Ring Bridge Research Articles

Anisotropic Conductivity at the Single-Molecule Scale.

In most junctions built by wiring a single molecule between two electrodes, the electrons flow along only one axis: between the two anchoring groups. However, molecules can be anisotropic, and an orientation-dependent conductance is expected. Here, we fabricated single-molecule junctions by using the electrode potential to control the molecular orientation and access individual elements of the conductivity tensor. We measured the conductance in two directions, along the molecular plane as the benzene ring bridges two electrodes using anchoring groups (upright) and orthogonal to the molecular plane with the molecule lying flat on the substrate (planar). The perpendicular (planar) conductance is about 400 times higher than that along the molecular plane (upright). This offers a new method for designing a reversible room-temperature single-molecule electromechanical switch that controllably employs the electrode potential to orient the molecule in the junction in either "ON" or "OFF" conductance states.

Anisotropic Conductivity at the Single‐Molecule Scale

AbstractIn most junctions built by wiring a single molecule between two electrodes, the electrons flow along only one axis: between the two anchoring groups. However, molecules can be anisotropic, and an orientation‐dependent conductance is expected. Here, we fabricated single‐molecule junctions by using the electrode potential to control the molecular orientation and access individual elements of the conductivity tensor. We measured the conductance in two directions, along the molecular plane as the benzene ring bridges two electrodes using anchoring groups (upright) and orthogonal to the molecular plane with the molecule lying flat on the substrate (planar). The perpendicular (planar) conductance is about 400 times higher than that along the molecular plane (upright). This offers a new method for designing a reversible room‐temperature single‐molecule electromechanical switch that controllably employs the electrode potential to orient the molecule in the junction in either “ON” or “OFF” conductance states.

Structurally Diverse Sesquiterpenoids from the Endangered Ornamental Plant Michelia shiluensis.

A preliminary phytochemical investigation on the MeOH extract of the leaves and twigs of the endangered ornamental plant Michelia shiluensis led to the isolation of 16 sesquiterpenoids. The isolated compounds comprised germacrane- (1-4, 13, 14), guaiane- (5-9, 15), amorphane- (10), and eudesmane-type (11, 12, 16) sesquiterpenoids. The new structures (1-12) were elucidated by spectroscopic and computational methods, and their absolute configurations (except for 9) were assigned by single-crystal X-ray diffraction crystallographic data and/or electronic circular dichroism spectra. Shiluolides (A-D, 1-4) are unprecedented C16 or C17 homogermacranolides, and their putative biosynthetic pathways are briefly discussed. Shiluone D (8) is a rare 1,10- seco-guaiane sesquiterpenoid featuring a new ether-containing spirocyclic ring, whereas shiluone E (9) represents the first example of a 1,5-4,5-di- seco-guaiane with a rare 5,11 -lactone moiety. Shiluone F (10) is the first amorphane-type sesquiterpenoid possessing an oxetane ring bridging C-1 and C-7. Bioassay evaluations indicated that lipiferolide (13) showed noteworthy cytotoxicities toward human cancer cell lines MCF-7 and A-549, with IC50 values of 1.5 and 7.3 μM, respectively. Shiluone D (8) exerted inhibition against protein tyrosine phosphatase 1B (IC50: 46.3 μM).

Flow visualization of R32 in parallel-port microchannel tube

This paper presents visualization of two-phase flow of R32 in a parallel-flow microchannel tube with hydraulic diameter of 0.643 mm. Six visualization sections are installed in the facility, the same as in Li and Hrnjak (2017). Flow patterns are classified as: plug/slug, transitional, and annular flow. In plug/slug flow, a clear interface between liquid slug and vapor plug is observed. In transitional flow, the interface between slug and plug is broken and becomes a thick liquid ring and vapor bridge. In annular flow, only a liquid film is observed in the channel. The flow pattern map of R32 is reported. Mass flux changes from 50 to 300 kg-m−2s−1. The two-phase flow is generated by adding heat to subcooled refrigerant. The interface velocity and vapor plug length fraction (close to void fraction) are measured from high speed video. The velocity and vapor fraction agree to results based on a homogeneous assumption. When mass flux is 50 kg-m−2 s−1, the flow is always in plug/slug from vapor quality 0 to 1. Annular flow is observed at high quality when mass flux is higher than 100 kg-m−2 s−1. Transitional flow is observed when mass flux is higher than 150 kg-m−2 s−1, and it connects the plug/slug and annular flow patterns. Most flow pattern correlations fail to fit the measured flow pattern map. This is due to the difference in two-phase flow generation method and experimental conditions between this paper and the database used in correlations.

