Naphthalene derivatives of a conformationally locked GFP chromophore with large stokes shifts

The active development of fluorescence microscopy requires an increase in the variety of the dyes and their characteristics. Compounds with a large Stokes shift, i.e., a large difference between the positions of the absorption and emission maxima, have attracted the interest of researchers as a tool that can be used for multicolor labeling. One of the known approaches to increase the Stokes shift is the introduction of additional polycyclic fragments. Herein, we report novel derivatives of a conformationally locked GFP chromophore containing the naphthalene ring. The proposed modification leads not only to the enhancement of the Stokes shift up to 100 nm but also leads to the noticeable red-shift of the emission and absorption spectra in contrast with the corresponding derivatives with one benzene ring.     

Impact of nanoconfinement on the diisopropylammonium chloride (C6H16ClN) organic ferroelectric

The dielectric studies of diisopropylammonium chloride (DIPAC) nanoparticles embedded into opal and MCM-41 silica matrices are presented. It is shown that the ferroelectric phase transition shifts to low temperatures and broadens for DIPAC within the opal pores compared to bulk. The thermal hysteresis of the transition increases under opal nanoconfinement. No anomalies of the permittivity relevant to the ferroelectric transition are observed for DIPAC within the MCM-41 molecular sieves likely due to formation of the amorphous phase.     

《应用声学》2018年总目次

Contents of JOURNAL of APPLIED ACOUSTICS, Vol. 37, 2018     

Incompressible Viscous Fluid Flows in a Thin Spherical Shell

Linearized stability of incompressible viscous fluid flows in a thin spherical shell is studied by using the two-dimensional Navier–Stokes equations on a sphere. The stationary flow on the sphere has two singularities (a sink and a source) at the North and South poles of the sphere. We prove analytically for the linearized Navier–Stokes equations that the stationary flow is asymptotically stable. When the spherical layer is truncated between two symmetrical rings, we study eigenvalues of the linearized equations numerically by using power series solutions and show that the stationary flow remains asymptotically stable for all Reynolds numbers.      

恒星氦燃烧关键反应12C(α,γ)16O天体物理S因子及其反应率

恒星氦燃烧阶段3α反应和12C（α,γ）16O反应相互竞争,两者的反应率共同决定了氦燃烧结束后12C与16O的丰度比,该比值是大质量恒星后继演化以及伴随的元素核合成过程的初始条件。目前,氦燃烧12C（α,γ）16O反应起始T₉=0.2处,天体物理模型要求的反应率的精确度要低于10%,然而尚未有实验或理论给出满足要求的结果。最为直接和可靠地获取12C（α,γ）16O反应率的方法,就是尽可能往低能区测量其天体物理S因子,然后通过理论外推到感兴趣的能区。为此基于经典的R-矩阵理论,建立了适用于低能核反应的多道、多能级的约化R-矩阵理论来拟合几乎所有可用的16O系统的实验数据。配合使用协方差统计和误差传播理论,拟合外推得到了客观的、内部自恰的和唯一性好的12C（α,γ）16O反应天体物理S因子。总的外推S因子STOT（0.3 MeV）=162.7±7.3 keV·b,理论上首次给出达到恒星演化与元素核合成模型的最低要求的S因子。基于计算给出的全能区的S因子,数值积分给出了温度位于0.04 6 T₉ 6 10的12C（α,γ）16O天体物理反应率。在T₉=0.2处,推荐的反应率为（7.83 ±0.35）×10-15 cm3mol-1s-1。During stellar helium burning, the rates of 3α and the 12C(α,γ)16O reaction, in competition with one another, determine the relative abundances of 12C and 16O in a massive star. The abundance ratio is the beginning condition of the following nucleosynthesis and star evolution of massive stars, which are extremely sensitive to the rate of 12C(α,γ)16O reaction at T₉=0.2. The most direct and trustworthy way to obtain the reaction rate of the 12C(α,γ)16O reaction is to measure the S factor for that reaction to as low energy as possible, and to extrapolate to energies of astrophysical interest. Based on a new multilevel and multichannel reduced R-matrix theory for applications in nuclear astrophysics, we have obtained an accurate and self-consistent astrophysical S factor of 12C(α,γ)16O, by a global fitting for almost all available experimental data of 16O system, with the coordination of covariance statistics and error-propagation theory. The extrapolated S factor of 12C(α,γ)16O was obtained with a recommended value STOT (0.3 MeV)=162.7±7.3 keV·b. And the reaction rates of 12C(α,γ)16O for stellar temperatures between 0.04 6 T₉ 6 10 are provided. At T₉=0.2, the reaction rate is (7.83 ±0.35)×10-15 cm3mol-1s-1, where stellar helium burning occurs.     

