We study the effect of channel fading in wireless power transfer (WPT) and show that fading enhances the RF-to-DC conversion efficiency of nonlinear RF energy harvesters. We then develop a new form ...of signal design for WPT, denoted as transmit diversity, that relies on multiple dumb antennas at the transmitter to induce fast fluctuations of the wireless channel. Those fluctuations boost the RF-to-DC conversion efficiency thanks to the energy harvester nonlinearity. In contrast with (energy) beamforming, transmit diversity does not rely on channel state information at the transmitter (CSIT) and does not increase the average power at the energy harvester input, even though it still enhances the overall end-to-end power transfer efficiency. Transmit diversity is also combined with recently developed (energy) waveform and modulation to provide further enhancements. The efficacy of the scheme is analyzed using physics-based and curve fitting-based nonlinear models of the energy harvester and demonstrated using circuit simulations, prototyping and experimentation. Measurements with two transmit antennas reveal gains of 50% in harvested DC power over a single transmit antenna setup. The work (again) highlights the crucial role played by the harvester nonlinearity and demonstrates that multiple transmit antennas can be beneficial to WPT even in the absence of CSIT.
The infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes the coronavirus disease 2019 (COVID-19) has threatened public health worldwide. The easy human-to-human ...transmission of this virus has rapidly evolved into a global pandemic. Therefore, to control the community spread of the virus, it is crucial to identify the infected individuals, including asymptomatic people. Hence, a specific and rapid assay is crucial for the early diagnosis and active monitoring of individuals potentially exposed to SARS-CoV-2 for controlling the COVID-19 outbreak. In this study, we have developed the novel lateral flow strip membrane (LFSM) assay that allows the simultaneous detection of RdRp, ORF3a, and N genes using the PCR product obtained by using the single-tube reverse transcription polymerase chain reaction (RT-PCR). The LFSM assay allows detection of SARS-CoV-2 in 30 min at 25 °C after the RT-PCR with the detection limit of 10 copies/test for each gene. The clinical performance of the LFSM assay for the detection of SARS-Cov-2 was evaluated using 162 clinical samples previously detected by using the commercial assay. The percent positive agreement, percent negative agreement, and overall percent agreement of the LFSM assay with the commercial assay were 100% (94.2–100%), 99.0% (94.6–100%), and 99.4% (96.6–100%), respectively. Therefore, the results of the LFSM assay showed significantly high concordance with the commercial assay for the detection of SARS-CoV-2 in clinical specimens. Therefore, we conclude that the developed LFSM assay can be used alone or complementary to the RT-PCR or other methods for the diagnosis and monitoring of the patients to curb community transmission and the pandemic.
This paper presents an electromyographic (EMG)-based continuous control scheme including simple classifier for an electric-powered wheelchair, ultimately for quadriplegics. The proposed scheme ...utilizes three EMG signals as inputs for the muscle-computer interface. Since zygomaticus major muscles and transversus menti muscle of human face are able to move independently as well as to adjust contractile forces voluntarily, the surface EMG signals on these muscles are utilized for the electric-powered wheelchair control system. To extract the envelopes of the signal waveforms and to reflect the moving average activities, the root-mean-squares (RMS) operation and normalization are subsequently employed as initial signal processing. Then, an activation vector containing three normalized RMS signals is obtained in real time. The activation vector is applied to the simple classifier for finding out the motion command. Both desired linear acceleration and angular velocity are yielded from the linear combinations of the classification result and the magnitude of activation vector. Finally, desired wheel velocities of the wheelchair control system are obtained by using the integration and differential inverse kinematics. The effectiveness of the proposed control scheme is verified through several experiments such as avoiding obstacle cones and navigating long distance by the users.
Reported herein is an unprecedented base‐promoted deborylative alkylation of pyridine N‐oxides using 1,1‐diborylalkanes as alkyl sources. The reaction proceeds efficiently for a wide range of ...pyridine N‐oxides and 1,1‐diborylalkanes with excellent regioselectivity. The utility of the developed method is demonstrated by the sequential C−H arylation and methylation of pyridine N‐oxides. The reaction also can be applied for the direct introduction of a methyl group to 9‐O‐methylquinine N‐oxide, thus it can serve as a powerful method for late‐stage functionalization.
Going to the source: The transition‐metal‐free alkylation of pyridine N‐oxides using 1,1‐diborylalkanes as alkyl sources proceeds efficiently for a wide range of pyridine N‐oxides and 1,1‐diborylalkanes with excellent regioselectivity, thus affording C2‐alkylated pyridines in good yields.
Brain organoids derived from human pluripotent stem cells provide a highly valuable in vitro model to recapitulate human brain development and neurological diseases. However, the current systems for ...brain organoid culture require further improvement for the reliable production of high-quality organoids. Here, we demonstrate two engineering elements to improve human brain organoid culture, (1) a human brain extracellular matrix to provide brain-specific cues and (2) a microfluidic device with periodic flow to improve the survival and reduce the variability of organoids. A three-dimensional culture modified with brain extracellular matrix significantly enhanced neurogenesis in developing brain organoids from human induced pluripotent stem cells. Cortical layer development, volumetric augmentation, and electrophysiological function of human brain organoids were further improved in a reproducible manner by dynamic culture in microfluidic chamber devices. Our engineering concept of reconstituting brain-mimetic microenvironments facilitates the development of a reliable culture platform for brain organoids, enabling effective modeling and drug development for human brain diseases.
