Advance in the chemical synthesis and magnetic properties of nanostructured rare-earth-based permanent magnets

Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.

Incidence, casualties and risk characteristics of civilian explosion blast injury in China: 2000-2017 data from the State Administration of Work Safety

Background: Civilian explosion blast injury is more frequent in developing countries, including China. However, the incidence, casualties, and characteristics of such incidents in China are unknown.Methods: This is a retrospective analysis of the State Administration of Work Safety database. Incidents during a period from January 1, 2000 to April 30, 2017 were included in the analysis. The explosions were classified based on the number of deaths into extraordinarily major, major, serious and ordinary type. Descriptive statistics was used to analyze the incidence and characteristics of the explosions. Correlation analysis was performed to examine the potential correlations among various variables.Results: Data base search identified a total of 2098 explosions from 2000 to 2017, with 29,579 casualties: 15,788 deaths(53.4%), 12,637 injured(42.7%) and 1154 missing(3.9%). Majority of the explosions were serious type(65.4%). The number of deaths(39.5%) was also highest with the serious type(P=0.006). The highest incidence was observed in the fourth quarter of the year(October to December), and at 9:00–11:00 am and 4:00–6:00 pm of the day. The explosions were most frequent in coal-producing provinces(Guizhou and Shanxi Province). Coal mine gas explosions resulted majority of the deaths(9620, 60.9%). The number of explosion accidents closely correlated with economic output(regional economy and national GDP growth rate)(r=–0.372, P=0.040;r=0.629, P=0.028).Conclusions: The incidence and civilian casualties due to explosions remain unacceptable in developing China. Measures that mitigate the risk factors are of urgently required.

Effect of thermally induced birefringence on high power picosecond azimuthal polarization Nd:YAG laser system

Pulse-burst 1064-nm picosecond azimuthal polarization beam amplification up to an average power of 16.32 W using side-pumped Nd: YAG amplifiers has been demonstrated. The maximum envelop energy as much as 16.32 mJ, corresponding to a power amplification factor of 299.5%. A simple criterion was defined to help estimate the amount of depolarization in Nd:YAG amplifier stages. The degree of depolarization of the beam was 7.1% and the beam quality was measured to be M2= 3.69. The reason for the azimuthal polarization depolarization and beam quality degradation were explained theoretically and experimentally during the amplification process.

Towards High-Dimensional Entanglement in Path:Photon-Source Produced from a Two-Dimensional Atomic Cloud

A photon source with high-dimensional entanglement is able to bring increasing capacity of information in quantum communication.The dimensionality is determined by the chosen degree of freedom of the photons and is limited by the complexity of the physical systems.Here we propose a new type of high-dimensional entangled photon source,generated via path-indistinguishable scheme from a two-dimensional atomic cloud,which is prepared in a magneto-optical trap.To verify the photon source,we demonstrate experimentally the quantum state of the single photons heralded by its partner photon,with homodyne tomographic technology.

Numerical study on dynamic mechanism of brain volume and shear deformation under blast loading

Blast-induced traumatic brain injury(b-TBI)is a kind of significant injury to soldiers in the current military conflicts.However,the mechanism of b-TBI has not been well understood,and even there are some contradictory conclusions.It is crucial to reveal the dynamic mechanism of brain volume and shear deformations under blast loading for better understanding of b-TBI.In this paper,the numerical simulation method is adopted to carry out comprehensive and in-depth researches on this issue for the first time.Based on the coupled Eulerian-Lagrangian method,the fluid-structure coupling model of the blast wave and human head is developed to simulate two situations,namely the head subjected to the frontal and lateral impacts.The simulation results are analyzed to obtain the underlying dynamic mechanisms of brain deformation.The brain volume deformation is dominated by the local bending vibration of the skull,and the corresponding frequency for the forehead skull under the frontal impact and the lateral skull faced to the lateral impact is as high as 8 kHz and 5 kHz,respectively.This leads to the high-frequency fluctuation of brain pressure and the large pressure gradient along the skull,totally different from the dynamic response of brain under head collisions.While the brain shear deformation mainly depends on the relative tangential displacement between the skull and brain and the anatomical structure of inner skull,being not related to the brain pressure and its gradient.By further comparing the medical statistics,it is inferred that diffuse axonal injury and brain contusion,the two most common types of b-TBI,are mainly attributed to brain shear deformations.And the von Mises stress can be adopted as the indicator for these two brain injuries.This study can provide theoretical guidance for the diagnosis of b-TBI and the development of protective equipment.

