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A combination of low-temperature scanning tunneling microscopy and density functional theory calculations was used to determine the binding characteristics of single pyridine molecules at a low coverage on a silver surface. The results indicated that pyridine binds to silver through the nitrogen atom in either a perpendicular or a parallel configuration with the latter structure being more prevalent. Both configurations are produced predominantly through electrostatic interaction between nitrogen and silver atoms. This is induced by charge redistribution in the pyridine molecule and nearby silver atoms upon pyridine adsorption. [ABSTRACT FROM AUTHOR]

The healing of burn wounds has been widely characterized to be highly intricate, involving processes such as neo-vascularization, granulation, re-epithelialization, inflammation and wound contraction. Various therapies are available for the management of burn wounds; however, a truly effective therapeutic strategy has yet to be identified due to safety issues. The aim of the present study was to assess and confirm the burn wound healing properties of the compounds asiaticoside (AE) and madecassoside (MA), which are found in the herb Centella asiatica. The cytotoxic nature of the AE and MA were inspected and were confirmed to be non-toxic up to 500 ppm. The compounds AE and MA increased monocyte chemoattractant protein-1 production, but caused no significant effect on vascular endothelial growth factor production. In addition, an in vivo animal burn model was employed to represent the features of burn wound healing. Hence, the present results warrant the further investigation of C. asiatica extracts for use in burn healing. [ABSTRACT FROM AUTHOR]

To efficiently identify small molecules binding to a G-quadruplex structure while avoiding binding to duplex DNA, we performed a multistep structure-based virtual screening by simultaneously taking into account G-quadruplex DNA and duplex DNA. Among the 13 compounds selected, one outstanding ligand shows significant selectivity for G-quadruplex binding as determined using SPR, FRET-based competition and luciferase activity assay. [ABSTRACT FROM AUTHOR]

A slanted columnar TiO2 sculptured anisotropic thin film (ATF) is prepared via the glancing angle deposition technique and used as the phase retardation plate. The tilted nanocolumn microstructures of thin film induce the optical anisotropy. With the biaxial birefringent model, the optical constants dispersion equations of TiO2 ATF are derived by fitting the transmittance spectra for s- and p-polarized waves measured at normal and oblique incidence within 400 nm–1200 nm. The phase shift of polarized light after reflection and/or transmission through the TiO2 ATF is analyzed with the characteristic matrix employing the extracted structure parameters. The theoretical studies reasonably well accord with the experimental results measured with spectroscopic ellipsometry. In addition, the dependences of the phase shift on the coating physical thickness and oblique incidence angle are also discussed. Birefringence of the biaxial ATF provides a sophisticated phase modulation by varying incidence angles over a broad range to have a wide-angle phase shift. [ABSTRACT FROM AUTHOR]

A novel single-cavity narrowband Fabry—Pérot (FP) polarizing filter at normal incidence, constructed from a sandwich structure with sculptured anisotropic space layer and symmetric isotropic HR mirrors, is designed and prepared. The optical performances of transmittance, phase shift, central wavelength, and bandwidth for two polarized states are analyzed with the characteristic matrix. The numerical studies accord reasonably well with the experimental results. It is demonstrated that the polarization state of the electromagnetic wave and phase shift can be modulated by employing an anisotropic space layer in the polarizing beam splitter system. The birefringence of the anisotropic space layer provides a sophisticated phase modulation by varying the incidence angles over a broad range to have a wide-angle phase shift. [ABSTRACT FROM AUTHOR]

Based on the theoretical analysis of biaxial birefringent thin films with characteristic matrix method, we investigate the phase shift on transmission of a tilted columnar biaxial film at normal and oblique incidence over 300-1200nm for s- and p-polarized waves. Compared with the simplified calculation method, the interference effects of the birefringent thin film are considered to yield more accurate results. The quarter wavelength phase shift calculated with the characteristic matrix method is consistent with that monitored with in situ measurement by two-angle ellipsometry, which validates our complied program for the calculation of the phase shift of the biaxial anisotropic thin film. Furthermore, the characteristic matrix method can be easily used to obtain continuous adjustable phase retardation at oblique incidence, whereas the simplified calculation method is valid for the case of normal incidence. A greater generality and superiority of the characteristic matrix method is presented. [ABSTRACT FROM AUTHOR]

