Thioalkynes in Ring Forming Reactions.

Organic cycles play an important role in chemistry, pharmacology and material science for their unique properties. Construction of organic cycles from thioalkynes attracted increasing attention due to the facile access of thioalkynes. 2H-Azirines were synthesized successfully from thioalkynyl oxime ethers. Cyclobutanes were formed through chiral titanium catalyzed cycloaddition of thioalkynes. Cyclopentenes were afforded by annulation of thioalkynes. Thioalkynes could be also applied to synthesize thiophenes, oxazoles, benzo[b]thiophenes, 2H-chromenes, 2-phenylbenzothiazoles, diazacyclobutene, etc. In this review, construction of organic cycles from thioalkynes were highlighted. Firstly, the property and application of organic cyclic compounds were simply introduced. After presenting the general methods to access organic cycles, applications of thioalkynes as synthons to prepare organic cycles were classified and presented in detail. Based on different kinds of organic cycles obtained from thioalkynes, organic reactions for synthesis of three-, four-, five-, six-membered as well as fused cycles would be summarized and the plausible reaction mechanisms could be presented if available.

Association analysis of PMEL gene expression and single nucleotide polymorphism with plumage color in quail.

To explore the relationship between PMEL gene and quail plumage color, to provide a reference for subsequent quail plumage color breeding. In this experiment, RT-qPCR technology was used to analyze the relative mRNA expression levels of Korean quail (maroon) and Beijing white quail embryos at different developmental stages. Two SNPs in PMEL gene were screened based on the RNA-Seq data of skin tissues of Korean quail and Beijing white quail during embryonic stage. The KASP technology was used for genotyping in the resource population and correlation analysis was carried out with the plumage color traits of quail. Finally, the bioinformatics technology was used to predict the effects of these two SNPs on the structure and function of the encoded protein. The results showed that the expression levels of PMEL gene during the embryonic development of Beijing white quail were extremely significantly higher than that of Korean quail (p < 0.01). The frequency distribution of the three genotypes (AA, AB, and BB) of the Beijing white quail at the c. 1030C > T and c. 1374A > G mutation sites were extremely significantly different from that of the Korean quail (p < 0.01). And there was a significant correlation between the c. 1374A > G mutation site with white plumage phenotype. Bioinformatics analysis showed that SNP1 (c. c1030t) located in exon 6 was a harmful mutation site, and SNP2 (c. a1374g) located in exon 7 was a neutral mutation site. Protein conservation prediction showed that the coding protein P344S site caused by SNP1 (c. c1030t) site and the coding protein I458M site caused by SNP2 (c. g2129a) site were non-conservative sites. The results of this experiment showed that the PMEL gene was associated with the plumage color traits of quail and could be used as a candidate gene for studying the plumage color of quail.

A High-Performance Portable Transient Electro-Magnetic Sensor for Unexploded Ordnance Detection.

Portable transient electromagnetic (TEM) systems can be well adapted to various terrains, including mountainous, woodland, and other complex terrains. They are widely used for the detection of unexploded ordnance (UXO). As the core component of the portable TEM system, the sensor is constructed with a transmitting coil and a receiving coil. Based on the primary field of the transmitting coil and internal noise of the receiving coil, the design and testing of such a sensor is described in detail. Results indicate that the primary field of the transmitting coil depends on the diameter, mass, and power of the coil. A higher mass-power product and a larger diameter causes a stronger primary field. Reducing the number of turns and increasing the clamp voltage reduces the switch-off time of the transmitting current effectively. Increasing the cross-section of the wire reduces the power consumption, but greatly increases the coil's weight. The study of the receiving coil shows that the internal noise of the sensor is dominated by the thermal noise of the damping resistor. Reducing the bandwidth of the system and increasing the size of the coil reduces the internal noise effectively. The cross-sectional area and the distance between the sections of the coil have little effect on the internal noise. A less damped state can effectively reduce signal distortion. Finally, a portable TEM sensor with both a transmitting coil (constructed with a diameter, number of turns, and transmitting current of 0.5 m, 30, and 5 A, respectively) and a receiving coil (constructed with a length and resonant frequency of 5.6 cm and 50 kHz, respectively) was built. The agreement between experimental and calculated results confirms the theory used in the sensor design. The responses of an 82 mm mortar shell at different distances were measured and inverted by the differential evolution (DE) algorithm to verify system performance. Results show that the sensor designed in this study can not only detect the 82 mm mortar shell within 1.2 m effectively but also locate the target precisely.

