The role of cAMP-dependent protein kinase A in the formation of long-term memory in Bactrocera dorsalis

The cAMP-dependent protein kinase A(PKA)signaling pathway has long been considered critical for long-term memory(LTM)formation.Previous studies have mostly focused on the role of PKA signaling in LTM induction by multiple spaced conditioning with less attention to LTM induction by a single conditioning.Here,we conducted behavioral-pharmacology,enzyme immunoassay and RNA interference experiments to study the role of the PKA signaling pathway in LTM formation in the agricultural pest Bactrocera dorsalis,which has a strong memory capacity allowing it to form a two-day memory even from a single conditioning trial.We found that either blocking or activating PKA prior to conditioning pretreatment affected multiple spaced LTM,and conversely,they did not affect LTM formed by single conditioning.This was further confirmed by enzyme-linked immunosorbent assay(ELISA)and silencing of the protein kinase regulatory subunit 2 and catalytic subunit 1.Taken together,these results suggest that activating PKA during memory acquisition helps to induce the LTM formed by multiple spaced conditioning but not by a single conditioning.Our findings challenge the conserved role of PKA signaling in LTM,which provides a basis for the greater diversity of molecular mechanisms underlying LTM formation across species,as well as possible functional and evolutionary implications.

Device design based on the covalent homocouplingof porphine molecules

Porphine has a great potential application in molecular electronic devices.In this work,based on the density functional theory(DFT)and combining with nonequilibrium Green's function(NEGF),we study the transport properties of the molecular devices constructed by the covalent homocoupling of porphine molecules conjunction with zigzag graphene nanoribbons electrodes.We find that different couple phases bring remarkable differences in the transport properties.Different coupling phases have different application prospects.We analyze and discuss the differences in transport properties through the molecular energy spectrum,electrostatic difference potential,local density of states(LDOS),and transmission pathway.The results are of great significance for the design of porphine molecular devices in the future.

Renewable energy investment in China:the impact of low oil prices

The promotion of renewable energy(RE)technology in China has been paramount in the country’s policy to reinforce energy security,reduce air pollution from coal,oil and gas,and tackle climate change.This study examines whether the RE sector in China(primarily solar and wind)might suffer an immediate or long-term backlash as the result of cuts in oil import costs.The demand for oil in China has increased at an astounding rate since the 1980s.In the face of its burgeoning economy and multiplying vehicle fleet,energy security has become a significant preoccupation for policy makers.The rapid fall in oil prices on the international market since June 2014 is likely to improve security of supply and positively impact the nation’s economy.However,the fate of another energy sector,RE technology is less predictable.The article proposes a quantitative model to compare oil demand and prices over recent years with the impact on investment in RE,taking into account that the main competitor of RE is coal rather than oil.How energy policy has evolved and adapted over this period is also discussed.It is observed that lower oil prices decrease RE investments but reduce concerns over energy security.But,the strength of the impact depends on the duration of low oil prices and its volatility.The commitment of the government to reduce global CO_(2) emissions may not be overlooked.

Simultaneous enhancement of coercivity and electric resistivity of Nd-Fe-B magnets by Pr-Tb-Al-Cu synergistic grain boundary diffusion toward high-temperature motor rotors

To high-power permanent magnetic motors,it is critical for Nd-Fe-B magnets to maintain the desirable coercivity at high-temperature operating conditions.To address this,two approaches have been proven effective:(1)enhancing the room temperature coercivity;(2)reducing the eddy current loss.However,these two items are difficult to be simultaneously achieved.Here,the grain boundary diffusion(GBD)of the Pr-Tb-Al-Cu-based source is applied to enhance the coercivity and electric resistivity at room temperature from 1101 kA m-1 and 2.13×10–6Ωm to 1917 kA m-1 and 2.60×10–6Ωm,and those at 120°C from 384 kA m-1 and 4.31×10–6Ωm to 783 kA m-1 and 4.86×10–6Ωm,respectively.Such optimization is ascribed to the improved formation depth of Tb-rich 2:14:1 shells with large magnetocrystalline anisotropy and the increased intergranular Pr-based oxides with high electric resistivity,induced by the coordination effects of Tb and Pr,as proven by the atomic-scale observations and the first principles calculations.It thus results in the simultaneously improved output power and energy efficiency of the motor because of the combination of magnetic thermal stability enhancement and eddy current loss reduction,as theoretically confirmed by electromagnetic simulation.

