Conduction and Resistive Switching Memory in Al/MoS2+PVP/Ag Devices Fabricated using Drop cast Method

Resistive switching in MoS2 embedded PVP composite-based ReRAM with Al and Ag electrodes is reported. A cost-free drop cast method was used to deposit active layers consisting of 30 wt%, 40 wt%, and 70 wt% of MoS2 in PVP. Each system exhibited unique electroforming and switching mode. Asymmetrical bipolar resistive switching occurring only in the positive voltage bias, a typical bipolar resistive switching and a typical ‘O-type’ resistive switching were observed for the 30 wt%, 40 wt%, and 70 wt% systems, respectively. Furthermore, injection of charge carriers at the electrode/active layer interface and electrochemical metalization mechanisms drove the formation of a nanoscale conductive filament in the device A and B. On the other hand, we attributed the conduction mechanism of device C to hopping conduction. Our results demonstrate the behaviour of MoS2 embedded PVP composite-based ReRAM has a strong dependence on the amount of MoS2 and that both the switching and conduction mechanism can be exploited by controlling the amount of MoS2 in the composite.

Protocol for Safely Collecting Saliva as a Biospecimen During and Post the COVID-19 Pandemic

The emergence of salivary bioscience began in the 1980’s, around the same time that researchers discovered we could assess cortisol through the gathering of saliva. In recent decades, the field of salivary bioscience has exponentially grown in scientific interest. This is likely due to the fact that interest in salivary cortisol has risen as well as the emergence of noninvasive procedures to collect other biomarkers of health (e.g., c-reactive protein, alpha amylase, uric acid) through saliva. However, the global health crisis caused by coronavirus disease 2019 (COVID-19) has presented challenges to biomedical researchers. The current manuscript provides detailed guidelines for safely collecting saliva as a biospecimen during and post the era of COVID-19. The protocol has six sections: screenings, package creation and mailing, sample collection demonstration, a contact-free drop-off or pick-up, text message reminders, and storage. Depending on participant screening responses and consistent with quarantine timelines suggested by the Center for Disease Control and Prevention (CDC), the entire protocol can be completed between 4 to 18 days, excluding package creation and mailing. The steps outlined can be accommodated by scientists with developing and mastery level expertise. The protocol can be applied to existing salivary bioscience protocols and maximize safety in the presence of other infectious diseases.

Numerical investigation of the turbulence characteristics and energy dissipation mechanism of baffle drop shafts

The baffle drop shaft is widely used in deep tunnel drainage system due to its fine applicability and high energy dissipation. To fully study the turbulence characteristics and energy dissipation mechanism of baffle drop shafts, a 1:25 scale physical model test and the numerical simulation based on the Realizable k-ε model and Volume of Fluid (VOF) method were performed. The results showed that a baffle spacing that is too dense or too sparse is not conducive to energy dissipation and discharge. The minimum baffle spacing is the optimal structural design at the design flow rate when the flow regime is free-drop flow. The energy dissipation calculation model established in this paper has high accuracy for calculating the energy dissipation rate on the baffles in free-drop flow. The energy dissipation modes of the shaft can be divided into inlet energy dissipation, baffle energy dissipation, and shaft-bottom energy dissipation. Baffles play a major role in the energy dissipation at low flow rates, and the proportions of inlet and shaft-bottom energy dissipation increase with the increase in flow rate.

Bruise Patterns of Fresh Market Apples Caused by Fruit-to-Fruit Impact

Comprehensive understanding of bruise damage caused by apple-to-apple impacts is beneficial to design a low-impact fruit capturing mechanism for mass (shake-and-catch) harvesting, as well as to design other fruit handling devices. This study quantified the bruising severity in ‘Jazz’ apples induced by different levels of impact upon various fruit surface locations. Impact experiments were carried out to analyze bruising patterns in three zones in a fruit surface, i.e., middle/cheek-to-top/stem, middle-to-middle and middle-to-bottom/calyx. Moving fruit and stationary fruit were impacted using a pendulum-type test device, and an equivalent drop height of fruit was calculated to provide a more practical measure for designing a catching surface. In each impact zone, seven different levels of impacts were applied respectively at seven different locations on the fruit surface. Those locations were evenly distributed along the circumferential direction in each of the three zones, and moving fruit was replaced after each impact test. The United States Department of Agriculture (USDA) standard was then used to estimate percentages of fruit in the Extra Fancy Class 1 (no bruising), Extra Fancy (a bruising area diameter ≤ 12.7 mm) and Fresh Market (a bruising area diameter ≤ 19 mm) grades. Results showed that fruit bruising severity increased in a non-linear manner with increasing drop height. It was also found that there existed significant differences in fruit bruising severity between stationary and moving fruit under different fruit-to-fruit impact zones. The bottom zone showed the least bruising sensitivity, followed by the middle zone which was statistically similar to the same in the top zone. The results suggested that the free drop height need to be <3 cm to keep from fruit bruising caused by apple-to-apple impact at a negligible level for ‘Jazz’ apples.