A qrr noncoding RNA deploys four different regulatory mechanisms to optimize quorum-sensing dynamics.

Quorum sensing is a cell-cell communication process that bacteria use to transition between individual and social lifestyles. In vibrios, homologous small RNAs called the Qrr sRNAs function at the center of quorum-sensing pathways. The Qrr sRNAs regulate multiple mRNA targets including those encoding the quorum-sensing regulatory components luxR, luxO, luxM, and aphA. We show that a representative Qrr, Qrr3, uses four distinct mechanisms to control its particular targets: the Qrr3 sRNA represses luxR through catalytic degradation, represses luxM through coupled degradation, represses luxO through sequestration, and activates aphA by revealing the ribosome binding site while the sRNA itself is degraded. Qrr3 forms different base-pairing interactions with each mRNA target, and the particular pairing strategy determines which regulatory mechanism occurs. Combined mathematical modeling and experiments show that the specific Qrr regulatory mechanism employed governs the potency, dynamics, and competition of target mRNA regulation, which in turn, defines the overall quorum-sensing response.

Compensation schemes for uneven illumination and LED light-emitting instability in optical camera communication system.

In order to increase the data rate of the optical camera communication (OCC) system, the 8-composite-amplitude-shift-keying modulation (8CASK) OCC system is used in this work. However, if the static decision thresholds are employed to demodulate multi-level ASK signal, uneven illumination of LED lamps and LED light-emitting instability lead to the fluctuation of the gray range in the picture and degrade the bit-error-rate (BER) performance. In this work, we propose and demonstrate a demodulation scheme, using the uneven illumination compensation algorithm, the pixel matrix threshold overall update algorithm and the secondary decision algorithm, to mitigate the impact of illumination unevenness and LED light-emitting instability. The BER performance is evaluated and compared with other demodulation schemes. The experimental results demonstrate that the communication rate of our proposed scheme can reach 9kbit/s at a distance of 250 cm where the illumination is 135lux, and the BER is 8.01 × 10-5.

Hydrothermal carbonisation of polyvinyl chloride in ethanol-water/water system for solid fuels: Dechlorination, characteristics analysis of hydrochar, and reaction path.

Polyvinyl chloride (PVC) waste plastic is a typical solid waste. In this paper, the dechlorination and carbonization behavior of PVC in ethanol-water/water system under different process parameters (temperature, residence time, solid-liquid ratio) was studied, and hydrothermal carbon was characterized by SEM, elemental analysis, TG-DTG, XPS, Py-GC/MS. The results show that temperature is the key to the hydrothermal dechlorination of PVC, and the dechlorination efficiency of PVC is the highest by parameter optimization (220°C-90 min-10% S/D-80% E/D), which can reach 96.33 %. With the removal of Cl, the surface of the PVC matrix changed from full and smooth flocculent to honeycomb with uniform pore size distribution. Thermogravimetric analysis shows that the combustion of hydrochar can be divided into three stages: HCl precipitation and volatile combustion, semi-coke and coke combustion, and fixed carbon combustion. The combustion parameters and kinetic parameters of hydrochar were measured, and it was found that the hydrothermal carbonization of PVC at higher temperatures and ethanol-water ratio could improve the combustion performance of hydrochar. The highest calorific value can reach 36.68 MJ/mol. Py-GC/MS analyzed the distribution of the pyrolysis products, and alkylbenzene and aliphatic were the main products of pyrolysis. The structural analysis of hydrochar showed that C-C and CC accounted for the largest proportion, accompanied by a small amount of C-O and CO and trace C-Cl. The possible reaction mechanism of the hydrothermal carbonization of PVC was analyzed based on the distribution of functional groups and compound composition. This work provides an effective and sustainable method for the recycling of refractory chlorinated plastics.

Preparation of functionalized porous chitin carbon to enhance the H2O2 production and Fe3+ reduction properties of Electro-Fenton cathodes for efficient degradation of RhB.

