Artificial nest boxes are placed to attract birds to nest and breed in a specific location,and they are widely used in avian ecology research and in the attraction of insectivorous birds.There is evidence that artific...Artificial nest boxes are placed to attract birds to nest and breed in a specific location,and they are widely used in avian ecology research and in the attraction of insectivorous birds.There is evidence that artificial nest boxes can adversely affect breeding fitness but no great focus has been placed on this issue by researchers.Therefore,we retrieved 321 research papers regarding artificial nest boxes published from 2003 to 2022 and used the'Biblioshiny'program to extract and integrate keywords;we then summarized the adverse effects of artificial nest boxes on avian breeding success.The studies highlighted many drawbacks and misuses in the designing and placement of nest boxes;furthermore,bird attraction was decreased by their inappropriate selection,thus reducing breeding success.Regarding nest box production,there were shortcomings in the construction material,color,smell,and structural design of the boxes used.Nest boxes were also placed at inappropriate densities,locations,orientations,heights,and managed incorrectly.Finally,we propose suggestions for more efficient and safer artificial nest boxes for future use in avian ecology research and bird conservation.展开更多
This paper summarizes the negative effects on geological environment caused by groundwater exploitation and its distribution. There are seven main types of the geological environment negative effects, which are genera...This paper summarizes the negative effects on geological environment caused by groundwater exploitation and its distribution. There are seven main types of the geological environment negative effects, which are generally as follows:(1) Constant decrease of groundwater level is mainly distributed in China(East Asia), India(South Asia), Tajikistan(Central Asia) and Saudi Arabia(West Asia);(2) land subsidence occurs mainly in eastern plains of East Asia and west Siberian Plain of North Asia;(3) seawater intrusion occurs mainly in China, Japan and South Korea in East Asia, Philippines and Indonesia in Southeast Asia, the Indian coastal areas in South Asia;(4) groundwater level decline caused by groundwater exploitation in oil fields;(5) mining collapse is mainly in 50° to 70° north latitude band;(6) the total area of karst collapse in China of East Asia is as much as 197.05 km^2; and(7) ground fracture is mainly distributed in the North China Plain, Fenwei Plain and the Yangtze River Delta. Asia can be divided into 6 zones in terms of the geological environment negative effect caused by groundwater exploitation. According to analysis, with the increasing intensity of human activities, geological environment issues become more and more serious, therefore it is vital to control the human activities within the scope of 5× 10~5 people/km^2 to 9.9× 10~5 people/km^2 for the effective control of the size of the affected area by geological environment problems.展开更多
This paper attempts to investigate the negative effects of the spread of COVID-19 on low-income families in Egypt.Coronavirus spread is measured by"Coronavirus cases"and"Coronavirus deaths"on a dai...This paper attempts to investigate the negative effects of the spread of COVID-19 on low-income families in Egypt.Coronavirus spread is measured by"Coronavirus cases"and"Coronavirus deaths"on a daily basis.Besides,it is measured by both"new Coronavirus cases"and"new deaths from Coronavirus",in relation to the population of Egypt.The Egyptian government is taking some measures to reduce the negative effects of COVID-19,including increasing personal exemptions by amending some provisions of the Egyptian Income Tax Law promulgated by Law No.91 of 2005 to protect low-income families.Of the negative effects of COVID-19,it is one of the most important tax policies to achieve social justice in distributing the tax burden,according to income levels,in a manner that achieves justice and equality.We find that Personal exemptions did not succeed in achieving tax justice by easing the tax burden on the low-income people in society.展开更多
deployment of the THAAD system in South Korea imposed by the United States is superficially and nominally to target at the DPRK's nuclear and missile threats,but essentially to respond to the rising China and Russ...deployment of the THAAD system in South Korea imposed by the United States is superficially and nominally to target at the DPRK's nuclear and missile threats,but essentially to respond to the rising China and Russia,is further tied South Korea to the U.S.war chariot and is a dose of poison undermining the Northeast Asian environment for the mutual benefit,mutual trust and win-win cooperation as well as development and stability.展开更多
The anti-resonant phenomenon of effective electromagnetic parameters of metamaterials has aroused controversy due to negative imaginary permittivity or permeability. It is experimentally found that the negative imagin...The anti-resonant phenomenon of effective electromagnetic parameters of metamaterials has aroused controversy due to negative imaginary permittivity or permeability. It is experimentally found that the negative imaginary permittivity can occur for the natural passive materials near the Fabry Perot resonances. We reveal the nature of negative imaginary permittivity, which is correlated with the magnetoelectric coupling. The anti-resonance of permittivity is a non-inherent feature for passive materials, while it can be inherent for devices or metamaterials. Our finding validates that the negative imaginary part of effective permittivity does not contradict the second law of thermodynamics for metamaterials owing to the magnetoelectric coupling.展开更多
As one of the most distinguished features of Chinese Culture,collective oriented culture is the deep structure of Chinese cultural psychology which has shaped Chinese character and influenced their behavior.As a resul...As one of the most distinguished features of Chinese Culture,collective oriented culture is the deep structure of Chinese cultural psychology which has shaped Chinese character and influenced their behavior.As a result of it,Chinese students suffer this negative effect from collective orientated culture when acquiring English,especially in oral English acquisition.TEFL teachers should be aware of cultural psychology and try their best to minimize its negative effect instead of neglecting or even enlarging it during oral English teaching.展开更多
