Early, full weightbearing with flexible fixation delays fracture healing

Secondary fracture healing is known to be accelerated by the process of periosteal callus formation that can be induced by flexible fracture fixation in connection with loading of the injured extremity. The purpose of this study was to compare the healing of experimental fractures of long bones in sheep under early weightbearing with that of fractures under delayed, steadily increasing weightbearing. Differences in the quality of fracture healing were described by biomechanical (rigidity of fracture, indentation stiffness of callus) and histologic methods. Prevention from early, full weightbearing resulted in a higher flexural rigidity of the fracture, an increased mechanical stiffness of the callus tissue, and an enhanced bone formation at the healing front. Although early loading of a fresh fracture initiated an enormous amount of periosteal callus, the healing of the osteotomy was significantly delayed, and the quality of the newly formed tissue was reduced as compared with fractures with a reduced loading situation. A reduction of load transfer by delaying full weightbearing is advantageous for the healing of fractures stabilized with flexible fixation systems.     

Effects of acute hyperinsulinemia on VLDL triglyceride and VLDL apoB production in normal weight and obese individuals

The effects of short-term hyperinsulinemia on the production of both VLDL triglyceride and VLDL apoB were determined semiquantitatively before and during a 6-h euglycemic hyperinsulinemic clamp (40 mU.m-2 x min-1) in 17 women (8 chronically hyperinsulinemic obese, BMI = 35.7 kg/m2; 9 normal weight, BMI = 22.5 kg/m2). During acute hyperinsulinemia, plasma FFA decreased by approximately 95% within 1 h in both groups. VLDL triglyceride production decreased 66% in the control subjects (P = 0.0003) and 67% in obese subjects (P = 0.0003). ApoB production decreased 53% in control subjects (P = 0.03) but only 8% in obese (NS). Plasma triglycerides decreased by 40% from baseline in control subjects (P < 0.0001) but only by 10% in obese subjects (P = NS). Despite the similar decrease in triglyceride and apoB production in control subjects, VLDL particle size (triglyceride-to-apoB ratio) decreased with hyperinsulinemia (P = 0.003). In obese subjects, despite a decrease in triglyceride production similar to that in control subjects but no change in apoB production, VLDL size did not change appreciably. Acute hyperinsulinemia in humans: 1) suppresses plasma FFA equally in control and obese subjects at this high dose of insulin; 2) inhibits VLDL triglyceride production equally in control and obese subjects, perhaps secondary to the decrease in FFA; 3) inhibits VLDL apoB production in control but less so in obese subjects, suggesting that obese subjects may be resistant to this effect of insulin; 4) decreases plasma triglyceride and VLDL particle size in control subjects, reflecting either stimulation of LPL activity or a greater relative decrease in triglyceride to apoB production; and 5) does not decrease plasma triglyceride or VLDL size in obese subjects to the same extent as it does in control subjects. Thus, the insulin resistance of obesity affects some but not all aspects of VLDL metabolism.     

Influence of annealing on the permeation properties of a thermoplastic elastomer

The use of plastic films with specific diffusion or permeation properties for industrial applications has grown at a considerable rate. Some useful applications are found in medical devices, bioreactors, and combustible fuel storage where polymer films function as separation membranes that allow permeation of different gases at different rates. In this work, the permeation and diffusion properties of a polyester‐based thermoplastic polyurethane (TPU) were investigated. TPU injected and extruded specimens were subjected to thermal treatment (annealing) at 100°C for 20 h. Injected samples were exposed to certain hygrothermal conditions and films were prepared to evaluate the influence of annealing on the permeation of gases. In order to achieve a complete analysis, tests such as differential scanning calorimetry, tensile tests, and Fourier transform infrared spectroscopy were conducted to examine the morphological changes. These were then correlated to the TPU permeation behavior after annealing. Water uptake by the polymer—measured as weight gain—likely indicates an increase in the free volume in the amorphous domains. Similarly, in permeation and water immersion tests, the diffusion rate of gases and H₂O through the TPU was higher for the annealed samples when compared to those without treatment, indicating that diffusion within the polymer is dependent on the postprocessing thermal treatment. POLYM. ENG. SCI., 59:1810–1817, 2019. © 2019 Society of Plastics Engineers     

Bounding the Inefficiency of the Reliability-Based Continuous Network Design Problem Under Cost Recovery

Networks and Spatial Economics - This study defines the price of anarchy for general reliability-based transport network design problems, which is an indicator of inefficiency that reveals how much...     

A controlled atmosphere specimen holder for transmission electron microscopy

A controlled atmosphere specimen holder (CASH) has been developed for transmission electron microscopy (TEM) experiments. It is designed for studying the specimen's microstructure before and after treatments in various gases (H₂, O₂, N₂, Ar, etc.) at temperatures up to 600°C. The experiments are carried out without exposing the specimen to the ambient atmosphere. No modification of the electron microscope itself is needed. The same area of the specimen can be easily located after each gas treatment, thus the changes in the microstructure can be studied directly. Preliminary results on the cyclic oxidation and reduction of a model cobalt catalyst are presented.     

Ordered silicon vacancies in the framework structure of the zeolite catalyst SSZ-74

Physico-chemical characterization of the high-silica zeolite catalyst SSZ-74 (ref. 1) suggested that it, like the related materials TNU-9 (ref. 2) and IM-5 (ref. 3), has a multidimensional 10-ring channel system. Such pore systems are ideal for many petrochemical applications, and indeed SSZ-74 has been shown to be a good catalyst for a wide variety of reactions. The elucidation of its framework structure, however, proved to be difficult. Comparable problems were encountered with TNU-9 and IM-5, which were synthesized with related structure-directing agents. Their framework structures, which are the two most complex ones known, both have 24 Si atoms in the asymmetric unit, and were finally solved by combining high-resolution powder diffraction data with information derived from high-resolution electron microscopy images. Therefore, a similar approach, using the powder charge-flipping algorithm to combine the two types of data and molecular modelling to help to locate the structure-directing agent, was applied to SSZ-74. This procedure eventually revealed a most unusual 23-Si-atom framework structure (|(C(16)H(34)N(2))(4)&Si(92)(4)O(184)(OH)(8)]) with ordered Si vacancies.