The performance of Electro-Fenton (EF) cathode materials is primarily assessed by H2O2 yield and Fe3+ reduction efficiency. This study explores the impact of pore structure in chitin-based porous carbon on EF cathode effectiveness. We fabricated mesoporous carbon (CPC-700-2) and microporous carbon (ZPC-700-3) using template and activation methods, retaining nitrogen from the precursors. CPC-700-2, with mesopores (3-5 nm), enhanced O2 diffusion and oxygen reduction, producing up to 778 mg/L of H2O2 in 90 min. ZPC-700-3, with a specific surface area of 1059.83 m2/g, facilitated electron transport and ion diffusion, achieving a Fe2+/Fe3+ conversion rate of 79.9%. EF systems employing CPC-700-2 or ZPC-700-3 as the cathode exhibited superior degradation performance, achieving 99% degradation of Rhodamine B, efficient degradation, and noticeable decolorization. This study provides a reference for the preparation of functionalized carbon cathode materials for efficient H2O2 production and effective Fe3+ reduction in EF systems.

Research progress in improving sludge dewaterability: sludge characteristics, chemical conditioning and influencing factors.

Sludge from wastewater treatment processes with high water content and large volume has become an inevitable issue in environmental management. Due to the challenging dewatering properties of sludge, current mechanical dewatering methods are no longer sufficient to meet the escalating water content standards of sludge. This paper summarizes the characteristics of various sludge and raises reasons for the their dewaterability differences. Affected by extracellular polymeric substances, biological sludge is hydrophilic and negatively charged, which limits the dewatering degree. The rheological properties, flocs, ionic composition, and solid phase concentration of the sludge also influence the dewatering to some extent. For these factors, the chemical conditioning measures with simple operation and excellent effect improve its dewaterability, which mainly include flocculation/coagulation, acid/alkali treatment, advanced oxidation, surfactant treatment and combined treatment. There is a growing necessity to explore the development of new chemical conditioning agents, even though traditional agents continue to remain widely used. However, the development of these new agents should prioritize finding a balance between various factors such as efficiency, effectiveness, ease of operation, environmental safety, and cost-effectiveness. Electrochemical dewatering enhances solid-liquid separation, and its coupling with chemical conditioning is also an excellent means to further reduce water content. In addition, the improvement of press filter is an effective way, which is influenced by pressure, processing time, sludge cake thickness and pore structure, filter media etc. In general, it is essential to develop new conditioning agents and enhance mechanical filtration press technology based on a thorough understanding of various sludge properties. Concurrently, an in-depth study of the principles of mechanical pressure filtration will contribute to establishing a theoretical foundation for effective deep sludge dewatering and propel further advancements in this field.

High-sensitivity non-cooled near-infrared detector based on lithium niobate surface acoustic wave resonators combined with MXene Ti3C2Tx quantum dot thin films.

In this study, we propose the design of a surface acoustic wave (SAW) near-infrared sensor combined with an MXene quantum dot thin film to improve the infrared absorption efficiency at near-infrared wavelengths. A YZ-cut lithium niobate (LiNbO3) SAW resonator is fabricated as an infrared sensing unit with a resonant frequency shift reflecting the change in infrared radiation. It was observed that the responsivity of the near-infrared sensor (with a base frequency of 460 MHz) increased by approximately 88.89%. Thus, the proposed device exhibits high-performance infrared detection. Owing to the passive wireless capability of the device, it has wide applications.

Lifetime visualization of femtosecond laser-induced plasma on GaP crystal.

