Search

Novel nereistoxin derivatives containing phosphonate were synthesized and characterized via 31P, 1H and 13C NMR and HRMS. The anticholinesterase activity of the synthesized compounds was evaluated on human acetylcholinesterase (AChE) using the in vitro Ellman method. Most of the compounds exhibited good inhibition of acetylcholinesterase. All of these compounds were selected to assess their insecticidal activity (in vivo) against Mythimna separata Walker, Myzus persicae Sulzer and Rhopalosiphum padi. Most of the tested compounds displayed potent insecticidal activity against these three species. Compound 7f displayed good activity against all three insect species, showing LC50 values of 136.86 μg/mL for M. separata, 138.37 μg/mL for M. persicae and 131.64 μg/mL for R. padi. Compound 7b had the highest activity against M. persicae and R. padi, with LC50 values of 42.93 μg/mL and 58.19 μg/mL, respectively. Docking studies were performed to speculate the possible binding sites of the compounds and explain the reasons for the activity of the compounds. The results showed that the compounds had lower binding energies with AChE than with the acetylcholine receptor (AchR), suggesting that compounds are more easily bound with AChE.

A route determination strategy through non-targeted screening of chemical attribution signatures was developed to identify tabun samples from three different synthetic routes. The CAS profiles of tabun samples were obtained by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometer (GC×GC-TOFMS). The structures of 109 CAS were identified by NIST library and mass spectrometry fragment analysis. A few identified compounds could be traced to impurities in precursor compounds used in tabun synthesis. Based on the gas chromatography/mass spectrometry peak data of the selected CAS, partial least squares-discriminant analysis (PLS-DA) was used to extract the chemical attribution signatures of the characteristic compounds. The trained PLS-DA model performed well, with the lowest specificity and sensitivity values of 1.000 and 0.882, respectively. The performance of the PLS-DA model was further verified by unknown sample test set. The model demonstrated its ability to differentiate all the unknown tabun samples. The stability of chemical attribution signatures from different time periods was also investigated, and was further evaluated.

This paper reviews the background of the development of chemical attribution technology, and discusses analytical and chemometrics technologies for chemical warfare agents (CWAs) and highly toxic organophosphorus pesticides. The analytical methods include gas chromatography–mass spectrometry (GC–MS), liquid chromatography–mass spectrometry (LC–MS), infrared spectroscopy (IR), Raman spectroscopy, nuclear magnetic resonance spectroscopy (NMR), and other technologies. The chemometrics technologies include principal component analysis (PCA), hierarchical cluster analysis (HCA), partial least squares–discriminant analysis (PLS–DA), random forest (RF), and other technologies. The combination of these analytical techniques can be used to detect a variety of CWAs and highly toxic organophosphorus pesticides. All the reviewed information was collected through detailed searches on Scopus, PubMed and Web of Science using relevant keywords (such as chemical threat agents, chemical attribution and chemometrics). Most chemical attribution analyses of CWAs and highly toxic organophosphorus pesticides still rely on chromatography–mass spectrometry, such as GC–MS and LC–MS. Chemical attribution analysis involves sample composition analysis in addition to sample identification as well as sample traceability analysis. The analysis data involved is often relatively large, and thus chemometrics methods are required to adequately analyze the data. However, the analysis of mixtures of CWAs and related chemical substances remains challenging, and the analytical capabilities of the instrument need to be further improved. Although these technologies have high selectivity and application prospects, the analysis of real samples is still rare. Although the chemical attribution technology for CWAs and related chemical substances has been developed to a certain extent, the development of real sample analytical methods has not been well established or verified. In the future, it is expected that more analytical methods that address sensitivity, specificity, stability, and repeatability will be developed.

A series of thiophosphinyl amide [(Pz)2P(S)NHR] and thiophosphonyl diamide [PzP(S)(NHR)2] compounds, where Pz = 1,3,5-trimethylpyrazole and N(H)R = derivatives of 2-aminobiphenyl, were synthesized via a facile two-step process. Reaction of pyrazolyl substituted bromophosphine with 2-aminobiphenyl derivatives and further reaction with elemental sulphur affords the corresponding thiophosphinyl amide and thiophosphonyl diamide. The intermediate species was used without prior purification for reaction with sulphur to yield the target compounds. The nematicidal activity evaluation suggests that some compounds could manifest moderate nematicidal activity towards Meloidogyne incogita, which is higher than that of their amide analogue bixafen.

