Convenient design of anti-wetting nano-Al/WO_(3)metastable intermolecular composites(MICs)with an enhanced exothermic life-span

For solving the dilemma of the short exothermic life-span of WO_(3)based metastable interstitial composites(MICs)with extensive application prospect,this paper has firstly designed the promising antiwetting Al/WO_(3)MICs via electrophoresis assembly of nano-Al and WO_(3)particles fabricated by hydrothermal synthesis method,followed by the subsequent fluorination treatment.A combination of X ray diffraction(XRD),field emission scanning electron microscope(FESEM),energy dispersive X-ray spectroscopy(EDX),and Fourier transform infrared spectroscopy(FT-IR)techniques were utilized in order to characterize the crystal structure,microstructure,and elemental composition distribution of target films after different natural exposure tests.The product with uniform distribution and high purity possesses a high contact angle of~170°and a minute sliding angle of~1°,and displays the outstanding anti-wetting property using droplets with different surface tensions.It also shows great moisture stability in high relative-humidity circumstances after one year of the natural exposure experiment.Notably,the heat output of a fresh sample can reach up to 2.3 kJ/g and retain 96%after the whole exposure test,showing outstanding thermo-stability for at least one year.This work further proposed the mechanism of antiwetting Al/WO_(3)MICs considering the variation tendency of their DSC curve,providing a valuable theoretical reference for designing other self-protected MICs with a long exothermic life-span applied in wide fields of national defense,military industry,etc.

客家山歌传播场域的社会学阐释

文章以宏观社会学的视角,按照场域中不同“位置”所拥有的资本力量差异,将当下客家山歌传播场域分为三种类型:其一,原生态传播场多是老人们在公园广场“唱着古老的歌谣”,自得其乐;其二,舞台态传播场由于“国家在场”,比赛、展演逐渐常态化,“新客家山歌”不断涌现,但有争议;其三,网络态传播场突破时空限制,“微信对歌”成为客家山歌在民间传播的独特方式,客家山歌获得“新生命”。以微观社会学的视角来分析,舞台态传播场中“管理者”处于主导地位,原生态传播场和网络形态传播场中“生产者”处于主导地位,并有向舞台态传播场转化的趋势,会导致客家山歌艺术特征的“同质化”,不利于文化多样性的保护。

Stiffness and toughness of soft/stiff suture joints in biological composites

Biological composites can overcome the conflict between strength and toughness to achieve unprecedented mechanical properties in engineering materials.The suture joint,as a kind of heterogeneous architecture widely existing in biological tissues,is crucial to connect dissimilar components and to attain a tradeoff of all-sided functional performances.Therefore,the suture joints have attracted many researchers to theoretically investigate their mechanical response.However,most of the previous models focus on the sutural interface between two chemically similar stiff phases with(or without)a thin adhesive layer,which are under the framework of linear elasticity and small deformation.Here,a general model based on the finite deformation framework is proposed to explore the stiffness and toughness of chemically dissimilar suture joints connecting soft and stiff phases.Uniaxial tension tests are conducted to investigate the tensile response of the suture joints,and finite element simulations are implemented to explore the underlying mechanisms,considering both material nonlinearity and cohesive properties of the interface.Two failure modes are quantitively captured by our model.The stored elastic energy in the soft phase competes with the energy dissipation due to the interface debonding,which controls the transition among different failure modes.The toughness of the suture joints depends on not only the intrinsic strengths of the constituent materials and their cohesive strength,but also the interfacial geometry.This work provides the structureproperty relationships of the soft/stiff suture joints and gives a foundational guidance of mechanical design towards high-performance bioinspired composites.

Intra-seasonal variability of the abyssal currents in COMRA's contract area in the Clarion-Clipperton Zone

In this paper,the intra-seasonal variability of the abyssal currents in the China Ocean Mineral Resources Association(COMRA)polymetallic nodule contact area,located in the western part of the Clarion and Clipperton Fraction Zone in the tropical East Pacific,is investigated using direct observations from subsurface mooring instruments as well as sea-surface height data and reanalysis products.Mooring observations were conducted from September 13,2017 to August 15,2018 in the COMRA contact area(10°N,154°W).The results were as follows:(1)At depths below 200 m,the kinetic energy of intra-seasonal variability(20-100 d)accounts for more than 40%of the overall low-frequency variability,while the ratio reaches more than 50%below 2000 m.(2)At depths below 200 m,currents show a synchronous oscillation with a characteristic time scale of 30 d,lasting from October to the following January;the energy of the 30-d oscillation increases with depth until the layer of approximately 4616 m,and the maximum velocity is approximately 10 cm/s.(3)The 30-d oscillation of deep currents is correlated with the tropical instability waves in the upper ocean.

