Effects of Curing Methods on the Permeability and Mechanism of Cover Concrete

Curing methods are one of the most important factors in determining the quality and compactness of cover concrete.The effect of curing methods on the water absorption and sorptivity coefficient of cover concrete with the substitution ratio of fly ash(FA)and ground granulated blast slag(GGBS)for cement between 30 wt%and 40 wt%was studied by capillary water absorption test.The vacuum saturation test and mercury intrusion test were employed to characterize these differences in the pore structure of cover concrete under different curing methods.With further analysis of the compactness of microstructure by SEM,the mechanism of the impact of curing methods on the permeability of cover concrete was revealed.The results obtained indicate that the effect of curing methods on the water absorption,sorptivity coefficient and porosity of cover concrete shows the trend of natural curing>cover curing>water curing>standard curing.It is also shown that reasonable curing is advantageous to reduce the porosity and permeability of cover concrete.In natural curing conditions,the appearance of porosity increasing and pore structure coarsening is more critical for covering concrete with mineral admixtures than for pure cement concrete.Therefore,the permeability of cover concrete with mineral admixtures is more sensitive to the early-age curing methods.

Analysis on Pore Structure of Non-Dispersible Underwater Concrete in Saline Soil Area

In this paper,mercury intrusion porosimetry(MIP)is used to test the pore structure of non-dispersible underwater concrete so as to study the influence of pouring and curing environment,age and slag powder on the pore characteristics of concrete,analyze the pore characteristics,porosity and pore distribution of concrete in different hydration stages,and reveal the relationship between pore structure and permeability of concrete.The results show that the pore-size distribution of concrete in fresh water condition is better than that in sulfate environment and mixed salt environment,and therefore,sulfate as well as mixed salt are not conducive to the development of pore structure of non-dispersible underwater concrete;chlorine salt has little effect on the pore structure of nondispersible underwater concrete;under the three conditions of sulfate,chlorine and mixed salt,the porosity of concrete mixed with slag powder is lower than that of concrete without slag powder.The results indicate that the addition of slag powder can ameliorate the pore size distribution of non-dispersed underwater concrete,reduce the porosity,and make the concrete structure more compact,which is beneficial to improve the permeability resistance of concrete at the macro level.

Effect of GGBS on performance deterioration of non-dispersible underwater concrete in saline soil

In saline soil areas,there are a large number of ions in soil or water environments,such as Cl^(-)and SO_(4)^(2-),which have strong corrosive interactions with buildings.To study the deterioration of non-dispersible underwater concrete in sulfate,chloride,and mixed salt environments,the compressive strength and deterioration resistance coefficient of the studied concrete mixed with different amounts of ground granulated blast-furnace slag(GGBS)were analyzed in this paper.At the same time,the micro morphology and corrosion products distribution of the studied concrete were observed by means of SEM,plus XRD diffraction,TG-DTG and FT-IR analyses to explore the influence of corrosive solutions on the hydration products of concrete.We also analyzed the mechanism of improving the deterioration resistance of the studied concrete by adding GGBS in a saline soil environment.The results show that the compressive strength of the studied concrete in a chloride environment was close to that in a fresh water environment,which means that chloride has no adverse effect on compressive strength.The deterioration of the studied concrete was most serious in a sulfate environment,followed by mixed salt environment,and the lowest in a chloride environment.In addition,by adding GGBS,the compressive strength and deterioration resistance of the studied concrete could be effectively improved.

Direct Imaging of Cross-sectional Magnetization Reversal in the Exchange biased CoFeB/IrMn Bilayer

Magnetoelectronic devices have been widely used in magnetic storage and sensor.The pinned ferromagnetic layer with a unidirectional magnetic anisotropy is an important reference layer in the devices.Ferromagnetic material is pinned by antiferromagnetic material at the interface through

Monoclonal Antibody-Based Enzyme Linked Immunosorbent Assay for the Analysis of Jasmonates in Plants

