Process optimization & kinetic modeling study for fresh microgreen (Alternanthera sessilis) juice treated under thermosonication.

Several experimental studies suggest the regular consumption of vegetables can marginally reduce the risk of chronic disease and nutrient deficiency. However, the average consumption rate of vegetables is still limited. Microgreens are emerging fresh produce, rich in nutrients, intense flavor, delicate texture, and culinary application. Microgreens juices are the potential alternative for nutrient deficiency and chronic disease due to their bioavailability of bioactive compounds. However, no scientific data are available on the process optimization of microgreens juices under thermosonication (TS). The present study focused on the process optimization of thermosonication (30-50 °C, and 20-35 min at constant 44 kHz) and its effect against the physical, chemical, and microbial nature of microgreen juice. Thermosonicated juice sample showed no significant difference in pH, TSS & TA throughout the process. But, a significant range was observed in the antioxidant (41.63 ± 1.05 to 53.86 ± 1.20), phenolic (0.54 ± 0.02 to 0.74 ± 0.02), and flavonoid (1.42 ± 0.01 to 1.63 ± 0.01) level in the treated juice sample. Likewise, the treated juice exhibits complete inactivation of the bacterial load. Our finding discloses, the quality enrichment of TS juice increased with the rise in temperature & time.

Full-field microscale strain measurements of a nitinol medical device using digital image correlation.

Computational modeling and simulation are commonly used during the development of cardiovascular implants to predict peak strains and strain amplitudes and to estimate the associated durability and fatigue life of these devices. However, simulation validation has historically relied on comparison with surrogate quantities like force and displacement due to barriers to direct strain measurement-most notably, the small spatial scale of these devices. We demonstrate the use of microscale two-dimensional digital image correlation (2D-DIC) to directly characterize full-field surface strains on a nitinol medical device coupon under emulated physiological and hyperphysiological loading. Experiments are performed using a digital optical microscope and a custom, temperature-controlled load frame. Following applicable recommendations from the International DIC Society, hardware and environmental heating studies, noise floor analyses, and in- and out-of-plane rigid body translation studies are first performed to characterize the microscale DIC setup. Uniaxial tension experiments are also performed using a polymeric test specimen to characterize the strain accuracy of the approach up to nominal stains of 5%. Sub-millimeter fields of view and sub-micron displacement accuracies (9nm mean error) are achieved, and systematic (mean) and random (standard deviation) errors in strain are each estimated to be approximately 1,000µÏµ. The system is then demonstrated by acquiring measurements at the root of a 300µm-wide nitinol medical device strut undergoing fixed-free cantilever bending motion. Lüders-like transformation bands are observed originating from the tensile side of the strut that spread toward the neutral axis at an angle of approximately 55°. Despite the inherent limitations of optical microscopy and 2D-DIC, simple and relatively economical setups like that demonstrated herein could provide a practical and accessible solution for characterizing cardiovascular implant micromechanics, validating computational model strain predictions, and guiding the development of next-generation material models for simulating superelastic nitinol.

Influence of microstructural purity on the bending fatigue behavior of VAR-melted superelastic Nitinol.

The bending fatigue resistance of commercially-available Standard versus High Purity Nitinol was evaluated at 3% mean strain and a range of strain amplitudes with the simple wire Z-specimen geometry. The Standard grade Nitinol demonstrated a 10(7)-cycle fatigue strain limit of 0.50% alternating strain, comparable to results reported elsewhere in the literature. Conversely, the High Purity grade VAR Nitinol demonstrated a 5-fold improvement in fatigue resistance with an impressive 10(7)-cycle fatigue strain limit of 2.5% alternating strain. The High Purity Nitinol has an oxygen+nitrogen content of 60wppm, maximum wrought-material inclusion length of 17µm, and inclusion volume fraction of 0.28%, all substantially less than industry standards. With all processing variables held constant except for inclusion content, it is clear that this marked fatigue superiority is due exclusively to the reduction in both size and area fraction of inclusions.