A negative capacitance(NC)effect has been proposed as a critical pathway to overcome the‘Boltzmann tyranny’of electrons,achieve the steep slope operation of transistors and reduce the power dissipation of current se...A negative capacitance(NC)effect has been proposed as a critical pathway to overcome the‘Boltzmann tyranny’of electrons,achieve the steep slope operation of transistors and reduce the power dissipation of current semiconductor devices.In particular,the ferroic property in hafnium-based films with fluorite structure provides an opportunity for the application of the NC effect in electronic devices.However,to date,only a transient NC effect has been confirmed in hafnium-based ferroic materials,which is usually accompanied by hysteresis and is detrimental to low-power transistor operations.The stabilized NC effect enables hysteresis-free and low-power transistors but is difficult to observe and demonstrate in hafnium-based films.This difficulty is closely related to the polycrystalline and multi-phase structure of hafnium-based films fabricated by atomic layer deposition or chemical solution deposition.Here,we prepare epitaxial ferroelectric Hf_(0.5)Zr_(0.5)O_(2) and antiferroelectric ZrO_(2) films with single-phase structure and observe the capacitance enhancement effect of Hf_(0.5)Zr_(0.5)O_(2)/Al_(2)O_(3) and ZrO_(2)/Al_(2)O_(3) capacitors compared to that of the isolated Al_(2)O_(3) capacitor,verifying the stabilized NC effect.The capacitance of Hf_(0.5)Zr_(0.5)O_(2) and ZrO_(2) is evaluated as−17.41 and−27.64 pF,respectively.The observation of the stabilized NC effect in hafnium-based films sheds light on NC studies and paves the way for low-power transistors.展开更多
Adsorption behaviors of phenol from aqueous solutions have been investigated in batch systems at 303 K and 318 K respectively, using hypercrosslinked polymeric adsorbent (CHA111), aminated hypercrosslinked polymeric...Adsorption behaviors of phenol from aqueous solutions have been investigated in batch systems at 303 K and 318 K respectively, using hypercrosslinked polymeric adsorbent (CHA111), aminated hypercrosslinked polymeric adsorbents (NDA101, NDA103, NDA105) and weakly basic polymeric adsorbent (D301) with a view to studying the effect of hydrogen bonding and Van der Waals interactions between adsorbate and the adsorbent. All adsorption isotherms can be well fitted by Langmuir and Freundlich equations. Compared with D301 driven by hydrogen bonding interaction only and CHA111 driven by Van der Waals interaction only, phenol adsorption on aminated adsorbents driven by both hydrogen bonding and Van der Waals interactions were apparently different, i.e., negative effect for NDA105, positive effect for NDA101 and synergistic effect for NDA103. In this synergistic action, some weak interactions would contribute more or less to the adsorption than they work individually.展开更多
Tunneling field effect transistors(TFETs) based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low...Tunneling field effect transistors(TFETs) based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low power devices. Here,we investigate the TFETs based on two different integration types: in-plane and vertical heterostructures composed of two kinds of layered phosphorous(β-P and δ-P) by ab initio quantum transport simulations. NDR effects have been observed in both in-plane and vertical heterostructures, and the effects become significant with the highest peak-to-valley ratio(PVR)when the intrinsic region length is near zero. Compared with the in-plane TFET based on β-P and δ-P, better performance with a higher on/off current ratio of - 10-6 and a steeper subthreshold swing(SS) of - 23 mV/dec is achieved in the vertical TFET. Such differences in the NDR effects, on/off current ratio and SS are attributed to the distinct interaction nature of theβ-P and δ-P layers in the in-plane and vertical heterostructures.展开更多
Y^3+-doped (Bi 1/2 Na 1/2) TiO 3-CaTiO 3-BaTiO 3 (BNCBT) positive temperature coefficient of resistivity (PTCR) ceramics sintered in air atmosphere were investigated in this study. (Bi 1/2 Na 1/2) TiO 3 (BNT...Y^3+-doped (Bi 1/2 Na 1/2) TiO 3-CaTiO 3-BaTiO 3 (BNCBT) positive temperature coefficient of resistivity (PTCR) ceramics sintered in air atmosphere were investigated in this study. (Bi 1/2 Na 1/2) TiO 3 (BNT) component can remarkably increase the onset temperature T c of PTCR ceramics with the expense of the resistivity R 25 increase. CaTiO 3 (9–27 mol%) component can decrease the resistivity, and adjust the effects of BNT phase on the T c point. For the sample containing 3 mol% CaTiO 3 , T c raises from 122 ℃ to 153 ℃ when only 0.6 mol% BNT added, while for the ones with higher CaTiO 3 content (9–27 mol%), T c is only increased by a rate of 8–9℃/1.0 mol% BNT. The effects of BNT and CaTiO 3 components on R25/Rmin (negative temperature coefficient effect) are also discussed.展开更多
The single thiolated arylethynylene molecule with 9,10-dihydroanthracene core(denoted as TADHA) possesses pronounced negative differential conductance(NDC) behavior at lower bias regime. The adsorption effects of ...The single thiolated arylethynylene molecule with 9,10-dihydroanthracene core(denoted as TADHA) possesses pronounced negative differential conductance(NDC) behavior at lower bias regime. The adsorption effects of F2 molecule on the current and NDC behavior of TADHA molecular junctions are studied by applying non-equilibrium Green's formalism combined with density functional theory. The numerical results show that the F2 molecule adsorbed on the benzene ring of TADHA molecule near the electrode can dramatically suppresses the current of TADHA molecular junction. When the F2 molecule adsorbed on the conjugated segment of 9,10-dihydroanthracene core of TADHA molecule, an obviously asymmetric effect on the current curves induces the molecular system showing apparent rectifier behavior. However, the current especially the NDC behavior have been significantly enlarged when F2 addition reacted with triple bond of TADHA molecule.展开更多
