Energy transfer of highly vibrationally excited azulene. II. Photodissociation of azulene-Kr van der Waals clusters at 248 and 266 nm

Photodissociation of azulene-Kr van der Waals clusters at 266 and 248 nm was studied using velocity map ion imaging techniques with the time-sliced modification. Scattered azulene molecules produced from the dissociation of clusters were detected by one-photon vacuum ultraviolet ionization. Energy transfer distribution functions were obtained from the measurement of recoil energy distributions. The distribution functions can be described approximately by multiexponential functions. Fragment angular distributions were found to be isotropic. The energy transfer properties show significantly different behavior from those of bimolecular collisions. No supercollisions were observed under the signal-to-noise ratios S/N=400 and 100 at 266 and 248 nm, respectively. Comparisons with the energy transfer of bimolecular collisions in thermal systems and the crossed-beam experiment within detection limit are made.     

A nonuniform L2 formula of Caputo derivative and its application to a fractional Benjamin–Bona–Mahony-type equation with nonsmooth solutions

To recover the full accuracy of discretized fractional derivatives, nonuniform mesh technique is a natural and simple approach to efficiently resolve the initial singularities that always appear in the solutions of time-fractional linear and nonlinear differential equations. We first construct a nonuniform L2 approximation for the fractional Caputo's derivative of order 1 < α < 2 and present a global consistency analysis under some reasonable regularity assumptions. The temporal nonuniform L2 formula is then utilized to develop a linearized difference scheme for a time-fractional Benjamin–Bona–Mahony-type equation. The unconditional convergence of our scheme on both uniform and nonuniform (graded) time meshes are proven with respect to the discrete H¹-norm. Numerical examples are provided to justify the accuracy.     

Super-strong RKA secure MAC,PKE and SE from tag-based hash proof system

\(\mathcal {F}\)-related-key attacks (RKA) on cryptographic systems consider adversaries who can observe the outcome of a system under not only the original key, say k, but also related keys f(k), with f adaptively chosen from \(\mathcal {F}\) by the adversary. In this paper, we define new RKA security notions for several cryptographic primitives including message authentication code (MAC), public-key encryption (PKE) and symmetric encryption (SE). This new kind of RKA notions are called super-strong RKA securities, which stipulate minimal restrictions on the adversary’s forgery or oracle access, thus turn out to be the strongest ones among existing RKA security requirements. We present paradigms for constructing super-strong RKA secure MAC, PKE and SE from a common ingredient, namely Tag-based hash proof system (THPS). We also present constructions for THPS based on the k-linear and the DCR assumptions. When instantiating our paradigms with concrete THPS constructions, we obtain super-strong RKA secure MAC, PKE and SE schemes for the class of restricted affine functions \(\mathcal {F}_{\text {raff}}\), of which the class of linear functions \(\mathcal {F}_{\text {lin}}\) is a subset. To the best of our knowledge, our MACs, PKEs and SEs are the first ones possessing super-strong RKA securities for a non-claw-free function class \(\mathcal {F}_{\text {raff}}\) in the standard model and under standard assumptions. Our constructions are free of pairing and are as efficient as those proposed in previous works. In particular, the keys, tags of MAC and ciphertexts of PKE and SE all consist of only a constant number of group elements.     

A linearized second-order scheme for nonlinear time fractional Klein-Gordon type equations

We consider difference schemes for nonlinear time fractional Klein-Gordon type equations in this paper. A linearized scheme is proposed to solve the problem. As a result, iterative method need not be employed. One of the main difficulties for the analysis is that certain weight averages of the approximated solutions are considered in the discretization and standard energy estimates cannot be applied directly. By introducing a new grid function, which further approximates the solution, and using ideas in some recent studies, we show that the method converges with second-order accuracy in time.     

A new xanthone from <Emphasis Type="Italic">Penicillium oxalicum</Emphasis>

A new tetrasubstituted xanthone (6,8-dihydroxy-3-methyl-9-oxo-9H-xanthene-1-carboxylic acid), together with four known compounds, was isolated from the EtOAc extract of Penicillium oxalicum. Their structures were elucidated by spectrometric and chemical methods, including ESI-MS and one- and two-dimensional NMR experiments.     

Synthesis of high-quality single-walled carbon nanotubes by catalytic decomposition of C2H2

High-quality single-walled carbon nanotubes free of defects and amorphous carbon coating have been produced by catalytic decomposition of C2H2 over Fe-Mo/Al2O3 catalyst.     

一种新的颜色视觉检测方法

利用计算机控制的彩色图形系统来测试人眼对颜色的感受能力,通过判断“Ｅ”形图的开口方向来检测色觉辨别力,能够较方便准确的划分色盲的种类,定量地划分色觉缺陷的等级,同时也为推动颜色视觉理论的深入研究作了一些初步的尝试。     

Composites prepared by penetrating poly(ethylene oxide) chains into mesoporous silica

Mesoporous silica was synthesized by hydrolysis of tetraethylorthosilicate (TEOS, formula Si(OCH₂CH₃)₄) at ambient temperature in a basic ethanol-water solution, with cetyltrimethyl ammonium bromide as a template. It had a surface area of approximately 1,400 m²/g, and an average pore diameter of approximately 40 Å. Portions were blended into three samples of poly(ethylene oxide) (PEO) of varying molecular weights, in the hope of making novel composites by penetrating some of the PEO chains into the silica channels. Differential Scanning Calorimetry (DSC) and X-ray diffraction (XRD) were used to characterize the structures of the PEO/mesoporous silica composites after they were held at 100 °C for up to 30 min. In both experiments, the melting temperature of the PEO decreased and ultimately disappeared. These results suggest that the PEO chains did penetrate into the silica pores, and since they were constrained in the pores, their crystallization was suppressed. This provides an interesting parallel to the disappearance of the glass transition temperatures of polymers constrained in the cavities of zeolites or in the galleries of intercalated clays.     

Electrogenerated Chemiluminescence Ethanol Biosensor Based on Carbon Nanotube‐Titania‐Nafion Composite Film

Mesoporous titania‐Nafion composite doped with carbon nanotube (CNT) has been used for the immobilization of tris(2,2′‐bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) and alcohol dehydrogenase on an electrode surface to yield a highly sensitive and stable electrogenerated chemiluminescence (ECL) ethanol biosensor. The presence of CNT in the composite film increases not only the sensitivity of the ECL biosensor but also the long‐term stability of the biosensor. The present biosensor responds linearly to ethanol in the wide concentration ranges from 1.0×10^?5 M to 1.0×10^?1 M with a detection limit of 5.0×10^?6 M (S/N=3). The present ECL ethanol biosensor exhibited higher ECL response compared to that obtained with the ECL biosensor based on the corresponding composite without CNT. The present CNT‐based ECL biosensor showed good long‐term stability with 75% of its initial activity retained after 2 weeks of storage in 50 mM phosphate buffer at pH 7.0.