Risk-Averse Two-Stage Distributionally Robust Economic Dispatch Model Under Uncertain Renewable Energy

With the participation of large quantities of renewable energy in power system operations,their volatility and intermittence increases the difficulties and challenges of power system economic scheduling.Considering the uncertainty of renewable energy generation,based on the distributionally robust optimization method,a two-stage economic dispatch model is proposed to minimize the total operation costs.In this paper,it is assumed that the fluctuating of renewable power generation follows the unknown probability distribution that is restricted in an ambiguity set,which is established by utilizing the first-order moment information of available historical data.Furthermore,the theory of conditional value-at-risk is introduced to transform the model into a tractable model,which we call robust counterpart formulation.Based on the stochastic dual dynamic programming method,an improved iterative algorithm is proposed to solve the robust counterpart problem.Specifically,the convergence optimum can be obtained by the improved iterative algorithm,which performs a forward pass and backward pass repeatedly in each iterative process.Finally,by comparing with other methods,the results on the modified IEEE 6-bus,118-bus,and 300-bus system show the effectiveness and advantages of the proposed model and method.

Research progress on rapid psychological regulation of pathogenic microorganism epidemic situation

Pathogenic microbial biological epidemics can cause negative emotions such as fear,anxiety,loneliness and depression,as well as somatization symptoms such as insomnia,headache,chest tightness and degenerative behavior.As a secondary disaster of major epidemic situation,this kind of adverse psychological stress needs to be adjusted quickly.The author reviews the rapid psychological regulation methods of novel coronavirus pneumonia(coronavirus disease 2019,Covid-19),aiming to provide a useful enlightenment for the prevention of psychological stress in microorganism epidemic situation.

Fe5C2 nanoparticles as low-cost HER electrocatalyst:the importance of Co substitution

Constructing and understanding the doping effect of secondary metal in transition metal carbide(TMC)catalysts is pivotal for the design of low-cost hydrogen evolution reaction(HER) electrocatalysts. In this work, we developed a wet-chemistry strategy for synthesizing Co-modified Fe_5C_2 nanoparticles((Fe_(1-x)Cox)_5C_2 NPs) as highly active HER electrocatalysts in basic solution. The structure of(Fe_(1-x)Cox)_5C_2 NPs was characterized by X-ray diffraction(XRD), extended X-ray absorption fine structure spectra(EXAFS) and scanning/transmission electron microscopy(S/TEM), indicating that the isomorphous substitution of cobalt in the lattice of Fe_5C_2.(Fe_(0.75) Co_(0.25))_5C_2 exhibited the best HER activity(174 mV for j = -10 mA/cm^2). Computational calculation results indicate that Co provides the most active site for HER. X-ray adsorption spectra(XAS) studies further suggested that the electron transfer in Fe–C bonds are enhanced by the substitution of Co, which modulates the hydrogen adsorption on the adjacent electronic-enriched carbon, and therefore promotes HER activity. Our results affirm the design of lowcost bimetallic TMCs based HER catalysts.

