bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Some Reactions of Quinoxalinecarboazides
Authors: Moustafa O. S. 
Published: May 2015

AbstractChlorination of ethyl(quinoxalin‐2(1H)one)‐3‐carboxylate 1 gave ethyl (2‐chloroquinoxaline)‐3‐carboxylate 2;thionation of 1 by P2S5 or 2 by thiourea yielded the same product 3. Reaction of chloro compound 2 or thiocompound 3 with hydrazine hydrate gave pyrazolylquinoxaline 4. The reaction of ester 1 with thiourea or hydrazine hydrate afforded pyrimido quinoxaline 5 or carbohydrazide 6; the reaction of 6 with carbon disulfide in basic medium followed by alkylation afforded oxadiazoloquinoxaline derivatives 7, 8a,b. Carboazide 9 was produced by reaction of 5 with nitrous acid. Compound 9 on heating in an inert solvent, with or without amines, in alcohols or hydrolysis in H2O undergoes Curtius rearrangments to yield 10‐13. Reaction of 13 with thiosemicarbazide gave triazoloquinoxaline 14 which on reaction with alkylhalides or hydrazine hydrate yielded 15a‐c while hydrolysis of 13 gave 3‐aminoquinoxalinone 16 which was used as an intermediate to produce 17‐20.
Sesquiterpenoids and Diterpenoids from the Liverwort Heteroscyphus Coalitus
Authors: Jong Jing‐Rong , Wu Chia‐Li 
Published: May 2015

AbstractThirteen specimens of Heteroscyphus coalitus were chemically examined. Among the isolated compounds, 1‐hydroxyaromadendr‐4‐en‐3‐one has not been reported previously. A third new chemotype with kauranoids as the major constituents for the liverwort H. coalitus was identified.
Chemical Vapor Deposition of SnO2 Thin Films from Bis(β‐diketonato)tin Complexes
Authors: Chi Kai‐Ming , Lin Chia‐Ch'i , Lu Ya‐Hui , Liao Ju‐Hsiou 
Published: May 2015

AbstractA series of bis(β‐diketonato)tin compounds have been systematically synthesized and examined as precursors for chemical vapor deposition of SnO2 thin films. These complexes were characterized by elemental analyses and NMR, IR and mass spectroscopic methods. X‐ray single‐crystal determination of Sn(tfac)2 reveals that the complex possesses a distorted trigonal bipyramidal structure. The SnO2 films can be deposited on the substrates such as silicon, titanium nitride, and glass by using Sn(hfac)2, Sn(tfac)2 and Sn(acac)2 as CVD precursors at deposition temperatures of 300‐600°C with a carrier gas of O2. The deposition rates range from 20 to 600 Å/min. Deposited films have been characterized by XRD, SEM, AFM, AES and AAS analyses.
Kinetic Study of the Ce(III)‐, Mn(II)‐, or Ferroin‐Catalyzed Belousov‐Zhabotinsky Reaction with Allylmalonic Acid
Authors: Yu Yueh‐O , Jwo Jing‐Jer 
Published: May 2015

AbstractIn a stirred batch experiment and under aerobic conditions, ferroin (Fe(phen)32+) behaves differently from Ce(III) or Mn(II) ion as a catalyst for the Belousov‐Zhabotinsky (BZ) reaction with allylmalonic acid (AMA). The effects of bromate ion, AMA, metal‐ion catalyst, and sulfuric acid on the oscillating pattern were investigated. The kinetics of the reaction of AMA with Ce(IV), Mn(III), or Fe(phen)33+ ion was studied under aerobic or anaerobic conditions. The order of reactivity of metal ions toward reaction with AMA is Fe(phen)33+ > Mn(III) > Ce(IV) under aerobic conditions whereas it is Mn(III) > Ce(IV) > Fe(phen)33+ under anaerobic conditions. Under aerobic or anaerobic conditions, the order of reactivity of RCH(CO2H)2 (R = H (MA), Me (MeMA), Et (EtMA), allyl (AMA), n‐Bu (BuMA), Ph (PhMA), and Br (BrMA)) is PhMA > MA > BrMA > AMA > MeMA > EtMA > BuMA toward reaction with Ce(IV) ion and it is MA > PhMA > BrMA > MeMA > AMA > EtMA > BuMA toward reaction with Mn(III) ion. Under aerobic conditions, the order of reactivity of RCH(CO2H)2 toward reaction with Fe(phen)33+ ion is PhMA > BrMA > (MeMA, AMA) > (BuMA, EtMA) > MA. The experiment results are rationalized.
Cholesterol Monohydrate Dissolution in Bile Salt‐Lecithin Solutions
Authors: Liu Chen‐Lun , Hsu Chi‐Feng 
Published: May 2015

