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A 2-iodoxybenzoic acid (IBX)–dimethyl sulfoxide (IBX-DMSO)-promoted oxidative aromatization of spiro[2.5]octa-4,7-dien-6-ones has been developed. A series of substrates with various substitutions were transformed into oxidative aromatization products in good to excellent yields. This oxidative aromatization features environmentally friendly reagents, high efficiency, a broad substrate scope, broad functional-group tolerance, and mild reaction conditions.

In recent years, methyl formate has received considerable attention as an ideal and green C1 building block to synthesize carboxylic esters. However, examples of a one-step route to esters with one-carbon elongation using methyl formate as a source of methoxycarbonyl radical are still rare. Herein, we present peroxide-induced radical carbonylation of

Source Data for paper "Topological spin-texture in the pseudogap phase of a high-Tc superconductor "

Simple and convenient visible-light-promoted radical monofunctionalization and difunctionalization of methylenecyclopropanes via ring-opening and cyclization processes have been developed for the syntheses of difluoromethyl compounds, alkyl compounds, halides, and sulfonyl compounds in moderate to excellent yields. The methodologies feature a wide substrate scope and tolerate various functional groups. A possible radical mechanism has been investigated and proven as a single electron transfer (SET) procedure.

In this paper, a novel immersion liquid pressure sensor based on the fiber Bragg grating (FBG)is introduced. Two FBGs are encapsulated in polymer in different forms, according to the deformation principle of the polymer under special constraints which is immersed in liquid, we can get the information of pressure in the liquid. Due to the use of a new packaging method, the proposed sensor can achieve distributed measurement on a single axis, which is difficult for liquid pressure sensor based on FBG to realize and is important for the measurement of pressure in special liquid environments. The sensing principle and mathematical model analysis of the sensor were first introduced and its sensing characteristics were analyzed by numerical simulation and the finite element simulation. The experimental result shows that the sensitivity of two sensors are 51.296 pm/MPa and 46.117 pm/MPa, it is consistent with the theoretical value within the working range of 0~15.5 MPa. The temperature compensation scheme is also considered in the designed sensor. Through the temperature calibration experiment, it is shown that the maximum average difference value is only 4.887 pm at a wide working temperature range 0~44.8° during the measurement.

Distributed block clamps are widely used in hydraulic piping systems. However, due to wear and tear over time, the clamps may loosen, and if not detected in the early stages, it can lead to the catastrophic results. The common methods to detect the clamp looseness are based on the monitoring the pre-load of the connected bolts. The Fiber Bragg Grating (FBG) sensors, as the emerging sensing technology with anti-electromagnetic interference, small size and lightweight, easy to install, corrosion resistant, durable, cost effective and multiplexed properties has been used to design smart bolts and smart washers in the existed literatures recently. However, the distributed features of the smart bolts are limited to the through-hole structures and the smart washer can only be used to the bolted connections with big-diameter bolts, which makes the smart bolts and washers difficult to apply to distributed clamp bolted with small-diameter bolts. Therefore, an FBG based smart clamp is presented for the first time in this paper. The theoretical models, i.e. the analytical model and Finite Element Model (FEM) are developed to derive the measurement principle and optimize the structure of the clamp. The calibration experiments of the smart clamp are conducted to obtain the sensitivity of the smart clamp. Subsequently, a practical application, i.e. clamp looseness detection, is given in an industrial piping system which shows that the smart clamp is high sensitive to the incipient looseness of the clamp.

