Evaluation of processed cheese viscoelastic properties during sterilization observed in situ.

Sterilized processed cheese is a specific dairy product with a prolonged shelf life intended for regular retail offer but also as food provisions for armies during peacetime, as well as during crisis and emergency situations, and for storage in state material reserves. Storage requirements are usually defined as ≤25°C for at least 24 mo. One of the ways to achieve such a shelf life is sterilization. Therefore, the aim of the work was to describe, for the first time in the available scientific literature, in situ changes in the viscoelastic properties of spreadable melt (34% wt/wt DM content, 45% wt/wt fat in DM content, and 14% wt/wt protein content) during an increase in temperature (target temperature 122°C), holding at sterilization temperature (20 min) and subsequent cooling (to ~30°C). While increasing to the target sterilization temperature, a significant decrease occurred in the storage and loss moduli values. Both moduli started to increase again during the target sterilization temperature period and during the whole cooling phase. The values of the storage and loss moduli were significantly higher at the end of the cooling of the sterilized product, and conversely, the phase angle value was lower compared with the melt before sterilization. As a result of sterilization, an increase occurred in the levels of markers of the Maillard reaction complex and lipid oxidation processes. The value of hardness, corrected stress, and elongational viscosity also increased compared with nonsterilized products. As a result of sterilization, the flavor worsened and sterilized processed cheeses showed darker (brownish) color. However, even after sterilization, the products were evaluated as acceptable for consumers and maintained their spreadability.

Reprocessed magnetorheological elastomers with reduced carbon footprint and their piezoresistive properties.

Despite the vast amount of studies based on magnetorheological elastomers (MREs), a very limited number of investigations have been initiated on their reprocessing. This paper presents a new type of recyclable MRE which is composed of thermoplastic polyurethane (TPU) and carbonyl iron particles (CI). The chosen TPU can be processed using injection moulding (IM), followed by several reprocessing cycles while preserving its properties. Numerous types of injection moulded and reprocessed MREs have been prepared for various particle concentrations. The effect of thermo-mechanical degradation on the recycled MREs has been investigated while simulating the reprocessing procedure. An apparent decrease in molecular weight was observed for all the examined matrices during the reprocessing cycles. These changes are attributed to the intermolecular bonding between the hydroxyl groups on the surface of the CI particles and the matrix which is studied in depth. The effect of reprocessing and the presence of magnetic particles is evaluated via tensile test, magnetorheology and piezoresistivity. These characterization techniques prove that the properties of our MREs are preserved at an acceptable level despite using 100% of recyclates while in real applications only up to 30% of recycled material is generally used.

Mechanical properties of bulk Sylgard 184 and its extension with silicone oil.

Due to its simple curing and very good mechanical properties, Sylgard 184 belongs to the most widely and frequently used silicones in many industrial applications such as microfluidics and microengineering. On top of that its mechanical properties are further controllable through the curing temperature, which may vary from ambient temperature up to 200 °C; the lower the curing temperature the lower the mechanical properties (Johnston et al. in J Micromech Microeng 24:7, 2014. 10.1088/0960-1317/24/3/035017). However, certain specialised application may require even a softer binder than the low curing temperature allows for. In this study we show that this softening can be achieved with the addition of silicone oil into the Sylgard 184 system. To this end a series of Sylgard 184 samples with varying silicone oil concentrations were prepared and tested (tensile test, rotational rheometer) in order to determine how curing temperature and silicone oil content affect mechanical properties. Curing reaction of the polymer system was found to observe 2nd order kinetics in all cases, regardless the oil concentration used. The results suggest that within the tested concentration range the silicone oil addition can be used to soften commercial silicone Sylgard 184.

Electrorheological behavior of iron(ii) oxalate micro-rods.

Electrorheological (ER) fluids represent smart materials with extensive application potential due to their rheological properties which can be readily changed under an external electric field. In this study, the iron(ii) oxalate particles with rod-like morphology were successfully synthesized by the co-precipitation method using sulphate heptahydrate and oxalic acid dihydrate. The characterization of particles was performed via X-ray diffractometry and scanning electron microscopy. Subsequently, the ER fluids were prepared by dispersing the synthesized particles in silicone oil. The optical microscopy demonstrated the formation of chain-like particle structures upon the application of an electric field. Rheological properties were determined by means of rotational rheometry including creep-recovery experiments. The viscoelastic behavior of systems under investigation in the presence of the electric field was confirmed by the presence of recoverable strain of the system.

The electrorheological behavior of suspensions based on molten-salt synthesized lithium titanate nanoparticles and their core-shell titanate/urea analogues.

This paper concerns the preparation of novel electrorheological (ER) materials using microwave-assisted synthesis as well as utilizing a suitable shell-providing system with enhanced ER performance. Lithium titanate nanoparticles were successfully synthesized, and their composition was confirmed via X-ray diffraction. Rheological properties were investigated in the absence as well as in the presence of an external electric field. Dielectric properties clarified the response of the particles to the application of an electric field. The urea-coated lithium titanate nanoparticle-based suspension exhibits higher ER performance in comparison to suspensions based on bare particles.

[Correlation of the Heidelberg retinal tomograph, evaluation of the retinal nerve fiber layer and perimetry in the diagnosis of glaucoma]. / Korelace Heidelberského retinálního tomografu, hodnocení vrstvy nervových vláken a perimetrie v diagnostice glaukomu.

PURPOSE: To assess the correlation of the selected structural and functional methods in the diagnosis of glaucoma. METHODS: The study group (SG) of 40 patients with primary open angle glaucoma with no or early visual field changes was compared to the control group (CG) of 40 healthy persons of similar age in the first year of prospective longitudinal study. All participants underwent the examination by means of Heidelberg retinal tomograph, photography of retinal nerve fiber layer, standard white-on-white perimetry, and blue-on-yellow perimetry. Only one eye of each examined person was evaluated. Significance was assessed by means of non-parametric test (Mann-Whitney) and the correlation analysis (Spearman) was performed as well. RESULTS: No significant differences in age, visual acuity, and refraction between SG and CG were found. The central corneal thickness (p< 0.05) and intraocular pressure (p< 0.01) were significantly different between both groups. The visual field mean sensitivity (MS) and mean defect (MD) of white-on-white perimetry differ significantly between SG and CG comparing to the visual field parameters of blue-on-yellow perimetry. HRT analysis found out significant parameters: cup area (CA), cup/disc ratio (C/D), rim/disc ratio (R/D), and rim volume (RV) (p< 0.05). Cup shape measure (CSM) and Mikelberg discrimination function (FSM) were significant as well (p< 0.01). The loss of retinal nerve fiber layer was significantly different (p< 0.01) between the glaucomatous and healthy eyes. Spearman's correlation analysis found out significant correlations (MS and MD) only in blue-on-yellow perimetry and CV and RV of HRT analysis by comparison of all healthy and glaucomatous eyes. Another significant correlations were found by comparison of the retinal nerve fiber layer loss to MS (p = 0.00) and MD (p = 0.03) of white-on-white perimetry. Some of HRT parameters: CA, RA, CD, RV, CSM, HVC and RNFL in the group of all 80 eyes were significantly correlated to retinal nerve fiber layer loss. In the group of glaucomatous eyes only, no significant correlations were found. CONCLUSION: Combination of the structural and functional methods can positively improve diagnosis of early glaucoma and better recognize the progression of glaucomatous neuropathy of the optical nerve.