AbstractA modified dissolution rate equation was used to quantitatively investigate the contribution of simple bile salt (BS) micelles and mixed BS‐lecithin (L) micelles to a cholesterol monohydrate (ChM) dissolution. Using a least‐squares technique to assess the relationship between the ChM dissolution rate and BS concentration at a constant L concentration, good curve‐fittings were obtained when the BS monomer concentration was set to equal the critical micellar concentration (CMC). For taurochenodeoxycholate (TCDC), a dihydroxy BS, the resulting values of parameters show that the simple TCDC micelle rate constant (ks) increases, but the mixed TCDC‐L micelle rate constant (kM) decreases with increasing L concentrations. As for taurocholate (TC), a tri‐hydroxy BS, a ChM dissolution study was conducted over the initial 2 hour period in different TC‐L solutions. A similar curve‐fitting analysis revealed that the simple TC micelle ks is independent of L concentration and is much higher than the kM of mixed TC‐L micelles. Moreover, the outcome of the analysis supports previously reported equilibrium dialysis study results concerning the BS to L ratio of mixed BS‐L micelles. According to the collision theory, the resulting ks and kM values are interpreted.
Alcohol Dehydrations over ZSM‐5 Type Zeolites, Montmorillonite Clays and Pillared Montmorillonites
Authors: Lin Hung‐En , Ko An‐Nan 
Published: May 2015

AbstractThe reactions of aliphatic alcohols (ethanol, 1‐propanol and 2‐propanol) were studied at 1 atm and 150–300°C by using ZSM‐5 type zeolites, montmorillonites, and pillared montmorillonites. With H‐ZSM‐5 (X) Y zeolites, the total number of acid sites increases with a decrease of Si02/Al2O3molar ratio (X) and calcining temperature (Y). In addition, apparent increase in the ratio of strong to weak acid sites occurs with increasing X or decreasing Y. The acidities of M‐ZSM‐5 (51) 600 zeolites follow the sequence: Li = Na < K < Cs. Pillared clays exhibit both larger surface areas and more acid sites than the clays. The alcohol conversions decrease in the order of 2‐propanol < 1‐propanol < ethanol, in accordance with the relative stabilities of the corresponding carbenium ions. The catalytic activities are parallel to the total number of catalyst acid sites and the reaction temperature. Favorable formations of ethers are observed at low reaction temperature and small contact time on a catalyst with weak acid strength. Simple consecutive reactions and combined pathway of parallel and consecutive reactions are proposed, respectively, for the dehydration of ethanol and for those of 1‐propanol and 2‐propanol.
Synthesis and Antibacterial Activity of s‐Triazoles, s‐Triazolo[3,4‐b]‐1,3,4‐thiadiazines and s‐Triazolo[3,4‐b]‐1,3,4‐thiadiazoles of 5‐Methylisoxazole
Authors: Hui Xin‐Ping , Zhang Lin‐Mei , Zhang Zi‐Yi , Wang Qin , Wang Fang 
Published: May 2015

AbstractThe condensation of 4‐amino‐5‐mercapto‐3‐(5‐methylisoxazol‐3‐yl)‐1,2,4‐triazole with substituted phenacyl bromide, aldehydes, p‐bromophenylisothiocyanate, aromatic carboxylic acids and oxalic acid, is described. The antibacterial activity of representative compounds was evaluated.
Picosecond Spectroscopic Studies of Tautomers of a Bisazo Compound in Solutions
Authors: Karpicz Renata , Gulbinas Vidmantas , Undzenas Algimantas 
Published: May 2015

AbstractSpectroscopic properties of a fluorenone‐based bisazo compound in different organic solvents have been investigated by means of the steady‐state absorption and fluorescence spectroscopy and picosecond time‐resolved absorption pump‐probe spectroscopy. The spectra of the molecules have been shown to be mainly determined by the excitations localized on individual chromophores ‐ azo fragments. Spectra of the azo‐enol and hydrazone‐quinone tautomeric forms were distinguished. Excited states of the two forms were found to relax in different ways. The hydrazone‐quinone form relaxes predominantly nonradiatively with the 400 ps time constant in α‐chloronaphthalene, resulting in the fluorescence quantum yield of the order of 10−2. The azo‐enol form relaxes via two competing ways, directly to the ground state with the time constant of the order of tens of picoseconds, or via the long‐lived intermediate state.
Development of Intense and Compact THz‐Radiation Source Using Femtosecond‐Laser Irradiated InAs Emitter in a High Magnetic Field
Authors: Ohtake Hideyuki , Ono Shingo , Sakai Masahiro , Kawahata Eiji , Kozeki Toshimasa , Murakami Hidetoshi , Liu Zhenlin , Tsukamoto Takeyo , Sarukura Nobuhiko 
Published: May 2015

