Rheological and thixotropic behavior of banana (Musa cavendishii) puree

Some rheological properties of banana puree were investigated. Experimental data was fitted to Hahn, Weltmanand Figoni-Shoemaker equations in order to quantify the thixotropic behavior. Thixotropy measurements were carried out in a range between 5 and 75ºC and applying she arrates of 10 and 20 s-1, finding that, in all cases, the Figoni-Shoemaker relationship was the best one to model the time dependency response. The flow behavior was well fitted by the Herschel-Bulkley model in a range between 5 and 75ºC, and between 12 and 22 ºBrix, obtaining that consistency coefficient decreased with temperature and increased with soluble solids content, flow behavior index decreased with soluble solids content, and apparent viscosity decreased with temperature and increased with soluble solids content. Adjusting the variation of apparent viscosity with temperature by means of an Arrhenius-type equation, the activation energy was obtained for different soluble solids content

Application of a new methodology based on Eurocodes and finite element simulation to the assessment of a romanesque church

This work proposes a methodology, based on finite element simulation, for analyzing masonry historical structures, according to Eurocodes, that has been applied for the assessment of the Saint Sebastian church, located in Piedratajada (Zaragoza, Spain). Settlement pathologies were detected and the aim of the work is to verify the current safety level and to propose reinforcement solutions if necessary. Results confirm the effect of soil settlement and allow establish the maximum admissible value. If that value is reached, a couple of reinforcement solutions, installing sheets of steel or carbon fiber composite, are proposed and analyzed

Rheology of redcurrant juices

The rheological behaviour of two different redcurrant juices was studied. Juices containing pectins exhibited non-Newtonian behavior. Juices from which pectins were removed exhibited Newtonian behavior. The power lawmodel described the relationship between shear stress and shear rate for the first type of juice, and the Newtonian model described the second type. The effect of temperature on the apparent viscosity at 100 s-1 was described by Arrhenius equation

To shift, or not to shift: Adequate selection of an internal standard in mass-shift approaches using tandem ICP-mass spectrometry (ICP-MS/MS)

The use of an internal standard to correct for potential matrix effects and instrument instability is common practice in ICP-MS. However, with the introduction of a new generation of ICP-MS instrumentation with a tandem mass spectrometry configuration (ICP-MS/MS), the use of chemical resolution in a mass-shift approach has become much more popular, suggesting that the appropriate selection of an internal standard needs revision. In this particular case, it needs to be decided whether the internal standard should also be subjected to a mass-shift or can simply be monitored on-mass ("to shift, or not to shift"). In this work, 17 elements covering a wide range of masses (24-205 amu) and ionization energies (3.89-9.39 eV) were measured via on-mass and/or mass-shift strategies, and the corresponding atomic ions and reaction product ions were monitored during various systematic experiments. For mass-shifting, an NH3/He gas mixture was used to obtain NH3-based reaction product ions (cluster formation). Product ion scanning (PIS) was used for assessing the differences in reactivity between the different analytes and for the identification of the best suited reaction product ions. It was found that the use of chemical resolution can significantly affect the short-term signal stability and that ion signals measured on-mass are not affected in the same way as those measured mass-shifted. Variations affecting the signal intensities of both atomic and reaction product ions can be attributed to the ion-molecule chemistry occurring within the collision/reaction cell and were found to be related with some degree of initial instability in the cell and differences in reactivity. The use of a sufficiently long stabilization time, however, avoids or at least mitigates such differences in the behavior between signals monitored on-mass and after mass-shifting, respectively. Furthermore, the introduction of cell disturbances, such as those generated after quickly switching between different sets of operating conditions in a multi-tune method, revealed significant differences in signal behavior between atomic and reaction product ions, potentially hampering the use of an internal standard monitored on-mass when the analysis is based on an analyte monitored after mass-shifting. However, the use of a reasonable waiting time again greatly mitigates such differences, with the duration of this stabilization time depending on the magnitude of the cell disturbances (e.g., switch between vented and pressurized mode or only between pressurized modes using different gas flow rates). In addition, also the effect of varying different instrument settings (plasma power, torch position, and gas and liquid flow rates) was evaluated, but no remarkable differences were found between signals monitored on-mass and those mass-shifted. Interestingly, a statistical evaluation of the influence of the different settings on the signal intensities of all ions monitored did not reveal the a priori important role of some properties traditionally suggested for adequate selection of analyte/internal standard pairs, such as mass number or ionization energy, as also suggested in other recent studies. © The Royal Society of Chemistry

