A Single-Stage Passive Vibration Isolation System for Scanning Tunneling Microscopy

Scanning Tunneling Microscopy (STM) uses quantum tunneling effect to study the surfaces of materials on an atomic scale. Since the probe of the microscope is on the order of nanometers away from the surface, the device is prone to noises due to vibrations from the surroundings. To minimize the random noises and floor vibrations, passive vibration isolation is a commonly used technique due to its low cost and simpler design compared to active vibration isolation, especially when the entire vibration isolation system (VIS) stays inside an Ultra High Vacuum (UHV) environment. This research aims to analyze and build a single-stage passive VIS for an STM. The VIS consists of a mass-spring system staying inside an aluminum hollow tube. The mass-spring system is comprised of a circular copper stage suspended by a combination of six extension springs, and the STM stays on top of the copper stage. Magnetic damping with neodymium magnets, which induces eddy currents in the copper conductor, is the primary damping method to reduce the vibrations transferred to the mass-spring system. FEMM and MATLAB® are used to model magnetic flux density and damping coefficients from eddy current effect, which will help determine the necessary damping ratios for the VIS. Viton, which demonstrates a high compatibility with vacuum environments, will also serve as a great damping material between joints and contacts for the housing tube. Viton will be modeled as a Mooney-Rivlin hyperelastic material whose material parameters are previous studied, and Abaqus will be used as a Finite Element Analysis software to study the Viton gaskets’ natural frequencies. The natural frequencies of the aluminum hollow tube will also be investigated through Abaqus

Autonomous Vehicles Operating Collaboratively to Avoid Debris and Obstructions

The purpose of this project is to demonstrate the safety and increased fuel efficiency of an automated collision avoidance system in collaborative vehicle platooning. This project was cosponsored by Daimler Trucks North America headquartered in Portland, Oregon, as well as Dr. Birdsong, and Dr. DeBruhl of Cal Poly. The mechanical engineering team consists of Cole Oppenheim, James Gildart, Toan Le, and Kyle Bybee who worked in coordination with a team of computer engineers. Vehicle platooning is a driving technique to increase the fuel efficiency of a group of vehicles by following a lead vehicle closely to reduce the drag experienced by the group. Specifically, large tractor trailer trucks could become more efficient utilizing vehicle platooning. To implement this system most effectively would require an automatic system for collision avoidance. The goal for the mechanical engineering team working on this project was build and design two scale model vehicles, a test track, and dynamic models of the vehicles. These were then interface with computer vision software and hardware (created in collaboration of a team of computer engineers) that allows the vehicles to autonomously platoon and avoid objects that would otherwise cause a collision. Interactions with the computer engineering team occurred at minimum on a weekly basis and more whenever necessary. Interactions between the team’s original occurred as meetings to determine each team individual progress until integration could be accomplished. When the systems were being integrated, meetings occurred regularly (2-3 times a week) to ensure the vehicles could properly execute their design function. The goal of this project is to demonstrate how this system could be implemented in truck platooning safely and to demonstrate the advantages of platooning with system developed. This project was intended and will be presented to compete at the Enhanced Safety of Vehicles conference in the Netherlands in June of 2019. This report covers the scope of work of this project, the preliminary design direction, and the final design direction, and the final design for the assembly of the two 1/10 scale cars, the track design, and the controls strategy to interface with the CPE’s software

The Association Between Ambient Temperatures and Hospital Admissions Due to Respiratory Diseases in the Capital City of Vietnam

This study aimed to examine the short-term effects of ambient temperature on hospital admissions due to respiratory diseases among Hanoi residents. We collected 34,653 hospital admissions for 365 days (November 1, 2017, to November 31, 2018) from two hospitals in Hanoi. A quasi-Poisson regression model with time series analysis was used to explore the temperature-health outcome relationship's overall pattern. The non-linear curve indicated the temperatures with the lowest risk range from 22 degrees (Celcius) to 25 degrees (Celcius). On average, cold temperatures showed a higher risk than hot temperatures across all genders and age groups. Hospital admissions risk was highest at 13 degrees (Celcius) (RR = 1.39; 95% CI = 1.26–1.54) for cold effects and at 33 degrees (Celcius) (RR = 1.21, 95% CI = 1.04–1.39) for the hot effects. Temporal pattern analysis showed that the most effect on respiratory diseases occurred at a lag of 0 days for hot effect and at a lag of 1 day for cold effect. The risk of changing temperature among women and people over 5 years old was higher than other groups. Our results suggest that the risk of respiratory admissions was greatest when the temperature was low. Public health prevention programs should be enhanced to improve public awareness about the health risks of temperature changes, especially respiratory diseases risked by low temperatures

Antibacterial hydrogel containing Piper betle L. extract for acne treatment, an ex vivo investigation

