Here we report that alfalfa-derived nitrogen-doped porous carbon (NPC) fabricated by a pyrolysis method is electrochemically active for the N2 reduction reaction (NRR) at ambient conditions. The ...results demonstrate that the obtained NPC material with a nitrogen content of 6.35 atom % at 500 °C (NPC-500) exhibits high NRR activity with an NH3 yield rate of 1.31 mmol h–1 g–1 cat. and a Faradaic efficiency of 9.98% at −0.4 V (vs RHE) in 0.005 M H2SO4 solution. The isotopic labeling experimental results using 15N2 feed gas and 15NPC-500 reveal that the yielded NH3 indeed resulted from the NPC-500 catalyzed NRR, and the doped pyridinic-N also contributes NH3 formation during NRR. The experimental and theoretical calculations results indicate that the doped pyridinic-N in the NPC catalyst during NRR can break away from its surface to form N vacancies in a carbon matrix as the catalytic active sites for N2 adsorption and activation.
As the modern navigation business evolves, demands for high-precision positioning in GNSS-challenged environments increase, and the integrated system composed of Global Navigation Satellite System ...(GNSS)-based Real-Time Kinematic (RTK), inertial system (INS), Light Detection and Ranging (LiDAR), etc., is accepted as the most feasible solution to the issue. For prior-map-free situations, as the only sensor with a global frame, RTK determines and maintains the global positioning precision of the integrated system. However, RTK performance degrades greatly in GNSS-challenged environments, and most of the existing integrated systems adopt loose coupling mode, which does nothing to improve RTK and, thus, prevents integrated systems from further improvement. Aiming at improving RTK performance in the RTK/LiDAR/INS integrated system, we proposed an innovative integrated algorithm that utilizes RTK to register LiDAR features while integrating the pre-registered LiDAR features to RTK and adopts parallel filters in the ambiguity-position-joint domain to weaken the effects of low satellite availability, cycle slips, and multipath. By doing so, we can improve the RTK fix rate and stability in GNSS-challenged environments. The results of the theoretical analyses, simulation experiments, and a road test proved that the proposed method improved RTK performance in GNSS-challenged environments and, thus, guaranteed the global positioning precision of the whole system.
Vehicles driving in urban canyons are always confronted with a degraded Global Navigation Satellite System (GNSS) signal environment. The surrounding obstacles may cause signal reflections or ...blockages, which lead to large multipath noises and intermittent GNSS reception. Under these circumstances, it is not feasible to use conventional real-time kinematic (RTK) algorithms to maintain high-precision performance for positioning. In order to meet the special requirements of safety-critical applications under non-ideal observation conditions, a novel tightly coupled RTK/Inertial Navigation System (INS) algorithm is proposed in this paper, which can provide accurate and reliable positioning results continuously. Our integrated RTK/INS algorithm has three features. Firstly, INS measurements are used to help search for integer ambiguities in the position domain. INS solutions can provide a more accurate initial location and a more efficient search region. Secondly, the criterion for determining whether a candidate position is the correct solution is only related to the fractional value of the carrier-phase measurement. Thus, the new algorithm is immune to cycle slips as well as large pseudorange noises. Thirdly, our algorithm can provide more accurate ranging information than the pseudorange, even though it may not necessarily be fixed successfully, because it selects the weighted ambiguity solution as the result rather than the candidate point with maximum probability. The proposed algorithm is demonstrated on both simulated and real datasets. Compared with single epoch RTK and conventional tightly coupled RTK/INS integrations that search integer ambiguities in the ambiguity domain, our method attains better accuracy and stability in a simulated environment. Moreover, the real experimental results are presented to validate the performance of the new integrated navigation algorithm.
Electroadhesive grippers can be used to pick up a wide range of materials, and those with variable stiffness functionality can increase load capacity and strength. This paper proposes an ...electroadhesive gripper (VSEAF) with variable stiffness function and a simple construction based on low melting point alloys (LMPAs) with active form adaptation through pneumatic driving. Resistance wires provide active changing stiffness. For a case study, a three-fingered gripper was designed with three electroadhesive fingers of varied stiffness. It is envisaged that these electroadhesive grippers with variable stiffness would extend the preparation process and boost the use of electroadhesion in soft robot applications.
This paper concerns the nature of the peculiar second-order buoyancy experienced by a magnet in magnetic fluid acceleration sensor. The equilibrium differential equation of magnetic fluid under the ...action of magnetic field and gravity field is established and the expression for calculating the second-order buoyancy is derived. Three practical and effective methods to calculate the second-order buoyancy called surface integral method, magnetic force method, and equivalent magnetic force method are proposed. Besides, the second-order buoyancy is calculated by the three methods mentioned above and measured experimentally. The calculation results are in very good agreement with the experimental results, for all the three methods, the calculation error is less than 7% compared with the numerical range of second-order buoyancy. Both calculation and experimental results show that the second-order buoyancy increases rapidly with the decrease of the axial distance between the bottom of the magnet and the container, and the trend can be fitted well by an exponential function.
The Ross-Amundsen sector is experiencing an accelerating warming trend and a more intensive advective influx of marine air streams. As a result, massive surface melting events of the ice shelf are ...occurring more frequently, which puts the West Antarctica Ice Sheet at greater risk of degradation. This study shows the connection between surface melting and the prominent intrusion of warm and humid air flows from lower latitudes. By applying the Climate Feedback-Response Analysis Method (CFRAM), the temporal surge of the downward longwave (LW) fluxes over the surface of the Ross Ice Shelf (RIS) and adjacent regions are identified for four historically massive RIS surface melting events. The melting events are decomposed to identify which physical mechanisms are the main contributors. We found that intrusions of warm and humid airflow from lower latitudes are conducive to warm air temperature and water vapor anomalies, as well as cloud development. These changes exert a combined impact on the abnormal enhancement of the downward LW surface radiative fluxes, significantly contributing to surface warming and the resultant massive melting of ice.