Microstructure modification is an effective approach to improve the mechanical properties of materials. In the present study, expanded graphite (EG) was added in a 20CrMnTi matrix to form pearlite microstructure and proeutectoid cementite after sintering. Mechanical alloying was used to obtain a fine milled mixture with a ball/powder weight ratio of 20:1. After mechanical alloying for 10 h, the milled mixtures with different EG contents were pressurelessly sintered at 1250 °C for 10 min and then hot-pressed at 1150 °C under 30 MPa for 30 min in Ar to obtain dense and modified 20CrMnTi materials. The content of EG has a profound influence on the microstructure and mechanical properties of 20CrMnTi. A high tensile strength of 1088 MPa and a high Vickers hardness of 4.7 GPa were achieved in the 1% EG-modified 20CrMnTi, which were increased by 105% and 28%, respectively, compared with the pure dense 20CrMnTi. The formed fine pearlite and small proeutectoid cementite in the modified microstructure contributed to the improved mechanical properties of 20CrMnTi.

As a member of low-carbon alloy steels, 20CrMnTi has been widely used to manufacture key-parts, such as gears and shafts, owing to its attractive fatigue resistance and easy of processing. To improve its the mechanical and frictional properties, the preparation of composite is required. In the present study, graphene was added in 20CrMnTi to form Gr/20CrMnTi composites by vacuum high-energy ball milling process and hot-pressing technique. The addition of graphene has a profound influence on the microstructure and properties of 20CrMnTi. A high hardness of 5.83 GPa and a good tensile strength of 1183 MPa were obtained in the 0.5 wt.%-Gr/20CrMnTi, increased by 18.5% and 27.8%, respectively. Meanwhile, the wear resistance reaches a maximum value of 2276.5 cm-3 in the 0.7 wt.%-Gr/20CrMnTi, showing a 491.1% increase than that of pure 20CrMnTi. The layered graphene played an important role in absorbing energy and preventing the propagation of micro-crack.

A series of thiophosphinyl amide [(Pz)

Self-healing property of ceramics is highly attractive in meeting the safety and durability requirements of high temperature structural components. This work reports on the crack healing behavior of MoAlB, together with its oxidation resistance. The MoAlB material showed a good oxidation resistance due to the formation of a dense and thin Al2O3 scale in the temperature range 1200–1300 °C for 10 h. The crack healing behavior as a function of temperature and healing time was studied. For the healed samples, the strength recovery almost returned to the initial strength. Healing is accomplished by the formation of only Al2O3 in the site of damage. The microstructure and the phase composition of samples before and after healing were characterized with scanning electron microscopy and x-ray diffraction method, respectively.

MoAlB has been the only known compound with attractive oxidation resistance in the MAB family so far. To widen the application of the MoAlB material in high temperature environments where temperature change is abrupt, the investigation of its thermal shock behavior is required. A dense MoAlB material was prepared by hot pressing of Mo, Al and B elemental powders at 1200 °C with 25 MPa for 1 h in Ar atmosphere. Thermal shock resistance of the synthesized MoAlB material was investigated by quenching in water from various temperatures. The residual strength of MoAlB showed a slow decrease trend after quenching from 600 °C to 1400 °C. The MoAlB material exhibits better thermal shock resistance than another MAB phase of Fe2AlB2. X-ray diffractometry was used to identify the phase composition, and scanning electron microscopy was adopted to characterize the microstructure.

Owing to the current environmental awareness, the development of environmentally friendly reactions in aqueous media is the subject of an increasing number of studies. Hence, we report a novel three-component reaction of alkyl halides, thiourea and Bunte salts using non-toxic H2O as a benign reaction medium. After heating for 7 h, various unsymmetrical disulfides in high purity could be prepared in up to 92% yield. The substrates are readily available and the protocol does not require either extra oxidant or reductant. In addition, no transition metal catalyst was required, making this process environmentally and economically friendly.

