A New Seco-Abietanoid from the Bark of Cryptomeria japonica

Chemistry of Natural Compounds - A new seco-abietanoid, 12-hydroxy-6,7-seco-abieta-8,11,13-triene-6,7-dioic acid (1), was isolated from the methanol extract of the bark of Cryptomeria japonica. The...     

Random k‐SAT and the power of two choices

We study an Achlioptas‐process version of the random k‐SAT process: a bounded number of k‐clauses are drawn uniformly at random at each step, and exactly one added to the growing formula according to a particular rule. We prove the existence of a rule that shifts the satisfiability threshold. This extends a well‐studied area of probabilistic combinatorics (Achlioptas processes) to random CSP's. In particular, while a rule to delay the 2‐SAT threshold was known previously, this is the first proof of a rule to shift the threshold of k‐SAT for . We then propose a gap decision problem based upon this semi‐random model. The aim of the problem is to investigate the hardness of the random k‐SAT decision problem, as opposed to the problem of finding an assignment or certificate of unsatisfiability. Finally, we discuss connections to the study of Achlioptas random graph processes. © 2014 Wiley Periodicals, Inc. Random Struct. Alg., 47, 163–173, 2015     

Insight into the thermal decomposition of kaolinite intercalated with potassium acetate: an evolved gas analysis

The thermal decomposition process of kaolinite–potassium acetate intercalation complex has been studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS). The results showed that the thermal decomposition of the complex took place in four temperature ranges, namely 50–100, 260–320, 320–550, and 650–780 °C. The maximal mass losses rate for the thermal decomposition of the kaolinite–potassium acetate intercalation complex was observed at 81, 296, 378, 411, 486, and 733 °C, which was attributed to (a) loss of the adsorbed water, (b) thermal decomposition of surface-adsorbed potassium acetate (KAc), (c) the loss of the water coordinated to potassium acetate in the intercalated kaolinite, (d) the thermal decomposition of intercalated KAc in the interlayer of kaolinite and the removal of inner surface hydroxyls, (e) the loss of the inner hydroxyls, and (f) the thermal decomposition of carbonate derived from the decomposition of KAc. The thermal decomposition of intercalated potassium acetate started in the range 320–550 °C accompanied by the release of water, acetone, carbon dioxide, and acetic acid. The identification of pyrolysis fragment ions provided insight into the thermal decomposition mechanism. The results showed that the main decomposition fragment ions of the kaolinite–KAc intercalation complex were water, acetone, carbon dioxide, and acetic acid. TG-FTIR-MS was demonstrated to be a powerful tool for the investigation of kaolinite intercalation complexes. It delivers a detailed insight into the thermal decomposition processes of the kaolinite intercalation complexes characterized by mass loss and the evolved gases.     

The Function of Self-Assembled Polyfluorene-Based π-Conjugated Supramolecular Structures Formed in Twisted Nematic Liquid Crystals

We demonstrate that the supramolecular structure can be formed through the fibrous self-assembly of the polyfluorene-based polymer F8BT in liquid crystal (LC) 5CB. With the utility of alignment layer, the F8BT molecules can be aligned and formed oriented polymer network. We found that the presence of oriented polymer network makes twisted nematic LC exhibit excellent electro-optical properties (EO) of driving voltage reduction and EO bump peak elimination. The polyfluorene-based supramolecular structure provides the function of stabilizing LC molecules. We consider this functional self-assembled network has potential to apply in various devices for the ability of improving performance in operating property.     

Characterizing Plasma-exposed In0.52Al0.48As Surface Using Photoreflectance-, Raman-, and Photoluminescence Spectra Method

We have performed Photoreflectance (PR), Raman Scattering (RS), and Photoluminescence (PL) experiments to characterize the In_0.52Al_0.48As surface exposed to plasma by a gas mixture of CH₄/H₂/Ar, PR spectra indicate that RIE (plasma) causes defects such as nonradiative recombination centers, scattering centers, and defects leading to the decrease of signal intensity, broaden line width and red shift of the transitions by increasing the rf power. In the Raman scattering study, RIE causes defects against InAs-like and AlAs-like LO modes vibration. As the rf power increased, the maximum of two LO modes shifts towards lower frequency and the line shape becomes increasingly asymmetric. Also, the intensity degrades gradually by disorder and point defects with increasing rf power. The PL transition energies show a red-shift with increasing the rf power. In addition, the spectral feature broadens, and the intensity decreases with rf power higher than 200 w. The consistence of the PL, PR, and RS results indicate that these three methods can be used as sensitive probes to evaluate the near surface damage of the epilayer.     