San-Huang chicken is a high-quality breed in China with yellow feather, claw and break. However, the abnormal phenomenon of the yellow shank turning into green shank of San-Huang chicken has been a concern, as it seri...San-Huang chicken is a high-quality breed in China with yellow feather, claw and break. However, the abnormal phenomenon of the yellow shank turning into green shank of San-Huang chicken has been a concern, as it seriously reduces the carcass quality and economic benefit of yellow-feathered broilers. In this study, the cause of this abnormal green skin in shank was systematically investigated. Physiological anatomy revealed that the abnormal skin in shank was primarily due to the deposition of melanin under the dermis. After analyzing multiple potential causes such as heredity(pedigree and genetic markers), environment(water quality monitoring) and feed composition(mycotoxin detection), excessive aflatoxin B1(AFB1) in feed was screened, accompanied with a higher L-dihydroxy-phenylalanine(L-DOPA)(P<0.05) and melanin content(P<0.01). So it was speculated that excessive AFB1 might be the main cause of abnormal green skin in shank. Subsequently, the further results showed that a high concentration of AFB1(>170 μg kg–1)indeed induced the abnormal green skin in shank compared to the normal AFB1 content(<10 μg kg–1), and the mRNA levels of TYR, TYRP1, MITE, MC1R and EDN3 genes related to melanin deposition would significantly up-regulate(P<0.01) and the content and activity of tyrosinase(TyR) significantly increased(P<0.05). At the same time, the content of L-DOPA and melanin deposition also increased significantly(P<0.01), which also confirmed the effect of excessive AFB1 on melanin deposition in skin of shank. Results of additional experiments revealed that the AFB1's negative effect on melanin deposition in skin of shank could last for a longer time. Taken together, the results of this study explained the occurrence and possible mechanisms of the abnormal AFB1-related green skin in shank of chickens. Excessive AFB1 in diets increased the L-DOPA content and melanin abnormal deposition in the chicken shank possibly via promoting TyR content and activity, and the expression of melanin synthesis-related genes. Furthermore, our findings once again raised the alarm of the danger of AFB1 in the broiler production.展开更多
To clarify the anodic dissolution mechanism of Mg,the hydrogen evolution from pure Mg in acidic solutions under galvanostatic conditions were systematically measured.With increasing anodic current density,the cathodic...To clarify the anodic dissolution mechanism of Mg,the hydrogen evolution from pure Mg in acidic solutions under galvanostatic conditions were systematically measured.With increasing anodic current density,the cathodic hydrogen evolution rate decreased,and the anodic hydrogen evolution became faster while some surface area on the Mg was becoming dark under anodic polarization.Based on the surface analysis results and the generally accepted basic electrochemical equations,the evolution kinetics of hydrogen from Mg was deduced,and the most possible surface intermediate active species that could facilitate the anodic Mg dissolution and anodic hydrogen evolution were proposed.This paper further develops the model of incomplete film Mg^(+) dissolution,explains many reported experimental phenomena,and clarifies misunderstandings of current mechanism.展开更多
Mechanistic understanding of the active intermediates of 2,6-diaminopyridine(DAP) dinitration in the concentrated nitric-sulfuric acid system is of crucial importance for the selectivity control of target product, i.e...Mechanistic understanding of the active intermediates of 2,6-diaminopyridine(DAP) dinitration in the concentrated nitric-sulfuric acid system is of crucial importance for the selectivity control of target product, i.e., 2,6-diamino-3,5-dinitropyridine(DADNP). The active intermediates determining the product selectivity are theoretically studied. The HSO_(4)^(-)-NO_(2)^(+) complex is proposed as the dominant active nitrating intermediate for the first time, which shows low energy barrier(i.e., 10.19 kcal·mol^(-1),1 kcal = 4.186 k J) for direct dinitration of DAP to DADNP. The formed water during the reaction results in not only the formation of less active SO_(4)^(2-)-NO_(2)^(+) complex, but also the occurance of DAP sulfonation(DAP-SO_(3)H intermediate)to facilitate the formation of mononitration byproduct. Meanwhile, the accompanied thermal effects cause the generation of undesirable pyridine-NHNO_(2) intermediate, which is difficult to be rearranged to yield DADNP, inhibiting the reaction and thus giving low DAP conversion. The insights reported here elucidates the importance of thermal effects elimination and water content control, confirmed experimentally in the batch-and micro-reaction systems.展开更多
Nodal-line semimetals have become a research hot-spot due to their novel properties and great potential application in spin electronics. It is more challenging to find 2D nodal-line semimetals that can resist the spin...Nodal-line semimetals have become a research hot-spot due to their novel properties and great potential application in spin electronics. It is more challenging to find 2D nodal-line semimetals that can resist the spin–orbit coupling(SOC)effect. Here, we predict that 2D tetragonal Zn B is a nodal-line semimetal with great transport properties. There are two crossing bands centered on the S point at the Fermi surface without SOC, which are mainly composed of the pxy orbitals of Zn and B atoms and the pz orbitals of the B atom. Therefore, the system presents a nodal line centered on the S point in its Brillouin zone(BZ). And the nodal line is protected by the horizontal mirror symmetry M_(z). We further examine the robustness of a nodal line under biaxial strain by applying up to-4% in-plane compressive strain and 5% tensile strain on the Zn B monolayer, respectively. The transmission along the a direction is significantly stronger than that along the b direction in the conductive channel. The current in the a direction is as high as 26.63 μA at 0.8 V, and that in the b direction reaches 8.68 μA at 0.8 V. It is interesting that the transport characteristics of Zn B show the negative differential resistance(NDR) effect after 0.8 V along the a(b) direction. The results provide an ideal platform for research of fundamental physics of 2D nodal-line fermions and nanoscale spintronics, as well as the design of new quantum devices.展开更多