Diabetes is associated with beta cell mass loss and islet dysfunctions. mTORC1 regulates beta cell survival, proliferation and function in physiological and pathological conditions, such as pregnancy ...and pancreatectomy. Here we show that deletion of Raptor, which is an essential component of mTORC1, in insulin-expressing cells promotes hypoinsulinemia and glucose intolerance. Raptor-deficient beta cells display reduced glucose responsiveness and exhibit a glucose metabolic profile resembling fetal beta cells. Knockout islets have decreased expression of key factors of functional maturation and upregulation of neonatal markers and beta cell disallowed genes, resulting in loss of functional maturity. Mechanistically, Raptor-deficient beta cells show reduced expression of DNA-methyltransferase 3a and altered patterns of DNA methylation at loci that are involved in the repression of disallowed genes. The present findings highlight a novel role of mTORC1 as a core mechanism governing postnatal beta cell maturation and physiologic beta cell mass during adulthood.
The increasing resistance of pathogens to antibiotics causes a huge clinical burden that places great demands on academic researchers and the pharmaceutical industry for resolution. Antimicrobial ...peptides, part of native host defense, have emerged as novel potential antibiotic alternatives. Among the different classes of antimicrobial peptides, proline-rich antimicrobial peptides, predominantly sourced from insects, have been extensively investigated to study their specific modes of action. In this review, we focus on recent developments in these peptides. They show a variety of modes of actions, including mechanism shift at high concentration, non-lytic mechanisms, as well as possessing different intracellular targets and lipopolysaccharide binding activity. Furthermore, proline-rich antimicrobial peptides display the ability to not only modulate the immune system via cytokine activity or angiogenesis but also possess properties of penetrating cell membranes and crossing the blood brain barrier suggesting a role as potential novel carriers. Ongoing studies of these peptides will likely lead to the development of more potent antimicrobial peptides that may serve as important additions to the armoury of agents against bacterial infection and drug delivery.
The World Health Organisation has deemed several multi-drug resistant (MDR) nosocomial bacterial pathogens to be of significant threat to human health. A stark increase in morbidity, mortality and ...the burden to healthcare systems around the world can be attributed to the development of resistance in these bacteria. Accordingly, alternative antimicrobial agents have been sought as an attractive means to combat MDR pathogens, with one such example being antimicrobial peptides (AMPs). Given the reported activity of AMPs, including Pardaxin, MSI-78, dermaseptin-PC (DMPC) and Cecropin B, it is important to understand their activities and modes of action against bacteria for further AMP design. In this study, we compared these AMPs against a panel of nosocomial bacterial pathogens, followed by detailed mechanistic studies. It was found that Pardaxin (1–22) and MSI-78 (4–20) displayed the most pronounced antimicrobial activity against the tested bacteria. The mechanistic studies by membrane permeability and molecular dynamics simulation further confirmed the strong membrane interaction and structure of Pardaxin (1–22) and MSI-78 (4–20), which contributed to their potent activity. This study demonstrated a structure and activity guidance for further design of Pardaxin (1–22) and MSI-78 (4–20) as therapeutics against MDR pathogens. The different effects of DMPC (1–19) and Cecropin B (1–21) on membrane integrity and phospholipid membrane interactions provided critical information for the rational design of next-generation analogues with specificity against either Gram-negative or Gram-positive bacteria.
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•Detailed activity and mechanistic studies of AMPs, including Pardaxin, MSI-78, dermaseptin-PC (DMPC) and Cecropin B, against a panel of Gram-negative and Gram-positive bacteria.•The most active Pardaxin (1–22) and MSI-78 (4–20) displayed strong membrane activity towards Gram-negative and Gram-positive bacteria.•Different mechanisms of DMPC (1–19) and Cecropin B (1–21) against Gram-negative and Gram-positive bacteria will guide the rational design of new AMP analogues.•Molecular dynamics simulation further provided the details of their structure and activity relationship.
The aim of this study was to conduct a meta-analysis of retrospective studies that investigated the association of preoperative C-reactive protein (CRP) levels with the overall survival (OS) of ...patients with bone neoplasms.
A detailed literature search was performed in the Cochrane Library, Web of Science, Embase and PubMed databases up to August 28, 2017, for related research publications written in English. We extracted the data from these studies and combined the hazard ratios (HR) and 95% confidence intervals (CIs) to assess the correlation between CRP levels and OS in patients with bone neoplasms.
Five studies with a total of 816 participants from several countries were enrolled in this current meta-analysis. In a pooled analysis of all the publications, increased serum CRP levels had an adverse prognostic effect on the overall survival of patients with bone neoplasms. However, the combined data showed no significant relationship between the level of CRP and OS in Asian patients (HR = 1.73; 95% CI: 0.86-3.49; P = 0.125). Similar trends were observed in patients with bone neoplasms when stratified by ethnicity, histology, metastasis and study sample size.
The results of this meta-analysis suggest that increased CRP expression indicates a poorer prognosis in patients with bone neoplasms. More prospective studies are needed to confirm the prognostic significance of CRP levels in patients with bone neoplasms.
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