The song of zebra finch is stable in life after it was learned successfully. Vocal plasticity is thought to be a motor exploration that can support continuous learning and optimization of performance. The activity of RA, an important pre-motor nucleus in songbird's brain, influences the song directly. This variability in adult birdsong is associated with the activity of NMDA receptors in LMANRA synapses, but the detailed mechanism is unclear. The control of gain refers to modulation of a neuron's responsiveness to input and is critically important for normal sensory, cognitive, and motor functions. Here, we observed the change of gain in RA projection neurons after exogenous NMDA was applied to activate NMDA receptors using the whole-cell current clamp recording. We found that NMDA substantially increased the slope (gain) of the firing rate-current relationship in RA projection neurons. The AMPA receptor-dependent excitability played a crucial role in the modulation of gain by NMDA. These results suggested that NMDA receptors may regulate the dynamics of RA projection neurons by input-output gain. [ABSTRACT FROM AUTHOR]

G-quadruplexes are higher-order DNA and RNA structures formed from guanine-rich sequences, and they are attractive anticancer drug targets. Understanding the three-dimensional interactions between a G-quadruplex and its ligand in solution is the key to discovering a drug lead. Hence, from crystallographic or NMR structures, molecular dynamics studies have been performed on six ligand−quadruplex complexes. BRACO-19, BSU6039, daunomycin, RHPS4, MMQ1, and TMPyP4 are the six ligands that bind to the G-quadruplex structures in the studies. Based on molecular dynamics simulations and a series of computational analyses, the results suggest that ions move away from the external G-quartet to let the ligand bind to the quadruplex in aqueous solution. The ligand binding can increase the stability of the Hoogseen hydrogen bonds within the G-quartet. However, the G-quartet binding site can only fit one ligand molecule. The ligand can form hydrogen bonds at the loop or flank of the quadruplex. However, not all the interactions will stabilize the ligand−quadruplex complex in aqueous solution. These findings can assist in the design of selective and potent G-quadruplex ligands. [ABSTRACT FROM AUTHOR]

On the basis of calculations using the density functional theory, we show that C62, a recently synthesized nonclassical fullerene, will presumably undergo dimerization with various isomers at elevated temperatures. This is shown by calculating the dimerization energy and the activation barrier of the dimerization. Eight possible isomers of the dimer were identified, all of which are more stable than the two isolated monomers. The relative stability of various isomers depends upon the kind of C&dbond;C bonds within the four-membered carbon ring involved in the dimerization. In addition, similar calculations were performed for the monomers and dimers of H2&bond;C62 and F2&bond;C62. Six isomers were identified for each of the dimers. Although less pronounced than the case of the C62 dimer, all isomers of the H2&bond;C62 dimer are appreciably more stable than the individual monomers. Although a large steric repulsion due to F atoms significantly reduces the stability of F2&bond;C62 dimer, its two isomers are still more stable than separate monomers. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [ABSTRACT FROM AUTHOR]

On the basis of calculations using density functional theory, we investigated the relative stabilities of all isomers of Sc3NC67B and Sc3NC67N as well as those of stable isomers of Sc3NC66BN. As a result, we predict that Sc3NC68can be doped substitutionally with a boron atom much better than C60. This effect can be ascribed to the favorable electrostatic attraction between the encased Sc3N cluster and the polar C−B bonds of the fullerene cage, which show the important role played by the encapsulated atoms in stabilizing the fullerene. A difference in the interaction also determines the regiospecificity of Sc3NC67B. On the contrary, N-doping of the fullerenes forming Sc3NC67N is much less favorable than that in C60or C70. A judicious choice of stable isomers of Sc3NC66BN among a vast number of possible isomers indicates that Sc3NC68can also be doped with a pair of B and N atoms better than C60under the simultaneous existence of B and N sources. Relative stabilities of various isomers of the BN-substituted fullerenes can be understood in terms of the combined electrostatic effects in the B- and N-substitutions of Sc3NC68complemented by a specific local preference in the N-substitution and the formation of a B−N bond. [ABSTRACT FROM AUTHOR]

