Se(Ⅳ)对水杨酸与DNA相互作用的影响

利用荧光光谱法和紫外吸收光谱法研究了Se(Ⅳ)对水杨酸与DNA的结合模式、结合常数的影响.结果表明,Se(Ⅳ)的加入使水杨酸与DNA由嵌入式结合转变为沟槽结合,结合作用力由琉水作用力转变为氢键和范德华力,同时结合常数变大,说明Se(Ⅳ)对水杨酸与DNA的结合起促进作用,这可能是由于Se(Ⅳ)和水杨酸形成络合物,又通过水...     

部分相干平顶高斯光束通过球差透镜的聚焦特性

 基于部分相干光的传输理论,研究了部分相干平顶高斯光束通过球差透镜聚焦后轴上点的光强分布。数值计算表明:轴上最佳聚焦点随着球差从负到正的变化而向几何焦点方向移动;光束阶数越大,实现最佳聚焦点越过几何焦点所需的正球差值越小;正负球差对应的最佳聚焦点始终分居于无球差时最佳聚焦点的两侧;轴上最佳聚焦点的光强随着球差从负到正的变化而变小;当正负球差绝对值较大时,光强随球差的变化较为缓慢,而在球差值为0附近,光强随球差的变化比较剧烈。     

Manipulated localized surface plasmon resonances in silver nanoshells coated with a spherical anisotropic layer

<正>The influences of the anisotropy of the outer spherically anisotropic(SA) layer on the far-field spectra and nearfield enhancements of the silver nanoshells are investigated by using a modified Mie scattering theory.It is found that with the increase of the anisotropic value of the SA layer,the dipole resonance wavelength of the silver nanoshell first increases and then decreases,while the local field factor(LFF) reduces.With the decrease of SA layer thickness, the dipole wavelength of the silver nanoshell shows a distinct blue-shift.When the SA layer becomes very thin,the modulations of the anisotropy of the SA layer on the plasmon resonance energy and the near-field enhancement are weakened.We further find that the smaller anisotropic value of the SA layer is helpful for obtaining the larger near-field enhancement in the Ag nanoshell.The geometric average of the dielectric components of the SA layer has a stronger effect on the plasmon resonance energy of the silver nanoshell than on the near-field enhancement.     

Preparation and characterization of crosslinked cellulose/sulfosuccinic acid membranes as proton conducting electrolytes

A series of crosslinked polymer electrolyte membranes were prepared by blending cellulose and sulfosuccinic acid (SA) for fuel cell applications. The crosslinking reaction of membranes occurred via the esterification between –OH of cellulose and –COOH of SA, as confirmed by FT-IR spectroscopy. Both the ion exchange capacity and the proton conductivity increased in proportion to the increase of SA concentrations due to the increasing portion of charged groups in the membrane. In contrast, the water uptake linearly increased up to 25 wt.% of SA concentration, above which it decreased abruptly. The maximum behavior of water uptake may be a result of competitive effect between the increasing number of ionic sites and the increasing degree of crosslinking with the SA concentrations. Wide angle X-ray scattering also showed that the crystalline structures of cellulose disappeared upon the introduction of SA. The mechanical properties of cellulose/SA membranes, i.e., tensile strength at break and Young’s modulus, showed a maximum at 15 wt.% of SA, as revealed by universal testing machine. These membranes exhibited good thermal stability up to 250 °C, as revealed by thermal gravimetric analysis.     

Ag_2O胶体粒子的自组装单层膜和多层膜

本文制备了Ａｇ２Ｏ胶体粒子的自组装单层膜和多层膜。运用接触角测量、红外吸收光谱和紫外可见吸收光谱等手段证实了Ａｇ２Ｏ胶体粒子能够组装在具有羧基的基底上,在有１,１８ 十八烷基二羧酸做为交联剂的情况下还可形成自组装多层膜     

Styrene-butadiene rubber/halloysite nanotubes nanocomposites modified by sorbic acid

Sorbic acid (SA) was used to improve the performance of styrene-butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed mechanisms for the largely improved performance were studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), porosity analysis and crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through SA intermediated linkages. SA bonds SBR and HNTs through grafting copolymerization/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and SA was achieved. Formation of zinc disorbate (ZDS) was revealed during the vulcanization of the composites. However, in the present systems, the contribution of ZDS to the reinforcement was limited. Effects of SA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of SA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and SA and the largely improved dispersion of HNTs.     