Evaluation of reanalysis surface wind products with quality-assured buoy wind measurements along the north coast of the South China Sea

Three archived reanalysis wind vectors at 10 m height in the wind speed range of 2-15 m/s,namely,the second version of the National Centres for Environmental Prediction(NCEP)Climate Forecast System Reanalysis(CFSv2),European Centre for Medium-Range Weather Forecasting Interim Reanalysis(ERA-I)and NCEPDepartment of Energy(DOE)Reanalysis 2(NCEP-2)products,are evaluated by a comparison with the winds measured by moored buoys in coastal regions of the South China Sea(SCS).The buoy data are first quality controlled by extensive techniques that help eliminate degraded measurements.The evaluation results reveal that the CFSv2 wind vectors are most consistent with the buoy winds(with average biases of 0.01 m/s and 1.76°).The ERA-I winds significantly underestimate the buoy wind speed(with an average bias of-1.57 m/s),while the statistical errors in the NCEP-2 wind direction have the largest magnitude.The diagnosis of the reanalysis wind errors shows the residuals of all three reanalysis wind speeds(reanalysis-buoy)decrease with increasing buoy wind speed,suggesting a narrower wind speed range than that of the observations.Moreover,wind direction errors are examined to depend on the magnitude of the wind speed and the wind speed biases.In general,the evaluation of three reanalysis wind products demonstrates that CFSv2 wind vectors are the closest to the winds along the north coast of the SCS and are sufficiently accurate to be used in numerical models.

Laser-induced porous graphene on Polyimide/PDMS composites andits kirigami-inspired strain sensor

The laser-induced porous graphene(LIG)prepared in a straightforward fabrication method is presented,and its applications in stretchable strain sensors to detect the applied strain are also explored.The LIGformed on the polyimide/polydimethylsiloxane(PI/PDMS)composite exhibits a naturally high stretchabil-ity(over 30%),bypassing the transfer printing process compared to the one prepared by laser scribing onPI films.The PI/PDMS composite with LIG shows tunable mechanical and electronic performances withdifferent PI particle concentrations in PDMS.The good cyclic stability and almost linear response of theprepared LIG’s resistance with respect to tensile strain provide its access to wearable electronics.To im-prove the PDMS/PI composite stretchability,we designed and optimized a kirigami-inspired strain sensorwith LIG on the top surface,dramatically increasing the maximum strain value that in linear response toapplied strain from 3%to 79%.

Observation and simulation of the diffuse attenuation coefficient of downwelling irradiance in the Polar Ocean

The three-stream radiation transfer model is used to investigate the fluctuation in the underwater diffuse attenuation coefficient of downwelling irradiance in the polar ocean with a high solar zenith angle and different direct radiation proportions.First,the applicability of the three-stream radiation model in the polar region is validated by using 18 in situ observation data from September to October 2009 in the Beaufort Sea.Statistics show that in the absence of sea ice,the average relative errors between the simulation and observation values for 490 nm downwelling irradiance (E_(d)(490)) and its diffuse attenuation coefficient (K_(d)(490)) are 7.04%and 9.88%,respectively.At the stations surrounded by sea ice,the radiation is relatively small due to ice blocking,and the average relative errors simulated by the model reach 15.89%and 15.55%,respectively.Second,simulations with different chlorophyll concentrations and different proportions of direct radiation reveal that a high solar zenith angle has a greater impact on K_(d)(490) in the surface water.K_(d)(490) is less affected by the light field (affected by the solar zenith angle and the proportion of direct radiation) at depths greater than 30 m,and meets the linear relationship with the inherent optical parameters(the sum of the absorption coefficient and backscattering coefficient).The surface K_(d)(490) is still consistent with that at a depth of more than 50 meters under a high solar zenith angle,implying that the surface K_(d)(490) can also be considered as an inherent optical parameter at a high solar zenith angle (greater than 60 degrees).The relative error of obtaining surface K_(d)(490) by using the linear relationship at the 50 m layer is found to be less than 8%in the seawater with chlorophyll concentration greater than0.05 mg m^(-3).The effect of the solar zenith angle and proportion of direct radiation can be ignored when measuring the diffuse attenuation coefficient in the polar region.Finally,the model can correct the ice-induced fluctuation in downward irradiance,allowing for optical research of seawater beneath the ice in the polar ocean.

