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Panax notoginseng is distributed throughout the north and northwest of Vietnam, especially Ha Giang, Lao Cai, and Cao Bang provinces. The root of this plant contains ginsenosides (Rb1, Rb2, Rd, Rg3), flavonoids, polyacetylene, polysaccharides, amino acids, fatty acids, and peptides. In this study, the ratios of enzyme (Viscozyme, Termamyl, Cellulase), solvent of components, and time extraction were investigated. The results showed that the highest contents of Rb1 and Rg3 were achieved in the sample extracted with the ratio of enzymes V:C:T = 1:0:0, ethanol:water (60:40, v/v) as extracting solvent in 45 minutes. Then, conditions of high performance liquid chromatography with diode array detector method to determine the content of ginsenosides Rb1 and Rg3 in the roots of Panax notoginseng were studied, including wavelength, mobile phase, and flow rate. The separation was subjected on a reversed-phase C18 column using acetonitrile (A) and water (B) as mobile phase. The gradient elution was set as follow: 0-10 min, 15-25% A; 10-20 min, 25-30% A; 20-40 min, 30-60% A; 40-60 min, 60-80% A; and 60-65 min back to 15% A before the next injection, at a flow rate of 0.5 mL/min, and the wavelength was set at 202 nm. The linear range was from 298.59 to 696.72 µg/mL for Rb1 and from 8.19 to 19.10 µg/L for Rg3. The limits of detection for Rb1 and Rg3 obtained were 0.31 µg/mL and 0.33 µg/mL, respectively. The limits of quantification were 0.95 µg/mL and 1.01 µg/mL for Rb1 and Rg3, respectively. Consequently, the high performance liquid chromatography demonstrated the highly sensitive and accurate method for determination of Rb1 and Rg3 in Panax notoginseng. [ABSTRACT FROM AUTHOR]

The diamond-like carbon (DLC) coatings were irradiated by the 10 picosecond laser pulses using the infrared (1064 nm), visible (532 nm), and ultraviolet (355 nm) light. The microRaman measurements indicated that the DLC films were removed in the center of the laser spot. The graphitization of the DLC and formation of the transpolyacetylene segments took place at the periphery regions of the laser beam radius. [ABSTRACT FROM AUTHOR]

Density functional theory using accepted semi-local exchange-correlation functionals is generally successful for structural properties. However, for electrical response calculations of extended molecular systems, like e.g. polyacetylene, they make large errors; for the hyperpolarizability the error can be several orders of magnitude. The errors can be traced to qualitative differences between the exchange potentials of semi-local and exact exchange methods. A recent effort has been successful in using a corrective term based on semi-local quantities to introduce the missing features directly into the exchange potential (as opposed to modeling the exchange-correlation energy). The resulting potential reproduces the derivative discontinuity, step structure, and counteracting field slope of exact exchange. It gives the polarizability of hydrogen chains with similar accuracy as exact exchange methods. [ABSTRACT FROM AUTHOR]

The impact of a laser’s photons (λ = 514.5 nm) on the surface of polyacetylene films (PA), composed of macromolecules PAcis and PAtrans produces simultaneously thermal and Raman diffusion [1]. The thermal effect initializes the isomerization of macromolecules PAcis to PAtrans [2]; this reaction is exothermic. Samples are polyacetylene oriented films synthesized horizontally or vertically in cis configuration and are subject to different laser powers during intervals of time which vary between 20 s and 250 s. The power (P (λ), mW) of the laser is equivalent to the temperature T, of isomerization [3]. Isotherms are constructed and are characterized by the laser power applied. We have established theoretical models calculations with the aim of determining the kinetic parameters of the reaction of isomerization: the activation energy (Ea), the frequency factor of Arrhenius (A), and the rate constant (k). We concluded that even in the field of seconds, the isomerization is a complex process different from a reaction of order: 1, 7/10, 2/3, 3/5, 1/2, 2/5 and 1/4. The order 2/3 being the most suitable. The study determined, among others, the rate constants k 2/3 (T) (of the order 2/3 of the isomerization reaction) = 0.003337244, 0.0052149, 0.0209636, 0.043727 s-1 respectively for Laser powers 30, 120, 200 and 300 mW; activation energy 17.7844 kcal/mol and a factor of collision 19.066816 106 s-1. These results are found to be close to the experimental results studied. [ABSTRACT FROM AUTHOR]

We review the old story of charge fractionalization in polyacetylene, and its newer realization in graphene. [ABSTRACT FROM AUTHOR]

The current-voltage (I-V) characteristics of individual nanofibers of lightly-doped polyacetylene show very strong nonlinearities. At low temperatures the I-V characteristics are consistent with Zener-type tunneling, and independent of temperature and magnetic field. These features suggest a novel conduction mechanism that involves tunneling of a segment of the conjugated bond system in the presence of an electric field, creating a pair of charged solitons. [ABSTRACT FROM AUTHOR]

The electronic spectra of polyacetylene cations were recorded at 20 K in the laboratory in an ion trap instrument. These can then be compared with diffuse interstellar band (DIB) absorptions. Examination of recently published data shows that the attribution of a weak DIB at ~506.9 nm to diacetylene cation is not justified. Study of the higher excited electronic states of polyacetylene cations shows that their widths can still be sufficiently narrow for consideration as DIB carriers. [ABSTRACT FROM AUTHOR]

Graphene nanoribbons (GNRs) are stripes of single layered graphenes with a finite width. The electronic states of GNRs are different by the edge conditions (armchair edges or zigzag edges). The results of tight-binding approximations are that the hydrogen terminated zigzag GNRs are metallic, and the hydrogen terminated armchair GNRs are metallic or semiconducting. But the narrowest hydrogen terminated GNRs are polyacethlenes, that are semiconducting. The reason of this contradiction is that the structures of polyacethlenes are changed by the Peierls transition. Therefore the effects of the Peierls transition of GNRs from polyacetylenes to graphene were examined systematically using density functional theory with structural optimizations. [ABSTRACT FROM AUTHOR]