Investigation on Centrifugal Impeller in an Axial-radial Combined Compressor with Inlet Distortion

Assembling an axial rotor and a stator at centrifugal compressor upstream to build an axial-radial combined compressor could achieve high pressure ratio and efficiency by appropriate size augment.Then upstream potential flow and wake effect appear at centrifugal impeller inlet.In this paper,the axial-radial compressor is unsteadily simulated by three-dimensional Reynolds averaged Navier-Stokes equations with uniform and circumferential distorted total pressure inlet condition to investigate upstream effect on radial rotor.The results show that spanwise nonuniform total pressure distribution is generated and radial and circumferential combined distortion is formed at centrifugal rotor inlet.The upstream stator wake deflects to rotor rotation direction and decreases with blade span increases.Circumferential distortion causes different separated flow formations at different pitch positions.The tip leakage vortex is suppressed in centrifugal blade passages.Under distorted inlet condition,flow direction of centrifugal impeller leading edge upstream varies evidently near hub and shroud but varies slightly at mid-span.In addition,compressor stage inlet distortion produces remarkable effect on blade loading of centrifugal blade both along chordwise and pitchwise.

Spectral reflectance response to nitrogen fertilization in field grown corn

This study was carried out to analyze the spectral reflectance response of different nitrogen levels for corn crops.Four different nitrogen treatments of 0%,80%,100%and 120%BMP(best management practice)were studied.Principal component analysis-loading(PCA-loading)was used to identify the effective wavelengths.Partial least squares(PLS)and multiple linear regression(MLR)models were built to predict different nitrogen values.Vegetation indices(VIs)were calculated and then used to build more prediction models.Both full and selected wavelengths-based models showed similar prediction trends.The overall PLS model obtained the coefficient of determination(R^(2))of 0.6535 with a root mean square error(RMSE)of 0.2681 in the prediction set.The selected wavelengths for overall MLR model obtained the R^(2) of 0.6735 and RMSE of 0.3457 in the prediction set.The results showed that the wavelengths in visible and near infrared region(350-1000 nm)performed better than the two either spectral regions(1001-1350/1425-1800 nm and 2000-2400 nm).For each data set,the wavelengths around 555 nm and 730 nm were identified to be the most important to predict nitrogen rates.The vogelmann red edge index 2(VOG 2)performed the best among all VIs.It demonstrated that spectral reflectance has the potential to be used for analyzing nitrogen response in corn.

Upper limb arthromyodynia can be treated with Notopterygium by down-regulating P2X3 to mediate PKC-induced inflammatory response

Rheumatoid arthritis(RA)is one of the most common refractory diseases in the world,and traditional Chinese medicine Notopterygium(NE)has been used in the treatment of upper limb pain for a long time.NE can significantly reduce the expression of inflammatory pain target P2X3 receptor in rats with upper-limb arthritis.To verify the relationship between the mechanism of NE for“upper limb paralysis”and the P2X3 receptor-mediated PKC inflammatory response pathway,UPLC was taken to measure the exact medicinal substance of ethyl acetate from NE.Sprague Dawley rats were randomly divided into a blank group,a model group,a live-action group,and a positive group.The joint cavity was removed after 21 d.Moreover,a model group,a live group,and a positive group were also set up with RA-FLS cells in our in vitro study.The expressions of P2X3 and PKC inflammation pathway indicators were detected by Western blotting analysis.A P2X3 inhibitor(A-317491)acted on RA-FLS cells,and a model group and a positive group were set.Then the protein expression of PKC was detected.NE reduced the expressions of P2X3,Rab7,PKC,and NF-κB at the protein level in both systems.NE and P2X3 receptor antagonists reduced the expressions of key proteins in the PKC pathway in RA-FLS cells to similar extents,and their effects were not additive.NE could effectively improve the“forelimb pain”of RA rats,with a mechanism closely related to the P2X3/Rab7/PKC/NF-κB pathway.

Potential paleoceanographic application of cold-water bamboo coral in the South China Sea

Recent deep-diving expeditions in the South China Sea(SCS)discovered abundant indigenous cold-water corals[1].Cold-water corals,preferentially inhabiting the low-latitude intermediate and deep waters with hard substrates and a cool water temperature,have great potential to be applied in researches of the ocean interior by providing high-resolution records[2,3].