Tempering mechanism of lath martensite induced in IF steel under high pressure

In this paper,low-and high-strength lath martensite(350 and 640 HV)was fabricated in an IF steel via high pressure martensitic transformation.The microstructure and the softening during their tempering from 200°C to 800°C for 1 h were systematically investigated.A carbon-irrelevant tempering process was proposed,exhibiting a three-stage structural evolution pattern depending upon the tempering de-gree(1-(HV-HV FP)/(HV NP-HV FP),where the HV is the instant hardness,HV NP is the non-tempered hard-ness and HV FP is the fully tempered hardness):(1)low tempered(<10%),removing the loose dislocations and dislocation boundaries within martensitic variants;(2)medium tempered(10%-50%),eliminating the martensitic variant laths via the migration of their terminal tips;(3)highly tempered(>50%),clearing up the remained variant laths via the migration of the triple junctions.Martensite-type microstructure is tailored by low-index lamellar variant boundaries and is thus intrinsically thermally stable,whereas the mobile terminal tips decrease the tempering resistance.The underlying mechanism for such carbon-irrelevant process was discussed and the potential effect on the tempering behavior of carbon-contained martensite was highlighted.

Subtidal variability in the Taiwan Strait induced by combined forcing of winter monsoon and topography

As an important channel connecting the East and South China Seas, circulations in the Taiwan Strait are strongly influenced by the East Asian monsoon and the topography of the strait, especially the Taiwan Bank(TWB), which is a remarkable topographic feature located at the southern entrance to the strait. Based on a series of pressure gauges deployed roughly 40 km offshore along the western Strait, subtidal sea-level variability under the combined impact of winter monsoon and topography was studied. The analyses show significant along-strait coherences of subtidal sea levels and their coherences with the large-scale monsoon wind for periods from 2 to 14 days. It is suggested that these fluctuations are mainly forced waves driven by the large-scale winds. In addition to the normal cross-shore wind setup, a sea-level setup in the along-strait direction is confirmed, which is induced by the combined forcing of the fluctuating winter monsoon and the blocking of the TWB. A southward current surge driven by a northerly wind event will cause a rising sea level over the TWB inducing a southward alongshore slope anomaly to the north of the TWB and a reversed slope anomaly to the south The subtidal current through the channel to the west of the TWB is found to be influenced by the reversed slope anomalies generated via the along-shore setup.

Reprogrammable 3D Mesostructures Through Compressive Buckling of Thin Films with Prestrained Shape Memory Polymer

The mechanically guided assembly that relies on the compressive buckling of strate- gically patterned 2D thin films represents a robust route to complex 3D mesostructures in advanced materials and even functional micro-devices. Based on this approach, formation of complex 3D configurations with suspended curvy features or hierarchical geometries remains a challenge. In this paper, we incorporate the prestrained shape memory polymer in the 2D precur- sor design to enable local rolling deformations after the mechanical assembly through compressive buckling. A theoretical model captures quantitatively the effect of key design parameters on local rolling deformations. The combination of precisely controlled global buckling and local rolling expands substantially the range of accessible 3D configurations. The combined experimental and theoretical studies over a dozen of examples demonstrate the utility of the proposed strategy in achieving complex reprogrammable 3D mesostructures.