The so-called 'negative difference effect'(NDE) was often defined by the increasing rate of hydrogen evolution from magnesium(Mg) surface under anodic polarization.In this work,a series of electrochemical test...The so-called 'negative difference effect'(NDE) was often defined by the increasing rate of hydrogen evolution from magnesium(Mg) surface under anodic polarization.In this work,a series of electrochemical tests and microstructure observations were performed to provide an evidence that the NDE of Mg-Li alloys can be retarded by increasing lithium content.Potentiostatic,galvanostatic and potentiodynamic polarization experiments using Mg-xLi(x=4,7.5 and 14 wt%) alloys electrodes indicated that Mg-4 Li alloy maintained the enhancing NDE prior to anodic dissolution as that of conventional Mg alloys.However,the emergence of β-Li phase weakened the NDE of duplex Mg-7.5 Li alloy at a low anodic current density,but it was still enhanced apparently after a high applied anodic value(more than 2 mA/cm^2).The surface observations,including the plane and cross-sectional morphologies,confirmed that the cracked surface film derived from the anodic dissolution resulted in the catalytic activity of NDE for Mg-4 Li and Mg-7.5 Li alloys.Furthermore,the NDE of Mg-14 Li alloy was suppressed obviously after a prior applied anodic polarization,which was attributed to the persistent and integrated surface film which endured a higher level of applied anodic potential and current.展开更多
We measured the anodic hydrogen evolution rates for various applied anodic current densities and estimated the corresponding cathodic hydrogen evolution rates.The estimated cathodic hydrogen evolution rates were less ...We measured the anodic hydrogen evolution rates for various applied anodic current densities and estimated the corresponding cathodic hydrogen evolution rates.The estimated cathodic hydrogen evolution rates were less than the measured anodic hydrogen evolution rates,contradicting the enhanced catalytic activity mechanism of Mg corrosion.In addition,this model was contradicted by the measured apparent Mg valence of 1.2±0.1.In contrast,the uni-positive Mg^(+)mechanism of Mg corrosion was supported by(i)the apparent Mg valence of 1.2±0.1,and(ii)the fact that the measured anodic hydrogen evolution rate increased with increasing weight loss rate.展开更多
Conductive polyvinylidene fluoride(PVDF)matrix composites filled with graphited fiber(GF)or carbon fiber(CF)were prepared by the melt-mixing method.The breakage and length distribution of the fibers in the polym...Conductive polyvinylidene fluoride(PVDF)matrix composites filled with graphited fiber(GF)or carbon fiber(CF)were prepared by the melt-mixing method.The breakage and length distribution of the fibers in the polymer matrix were studied by scanning electron microscope(SEM)and optical microscope(OM)observations,respectively. The differences in the positive temperature coefficient(PTC)effects of the composites were mainly attributed to inter-fiber contact ability.The elimination of the negative temperature coefficient(NTC)effect for CF/PVDF composite was because of an increase in the viscosity of the polymer matrix.With the same filler content,CF could be more effective,to eliminate the NTC effect when compared with GF.Addition of 2%CF(mass fraction)in the PVDF composite with 7%GF(mass fraction)could effectively eliminate the NTC phenomenon of the composite.展开更多
We obtained the output characteristics in wurtzite Al0.15Ga0.85N/GaN MODFETs with the full band Monte Carlo method. The gate length Lg and the channel length Los in the device are 0.2 μm and 0.4 urn, respectively. In...We obtained the output characteristics in wurtzite Al0.15Ga0.85N/GaN MODFETs with the full band Monte Carlo method. The gate length Lg and the channel length Los in the device are 0.2 μm and 0.4 urn, respectively. In the output characteristics we found a differential negative resistance effect. That is, as VDS is a constant, initially, VDS increases with increasing VDS. When VDS exceeds a certain critical value, IDS decreases with increasing VDS. The analysis for velocity-field characteristics in wurtzite CaN, the distributions of the electric field and the electron velocity in the two dimensional electron gas channel indicates that the differential negative resistance effect of the electron average velocity results in the differential negative resistance effect of the output characteristics. The transient transport also is related to the differential negative resistance effect of the output characteristics. This effect only can be observed in the devices with very short channel.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.32170485,31501867)the Fundamental Research Funds for the Central Universities(Grant No.2572022BE02)。
文摘Artificial nest boxes are placed to attract birds to nest and breed in a specific location,and they are widely used in avian ecology research and in the attraction of insectivorous birds.There is evidence that artificial nest boxes can adversely affect breeding fitness but no great focus has been placed on this issue by researchers.Therefore,we retrieved 321 research papers regarding artificial nest boxes published from 2003 to 2022 and used the'Biblioshiny'program to extract and integrate keywords;we then summarized the adverse effects of artificial nest boxes on avian breeding success.The studies highlighted many drawbacks and misuses in the designing and placement of nest boxes;furthermore,bird attraction was decreased by their inappropriate selection,thus reducing breeding success.Regarding nest box production,there were shortcomings in the construction material,color,smell,and structural design of the boxes used.Nest boxes were also placed at inappropriate densities,locations,orientations,heights,and managed incorrectly.Finally,we propose suggestions for more efficient and safer artificial nest boxes for future use in avian ecology research and bird conservation.
