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.
Recent research has focused on a new group called the "weekend warriors". These individuals accumulate their recommended moderate to vigorous physical activity (MVPA) over just 1-2 days, often during ...weekends, while remaining relatively inactive during the rest of the week. However, the effects of engaging in low-frequency MVPA on the risk of metabolic syndrome (MetS) are not well understood. This study investigated the association between physical activity patterns and the risk of MetS among Korean adults.BackgroundRecent research has focused on a new group called the "weekend warriors". These individuals accumulate their recommended moderate to vigorous physical activity (MVPA) over just 1-2 days, often during weekends, while remaining relatively inactive during the rest of the week. However, the effects of engaging in low-frequency MVPA on the risk of metabolic syndrome (MetS) are not well understood. This study investigated the association between physical activity patterns and the risk of MetS among Korean adults.This study included 26,197 participants (11,804 male and 14,393 female) aged ≥ 20 years from the Korea National Health and Nutrition Examination Survey. MVPA was measured using a global physical activity questionnaire. MetS was defined as the presence of more than three risk factors.MethodsThis study included 26,197 participants (11,804 male and 14,393 female) aged ≥ 20 years from the Korea National Health and Nutrition Examination Survey. MVPA was measured using a global physical activity questionnaire. MetS was defined as the presence of more than three risk factors.The odds ratio (OR) for MetS was 0.60 (95% confidence interval CI = 0.52, 0.70) in the "regularly active" group and 0.82 (95% CI = 0.69, 0.98) in the "weekend warrior" group compared to that in the inactive group (reference), which controlled for all covariates. For sensitivity analyses, the results across all subgroups exhibited similar patterns, with more pronounced effects observed in women, middle-aged individuals, and non-drinkers/light drinkers.ResultsThe odds ratio (OR) for MetS was 0.60 (95% confidence interval CI = 0.52, 0.70) in the "regularly active" group and 0.82 (95% CI = 0.69, 0.98) in the "weekend warrior" group compared to that in the inactive group (reference), which controlled for all covariates. For sensitivity analyses, the results across all subgroups exhibited similar patterns, with more pronounced effects observed in women, middle-aged individuals, and non-drinkers/light drinkers.Our findings suggest that concentrated bouts of moderate to vigorous physical activity, even if undertaken infrequently, confer health benefits that align with the recommended guidelines. This study contributes to the growing evidence on the relationship between physical activity patterns and MetS risk in Korean adults. The study also emphasizes the potential of different activity patterns in mitigating metabolic risk.ConclusionsOur findings suggest that concentrated bouts of moderate to vigorous physical activity, even if undertaken infrequently, confer health benefits that align with the recommended guidelines. This study contributes to the growing evidence on the relationship between physical activity patterns and MetS risk in Korean adults. The study also emphasizes the potential of different activity patterns in mitigating metabolic risk.
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.
Waste Expanded polypropylene (EPP) was utilized as recycled matrix for kenaf fiber-reinforced polypropylene (PP) composites produced using chopped kenaf fibers and crushed EPP waste. The flexural ...properties, impact strength, and heat deflection temperature (HDT) of kenaf fiber/PP composites were highly enhanced by using waste EPP, compared to those by using virgin PP. The flexural modulus and strength of the composites with waste EPP were 98% and 55% higher than those with virgin PP at the same kenaf contents, respectively. The Izod impact strength and HDT were 31% and 12% higher with waste EPP than with virgin PP, respectively. The present study indicates that waste EPP would be feasible as recycled matrix for replacing conventional PP matrix in natural fiber composites.
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