An Improved High-Sensitivity Airborne Transient Electromagnetic Sensor for Deep Penetration.

The investigation depth of transient electromagnetic sensors can be effectively increased by reducing the system noise, which is mainly composed of sensor internal noise, electromagnetic interference (EMI), and environmental noise, etc. A high-sensitivity airborne transient electromagnetic (AEM) sensor with low sensor internal noise and good shielding effectiveness is of great importance for deep penetration. In this article, the design and optimization of such an AEM sensor is described in detail. To reduce sensor internal noise, a noise model with both a damping resistor and a preamplifier is established and analyzed. The results indicate that a sensor with a large diameter, low resonant frequency, and low sampling rate will have lower sensor internal noise. To improve the electromagnetic compatibility of the sensor, an electromagnetic shielding model for a central-tapped coil is established and discussed in detail. Previous studies have shown that unclosed shields with multiple layers and center grounding can effectively suppress EMI and eddy currents. According to these studies, an improved differential AEM sensor is constructed with a diameter, resultant effective area, resonant frequency, and normalized equivalent input noise of 1.1 m, 114 m², 35.6 kHz, and 13.3 nV/m², respectively. The accuracy of the noise model and the shielding effectiveness of the sensor have been verified experimentally. The results show a good agreement between calculated and measured results for the sensor internal noise. Additionally, over 20 dB shielding effectiveness is achieved in a complex electromagnetic environment. All of these results show a great improvement in sensor internal noise and shielding effectiveness.

Overhauser Geomagnetic Sensor Based on the Dynamic Nuclear Polarization Effect for Magnetic Prospecting.

Based on the dynamic nuclear polarization (DNP) effect, an alternative design of an Overhauser geomagnetic sensor is presented that enhances the proton polarization and increases the amplitude of the free induction decay (FID) signal. The short-pulse method is adopted to rotate the enhanced proton magnetization into the plane of precession to create an FID signal. To reduce the negative effect of the powerful electromagnetic interference, the design of the anti-interference of the pick-up coil is studied. Furthermore, the radio frequency polarization method based on the capacitive-loaded coaxial cavity is proposed to improve the quality factor of the resonant circuit. In addition, a special test instrument is designed that enables the simultaneous testing of the classical proton precession and the Overhauser sensor. Overall, comparison experiments with and without the free radical of the Overhauser sensors show that the DNP effect does effectively improve the amplitude and quality of the FID signal, and the magnetic sensitivity, resolution and range reach to 10 pT/Hz 1 / 2 @1 Hz, 0.0023 nT and 20-100 µ T, respectively.

Struvite pellet crystallization in a high-strength nitrogen and phosphorus stream.

Struvite crystallization is a reliable method to recover nutrients from wastewater. Laboratory-scale experiments were conducted to investigate nutrient recovery from synthetic wastewater with high-strength orthophosphate and ammonia-nitrogen by the formation of struvite pellets. Without adjusting pH, struvite crystal growth environment was achieved in ammonia-nitrogen and orthophosphate concentration ranges of 100-1,000 and 221-2,214 mg/L, respectively. The mean size of the harvested struvite pellets was in the range of 3-4 mm. pH is an important factor indicating the process supersaturation. A range of pH 6.2-9.0 was tested in order to enhance nutrient removal efficiency. The results showed although higher N, P and Mg removals were achieved at higher pH values, over 95% N, P and Mg removals were still achieved at pH of 7.6. Recycling ratio of the clarifier supernatant to influent had no significant promotion of N or P removal.