Due to the risk of failure induced by vibration fatigue, performance testing and condition monitoring are important to hydraulic piping systems in some critical industries such as nuclear power, oil and gas, and aerospace. A multi-parameter dynamical measuring system using Fibre Bragg Grating (FBG) sensors is proposed to detect multiple physical parameters (strain, temperature, pressure, acceleration, etc.) in industrial hydraulic piping. This paper investigates the multi-parameter measuring principle of FBG and presents the framework of the proposed system. Multi-parameter dynamical measuring experiments on a hydraulic piping test platform were carried out to validate the system. Multiple parameters of the hydraulic piping were obtained and analysed in the time, frequency and modal domains. The results obtained by FBG sensors are in good agreement with those detected by the reference electrical and piezoelectric sensors. The proposed system was implemented to monitor the clamping looseness of the pipe. Experimental results indicate that the proposed system could be used for multi-parameter dynamical measurements and real-time condition monitoring of complex industrial hydraulic piping systems in harsh environments.

An efficient and novel visible-light-promoted radical difluoromethylation of enol acetates for the synthesis of α-CF

The beam-like structures are widely employed in civil, machinery, and aerospace engineering. However, the beam-like structure often suffers from undesired vibration problems due to the environmental incentives, which may influence the overall structural safety. Therefore, a real-time deformation monitoring system is critical to guarantee the safety of the beam-like structure under the condition of operating. This paper presents a novel deflection monitoring system that can be installed easily to any large-scale beam-like structures. The proposed system contains a sensing network, which is constructed of fiber Bragg grating (FBG). Such a network can monitor the quasi-distributed dynamic strain of the structure online, which has some merits such as anti-electromagnetic interference, small size, and multiplexed. An estimation algorithm for the beam-like structure based on those strain measurements is also presented in this work. The performance of the proposed sensing network and deflection estimation algorithm was validated by a cantilever beam test rig excited by impulsive excitations in the laboratory environment. The experimental results illustrate the suggested monitoring system can monitor the bending deformation of the beam-like structure successfully.

Realistic multi-span fluid-conveying pipe may contain various accessories such as valves, clamps, flanges , elastic supports and vibration absorbers under complex boundary conditions in engineering applications. The dynamic response of the multi-span pipe may be affected by the presence of accessories, giving rise to complex mode shapes. Simplified and reliable methods for multi-span mode shapes calculation from eigenvector of the characteristic equation are widely applied in the pipeline engineering community. However, current methods are not valid when it comes to the amplitude of the eigenvector with a resonance frequency . Consequently, corresponding stresses cannot be further evaluated exactly. To address the above mentioned issues, a novel Frequency Response Function (FRF)-based method is proposed in this paper for the calculation of the mode shapes exactly. Furthermore, a method combining the Spectral Analysis Method (SAM) and Transfer Matrix Method (TMM) is first proposed in this paper to obtain the natural frequencies and transient response for the cascaded pipeline. The results calculated by the present method are validated by comparing them with those obtained from existing literature and conventional Finite Element Method (FEM). The effects of the accessories on the vibration characteristics of the multi-span pipes are further analyzed.

The controlled transformation of materials, both their structure and their physical properties, is key to many devices. Ionic liquid gating can induce the transformation of thin-film materials over long distances from the gated surface. Thus, the mechanism underlying this process is of considerable interest. Here we directly image, using in situ, real-time, high-resolution transmission electron microscopy, the reversible transformation between the oxygen vacancy ordered phase brownmillerite SrCoO2.5 and the oxygen ordered phase perovskite SrCoO3. We show that the phase transformation boundary moves at a velocity that is highly anisotropic, traveling at speeds ~30 times faster laterally than through the thickness of the film. Taking advantage of this anisotropy, we show that three-dimensional metallic structures such as cylinders and rings can be realized. Our results provide a roadmap to the construction of complex meso-structures from their exterior surfaces., Local and reversible oxidation is used to exploit the very different properties of oxygen and vacancy ordered oxides. Here the authors directly image and make use of anisotropic migration velocities of oxygen in SrCoOx to create 3D meso-structures of those two phases by ionic liquid gating.