Synthesis and magnetic properties of barium–calcium hexaferrite particles prepared by sol–gel and microemulsion techniques

The preparation of W-type hexaferrite particles with the composition BaCa₂Fe₁₆O₂₇ by microemulsion and a stearic acid sol–gel method with and without surfactant has been investigated at various sintering temperatures. The structural and magnetic characteristics have been studied by X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetric (DSC) and Fourier transform infrared (FTIR) techniques. The effect of sintering temperature on the properties of BaCa₂Fe₁₆O₂₇ hexaferrites has been studied. The value of saturation magnetization (M_s) depends on types of surfactant used. The sample prepared in the presence of polyoxyethylene (20) sorbitan monooleat (Tween 80) shows low saturation magnetization (M_s=15.10 emu/g), whereas the other sample prepared in the presence of a surfactant cetyltrimethylammonium bromide (CTAB) exhibits high saturation magnetization (M_s=24.60 emu/g) compared to the normal sample.     

Voltage-induced modification in magnetic coercivity of patterned Co50Fe50 thin film on piezoelectric substrate

A controlled modulation of magnetic properties through the inverse piezoelectric (PE) effect was investigated by means of the magneto-optical Kerr effect magnetometry in a periodic array of ferromagnetic (FM) Co₅₀Fe₅₀ stripes patterned on a commercial PE substrate. The coercive field (_Hc)$(H_{\mathrm{c}})$ rise (up to 80% in virgin cycle and 25% in subsequent cycles) when a DC electric field (up to 75 kV/cm) is applied on the PE substrate manifests a magnetoelectric coupling between the PE substrate and adjacent FM layer. The electric field dependence of _Hc$H_{\mathrm{c}}$ resembles the shear strain response to electric field of the PE constituent. The differences in the hysteresis loops shape when the magnetic field is oriented parallel and perpendicular to the stripes, reveal the interplay of the shape and stress anisotropy of the ferromagnet. Besides the inherent difficulties on constructing, an epitaxial hybrid system is a promising candidate of future random access memories designation.     

Complete and incomplete fusion studies in7Li and16O induced reactions on51V by measurement of excitation functions and recoil ranges

Excitation function and mean projected recoil ranges of nuclei produced in the⁷Li and¹⁶O induced reactions on⁵¹V target were measured by conventional stacked foil and thick-target thick-recoil-catcher technique for bombarding energiesE ≤ 50.0 MeV for⁷Li ions andE ≃ 60.0-96.0 MeV for the¹⁶O ions. The measured recoil ranges are converted to momentum transfer. The momentum transfer information was used to get clues about some aspects of the interaction such as complete and incomplete fusion reaction mechanism which correspond to full and reduced momentum transfer respectively. The measured excitation functions are compared with the calculation based on the statistical model which describes only equilibrium decay of the compound nucleus using the CASCADE code. The comparison of the CASCADE code with the measured excitation functions for the residue radioisotopes⁵¹Cr and⁵⁴Mn for the⁷Li +⁵¹V system indicates the reaction mechanisms is complete fusion of⁷Li with the target nucleus⁵¹V. Similarly the comparison of the CASCADE code with the measured excitation functions of the residue radioisotopes for the system¹⁶O +⁵¹ V indicates that the four reaction mechanisms (i) complete fusion of¹⁶O, (ii) incomplete fusion of¹²C, (iii) incomplete fusion of⁸Be and (iv) incomplete fusion of⁴He respectively with the target might be contributing to reaction cross sections.     

SBA-16薄膜内生长碳纳米管阵列及其Fe的填充

以表面活性剂F-127、导电玻璃(ITO)为基底制备了三维体心立方结构(Im3m)的介孔SBA-16膜.该膜的(111)晶面垂直于ITO基底.采用电化学沉积技术将少量Fe沉积进入SBA-16膜的孔底,沉积Fe后的SBA-16膜于700℃下乙炔裂解生长碳纳米管,在SBA-16膜(孔)内生长直径均匀、间距相等的开口碳纳米管阵列.采用二次电沉积法可以制备高度有序的填充Fe的碳纳米管阵列.TEM的研究结果表明填充进碳纳米管的Fe具有单晶结构.     

Differential smoothness of skew polynomial rings

It is shown that, under some natural assumptions, the tensor product of differentially smooth algebras and the skew-polynomial rings over differentially smooth algebras are differentially smooth.