Characterisation of freeze-dried type II collagen and chondroitin sulfate scaffolds

Collagen type-II is the dominant type of collagen in articular cartilage and chondroitin sulfate is one of the main components of cartilage extracellular matrix. Afibrillar and fibrillar type-II atelocollagen scaffolds with and without chondroitin sulfate were prepared using casting and freeze-drying methods. The scaffolds were characterised to highlight the effects of fibrillogenesis and chondroitin sulfate addition on viscosity, pore structure, porosity and mechanical properties. Microstructure analysis showed that fibrillogenesis increased the circularity of pores significantly in collagen-only scaffolds, whereas with it, no significant change was observed in chondroitin sulfate-containing scaffolds. Addition of chondroitin sulfate to afibrillar scaffolds increased the circularity of the pores and the proportion of pores between 50 and 300 μm suitable for chondrocytes growth. Fourier transform infrared spectroscopy explained the bonding between chondroitin sulfate and afibrillar collagen- confirmed with rheology results- which increased the compressive modulus 10-fold to 0.28 kPa. No bonding was observed in other scaffolds and consequently no significant changes in compressive modulus were detected.     

Optimal selection of cutting parameters in multi-tool milling operations using a genetic algorithm

In the milling of large monolithic structural components for aircraft, 70–80% of the total cut volume is removed using high-speed roughing operations. In order to achieve the economic objective (i.e. optimal part quality in minimal machining time) of this process, it is necessary to determine the optimal cutting conditions while respecting the multiple constraints (functional and technological) imposed by the machine, the tool and the part geometry. This work presents a physical model called GA-MPO (genetic algorithm based milling parameter optimisation system) for the prediction of the optimal cutting parameters (namely, axial depth of cut (a _p), radial immersion (a _e), feed rate (f _t) and spindle speed (n)) in the multi-tool milling of prismatic parts. By submitting a preliminary milling process plan (i.e. CL data file) generated by CAM (computer-aided manufacturing) software, the developed system provides an optimal combination of process parameters (for each machining feature), respecting the machine–tool–part functional/technological constraints. The obtained prediction accuracy and enhanced functional capabilities of the developed system demonstrate its improved performance over other models available in the literature.     

A system for seismocardiography-based identification of quiescent heart phases: implications for cardiac imaging

Seismocardiography (SCG), a representation of mechanical heart motion, may more accurately determine periods of cardiac quiescence within a cardiac cycle than the electrically derived electrocardiogram (EKG) and, thus, may have implications for gating in cardiac computed tomography. We designed and implemented a system to synchronously acquire echocardiography, EKG, and SCG data. The device was used to study the variability between EKG and SCG and characterize the relationship between the mechanical and electrical activity of the heart. For each cardiac cycle, the feature of the SCG indicating Aortic Valve Closure was identified and its time position with respect to the EKG was observed. This position was found to vary for different heart rates and between two human subjects. A color map showing the magnitude of the SCG acceleration and computed velocity was derived, allowing for direct visualization of quiescent phases of the cardiac cycle with respect to heart rate.     

Thermochemical functions for gas-phase, 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), its condensed phases, and its larger reaction products

1,3,5,7-Tetranitro-1,3,5,7-tetraazacyclooctane (HMX) is a major component of many explosives and propellants. Chemical kinetic simulations of the reactions of HMX require knowledge of its enthalpy, entropy, and heat capacity in the gas-phase and condensed phases. While some experimental measurements are available, most available thermochemical information has been obtained by analogy with the smaller species, RDX, and its reaction products. Using the Hartree-Fock method with the 6-31G∗ basis set we have calculated structures, vibrational frequencies, and bond strengths for the isolated HMX molecule and its two major reaction products. This, with some available experimental data, allows us to calculate the relevant thermochemical parameters for these species. With this information and some published experimental measurements of sublimation pressure, phase change enthalpies, and heat capacities, we have also calculated some thermochemical data for three condensed phases of HMX: β-HMX, δ-HMX and liquid HMX. We present the thermochemical parameters in both the JANAF and CHEMKIN format. We also compare the current calculations with previous estimates.     

Electrical conductivity of milk: measurement, modifiers, and meta analysis of mastitis detection performance.