Epitaxial strain imposed in complex oxide ultrathin films is recognized as a powerful tool for controlling the ground state of correlated electron system. Here, we achieved simultaneous control of oxygen vacancies, orbital occupancy and magnetic ordering through the facile application of epitaxial strain, both tensile and compressive, in SrCoO3−δ oxygen “sponge” material rather than the ordinary manganites. The oxygen vacancies are enhanced greatly as the strain changes from smaller tensile 1.0% to larger tensile 2.0%, then to moderate compressive −1.0% in SrCoO3−δ films, associated with 3 − δ varying from ∼2.90 to ∼2.835, then to ∼2.72. Highest saturated magnetization is found in the thin films in small tension on La0.3Sr0.7Al0.65Ta0.35O3 substrate and lower values are found in larger tension on SrTiO3 and lowest values in moderate compression on LaAlO3. Meanwhile, electrons prefer to occupy the in-plan oriented orbitals for the tensile strain, in contrast to the preferential out-of-plane orbital occupancy for the compressive state associated with coupled intermediate spin-Co4+ (t2g4eg1)/high spin-Co3+ (t2g4eg2) in different proportions depending on strain states. Such controllable spin and orbital configurations lead to more robust magnetization in tensile strained SrCoO3−δ films than in its compressive counterpart. Our findings provide a nostrum for tailoring and controlling new magnetic, electronic and ionically active properties with strain engineering and further enrich orbital physics in cobaltites.

A new and efficient method for the synthesis of 1,3,4-oxadiazoles via the annulation of hydrazides with benzene-1,3,5-triyl triformate (TFBen) under metal-free conditions is reported. A broad range of hydrazides were transformed into the corresponding 1,3,4-oxadiazoles in good yields with excellent functional group tolerance.

Herein we present a new strategy for the dehydrogenative-decarboxylative coupling of indoles with glyoxylic acid. A broad range of indoles were transformed into the corresponding 3-formylindoles in moderate to good yields and excellent functional group tolerance. Notably, no N-formylation product was detected under our conditions.

Multiple-color-emissive graphene quantum dots (GQDs) have great potential in diverse applications such as bioimaging, light emission, and photocatalysis. Growing interest in GQDs is largely focused on their macro-scale aggregations that could inherit the unique properties of individual dots. However, the lack of advanced fabrication methods limits the practical applications of GQDs. Here, we employed a Langmuir-Blodgett (LB) technique to fabricate ultrathin, high-quality GQD aggregated films with well-modulated optical properties in a wide range of wavelengths. Through the combination of a bottom-up synthesis of GQDs and the LB assembly method, uniform, closely packed, and ultra-thin GQD films can be self-assembled with a well-controlled thickness on different substrates. The photoluminescence (PL) spectra of ultra-thin GQD films have an obvious red-shift compared with isolated GQD solution. We then elucidate remarkably strong energy transfer in self-assembled GQDs. Furthermore, the ultra-thin GQD films exhibit a clear excitation-dependent PL that could almost cover the entire visible light. This convenient self-assembly method and systematic optical and physical studies of ultra-thin GQD films may provide a new direction for developing low-cost, GQD film-based light-emitting devices.

A sustainable procedure for the synthesis of various alkyl arylacetates from benzyl alcohols has been developed. With palladium as the catalyst and organic carbonates as the green solvent and in situ activator, benzyl alcohols were carbonylated in an efficient manner without any halogen additives.

In this communication, we developed a new procedure for the direct carbonylative transformation of benzyl amines. Using dimethyl carbonate as the solvent, methyl 2-arylacetates can be produced in good to excellent yields from the corresponding primary, secondary, and tertiary benzyl amines with palladium as the catalyst. Notably, no base or any other additive is required here. In addition, our procedure can also be applied in the preparation of methylphenidate, which is a marketing drug and used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy.

A novel and efficient method for the carbonylative activation of benzotriazoles to benzoxazinones has been developed. By using a silver and palladium bimetallic catalyst system, a broad range of benzotriazoles were transformed into the corresponding benzoxazinones in moderate to good yields with excellent functional group tolerance. Notably, this procedure proceeds under neutral conditions.