On the basis of calculations using density functional theory, we show that C58N12, just as C48N12, can be a stable N-dopant of C70. By considering many different isomers of the product, we find that the chemical stability of C48N12and C58N12, with respect to oxygenation, is not significantly different from that of C70, thereby indicating that the N-dopant would not easily be oxygenated in air under normal conditions. In both C48N12O and C58N12O, many different isomers are expected, in which oxygenation occurs at different C-N bonds as well as at C-C bonds, among which specific C-N bonds are the most amenable to the reaction. Investigation of their hydrogenations shows that C48N12is slightly more easily hydrogenated than C60, while C58N12is less easily hydrogenated. In addition, we expect a regiospecificity in the hydrogenated products of C58N12, which prefers to react at equatorial sites, while C70prefers reaction at polar sites. Meanwhile, comparison of the encapsulation energy of a nitrogen atom (Nen) in C60, C48N12, C70, and C58N12shows that the N-doped fullerenes, particularly C58N12, can encase the atom much better than the undoped ones, allowing us to expect the existence of NC48N12and NC58N12. Spin multiplicities are doublet for most of their stable structures. These observations correlate with the formation of Nen-C bonds, which are not found in NC60and NC70. Various isomers of the N-encapsulating fullerenes were identified. The relative stability of these isomers heavily depends on the number of substitutional nitrogen atoms around Nen-C bonds. [ABSTRACT FROM AUTHOR]

A compact two-layer frequency-selective surface is presented to design circular polarisers for broadband applications. By optimising the parameters of the semi-circle metal strip element, an excellent simulated bandwidth of axial ratio (AR) (lower than 3 dB) is achieved from 10.02 to 11.09 GHz, while the amplitude of the transmission coefficient is higher than 0.8. Furthermore, the polariser unit cell is less sensitive to the range of oblique incidence angles. To verify the proposed design, an X-band circular polariser prototype is fabricated and measured. The results show that excellent AR performance can be achieved; the measured AR of the transmission wave is lower than 3 dB in the band from 9 to 12 GHz. [ABSTRACT FROM AUTHOR]

A miniaturized double stop-band FSS for WLAN was proposed based on the structure of a ring patch with internal branches and a cross zigzag loaded line. This construction is obtained by using the multilayer connection method to paint the two layers of the patch that we designed on the top and bottom of the dielectric substrate to simulate the designed construction by using HFSS simulation. Analyzing the frequency response characteristics of the FSS indicates that the construction can generate two transmission band gaps at 1.92-2.17 GHz and 4.94-5.99 GHz in the WLAN wave. This construction has stronger polarization stability and angle stability when the incident electromagnetic wave is 0-60². It also has a simple construction, small size, and significant engineering application value. [ABSTRACT FROM AUTHOR]

A miniaturized double stop-band FSS for WLAN was proposed based on the structure of a ring patch with internal branches and a cross zigzag loaded line. This construction is obtained by using the multilayer connection method to paint the two layers of the patch that we designed on the top and bottom of the dielectric substrate to simulate the designed construction by using HFSS simulation. Analyzing the frequency response characteristics of the FSS indicates that the construction can generate two transmission band gaps at 1.92-2.17 GHz and 4.94-5.99 GHz in the WLAN wave. This construction has stronger polarization stability and angle stability when the incident electromagnetic wave is 0-60°. It also has a simple construction, small size, and significant engineering application value. [ABSTRACT FROM AUTHOR]

Dendrobium is the largest genus of tropical epiphytic orchid, some of which are traditional Chinese medicinal plants. The therapeutic components varied significantly among species. Endophytic microbes (fungi) hidden in medicinal plants may play an important effect on the overall quality of herb. Investigation of fungal composition in host plants is the first step toward elucidating the relationship endophyte-therapeutic content of herbal medicine. In this study, 401 culturable fungal endophytes were isolated and identified from 10 species of medicinal Dendrobium based on morphological and molecular techniques. The results showed that endophytic fungi from Dendrobium plants exhibited high biodiversity (37 genera, about 80 species). Acremonium, Alternaria, Ampelomyces, Bionectria, Cladosporium, Colletotrichum, Fusarium, Verticillium and Xylaria were the dominant fungal endophytes. Tropical epiphytic orchids appear to vary in degree of host specificity in their endophytic fungi. [ABSTRACT FROM AUTHOR]