AbstractTHz‐radiation power from femtosecond pulse irradiated InAs is found to be saturated at the magnetic field around 3T. We have found this saturation magnetic field drastically depends on geometrical layout and interesting magnetic field dependence of the center frequency for the THz radiation. Additionally, a compact THz‐radiation source using an InAs semiconductor is demonstrated with a turn‐key femtosecond fiber laser as an excitation source and a newly designed 2‐T permanent magnet. By using a newly designed magnetic circuit, a compact permanent magnet which can exceed the remanence magnetic field was obtained. This compact source is sufficiently intense for absorption spectroscopy.
Femtosecond Studies of Barrierless Rotamers in Solution
Authors: Glasbeek Max , Zhang Hong , van Der Meer Michael 
Published: May 2015

AbstractFemtosecond fluorescence upconversion experiments have been performed for photoexcited auramine (a diphenylaminemethane dye) in liquid solution. Following pulsed laser excitation, the fluorescence shows a multiexponential decay with an initial fast decay of 2 ps. The lifetime of the relaxed excited state is 30 ps or longer, depending on the viscosity of the solvent. Concomitant with the initial fast decay a dynamic Stokes shift is observed. From a study of the excited state dynamics as a function of solvent viscosity it is concluded that auramine undergoes a picosecond (quasi)‐barrierless relaxation from an emissive to a non‐emissive excited state. The relaxation within the excited state arises from torsional diffusion motions of the phenyl rings of the auramine molecule.
Exciton States and Relaxation in Molecular Aggregates: Numerical Study of Photosynthetic Light Harvesting
Authors: Pullerits TÕNu 
Published: May 2015

AbstractIn this article we briefly review the molecular exciton theory and apply it to photosynthetic light harvesting systems. We derive expressions for exciton relaxation rates using perturbation theory in Hilbert space representation and show how the Förster equation can be obtained from a general relaxation rate expression in case of well localized excitons. A detailed analysis of the exciton level structure and wavefunctions of the ring structure is presented for diagonal and nondiagonal disorder. We conclude that the latter plays only a minor role in light‐harvesting systems. We emphasize the relaxation rate dependency on square of the energy gap, which makes the high frequency modes particularly important for the exciton relaxation. We found a reasonably good agreement between the measured and calculated relaxation rates in photosynthetic purple bacteria.
3‐Acyl‐4‐diphenylmethyl‐2‐(N‐cyanoimino)thiazolidine: An Enantioselective Acylation Reagent for Racemic Amines
Authors: Tanaka Tetsuaki , Fang Xie , Azuma Tsutomu , Uchida Shuji , Ishida Toshimasa , In Yasuko , Iwata Chuzo , Maezaki Naoyoshi 
Published: May 2015

Abstract(S)‐3‐Acyl‐4‐diphenylmethyl‐2‐(N‐cyanoimino)thiazolidine was found to be an effective enantioselective acylation reagent for racemic amines. 3‐Benzoyl derivative was found to realize up to 79% ee upon acylation of (±)‐1 ‐phenylethylamine.
Fluorescence Lifetime of Tris‐(8‐Hydroquinoline) Aluminum Thin Film and Solution
Authors: Tang Kuo‐Chun , Cheng Pei‐Wen , Chien Volume , Cheng Cheu Pyeng , Cheng Po‐Yuan , Chen I‐Chia 
Published: May 2015

AbstractThe emission lifetime of tris‐(8‐hydroxyquinoline) aluminium (AIQ3) as a powder or a thin film from vaporization is measured at excitation wavelength ∼400 nm. According to decay curves recorded with time‐correlated single photon counting, the lifetimes are 17 and 12 ns for powder and film, respectively. Because films formed by sublimation contain microcrystals (C. W. Tang, S. A. Van Slyke and C. H. Chen, J. Appl. Phys. 65, 3610 (1989)), the measured lifetime reflects the structure and quality of the film. Decay curves of electronically excited AIQ3 dissolved in methanol, ethanol, acetonitrile, trichloromethane and benzene are measured; the lifetimes are 9.3, 11, 9.9, 18 and 20 ns, respectively. The lifetime of excited AIQ3 decreases with increasing solvent polarity; this trend is attributed to a dipole‐dipole interaction associated with relaxation of AIQ3. The quantum yield of fluorescence of AlQ3 in ethanol is measured to be 9.4 %.
Calculated Life Times of the First (v=1) Hydrogen Stretching Excited State on Hydrogen‐Covered H/Ge(111 )Germanium Surface
Authors: Hong Sho‐Ching , Ho Ming‐Shun , Lu Hsiu‐Feng , Sun Ying‐Chieh 
Published: May 2015