基金supported by Geological Map of Groundwater Resources and Environment of China and Surrounding Areas(12120113014200)Series Maps of Karst Environment Geology of China and South East Asia(12120114006401,12120114006301)
文摘This paper summarizes the negative effects on geological environment caused by groundwater exploitation and its distribution. There are seven main types of the geological environment negative effects, which are generally as follows:(1) Constant decrease of groundwater level is mainly distributed in China(East Asia), India(South Asia), Tajikistan(Central Asia) and Saudi Arabia(West Asia);(2) land subsidence occurs mainly in eastern plains of East Asia and west Siberian Plain of North Asia;(3) seawater intrusion occurs mainly in China, Japan and South Korea in East Asia, Philippines and Indonesia in Southeast Asia, the Indian coastal areas in South Asia;(4) groundwater level decline caused by groundwater exploitation in oil fields;(5) mining collapse is mainly in 50° to 70° north latitude band;(6) the total area of karst collapse in China of East Asia is as much as 197.05 km^2; and(7) ground fracture is mainly distributed in the North China Plain, Fenwei Plain and the Yangtze River Delta. Asia can be divided into 6 zones in terms of the geological environment negative effect caused by groundwater exploitation. According to analysis, with the increasing intensity of human activities, geological environment issues become more and more serious, therefore it is vital to control the human activities within the scope of 5× 10~5 people/km^2 to 9.9× 10~5 people/km^2 for the effective control of the size of the affected area by geological environment problems.
文摘This paper attempts to investigate the negative effects of the spread of COVID-19 on low-income families in Egypt.Coronavirus spread is measured by"Coronavirus cases"and"Coronavirus deaths"on a daily basis.Besides,it is measured by both"new Coronavirus cases"and"new deaths from Coronavirus",in relation to the population of Egypt.The Egyptian government is taking some measures to reduce the negative effects of COVID-19,including increasing personal exemptions by amending some provisions of the Egyptian Income Tax Law promulgated by Law No.91 of 2005 to protect low-income families.Of the negative effects of COVID-19,it is one of the most important tax policies to achieve social justice in distributing the tax burden,according to income levels,in a manner that achieves justice and equality.We find that Personal exemptions did not succeed in achieving tax justice by easing the tax burden on the low-income people in society.
文摘deployment of the THAAD system in South Korea imposed by the United States is superficially and nominally to target at the DPRK's nuclear and missile threats,but essentially to respond to the rising China and Russia,is further tied South Korea to the U.S.war chariot and is a dose of poison undermining the Northeast Asian environment for the mutual benefit,mutual trust and win-win cooperation as well as development and stability.
基金Supported by the National Natural Science Foundation of China under Grant No 51102007the Fund for Discipline Construction of Beijing University of Chemical Technology under Grant No XK1702
文摘The anti-resonant phenomenon of effective electromagnetic parameters of metamaterials has aroused controversy due to negative imaginary permittivity or permeability. It is experimentally found that the negative imaginary permittivity can occur for the natural passive materials near the Fabry Perot resonances. We reveal the nature of negative imaginary permittivity, which is correlated with the magnetoelectric coupling. The anti-resonance of permittivity is a non-inherent feature for passive materials, while it can be inherent for devices or metamaterials. Our finding validates that the negative imaginary part of effective permittivity does not contradict the second law of thermodynamics for metamaterials owing to the magnetoelectric coupling.
文摘As one of the most distinguished features of Chinese Culture,collective oriented culture is the deep structure of Chinese cultural psychology which has shaped Chinese character and influenced their behavior.As a result of it,Chinese students suffer this negative effect from collective orientated culture when acquiring English,especially in oral English acquisition.TEFL teachers should be aware of cultural psychology and try their best to minimize its negative effect instead of neglecting or even enlarging it during oral English teaching.
基金The National Key R&D Program of China(Grant No.2021YFB3601301)the National Natural Science Foundation of China(Grant No.52225106 and 12241404)the Natural Science Foundation of Beijing,China(Grant No.JQ20010).