The physics, physiology, and pathology of electrical conductivity of milk are described. Based on a meta analysis, the use of electrical conductivity as a mastitis detection tool is discussed. Most reports were based on subclinical mastitis data. The gold standards of the different reports are discussed. With an overall sensitivity of 66% and an overall specificity of 94%, the predictive value of a positive electrical conductivity test remains low in a low prevalence population. The use of on-line systems for clinical mastitis detection is discussed. On-line systems that combine multiple data and perform multifactorial analyses will be of interest to the dairy industry.     

Modeling the Soluble Solids and Storage Temperature Effects on <Emphasis Type="Italic">Byssochlamys fulva</Emphasis> Growth in Apple Juices

Byssochlamys fulva is an ascospore producer fungus known to be heat resistant and commonly found in fruit juices. This work aims at studying the influence of soluble solid content and storage temperature on the growth of B. fulva in apple juices. Agar-added apple juices, adjusted to different levels of soluble solids (12, 20, 25, 35, 45, 55, 70 °Bx) were artificially inoculated with B. fulva spores and incubated at different temperatures (10, 15, 20, 25, 30 °C). Microorganisms’ growth was assessed every day for a total of 3 months. A Gompertz-based model was used in experimental data fit for each soluble solid and temperature condition applied. Kinetic parameters were estimated by nonlinear regression procedures. The soluble solids and temperature effects were thereafter included in the primary Gompertz-based model. The predictive ability of this expression in terms of B. fulva growth was successfully proven for the range of conditions tested.     

Risk factors for clinical mastitis in herds with a low bulk milk somatic cell count. 2. Risk factors for Escherichia coli and Staphylococcus aureus

The incidence rate of clinical mastitis due to Escherichia coli and Staphylococcus aureus was studied in 125 herds with a low annual bulk milk somatic cell count (less than 150,000 cells/ml). Risk factors that were offered to a multivariate Poisson regression model included general management, housing, cleaning procedures, cow and cubicle cleanliness, feeds and feeding, dry cow management, milking procedures, machine milking, disease prevention, and milk production. Some differences in epidemiology between E. coli and S. aureus were observed. In the S. aureus model, more milking procedure and milking machine variables were present. The milk production, drinking water source, amount of bedding, and ventilation were other important factors in the S. aureus model. Teat disinfection was an important risk factor in the E. coli model but was much less important in the S. aureus model. Cleaning procedures were more important in the E. coli model. The main breed on the farm and percentage of cows leaking milk were other important factors in the E. coli model.     

Effect of Solvent Content on the Separation and the Energy Consumption of Extractive Distillation Columns

This article sets out to evaluate the effect of solvent content in the extractive section on the separation efficiency and energy consumption of extractive distillation columns. Contrary to the classical approach, the proposed approach enables a simultaneous evaluation of the effect of the major decision variables (reflux ratio, solvent flow rate, and the number of stages of the extractive section [NSE]). The procedure allows calculating the minimum solvent flow rate for the separation and the minimum specific energy consumption. The results show that the minimum specific energy consumption is obtained for the minimum reflux ratio and not for the minimum solvent flow rate. Moreover, the results show that it is not always the case that a larger NSE results in lower energy consumption. Due to its industrial importance, the dehydration of aqueous mixtures of ethanol using ethylene glycol as solvent has been chosen as a case study.     

Synthesis and Characterization of Aluminum–Zirconium Intermetallic Composites

The search for composite materials comes from a necessity of improving properties of conventional materials. The reaction synthesis process frequently gives products with some level of porosity that may be improved through the use of hot pressing routes. The combination of aluminum and zirconia in controlled conditions has led to a metal matrix composite with a dispersion of intermetallics, especially Al₃Zr. Temperature, pressure, and chemical composition were the main parameters varied during the production of the samples. The experimental procedures consisted initially of the mixing and homogenization of the powders in three proportions (5, 10, and 20 in zirconia wt. %). The powders were pressed for the production of green bodies, cylinders of 9 × 9 mm, with the application of three pressures (150, 250, and 300 MPa). Synthesis was carried out in a tubular furnace (1073, 1173, and 1273 K) using a helium atmosphere. Reactive hot pressing was carried out in a MTS machine. The densification process in the simultaneous hot pressing was observed with the use of mercury picnometry to measure the densities and confirmed with the help of an image analyzer. The temperatures were monitored by a thermocouple connected to an A/D interface. Determination of Vickers microhardness was carried out in the aluminum matrix and in the intermetallic particles; hardness was determined in all samples. The identification of the phases was obtained utilizing XRD, optical, and SEM microscopy.