Effects of different protein and lipid levels on the growth performance and intestinal microflora of loach (Paramisgurnus dabryanus).

The aim of this study was to examine the effects of dietary protein and lipid levels on the growth performance and homeostasis of the intestinal flora in Paramisgurnus dabryanus. An 8-wk 3 × 3 two-factorial experiment was conducted to investigate the interaction between dietary crude protein (CP: 30%, 35%, 40%) and ether extract (EE: 6%, 10%, 14%) on the growth rate and the intestinal microflora of P. dabryanus. A total of 2,160 fish (5.19 ± 0.01 g) were randomly allotted to 36 aquariums each with 60 fish. Fish were fed the experimental diet twice daily. Results revealed that weight gain rate (WGR), specific growth rate (SGR), protein efficiency ratio and net protein utilization significantly increased when increasing protein levels from 30% to 40% (P < 0.05). Both WGR and SGR enhanced first but reduced thereafter with maximum value at 10% lipid level as dietary lipid increased from 6% to 14% (P < 0.05). Significant interactions between protein and lipid were found with feed conversion rate, lipid efficiency ratio and net lipid utilization (P < 0.05). At the phylum level, Proteobacteria and Actinobacteria were the dominant bacteria; at the genus level, Burkholderia-Caballeronia-Paraburkholderia was the dominant bacteria. Fish fed the diet containing 10% lipid had a higher abundance of Proteobacteria and unclassified_f_Eenterobacteriaceae than those fed the 14% lipid diet, and a higher abundance of Rhodobacter than those fed the 6% lipid diet (P < 0.05). Analysis of the predicted functions showed that metabolism in the intestine of fish in the CP40EE10 group was more active than that in CP30EE14 group. Polynomial regression analysis found that a diet containing 40.87% protein and 9.88% lipid can be considered optimal for P. dabryanus.

Association analysis of melanophilin (MLPH) gene expression and polymorphism with plumage color in quail.

We explore the relationship between the melanophilin (MLPH) gene and quail plumage color and provide a reference for subsequent quail plumage color breeding. In this experiment, real-time quantitative PCR (RT-qPCR) technology was used to analyze the relative mRNA expression levels of Korean quail (maroon) and Beijing white quail embryos at different developmental stages. Two single-nucleotide polymorphisms (SNPs) in the MLPH gene were screened based on the RNA-sequencing (RNA-Seq) data of skin tissues of Korean quail and Beijing white quail during the embryonic stage. Kompetitive allele-specific PCR (KASP) technology was used for genotyping in the resource population, and correlation analysis was carried out with the plumage color traits of quail. Finally, bioinformatics was used to predict the effects of these two SNPs on the structure and function of the encoded protein. The results showed that the expression level of the MLPH gene during embryonic development of Beijing white quail was significantly higher than that of Korean quail ( P < 0.01 ). The frequency distribution of the three genotypes (CC, CA and AA) of the Beijing white quail at the c.1807C  >  A mutation site was significantly different from that of the Korean quail ( P < 0.01 ). The frequency distribution of the three genotypes (GG, GA and AA) of the Beijing white quail at the c.2129G  >  A mutation site was significantly different from that of the Korean quail ( P < 0.01 ). And there was a significant correlation between the c.1807C  >  A mutation site and the white plumage phenotype. Bioinformatics showed that SNP1 (c.1807C  >  A) was a neutral mutation and that SNP2 (c.2129G  >  A) was a deleterious mutation. The prediction of protein conservation showed that the mutation sites of coding proteins R603S and G710D caused by SNP1 (c.1807C  >  A) and SNP2 (c.2129G  >  A) were highly conserved.

A fast tracking method for magnetic abnormalities using distributed Overhauser magnetometer system based on genetic algorithm.

