Convergence analysis of a minimax method for finding multiple solutions of hemivariational inequality in Hilbert space

In 2013, a minimax method for finding saddle points of locally Lipschitz continuous functional was designed (Yao Math. Comp. 82 2087–2136 2013). The method can be applied to numerically solve hemivariational inequality for multiple solutions. Its subsequence and sequence convergence results in functional analysis were established in the same paper. But, since these convergence results do not consider discretization, they are not convergence results in numerical analysis. In this paper, we point out what approximation problem is, when this minimax method is used to solve hemivariational inequality and the finite element method is used in discretization. Computation of the approximation problem is discussed, numerical experiment is carried out and its global convergence is verified. Finally, as element size goes to zero, convergence of solutions of the approximation problem to solutions of hemivariational inequality is proved.     

High-peak-power,high-repetition-rate LD end-pumped Nd:YVO<Subscript>4</Subscript> burst mode laser

A compact high-peak-power, high-repetition-rate burst mode laser is achieved by an acousto-optical Q-switched Nd:YVO₄ 1064 nm laser directly pumped at 878.6 nm. Pulse trains with 10–100 pulses are obtained using acousto-optical Q-switch at repetition rates of 10–100 kHz under a pulsed pumping with a 1 ms duration. At the maximum pump energy of 108.5 mJ, the pulse energy of 10 kHz burst mode laser reaches 44 mJ corresponding to a single pulse energy of 4.4 mJ and an optical-to-optical efficiency of 40.5 %.The maximum peak power of ~468.1 kW at 10 kHz is obtained with a pulse width of 9.4 ns. The beam quality factor is measured to be M ² ~1.5 and the pulse jitter is estimated to be less than 1 % in both amplitude and time region.     

A colorimetric anion receptor containing the <Emphasis Type="Italic">cis</Emphasis>-Ru(bipy)<Subscript>2</Subscript><Superscript>2+</Superscript> group

When one or more nitro groups are incorporated into an anion receptor, intramolecular proton transfer from nearby –NH groups often takes place and is a significant obstacle for the construction of supramolecular systems. In this paper, by employing an intramolecular hydrogen bond between –NH and nitro groups in order to reduce the acidity of the amide group, we were able to construct a receptor that formed stable supramolecular systems. The receptor forms a 1:2 supramolecular compound with fluoride, whereas 1:1 complexes were formed with AcO⁻ and H₂PO₄ ⁻ in DMSO solution. Using this system, an easy-to-prepare test paper for the detection of F⁻ in low concentration at (10⁻⁴ M) in water was developed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

基于3D⁃DIC技术的约束岩石裂缝扩展研究

采用 RMT-301B岩石与混凝土力学实验系统对施加预应力值为峰值强度 20 %、40 %、60 %的泥质白云 岩进行单轴压缩实验,并借助三维数字图像相关技术(3D-DIC)测试系统观测受约束岩石试样的变形和破坏形 态,研究泥质白云岩在约束条件下的位移场和 Tresca应变场的演化过程．结果表明：(1) 岩石的破坏过程是由 内向外扩展,当应力积累超出岩石承受范围后,岩石出现裂纹,随后裂纹尖端继续扩展,应力也发生了重分 布,岩石内部多组裂纹开始联合扩展、贯穿,直到试件发生完全破坏．(2) 含约束岩石在单轴压缩下一共有轴 向劈裂破坏、沿片理破坏、Y形破坏、共轭剪切破坏四种破坏形态,且以轴向劈裂破坏为主     

Bio-switchable optofluidic lasers based on DNA Holliday junctions

Bio-switchable optofluidic lasers based on DNA Holliday junctions were demonstrated. Nearly 100% wavelength switching was achieved through reversible conformational change of the Holliday junction controlled by magnesium ionic strength.     

Rapid, sensitive, and multiplexed on-chip optical sensors for micro-gas chromatography

We developed and characterized a rapid, sensitive and integrated optical vapor sensor array for micro-gas chromatography (μGC) applications. The sensor is based on the Fabry-Pérot (FP) interferometer formed by a micrometre-thin vapor-sensitive polymer layer coated on a silicon wafer. The thickness and the refractive index of the polymer vary in response to the vapor analyte, resulting in a change in the reflected intensity of the laser impinged on the sensor. In our study, four different polymers were coated on four wells pre-etched on a silicon wafer to form a spatially separated sensor array. A CMOS imager was employed to simultaneously monitor the polymers' response, thus enabling multiplexed detection of a vapor analyte passing through the GC column. A sub-second detection time was demonstrated. In addition, a sub-picogram detection limit was achieved, representing orders of magnitude improvement over the on-chip vapor sensors previously reported.     

