Orientation of molecular interface dipole on metal surface investigated by noncontact atomic force microscopy

We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomic force microscope(NC-AFM).The dipole moment orientations corresponding to two different configurations of individual TiOPc molecules were determined unambiguously.The correlation between the actual molecular structures and the corresponding STM topographies is proposed based on the sub-molecular resolution imaging and local contact potential difference(LCPD)measurements.Comparing with the pristine substrate,the LCPD shift due to the adsorption of non-planar molecule is dependent on the permanent molecular dipole,the charge transfer between the surface and the molecule,and the molecular configurations.This work would shed light on tailoring interfacial electronic properties and controlling local physical properties via polar molecule adsorption.     

Electronic structures and nonlinear optical properties of XAuPH<Subscript>3</Subscript>

The studies on model systems XAuPH3(X-H,F,Cl,Br,I,CN,CH3)have been carried out by using ab intiol HF and DFT B3LYP methods at pseudopotential and double-zeta LANL2DZ level.The results are compared with those of MP2,The properties of the models.i.e.the atomic net charge populations.the frontier molecular orbitals and nonlinear optical(NLO)properties have been investigated under an applied electric field on the basis of optimized structures.The computational results show that for these models characterized as electron acceptor-metal-electron donor(A-M-D)system,the NLO properties are due to intramolecular charge-transfer interaction between the acceptor and the donor.The more charges transfer gives,the better NLO properties.In the selected model systems,IAuPH3 has the biggest βvec and γof 1184.1942 a.u.and 17341.9214 a.u.,whereas IC6H4PH3^ ,A TYPICAL a-π-D organic conjugated system,has βvec and γof 710.7697 and 11664.1405 a.u.respectively.In comparison.IAuPH3 has significant NLO properties.     

Quantum chemical studies on tuning the second-order nonlinear optical molecular switching of triarylborane derivatives

In this work, density functional theory (DFT) combined with the finite field (FF) method has been adopted to analyze the second-order nonlinear optical (NLO) properties of the triarylborane (TAB) derivatives obtained by introducing different inductive electron groups into the phenylene ring of the TAB (RTAB, where R=2-C6H5-C2B10H10(1),R=F(2), R=Me(3),R=NO2(4),R=NH2(5)). The static first hyperpolarizabilities (βtot) of the RTAB molecules can be switched by binding one F- to the boron center (RTAB′) or one-electron reduction (RTAB"). The DFT-FF calculations show that the βtot values of 2′, 3′ and 5′ decrease while those of 1′ and 4′ increase compared with the values of their neutral molecules, which was attributed to the fact that the charge transfers of 2, 3 and 5 become smaller and those of 1 and 4 become larger by binding one F- ion to the boron center, according to time-domain DFT (TD-DFT) analysis. However, the incorporation of one electron enhances the second-order NLO properties of the RTAB molecules remarkably, especially for system 1. It is notable that the βtot value of reduced form 1″ is 508.69×10-30 esu, i.e. about 578 times larger than that of system 1. Frontier molecular orbital (FMO) and natural bond orbital (NBO) analyses suggest that the reversal of the charge distribution between the neutral molecules and their reduced forms leads to low HOMO-LUMO energy gaps (E0) and thus large βtot values for the reduced forms.     

MOLECULAR DESIGN STUDY ON THE NEW ORGANIC NONLINEAR OPTICAL MATERIALS

In this paper, the second-order nonlinear-optical coefficients of a series of conjugated substituted polyenes have been calculated by the semi-empirical CNDO/S-CI method, we have studied in detail the influence on the number of substituents, the location of the substituents and the conjugation length in molecules to the NLO coefficient β The results showed that the introduction of the electronic donor and acceptor groups and the increase in the distance between the substituents and the conjugated length may lead to enhanced NLO responses. It is also shown that the calculated ln β_(vec) is linear with the number of double bonds in planar and linear trans substituted polyenes. A saturation effect in substitution is also presented. Based on these discussion one can provide the theoritical guidelines for designing and synthesizing of molecules with larger NLO coefficients.     