Albumin is a new biomarker of organophosphorus compounds (OPs) and nerve agents (OPNAs) for retrospective verification. Recent studies on OPs adducts show that amino acid residues can covalently bind to OPs and OPNAs. In this article, after being incubated with soman, sarin, cyclosarin, VX, ethyl tabun, and propyl tabun, human serum albumin (HSA) is analyzed by quadrupole-Orbitrap mass spectrometer (Q Exactive LC-MS/MS). In addition to the three known phosphonylated sites, six new sites modified by OPNAs are detected. To identify the most reactive residue, we calculate the area ratio of the modified peptides to the whole peptides. The result demonstrates that tyrosine 263 (Y263) in peptide Y263ICENQDSISSK, which has been poisoned with six kinds of nerve agents, possesses the highest reactivity. The structure characteristics based on molecular simulation provide a theoretical evidence for the reactivity of the nine binding sites. It suggests that Y263 also has the potential to be used as a biomarker to detect OPNAs exposure, and the presented Q Exactive LC-MS/MS method might be of relevance for the verification of new phosphonylated sites.

Chemical forensics has been widely recognized as an important tool to investigate alleged use of chemical weapons and/or to identify the illicit production of chemical warfare agents. This paper describes the use of gas chromatography and mass spectrometry (GC-MS) to determine chemical attribution signatures (CAS) N,N-dimethylphosphoramidic dichloride (DMPADC), a key precursor of tabun, for tracking the production of tabun. Synthetic samples were identified and classified by using GC-MS and chemometrics. Analysis samples (n = 27) were collected from three synthetic DMPADC routes; 20 potential CAS were identified, and the structures of five CAS were assigned. Principal component analysis (PCA) was performed to summarize the distribution trend of the samples and to check for the presence of outliers. A Partial least squares discriminant analysis (PLSDA) model was established to discriminate and classify the synthetic samples. The proposed model in this paper has high predictive ability, and the test set samples can be correctly categorized.

Since the intrinsic characteristics of self-synchronization vibration system, the implementation of in-phase synchronization state is restricted, which leads to unsatisfactory force of dual-rotor system driven by two coaxial motors in the space. Thus, control synchronization is proposed in this paper to address the problems above. Firstly, to explore the defects of the self-synchronization vibration system, dynamic model of the dual-rotor space vibration system is established, and the self-synchronization mechanism of two eccentric rotors (ERs) is analyzed by small parameter average method. Subsequently, to implement the in-phase synchronization between the two ERs, controllers based on master–slave control structure (MSCS) and sliding mode control (SMC) algorithm are systematically designed. Finally, the effectiveness of self-synchronization mechanism and control-synchronization method is validated by simulations in Matlab/Simulink. The results show that the anti-phase synchronization state is appeared on account of small horizontal distance or larger installation height of the two ERs; however, with the application of controllers, the phase difference (PD) of the two ERs is successfully controlled at zero, and the strong robustness of the controllers is further demonstrated by the variations of rotation velocity and structural parameter.

Nerve agents (NAs) are notorious chemical warfare agents that pose a serious threat to national security and public health. The total number of theoretical chemicals of NAs and their degradation products (DPs) exceeds 410 000, according to 1.A.01-1.A.03 in the Schedules of Chemicals of the Chemical Weapons Convention, which poses great challenges for identification and verification. A three-step integrated untargeted screening strategy was developed based on high-resolution mass spectrometry. First, an extensible homemade library for targeted screening of common classical agents was established. Second, a set of in-source collision-induced dissociation mass spectrometry (MS)-alerting ions was extracted and concluded based on fragmentation behavior studies, which included 40 specific alerting ions and 10 types of characteristic structural fragments from total NAs and their DPs. A novel "alerting ion" searching method was developed to rapidly and sensitively screen whether or not nerve agent-related compounds were present and of which type they were. Third, we built a theoretical exact mass database including 202 accurate masses or molecular formulas, which could cover all structural possibilities of the NAs and their DPs. Comprehensively, the elemental composition of pseudomolecular ions, fragment ions, MS/MS spectra, and isotope pattern information were obtained from the full scan MS/data dependent-MS