Experimental investigation of characteristics of instability evolution in a centrifugal compressor

The stable range of operation for the centrifugal compressor significantly influences the dynamic,economic,and environment-friendly characteristics of power systems.A deep understand-ing of the characteristics of instability evolution is necessary to improve the compressor stability.A centrifugal compressor equipped with a vaneless diffuser is experimentally investigated using high-response static-pressure measurements.The results obtained indicate that three typical rotational-speed ranges exist based on the different instability evolution characteristics,which reveals the var-ious impeller–diffuser matching behaviors over the entire speed range.At low-speed ranges((40%–75%)N_(max),N_(max)is the maximum rotational speed),the compressor exhibits stable,Rotating Insta-bility(RI),impeller stall(diffuser stall),and surge modes.The impeller stall mode is induced by RI and propagates downstream,resulting in the diffuser stall and compressor surge modes.In the medium-speed range((75%–85%)N_(max)),the compressor exhibits stable,diffuser stall,RI,and surge modes.In the high-speed range((85%–100%)N_(max)),the compressor exhibits stable,diffuser stall,and surge modes.The dominant instability position is shifted from the impeller to the diffuser as the rotational speed increases.Both the impeller and diffuser stall present an irregular sawtooth static-pressure wave and exhibit broadband frequency spectrum patterns.

高校毕业生“考公热”选择走向成因分析及引导策略——基于布迪厄场域和文化资本理论

近年来,越来越多的高校毕业生将“考公”作为未来就业的首选目标。目前学界对“考公热”的研究主要沿用了传统的“现象-解释”范式,从研究旨趣差异看主要体现为以量化研究为特征的调查研究和实验研究,使得相关研究具有一定的囿限性。本文通过质性研究方法,以网络民族志的观察和对10位高校毕业生的深入访谈,从布迪厄场域和文化资本理论视角探究当前青年“考公”偏好与背后缘由。研究发现,高校毕业生普遍存在“迷失、顺势和取舍”等择业表征,主要受到空间分配的位次差异、文化资本的占有程度不同以及文化资本的产品化等因素的形塑。本文提出引导策略,希冀通过角色引导、场域重构与再造、资本积累与再生产的延续与置换、文化产品再生产的规范化等策略进行纾解。

Wet-chemistry synthesis of cobalt carbide nanoparticles as highly active and stable electrocatalyst for hydrogen evolution reaction

Transition metal carbide （TMC） nanomaterials are promising alternatives to Pt, and are widely used as heterogeneous electrocatalysts for the electrochemical hydrogen evolution reaction （HER）. In this work, a bromide-induced wet-chemistry strategy to synthesize Co2C nanoparticles （NPs） was developed. Such NPs exhibited high electrocatalytic activity （η= 181 mV for j = -10 mA·cm^-2） and long-term stability （no obvious performance decrease after 4,000 cycles） for the HER. This study will pave the way for the design and fabrication of TMC NPs via a wet- chemistry method, and will have significant impacts on broader areas such as nanocatalysis and energy conversion.

High-efficiency 50 W burst-mode hundred picosecond green laser

We report high-energy,high-efficiency second harmonic generation in a near-infrared all-solid-state burst-mode picosecond laser at a repetition rate of 1 kHz with four pulses per burst using a type-I noncritical phase-matching lithium triborate crystal.The pulses in each burst have the same time delay(~1 ns),the same pulse duration(~100 ps)and different relative amplitudes that can be adjusted separately.A mode-locked beam from a semiconductor saturable absorber mirror is pulse-stretched,split into seed pulses and injected into a Nd:YAG regenerative amplifier.After the beam is reshaped by aspheric lenses,a two-stage master oscillator power amplifier and 4f imaging systems are applied to obtain a high power of^100 W.The 532 nm green laser has a maximum conversion efficiency of 68%,an average power of up to 50 W and a beam quality factor M^2 of 3.5.