Effect of protein molecules on the photoluminescence properties and stability of water-soluble CdSe/ZnS core-shell quantum dots

The fact that the photoluminescence properties of quantum dots are always strongly influenced by the environment limits the scope of further progress in the field of QD’ bio-applications. In this paper, the effects of immunoglobulin G (IgG) on the photo-luminescence properties and stability of water-soluble CdSe/ZnS core-shell quantum dots coated with amphiphilic poly (acrylic acid) (PAA) are studied. Photoluminescence (PL) spectra, UV-vis spectra and excited state lifetime measurements are used to characterize the influence of different protein molecules, such as IgG (goat anti-human IgG, rabbit anti-human IgG, human IgG, and goat anti-human IgG-human IgG conjugates), avidin and bovine serum albumin (BSA) on the PL properties of QDs. The PL intensity and stability of CdSe/ZnS are largely enhanced compared to that of pure CdSe/ZnS QDs when the IgG molecules are added into the QD solution. The PL intensity increases with increasing the IgG concentration, but there appears no influence on the PL peak and a full width at half maximum (FWHM). The PL evolution of QDs as a function of different protein molecules depends on the structure of protein molecules, which is used as a sensor to recognize human IgG. It is inferred that the interaction between PAA coating layer and IgG molecules results in the enhancement of PL intensity. The study of the effect of pH and ion strength on optical properties of QD-IgG mixed solution, compared with the pure QD solution, suggests that pH value and ion strength do not destroy the interaction between the PAA coating layer and IgG. Excited state lifetime analysis indicates that the PL enhancement comes from the passivation of surface of the QDs with the PAA coating layer. IgG molecules have no effects on the properties of the biological system but can increase the stability and PL intensity of CdSe/ZnS QDs, which will enlarge the application of QDs in biomedicine and other fields.     

Composition, structure and mechanical properties of several natural cellular materials

The stem piths of sunflower, kaoliang and corn are natural cellular materials. In this paper, the contents of the compositions of these piths are determined and their cell shapes and structures are examined through scanning electron microscope (SEM) and optical microscope. Further research is conducted in the effects of the compositions and structures of the piths on the mechanical properties after testing the partial mechanical properties. The results show that the total cellulose, hemicelluloses and lignin content of each sample approaches 75% of the dry mass of its primary cell walls. With the fall of R value, a parameter relative to the contents of the main compositions, the flexibilities of the cellular piths de- scend while their stresses and rigidities increase. The basic cell shape making up the sunflower pith is approximately a tetrakaidehedron. The stem piths of kaoliang and corn are made up of cells close to hexangular prisms and a few tubular ones which can observably reinforce their mechanical properties in the axial directions.     

Correlation between intrinsic dipole moment and pyroelectric coefficient of Fe-Mg tourmaline

Single-crystal X-ray diffraction structural data of four Fe-Mg tourmalines with different Fe contents from Xinjiang, Sichuan, and Yunnan Provinces, China, were collected at room temperature and ?100℃. The intrinsic dipole moments of polyhedra and the total intrinsic dipole moment of the unit cell were calculated. By comparing the intrinsic electric dipole moments of the X, Y, Z, T, and B site polyhedra, it is found that the T site polyhedron makes the greatest contribution to the total intrinsic dipole moment. The pyroelectric coefficients of four Fe-Mg tourmalines were experimentally determined, and the influence of intrinsic dipole moments on their pyroelectric properties was investigated. The experimental results show that, compared with the case at room temperature, the intrinsic dipole moments change with the total Fe content at ?100℃ in a completely different way. With the decrease of temperature, the total intrinsic dipole moments of tourmaline decrease. Over the same temperature interval, the pyroelectric coefficients increase with the increase in intrinsic dipole moment.     

Algorithm of graph isomorphism with three dimensional DNA graph structures

An algorithm for solving the graph isomorphism problem with 3-D DNA structures is proposed in this paper. The karmed branched junction molecules are used to code k-degree vertices. Double stranded molecules are used to code edges. Then the molecules are mixed in a tube to be ligated. The result can be detected by gel electrophoresis. The time complexity of the algorithm is O(n2), where n is the number of vertices of the graph.     