A novel closed-form high-order small perturbation method (HOSPM) for the analysis of scattering from 1-D conducting random rough surfaces under TE incidence is developed. The main theoretical contributions of the HOSPM are as follows: (1) our method yields a general high-order SPM form for scattered fields of arbitrary orders, (2) Faà di Bruno's formula is introduced into computational electromagnetics (CEM) for the first time to expand a tapered incident wave and its partial derivatives in power series form, and (3) the form is simple and easy to program and does not require any mathematical pretreatment. Comparisons are made between the method of moments (MOM) and different-order HOSPMs in terms of several aspects, including accuracy and time efficiency. The order convergence of the HOSPM is discussed, the regions of validity with regard to correlation lengths and root mean square (RMS) heights are demonstrated for the 2nd-order HOSPM, and the robustness of the 2nd-order HOSPM is proven over a broad range of frequencies. [ABSTRACT FROM AUTHOR]

Elastic properties of three high pressure polymorphs of CaCO3 are investigated based on first principles calculations. The calculations are conducted at 0 GPa–40 GPa for aragonite, 40 GPa–65 GPa for post-aragonite, and 65 GPa–150 GPa for the -h-CaCO structure, respectively. By fitting the third-order Birch–Murnaghan equation of state (EOS), the values of bulk modulus and pressure derivative are 66.09 GPa and 4.64 for aragonite, 81.93 GPa and 4.49 for post-aragonite, and 56.55 GPa and 5.40 for -h-CaCO, respectively, which are in good agreement with previous experimental and theoretical data. Elastic constants, wave velocities, and wave velocity anisotropies of the three high-pressure CaCO phases are obtained. Post-aragonite exhibits 25.90%–32.10% anisotropy and 74.34%–104.30% splitting anisotropy, and -h-CaCO shows 22.30%–25.40% anisotropy and 42.81%–48.00% splitting anisotropy in the calculated pressure range. Compared with major minerals of the lower mantle, CaCO high pressure polymorphs have low isotropic wave velocity and high wave velocity anisotropies. These results are important for understanding the deep carbon cycle and seismic wave velocity structure in the lower mantle. [ABSTRACT FROM AUTHOR]

Background: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease and still continues to have the worst prognosis of all gastrointestinal malignancies. Reports have demonstrated that secretory leukocyte protease inhibitor (SLPI) is overexpressed in various cancers and may be a potential therapeutic strategy for the treatment of different cancers. However, the possible role of SLPI in PDAC is still unknown. In the present study, we investigate the effects of SLPI gene knockdown on the biological behavior of human pancreatic cancer cells. The expressions of SLPI were detected, by qRT-PCR and Western blot, in human PDAC tissues as well as AsPC-1, BxPC-3 and PANC-1 cells. After transfection with siRNA targeting to SLPI, SLPI expression was detected by qRT-PCR and Western blot in cells. Cell proliferation and apoptosis were also evaluated by MTT assay and flow cytometry (FCM). The trans-well assays were also employed to explore the effects of SLPI knockdown on the migration and invasion of PDAC cells in vitro. Results: The expressions of SLPI derived from human PDAC and PDAC cell lines were significant higher than those of control groups, respectively (P < 0.05). Regression analysis showed elevated SLPI level was positive correlated with development of PDAC. The siRNA target to SLPI significantly decreased the expressions of SLPI in these PDAC cell lines. Following SLPI-siRNA transduction, the proliferative capacity of the AsPC-1, BxPC-3 and PANC-1 cells was significantly inhibitions, compared to the blank (PDAC-wild type cells) and negative (non-targeting scrambled siRNA transduced PDAC cells) control ones, respectively (P < 0.05). Moreover, SLPI knockdown significantly increased the apoptosis fractions and reduced the migration and invasion of PDAC cells in vitro (P< 0.05). Conclusions: The present study demonstrated that: i) SLPI played an important role in PDAC progression; ii) SLPI might be an important characteristic of malignant PDAC associated with migration and invasion in vitro; and iii) siRNA targeting to SLPI might be a potential therapeutic strategy for the treatment of PCC. [ABSTRACT FROM AUTHOR]