Rationale Organophosphorus nerve agents are highly toxic because they inhibit acetylcholinesterase activity, thereby causing a series of symptomatic poisoning. Upon entering the body, nerve agents bind active amino acid residues to form phosphonylated adducts. A potentially beneficial method for specific verification of exposure of nerve agents is based on albumin adducts, which have a half-life of 18 days. This appears to be more effective than the fluoride reactivation method, based on acetylcholinesterase. Methods After the exposure of human serum albumin to nine nerve agents, human serum albumin was denatured, reduced, alkylated and digested with trypsin according to standard mass spectrometry-based proteomics procedures. The phosphonylated peptides of human serum albumin were identified using positive ion electrospray ionization with a quadrupole orbitrap mass spectrometer. Results The peptide KVPQVSTPTLVESR showed a good mass spectrometric response to the nine nerve agents. The tendency of sarin and cyclosarin was to bind to S419 on the peptide, while the other nerve agents (tabun, soman and V-type nerve agents) were shown to bind more readily to K414 on the peptide. Conclusions This research revealed a new site, S419, of the tryptic peptide KVPQVSTPTLVEVSR on human albumin to be a valuable biomarker for sarin/cyclosarin exposure, helping to further distinguish sarin and cyclosarin poisoning from that of other nerve agents and providing an important tool for the identification of sarin or cyclosarin in terrorist attacks.

The nanolaminated ternary boride Fe2AlB2 exhibits a combination of damage tolerance, electrical conductivity, and machinability at room temperature. This work reports for the first time on the thermal stability and thermal shock resistance of Fe2AlB2 at high temperatures. The thermal stability of Fe2AlB2 at temperatures up to 1300 °C in Ar atmosphere was studied. Fe2AlB2 intensively decomposed at 1236 °C in Ar atmosphere. The thermal shock resistance was investigated using the water-quenching method in the temperature range 600–1200 °C. The residual strength of the quenched Fe2AlB2 decreased continuously with increasing temperatures. The phase composition, phase transformation and microstructure were characterized with X-ray diffractometry, differential scanning calorimetry and scanning electron microscopy.

V-type agents are highly toxic organophosphorus nerve agents that inhibit acetylcholinesterase in the nervous system, causing a series of poison symptoms. Trace analytical methods are essential for the specific verification of exposure to these agents, especially for human exposure. This paper investigates the phosphonylated and disulfide adducts between human ceruloplasmin and O-ethyl S-(2-(diisopropylamino)ethyl) methylphosphonothioate (VX), O-isobutyl S-(2-(diethylamino)ethyl) methylphosphonothioate (VR), and O-butyl S-(2-(diethylamino)ethyl) methylphosphonothioate (Vs). After being digested by trypsin, the mixture of peptides was separated by a nano-liquid chromatography (nano-LC) and analyzed using quadrupole-orbitrap mass spectrometry (Q-Orbitrap-MS). The sensitive LC-MS/MS-assisted proteomics approach was developed to achieve the identification of human exposure to V-type agents based on these modified sites; results revealed that potential biomarkers could be derived from adducts based on the sulfur- and phosphorus-containing groups of V-type agents. This work offered a novel insight into the mechanism of disulfide-containing adducts resulting from the replacement of disulfide bridges by the thiolate groups from the V-type agents. Moreover, four disulfide adducts on human ceruloplasmin were also discovered during this research, specifically confirming exposure to the V-type agents. Furthermore, molecular simulation testified to the reactivity of the modified sites. Collectively, our findings suggest that the eleven binding sites on human ceruloplasmin have the potential use as a selective marker for prediction the V-type agent exposure in humans.