Effects of grain boundary diffusion process on magnetic properties enhancement and microstructure evolution of hot-deformed Nd-Fe-B magnets

Grain boundary diffusion(GBD)process is an important approach for producing Nd-Fe-B magnets with high coercivity and high thermal stability.The GBD for hot-deformed Nd-Fe-B magnets with nanocrystalline micro structure is more complicated compared to sintered magnets.Here,we investigated the effects of different GBD methods,i.e.,intergranular addition(in-situ GBD 1#),in-situ GBD from magnet surface during hot pressing and hot deformation(in-situ GBD 2#),and conventional GBD,on the magnetic properties and microstructure of hot deformed magnets.After the treatment by these three GBD approaches using 2 wt%Pr_(40)Tb_(30)Cu_(30)diffusion source,the coercivity of the hot-deformed magnet increases from 1281 to 1567,1412 and 2022 kA/m,respectively.The coercivity enhancement is attributed to the formation of local(Nd,Tb)2Fe14B phase with stro ng magnetic anisotropy.Reduced grain orientation is found in both in-situ GBD 1#and conventional GBD treated samples mainly due to the local stress state variation and the rotation of platelet grains.Interestingly,the in-situ GBD 2#processed sample has a high orientation at diffusion surface,which may be caused by the modified surface state of the magnet by the diffusion source.Compared with the in-situ GBD processes,the conventional GBD exhibits a higher utilization efficiency of Tb.Since the in-situ GBD is effective to treat thick hot-deformed magnets,further effort should be aimed at enhancing its diffusion efficiency.

Grain boundary construction and properties enhancement for hot deformed(Ce,La,Y)-Fe-B magnet by a two-step diffusion process

The rare earth-iron-boron magnets based on high abundance rare earths(REs)show potential for costeffective permanent magnets but their hard magnetic properties have to be greatly improved.The grain boundary diffusion process(GBDP)is known as an effective way to improve the coercivity of Nd-Fe-B magnets,however,the conventional diffusion method faces a challenge for Ce-based magnets since there is no enough continuous GB layer as the diffusion channel.Here,a two-step(Nd-Cu doping followed by Nd-Cu diffusion)GBDP was introduced for hot deformed(Ce,La,Y)-Fe-B magnet,and the excellent magnetic properties ofμ0Hc=0.63 T,μ0Mr=0.68 T,and(BH)max=72.4 kJ/m^(3)were achieved.The Nd-Cu doping helps the formation of RE-rich GB layer,and then it acts as the diffusion channel for increasing the ef-ficiency of the subsequent Nd-Cu diffusion and results in the increased volume fraction of continuously distributed GB phase,whose paramagnetism was verified by 57Fe Mössbauer spectrometry.Those paramagnetic GB phases help to form the discontinuous domain walls,as observed by Lorentz transmission electron microscopy,and break the magnetic exchange coupling of RE2Fe14B grains.It thus contributes to the coercivity enhancement of the hot deformed magnet with two-step diffusion,which is further proved by micromagnetic simulation.This study proposes a potential technique to prepare anisotropic hot deformed(Ce,La,Y)-Fe-B magnet with high cost-performance.

Phase precipitation and magnetic properties of melt-spun ternary Gd_(2)Fe_(14)B alloy and advantages of gadolinium substitution in Y_(2)Fe_(14)B alloy

To take the advantage of gadolinium(Gd) in developing and manufacturing RE-permanent magnets,the magnetic properties and phase precipitation behavior of Gd_(2)Fe_(14)B alloys prepared by melt spinning were investigated in this work.The results show that optimally direct quenched nanocrystalline Gd_(2)Fe_(14)B alloy exhibits the magnetic properties with remanence J_(r) of 0.51 T,coercivity H_(c) of 187 kA/m,and maximum energy product(BH)_(max) of 33.1 kJ/m^(3).It also shows excellent thermal stability with a small negative temperature coefficient of J_(r)(α=-0.066%/K) and a positive temperature coefficient of H_(c)(β=0.171 %/K).The phase precipitations of as spun Gd_(2)Fe_(14)B alloy during melt spinning and over-quenched amorphous Gd_(2)Fe_(14)B alloy during heat treatment were clarified.The magnetic properties of the crystallized alloys annealed at 800℃ are close to those of the optimized directly quenched as-spun alloys,indicating good performance stability under various processes.In addition,the role of Gd substitution in(Y_(1-x)Gd_(x))_(2)Fe_(14)B alloys was systematically studied.Gd substitution can significantly enhance the thermal stability and decrease the irreve rsible remanence loss of Y_(2)Fe_(14)B alloy.With increasing Gd conte nt,Gd-doped Y_(2)Fe_(14)B alloys show continuous enhancement of H_(c) at elevated temperatures.The highest β value of 0.22%/K was obtained in(Y_(0.2)Gd_(0.8))_(2)Fe_(14)B alloy at 300—400 K.Gd substitution is not only effective in improving the exchange coupling effect and corrosion resistance of Y_(2)Fe_(14)B alloy but also superior to Nd in terms of improving the oxidation resistance.The present work has certain instructions for designing and developing new low cost RE permanent magnets with improved thermal and environment stability.

