长期施肥下我国典型农田耕层土壤的pH演变

探索长期不同施肥措施下农田耕层土壤的pH演变，为进一步揭示农田土壤酸化的机制及其预防措施提供依据。收集了我国典型农田6个长期（18～30a）施肥试验（祁阳红壤、进贤红壤、重庆紫色土、公主岭黑土、哈尔滨黑土常量施肥和高量施肥）的历史观测资料，对耕层土壤pH在不同试验阶段（每6a）和施肥措施（对照不施肥（CK）、单施化学氮肥（N）、磷钾配施氮肥（NPK）和有机肥配施化肥（NPKM））间的差异性进行检验，并计算土壤酸化速率。结果表明，试验期间，对照CK处理的耕层pH略有降低，平均土壤酸化速率为0．013pHa-1；N处理的1～6a，祁阳红壤、公主岭黑土和哈尔滨黑土常量施肥试验的耕层pH较对照显著降低0．32～0．55个单位，至最近6a，所有试验的耕层pH较对照显著降低0．64～1．46个单位；NPK处理的耕层pH在试验1～12a明显低于N处理；NPKM处理的耕层pH却较NPK处理高0．30～0．53个单位，pH变化趋势与NPK相似。处理间成对T检验表明，长期施肥农田的土壤酸化速率大小顺序为：N〉NPK〉NPKM—CK，N和NPK处理的土壤酸化速率分别为对照的4．6倍和3．2倍。基于湿润或半湿润地区排水良好的旱作或水旱轮作农田分析了农田土壤酸化过程。尽管存在地域差异性，长期施肥农田耕层土壤的pH演变存在对施肥措施的共性响应特征。

Wind-induced responses of super-large cooling towers

Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads(ESWLSs)were derived based on structural dynamics and random vibration theory.The consistent coupled method(CCM)was presented to compensate the coupled term between background and resonant response.Taking the super-large cooling tower(H=215 m)of nuclear power plant in Jiangxi Province,China,which is the highest and largest in China,as the example,based on modified equivalent beam-net design method,the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out.Then,combining wind tunnel test and CCM,the effects of self-excited force on the surface pressures and wind-induced responses are discussed,and the wind-induced response characteristics of background component,resonant component,coupled term between background and resonant response,fluctuating responses,and wind vibration coefficients are discussed.It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.

Nonlinear Optical Response of Conjugated Polymer to Elec tric Field

The organic π-conjugate d polymers are of major interest materials for the use in electro-optical and no nlinear optical devices. In this work, for a selected polyacetylene chain, the optical absorption spectra in UV/Vis regime as well as the linear polarizabiliti y and nonlinear hyperpolarizability are calculated by using quantum chemical ab initio and semiempirical methods. The relationship of its optical property to el ectric field is obtained. Some physical mechanism of electric field effect on mo lecular optical property is discussed by means of electron distribution and intr amolecular charge transfer.

Comprehensive Alcohol-/Ion-Responsive Properties of Poly(N-Isopropylacrylamide-co-Benzo-18-Crown-6-Acrylamide) Copolymers

In this paper, we report on the comprehensive alcohol-/ion-responsive properties of a smart copolymer poly（N- isopropylacry]amide-co-benzo-18-crown-6-acrylamide） （P（NIPAM-co-BCAm））. The orthogonal design method is adopted for experimental design. The experimental results show that alcohol can trigger the shrinking and Ba2t can induce the swelling of the P（NIPAM-co-BCAm） copolymer. According to the phase transition tempera- ture （LCST） change results of the copolymer, the influence of variables on the LCST changes weakens in the following order： alcohol concentration 〉 alcohol species 〉 metal ion species 〉 BCAm concentration 〉 ion concentration. The larger the alcohol concentration and the larger the molecular size of alcohols, the lower the LCST value; on the contrary, the more the BCAm content in the copolymer or the larger the BCAm/ion complex stability constant （IgK） or the larger the ion concentration is, the higher the LCST value. For a P（NIPAM-co-BCAm ） copolymer with a fixed BCAm content, a binary function of ion concentration and IgK of BCAm/ion is developed to precisely predict the LCST values of the copolymer in different metal ion solutions. The results provide valuable information for fabricating artificial biomimetic G-protein-gated inwardly rectifying potassium （GIRK） channels that are activated by alcohol and inhibited by Ba2＋.