The effects of Gd3+ substitution on the crystal structure, site symmetry, and photoluminescence of Y/Eu layered rare-earth hydroxide (LRH) nanoplates

Well crystallized nanoplates of the (Y(0.95-x)Gd(x)Eu(0.05))(2)(OH)(5)NO(3)·nH(2)O ternary layered rare-earth hydroxides (LRHs), synthesized hydrothermally, have been investigated with emphasis on the effects of Gd(3+) substitution for Y(3+) on the structural features and optical properties. Characterizations of the materials were achieved by the combined techniques of XRD, FT-IR, TEM, DTA/TG, and optical spectroscopies. The results showed that Gd(3+) substitution leads to linearly expanded ab plane, shortened interlayer distance (c/2), and reduced hydration (smaller n value) of the crystal structure. As a consequence, the Ln(3+) partially shifts from the C(4v) to C(1) site symmetries and thus leads to systematically altered photoluminescence behaviors. Under the (7)F(0)→(5)L(6) transition excitation of Eu(3+) at 394 nm, both the (5)D(0)→(7)F(2) to (5)D(0)→(7)F(4) and the 595 nm (5)D(0)→(7)F(1) to 590 nm (5)D(0)→(7)F(1) intensity ratios linearly increase towards a higher Gd(3+) content. The incorporated Gd(3+) cations selectively sensitize emission from the C(1)-site Eu(3+) and produce a new charge transfer (CT) excitation band at ～254 nm. With this, the desired 615-nm red emission is obtainable either under intra-4f(6) transition excitation of Eu(3+) or by exciting the CT band. The materials have similar fluorescence lifetimes of 0.85 ± 0.05 ms for the 615-nm emission, irrespective of the Gd(3+) content and excitation wavelength.     

Efficient chiral monophosphorus ligands for asymmetric Suzuki-Miyaura coupling reactions

A series of novel P-chiral monophosphorus ligands exhibit efficiency in asymmetric Suzuki-Miyaura coupling reactions, enabling the construction of an array of chiral biaryl products in high yields and excellent enantioselectivities (up to 96% ee) under mild conditions. The carbonyl-benzooxazolidinone moiety in these chiral biaryl products allows facile derivatization for further synthetic applications. A computational study has revealed that a π-π interaction between the two coupling partners can enhance the enantioselectivity of the coupling reaction.     

Enhancement of photoresponse properties of conjugated polymers/inorganic semiconductor nanocomposites by internal micro-magnetic field

In this paper, the effect of the internal micro-magnetic field (IMMF) on the photocurrent property of conjugated polymer/inorganic semiconductor nanocomposites is reported and analyzed. By using the redox reaction, magnetic Fe(3)O(4) nanoparticles were coated on the surface of highly active nanorods of conjugated polyaniline (PANI), forming an internal micro-magnetic electron donor (i.e., Fe(3)O(4)@PANI). After subsequent incorporation of CdS nanoparticles (serving as electron acceptors), the power conversion efficiency (PCE) of the system (Fe(3)O(4)@PANI-CdS) was found to be as high as 3.563%, contrasting sharply with the value (1.135%) of the hybrid without Fe(3)O(4) (PANI-CdS). This obvious enhancement originated from the fact that the IMMF increased the number of singlet polaron pairs through field-dependent intersystem crossing (ISC), giving a positive contribution to the photocurrent generation. Additionally, the dependence of the photocurrent on the remnant magnetization of the Fe(3)O(4)@PANI-CdS nanocomposites was investigated. A percolation behavior was observed, which was due to the appearance of interpenetrating networks consisting of donor and acceptor phases, leading to the recombination of charge carriers through trapping. The outcomes of the present work might help to produce a new family of conjugated organic/inorganic semiconductor nanocomposites with designed optoelectronic performances.     

Caerulomycins and collismycins share a common paradigm for 2,2'-bipyridine biosynthesis via an unusual hybrid polyketide-peptide assembly Logic

Caerulomycins (CAEs) and collismycins (COLs), which mainly differ in sulfur decoration, are two groups of structurally similar natural products containing a 2,2'-bipyridine (2,2'-BP) core, derivatives of which have been widely used in chemistry. The biosynthetic pathways of CAEs and COLs remain elusive. In this work, cloning of the CAE biosynthetic gene cluster allowed us to mine a highly conserved gene cluster encoding COL biosynthesis in a Streptomyces strain that was previously unknown as a 2,2'-BP producer. In vitro and in vivo investigations into the biosynthesis revealed that CAEs and COLs share a common paradigm featuring an atypical hybrid polyketide synthase/nonribosomal peptide synthetase system that programs the 2,2'-BP formation. This likely involves an unusual intramolecular cyclization/rearrangement sequence, and a difference in processing of the sulfhydryl group derived from the same precursor cysteine drives the biosynthetic route toward CAEs or COLs.