Controlled mechanical assembly of complex 3D mesostructures and strain sensors by tensile buckling

Recent research establishes methods of controlled mechanical assembly as versatile routes to three-dimensional(3D)mesostructures from patterned 2D films,with demonstrated applicability to a broad range of materials(e.g.,semiconductors,polymers,metals,and their combinations)and length scales(e.g.,from sub-microscale to centimeter scale).Previously reported schemes use pre-stretched elastomeric substrates as assembly platforms to induce compressive buckling of 2D precursor structures,thereby enabling their controlled transformation into 3D architectures.Here,we introduce tensile buckling as a different,complementary strategy that bypasses the need for a pre-stretched platform,thereby simplifying the assembly process and opening routes to additional classes of 3D geometries unobtainable with compressive buckling.A few basic principles in mechanics serve as guidelines for the design of 2D precursor structures that achieve large out-of-plane motions and associated 3D transformations due to tensile buckling.Experimental and computational studies of nearly 20 examples demonstrate the utility of this approach in the assembly of complex 3D mesostructures with characteristic dimensions from micron to millimeter scales.The results also establish the use of nonlinear mechanics modeling as a mechanism for designing systems that yield desired 3D geometries.A strain sensor that offers visible readout and large detectable strain range through a collection of mechanically triggered electrical switches and LEDs serves as an application example.

Tunable seesaw-like 3D capacitive sensor for force and acceleration sensing

To address the resource-competing issue between high sensitivity and wide working range for a stand-alone sensor,development of capacitive sensors with an adjustable gap between two electrodes has been of growing interest.While several approaches have been developed to fabricate tunable capacitive sensors,it remains challenging to achieve,simultaneously,a broad range of tunable sensitivity and working range in a single device.In this work,a 3D capacitive sensor with a seesaw-like shape is designed and fabricated by the controlled compressive buckling assembly,which leverages the mechanically tunable configuration to achieve high-precision force sensing(resolution~5.22 nN)and unprecedented adjustment range(by~33 times)of sensitivity.The mechanical tests under different loading conditions demonstrate the stability and reliability of capacitive sensors.Incorporation of an asymmetric seesaw-like structure design in the capacitive sensor allows the acceleration measurement with a tunable sensitivity.These results suggest simple and low-cost routes to high-performance,tunable 3D capacitive sensors,with diverse potential applications in wearable electronics and biomedical devices.

Generation of knockout rabbits using transcription activator-like effector nucleases

Zinc-finger nucleases and transcription activator-like effector nucleases are novel gene-editing platformscontributing to redefine the boundaries of modern biological research. They are composed of a non-specificcleavage domain and a tailor made DNA-binding module, which enables a broad range of genetic modifications byinducing efficient DNA double-strand breaks at desired loci. Among other remarkable uses, these nucleases havebeen employed to produce gene knockouts in mid-size and large animals, such as rabbits and pigs, respectively.This approach is cost effective, relatively quick, and can produce invaluable models for human disease studies,biotechnology or agricultural purposes. Here we describe a protocol for the efficient generation of knockout rabbitsusing transcription activator-like effector nucleases, and a perspective of the field.

A soft and stretchable electronics using laser-induced graphene on polyimide/PDMS composite substrate

The one-step fabricated laser-induced graphene(LIG)has the advantages of low cost,patterning of various desired geometries,and high sensitivity.However,the robustness of substrates imposes certain constraints on their applications in stretchable devices.In this paper,the substrate composed of polydimethylsiloxane(PDMS)and polyimide(PI)particles is proposed to serve as the platform to manufacture LIG.Ascribing to the inherent soft and stretchable attributes of the PI/PDMS composite substrate,the LIG based sensors can fit complex 3D configurations or bear a mechanical tension over 15%.Notably,the fluence of the laser is experimentally and theoretically determined as the only principle to characterize the formation of conductive LIG on PI/PDMS composite greatly facilitating the selection of the allowable laser scanning parameters to form the desired LIG-based devices.Three demonstrations are conducted to highlight the superiority and the potential of this soft and stretchable LIG-based system in wearable electronics and soft robots.

热膨胀系数可控二维双金属点阵结构

热膨胀系数可控的力学超结构,有望显著提高极端热环境下电子器件和光学设备的尺寸稳定性和指向精度.前期针对热膨胀可控力学超结构的设计理论和性能评价方法已开展了大量研究,但如何实现近各向同性可控热膨胀变形和结构高承载特性仍面临诸多挑战.本文提出一种双金属点阵超结构,宏观等效热膨胀系数调控范围为75 ppm/K-−45 ppm/K,宏观等效模量达到80 MPa,建立了考虑双金属材料真实连接边界条件的理论预示模型,可准确预测几何构型与材料组元对结构热变形的影响规律,并通过实验验证了几类典型铝、钛、因瓦合金双金属点阵超结构的可控热变形行为,与传统工程材料相比其性能更加优越.

