Spectroscopy and crystal-field analysis of Cr4+-doped transparent silicate glass-ceramics

We report transparent Cr⁴⁺-doped SiO₂–Al₂O₃–ZnO–Li₂O–K₂O glass-ceramics with broadband infrared luminescence. After heart-treatment, Li₂ZnSiO₄ crystallite was precipitated in the glasses, and its average size increased with increasing heat-treatment temperature. Racah parameters of Cr⁴⁺–Li₂ZnSiO₄ glass-ceramics have been calculated, and it was confirmed from absorption spectra that the energy levels of Cr⁴⁺-doped glass-ceramics are close to the cross point ¹E and ³T states. No infrared emission was detected in the as-made glass samples, but the broadband infrared emission centered at 1210 nm with the full width at half maximum (FWHM) of more than 250 nm was observed by exciting the glass-ceramics with excitation of an 808 nm laser diode. In order to analyze the located crystal field of Cr⁴⁺ ions, the emission spectra are fitted by multi-peak Gauss fitting. It is seen that the fluorescence spectra are fitted into two Gaussian bands at around 1195 and 1263 nm with band widths of 208 and 278 nm, respectively. The two Gaussian bands at around 1195 and 1263 nm have about the same decay rate, and hence they would probably originate from the same luminescent centers. The observed infrared emission could be attributed to Cr⁴⁺ ions at low-field sites in Li₂ZnSiO₄ glass-ceramics.     

Primitive non-powerful sign pattern matrices with base 2

A sign pattern matrix M with zero trace is primitive non-powerful if for some positive integer k, M ^k ?=?J _#. The base l(M) of the primitive non-powerful matrix M is the smallest integer k. By considering the signed digraph S whose adjacent matrix is the primitive non-powerful matrix M, we will show that if l(M)?=?2, the minimum number of non-zero entries of M is 5n???8 or 5n???7 depending on whether n is even or odd.     

L~Φ可料控制鞅Hardy-Orlicz空间之间的鞅变换

以鞅变换为工具,刻画了L^Φ可料控制鞅的Hardy-Orlicz空间之间的相互关系,设Φ₁和Φ₂是两个Young函数,并在某种意义上Φ₂强于Φ1（具体定义见正文）,以构造性的方法证明了Hardy-Orlicz空间D_Φ1中的鞅恰好是Hardy-Orlicz空间D_Φ2中的鞅的鞅变换.所得的结果推广了已有文献中的相关结论.     

Solutions of nonlinear thickness-shear vibrations of an infinite isotropic plate with the homotopy analysis method

As a preliminary attempt for the study on nonlinear vibrations of a finite crystal plate, the thickness-shear mode of an infinite and isotropic plate is investigated. By including nonlinear constitutive relations and strain components, we have established nonlinear equations of thickness-shear vibrations. Through further assuming the mode shape of linear vibrations, we utilized the standard Galerkin approximation to obtain a nonlinear ordinary differential equation depending only on time. We solved this nonlinear equation and obtained its amplitude–frequency relation by the homotopy analysis method (HAM). The accuracy of the present results is shown by comparison between our results and the perturbation method. Numerical results show that the homotopy analysis solutions can be adjusted to improve the accuracy. These equations and results are useful in verifying the available methods and improving our further solution strategy for the coupled nonlinear vibrations of finite piezoelectric plates.     

Spiro[pyrrolidine-2,3′-oxindole] derivatives synthesized by novel regionselective 1,3-dipolar cycloadditions

A series of spiro-oxindole derivatives was synthesized by novel regioselective 1,3-dipolar cycloadditions of isatin, α-amino acids, and (E)-β-aryl-nitro-olefins. Regioisomers were produced in each reaction and the major products showed different regioselectivity compared to previously reported spiro-oxindole derivatives.     