The current treatments of acne vulgaris and acne-like disorders such as gram-negative folliculitis possess lots of unwanted side effects. Thus, alternative approach of utilizing natural plant extracts, specifically Piper betle L., have gained much attention. To this end, this work developed, characterized, and ex vivo evaluated novel antibiotics hydrogels containing P. betle L. leaf extract for acne treatment. Firstly, the design of experiments (DoE) D-optimal method was successfully developed, optimized, and validated, to investigate the relationship between P. betle L. extraction conditions and the extract properties. Secondly, the best extract was encapsulated in the hydrogel formulations composed of carbopol 940, propylene glycol, and cocamidopropyl betaine. Finally, the hydrogel was ex vivo determined its antibacterial activity on bacteria isolated from 15 patient acne samples. The optimal extraction condition being an extraction solvent/plant weight ratio of 4.034:1, an extraction time of 2.147 h, and a water extract volume of 91.4 mL. This condition yielded an extract total phenolic content of 3.337±0.034 g GAE/g, and minimum inhibitory concentrations of 32 µg/mL and 128 µg/mL on Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922, respectively. The hydrogel possessed suitable properties for a topical medication, including a viscosity of 6800 cps, a pH of 7.0, and a good foaming ability, at both 10°C, 25°C, and 40°C. The hydrogel showed higher antibacterial activity than the positive controls in both gram-positive and gram-negative bacteria. Conclusively, the hydrogel could become a potential pharmaceutical product for acne treatment

Optimal User Pairing Approach for NOMA-based Cell-free Massive MIMO Systems

This study investigates a non-orthogonal multiple access (NOMA)-assisted cell-free massive multiple-input multiple-output (MIMO) system, considering the impact of both individual and linear-combination channel estimations. To make the best use of NOMA as an enabler for cell-free massive MIMO systems, user pairing should be employed effectively. Random user pairing naturally leads to a non-optimal solution, whereas an exhaustive search approach is unfavorable for practical systems owing to the high complexity. In this study, we propose an optimal user pairing strategy to group users that jointly optimize the minimum downlink rate per user and power allocation at an acceptable cost of complexity. To address this problem, we first relax the binary variables to continuous variables and then develop an iterative algorithm based on the inner approximation method, yielding at least one locally optimal solution. Numerical results show that the proposed user pairing algorithm outperforms existing counterparts, such as conventional beamforming, random pairing, far pairing, and close-pairing strategies, while it can be performed dynamically, that is, two arbitrary users satisfying the formulated problem can be paired regardless of geographical distance. Finally, our approach demonstrates that the combination channel estimation-based NOMA-assisted cell-free massive MIMO achieves the best result in terms of the downlink rate per user when associated with the proposed algorithm

Co-infection of human parvovirus B19 with Plasmodium falciparum contributes to malaria disease severity in Gabonese patients

Background: High seroprevalence of parvovirus B19 (B19V) coinfection with Plasmodium falciparum has been previously reported. However, the impact of B19V-infection on the clinical course of malaria is still elusive. In this study, we investigated the prevalence and clinical significance of B19V co-infection in Gabonese children with malaria. Methods: B19V prevalence was analyzed in serum samples of 197 Gabonese children with P. falciparum malaria and 85 healthy controls using polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and direct DNA-sequencing. Results: B19V was detected in 29/282 (10.28%) of Gabonese children. B19V was observed more frequently in P. falciparum malaria patients (14.21%) in comparison to healthy individuals (1.17%) (

Women’s involvement in coffee agroforestry value-chains: Financial training, Village Savings and Loans Associations, and Decision power in Northwest Vietnam

Globally, in the coffee sector and smallholder agriculture in developing countries, there is a distinct gender gap in key factors that enable women’s active participation in and contribution to the coffee value chain and in farm and domestic decisions, such as decisions over credit, agricultural inputs, and training opportunities and division of labor and time. This study assesses Village Savings and Loans Associations (VSLA) impacts and related training on gender equality and women’s access to coffee markets in an ongoing coffee- project in northwest Vietnam. All 169 women in this survey received gender equality and finance training, with one group being members of a VSLA and taking out small loans. With Women’s Empowerment in Agriculture Index (WEAI), women rated their perception of their decision-making power over a range of 18 tasks related to household and agricultural responsibilities and use of income and social activities over 18 months. There were significant improvements in decision-making power in categories with previously low participation and increased sharing of domestic responsibilities. The categories with the biggest gains were decision-making over large purchases and use of income, especially for VSLA-members who sought out market information before engaging with potential coffee buyers and enhanced their negotiating abilities to arrange more favorable outcomes successfully. These results indicate that active gender and finance training translated to real changes in gender dynamics, and membership of a VSLA also helped women improve their financial literacy and improve their negotiating abilities. Husbands to women in the study also began to reconsider gender roles and shift towards equal sharing of responsibility and decision- making with their wives. Based on this study, we recommend (1) implementing gender and finance training and enabling access to loans for women as a means for their inclusion in agriculture value chains, and (2) engaging the whole household in gender training in order for all family members to be receptive to adjustments in the gender division of responsibility, labor and decision-making. The results indicate the conditions under which women can benefit from activities involving agroforestry systems that also enhance carbon sequestration for climate change mitigation compared to coffee monoculture

A Multinational Data Set of Game Players' Behaviors in a Virtual World and Environmental Perceptions

Video gaming has been rising rapidly to become one of the primary entertainment media, especially during the COVID-19 pandemic. Playing video games has been reported to associate with many psychological and behavioral traits. However, little is known about the connections between game players' behaviors in the virtual environment and environmental perceptions. Thus, the current data set offers valuable resources regarding environmental worldviews and behaviors in the virtual world of 640 Animal Crossing: New Horizons (ACNH) game players from 29 countries around the globe. The data set consists of six major categories: 1) socio-demographic profile, 2) COVID-19 concern, 3) environmental perception, 4) game-playing habit, 5) in-game behavior, and 6) game-playing feeling. By making this data set open, we aim to provide policymakers, game producers, and researchers with valuable resources for understanding the interactions between behaviors in the virtual world and environmental perceptions, which could help produce video games in compliance with the United Nations (UN) Sustainable Development Goals