Monitoring the gelation of polyacrylamide–sodium alginate composite by fluorescence technique

Polyacrylamide (PAAm)–sodium alginate (SA) composite was prepared with different amounts of SA varying in the range between 0.06% and 2% (w/v). The PAAm–SA composite was characterized by the steady-state fluorescence technique. Pyranine was added as a fluoroprobe for monitoring the polymerization. It was observed that pyranine molecules bind to AAm and SA chains upon the initiation of the polymerization. Thus, the fluorescence spectra of the bonded pyranines shift to the shorter wavelengths. Fluorescence spectra from the bonded pyranines allowed us to monitor the sol–gel phase transition, and to test the universality of the sol–gel transition as a function of SA contents. Observations around the critical point show that the gel fraction exponent, β, and the weight average degree of polymerization exponent, γ, agreed with the percolation result for (<0.25% (w/v)) SA contents. However, classical results were produced at (<2% (w/v)) SA contents.     

部分相干平顶高斯光束通过球差透镜的聚焦特性

基于部分相干光的传输理论,研究了部分相干平顶高斯光束通过球差透镜聚焦后轴上点的光强分布。数值计算表明:轴上最佳聚焦点随着球差从负到正的变化而向几何焦点方向移动;光束阶数越大,实现最佳聚焦点越过几何焦点所需的正球差值越小;正负球差对应的最佳聚焦点始终分居于无球差时最佳聚焦点的两侧;轴上最佳聚焦点的光强随着球差从负到正的变化而变小;当正负球差绝对值较大时,光强随球差的变化较为缓慢,而在球差值为0附近,光强随球差的变化比较剧烈。     

Ultrafast Saturable Absorption of Core/Shell Colloidal Quantum Dots

Ultrafast saturable absorption (SA) materials that are capable of blocking the optical absorption under strong excitation have extensive applications in photonic devices. This work presents core/shell colloidal quantum dots (CQDs) which have the quantized energy levels, excellent band gap tunability, and possess significant SA performance. When the band gap is close to the pump pulse energy, the CQDs show significant resonant SA response. At the same excitation conditions, the core/shell CQDs dispersions show better SA response than graphene dispersions, and comparable to the recently reported molybdenum disulfide. The carrier dynamics of the SA of the CQDs is analyzed systematically. The research has also found that the two‐photon absorption of the CQDs show nearly cubic power law of the band gap, while the SA performance keeps almost the same in the nonresonant regime. Further, superior passive Q‐switched laser behavior is observed using the CQDs as a saturable absorber. The results directly reveal the physical processes of this basic problem and broaden the applications of CQDs in photonic devices.     

Directed self-assembly process for nano-electronic devices and interconnect

Requirements for nano-electronic devices and interconnect in conventional logic circuit architecture are examined to reveal the possible device structure containing self-assembly (SA) features. For integration with lithography, we discuss the features of the SA process and then present a full process flow for a novel type of SA nano-crystal EEPROM cells. The logic functionality below the lithography limit derived from the SA dot arrays and the I–V characteristics including the Coulomb blockade effect are then presented.     

Mechanical and Thermal Properties of Polypropylene/Silica Aerogel Composites

Polypropylene (PP) composites including various amounts of silica aerogel (SA) microparticles were prepared by melt mixing in an internal mixer. The morphology and microstructure of the prepared composites were investigated by scanning electron microscopy (SEM). Mechanical properties of the samples, including elastic modulus, tensile stress, elongation and stress at break, were measured by tensile tests. In addition, the other mechanical features, including Izod impact strength, hardness and wear resistance, were evaluated and then related to the structure of the PP/SA composites. Furthermore, the thermal characteristics of the composites, such as heat deflection temperature and thermal stability, were studied by thermal gravimetric analysis (TGA). The SEM photographs indicated the satisfactory SA particles dispersion for the compositions of 1% and 3% but agglomeration of the aerogels at higher SA contents. Since the composites became stiffer, the impact and tensile strength decreased. The addition of the SA to the PP matrix yielded harder samples with lower weight loss and coefficients of friction in wear tests. The TGA evaluations confirmed that the presence of SA promoted and upgraded the thermal stability and heat deflection temperature of PP. The thermal results proved the superior potential of PP as an insulator when the SA particles were added.     