Magnetic anomaly detection technologies have been widely used for tracking moving targets. In this paper, we present a fast-tracking method for magnetic abnormalities using a distributed Overhauser magnetometer system based on the genetic algorithm. Our proposed framework of the Overhauser magnetometer system employs multiple sensors to eliminate background interference, and the genetic algorithm efficiently solves magnetic anomaly data without requiring the derivation of the objective function. Test platforms were built to evaluate the distributed Overhauser magnetometer system and the genetic algorithm. Results from the natural outdoor magnetism laboratories showed that the noise of our presented magnetometers was below 0.134 nT. The optimal factors for solution precision and effectiveness in the genetic algorithm were obtained from the simulation. Moreover, the outdoor tracking experiments indicated that the proposed method could accurately and quickly detect the moving ferromagnetic object within 6.9% maximum positioning error in 0.55 m, and the tracking precision of the object velocity can get 5.88% maximum error in 4.33 km/h.

An optimized free induction decay signal sensing coil and its matching circuit for miniaturized Overhauser geomagnetic sensor.

An Overhauser geomagnetic sensor is a precise instrument commonly employed for geomagnetic field observation, magnetic surveys, and so on. Currently, the miniaturization of the Overhauser geomagnetic sensor is limited due to the lower signal-to-noise ratio. Thus, how to effectively extract weaker free induction decay (FID) signal from a miniaturized sensor and how to improve the signal quality have become the bottleneck. To address these problems, we came up with an optimal design of the FID signal sensing coil for a miniaturized Overhauser geomagnetic sensor and propose a front-end matching circuit for the sensing coil to inhibit the attenuation of the signal amplitude caused by high impedance, further reducing the overall noise floor of the signal acquisition system. Finally, the field experimental results show that the miniaturized prototype sensor has a smaller volume and mass with an approximate performance compared with the commercial sensor.

Compressed sensing based tuning algorithm for the sensor of proton precession magnetometers.

In this Note, a new compressed sensing-based tuning algorithm has been developed to boost the sensor tuning performance of the proton precession magnetometers (PPMs). An end-to-end framework for the PPM's sensing free induction decay (FID) signal resonance based on orthogonal matching pursuit compressed sensing (OMPCS), dubbed OMPCS-FID resonance (OMPCS-FIDR), is developed and its working principle and implemented strategy are elaborated. By comparing the new sensor tuning approach with the state-of-the-art algorithms, i.e., peak detection, auto-correction, and secondary tuning, the results demonstrate that the proposed tuning method not only retains the performance but also overcomes the drawbacks of the state-of-the-art methods, which accelerates the possibilities of the PPM working in a scenario with a strong gradient magnetic field.

Efficient noise reduction for the free induction decay signal from a proton precession magnetometer with time-frequency peak filtering.

The proton precession magnetometer (PPM) is a commonly used device to measure the varying magnetic field. Since the frequency of the PPM sensing free induction decay (FID) signal is proportional to the magnetic field, the signal-to-noise ratio (SNR) is always a critical issue that influences the measurement accuracy severely due to the external interferences such as harmonic noise and random noise. In this study, to boost the SNR of the FID signal, an effective filtering algorithm based on time-frequency peak filtering (TFPF) analyzed with pseudo-Wigner-Ville distribution (PWVD) is proposed. Through pre-treating the collected noisy FID signal with frequency modulation and instantaneous frequency estimation using the peak value of the time-frequency characterization, the embedded noise can be decorrelated and the relative pure FID signal can be detected regardless of the impact of varying noise levels. The superiority of the proposed synaptic noise reduction framework, namely, TFPF-PWVD, was found by comparing it with state-of-the-art approaches under the same conditions. The results illustrated that even though in a strong-noisy scenario, the proposed TFPF-PWVD based approach still achieved the best SNR for the yielded sensing FID and the minimum standard deviation for the observed magnetic field data, which can enhance the geomagnetic measuring performance of a PPM.

A fusion of principal component analysis and singular value decomposition based multivariate denoising algorithm for free induction decay transversal data.