Gallium phosphide (GaP) is a widely used and promising semiconductor material for photonics devices and we suppose the ultrafast laser can be a competitive tool for GaP processing. We used an 800 nm centered femtosecond (fs) laser with a pulse duration of 50 fs to irradiate the GaP crystal. The ablation threshold was first determined, and then the ultrafast dynamics including plasma expansion, shockwave formation and propagation, and spectral evolution were acquired and analyzed. The evolution of ejected plasma in the initial stage changed from cylindrical to planar propagation with the augment of laser fluence. The study on the propagation properties of shockwaves showed that the energy of propelling shockwaves accounted for 12% to 18% of the laser pulse energy at all fluences above the ablation threshold. A prominent plasma splitting was observed at a fluence slightly higher than the threshold, and a phenomenon that the plasma protruded out of the shockwaves was also found. Finally, the transient temperature and density of electron at different fluences were calculated. The temperature difference between the plasma and the shockwave proved the heating effect of the plasma during ablation.

Identifying determinants of bacterial fitness in a model of human gut microbial succession.

Human gut microbiota development has been associated with healthy growth but understanding the determinants of community assembly and composition is a formidable challenge. We cultured bacteria from serially collected fecal samples from a healthy infant; 34 sequenced strains containing 103,102 genes were divided into two consortia representing earlier and later stages in community assembly during the first six postnatal months. The two consortia were introduced alone (singly), or sequentially in different order, or simultaneously into young germ-free mice fed human infant formula. The pattern of fitness of bacterial strains observed across the different colonization conditions indicated that later-phase strains substantially outcompete earlier-phase strains, although four early-phase members persist. Persistence was not determined by order of introduction, suggesting that priority effects are not prominent in this model. To characterize succession in the context of the metabolic potential of consortium members, we performed in silico reconstructions of metabolic pathways involved in carbohydrate utilization and amino acid and B-vitamin biosynthesis, then quantified the fitness (abundance) of strains in serially collected fecal samples and their transcriptional responses to different histories of colonization. Applying feature-reduction methods disclosed a set of metabolic pathways whose presence and/or expression correlates with strain fitness and that enable early-stage colonizers to survive during introduction of later colonizers. The approach described can be used to test the magnitude of the contribution of identified metabolic pathways to fitness in different community contexts, study various ecological processes thought to govern community assembly, and facilitate development of microbiota-directed therapeutics.

An Anionic Porous Indium-Organic Framework with Nitrogen-Rich Linker for Efficient and Selective Removal of Trace Cationic Dyes.

Metal-organic frameworks (MOFs) with porosity and functional adjustability have great potential for the removal of organic dyes in the wastewater. Herein, an anionic porous metal-organic framework (MOFs) [Me2NH2]2In2[(TATAB)4(DMF)4]·(DMF)4(H2O)4 (HDU-1) was synthesized, which is constructed from a [In(OOC)4]- cluster and a nitrogen-rich linker H3TATAB (4,4',4″-s-triazine-1,3,5-triyltri-p-aminobenzoic acid). The negatively charged [In(OOC)4]- cluster and uncoordinated -COOH on the linker result in one unit cell of HDU-1 having 8 negative sites. The zeta potential of -20.8 mV dispersed in pure water also shows that HDU-1 possesses negatively charged surface potential. The high electronegativity, water stability, and porosity of HDU-1 can facilitate the ion-exchange and Coulombic interaction. As expected, the HDU-1 exhibits high selectivity and removal rates towards trace cationic dyes with suitable size, such as methylene blue (MB) (96%), Brilliant green (BG) (99.3%), and Victoria blue B (VB) (93.6%).

Study of MXene Ti3C2Tx quantum dot thin film on quartz bulk acoustic wave uncooled infrared sensors.

The infrared absorption efficiency is essential for an infrared sensor. We propose a quartz bulk acoustic wave (BAW) uncooled infrared sensor coated with MXene quantum dot film. The infrared detection is realized by measuring the resonant frequency of a Y-cut quartz BAW sensitive unit. An infrared sensor is fabricated by MEMS process, then the MXene quantum dot film is coated through the spin coating technology. The mechanism of infrared absorption enhancement is analyzed. Test results show that after coating the film, the responsivity (R) of the sensor increased by nearly 41% at a wavelength of 830nm, from 10.88MHz/W to 15.28 MHz/W. The quartz BAW infrared sensor combined with MXene quantum dots film has the potential of high-performance infrared detection.