AbstractIn the present study, were port the calculated life times of the first hydrogen stretching excited state on a hydrogen‐covered H/Ge(111) germanium surface using molecular dynamics simulation based on the Bloch‐Redfield the ory. The life time was found to be 20 mi cro sec onds at room temperature, four or derslon ger than the hydrogen stretches on aH/Si(111) silicon surface. In addition, the calculations for the Ge‐D and Ge‐T stretches gave life times in the time scale of hundreds and tens of nano seconds, respectively, at room temperature. The thermal effect and an effect of the Ge‐Ge‐H bending frequency in the calculated life times are discussed.
Chemical Constituents from Annona Glabra III
Authors: Chang Fang‐Rong , Chen Chung‐Yi , Hsieh Tian‐Jye , Cho Chun‐Ping , Wu Yang‐Chang 
Published: May 2015

AbstractTwenty compounds including a dioxoaporphine, annobraine (1); two oxoaporphines, liriodenine (2) and lysicamine (3); five aporphines, (‐)‐nornuciferine (4), (‐)‐anonaine (5), (‐)‐N‐formylanonaine (6), (‐)‐asimilobine (7) and (+)‐nordomesticine (8); one proaporphine, (+)‐stepharine (9); two protoberberines, (‐)‐kikemanine (10) and dehydrocorydalmine (11); one azaanthraquinone, 1‐aza‐4‐methyl‐2‐oxo‐1,2‐dihydro‐9,10‐anthracenedione (12); two amides, N‐trans‐feruloyltyramine (13) and N‐p‐coumaroyltyramine (14); one ionone, blumenol A (15); and five steroids, β‐sitosterol (16), stigmasterol (17), β‐sitosteryl‐D‐glucoside (18), stigmasteryl‐D‐glucoside (19) and 6‐O‐palmitoyl‐β‐sitosteryl‐D‐glucoside (20), were isolated from the fruits and stems of Annona glabra. Among them, 1 is a novel dioxoaporphine alkaloid and 12 was obtained for the first time from natural sources. These compounds were characterized and identified by physical and spectral evidence.
A Versatile Diquinane from Fulvene as a Building Block in Natural Product Synthesis II. A Facile Synthesis of Iridoids 10‐Deoxygeniposide, Mussaenoside, and 8‐epi‐Loganin
Authors: Tai Huo‐Mu , Yang Chau‐Chen 
Published: May 2015

AbstractA formal total synthesis of 10‐deoxygeniposide (4), Mussaenoside (5), and 8‐epi‐loganin (6) from a versatile diquinane 3 is described.
The Constituents of the Leaves of Aristolochia Mollissima Hance
Authors: Wu Tian‐Shung , Chan Yu‐Yi , Leu Yann‐Lii 
Published: May 2015

AbstractTwo new sesquiterpenes, madolin‐T (1), madolin‐V (2) together with 14 known compounds were isolated from the leaves of Aristolochia mollissima. Their structures were determined by spectral analysis.
Phase Separation of n‐Propanol from Water and Extraction of Cadmium(ll) Complex into n‐Propanol
Authors: Li Quan‐Min , Liu Qi , Zhang Li‐Min , Xue Wan‐Xin 
Published: May 2015

Abstractn‐Propanol can be salted out from aqueous solution by adding inorganic salts. This phase separation method has been used for the extraction of cadmium(II) as Cd(II) complex into n‐propanol phase at pH 2.0‐6.0, with 2.5 × 10−4M of Rhodamine B (RB+), 2.6 g/10 mL of ammonium sulfate as the salting‐out reagent, n‐propanol as the solvent, in the presence of 0.065 M of KI. Cd(II) was determined spectrophotometrically by measuring the absorbance at 495 nm. Various parameters influencing the phase separation and the extraction of Cd(II) have been investigated. The method is quite simple and useful; it affords binary separation of Cd(II) from Fe(III), Co(II), Ni(II), Zn(II), Mn(II)and Al(III) and is applicable to the separation of Cd(II) from synthetic samples. The extraction mechanism has been tentatively studied.
Base‐Promoted Reaction of a Cage Diketone. Novel Rearrangement to a Tricyclic Bridgehead Olefin
Authors: Chou Teh‐Chang , Wu Hui‐Juang , Liao Ju‐Hsiou 
Published: May 2015