文摘A negative capacitance(NC)effect has been proposed as a critical pathway to overcome the‘Boltzmann tyranny’of electrons,achieve the steep slope operation of transistors and reduce the power dissipation of current semiconductor devices.In particular,the ferroic property in hafnium-based films with fluorite structure provides an opportunity for the application of the NC effect in electronic devices.However,to date,only a transient NC effect has been confirmed in hafnium-based ferroic materials,which is usually accompanied by hysteresis and is detrimental to low-power transistor operations.The stabilized NC effect enables hysteresis-free and low-power transistors but is difficult to observe and demonstrate in hafnium-based films.This difficulty is closely related to the polycrystalline and multi-phase structure of hafnium-based films fabricated by atomic layer deposition or chemical solution deposition.Here,we prepare epitaxial ferroelectric Hf_(0.5)Zr_(0.5)O_(2) and antiferroelectric ZrO_(2) films with single-phase structure and observe the capacitance enhancement effect of Hf_(0.5)Zr_(0.5)O_(2)/Al_(2)O_(3) and ZrO_(2)/Al_(2)O_(3) capacitors compared to that of the isolated Al_(2)O_(3) capacitor,verifying the stabilized NC effect.The capacitance of Hf_(0.5)Zr_(0.5)O_(2) and ZrO_(2) is evaluated as−17.41 and−27.64 pF,respectively.The observation of the stabilized NC effect in hafnium-based films sheds light on NC studies and paves the way for low-power transistors.
基金This study was funded by the National Natural Science Foundation of China(No.20274017)the Natural Science Foundation of Jiangsu Province(No.BK2004415).
文摘Adsorption behaviors of phenol from aqueous solutions have been investigated in batch systems at 303 K and 318 K respectively, using hypercrosslinked polymeric adsorbent (CHA111), aminated hypercrosslinked polymeric adsorbents (NDA101, NDA103, NDA105) and weakly basic polymeric adsorbent (D301) with a view to studying the effect of hydrogen bonding and Van der Waals interactions between adsorbate and the adsorbent. All adsorption isotherms can be well fitted by Langmuir and Freundlich equations. Compared with D301 driven by hydrogen bonding interaction only and CHA111 driven by Van der Waals interaction only, phenol adsorption on aminated adsorbents driven by both hydrogen bonding and Van der Waals interactions were apparently different, i.e., negative effect for NDA105, positive effect for NDA101 and synergistic effect for NDA103. In this synergistic action, some weak interactions would contribute more or less to the adsorption than they work individually.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11604019,61574020,and 61376018)the Ministry of Science and Technology of China(Grant No.2016YFA0301300)+1 种基金the Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications),Chinathe Fundamental Research Funds for the Central Universities,China(Grant No.2016RCGD22)
文摘Tunneling field effect transistors(TFETs) based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low power devices. Here,we investigate the TFETs based on two different integration types: in-plane and vertical heterostructures composed of two kinds of layered phosphorous(β-P and δ-P) by ab initio quantum transport simulations. NDR effects have been observed in both in-plane and vertical heterostructures, and the effects become significant with the highest peak-to-valley ratio(PVR)when the intrinsic region length is near zero. Compared with the in-plane TFET based on β-P and δ-P, better performance with a higher on/off current ratio of - 10-6 and a steeper subthreshold swing(SS) of - 23 mV/dec is achieved in the vertical TFET. Such differences in the NDR effects, on/off current ratio and SS are attributed to the distinct interaction nature of theβ-P and δ-P layers in the in-plane and vertical heterostructures.
基金Project supported by the SPAT of Shanghai Committee of Chinese People's Political Consultative Conference and Shanghai Education Development Foundation (Grant No.2008012)
文摘Y^3+-doped (Bi 1/2 Na 1/2) TiO 3-CaTiO 3-BaTiO 3 (BNCBT) positive temperature coefficient of resistivity (PTCR) ceramics sintered in air atmosphere were investigated in this study. (Bi 1/2 Na 1/2) TiO 3 (BNT) component can remarkably increase the onset temperature T c of PTCR ceramics with the expense of the resistivity R 25 increase. CaTiO 3 (9–27 mol%) component can decrease the resistivity, and adjust the effects of BNT phase on the T c point. For the sample containing 3 mol% CaTiO 3 , T c raises from 122 ℃ to 153 ℃ when only 0.6 mol% BNT added, while for the ones with higher CaTiO 3 content (9–27 mol%), T c is only increased by a rate of 8–9℃/1.0 mol% BNT. The effects of BNT and CaTiO 3 components on R25/Rmin (negative temperature coefficient effect) are also discussed.
基金Project supported by the National Natural Science Foundation of China(Grant No.11374195)the Taishan Scholar Project of Shandong Province,Chinathe Jinan Youth Science and Technology Star Project,China(Grant No.201406004)
文摘The single thiolated arylethynylene molecule with 9,10-dihydroanthracene core(denoted as TADHA) possesses pronounced negative differential conductance(NDC) behavior at lower bias regime. The adsorption effects of F2 molecule on the current and NDC behavior of TADHA molecular junctions are studied by applying non-equilibrium Green's formalism combined with density functional theory. The numerical results show that the F2 molecule adsorbed on the benzene ring of TADHA molecule near the electrode can dramatically suppresses the current of TADHA molecular junction. When the F2 molecule adsorbed on the conjugated segment of 9,10-dihydroanthracene core of TADHA molecule, an obviously asymmetric effect on the current curves induces the molecular system showing apparent rectifier behavior. However, the current especially the NDC behavior have been significantly enlarged when F2 addition reacted with triple bond of TADHA molecule.