A convenient procedure for the synthesis of N-(2-carbonylaryl)benzamides has been developed. Through Pd/C-catalyzed aminocarbonylation of anthranils with various hindered and functionalized aryl iodides, the desired amides were afforded in moderate to good yields. The protocol is advantageous due to the recyclable Pd/C catalyst, safe Mo(CO)6 as the solid CO source, and environmentally benign water as solvent. No inert atmosphere protection is needed.

A novel and convenient procedure for the synthesis of 3-acylindoles from simple indoles and aryl iodides has been established. Through ruthenium-catalyzed carbonylative C–H functionalization of indoles, with Mo(CO)6 as the solid CO source, the desired indol-3-yl aryl ketones were isolated in moderate to good yields. Not only N-alkylindoles but also N-H indoles can be applied here.

In this communication, we established an interesting palladium-catalyzed carbonylation protocol for the intramolecular cyclization of azoarenes. With Mo(CO)6 as the solid CO source and through C(sp2)−H bond activation, a series of azoarenes were transformed into the corresponding 2-arylindazolones in moderate to good yields. Notably, not only symmetrical azoarenes, but also unsymmetrical substrates underwent the reaction with excellent regioselectivity.

An interesting iron-catalyzed synthesis of 3-arylindoles from their corresponding nitrosoarenes and alkynes has been developed. By using iron(II) phthalocyanine as the catalyst precursor and CO as the reductant, broad range of nitrosoarenes and alkynes were transformed into the corresponding indoles in good yields with excellent functional groups tolerance. Remarkably, CO gas can be replaced by other reductants such as isopropanol as well.

A novel copper-catalyzed carbonylative cross-coupling between N-chloroamines and arylboronics acids has been developed. With copper(I) oxide as the catalyst, various desired amide compounds were produced in moderate to good yields. Functional groups such as iodide and alkene are tolerated. Notably, this is the first example of a copper-catalyzed aminocarbonylation with N-chloroamines.

International audience; Esters are important chemicals widely used in various areas, and alkoxycarbonylation represents one of the most powerful tools for their synthesis. In this communication, a new copper-catalyzed carbonylative procedure for the synthesis of aliphatic esters from cycloalkanes and alcohols was developed. Through direct activation of the Csp3 -H bond of alkanes and with alcohols as the nucleophiles, the desired esters were prepared in moderate-to-good yields. Paraformaldehyde could also be applied for in situ alcohol generation by radical trapping, and moderate yields of the corresponding esters could be produced. Notably, this is the first report on copper-catalyzed alkoxycarbonylation of alkanes.

An interesting procedure on palladium-catalyzed carbonylative synthesis of 3-methyleneisoindolin-1-ones from ketimines has been established. With 0.3 equivalent of Mo(CO)6 as the solid CO source via C(sp2)-H bond activation, moderate to good yields of the desired 3-methyleneisoindolin-1-ones were isolated.

This paper proposes a novel method to detect the liquid level. Specifically, a novel structure based on the diagram and the flexible hinge is presented, in which the Fiber Bragg Grating (FBG) is employed as the sensing element and temperature compensation is considered. The corresponding analytical model of the structure is developed, which shows that the strain of the FBG is a linear correlation with the liquid level. The presented sensor show superior range (±200mm) and superior sensitivity (23.80pm/mm) when compared with some of the similar structures shown in the literature. To validate the analytical model, a Finite Element Model (FEM) is employed and the results showed that the analytical model is accurate. This paper aims to give the structure design and performance analysis for the sensor and the corresponding experiments will be given in our subsequent paper series Part II.