All-optical 2R regeneration using passive saturable absorption

This paper reports on the regenerative properties and efficiency of an all-optical 2R regenerator based on a tandem of saturable absorber (SA) chips. A new SA structure allowing mark level equalization, which is a complement to the function of extinction ratio enhancement of the classical SA structure, is described. The experimental results at 42.6 Gbit/s show that amplitude fluctuations on both low and high power levels are significantly reduced with the SA tandem regenerator, and the system margin improvements in terms of receiver sensitivity and Q factor are obtained.     

Surface states and its influence on luminescence in ZnS nanocrystallite

In this pape,r the influence of surface effects on the self-activated (SA) luminescence in ZnS nanoparticles prepared by the wet-chemical method is presented. It is observed that the luminescence of SA decreases dramatically by rinsing with methanol. In the rinsed sample, the luminescence of SA increases more by ultraviolet (UV) light irradiation. To clarify its origin, the Raman spectra and electron paramagnetic resonance (EPR) are studied. The results demonstrate that the vibrational modes assigned to organic functional groups of -OH and -COO and -CH₃ decreases remarkably by rinsing, while the EPR signal originated from the unpaired electrons of some transition metal impurity ions including Mn²⁺ increases. It is suggested that the SA centers prefer to occupy the sites near the surface and that the donor of SA emission may be partly related to the organic functional groups of -OH and -COO adsorbed on the surface. The surface-dangling bonds caused by unpaired electrons of some transition metal impurity ions play a role of surface states, leading to the quenching of the SA emissions. The organic functional groups chemically combine with these surface-dangling bonds leading to the decrease in surface states and surface nonradiative relaxation channels and to the increase in the SA emissions.     

硬脂酸镉和山嵛酸镉混合LB膜的微结构

用X射线衍射研究了沉积于亲水玻璃基底上的硬脂酸镉和山嵛酸镉多层混合LB膜的微区结构和相分离情况．纯的脂肪酸镉衍射峰没有在混合LB膜的XRD谱图中出现,说明混合膜中形成的微区很小而且均匀分布．混合膜样品的面间距随硬脂酸镉和山嵛酸镉混合比例的变化形成一条台阶状的曲线,这表明在它们比例变化的过程中,只形成了三种有序的结构,而且每一种结构,特别是长短链交错的微结构,可以在一定的比例范围内保持;另外,在长短链交错的微结构中,两种脂肪酸长链具有相同的偏离膜平面法线方向的小倾角,这也可由它们傅立叶红外透射谱中表征脂肪酸长链分子取向的亚甲基CH2相同的峰位2847.80和2914.37 cm-1(对应于CH2对称和反对称伸缩振动)得到说明．当混合比例超出1/5?1/1,混合膜将会经历一个纵向有序度降低的过程,表现为混合膜相对X射线衍射强度随混合比例以\W"形变化．     

基于改进遗传与模拟退火融合的RISP软硬件划分

软硬件划分是可重构指令集处理器在软硬件协同设计中的关键问题,通过对比遗传算法和经典模拟退火算法的优缺点,提出改进遗传算法的适应度函数,同时将Tsallis接受准则引入到经典模拟退火当中。其思路是用遗传算法的结果来制约模拟退火算法产生的随机状态,然后由模拟退火的接受准则以及产生的随机状态函数对遗传算法的种群进行更新,从而找到全局近似最优解。实验结果证明,改进算法与单一遗传算法以及经典模拟退火算法相比,其收敛速度和适应度更好,找到全局近似最优解的概率更大。     

Nanosecond Pulse Generation with Silver Nanoparticle Saturable Absorber

Nanosecond pulse generation in an erbium-doped fiber laser (EDFL) passively mode-locked by a silver nanoparticle(SNP)-based saturable absorber(SA) is experimentally demonstrated. The SA is fabricated by depositing a nanosized SNP layer onto the surface of polyvinyl alcohol film through the thermal evaporation process. By inserting the SA into an EDFL cavity, stable mode-locked operation is achieved at 1561.5 nm with the maximum pulse energy up to 52.3 nJ. The laser operates at a pulse repetition frequency of 1.0 MHz with a pulse width of 202 ns. These results suggest that SNPs could be developed as an effective SA for mode-locking pulse generation.     