Theoretical and Experimental Study on Nonlinear Failure of an MEMS Accelerometer under Dual Frequency Acoustic Interference.

In order to quantitatively study the interfered output of the accelerometer under an acoustic injection attack, a mathematical model for fitting and predicting the accelerometer output was proposed. With ADXL103 as an example, an acoustic injection attack experiment with amplitude sweeping and frequency sweeping was performed. In the mathematical model, the R-squared coefficient was R2 = 0.9990 in the acoustic injection attack experiment with amplitude sweeping, and R2 = 0.9888 with frequency sweeping. Based on the mathematical model, the dual frequency acoustic injection attack mode was proposed. The difference frequency signal caused by the nonlinear effect was not filtered by the low-pass filter. At a 115 dB sound pressure level, the maximum acceleration bias of the output was 4.4 m/s2 and the maximum amplitude of fluctuation was 4.97 m/s2. Two kinds of methods of prevention against acoustic injection attack were proposed, including changing the damping ratio of the accelerometer and adding a preposition low-pass filter.

A Filtering Algorithm of MEMS Gyroscope to Resist Acoustic Interference.

To reduce the impact of acoustic interference in a microelectromechanical system (MEMS) gyroscope and to improve the reliability of output data, a filtering algorithm based on orthogonal demodulation is proposed. According to the working principle and failure mechanism of a MEMS gyroscope, the sound and angular velocity frequencies are not identical, which lead to a different frequency signal output of the original single-channel demodulation scheme. Therefore, a Q channel demodulation filtering process was added to the origin single-channel demodulation scheme. For the Q channel demodulated signal, a Hilbert transform was used to compensate for the 90 degree phase shift. The IQ dual-channel difference can remove the acoustic interference signal. The simulation results indicate that the scheme can effectively suppress the acoustic interference signal and it can eliminate more than 95% of the impact of sound waves. We assembled the acoustic interference experimental platform, collected the driving and sensing data, and verified the denoising performance with our algorithm, which eliminated more than 70% of the noise signal. The simulation and experimental results demonstrate that the scheme can eliminate acoustic interference signal without destroying angular velocity signal.

Hybrid indoor localization scheme with image sensor-based visible light positioning and pedestrian dead reckoning.

In this paper, we propose a hybrid indoor localization scheme with image sensor-based visible light positioning and pedestrian dead reckoning. The architecture and algorithm of the proposed positioning scheme are analyzed. We build and demonstrate two different positioning prototypes with single/multiple cells, which are based on a commercial light-emitting diode lamp and off-the-shelf mobile phone equipped with an image sensor and inertial measurement unit. Experimental results show that the proposed visible light positioning scheme can achieve both cell recognition and three-dimensional positioning with a single captured image of a single light source, and the positioning error is only several centimeters. Moreover, with the proposed hybrid positioning algorithm consisting of visible light positioning and pedestrian dead reckoning, we achieved real-time decimeter-level indoor location tracking continuously and robustly with sparse light-source beacons in an actual indoor scenario.

Accurate and Robust Monocular SLAM with Omnidirectional Cameras.

Simultaneous localization and mapping (SLAM) are fundamental elements for many emerging technologies, such as autonomous driving and augmented reality. For this paper, to get more information, we developed an improved monocular visual SLAM system by using omnidirectional cameras. Our method extends the ORB-SLAM framework with the enhanced unified camera model as a projection function, which can be applied to catadioptric systems and wide-angle fisheye cameras with 195 degrees field-of-view. The proposed system can use the full area of the images even with strong distortion. For omnidirectional cameras, a map initialization method is proposed. We analytically derive the Jacobian matrices of the reprojection errors with respect to the camera pose and 3D position of points. The proposed SLAM has been extensively tested in real-world datasets. The results show positioning error is less than 0.1% in a small indoor environment and is less than 1.5% in a large environment. The results demonstrate that our method is real-time, and increases its accuracy and robustness over the normal systems based on the pinhole model. We open source in https://github.com/lsyads/fisheye-ORB-SLAM.