Upon entering the body, nerve agents can bind active amino acid residues to form phosphonylated adducts. Tabun derivatives (O-alkyl-N,N-dialkyl phosphoroamidocyanidates) have strikingly different structural features from other G-series nerve agents, such as sarin and soman. Here, we investigate the binding mechanism for the phosphonylated adducts of nerve agents of tabun derivatives. Binding sites for three tabun derivatives, O-ethyl-N,N- dimethyl phosphoramidocyanidate (GA), O-ethyl-N,N-ethyl(methyl) phosphoramidocyanidate, and O-ethyl-N,N-diethylphosphoramidocyanidate were studied. Quadrupole-orbitrap mass spectrometry (Q-Orbitrap-MS) coupled to proteomics was used to screen adducts between tabun derivatives and albumin, immunoglobulin, and hemoglobin. The results reveal that all three tabun derivatives exhibit robust selectivity to lysine residues, rather than other amino acid residue types. A set of 10 lysine residues on human serum albumin are labeled by tabun derivatives in vitro, with K525 (K*QTALVELVK) and K199 (LK*CASLQK) peptides displaying the most reactivity. Tabun derivatives formed stable adducts on K525 and K414 (K*VPQVSTPTLVEVSR) for at least 7 days and on K351 (LAK*TYETTLEK) for at least 5 days in a rabbit model. Three of these peptides-K525, K414, and K351-have the highest homology with human serum albumin of all 5 lysine residues that bound to examined rabbit blood proteins in vivo. Molecular simulation of the tabun-albumin interaction using structural analysis and molecular docking provided theoretical evidence supporting lysine residue reactivity to phosphonylation by tabun derivatives. K525 has the lowest free binding energy and the strongest hydrogen bonding to human albumin. In summary, these findings identify unique binding properties for tabun derivatives to blood proteins.

A major challenge in organophosphate compound (OP) and OP nerve agent (OPNA) research has been in the identification and utilization of reliable biomarkers for rapid, sensitive, and efficient detection of OP exposure. Albumin has been widely studied as a biomarker for retrospective verification of exposure to OPNAs, including soman (GD), by detecting the phosphonylation of specific amino acid residues. The aim of the present study was to identify binding sites between GD and rabbit serum albumin in vitro and in vivo. A nano-liquid chromatography coupled with a quadrupole-orbitrap mass spectrometry (nLC-Q-Orbitrap-MS) was used to examine the GD-modified adducts of rabbit albumin. A total of 11 GD-modified sites were found in rabbit serum albumin across three experimental models. The following five GD-modified rabbit albumin sites, which were all lysine residues, were established in vivo: K188, K329, K162, K233, and K525. Two of these five lysine residues, K188 in peptide EK*ALISAAQER and K162 in peptide YK*AILTECCEAADK, were stable for at least 7 days in vivo. Molecular simulation of the GD–albumin interaction provided theoretical evidence for reactivity of the identified lysine residues. The findings suggest that these modifiable lysine residues are potential biomarkers of GD exposure for retrospective analysis by Q-Orbitrap-MS.

NN-based force fields development has shown its merit of low cost, accuracy and versatility; where the choice of descriptors plays a central role. In this contribution, descriptors representing atomic environments with/without nuclear charges are employed respectively to construct force fields for three elemental materials Fe, Cr and Al. The descriptions of the force fields can be unified when the nuclear charges are included as one descriptor. This strategy greatly enhance the efficiency of force fields building for different elemental materials, which is treated as feasible and can be extendable to other types of elemental and multi-elemental materials.

The MAB phase MoAlB has attractive properties both at room and high temperatures. To further improve its properties, a possible way is to form solid solutions by partially substituting one of constituting elements in MoAlB. This work reports on the synthesis of MoAl1-xSixB solid solutions by powder metallurgy. Influences of sintering temperature, dwelling time, and composition of starting mixture on the solubility limit of Si in MoAlB have been investigated. The maximum solubility of Si was 0.91 at.%, corresponding to x = 0.03. Increase of Si content in the starting mixtures caused the formation of other competing phases. Phase composition and microstructure were characterized by x-ray diffraction method and scanning electron microscopy. A dense MoAl0·97Si0·03B solid solution has been achieved by hot-pressing a MoB/1.3Al/0.1Si mixture at 1200 °C with 25 MPa for 1 h, and its mechanical properties have been measured. An increase in strength and hardness is achieved by solid-solution strengthening. The flexural strength and the hardness of the solid solution are higher than those of MoAlB, viz. 385 MPa vs 307 MPa, and 14.89 GPa vs 8.43 GPa.