Improved and excellent CO sensing properties of Cu-doped TiO<Subscript>2</Subscript> nanofibers

Cu-doped TiO2 nanofibers with an average diameter of about 80 nm are synthesized through an electrospinning method. Both anatase and rutile crystallographic structures are found in the fibers based on XRD results. Compared with pure TiO2 nanofibers, the Cu-doped TiO2 nanofibers exhibit improved CO sensing properties at 300°C. The sensitivity of Cu-doped TiO2 nanofibers is up to 3 when the sensor is exposed to 5 ppm CO, and the response and recovery times are about 4 and 8 s, respectively. Good selectivity i...     

The roles of π electrons in the electronic structures and optical properties of graphyne

The electronic structures and optical properties of graphyne consisting of sp-and sp 2-hybridized carbon atoms are studied using first-principles calculations.A tight-binding model of the 2p z orbitals are proposed to describe the electronic bands near the Fermi level.The results show that the natural band gap of graphyne originates from the inhomogeneous bindings between differently-hybridized carbon atoms.The interlayer interactions of bulk graphyne narrow the band gap to 0.16 eV and result in redshift of the optical spectral peaks as compared to single-layered graphyne.     

Transpositional behaviour of the Ds element in the Ac/Ds system in rice

Insertional mutagenesis based on maize Activator/Dissociator (Ac/Ds) transposons is becoming a ma- jor approach used to produce a saturated mutant collection in rice. In this research, Ds-T-DNA trans- formed homozygotes were crossed with Ac-T-DNA transformed homozygotes in order to establish an Ac/Ds transposon system in rice. The successive investigation of Ds transposition from F1 to F5 gen- erations indicated that the frequencies of germinal transposition increased over successive genera- tions and reached 54.2% in F3 generation. The Ds transposition pattern revealed that a Ds transposition induced an approximately 170-bp deletion of T-DNA sequence and another Ds transposition carried a 272-bp T-DNA sequence. Using thermal asymmetric interlaced PCR (TAIL-PCR), some flanking se- quences of the Ds element were amplified. Analyses of 17 Ds-flanking sequences showed that five Ds were inserted into gene regions. The Ds could transpose not only to the linked sites but also to the unlinked sites. The frequency of inter-chromosomal transposition of Ds was 33.3%.     

Synthesis,characterization and photoluminescence of aluminum <Emphasis Type="Italic">N</Emphasis>-aryloxo functionalized <Emphasis Type="Italic">β</Emphasis>-ketoiminate complexes

The synthesis, characterization and luminescent properties of aluminum complexes containing a dianionic N-aryloxo functionalized β-ketoiminate ligand are presented. 4-(2-Hydroxy-5-R-phenyl)imino-2-pentanone (R = Me, L¹H₂; R = tert-butyl, L²H₂) ligands reacted with AlEt₃ in tetrahydrofuran to give the aluminum complexes (L¹AlEt)₂ (1) and (L²AlEt)₂ (2) in reasonable isolated yields. X-ray diffraction revealed that complexes 1 and 2 have solvent-free centrosymmetric dimeric structures, and each aluminum center has distorted trigonal bipyramidal geometry. At room temperature, complexes 1 and 2 exhibit blue photoluminescence in acetonitrile with maximum emission wavelengths of 419 and 413 nm, respectively.     

The R- and AR-indices： Complementing the h-index

Based on the foundation laid by the h-index we introduce and study the R- and AR-indices. These new indices eliminate some of the disadvantages of the h-index, especially when they are used in combina-tion with the h-index. The R-index measures the h-core’s citation intensity, while AR goes one step further and takes the age of publications into account. This allows for an index that can actually in-crease and decrease over time. We propose the pair (h, AR) as a meaningful indicator for research evaluation. We further prove a relation characterizing the h-index in the power law model.     

Direct coordination of metal ions to cucurbit[<Emphasis Type="Italic">n</Emphasis>]urils

Cucurbit[n]urils (Q[n]) are promising ligands for the coordination of metal ions, metal complexes or clusters, and form various Q[n]-based complexes. Among the Q[n] complexes, those formed by direct coordination between Q[n]s and metal ions are partic- ularly important. The direct coordination of metal ions to cucurbit[n]urils leads to the formation of Q[n]-based molecular capsules, tubular polymers and molecular bracelets, which could have nanoscale applications in drug delivery, molecular devices and new materials.     