Secondary Metabolites with Anti-Inflammatory from the Roots of Cimicifuga taiwanensis

The genus Cimicifuga is one of the smallest genera in the family Ranunculaceae. Cimicifugae Rhizoma originated from rhizomes of Cimicifuga simplex, and C. dahurica, C. racemosa, C. foetida, and C. heracleifolia have been used as anti-inflammatory, analgesic and antipyretic remedies in Chinese traditional medicine. Inflammation is related to many diseases. Cimicifuga taiwanensis was often used in folk therapy in Taiwan for inflammation. Phytochemical investigation and chromatographic separation of extracts from the roots of Cimicifuga taiwanensis has led to the isolation of six new compounds: cimicitaiwanins A–F (1–6, respectively). The structures of the new compounds were unambiguously elucidated on the basis of extensive spectroscopic data analysis (1D- and 2D-NMR, MS, and UV) and comparison with the literature data. The effect of some isolates on the inhibition of NO production in lipopolysaccharide-activated RAW 264.7 murine macrophages was evaluated. Of the isolates, 3–6 exhibited potent anti-NO production activity, with IC₅₀ values ranging from 6.54 to 24.58 μM, respectively, compared with that of quercetin, an iNOS inhibitor with an IC₅₀ value of 34.58 μM. This is the first report on metabolite from the endemic Taiwanese plant-C. taiwanensis.     

Tens of GHz Tantalum pentoxide‐based micro‐ring all‐optical modulator for Si photonics

A tantalum pentoxide‐based (Ta₂O₅‐based) micro‐ring all‐optical modulator was fabricated. The refractive index inside the micro‐ring cavity was modified using the Kerr effect by injecting a pumped pulse. The transmittance of the ring resonator was controlled to achieve all‐optical modulation at the wavelength of the injected probe. When 12 GHz pulses with a peak power of 1.2 W were coupled in the ring cavity, the transmission spectrum of the Ta₂O₅ resonator was red‐shifted by 0.04 nm because of the Kerr effect. The relationship between the modulation depth and gap of the Ta₂O₅ directional coupler is discussed. An optimized gap of 1100 nm was obtained, and a maximum buildup factor of 11.7 with 84% modulation depth was achieved. The nonlinear refractive index of Ta₂O₅ at 1.55 μm was estimated as 3.4 × 10^?14 cm²/W based on the Kerr effect, which is almost an order of magnitude higher than that of Si₃N₄. All results indicate that Ta₂O₅ has potential for use in nonlinear waveguide applications with modulation speeds as high as tens of GHz.

     

Numerical study of InGaN tandem solar cells with intermediate bands

Theoretical investigations of InGaN tandem solar cells with intermediate bands (IBs) have been conducted through calculating the diode equation taking into account the radiative and nonradiative recombination currents. The calculated maximum ef?ciencies of the double‐junction cell with one IB in each subcell are 57.85% and 68.37% under AM1.5G one‐sun and 46000‐sun illuminations, respectively. It has also been observed that the combined device with the top‐cell bandgaps of 2.9–3.4 eV (2.6–3.4 eV for full concentration) may have an opportunity to realize the application of over 50% efficiency. We suggest that the optimized width of the IB layer be designed in the range of 1–6 μm if its absorption coefficient is 10⁴–10⁵ cm^–1 in the IB region.     

A curve of nilpotent Lie algebras which are not Einstein nilradicals

The only known examples of non-compact Einstein homogeneous spaces are standard solvmanifolds (special solvable Lie groups endowed with a left invariant metric), and according to a long standing conjecture, they might be all. The classification of Einstein solvmanifolds is equivalent to the one of Einstein nilradicals, i.e. nilpotent Lie algebras which are nilradicals of the Lie algebras of Einstein solvmanifolds. Up to now, very few examples of \mathbb N{\mathbb N}-graded nilpotent Lie algebras that cannot be Einstein nilradicals have been found. In particular, in each dimension, there are only finitely many known. We exhibit in the present paper two curves of pairwise non-isomorphic nine-dimensional two-step nilpotent Lie algebras which are not Einstein nilradicals.