The mechanical properties of nickel-based single crystal superalloys deteriorate with increasing misorientation, thus the finished product rate of the casting of single crystal turbine airfoils may be reduced due to the formation of grain boundaries especially when the misorientation angle exceeds to some extent. To this day, evolution of the microstructures at the grain boundaries with misorientation and the relationship between the microstructures and the mechanical properties are still unclear. In this work a detailed characterization of the misorientation related microstructure at the grain boundary in DD6 single crystal superalloy has been carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques; the elemental distribution at the grain boundaries has been analyzed by energy dispersive (EDS) X-ray mapping; and the effect of precipitation of μ phases at the grain boundary on the mechanical property has been evaluated by finite element calculation. It is shown that the proportion of γ phase at the grain boundaries decreases, while the proportion of γ′ phase at the grain boundaries increases with increasing misorientation; the μ phase is precipitated at the grain boundaries when the misorientation angle exceeds about 10° and thus it could lead to a dramatic deterioration of the mechanical properties, as well as that the enrichment of Re and W gradually disappears as the misorientation angle increases. All these factors may result in the degradation of the mechanical properties at the grain boundaries as the misorientation increases. Furthermore, the finite element calculation confirms that precipitation of μ phases at the grain boundary is responsible for the significant deterioration of the mechanical properties when the misorientation exceeds about 10°. This work provides a physical imaging of the microstructure for understanding the relationship between the mechanical properties and the misorientation of the grain boundaries in the single crystal superalloy. Based on our study we hope that we can offer some scientific basis for further improvement of the nickel-based single crystal superalloys.

The synthesis of sulfides is important in various fields. This paper reports an efficient, odorless, and viable protocol for the base-mediated synthesis of benzyl alkyl sulfides using thiourea. The...

To investigate the impact of green tea on urinary oxalate excretion in healthy male volunteers. The oxalate concentrations after different brewing times (2–60 min) of different qualities (2–8 g) of green tea were measured in in vitro experiment. In in vivo experiment, the effects on urine composition were assessed in 12 healthy men with an age of 24–29 years. Each subject was requested to collect two 24-h urine samples under normal dietary conditions. Green tea prepared from tea bags containing 2 g of tea leafs was consumed by the subjects for 7 consecutive days, and 24-h urine samples were collected and analyzed on days 6 and 7. After 3-week washout interval, all subjects consumed green tea containing 4 g of leaf tea for another 7 consecutive days. Two 24-h urine samples were collected on the last 2 days. Urine volume, pH, calcium, magnesium, sodium, phosphate, potassium, chloride, citrate, oxalate, urate and creatinine were measured. In the in vitro experiments, oxalate in solution increased with brewing time (p

Thiourea is very useful in the synthesis of asymmetric and symmetric disulfides. In this paper, we report an efficient, odorless, and one-pot procedure for the synthesis of benzyl alkyl disulfides by using the mixtures of thiourea, alkyl halides, and benzyl thiocyanates. The reaction was carried out in water with the assistance of microwaves, enabling a time-saving process. Optimal conditions were obtained as follows: benzyl thiocyanate (1.0 equiv.), thiourea (2.0 equiv.), and alkyl halide (1.2 equiv.) were reacted under microwave irradiation using K3PO4 as the base in water at 90 °C for 15 min. In most cases, the yields are higher than 80%. In this protocol, the substrates are readily available and their synthesis is much easier than the corresponding thiols. Moreover, it is environmentally and economically friendly.

Tabun has been shown to form phosphylated adducts on tyrosine residues in albumin in vivo and in vitro. However, in this work, tabun-labeled lysine adducts were found in albumin. Three types of albumin were treated with overdose of tabun in vitro and 17 tabun-labeled lysine residues were found: K4, K12, K224, K377, and K524 in bovine albumin, K186, K188, K212, K329, K414, and K525 in leporine albumin, and K79, K186, K188, K212, K376, and K525 in rat albumin. To investigate the modification of tabun in vivo, three leporines were injected with 0.8×LD50 dose of tabun. The results showed that the labeled lysine residues in vivo, were consistent with modified lysines in vitro. Structure characteristics and the binding mode of 6 tabun-labeled lysines of leporine albumin were further analyzed using theory simulation and molecular docking in Discovery Studio. For the first time, we show that tabun-labeled lysine peptides are found in vivo and in vitro. These modified lysine peptides are good biomarkers for exposure to tabun in albumin of leporine and rat.