基金funded by the grants from the China Agriculture Research System of MOF and MARA (CARS-41)the Agricultural Science and Technology Innovation Program, China (ASTIP-IAS04)。
文摘San-Huang chicken is a high-quality breed in China with yellow feather, claw and break. However, the abnormal phenomenon of the yellow shank turning into green shank of San-Huang chicken has been a concern, as it seriously reduces the carcass quality and economic benefit of yellow-feathered broilers. In this study, the cause of this abnormal green skin in shank was systematically investigated. Physiological anatomy revealed that the abnormal skin in shank was primarily due to the deposition of melanin under the dermis. After analyzing multiple potential causes such as heredity(pedigree and genetic markers), environment(water quality monitoring) and feed composition(mycotoxin detection), excessive aflatoxin B1(AFB1) in feed was screened, accompanied with a higher L-dihydroxy-phenylalanine(L-DOPA)(P<0.05) and melanin content(P<0.01). So it was speculated that excessive AFB1 might be the main cause of abnormal green skin in shank. Subsequently, the further results showed that a high concentration of AFB1(>170 μg kg–1)indeed induced the abnormal green skin in shank compared to the normal AFB1 content(<10 μg kg–1), and the mRNA levels of TYR, TYRP1, MITE, MC1R and EDN3 genes related to melanin deposition would significantly up-regulate(P<0.01) and the content and activity of tyrosinase(TyR) significantly increased(P<0.05). At the same time, the content of L-DOPA and melanin deposition also increased significantly(P<0.01), which also confirmed the effect of excessive AFB1 on melanin deposition in skin of shank. Results of additional experiments revealed that the AFB1's negative effect on melanin deposition in skin of shank could last for a longer time. Taken together, the results of this study explained the occurrence and possible mechanisms of the abnormal AFB1-related green skin in shank of chickens. Excessive AFB1 in diets increased the L-DOPA content and melanin abnormal deposition in the chicken shank possibly via promoting TyR content and activity, and the expression of melanin synthesis-related genes. Furthermore, our findings once again raised the alarm of the danger of AFB1 in the broiler production.
基金supported by the National Science Foundation of China(key project grant No.51731008 and general project grant No.51671163).
文摘To clarify the anodic dissolution mechanism of Mg,the hydrogen evolution from pure Mg in acidic solutions under galvanostatic conditions were systematically measured.With increasing anodic current density,the cathodic hydrogen evolution rate decreased,and the anodic hydrogen evolution became faster while some surface area on the Mg was becoming dark under anodic polarization.Based on the surface analysis results and the generally accepted basic electrochemical equations,the evolution kinetics of hydrogen from Mg was deduced,and the most possible surface intermediate active species that could facilitate the anodic Mg dissolution and anodic hydrogen evolution were proposed.This paper further develops the model of incomplete film Mg^(+) dissolution,explains many reported experimental phenomena,and clarifies misunderstandings of current mechanism.
基金financially supported by the National Natural Science Foundation of China, China (21922803, 22122807, and 22008072)the Innovation Program of Shanghai Municipal Education Commission, China+1 种基金the Program of Shanghai Academic/Technology Research Leader, China (21XD1421000)the China Postdoctoral Science Foundation, China (2020M671025 and 2019TQ0093)。
文摘Mechanistic understanding of the active intermediates of 2,6-diaminopyridine(DAP) dinitration in the concentrated nitric-sulfuric acid system is of crucial importance for the selectivity control of target product, i.e., 2,6-diamino-3,5-dinitropyridine(DADNP). The active intermediates determining the product selectivity are theoretically studied. The HSO_(4)^(-)-NO_(2)^(+) complex is proposed as the dominant active nitrating intermediate for the first time, which shows low energy barrier(i.e., 10.19 kcal·mol^(-1),1 kcal = 4.186 k J) for direct dinitration of DAP to DADNP. The formed water during the reaction results in not only the formation of less active SO_(4)^(2-)-NO_(2)^(+) complex, but also the occurance of DAP sulfonation(DAP-SO_(3)H intermediate)to facilitate the formation of mononitration byproduct. Meanwhile, the accompanied thermal effects cause the generation of undesirable pyridine-NHNO_(2) intermediate, which is difficult to be rearranged to yield DADNP, inhibiting the reaction and thus giving low DAP conversion. The insights reported here elucidates the importance of thermal effects elimination and water content control, confirmed experimentally in the batch-and micro-reaction systems.