High-Precision Indoor Visible Light Positioning Using Modified Momentum Back Propagation Neural Network with Sparse Training Point.

In this letter, we propose an indoor visible light positioning technique using a Modified Momentum Back-Propagation (MMBP) algorithm based on received signal strength (RSS) with sparse training data set. Unlike other neural network algorithms that require a large number of training data points to locate accurately, we have realized high-precision positioning for 100 test points with only 20 training points in a 1.8 m × 1.8 m × 2.1 m localization area. In order to verify the adaptability of the MMBP algorithm, we experimentally demonstrate two different training data acquisition methods adopting either even or arbitrary training sets. In addition, we also demonstrate the positioning accuracy of the traditional RSS algorithm. Experimental results show that the average localization accuracy optimized by our proposed algorithm is only 1.88 cm for the arbitrary set and 1.99 cm for the even set, while the average positioning error of the traditional RSS algorithm reaches 14.34 cm. Comparison indicates that the positioning accuracy of our proposed algorithm is 7.6 times higher. Results also show that the performance of our system is higher than some previous reports based on RSS and RSS fingerprint databases using complex machine learning algorithms trained by a large amount of training points.

Spatial distribution and sources of heavy metals in natural pasture soil around copper-molybdenum mine in Northeast China.

The characterization of the content and source of heavy metals are essential to assess the potential threat of metals to human health. The present study collected 140 topsoil samples around a Cu-Mo mine (Wunugetushan, China) and investigated the concentrations and spatial distribution pattern of Cr, Ni, Zn, Cu, Mo and Cd in soil using multivariate and geostatistical analytical methods. Results indicated that the average concentrations of six heavy metals, especially Cu and Mo, were obviously higher than the local background values. Correlation analysis and principal component analysis divided these metals into three groups, including Cr and Ni, Cu and Mo, Zn and Cd. Meanwhile, the spatial distribution maps of heavy metals indicated that Cr and Ni in soil were no notable anthropogenic inputs and mainly controlled by natural factors because their spatial maps exhibited non-point source contamination. The concentrations of Cu and Mo gradually decreased with distance away from the mine area, suggesting that human mining activities may be crucial in the spreading of contaminants. Soil contamination of Zn were associated with livestock manure produced from grazing. In addition, the environmental risk of heavy metal pollution was assessed by geo-accumulation index. All the results revealed that the spatial distribution of heavy metals in soil were in agreement with the local human activities. Investigating and identifying the origin of heavy metals in pasture soil will lay the foundation for taking effective measures to preserve soil from the long-term accumulation of heavy metals.

Functional determinants of the quorum-sensing non-coding RNAs and their roles in target regulation.

Quorum sensing is a chemical communication process that bacteria use to control collective behaviours including bioluminescence, biofilm formation, and virulence factor production. In Vibrio harveyi, five homologous small RNAs (sRNAs) called Qrr1-5, control quorum-sensing transitions. Here, we identify 16 new targets of the Qrr sRNAs. Mutagenesis reveals that particular sequence differences among the Qrr sRNAs determine their target specificities. Modelling coupled with biochemical and genetic analyses show that all five of the Qrr sRNAs possess four stem-loops: the first stem-loop is crucial for base pairing with a subset of targets. This stem-loop also protects the Qrr sRNAs from RNase E-mediated degradation. The second stem-loop contains conserved sequences required for base pairing with the majority of the target mRNAs. The third stem-loop plays an accessory role in base pairing and stability. The fourth stem-loop functions as a rho-independent terminator. In the quorum-sensing regulon, Qrr sRNAs-controlled genes are the most rapid to respond to quorum-sensing autoinducers. The Qrr sRNAs are conserved throughout vibrios, thus insights from this work could apply generally to Vibrio quorum sensing.

