The Signless Laplacian Spectral Radius of Some Strongly Connected Digraphs

Let \(\vec G\) be a strongly connected digraph and Q( \(\vec G\)) be the signless Laplacian matrix of \(\vec G\). The spectral radius of Q(\(\vec G\)) is called the signless Lapliacian spectral radius of \(\vec G\). Let \({\tilde \infty _1}\)-digraph and \({\tilde \infty _2}\)-digraph be two kinds of generalized strongly connected 1-digraphs and let \({\tilde \theta _1}\)-digraph and \({\tilde \theta _2}\)-digraph be two kinds of generalized strongly connected µ-digraphs. In this paper, we determine the unique digraph which attains the maximum(or minimum) signless Laplacian spectral radius among all \({\tilde \infty _1}\)-digraphs and \({\tilde \theta _1}\)-digraphs. Furthermore, we characterize the extremal digraph which achieves the maximum signless Laplacian spectral radius among \({\tilde \infty _2}\)-digraphs and \({\tilde \theta _2}\)-digraphs, respectively.     

5 + 1] annulation: a synthetic strategy for highly substituted phenols and cyclohexenones

A novel [5 + 1] annulation strategy is developed for the synthesis of highly substituted phenols and cyclohexenones from alpha-alkenoyl ketenedithioacetals and nitroalkanes.     

双折射光纤传输特性与偏振状态的实验研究

本文对两种不同结构双折射光纤的偏光特性进行了实验研究。测试了它们传输损耗与入射光偏振状态的关系及光纤不同曲率对传输导模的影响。给出了测试装置和测试原理,并对结果进行了分析。     

A new organically templated vanadium tellurite: (H2dien)[(VO2)(TeO3)]2·2H2O (dien is diethylenetriamine)

A new organically templated vanadium tellurite, poly[2,2′‐iminodiethanaminium [hexa‐μ₂‐oxido‐tetraoxidoditellurium(IV)divanadium(V)] dihydrate], {(C₄H₁₅N₃)[Te₂V₂O₁₀]·2H₂O}_n, features the interconnection of distorted [VO₅] trigonal bipyramids by bridging [TeO₃] pyramids, leading to a two‐dimensional corrugated anionic layer with an interlayer distance of about 13.47 Å. The interlayer space is occupied by doubly protonated diethylenetriamine cations (H₂dien) and guest water molecules. The two terminal amino groups of H₂dien are protonated, while the middle amino group, located on a twofold rotation axis, is not protonated. All the three amino groups and water molecules are involved in hydrogen‐bonding interactions. The compound represents a new member in the series (H₂am)[(VO₂)(TeO₃)]₂·xH₂O, where H₂am represents a doubly protonated diamine. Similarities and differences between the structures of members of the series are discussed.     

6.2-W deep blue light generation by intracavity frequency-doubled Nd:GdVO4 using BiBO

Efficient continuous-wave (CW) intracavity frequency doubling of a diode-end-pumped Nd:GdVO4 laser operating on 4F3/2 - 4I9/2 transitions at 912 nm has been demonstrated. A symmetrical cavity with two laser rods is designed, which divides the pump power between the two laser rods, allowing for greater power scalability. An 18-mm-long BiBO crystal, cut for critical type Ⅰ phase matching, is used for the intracavity frequency-doubled laser. A maximum output power of 6.2 W in the blue spectral range at 456 nm has been achieved with the pump power of 36 W. The beam quality M2 value is 2.5 in both horizontal and vertical directions. The ellipticity of the deep blue laser is 0.98, and the power stability is better than 3.2% at the maximum output power.     

Difluoroacetaldehyde N-Triftosylhydrazone (DFHZ-Tfs) as a Bench-Stable Crystalline Diazo Surrogate for Diazoacetaldehyde and Difluorodiazoethane

Despite the growing importance of volatile functionalized diazoalkanes in organic synthesis, their safe generation and utilization remain a formidable challenge because of their difficult handling along with storage and security issues. In this study, we developed a bench-stable difluoroacetaldehyde N-triftosylhydrazone (DFHZ-Tfs) as an operationally safe diazo surrogate that can release in situ two low-molecular-weight diazoalkanes, diazoacetaldehyde (CHOCHN₂) or difluorodiazoethane (CF₂HCHN₂), in a controlled fashion under specific conditions. DFHZ-Tfs has been successfully employed in the Fe-catalyzed cyclopropanation and Doyle–Kirmse reactions, thus highlighting the synthetic utility of DFHZ-Tfs in the efficient construction of molecule frameworks containing CHO or CF₂H groups. Moreover, the reaction mechanism for the generation of CHOCHN₂ from CF₂HCHN₂ was elucidated by density functional theory (DFT) calculations.     

Decarbonylative CC Bond‐Forming Reactions of Saccharins by Nickel Catalysis: Homocoupling and Cycloaddition

Decarbonylation of saccharins by nickel catalysis enables two kinds of C?C bond‐forming reactions; homocoupling of saccharins to form biaryls and cycloaddition with alkynes to form benzosultams. The former represents the first reported nickel‐catalyzed decarbonylative C?C homocoupling reaction, whereas the latter constitutes a powerful method to pharmaceutically relevant benzosultams. The reactions proceed with good functional‐group tolerance and excellent regioselectivity.     

Multimodal imaging probes based on Gd-DOTA conjugated quantum dot nanomicelles

Recently, multimodal nanoparticles integrating dual- or tri-imaging modalities into a single hybrid nanosystem have attracted plenty of attention in biomedical research. Here, we report the fabrication of two types of multimodal micelle-encapsulated nanoparticles, which were systematically characterized and thoroughly evaluated in terms of their imaging potential and biocompatibility. Optical and magnetic resonance (MR) imaging probes were integrated by conjugating DOTA-gadolinium (Gd) derivative to quantum dot based nanomicelles. Two amphiphilic block copolymer micelles, amine-terminated mPEG-phospholipid and amine-modified Pluronic F127, were chosen as the capping agents because of their excellent biocompatibility and ability to prevent opsonization and prolong circulation time in vivo. Owing to their different hydrophobic-hydrophilic structure, the micellar aggregates exhibited different sizes and protection of core QDs. This work revealed the differences between these nanomicelles in terms of the stability over a wide range of pH, along with their cytotoxicity and the capacity for chelating gadolinium, thus providing a useful guideline for tailor-making multimodal nanoparticles for specific biomedical applications.