Methyl jasmonate （MeJA） and its free-acid form, jasmonic acid （JA） are naturally occurring plant growth regulators widely distributed in higher plants. In order to improve the sensitivity for the analysis of MeJA at low levels in small amounts of plant samples, a monoclonal antibody （MAb） （designated as MAb 3E5D7C4B6） against MeJA was derived from a JA- bovine serum albumin （BSA） conjugate as an immunogen. The antibody belongs to the IgG1 subclass with a κ type light chain and has a dissociation constant of approximately 6.07 ×10^-9 M. MAb3E5D7C4B6 is very specific to MeJA. It was used to develop a direct competitive enzyme-linked immunosorbent assay （dcELISA）, conventional and simplified indirect competitive ELISAs （icELISA）. JA was derivatized into MeJA for the ELISA analysis. The IC50 value and detection range for MeJA were, respectively, 34 and 4-257 nglmL by the conventional icELISA, 21 and 3-226 nglmL by the simplified icELISA and 5.0 and 0.7-97.0 nglmL by the dcELISA. The dcELISA was more sensitive than either the conventional or simplified icELISA. The assays were used to measure the content of jasmonates as MeJA in tobacco leaves under drought stress or inoculated with tobacco mosaic virus and tomato leaves inoculated with tomato mosaic virus or Lirioinyza sativae Blanchard as compared with the corresponding healthy leaves. The increased jasmonates content indicated its role in response to the drought stress and pathogens.

Flexible magnetic thin films and devices

Flexible electronic devices are highly attractive for a variety of applications such as flexible circuit boards, solar cells, paper-like displays, and sensitive skin, due to their stretchable, biocompatible, light-weight,portable, and low cost properties. Due to magnetic devices being important parts of electronic devices, it is essential to study the magnetic properties of magnetic thin films and devices fabricated on flexible substrates. In this review, we mainly introduce the recent progress in flexible magnetic thin films and devices, including the study on the stress-dependent magnetic properties of magnetic thin films and devices, and controlling the properties of flexible magnetic films by stress-related multi-fields, and the design and fabrication of flexible magnetic devices.

Construction of a low-valent thiolate-bridged dicobalt platform and its reactivity toward hydrogen activation and evolution

Low-valence transition metallic complexes have drawn longstanding attention due to their high reactivity toward catalytic transformation of various small molecules.Among these known complexes,the low-valence metal centres are commonly stabilized by neutral bulky ligands with strong electron-donating capacity.However,low-valence bimetallic complexes supported by anionic sulfur and cyclopentadienyl ligands are still difficult to obtain in high isolated yield.Herein,we report the synthesis and characteri-zation of two scarce thiolate-bridged Co^(I)Co^(II)and Co^(I)Co^(I)complexes bearing sterically demanding ligands through two stepwise one-electron reduction processes.Interestingly,the Co^(I)Co^(II)complex can facilely promote the homolytic cleavage of dihydrogen across the short Co−Co metallic bond to give a Co^(II)Co III dihydride bridged complex,which is capable of serving as a competent hydrogen atom transfer agent.Moreover,the anionic Co^(I)Co^(I)complex can trigger a stepwise hydrogen generation cycle involving several isolated and structurally well-characterized intermediates.

Synthesis,characterization and reactivity of thiolate-bridged cobalt-iron and ruthenium-iron complexes

Thiolate-bridged hetero-bimetallic complexes[Cp^(*)M(MeCN)N_(2)S_(2)FeCl][PF_(6)](2,M=Ru;3,M=Co,Cp^(*)=η^(5)-C_(5)Me_(5),N_(2)S_(2)=N,N'-dimethyl-3,6-diazanonane-1,8-dithiolate)were prepared by self-assembly of dimer[N_(2)S_(2)Fe]2 with mononuclear precursor[Cp^(*)Ru(MeCN)_(3)][PF_(6)]or[Cp^(*)Co(MeCN)_(3)][PF_(6)]_(2)in the presence of CHCl_(3)as a chloride donor.Complexes 2 and 3 exhibit obviously different redox behaviors investigated by cyclic voltammetry and spin density distributions supported by DFT calculations.Notably,iron-cobalt complex 3 possesses versatile reactivities that cannot be achieved for complex 2.In the presence of CoCp_(2),complex 3 can undergo one-electron reduction to generate a stable formally Co^(II)Fe^(II)complex[Cp^(*)CoN_(2)S_(2)FeCl](4).Besides,the terminal chloride on the iron center in 3 can be removed by dehalogenation agent AgPF_(6)or exchanged with azide to afford the corresponding complexes[Cp^(*)Co(MeCN)N_(2)S_(2)Fe(MeCN)][PF_(6)]_(2)(5)and[Cp^(*)Co(MeCN)N_(2)S_(2)Fe(N_(3))][PF_(6)](6).In addition,complexes 2,3 and 4 show distinct catalytic reactivity toward the disproportionation of hydrazine into ammonia.These results may be helpful to understand the vital role of the heterometal in some catalytic transformations promoted by heteromultinuclear complexes.