The free induction decay (FID) transversal data determines the measurement accuracy of time-dependent geomagnetic fields, whereas the conservation of clean components and removal of noise cannot be easily achieved for this kind of data. Even though numerous techniques have been proven to be effective in improving the signal-to-noise ratio by filtering out frequency bands, how to efficiently reduce noise is still a crucial issue due to several restrictions, e.g., prior information requirement, stationary data assumption. To end this, a new multivariate algorithm based on the fusion of principal component analysis (PCA) and singular value decomposition (SVD), namely, principal component analysis and decomposition (PCAD), was presented. This novel algorithm aims to reduce noise as well as cancel the interference of FID transversal data. Specifically, the PCAD algorithm is able to obtain the dominant principal components of the FID and that of the noise floor by PCA, in which an optimal number of subspaces could be retained via a cumulative percent of variance criterion. Furthermore, the PCA was combined with an SVD filter whose singular values corresponding to the interferences were identified, and then the noise was suppressed by nulling the corresponding singular values, which was able to achieve an optimum trade-off between the preservation of pure FID data and the denoising efficiency. Our proposed PCAD algorithm was compared with the widely used filter methods via extensive experiments on synthetic and real FID transversal data under different noise levels. The results demonstrated that this method can preserve the FID transversal data better and shows a significant improvement in noise suppression.

Suppression of the negative effect of abnormal data based on the Hough transform and application to the magnetic compensation of airborne optically-pumped magnetometer data.

A magnetic sensor of the optically pumped magnetometer may enter a dead zone during an aeromagnetic survey, resulting in unavoidable abnormal data and seriously affecting the effect of aeromagnetic compensation. We propose a fast discrimination and culling method based on the Hough transform to prevent abnormal data from participating in the coefficient estimation. In the proposed method, the parameter space is partitioned into small buckets and the most frequently passed region of sinusoidal curves is detected to eliminate abnormal data. Although the conventional method performs similarly to the proposed method when there is only 1% abnormal data, it is theoretically shown that the proposed method has a better goodness of fit of 0.9518, compared with a value of 0.1956 for the conventional method, in the presence of 45% abnormal data. Furthermore, we construct an experimental platform and conduct a flight test in which the proposed method has an improvement ratio of 4.11 compared with a value of 0.34 for the conventional method.

Apparatus and method for efficient sampling of critical parameters demonstrated by monitoring an Overhauser geomagnetic sensor.

The polarization frequency of free radical solution in Overhauser geomagnetic sensor determines the quality of the Larmor precession signal generated by the sensor. To obtain the polarization frequency accurately, a test apparatus was designed in this paper, which can overcome existing problems in the presently used apparatuses, such as lower resolution, complex operation, etc. The proposed apparatus adopts a high-resolution direct digital synthesis as the controllable radio frequency (RF) signal source. Meanwhile, an analog-to-digital converter synchronization acquisition technology combined with a normalization approach is proposed, which effectively solves the problem of the uneven amplitude-frequency characteristic in the range of 50 MHz-100 MHz. Moreover, the apparatus is integrated by adopting the RF power and applying the weak signal amplifier as an auxiliary measurement channel. The equivalent circuit of the sensors resonant cavity was simulated, and the efficiency curve of the adjustable capacitors to the resonant frequency and the quality factor were obtained. The simulated results were further verified by testing the resonance cavity characteristics of a commercial Overhauser geomagnetic sensor under different conditions. Furthermore, the relationship between the polarization degree of the free radical solution and RF excitation power and time were also obtained. The testing methods and results were given, and the experimental data were analyzed. Finally, the experimental results demonstrate that the proposed apparatus can measure the polarization frequency of the free radical solution, the bandwidth, and the quality factor, accurately. Furthermore, it can be used for the determination of the polarization power and time during the design process for an Overhauser magnetometer.

A high-precision and fast-sampling frequency measurement method based on FPGA carry chain for airborne optically pumped cesium magnetometer.