Background: The avian influenza virus (AIV) causes frequent disease with high morbidity and mortality. RNA interference (RNAi) has been shown to provide an effective antiviral defense in animals, and several studies have focused on harnessing small interfering RNAs (siRNAs) to inhibit viral infections. In addition, single chain variable fragments (scFvs) contain the complete antigen binding site, and specific scFvs can bind to and neutralize viruses. Results: Fourteen positive scFvs were selected by the yeast two-hybrid system. Using molecular docking technology, we selected the three highest affinity scFvs for further functional validation. Results of indirect ELISA and IFA showed that all three scFvs could bind to FJ13 strain and had neutralizing activity, decreasing the viral infectivity markedly. Chicken fibroblastic DF-1 cells were transfected with scFvs in combination with siRNA-NP604 (an siRNA of anti-AIV NP protein previously reported). Following infection with FJ13 virus, copy numbers of the virus were significantly reduced from 12 h to at least 60 h post-infection compared to that achieved in cells transfected with scFv or siRNA-NP604 separately. Conclusions: A novel combination of antiviral siRNAs expressed in chicken cells and chicken antibody single-chain variable fragments (scFvs) secreted from the cells has a synergistic inhibitory effect on the avian influenza viral proliferation in vitro. Intracellular application of scFvs and anti-viral siRNA may provide a new approach to influenza prevention and treatment. [ABSTRACT FROM AUTHOR]

Mink enteritis virus (MEV) is one of the most important pathogens in the mink industry. Recent studies have shed light into the role of microRNAs (miRNAs), small noncoding RNAs of length ranging from 18–23 nucleotides (nt), as critical modulators in the host-pathogen interaction networks. We previously showed that miRNA miR-181b can inhibit MEV replication by repression of viral non-structural protein 1 expression. Here, we report that two other miRNAs (miR-320a and miR-140) inhibit MEV entry into feline kidney (F81) cells by downregulating its receptor, transferrin receptor (TfR), by targeting the 3′ untranslated region (UTR) of TfR mRNA, while being themselves upregulated. [ABSTRACT FROM AUTHOR]

Streptococcosis is one of the major infectious and contagious bacterial diseases for swine farm in southern China. The influence of various control measures on the outbreaks and transmission of S. suis is not currently known. In this study, in order to explore effective control and prevention measures we studied a deterministic dynamic model with stage structure for S. suis. The basic reproduction number R0 is identified and global dynamics are completely determined by R0. It shows that if R0 < 1, the disease-free equilibrium is globally stable and the disease dies out, whereas if R0 > 1, there is a unique endemic equilibrium which is globally stable and thus the disease persists in the population. The model simulations well agree with new clinical cases and the basic reproduction number of this model is about 1.1333. Some sensitivity analyses of R0 in terms of the model parameters are given. Our study demonstrates that combination of vaccination and disinfection of the environment are the useful control strategy for S. suis. [ABSTRACT FROM AUTHOR]

G-Quadruplex is a special DNA secondary structure and present in many important regulatory regions in human genome, such as the telomeric end and the promoters of some oncogenes. Specially, different forms of G-quadruplexes exist in telomeric DNA and c-mycpromoter and play important roles in the pathway of cell proliferation and senescence. The effects of G-quadruplex ligands for either telomeric or c-mycG-quadruplex in vitro have been widely studied, but the specificity of these effects in vivo is still unknown. In the present research, various experiments were carried out to study the effect of G-quadruplex ligand SYUIQ-05 on tumor cell lines and the mechanism of this effect. Our results showed that it preferred to bind with G-quadruplex in c-mycand had rather insignificant effect on G-quadruplex in telomere. Therefore, it is possible that this compound had its antitumor activity for cancer cells mainly through its interaction with c-mycquadruplex. [ABSTRACT FROM AUTHOR]

