or polytetrafluoroethylene abdominal wall implants

The objective of this work was to study the healing process at the interface between biomaterial and visceral peritoneum. Implants of polytetrafluoroethylene (ePTFE) and polypropylene prostheses were introduced into the abdominal wall of New Zealand rabbits. The behaviour of the biomaterials was analysed using light and scanning electron microscopy and immunohistochemistry in which a specific anti-rabbit macrophage monoclonal antibody (RAM 11) was employed. According to macroscopic observation, there was significantly fewer adhesions prosthesis-viscera to ePTFE than to polypropylene implants. After ePTFE implantation, restoration of the peritoneum took place in an orderly fashion. When polypropylene was used, the peritoneum formed was a disorderly tissue in which small areas of haemorrhage and necrosis could be seen to coincide with the appearance of adhesions. The number of labelled macrophages peaked 14 days after ePTFE or polypropylene implantation, after which it decreased gradually. It is concluded that, given the low rate of adhesion provoked by PTFE, this material is ideal for implants contiguous to the peritoneal cavity viscera. The macrophage response does not determine the use of one material or the other. The structure of the newly formed peritoneum and development of adhesions depends on the porosity of the biomaterial.     

Infants of diabetic mothers (IDM). II -- Fibronectin and perinatal morbidity

OBJECTIVE: The objective of this study was to determine fibronectin levels in umbilical cord blood of infants of diabetic mothers (IDM) and evaluate a possible correlation with perinatal pathology. PATIENTS AND METHODS: A prospective study of 58 IDM (33 males and 25 females) and 58 control newborns (NB) (33 males and 25 females) was carried out. RESULTS: There were no differences in fibronectin levels between the two groups nor between the sexes. Perinatal morbidity was higher in the IDM group, but there was no correlation between fibronectin levels and the presence of perinatal pathology. CONCLUSIONS: Fibronectin levels are not useful in the perinatal evaluation of infants of diabetic mothers.     

A neuron membrane mesh representation for visualization of electrophysiological simulations

We present a process to automatically generate three-dimensional mesh representations of the complex, arborized cell membrane surface of cortical neurons (the principal information processing cells of the brain) from nonuniform morphological measurements. Starting from manually sampled morphological points (3D points and diameters) from neurons in a brain slice preparation, we construct a polygonal mesh representation that realistically represents the continuous membrane surface, closely matching the original experimental data. A mapping between the original morphological points and the newly generated mesh enables simulations of electrophysiolgical activity to be visualized on this new membrane representation. We compare the new mesh representation with the state of the art and present a series of use cases and applications of this technique to visualize simulations of single neurons and networks of multiple neurons.     

Enhanced mortar approach to characterize the effect of reclaimed asphalt pavement on virgin binder true grade

The asphalt community seeks a solvent-free method to determine the properties of RAP binder and those of its blends with virgin binders. A promising approach is to test mortars composed of fine fractions of RAP and a virgin binder, and to calculate grade change rate (GCR) to predict blended binder true grade at any binder replacement rate (BRR). However, the existing mortar approach underestimates the effect of RAP on binder grade, particularly at high temperatures. This study identified the use of a shift factor in the existing method as the source of underestimations. An alternative data analysis method was developed, which eliminates the shift factor by using the relationship between binder and mortar properties. Dynamic shear rheometer tests were conducted on a total of 12 mortar combinations, including 4 virgin binders and 3 RAP sources at a BRR of 15%, and then, RAP GCR values were determined by following both the existing and the alternative methods. Satisfactory comparisons were only observed between grades predicted with the alternative method and measured values of manual RAP binder blends: the average difference was lower than 1 °C for BRR of 15 and 30%, and < 4 °C for BRR of 100%. This not only validated the alternative method but also substantiated that RAP GCR is constant, i.e., the grade of RAP blends linearly increased with BRR. Further evaluation of the enhanced mortar approach is recommended at intermediate and low temperatures as well as with blends including recycled asphalt shingles.     

Modeling and performance analysis of an absorption chiller with a microchannel membrane‐based absorber using LiBr‐H2O,LiCl‐H2O,and LiNO3‐NH3

In order to develop compact absorption refrigeration cycles driven by low heat sources, the simulated performance of a microchannel absorber of 5‐cm length and 9.5 cm³ in volume provided with a porous membrane is presented for 3 different solution‐refrigerant pairs: LiBr‐H₂O, LiCl‐H₂O, and LiNO₃‐NH₃. The high absorption rates calculated for the 3 solutions lead to large cooling effect to absorber volume ratios: 625 kW/m³ for the LiNO₃‐NH₃, 552 kW/m³ for the LiBr‐H₂O, and 318 kW/m³ for the LiCl‐H₂O solutions given the studied geometry. The performance of a complete absorption system is also analyzed varying the solution concentration, condensation temperature, and desorption temperature. The LiNO₃‐NH₃ and the LiBr‐H₂O solutions provide the largest cooling effects. The LiNO₃‐NH₃ can work at a lower temperature of the heating source, in comparison with the one needed in a LiBr‐H₂O system. The lowest cooling effect and coefficient of performance are found for the LiCl‐H₂O solution, but this mixture allows the use of lower temperature heating sources (below 70°C). These results can be used for the selection of the most suitable solution for a given cooling duty, depending on the available heat source and condensation temperature.     

Generalization of recommender systems: Collaborative filtering extended to groups of users and restricted to groups of items

In this paper we present a collaborative filtering method which opens up the possibilities of traditional collaborative filtering in two aspects: (1) it enables joint recommendations to groups of users and (2) it enables the recommendations to be restricted to items similar to a set of reference items. By way of example, a group of four friends could request joint recommendations of films similar to “Avatar” or “Titanic”. In the paper, using experiments, we show that the traditional approach of collaborative filtering does not satisfactorily resolve the new possibilities contemplated; we also provide a detailed formulation of the method proposed and an extensive set of experiments and comparative results which show the superiority of designed collaborative filtering compared to traditional collaborative filtering in: (a) number of recommendations obtained, (b) quality of the predictions, (c) quality of the recommendations. The experiments have been carried out on the databases Movielens and Netflix.