Improving the precision and sampling rate of the resonance frequency of cesium atoms is the key to enhancing the same factors of an airborne optically pumped cesium magnetometer (AOPCM). Aiming at the existed problems of AOPCM and characteristics of resonance signal, this paper proposes a high-precision and fast-sampling frequency measurement method based on carry chains of Field-Programmable Gate Array (FPGA). In order to achieve a fast-sampling rate, an improved equal precision frequency measurement method is proposed to measure the standard signal and the resonance signal continuously. Besides, by using the serial full adder to connect FPGA carry chains to a delay line, the delay line is used to compensate the unsynchronized clock edge, so the counting error can be reduced, and the precision of frequency measurement can be improved greatly. Experiments show that the frequency resolution is 0.014 nT and the relative error is lower than 2 × 10-6 when the sampling rate is 500 Hz. The experimental result indicates that the proposed method improves the precision and sampling rate of resonance frequency measurement greatly. Consequently, the precision and sampling rate of AOPCM can be improved.

Evaluation of chemical indicators for tracking and apportionment of phosphorus sources to Table Rock Lake in Southwest Missouri, USA.

This work evaluated the suitability of selected chemical species as indicators for tracking and apportionment of point and non-point phosphorus sources within the Table Rock Lake watershed in Southwest Missouri, USA. The species were evaluated with respect to their uniqueness to specific source types, their ability to be detected in both sources and receiving waters, and the consistency of their concentration ratios to phosphorus. Four sampling events were conducted at 15 sample locations in one year to collect water samples for measuring the concentrations of total and dissolved phosphorus, seven anions, and 19 major and trace elements. Current analytical methods were sensitive enough for quantification of most of the chemical species in both sources and the receiving waterbody. Due to the high seasonal variation of phosphorus concentrations in source samples, no chemical species had consistent concentration ratios to phosphorus across source types. However, several chemicals were found to be unique to specific sources; bromide ion can be used as a unique indicator for the effluent of the largest wastewater treatment plant in the watershed.

[Degradation of nicosulfuron by combination effects of microorganisms and chemical hydrolysis].

A strain which was capable of degrading nicosulfuron in the presence of glucose was isolated from nicosulfuron contaminated wetland soil, and it was identified as Klebsiella sp. based on 16S rDNA gene sequencing analysis. The strain could grow using nicosulfuron as the sole nitrogen source. The optimal temperature was 35 degrees C and the initial pH was neutral to weak acid. Hydrolysis experiments indicated that nicosulfuron remained stably under neutral and alkaline conditions, while in acidic conditions, it hydrolyzed quickly. Based on biodegradation experiments, when the concentration of glucose in culture was 5 g x L(-1), the strain could degrade 99.4% of nicosulfuron after incubation for 10 days at 35 degrees C, initial pH = 7; pH of the solution decreased from initial 7.0 to 4.0 in the meantime. When the concentration of glucose in culture solution was decreased to 500 mg x L(-1) and 100 mg x L(-1), with other conditions unchanged, only 11.7% and 6.6% of nicosulfuron were degraded, respectively, and pH of the solution remained at around 7.0. It was proposed that the degradation of nicosulfuron was caused by hydrolysis under acidic conditions at low pH which was resulted from the biodegradation of glucose by the strain. Therefore, the removal of nicosulfuron was actually caused by combined effects of microorganisms and chemical hydrolysis.

A facile one-pot method for synthesis of low-cost iron oxide/activated carbon nanotube electrode materials for lithium-ion batteries.

We designed a facile one-pot method to synthesize iron oxide/activated carbon nanotubes (IO/ACNTs) using as-prepared carbon nanotubes (APCNTs) modified by alkali solid-activation. The open-ended CNTs and iron oxide loading could be realized in one step. The resulting IO/ACNT hybrids, as an anode material for lithium-ion batteries (LIBs), exhibited high reversible lithium storage capacity and excellent rate capability, which make APCNTs potentially useful for large-scale applications in LIBs.