Prognostic utility of atypical mitoses in patients with breast cancer: A comparative study with Ki67 and phosphohistone H3

Emerging evidence suggests that the presence of atypical mitoses is associated with poor prognosis in some types of cancer, but its clinical significance remains uncertain. Here, we investigated the occurrence of atypical mitoses in breast cancers. Mitotic figures, including normal and atypical mitoses, were assessed in resected histological sections from 109 patients with invasive carcinoma of no special type (ICNST). Comparisons with clinicopathological features and biomarkers such as Ki67 and phosphohistone H3 (PHH3) were performed. The total number of mitotic figures, including atypical mitoses, was higher in situ and invasive ductal carcinoma components than in normal ducts. Morphological characteristics of atypical mitoses included multipolar, lagged, ring, asymmetrical mitoses, and anaphase bridge. Patients with higher total mitoses and PHH3, and the presence of atypical mitoses showed reduced overall survival (OS), compared to those with lower total mitoses and PHH3, and without atypicalmitoses (P = 0.03, 0.02,and <0.001, respectively). In multivariate analysis, the presence of atypical mitoses alone attained significant correlation with shorter OS (P < 0.001). Atypical mitoses in routinely resected specimens have a robust prognostic value for ICNST of the breast, but its clinical utility remains to be validated in a multicenter large material.

Dihydroindenofluorene Positional Isomers.

Bridged oligophenylenes are very important organic semiconductors (OSCs) in organic electronics (OE). The fluorene unit, which is a bridged biphenyl, is the spearhead of this class of materials and has, over the last 20 years, led to fantastic breakthroughs in organic light-emitting diodes. Dihydroindenofluorenes belong to the family of bridged terphenyls and can be viewed as the fusion of a fluorene unit with an indene fragment. Dihydroindenofluorenes have also appeared as very promising building blocks for OE applications. In the dihydroindenofluorene family, there are five positional isomers, with three different phenyl linkages ( para/ meta/ ortho) and two different ring bridge arrangements ( anti/ syn). We have focused on the concept of positional isomerism. Indeed, the structural differences of the dihydroindenofluorenyl cores lead to unusual electronic properties, which our group has described since 2006, thanks to the five dispirofluorene-indenofluorene positional isomers (dihydroindenofluorenes substituted on the bridges by fluorenyl units). 6,12-Dihydroindeno[1,2- b]fluorene (the para-anti isomer) is constructed on a p-terphenyl core and possesses an anti geometry. Although this isomer has been widely investigated over the last 20 years, studies of the four other isomers remain very scarce. 11,12-Dihydroindeno[2,1- a]fluorene (the para-syn isomer) is also built on a bridged p-terphenyl core but possesses a syn geometry. This particular geometry has been advantageously used by our group to drastically tune the electronic properties, and this isomer has emerged as a promising scaffold to obtain stable blue emission arising from conformationally controllable intramolecular excimers. These preliminary studies have shown the crucial influence of the geometry on the electronic properties of the dihydroindenofluorenes. Modification of the arrangement of the phenyl linkages from para to meta provides the meta isomers, namely, 7,12-dihydroindeno[1,2- a]fluorene (the meta-anti isomer) and 5,7-dihydroindeno[2,1- b]fluorene (the meta-syn isomer). With these two regioisomers, the strong impacts of both the linkage and the geometry on the electronic properties have been particularly highlighted over the years. The last positional isomer of the family is 5,8-dihydroindeno[2,1- c]fluorene, which possesses a central o-terphenyl backbone and a syn geometry. This isomer is unique because of its ortho linkage, which induces a particular helicoidal turn of the dihydroindenofluorenyl core. Using a structure-property relationship approach, in the present Account we describe the molecular diversity of the five dispirofluorene-indenofluorene positional isomers and the consequences both in terms of their organic synthesis and electronic properties. This Account shows how positional isomerism can be a powerful tool to tune the electronic properties of OSCs.