Synthetic aperture ultrasound imaging

The paper describes the use of synthetic aperture (SA) imaging in medical ultrasound. SA imaging is a radical break with today's commercial systems, where the image is acquired sequentially one image line at a time. This puts a strict limit on the frame rate and the possibility of acquiring a sufficient amount of data for high precision flow estimation. These constrictions can be lifted by employing SA imaging. Here data is acquired simultaneously from all directions over a number of emissions, and the full image can be reconstructed from this data. The paper demonstrates the many benefits of SA imaging. Due to the complete data set, it is possible to have both dynamic transmit and receive focusing to improve contrast and resolution. It is also possible to improve penetration depth by employing codes during ultrasound transmission. Data sets for vector flow imaging can be acquired using short imaging sequences, whereby both the correct velocity magnitude and angle can be estimated. A number of examples of both phantom and in vivo SA images will be presented measured by the experimental ultrasound scanner RASMUS to demonstrate the many benefits of SA imaging.     

Contributions from changes in various solar indices in cycles 20–23 and 24 to the modulation of cosmic rays

The modulation of cosmic rays (CRs) observed at neutron monitors during the minimum, growth, maximum, and beginning of the decay of solar activity (SA) of cycle 24 (2008–2015) is compared to the modulation of CRs in the same periods of SA of cycles 20–23. After a prolonged minimum of SA between cycles 23 and 24 in 2007–2009 and the maximum of CRs at the end of 2009, when CR intensity exceeded the previous four CR maxima, the SA growth phase displayed weaker modulation of CRs than in the corresponding periods of the previous cycles. The shorter variations in CRs (oscillations with variable periods and activity spikes) were clearer against the background of the reduction in the 11-year variation during SA growth in 2011–2014. The current SA cycle (24) saw a scenario with two SA maxima, and the CRs showed one minimum at the end of 2014 that differed from the maximum of 2009 by ≈12% for particles with a rigidity of 10 GV. CR modulation in the last cycle was the weakest since neutron monitors began operating. At the beginning of 2015, the CRs started to recover. Possible reasons for the unusually weak CR modulation are considered. Quantitative estimates are made of the contribution from different characteristics of the solar magnetic field to CR modulation in the period of cycle 24 under study and in the corresponding periods of solar cycles 20–23, and the estimates are compared.     

光谱分析和延迟荧光检测研究外源水杨酸对拟南芥光合作用的影响

外源水杨酸在影响植物活性氧代谢以及光合作用等方面起着重要作用.该文以野生型拟南芥和胁迫条件下内源水杨酸含量较高的cpr5突变体和内源水杨酸含量较低的eds-4突变体为材料,采用光谱分析和延迟荧光检测分析手段,研究了不同浓度的外源水杨酸对三种拟南芥离体叶片光合能力的影响,实验发现100和300 μmol·L-1较低浓度的外源水杨酸对野生型拟南芥离体叶片,eds-4叶片的光合作用都有一定的促进作用,而对cpr5叶片的光合会产生抑制,形成一种胁迫.500μmol·L-1较高浓度的外源水杨酸对三种拟南芥离体叶片均形成了一种胁迫,进而阻抑和降低了叶片的光合效能.DCF(dichloro fluorescein)标记活性氧检测了外源水杨酸作用下叶片活性氧产生量的变化,发现在500μmol·L-1外源水杨酸作用下60min内叶片组织中活性氧产生了明显的积累.     

Cluster formation in binary fluids with competing short-range and long-range interactions

Abstract

The equilibrium phase behaviour of a model binary fluid is investigated through Monte Carlo simulations and by developing a molecular thermodynamic model. Both fluid components interact through a hard core with short-range attractions (SA), but one of the components exhibits an additional long-range repulsion (SA+LR). We find that phase behaviour for this system is controlled by the cross-interaction between the two types of particles as well as their chemical potentials. For a weak cross-interaction, the system displays behaviour that is a composite of the behaviour of the individual components, i.e. the SA component can display bulk vapour/liquid phase separation, while the SALR component can display giant micelle-like clusters for a suitable combination of SA and LR interactions. For a strong cross-interaction, qualitatively different behaviour is observed, with the resulting clusters typically composed of a more equal mixture of SA and SALR particles. Moreover, these mixed clusters can exist even when the SA component by itself would be undersaturated or supercritical, and/or when the SALR component by itself would not form giant clusters. These insights should help to identify the mechanisms for clustering in experimental systems where giant equilibrium clusters are observed.