杭州市冬季大气气溶胶PM2.5中二恶英和多氯联苯的污染特征

2014年1月在杭州市选择5个点位采集大气颗粒物PM_2.5样品,采用同位素稀释高分辨气相色谱/高分辨质谱测定PM_2.5中的二恶英（PCDD/Fs）和多氯联苯（PCBs）,对PM_2.5的污染状况以及PM_2.5中PCDD/Fs和PCBs的污染水平及分布特征进行了研究。PM_2.5的质量浓度范围为85~168 μg/m³,PM_2.5污染较重,但与2004年同期相比明显降低。PM_2.5中PCDD/Fs的毒性当量（TEQ）为0.277~0.488 pg I-TEQ/m³,明显高于2004年同期采集样品。颗粒物中PCDD/Fs以八氯代二苯并-对-二恶英（OCDD）为主,毒性当量主要贡献者为2,3,4,7,8-五氯代二苯并呋喃（2,3,4,7,8-PeCDF）。PM_2.5中PCBs的质量浓度范围为2.9~8.1 pg/m³,二恶英类多氯联苯（DL-PCBs）的毒性当量范围为2.6~6.1 fg WHO-TEQ/m³,污染较低。PCBs在颗粒物中分布以PCB-28为主,但对毒性当量贡献最大的为PCB-126。PCDD/Fs和PCBs的气-固分配特征表现为PCDD/Fs主要分布于颗粒物中,而PCBs主要分布于气相中。     

All hypoenergetic graphs with maximum degree at most 3

The energy E(G) of a graph G is defined as the sum of the absolute values of its eigenvalues. A connected graph G of order n is said to be hypoenergetic if E(G)<n. All connected hypoenergetic graphs with maximum degree Δ3 have been characterized. In addition to the four (earlier known) hypoenergetic trees, we now show that complete bipartite graph K_2,3 is the only hypoenergetic cycle-containing hypoenergetic graph. By this, the validity of a conjecture by Majstorović et al. has been confirmed.     

Synthesis, crystal structure and in vitro antibacterial activity of two novel silver(I) complexes

Two silver(I) complexes [Ag₂(dppm)₂(L¹)₂(CH₂Cl₂)₂] (1) and [Ag₄(dppm)₂(L²)₂(NO₃)₂] (2) have been prepared by the reactions of [Ag₂(dppm)₂(NO₃)₂] with HL¹ and HL² [dppm = bis(diphenylphosphino)methane, HL¹ = 2-(9H-carbazol-9-yl) acetic acid and HL² = (E)-3-(4-(9H-carbazole-9-yl) phenyl) acrylic acid], respectively. Both complexes have been structurally characterized by X-ray crystallography, confirming that 1 is a binuclear complex whereas 2 is a tetranuclear one. Both complexes were assayed for antibacterial activity against two Gram-positive bacterial strains (Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 6538) and two Gram-negative bacterial strains (Pseudomonas aeruginosa ATCC 13525 and Escherichia coli ATCC 35218) by MTT method. Complex 2 exhibited powerful antibacterial activities against B. subtilis ATCC 6633 with MIC of 0.78 μg/mL, which was superior to the positive controls penicillin G. On the basis of the biological results, structure-activity relationships were discussed.     

Chemiluminescence mechanisms of cerium-norfloxacin and its application in urine analysis

In this article, novel chemiluminescence mechanisms between norfloxacin and cerium(IV) in an acidic medium were studied. Chemiluminescence spectra of the present system were recorded observing three maximum emissions at about 475 nm, 550 nm, and 620 nm, respectively. The results indicate that the chemiluminescence peaks located at 475 nm and 620 nm can be ascribed to the emission of a singlet oxygen, while the chemiluminescence emission at 550 nm occurred in course of the reaction between acidic cerium(IV) and the phenolic intermediate. Under optimum conditions, the chemiluminescence intensity was linear with the concentration of norfloxacin over the range of 2.0 × 10⁻⁸−1.0 × 10⁻⁵ g mL⁻¹ and the detection limit of 1.0 × 10⁻⁸ g mL⁻¹ (S/N = 3). The relative standard deviation was 1.94 % for a 4.0 × 10⁻⁷ g mL⁻¹ norfloxacin solution considering eleven repeated measurements. The present chemiluminescence system was successfully applied in the determination of norfloxacin in pharmaceutical preparations and concentration-time profiles in urine.     

气体膨胀液体技术制备纳米微粒研究进展

近年来,利用气体膨胀液体的相行为已经开发了许多气体膨胀液体微粒制备方法,并已在制备无机、有机材料、有机金属固体、医药、电子等方面的微细颗粒方面得到广泛应用。本文介绍了气体膨胀液体制备纳米颗粒的研究和应用进展。