Spirobifluorene Regioisomerism: A Structure–Property Relationship Study

The present works report the first structure-property relationship study of a key class of organic semiconductors, that is, the four spirobifluorene positional isomers possessing a para-, meta- or ortho-linkage. The remarkable and surprising impact of the ring bridging and of the linkages on the electronic properties of the regioisomers has been particularly highlighted and rationalised. The impact of the ring bridging on the photophysical properties has been stressed with notably the different influence of the linkages and the bridge on the singlet and triplet excited states. The first member of a new family of spirobifluorenes substituted in the 1-position, which presents better performance in blue phosphorescent OLEDs than those of its regioisomers, is reported. These features highlight not only the great potential of 1-substituted spirobifluorenes, but also the remarkable impact of regioisomerism on electronic properties.

Synthesis of water-soluble palladium(ii) complexes with N-heterocyclic carbene chelate ligands and their use in the aerobic oxidation of 1-phenylethanol.

The synthesis of palladium(ii) complexes containing N-heterocyclic carbene chelate ligands is reported. These chelate ligands have methylene or ethylene ring bridges and sulfonate, carbonate or ammonium functionalities to render the complexes soluble in water. Bis- [(bis-NHC)PdX2] (X = Cl, Br or I) and tetra-carbene [(bis-NHC)2Pd] complexes have been prepared and the crystal structures of two of them have been determined. The NHC ligand is coordinated to the metal center in normal (C2-bound) or abnormal (C4-bound) mode. Processes involving the formation of NHC-Pd bonds or the transfer of NHC ligands have been explored in water. The behavior of the bis-carbene complexes as catalysts for the aerobic oxidation of 1-phenylethanol is also discussed.

Planar homotropenylium cation: a transition state with reversed aromaticity.

In contrast to the equilibrium structure of the homoaromatic C(s) homotropenylium cation, C8H9(+) (1), which supports a pinched diatropic ring current, the C(2v) transition state (2) for inversion of the methylene bridge of 1 is antiaromatic and supports a two-lobe paratropic π current, as detected by plotting B3LYP/6-31G** ipsocentric current maps. Participation of the bridge CH bonds is crucial for the change in global character of the current in the transition state, as shown by the quenching of its paratropicity on substitution of H by F. Orbital-based arguments allow rationalization of this transition between homoaromaticity and hyper(conjugative) antiaromaticity. More generally, the hyperconjugative ring current in a family of C(2v) planar-constrained geometries of (CR2)C(N-1)H(N-1)(q) homoannulenes (R = H, F) can be switched from paratropic (antiaromatic) to diatropic (aromatic) by variation of ring size, charge, and bridge substituent. An orbital-based counting rule accounts for these systematic trends.

Polarization, second-order nonlinear optical properties and electrochromism in 4H-pyranylidene chromophores with a quinoid/aromatic thiophene ring bridge

The second-order NLO responses and spectroelectrochemical properties of donor–π–acceptor systems featuring a quinoid/aromatic thiophene unit have been studied.

2-Pyridyl-phosphine and -diphosphine complexes of nickel(II), and their aqueous solution chemistry

The cis, square planar NiII complexes NiX2[d(py)pe], where d(py)pe is the 2-pyridyl-diphosphine ligand py2P(CH2)2Ppy2, and X=Cl (1a), Br (1b), I (1c), NCS, and NO3, and the corresponding d(py)pcp complexes, where d(py)pcp is ▪ with a cyclopentane ring bridge, are synthesized via use of the NiX2(PPh3)2 precursors, and fully characterized, including five X-ray structures. An X-ray structure of d(py)pcp is also reported.Complexes 1a–c dissolve in water to form cis-{Ni(H2O)2[d(py)pe]}2+, which is isolated as the PF6 salt; the d(py)pcp analogues behave similarly. All the diaquo complexes decompose slowly in H2O to generate Ni(H2O)62+ and the dioxides of the pyridyl-diphosphines, likely due to the presence of trace O2. Known, tetrahedral complexes of the type NiX2(PPh3−npyn)2 (X=Cl, Br; py=2-pyridyl, and n=1–3) also dissolve in H2O, again with generation of 2:1 electrolyte species. An attempted synthesis of Ni(CO)2(Ppy3)2 from Ni(CO)2(PPh3)2 and Ppy3 in CH2Cl2 accidentally gives the known NiCl2(P,N-Ppy3)·H2O via a laboratory light-induced reaction; this species partially converts into [Ni(Ppy3)2]Cl2, and a crystal structure confirms the octahedral, tripodal N,N′,N″-coordination of the cation. The water-soluble systems, studied because of their potential for catalysis in aqueous media, are not effective for catalyzed olefin hydration, or transfer-hydrogenation of cyclohexanone.