Asymmetric epoxidation of <Emphasis Type="Italic">α</Emphasis>,<Emphasis Type="Italic">β</Emphasis>-unsaturated ketones using <Emphasis Type="Italic">α</Emphasis>,<Emphasis Type="Italic">α</Emphasis>-diarylprolinols as catalysts

Asymmetric epoxidation of α,β-unsaturated ketones has been extensively studied and several important procedures have been developed in the last decade. This review addresses the most significant advances in asymmetric epoxidation of α,β-unsaturated ketones using proline-derived α,α-diarylprolinols as catalysts. Special attention has been paid to the enantioselective epoxidation of chalcones, α,β-unsaturated trifluoromethyl, trichloromethyl ketones and β,γ-unsaturated α-keto esters based on the reseach of our group.     

Genetic and physical mapping of AvrPi7, a novel avirulence gene of Magnaporthe oryzae using physical position-ready markers

Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most devastating crop diseases worldwide. The avirulence gene corresponding to rice blast resistance gene Pi7 in field isolate CHL346 was inherited as a single gene, designated AvrPi7, in a segregating population consisting of 189 ascospore progenies derived from a cross between field isolates CHL346 and CHL42. In order to determine the chromosomal location of the AvrPi7 locus, a total of 121 simple sequence repeat (SSR) markers were developed based on the whole-genome sequence of reference isolate 70-15 of M. oryzae. Linkage analysis of the locus with these SSR markers showed that eight SSR markers on chromosome 1 were linked to the locus, among which the closest flanking markers MS1-9 and MS1-15 were 3.2 and 16.4 cM from the locus, respectively. For fine mapping, additional PCR-based makers including eight SSR markers and three candidate avirulence gene (CAG) markers were developed in the region flanking both markers. The AvrPi7 locus was genetically delimited within a 1.6-cM region flanked by markers MS1-21 and MS1-22, and co-segregated with the marker CAG2. To construct a physical map of the AvrPi7 locus, molecular markers linked to the Avr gene were mapped on the supercontigs of the ref-erence isolate 70-15 through bioinformation analysis (BIA). Consequently, the AvrPi7 locus was delim-ited to a 75-kb interval flanked by markers MS1-21 and MS1-22 based on the reference sequence. Merodiploids observed in this study are also discussed.     

Osmotically stress-regulated the expression of glutathione peroxidase 3 in Arabidopsis

Gene expression of glutathione peroxidase 3 (ATGPX3) in response to osmotic stress was analyzed in Arabidopsis using ATGPX3 promoter-glucuronidase (GUS) transgenic plants. High levels of GUS ex- pression were detected under osmotic stress in ATGPX3 promoter-GUS transgenic plants. Compared with the wild type, the growth and development of ATGPX3 mutants (atgpx3-1) were more sensitive to mannitol. In addition, the expression of RD29A, ABI1, ABI2 and RbohD in atgpx3-1 was induced by ABA stress. These results suggest that ATGPX3 might be involved in the signal transduction of osmotic stress.     

<Emphasis Type="Italic">In vitro</Emphasis> induction of mouse meningeal-derived ips cells into neural-like cells

Previous research has shown that mouse embryonic stem (ES) cells can be induced to form neural cells in adherent monocultures. In this study, pluripotent stem (iPS) C5 cells derived from meningeal membranes were converted successfully into neural-like cells using the same protocol generally used for ES cells. Meningeal-iPS C5 cells were induced to express neural markers Sox1, Sox3, Pax6, Nestin and Tuj1 and to reduce the expression of ES markers Oct4 and Nanog during neural differentiation, and can be differentiated into Pax6 and Nestin positive neural progenitors, and further into neuronal, astrocytic, and oligodendrocytic cells. In vitro differentiation of iPS cells into patient-specific neural cells could serve as a model to study mechanisms of genetic diseases and develop promising candidates for therapeutic applications in dysfunctional or aging neural tissues. Meningeal cells express a high level of the embryonic master regulator Sox2, allowing them to be reprogrammed into iPS cells more easily than other somatic cells.