Since its first report in Wuhan, China, in December 2019, the coronavirus disease (COVID-19) pandemic has significantly influenced our way of living 1. The World Health Organization proclaimed this ...disease a global pandemic on March 11, 2020. Since then, the Korean government has implemented social distancing measures. The number of confirmed cases of COVID-19 in Korea had reached 741,000 as of January 25, 2022, with a total of 6,565 deaths. During the pandemic, several governmental agencies and academic organizations have proposed recommendations for the elderly and those with chronic health conditions. The elderly, especially frail older adults, are more susceptible to negative health consequences. Regular physical activity increases one’s immune function 2. People who have an active lifestyle are less likely to acquire viral infections, and have lower severity of symptoms and mortality rates 2. Physical activity, such as walking, is crucial in preventing various adverse health outcomes in those with chronic illnesses and the elderly. However, for the elderly and chronically ill, social isolation and fear of acquiring COVID-19 significantly limit physical activity, leading to greater impairment and symptoms of depression 3,4. High levels of physical activity and immunity, even at old age, can help prevent viral infections and, if infected, lessen the severity of symptoms. Moderate-intensity exercise is promoted by international medical organizations, such as the World Health Organization, to enhance immunity. Even during the COVID-19 pandemic, regular exercise is included as a lifestyle guideline. However, during the pandemic, most of the world’s population, including South Korea, is encouraged to stay at home and avoid close contact with family and friends. Access to local amenities, such as gyms and parks, has been restricted to promote social distancing. In Korea, there are no guidelines on promoting physical activity during the COVID-19 pandemic. Academic exercise organizations should teach and advise the population on the benefits of engaging in physical activity, even during a pandemic. The fitness industry suffered significant financial losses due to the COVID-19 pandemic. However, the importance of exercise and physical fitness management is highly evident today. Performing high-intensity exercises in poorly ventilated indoor spaces may increase the risk of infection. However, rather than considering physical activity as a route of spreading COVID-19, government authorities should establish realistic and reasonable guidelines to maintain safety in exercising. Exercise experts and researchers should aim to create an environment that can allow one to maintain a healthy lifestyle through exercising safely amid the COVID-19 pandemic. KCI Citation Count: 0
Enzymatically induced carbonate precipitation (EICP) using urea hydrolysis is a well-known bio-cementation process that not only promotes the precipitation of calcium carbonate (CaCO
) but can ...provide excess calcium cations for further reaction depending on the substrate constituents and reaction stage. This study presents the EICP recipe to contain sulfate ions in landfill leachate sufficiently using remaining calcium cations and a series of tests were conducted to validate its ability to retain sulfates. The reaction rate for 1 M CaCl
and 1.5 M urea was identified by controlling the purified urease content and the curing time of the EICP process. The results showed that 0.3 g/L of purified urease produced 46% CaCO
and reduced sulfate ions by 77% after 3 days of curing. The shear stiffness in EICP-treated sand was enhanced 13 times by CaCO
precipitation followed by 1.12 times increment due to subsequent precipitation of gypsum (CaSO
·2H
O) crystals implying sulfate containment. A cost-efficient EICP treatment using soybean crude urease instead of lab-grade purified urease exhibited lower sulfate removal efficiency (i.e., 18%) with only nominal formation of gypsum in the EICP-treated sand. The addition of gypsum powder was effective in increasing sulfate removal by 40% when soybean crude urease was used for EICP.
OBJECTIVES Age-related loss of muscular strength may contribute to medical health condition. Decreased handgrip strength is associated with an increased risk of chronic diseases, disability, and ...mortality. However, it is not known whether handgrip strength is also linked with hospitalization and medical use from the long-term cohort study in middle-aged adults. Thus, we aimed to investigate the association of handgrip strength levels, medical use, and hospitalization in Korean adults.METHODS This large prospective study was based on data from Korean Longitudinal Study of Ageing 2006 to 2018. In total, 9,228 participants aged ≥45 years were included for this study. Handgrip strength was measured using dynamometer, and classified into quartiles by sex-specific cutoff point.RESULTS Significantly higher hazard ratio (HR) for hospitalization was observed in lower handgrip strength (HR: 1.22, 95% CI:1.11-1.34) compared to higher handgrip strength (reference) in the fully adjusted model. We also found longitudinal association of handgrip strength levels and the use of hospitalization and outpatient medical care during 12 years following period using mixed effect modes with time-dependent interaction.CONCLUSIONS Our results suggests that lower handgrip strength was associated with increased the risk of hospitalization and use of medical care in Korean population. This study highlights the maintaining of muscular strength may play an important role in the reduction of risk for hospitalization and medical use by preventing chronic diseases.
Dementia is one of the priority public health problems in the older population, and the number of people with dementia is steadily increasing. The longitudinal association of muscle strength with ...risk of new-onset cognitive dysfunction in a general population including middle and older adults remains unknown. The purpose of this study was to investigate the effects of low muscle strength on risk for new-onset cognitive dysfunction over 6 years using a large nationwide sample of cognitively healthy adults. Study participants included 6,435 middle and older adults (33,554 person-years of follow-up), using data from the Korean Longitudinal Study of Ageing 2006-2012. Muscular strength was measured using the maximum handgrip strength of each participant as an index of muscle quality. Low muscle strength was defined as one standard deviation below the mean using the handgrip strength index based on the study population. Cognitive function was evaluated using the Mini-Mental Status Evaluation. The hazard ratio (HR) for cognitive dysfunction significantly and linearly increased according to muscle strength status independent of potential confounding factors (HR: 1.36, 95% confidence interval CI: 1.18-1.56 for low vs. normal-high group). Using stratified analyses, a significant association between muscle strength status and risk of cognitive impairment was observed in those with low physical activity, but not those with high physical activity. We show that handgrip strength is associated with increased risk of new-onset cognitive dysfunction over 6 years of follow-up in cognitively healthy middle aged and older adults at baseline.
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