The use of Barthel index for the assessment of the functional recovery after osteoporotic hip fracture: One year follow-up

The Barthel index evolution was analyzed in a sample of older people with osteoporotic hip fracture in order to verify the influence of comorbidities and cognitive impairment on the physical recovery of those patients, during the first year following the fracture. A prospective observational study was carried out between October 1, 2012 and March 31, 2013. A sample of 247 individuals was initially selected. After a primary revision, 39 participants were excluded (clearly not meeting inclusion criteria, lack of data, or not agree to participate in the study), and finally a total of 208 participants were included in the analysis, 166 women, with an average age of 84.59 years, and 42 men, with an average age of 82.05. 54.80% of all cases were older than 85 years. The mean Barthel index value prior to fracture was 76.63, decreasing to 64.91 at one-year follow-up. Only 22.12% of patients achieved a full recovery for activities of daily living. A statistical analysis was performed by comparing Barthel index recovery depending on the values of Charlson and Pfeiffer indexes, respectively. The mean differences in Barthel index drop between the one-year follow-up and the hospital admission values were found statistical significant (p<0.01). These findings indicate that Charlson and Pfeiffer indexes clearly influence the Barthel index recovery. Low values of Charlson and Pfeiffer indexes resulted in better Barthel index recovery. In conclusion, the Barthel index is a good tool to evaluate the physical recovery after osteoporotic hip fracture

A comparative study of hyperelastic constitutive models for colonic tissue fitted to multiaxial experimental testing

For colonic stents design, the interaction with colonic tissue is essential in order to characterize the appropriate radial stiffness which provides a minimum lumen for intestinal transit to be maintained. It is therefore important to develop suitable constitutive models allowing the mechanical behavior of the colon tissue to be characterized. The present work investigates the biomechanical behavior of colonic tissue by means of biaxial tests carried out on different parts of the colonic tract taken from several porcine specimens. Samples from the colonic tract were quasi-statically tensioned using a load-controlled protocol with different tension ratios between the circumferential and the axial directions. Fitting techniques were then used to adjust specific hyperelastic models accounting for the multilayered conformation of the colonic wall and the fiber-reinforced configuration of the corresponding tissues. It was found that the porcine colon changed from a more isotropic to a more anisotropic tissue and became progressively more flexible and compliant in circumferential direction depending on the position along the duct as it approaches the rectum. The best predictive capability of mechanical behavior corresponds to the Four Fiber Family model showing mean values of coefficient of determination R2 ¼ 0:97, and a normalized root mean square error of eNRMS ¼ 0:0814 for proximal spiral samples, and R2 ¼ 0:89 ; eNRMS ¼ 0:1600 and R2 ¼ 0:94 ; eNRMS ¼ 0:1227 for distal spiral and descending colon samples, respectively. The other analyzed models provide good results for proximal spiral colon specimens, which have a lower degree of anisotropy. The analyzed models with the fitted elastic parameters can be used for more realistic and reliable FE simulations, providing the appropriate framework for the design of optimal devices for the treatment of colonic diseases

Study of the polycarbonate-urethane/metal contact in different positions during gait cycle

Nowadays, a growing number of young andmore active patients receive hip replacement.More strenuous activities in such patients involve higher friction and wear rates, with friction on the bearing surface being crucial to ensure arthroplasty survival in the long term. Over the last years, the polycarbonate-urethane has offered a feasible alternative to conventional bearings. A finite element model of a healthy hip joint was developed and adjusted to three gait phases (heel strike, mid-stance, and toe-off), serving as a benchmark for the assessment of the results of joint replacement model. Three equivalent models were made with the polycarbonate-urethane Tribofit system implanted, one for each of the three gait phases, after reproducing a virtual surgery over the respective healthy models. Standard body-weight loads were considered: 230% body-weight toe-off, 275% body-weight mid-stance, and 350% body-weight heel strike. Contact pressures were obtained for the different models. When comparing the results corresponding to the healthy model to polycarbonate-urethane joint, contact areas are similar and so contact pressures are within a narrower value range. In conclusion, polycarbonate-urethane characteristics are similar to those of the joint cartilage. So, it is a favorable alternative to traditional bearing surfaces in total hip arthroplasty, especially in young patients