Fusion Based on Visible Light Positioning and Inertial Navigation Using Extended Kalman Filters.

With the rapid development of smart technology, the need for location-based services (LBS) increases every day. Since classical positioning technology such as GPS cannot satisfy the needs of indoor positioning, new indoor positioning technologies, such as Bluetooth, Wi-Fi, and Visible light communication (VLC), have already cut a figure. VLC positioning has been proposed because it has higher accuracy, costs less, and is easier to accomplish in comparison to the other indoor positioning technologies. However, the practicality of VLC positioning is limited since it is easily affected by multipath effects and the layout of LEDs. Thus, we propose a fusion positioning system based on extended Kalman filters, which can fuse the VLC position and the inertial navigation data. The accuracy of the fusion positioning system is in centimeters, which is better compared to the VLC-based positioning or inertial navigation alone. Furthermore, the fusion positioning system has high accuracy, saves energy, costs little, and is easy to install, making it a promising candidate for future indoor positioning applications.

[Determination of 41 pesticides in vegetables and fruits by GPC-GC-MS/MS].

OBJECTIVE: A method for the determination of 41 pesticides including 26 organophosphorus pesticides, 6 kinds of carbamate, 7 pryethoids insecticides, 1 kinds of organochlorine and fungicide in vegetables and fruits, was established based on optimized QuEChERS with on line gel permeation chromatography-gas chromatography-mass spectrometry (GPC-GC-MS/MS). METHODS: The method obtained the optimized conditions by comparing different methods of extraction and purification. The analytes were extracted from the samples using acetonitrile-buffer of acetic acid and sodium acetate. Then the extracts were determined by GC-MS/MS in multireaction monitoring (MRM) mode after being cleaned up with mixed solid-phase dispersion. And the external standard method was applied to quantify. RESULTS: All the 41 pesticides had good linearity in the ranges of 2-200 ng/mL with the correlation coefficients higher than 0.995. The average recoveries of the most of 41 pesticides in celery and apple were in the range of 71.0%-125.4% at the spiked levels of 5, 10 and 50 µg/kg,with relative standard deviations (RSDs) of 0.34%-15.0%. The limits of quantification (LOQs) of the method at the spiked levels of 5 µg/kg were 0.107-10.100 µg/kg. CONCLUSION: The method is simple, rapid, sensitive and specific.

Identification of avaC from Human Gut Microbial Isolates that Converts 5AVA to 2-Piperidone.

2-piperidone is a crucial industrial raw material of high-value nylon-5 and nylon-6,5. Currently, a major bottleneck in the biosynthesis of 2-piperidone is the identification of highly efficient 2-piperidone synthases. In this study, we aimed to identify specific strains among 51 human gut bacterial strains capable of producing 2-piperidone and to elucidate its synthetic mechanism. Our findings revealed that four gut bacterial strains, namely Collinsella aerofaciens LFYP39, Collinsella intestinalis LFYP54, Clostridium bolteae LFYP116, and Clostridium hathewayi LFYP18, could produce 2-piperidone from 5-aminovaleric acid (5AVA). Additionally, we observed that 2-piperidone could be synthesized from proline through cross-feeding between Clostridium difficile LFYP43 and one of the four 2-piperidone producing strains, respectively. To identify the enzyme responsible for catalyzing the conversion of 5AVA to 2-piperidone, we utilized a gain-of-function library and identified avaC (5-aminovaleric acid cyclase) in C. intestinalis LFYP54. Moreover, homologous genes of avaC were validated in the other three bacterial strains. Notably, avaC were found to be widely distributed among environmental bacteria. Overall, our research delineated the gut bacterial strains and genes involved in 2-piperidone production, holding promise for enhancing the efficiency of industrial biosynthesis of this compound.