The cantilever plate structure is widely used in wind tunnel nozzle segments. During the operation of the wind tunnel, the flexible steel plate will bear various complex loads such as shearing, bending and twisting, etc. The bolts of the plate are prone to loosen due to the fatigue damage. The methods based on the electromechanical impedance, sub-harmonic resonance and vision have been presented in the literature. However, the mentioned methods cannot detect the bolt looseness effectively in a harsh environment. To address this issue, we presented a novel method to detect the bolt looseness for the cascaded structures based on the operational strain estimated from Fiber Bragg Grating (FBG). In this work, an improved method of the operational modal analysis (OMA) presented in our previous work is employed. And then an enhanced Structural Damage Indicator (SDI) based on the operational strain is presented to detect and locate the loose bolts. Both the results from experiments and simulations showed that the SDI can detect and locate the loose bolts accurately.

In this paper, A semi-physical method for calculating time varying mesh stiffness and the dynamic response of gear system based on experimental strain data is studied. In a previous work, it was reported that dynamic strain on gear tooth root can be measured under normal operating condition using fiber Bragg Grating (FBG) sensors. This paper aims to compute gear dynamic response using experimental strain data and give an explanation of the fault propagation process. Using the dynamic strain data from FBG sensors, a method for calculating the dynamic response of gear system is proposed. Based on the theory of potential energy and material mechanics, the relationship between the bending strain of the tooth root and the time varying mesh stiffness is established. The time varying mesh stiffness and dynamic response of healthy gear and pitted gear are then calculated respectively. The force transmission during gear mesh under the condition of surface pitting is analyzed. It is concluded that in the case of pitting fault, there will be a significant loss of torque in the power transmission process due to the loss of contact area. It is further inferred that the loss of meshing force andthedecreasing of Hertzian contact stiffness are the major contributing factors for pitting fault. In addition, the semi-analytical method of computing gear dynamic response is validated with experimental study ofacceleration signal in the perspective of dynamic response.

Clamp looseness in hydraulic pipelines usually accelerates the wear process of pipelines and results in the fatigue fracture of pipelines. Conventionally, the condition monitoring of pipelines is often difficult and expensive due to the long length of pipes and large number of clamps that, in turn, requires a large capacity sensing network. In recent years, the fiber Bragg grating based sensing technique has begun to attract interests because of its cost-effective and ease of forming the large capacity sensing network. Therefore, this study investigates the feasibility of a new pipeline monitoring system instrumented with fiber Bragg grating sensors, which can measure the dynamic strain along the pipeline. The experiments were performed on a laboratory hydraulic pipeline system, where the impact hammer was used to excite the vibration of pipes. The preliminary selection of significant feature from the measured strain data is made with the use of principal component analysis. Then, the extracted feature with the reduced dimension is analyzed for the diagnosis of pipelines, which utilizes support vector machines to classify the location and severity of clamp looseness. The experimental results show the proposed sensing technique and diagnostic algorithm have a promising potential in developing an economic and reliable monitoring system for online diagnosis of hydraulic pipelines.

We report thickness dependent inhomogeneous antiferromagnetic (AFM) to ferromagnetic (FM) phase transitions in ultrathin $\mathrm{L}{\mathrm{a}}_{0.7}\mathrm{S}{\mathrm{r}}_{0.3}\mathrm{Mn}{\mathrm{O}}_{3}$ (LSMO) films grown on the $\mathrm{SrTi}{\mathrm{O}}_{3}$ substrate. When the films are 4--7 unit cells (UCs) thick, FM domains appear as isolated nanodisks in the AFM matrix that together floats on top of the three AFM base UCs, leading a superparamagnetic blocking behavior. Our first principles calculations unravel the rather counterintuitive physical origin of this mixed phase state; the formation of FM/AFM domain boundaries is energetically favorable. At 8 UCs, an abrupt shear strain relief occurs in the LSMO thin film and twinning patterns with two unit cell periodicity form along the [010] and [100] directions. Our studies reveal the complexity of the magnetic phase transition at the nanometer scale and open a door for the development of quantum devices and statistical theories.