In the past several years, applications of transition metal complexes in tuning the reactivity of organocatalyst‐promoted transformations have attracted increasing attention in the synthetic ...community. Efforts in this direction have led to the discovery of unprecedented reactivities, which are not accessible through the use of either of these two catalytic systems separately. The concept continues to develop and offers huge potential. This microreview describes and summarizes recent progress in this field, focusing on discussion of the enhancement and diversification of reactivity patterns in organocatalysis through the deployment of transition metal complexes.
The fast development of organocatalysis has significantly enriched the field oforganic synthesis. Recent success in combining transition metal complexes withorganocatalysis has led to the emergence of a promising new direction with potential discoveries of new reactivity patterns and novel synthetic strategies.
This paper proposes a novel approach to health monitoring and multifault detection in permanent magnet synchronous machines using direct flux measurement with search coils. Unlike other ...spectrum-based fault detection schemes, only the fundamental frequency component of the measured voltage is utilized for fault detection. Therefore, the performance of the proposed scheme is not affected by nonstationary speed or harmonics introduced by the power supply. In addition, location of interturn short circuits and direction of static eccentricity can be detected, which have never been done by any other scheme. In spite of the invasive nature of the technique, it is very suitable for mission-critical applications and emerging applications such as off-shore wind turbines, hybrid vehicle technology, and military applications, where early detection of faults is of paramount importance. 2-D simulations using finite element analysis have been presented to validate the proposed method under different operating conditions. Experimental introduction of stator interturn short circuit, demagnetization, and static eccentricity has been discussed, and the proposed scheme is experimentally implemented to examine its effectiveness.
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•Adsorption of different emerging pharmaceuticals on MWCNTs was studied.•Pharmaceuticals adsorption was rapid and increased with the MWCNTs surface area.•Adsorption isotherms, ...kinetics and affinity were comprehensively investigated.•Electrostatic interaction, polarity, and substituent effects were discussed.•Adsorption was affected by environmental conditions, such as pH and ionic strength.
The adsorption behavior of different emerging contaminants (3 chloramphenicols, 7 sulfonamides, and 3 non-antibiotic pharmaceuticals) on five types of multi-walled carbon nanotubes (MWCNTs), and the underlying factors were studied. Adsorption equilibriums were reached within 12h for all compounds, and well fitted by the Freundlich isotherm model. The adsorption affinity of pharmaceuticals was positively related to the specific surface area of MWCNTs. The solution pH was an important parameter of pharmaceutical adsorption on MWCNTs, due to its impacts on the chemical speciation of pharmaceuticals and the surface electrical property of MWCNTs. The adsorption of ionizable pharmaceuticals decreased in varying degrees with the increased ionic strength. MWCNT-10 was found to be the strongest adsorbent in this study, and the Freundlich constant (KF) values were 353–2814mmol1−nLn/kg, 571–618mmol1−nLn/kg, and 317–1522mmol1−nLn/kg for sulfonamides, chloramphenicols, and non-antibiotic pharmaceuticals, respectively. The different adsorption affinity of sulfonamides might contribute to the different hydrophobic of heterocyclic substituents, while chloramphenicols adsorption was affected by the charge distribution in aromatic rings via substituent effects.
Transition-metal-catalyzed diazo activation is a classical way to generate metal carbene, which are valuable intermediates in synthetic organic chemistry. An alternative iodine-catalyzed diazo ...activation is disclosed herein under either photo-initiated or thermal-initiated conditions, which represents an approach to enable carbene radical reactivity. This metal-free diazo activation strategy were successfully applied into olefin cyclopropanation and epoxidation, and applying this method to pyrrole synthesis under thermal-initiated conditions further demonstrates the unique reactivity using this method over typical metal-catalyzed conditions.
Electron cryotomography is currently the only method capable of visualizing cells in three dimensions at nanometer resolutions. While modern instruments produce massive amounts of tomography data ...containing extremely rich structural information, data processing is very labor intensive and the results are often limited by the skills of the personnel rather than the data. We present an integrated workflow that covers the entire tomography data processing pipeline, from automated tilt series alignment to subnanometer resolution subtomogram averaging. Resolution enhancement is made possible through the use of per-particle per-tilt contrast transfer function correction and alignment. The workflow greatly reduces human bias, increases throughput and more closely approaches data-limited resolution for subtomogram averaging in both purified macromolecules and cells.
Using a combination of triazole-gold (TA-Au) and copper catalysts, the substituted furan was achieved in one pot through a three-step reaction cascade. The reaction tolerates a large substrate scope ...with simple starting materials. The desired di-, tri-, and tetrasubstituted furans were prepared in good to excellent yields.
This work designs an experimental model of tight sandstone with a closed cemented pre-existing fracture network (CCPF) to explore the influence of closed cemented natural fractures on the propagation ...behavior of hydraulic fracture (HF) in tight sandstone formations. The influence of CCPFs with different directions on the initiation, deflection, and propagation of HF is studied based on tri-axial hydraulic fracturing experiments with acoustic emission (AE) monitoring technology. The experimental results show four types of interaction behavior between HFs and CCPFs: deflection I; deflection II; penetration; and composite pattern. When the angle (α) between the HFs and CCPF is 0° ± 15°, their interaction is deflection I. During the process of hydraulic fracturing, the CCPF open with few AE events. When α = 90° ± 15°, the interaction between the HF and CCPFs includes deflection II and penetration patterns. The HF mainly extends in the rock matrix and is accompanied by significant AE events. When α = 45° ± 15°, the interaction is complicated and includes composite and deflection I patterns. The accumulated AE energy of composite interaction pattern shows a ladder-type increase. Under the same in-situ stress conditions, the HF geometry is the most complicated with the largest number of communicated natural fractures when the angle between the maximum principal horizontal stress direction and CCPF is 30°–60°. The experimental model designed in this paper can reproduce the complex propagation patterns of HFs in fractured tight sandstone formations, and the results provide a reliable basis for follow-up theoretical studies and engineering applications.
•A new experimental model of fractured tight sandstone formation is established which includes several groups of cemented closed fractures in different directions.•The complex fracture propagation patterns revealed the physical experiment of hydraulic fracturing combing the AE monitoring technology.•The relationship between the characteristics of injection pressure curve and fracture propagation patterns was explored.•Findings about the propagation mechanism of hydraulic fracture under the influence of closed cemented fracture was discussed.
A new type of alanine triazole (ATA) ligand was found to be an efficient partner for the stabilization of gold(III), thus rendering improved stability and high catalytic activities in allene ...synthesis and hydration reactions through the 3,3′‐arrangement of propargyl esters and propargyl alcohols. In addition to Au(I), ATA‐gold(III) was also proven to be an effective catalyst in promoting the formation of allenes with high yields. Furthermore, alanine triazole ruthenium has exhibited excellent potential as a means to catalyze borrowing hydrogen of alcohols and amines, ketones and alcohols.
Metamaterials have been increasingly used in the past few decades in the design of novel microwave circuits and sensor systems. This paper deals with the design of a split-ring resonator (SRR) sensor ...for microwave nondestructive evaluation (NDE) applications. Building on prior work in this field, a modified design of the sensor is used for imaging composites. The tip of the sensing ring is extended, and a reference ring is introduced to tailor fit the sensor for imaging and NDE applications. A built-in calibration system, integration of multiple sensors (high and low frequencies), super resolution capability, and high-Q factor are some of the benefits of the sensor. This paper presents the design and development of the sensor system along with experimental results demonstrating the feasibility of the approach for detection of sub-wavelength defects in composites and additive manufactured metals.
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