Small Molecular Donors for Organic Solar Cells Obtained by Simple and Clean Synthesis

A small donor-acceptor molecule is synthesized in a two-step procedure involving reaction of N,N-diphenylhydrazine on 2,5-diformylthiophene and Knoevenagel condensation. Results of UV/Vis absorption spectroscopy and cyclic voltammetry show that replacement of the phenyl ring bridge of a reference compound 2 by an azo group produces a slight red-shift of λmax, an enhancement of the molecular absorption coefficient, and a decrease of the energy level of the frontier orbitals. A preliminary evaluation of the potentialities of compound 1 as donor material in a basic bilayer planar heterojunction cell of 28 mm(2) active area using C60 as acceptor gave a short-circuit current density of 6.32 mA cm(-2) and a power conversion efficiency of 2.07 %.

Dependence of the Properties of Dihydroindenofluorene Derivatives on Positional Isomerism: Influence of the Ring Bridging

Angriff auf die Spitze: Die relative Position der Ringverbrückungen hat einen bemerkenswerten Einfluss auf die spektroskopischen Eigenschaften zweier isomerer verbrückter m-Terphenylderivate (siehe Bild). Die Aktivität dieser neuen organischen Halbleiter als Emissionsschicht in blauen organischen Leuchtdioden (OLEDs) ist fast so hoch wie bei den bisher aktivsten Dihydroindenofluoren-basierten OLEDs. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Dependence of the Properties of Dihydroindenofluorene Derivatives on Positional Isomerism: Influence of the Ring Bridging

Taking pole position: The relative position of the ring bridging has a unique and remarkable effect on the spectroscopic properties of dihydroindeno[1,2-a]/ [2,1-b]fluorenes (see picture). These blue-emitting positional isomers have been successfully used as the emitting layer in organic light-emitting diodes (OLEDs), with performance among the highest reported for dihydroindenofluorene-based OLEDs.

Application of Anchoring Concrete Filling Piles in Deep Foundation Pit Engineering at Zhengzhou North Freight Marshalling Station

This paper introduces the "Levels of anchor cable +Bored piles +Net shotcrete combined support plans application in deep foundation pit engineering at Zhengzhou north freight marshalling station. Construction practice and monitoring data show that the engineering supporting design and construction have got an ideal effect, to ensure the safety of the north Ring Bridge and the railway line. It has a certain guiding significance to similar municipal engineering.

Unusual Redox Chemistry of Ytterbium Carbazole–Bis(oxazoline) Compounds: Oxidative Coupling of Primary Phosphines by an Ytterbium Carbazole–Bis(oxazoline) Dialkyl