A Study on Stochastic Resonance in Biased Subdiffusive Smoluchowski Systems within Linear Response Range

The method of matrix continued fraction is used to investigate stochastic resonance (SR) in the biasedsubdiffusive Smoluchowski system within linear response range.Numerical results of linear dynamic susceptibility andspectral amplification factor are presented and discussed in two-well potential and mono-well potential with differentsubdiffusion exponents.Following our observation,the introduction of a bias in the potential weakens the SR effect inthe subdiffusive system just as in the normal diffusive case.Our observation also discloses that the subdiffusion inhibitsthe low-frequency SR,but it enhances the high-frequency SR in the biased Smoluchowski system,which should reflect a'flattening' influence of the subdiffusion on the linear susceptibility.

A high strength pH responsive supramolecular copolymer hydrogel

Constructing high strength pH sensitive supramolecular polymer hydrogel remains very challenging due to the unavoidable network swelling caused by ionization of acid or basic groups at a specified pH.In this work,we proposed a simple and very convenient approach to fabricate high strength pH responsive supramolecular polymer(SP) hydrogels by one-pot copolymerization of N-acryloyl glycinamide(NAGA) and 2-vinyl-4,6-diamino-1,3,5-triazine(VDT),two feature hydrogen bonding monomers.In these PNAGA-PVDT SP hydrogels obtained,the hydrogen bonding of NAGA was shown to play a dominant role in reinforcing strength,while the hydrogen bonding of diaminotriazine served as a pH sensitive moiety.At pH 3,the mechanical properties of PNAGA-PVDT hydrogels decreased to a different extent due to the breakup of hydrogen bonding;in contrast,the hydrogel resumed the original strength while pH was raised to 7.4 because of reconstruction of hydrogen bonding.Over the selected pH range,the PNAGA-PVDT hydrogels exhibited up to 1.25 MPa tensile strength,845% breaking strain,69 kPa Young's modulus and 21 MPa compressive strength.This novel high strength pH-responsive SP hydrogels may find applications in biomedical and industrial fields.

Analyte-responsive fluorescent probes with AIE characteristic based on the change of covalent bond

It is important for the determination of biologically and/or environmentally relevant species by utilization of fluorescent probes. Conventional fluorescent probes are subjected to the influence of aggregation-caused quenching that is limiting their application due to low selectivity as well as photobleaching. Additionally, quencher pairs are usually introduced in the design of these probes, which lead to the complex synthetic procedure. A novel class of fluorogens with aggregation-induced emission (AIE) characteristic provide a solution to address the dilemma. By taking advantage of the unique characteristic of AIE fluorogens, specific turn-on probes have been developed via combination with recognition components, exhibiting low background, good selectivity and outstanding photostability. This review focuses on the development of fluorescent probes with AIE characteristics via the bond cleavage as well as formation strategy.

Linear response eigenvalue problem solved by extended locally optimal preconditioned conjugate gradient methods

The locally optimal block preconditioned 4-d conjugate gradient method(LOBP4dC G) for the linear response eigenvalue problem was proposed by Bai and Li(2013) and later was extended to the generalized linear response eigenvalue problem by Bai and Li(2014). We put forward two improvements to the method: A shifting deflation technique and an idea of extending the search subspace. The deflation technique is able to deflate away converged eigenpairs from future computation, and the idea of extending the search subspace increases convergence rate per iterative step. The resulting algorithm is called the extended LOBP4 dC G(ELOBP4dC G).Numerical results of the ELOBP4 dC G strongly demonstrate the capability of deflation technique and effectiveness the search space extension for solving linear response eigenvalue problems arising from linear response analysis of two molecule systems.