Development of non-rare earth grain boundary modification techniques for Nd-Fe-B permanent magnets

The magnetic performance of Nd-Fe-B magnets depends on their grain boundary structure.Intergranular addition and grain boundary diffusion(GBD)process are effective approaches for enhancing coercivity with low material cost.This review summarizes the development of grain boundary modification techniques with emphasis on our recent work using cost-effective non-rare earth(non-RE)sources for GBD.Up to now,heavy rare earth(HRE)based compounds,metals and light rare earth(LRE)based alloys have been successfully employed as the diffusion sources for coercivity enhancement.Inspired from the previous investigations on the intergranular addition of non-RE compounds and alloys for Nd-Fe-B magnets,in 2015,we firstly proposed a novel GBD process based on diffusion source of Mg O.After that,various non-RE diffusion sources have been developed.The fundamentals of non-RE additives and non-RE diffusion sources for hard magnetic properties enhancement of Nd-Fe-B magnets are summarized here based on both the experimental and computational results.In particular,the properties-microstructure relationships of non-RE GBD modified magnets are discussed.The non-RE alloys or compounds modify the composition and structure of the grain boundary by diffusing into the intergranular regions,resulting in enhanced coercivity and corrosion resistance.Recently,we used Al-Cr coatings for both coercivity enhancement and surface protection,which shortens the production process and makes non-RE diffusion sources more competitive.The opportunity and future directions for non-RE GBD are also discussed in this review.

Observations and computations of narrow Kelvin ship wakes

Computations of far-field ship waves,based on linear potential flow theory and the Hogner approximation,are reported for monohull ships and catamarans.Specifically,far-field ship waves are computed for six monohull ships at four Froude numbers F≡V/√gL=0.58,0.68,0.86,1.58 and for six catamarans with nondimensional hull spacing s≡S/L=0.25 at two Froude numbers F s≡V/√gS=1 and 2.5.Here,g is the gravitational acceleration,V and L denote the ship speed and length,and S is the separation distance between the twin hulls of a catamaran.The computations show that,although the amplitudes of the waves created by a ship are strongly influenced by the shape of the ship hull,as well known,the ray angles where the largest waves are found are only weakly influenced by the hull shape and indeed are mostly a kinematic feature of the flow around a ship hull.An important practical consequence of this flow feature is that the apparent wake angle of general monohull ships or catamarans(with arbitrarily-shaped hulls)can be estimated,without computations,by means of simple analytical relations;these relations,obtained elsewhere via parametric computations,are given here.Moreover,the influence of the two parameters F s and s that largely determine the ray angles of the dominant waves created by a catamaran is illustrated via computations for three catamarans with hull spacings s=0.2,0.35,0.5 at four Froude numbers F s=1,1.5,2,2.5.These computations confirm that the largest waves created by wide and/or fast catamarans are found at ray angles that only depend on F s(i.e.that do not depend on the hull spacing s)in agreement with an elementary analysis of lateral interference between the dominant waves created by the bows(or sterns)of the twin hulls of a catamaran.The dominant-waves ray angles predicted by the theory of wave-interference effects for monohull ships and catamarans are also compared with the observations of narrow Kelvin ship wakes reported by Rabaud and Moisy,and found to be consistent with these observations.

Development of cost-effective nanocrystalline multi-component(Ce,La,Y)-Fe-B permanent magnetic alloys containing no critical rare earth elements of Dy,Tb,Pr and Nd

Here we first report the fully abundant rare earth(RE)-based nanocrystalline multi-component(Ce,La,Y)-Fe-B alloys containing no critical RE elements of Nd,Pr,Dy,and Tb by melt-spinning technique.The roles of La and Y substitutions for Ce have been fully understood.La plays a positive role on both thermal stability and room-temperature(RT)magnetic properties.The enhanced coercivity H_(cj)by partial substitution of La is attributed to the increases of anisotropy field H_A and the formation of continuously distributed grain boundaries resulting from the suppre s sion of CeFe_(2)phase.Although Y substitution is not benefit for H_(cj),both remanent polarization J_r and thermal stability have been effectively improved since Y_(2)Fe_(14)B shows relatively high saturation magnetization M_s and a positive temperature coefficient of HA over a certain temperature range.In addition,RE element segregation has been confirmed,La prefers to enter into the grain boundaries than Ce and Y prefers to remain in the 2:14:1 phase.Based on these understanding,a series of melt-spun(Ce,La,Y)-Fe-B alloys have been designed.A relatively good combination of magnetic properties with maximum energy product(BH)_(max)=7.4 MGOe,H_(Cj)=400 kA/m,and J_r=0.63 T has been obtained in[(Ce_(0.8)La_(0.2))_(0.7)Y_(0.3)]_(17)Fe_(78)B_6 alloy,together with high Curie temperature(T_c=488 K)and low temperature coefficients of remanence(α=-0.255%/K)and coercivity(β=-0.246%/K).