Thiourea is very useful in the synthesis of asymmetric and symmetric disulfides. In this paper, we report an efficient, odorless, and one-pot procedure for the synthesis of benzyl alkyl disulfides by using the mixtures of thiourea, alkyl halides, and benzyl thiocyanates. The reaction was carried out in water with the assistance of microwaves, enabling a time-saving process. Optimal conditions were obtained as follows: benzyl thiocyanate (1.0 equiv.), thiourea (2.0 equiv.), and alkyl halide (1.2 equiv.) were reacted under microwave irradiation using K3PO4 as the base in water at 90 °C for 15 min. In most cases, the yields are higher than 80%. In this protocol, the substrates are readily available and their synthesis is much easier than the corresponding thiols. Moreover, it is environmentally and economically friendly.

Based on our experimental observations of the resonant stimulated Raman gain and loss spectra in Rb atomic vapor, we propose an alternative interpretation of electromagnetically induced transparency (EIT). We find that, in the presence of a coupling field, a probe beam can exhibit both gain and loss depending on the frequencies of the incident beams. The gain and loss can coexist in a Doppler-broadened system, leading to polarization interference between atoms of different velocities, with a sharp transition from gain to loss as the probe-field frequency is scanned. We use the concept of Raman gain, instead of the commonly accepted quantum Fano interference, to explain the phenomenon of EIT and its transparency window as being due to the suppression of linear absorption by the Raman gain. Using this concept, the phenomena of EIT and Autler-Townes splitting may be explained within the same framework.

Numerical modeling of transmission tower-line systems subjected to stochastic wind loads is presented. Dynamic responses of transmission tower-line systems with different structural parameters in stochastic wind fields with various average wind velocities are carried out by ABAQUS software. Based on the dynamic swing angles of the insulator strings, dynamic wind load factors are suggested to determine the swing angle of suspension insulator string in tower head design. The dynamic wind load factors are dependent on the reliability requirement of the designed transmission line.

The effects of Doppler broadening on Autler-Townes (AT) splitting in six-wave mixing (SWM) are investigated by the dressed-state model. We analyze the velocities at which the atoms are in resonance with the dressed states through Doppler frequency shifting and find that, depending on the wave-number ratio, there may be two resonant velocities which can originate from resonance with one of the dressed states or from resonance with two different dressed states. Based on this model, we discuss a novel type of AT doublet in the SWM spectrum, where macroscopic effects play an important role. Specifically, the existence of resonant peaks requires polarization interference between atoms of different velocities in addition to a change in the number of resonant atoms involved. Our model can also be employed to analyze electromagnetically induced transparency resonance and other types of Doppler-free high-resolution AT spectroscopy.

We measure the absorption and dispersion in a Doppler-broadened Λ-type three level system by resonant stimulated Raman spectroscopy with homodyne detection. Through studying the dressed state energies of the system, it is found that the absorption and dispersion satisfy the Kramers–Kronig relation. The absorption and dispersion spectra calculated by employing this relation agree well with our experimental observations.

Based on Akaike's information criterion (AIC) for a coherently driven ensemble of cold rubidium atoms, we study the crossover between electromagnetically induced transparency (EIT) and Autler–Townes (AT) splitting from the dispersion as well as the absorption viewpoint. We find that the dispersion signal is more sensitive than the absorption signal, showing more pronounced features in the Akaike per-point weights spectrum, which provides a cleaner way of discerning EIT from AT splitting.

The threshold for the transition between Autler–Townes splitting (ATS) and electromagnetically induced transparency (EIT) is studied through examining the dynamics of decaying dressed states, which are derived from the effective Hamiltonian. It is found that the threshold corresponds to the suppression of the Rabi oscillation of the populations by the relaxation as the coupling field becomes weak. Moreover, ATS and EIT belong to two different regimes, the former being in the non-perturbation regime, where there is coherent Rabi oscillation of the populations of the states coupled by the coupling field. By contrast, EIT is in the perturbation regime, and the transparency window in the EIT resonance can be explained as being due to the gain of the four-wave mixing process. Experiments are performed in cold rubidium atoms, where both the absorption and dispersion are measured, showing that EIT can be discriminated from ATS through Fourier transformation of the spectra. Compared to the statistical method proposed by Anisimov et al (2011 Phys. Rev. Lett. 107 163604), our method is more direct and is deterministic.