A series of 5- N-methyl quindoline (cryptolepine) derivatives ( 2a− x) as telomeric quadruplex ligands was synthesized and evaluated. The designed ligands possess a positive charge at the 5- Nposition of the aromatic quindoline scaffold. The quadruplex binding of these compounds was evaluated by circular dichroism (CD) spectroscopy, fluorescence resonance energy transfer (FRET) melting assay, polymerase chain reaction (PCR) stop assay, nuclear magnetic resonance (NMR), and molecular modeling studies. Introduction of a positive charge not only significantly improved the binding ability but also induced the selectivity toward antiparallel quadruplex, whereas the nonmethylated derivatives tended to stabilize hybrid-type quadruplexes. NMR and molecular modeling studies revealed that the ligands stacked on the external G-quartets and the positively charged 5- Natom could contribute to the stabilizing ability. Long-term exposure of human cancer cells to 2rshowed a remarkable cessation in population growth and cellular senescence phenotype and accompanied by a shortening of the telomere length. [ABSTRACT FROM AUTHOR]

Multiwalled boron carbonitride (BCN) nanotubes with two different structures were synthesized via thermal chemical vapor deposition; one has 10% C atoms homogeneously doped into BN nanotubes (B0.45C0.1N0.45 NTs), and the other has BN layers sheathed with 5-nm-thick C outerlayers (BN-C NTs). The electronic structures of the B, C, and N atoms were thoroughly probed by synchrotron X-ray photoelectron spectroscopy and the X-ray absorption near-edge structure method. The B0.45C0.1N0.45 NTs contain a significant amount of BC and CN bonding with a pyridine-like structure (hole structure), which reduces the π bonding states of the B and N atoms. From the XPS valence band spectrum, the band gap was estimated to be about 2.8 eV. In the BN-C NTs, the C and BN domains are separated without forming the pyridine-like structure. Using the first principles method, we investigated the relative stabilities and electronic structures of the various isomers of the double-walled (12,0) @ (20,0) BCN NTs. The C-outerlayer BN nanotube structure is the most stable isomer, when there exist no defects in the tubes with B/N = 1.0 (i.e., graphite-like structure). In addition, a reasonable model, which is characterized by the motives consisted of three pyridine-like rings around a hollow site, is presented for the local structure of C atoms in the B0.45N0.45C0.1 NTs. A considerable decrease of the band gap due to the 10% C doping was predicted, which was consistent with the experimental results. [ABSTRACT FROM AUTHOR]

One-dimensional Si3N4 nanostructures are desirable for constructing nanoscale electric and optoelectronic devices due to their peculiar morphologies. Herein, a facile and environmentally friendly catalyst-free method is proposed to synthesize ultra-long single crystal α-Si3N4 nanobelts via carbothermal nitridation of carbon nanotubes at 1750 °C. The obtained α-Si3N4 nanobelts with a flat surface (thickness of ∼150 nm, length of several millimeters) exhibited an extremely high aspect ratio, perfect crystal structure, and high specific surface area of 7.34–10.09 m2 g−1. In addition, the width was increased from approximately 80 nm to 8 μm by increasing the holding time from 1 to 3 h. The nanobelt formation was governed by the vapor–solid (VS) reaction between SiO vapor, N2 and carbon nanotubes, and the vapor–vapor reaction between SiO, CO and N2. The former was responsible for the initial nucleation and successive base-growth of α-Si3N4 nanotubes. The latter additionally contributed to the nanorod and subsequent proto-nanobelt formation and to the growth of the nanobelts. During high-temperature annealing at 1750 °C, the original Si3N4 nanotubes gradually transformed into nanorods, and, finally, nanobelts with stable shapes as a result of surface energy minimization. [ABSTRACT FROM AUTHOR]

We have developed an incandescent Mo source to fabricate large-area single-crystalline MoSe2 thin films. The as-grown MoSe2 thin films were characterized using transmission electron microscopy, energy dispersive x-ray spectroscopy, atomic force microscopy, Raman spectroscopy, photoluminescence (PL), reflection high energy electron diffraction (RHEED) and angular resolved photoemission spectroscopy (ARPES). A new Raman characteristic peak at 1591 cm−1 was identified. Results from Raman spectroscopy, PL, RHEED and ARPES studies consistently reveal that large-area single crystalline mono-layer of MoSe2 could be achieved by this technique. This technique enjoys several advantages over conventional approaches and could be extended to the growth of other two-dimensional layered materials containing a low-vapor-pressure element. [ABSTRACT FROM AUTHOR]