基金Project supported by the Natural Science Foundation of Shandong Province, China (Grant No. ZR2019MA041)Taishan Scholar Project of Shandong Province, China (Grant No. ts20190939)the National Natural Science Foundation of China (Grant No. 62071200)。
文摘Nodal-line semimetals have become a research hot-spot due to their novel properties and great potential application in spin electronics. It is more challenging to find 2D nodal-line semimetals that can resist the spin–orbit coupling(SOC)effect. Here, we predict that 2D tetragonal Zn B is a nodal-line semimetal with great transport properties. There are two crossing bands centered on the S point at the Fermi surface without SOC, which are mainly composed of the pxy orbitals of Zn and B atoms and the pz orbitals of the B atom. Therefore, the system presents a nodal line centered on the S point in its Brillouin zone(BZ). And the nodal line is protected by the horizontal mirror symmetry M_(z). We further examine the robustness of a nodal line under biaxial strain by applying up to-4% in-plane compressive strain and 5% tensile strain on the Zn B monolayer, respectively. The transmission along the a direction is significantly stronger than that along the b direction in the conductive channel. The current in the a direction is as high as 26.63 μA at 0.8 V, and that in the b direction reaches 8.68 μA at 0.8 V. It is interesting that the transport characteristics of Zn B show the negative differential resistance(NDR) effect after 0.8 V along the a(b) direction. The results provide an ideal platform for research of fundamental physics of 2D nodal-line fermions and nanoscale spintronics, as well as the design of new quantum devices.
基金supported financially by the National Key Research and Development Program of China (Nos. 2017YFB0702001 and 2016YFB0301105)the National Natural Science Foundation of China Projects (Nos. 51901047,51871211 and51701129)+5 种基金the Doctor Startup Fund of Natural Science Foundation Program of Liaoning Province (No. 2019-BS-200)the Strategic New Industry Development Special Foundation of Shenzhen (No. JCYJ20170306141749970)the Funds of International Joint Laboratory for Light Alloys, the Liaoning Bai Qian Wan Talents Programthe Domain Foundation of Equipment Advance Research of 13th Five-year Plan (No. 61409220118)the Innovation Fund of Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS)the National Basic Research Program of China (No. 2013CB632205)。
文摘The so-called 'negative difference effect'(NDE) was often defined by the increasing rate of hydrogen evolution from magnesium(Mg) surface under anodic polarization.In this work,a series of electrochemical tests and microstructure observations were performed to provide an evidence that the NDE of Mg-Li alloys can be retarded by increasing lithium content.Potentiostatic,galvanostatic and potentiodynamic polarization experiments using Mg-xLi(x=4,7.5 and 14 wt%) alloys electrodes indicated that Mg-4 Li alloy maintained the enhancing NDE prior to anodic dissolution as that of conventional Mg alloys.However,the emergence of β-Li phase weakened the NDE of duplex Mg-7.5 Li alloy at a low anodic current density,but it was still enhanced apparently after a high applied anodic value(more than 2 mA/cm^2).The surface observations,including the plane and cross-sectional morphologies,confirmed that the cracked surface film derived from the anodic dissolution resulted in the catalytic activity of NDE for Mg-4 Li and Mg-7.5 Li alloys.Furthermore,the NDE of Mg-14 Li alloy was suppressed obviously after a prior applied anodic polarization,which was attributed to the persistent and integrated surface film which endured a higher level of applied anodic potential and current.
基金the financial support for this research by the Australian Research Council(ARC)through the discovery grant DP170102557
文摘We measured the anodic hydrogen evolution rates for various applied anodic current densities and estimated the corresponding cathodic hydrogen evolution rates.The estimated cathodic hydrogen evolution rates were less than the measured anodic hydrogen evolution rates,contradicting the enhanced catalytic activity mechanism of Mg corrosion.In addition,this model was contradicted by the measured apparent Mg valence of 1.2±0.1.In contrast,the uni-positive Mg^(+)mechanism of Mg corrosion was supported by(i)the apparent Mg valence of 1.2±0.1,and(ii)the fact that the measured anodic hydrogen evolution rate increased with increasing weight loss rate.
基金the National Natural Science Foundation of China(Nos.20771030 and 20671025).
文摘Conductive polyvinylidene fluoride(PVDF)matrix composites filled with graphited fiber(GF)or carbon fiber(CF)were prepared by the melt-mixing method.The breakage and length distribution of the fibers in the polymer matrix were studied by scanning electron microscope(SEM)and optical microscope(OM)observations,respectively. The differences in the positive temperature coefficient(PTC)effects of the composites were mainly attributed to inter-fiber contact ability.The elimination of the negative temperature coefficient(NTC)effect for CF/PVDF composite was because of an increase in the viscosity of the polymer matrix.With the same filler content,CF could be more effective,to eliminate the NTC effect when compared with GF.Addition of 2%CF(mass fraction)in the PVDF composite with 7%GF(mass fraction)could effectively eliminate the NTC phenomenon of the composite.
文摘We obtained the output characteristics in wurtzite Al0.15Ga0.85N/GaN MODFETs with the full band Monte Carlo method. The gate length Lg and the channel length Los in the device are 0.2 μm and 0.4 urn, respectively. In the output characteristics we found a differential negative resistance effect. That is, as VDS is a constant, initially, VDS increases with increasing VDS. When VDS exceeds a certain critical value, IDS decreases with increasing VDS. The analysis for velocity-field characteristics in wurtzite CaN, the distributions of the electric field and the electron velocity in the two dimensional electron gas channel indicates that the differential negative resistance effect of the electron average velocity results in the differential negative resistance effect of the output characteristics. The transient transport also is related to the differential negative resistance effect of the output characteristics. This effect only can be observed in the devices with very short channel.