Globular adiponectin-mediated vascular remodeling by affecting the secretion of adventitial-derived tumor necrosis factor-αinduced by urotensinⅡ

Objectives:In this study,we explored how adiponectin mediated urotensinⅡ(UⅡ)-induced tumor necrosis factor-α(TNF-α)andα-smooth muscle actin(α-SMA)expression and ensuing intracellular signaling pathways in adventitial fibroblasts(AFs).Methods:Growth-arrested AFs and rat tunica adventitia of vessels were incubated with UⅡand inhibitors of signal transduction pathways for 1-24 h.The cells were then harvested for TNF-αreceptor(TNF-α-R)messenger RNA(mRNA)and TNF-αprotein expression determination by reverse transcription-polymerase chain reaction(RT-PCR)and enzyme-linked immunosorbent assay(ELISA),respectively.Adiponectin and adiponectin receptor(adipoR)expression was measured by RT-PCR,quantitative real-time PCR(qPCR),immunohistochemical analysis,and cell counting kit-8(CCK-8)cell proliferation experiments.We then quantified TNF-αandα-SMA mRNA and protein expression levels by qPCR and immunofluorescence(IF)staining.RNA interference(RNAi)was used to explore the function of the adipoR genes.To investigate the signaling pathway,we applied western blotting(WB)to examine phosphorylation of adenosine 5’-monophosphate(AMP)-activated protein kinase(AMPK).In vivo,an adiponectin(APN)-knockout(APN-KO)mouse model mimicking adventitial inflammation was generated to measure TNF-αandα-SMA expression by application of qPCR and IF,with the goal of gaining a comprehensive atlas of adiponectin in vascular remodeling.Results:In both cells and tissues,UⅡpromoted TNF-αprotein and TNF-α-R secretion in a dose-and time-dependent manner via Rho/protein kinase C(PKC)pathway.We detected marked expression of adipoR1,T-cadherin,and calreticulin as well as a moderate presence of adipoR2 in AFs,while no adiponectin was observed.Globular adiponectin(gAd)fostered the growth of AFs,and acted in concert with UⅡto induceα-SMA and TNF-αthrough the adipoR1/T-cadherin/calreticulin/AMPK pathway.In AFs,gAd and UⅡsynergistically induced AMPK phosphorylation.In the adventitial inflammation model,APN deficiency up-regulated the expression ofα-SMA,UⅡreceptor(UT),and UⅡwhile inhibiting TNF-αexpression.Conclusions:From the results of our study,we can speculate that UⅡinduces TNF-αprotein and TNF-α-R secretion in AFs and rat tunica adventitia of vessels via the Rho and PKC signal transduction pathways.Thus,it is plausible that adiponectin is a major player in adventitial progression and could serve as a novel therapeutic target for cardiovascular disease administration.

The stretchable carbon black-based strain fiber with a remarkable linearity in a wide sensing range

Ascribed to its wide sensing range,high sensitivity,and low stiff-ness to match target objects with complex 3D shapes,the stretch-able strain sensor has shown its promising applications in various fields,ranging from healthcare,bodynet,and intelligent traffic system,to the robotic system.This paper presents a low-cost and straightforward fabrication technology for the stretchable strain fiber with the combined attributes of a wide sensing range,excep-tional linearity,and high durability.The hybrid composite consist-ing of carbon black and silicone is utilized as the functional material to respond to the external mechanical deformation due to the piezoresistive effect.To address the remarkable hysteresis of the CB-silicone composites,the latex tubes with excellent mechanical robustness and a considerable accessible tensile strain are intro-duced as the outer supporting components.After injecting the conductive CB-silicone composite into these tubes,the stretchable strain fibers are successfully prepared.Notably,the stretchable strain sensor exhibits linearity(R^(2)=0.9854)in a wide sensing range(0-400%)and remarkable durability even after the 2500 cycles under 100%tension.Additionally,the potential of this stretchable strain fiber as the wearable strain sensor and the realtime feedback is demonstrated by detecting the body motion and the expansion devices.