The 1,8-bis(4′,4′-dimethyloxazolin-2′-yl)-3,6-di-tert-butylcarbazole anion (Czx) forms monomeric, six-coordinate halide complexes of Yb(II), (Czx)Yb(X)(THF)2 (X = I (2), Cl (3)), by metathesis of YbX2 with NaCzx (1) or Na/Hg reduction of (Czx)Yb(Cl)2(THF). The crystal structure of 1 reveals a polymeric chain structure in which the oxazoline ring bridges to the Na+ of an adjacent unit. The iodo complex 2 serves as a precursor to divalent silylamide, alkyl, and phosphide complexes, (Czx)Yb(X)(THF)n (4, X = N(SiMe3)2, n = 1; 5, X = CH(SiMe3)2, n = 1; 7a, X = 2,4,6-Me3C6H2PH, n = 2; 7b, X = 2,4,6-Pri3C6H2PH, n = 2). The X-ray structure of 4 reveals a distorted-trigonal-bipyramidal geometry with the Czx ligand occupying two axial sites and one equatorial site in a pseudo-mer coordination mode. In contrast to the typical metathesis chemistry observed with LiCH(SiMe3)2, an unusual oxidation occurs when 2 or 3 is treated with LiCH2SiMe3 to generate the previously isolated trivalent alkyl (Czx)Yb(CH2SiMe3)2. Trivalent Yb complexes with the Czx ligand also display unusual redox chemistry: rapid reduction to the Yb(II) phosphides 7a,b is observed on treatment of mer,cis-(Czx)Yb(Cl)2(THF) with ArPH– Na+ (6a,b) or, equivalently, on treatment of (Czx)Yb(CH2SiMe3)2 with ArPH2. In both cases, oxidative coupling of the phosphide or phosphine was observed to form meso- and rac-biphosphines, ArPH–PHAr (Ar = 2,4,6-Me3C6H2 (9a), 2,4,6-Pri3C6H2 (9b)).

Synthesis of quaternary α-amino acid-based arginase inhibitors via the Ugi reaction

The Ugi reaction has been successfully applied to the synthesis of novel arginase inhibitors. In an effort to decrease conformational flexibility of the previously reported series of 2-amino-6-boronohexanoic acid (ABH) analogs 1, we designed and synthesized a series of compounds, 2, in which a piperidine ring is linked directly to a quaternary amino acid center. Further improvement of in vitro activity was achieved by adding two carbon bridge in the piperidine ring, that is, tropane analogs 11. These improvements in activity are rationalized by X-ray crystallography analysis, which show that the tropane ring nitrogen atom moves into direct contact with Asp202 (arginase II numbering). The synthetic routes described here enabled the design of novel arginase inhibitors with improved potency and markedly different physico-chemical properties compared to ABH. Compound 11c represents the most in vitro active arginase inhibitor reported to date.

Effects of Three Bridging Exercises on Local and Global Muscles of Middle Aged Women

[Purpose] This study investigated the muscle activity differences of three different lumbar stabilization exercises in a comparison of middle-aged and young women. [Subjects] Seventeen middle-aged women and fifteen young women were enrolled in this study. Patients with a history of any neurologic disorders, orthopedic disorders, or cardiopulmonary problems that would have affected their lumbar stabilization exercise performance were excluded. [Methods] All subjects performed 3 exercises while the surface electromographic activity was recorded of the rectus abdominis, internal oblique, multifidus, and iliocostalis lumbolum. The mean electromyographic amplitudes obtained during the exercise were normalized to the amplitude of maximal voluntary isometric contraction (%MVIC) to produce an inter-individually comparable muscle activity index. [Results] The highest muscle activity of middle-aged women was observed in the ring bridging exercise. The middle-aged women had higher levels of all muscle activaties than the young women, particularly in the multifidus muscle and iliocostalis lumborum. No significant difference in muscle activity ratio was observed between the local muscles and global muscles in the three different exercises, though the muscle activity ratio was the highest in the ring bridging exercise. The young women group showed a higher ratio of the internal oblique/rectus abdominus than the middle aged women in the bridging exercise. [Conclusion] The ring bridging exercise should be used for stabilizing the lumbar area because the young women showed a higher ratio than the middle aged women.

Research on the Countermeasures of Urban Transport Problem in Wuhan

Abstract: Traffic is an important factor to investigate the development space of a city. Therefore, how to solve current traffic problems has become the first task of local government and academic communities. The article analysis the traffic issues in Wuhan from many aspects such as urban ring roads, bridge traffic, urban sprawl, transfer system and people’s traffic, trying to find out the causes of Wuhan traffic problem. Additionally, we use the referential models to resolve the current problems, and give some recommends.

Research on the Countermeasures of Urban Transport Problem in Wuhan

Abstract: Traffic is an important factor to investigate the development space of a city. Therefore, how to solve current traffic problems has become the first task of local government and academic communities. The article analysis the traffic issues in Wuhan from many aspects such as urban ring roads, bridge traffic, urban sprawl, transfer system and people’s traffic, trying to find out the causes of Wuhan traffic problem. Additionally, we use the referential models to resolve the current problems, and give some recommends.