A loss-of-function mutant allele of a glycosyl hydrolase gene has been co-opted for seed weight control during soybean domestication

The resultant DNA from loss-of-function mutation can be recruited in biological evolution and development.Here,we present such a rare and potential case of“to gain by loss”as a neomorphic mutation during soybean domestication for increasing seed weight.Using a population derived from a chromosome segment substitution line of Glycine max(SN14)and Glycine soja(ZYD06),a quantitative trait locus(QTL)of 100-seed weight(q HSW)was mapped on chromosome 11,corresponding to a truncatedβ-1,3-glucosidase(βGlu)gene.The novel gene hsw results from a 14-bp deletion,causing a frameshift mutation and a premature stop codon in theβGlu.In contrast to HSW,the hsw completely lostβGlu activity and function but acquired a novel function to promote cell expansion,thus increasing seed weight.Overexpressing hsw instead of HSW produced large soybean seeds,and surprisingly,truncating hsw via gene editing further increased the seed size.We further found that the core 21-aa peptide of hsw and its variants acted as a promoter of seed size.Transcriptomic variation in these transgenic soybean lines substantiated the integration hsw into cell and seed size control.Moreover,the hsw allele underwent selection and expansion during soybean domestication and improvement.Our work cloned a likely domesticated QTL controlling soybean seed weight,revealed a novel genetic variation and mechanism in soybean domestication,and provided new insight into crop domestication and breeding,and plant evolution.

Click chemistry and drug delivery:A bird's-eye view

Click chemistry has been proven to be very useful in drug delivery.Due to the availability of a large number of click reactions with a various characteristics,selection of appropriate chemistry for a given application is often not a trivial task.This review is written for pharmaceutical researchers who are interested in click chemistry applications and yet may not be click chemistry experts.For this,the review gives an overview of available click reactions organized by application types.Further,the general understanding of click reactions being fast and high yielding sometimes overshadows the need to analyze reaction kinetics in assessing suitability of a given reaction for certain applications.For this,we highlight the need to analyze the relationship among reaction kinetics,concentration effects,and reaction time scales,knowing that lack of such analysis could easily lead to failures.Further,possible issues such as chemical stability with various click reagents are also discussed to aid experimental designs.Recent examples and extensive references are also provided to aid in-depth understanding of technical details.We hope this review will help those interested in using click chemistry in drug delivery to select the appropriate reactions/reagents and minimize the number of pitfalls.

Synthesis of Iron-Carbide Nanoparticles:Identification of the Active Phase and Mechanism of Fe-Based Fischer-Tropsch Synthesis

Despite the extensive study of the Fe-based Fischer-Tropsch synthesis(FTS)over the past 90 years,its active phases and reaction mechanisms are still unclear due to the coexistence of metals,oxides,and carbide phases presented under realistic FTS reaction conditions and the complex reaction network involving CO activation,C-C coupling,and methane formation.To address these issues,we successfully synthesized a range of pure-phase iron and iron-carbide nanoparticles(Fe,Fe_(5)C_(2),Fe_(3)C,and Fe_(7)C_(3))for the first time.By using them as the ideal model catalysts on high-pressure transient experiments,we identified unambiguously that all the iron carbides are catalytically active in the FTS reaction while Fe_(5)C_(2) is the most active yet stable carbide phase,consistent with density functional theory(DFT)calculation results.The reaction mechanism and kinetics of Fe-based FTS were further explored on the basis of those model catalysts by means of transient high-pressure stepwise temperature-programmed surface reaction(STPSR)experiments and DFT calculations.Our work provides new insights into the active phase of iron carbides and corresponding FTS reaction mechanism,which is essential for better iron-based catalyst design for FTS reactions.

Expert knowledge maps for knowledge management: a case study inTraditional Chinese Medicine research

OBJECTIVE:To design a model to capture information on the state and trends of knowledge creation,at both an individual and an organizational level,in order to enhance knowledge management.METHODS:We designed a graph-theoretic knowledge model,the expert knowledge map(EKM),based on literature-based annotation.A case study in the domain of Traditional Chinese Medicine research was used to illustrate the usefulness of the model.RESULTS:The EKM successfully captured various aspects of knowledge and enhanced knowledge management within the case-study organization through the provision of knowledge graphs,expert graphs,and expert-knowledge biography.CONCLUSION:Our model could help to reveal thehot topics,trends,and products of the research done by an organization.It can potentially be used to facilitate knowledge learning,sharing and decision-making among researchers,academicians,students,and administrators of organizations.