AbstractCaged diketone 1underwent the base‐promoted reaction to produce bicyclo[2.2.1]heptenyl diacid 4and tricyclic ketone 5as major products. Tricyclic ketone 5possesses a bridgehead double bond embedded in a tricyclo[5.2.1.03,8]dec‐2‐ene ring skeleton. The structures of 4and 5were unambiguously established by X‐ray crystal analyses.
Time‐Resolved Phase Transitions of the Nanocrystalline Cubic to Submicron Monoclinic Phase in Zirconia
Authors: Lajavardi Manouchehr , Kenney Donald J. , Lin Sheng Hsien 
Published: May 2015

AbstractThe nanocrystalline cubic, tetragonal, and submicron monoclinic phases of pure zirconia were prepared by thermal decomposition of carbonate and hydroxide precursors. The crystallization and isothermal phase transformations of the oxide were studied using high temperature X‐ray diffraction, X‐ray diffraction and Raman spectra of quenched samples. Cubic zirconia formed first, and then progressively transformed to tetragonal and monoclinic phases at temperatures as low as 320°C. The cubic, tetragonal, and monoclinic phases for ZrO2 were found to be distinct functions of crystallite size, indicating the nanocrystalline nature of these phases. They were found to exist within critical size ranges of 50 to 140 Å, 100 to 220 Å and 190 to 420 Å (±5 Å), respectively. Thus, as the crystallites grow during annealing, they first transform from cubic to tetragonal and then from tetragonal to monoclinic at critical sizes. The classical Avrami equation for nucleation and growth was applied to the tetragonal to monoclinic phase transition.
Tubular Morphology of Mesoporous Silica MCM‐41
Authors: Lin Hong‐Ping , Hwang Jyun‐Hwei , Mou Chung‐Yuan , Tang Chih‐ Yuan 
Published: May 2015

AbstractWe investigated detailed conditions for synthesizing the tubular form of MCM‐41 mesoporous aluminosilicate. The method is the delayed neutralization method in which the rate of neutralization is one of the controlling factors. Rapid neutralization results in the particulate form while gradual neutralization leads to tubules. It is found that the tubule morphology has several sub‐categories. There are thick‐walled, think‐walled hollow tubular MCM‐41 and solid core tubules. There are void structures in the channel framework that makes the nanochannels to be effectively interconnected.
Fullerene‐Crown Ether Coated Piezoelectric Crystal Liquid Chromatographic Detector for Metal Ions and Polar/Nonpolar Organic Molecules
Authors: Hung Chen‐Hui , Shih Jeng‐Shong 
Published: May 2015

AbstractFullerene(C60)‐dibenzo‐16‐crown‐5‐oxyacetic acid (DBI6C5‐OCH2‐COOC60) was prepared and applied as the coating material on piezoelectric quartz crystals for detection of various metal ions and polar/nonpolar organic molecules. The C60‐crown ether‐coated piezoelectric crystal sensor with a home‐made computer interface for signal acquisition and data processing was applied as an ion chromatographic (IC) detector for various metal ions, e.g., alkali metal, alkaline earth metal and transition‐metal ions. The piezoelectric detector exhibited quite good sensitivity of 104 ∼ 106 Hz/M and good detection limit of 10−3 ∼ 10−4 M for these metal ions. The C60‐crown ether piezoelectric detector compared well with the commercial conductivity detector conventionally used for metal ions. The ionic size and ionic charge seemed to have significant effect on the frequency response of the piezoelectric detector. The C60‐crown ether coated piezoelectric crystal sensor was also employed as a high performance liquid chromatographic (HPLC) detector for various polar organic molecules with frequency responses in the order: amines > carboxylic acids > alcohols > ketones. Furthermore, nonpolar organic molecules, e.g., n‐hexane, 1‐hexene and 1‐hexyne, were also detected with this piezoelectric crystal detector. The frequency responses of the piezoelectric crystal detector for these nonpolar organic molecules were in the following order: alkynes > alkenes > alkanes. The effects of solvents and flow rate on the frequency responses of the piezoelectric crystal detector were investigated. The C60‐crown ether coated piezoelectric crystal detector also showed short response time (< 1 min.) and good reproducibility.
The Low Polar Constituents from Bidens Pilosa L. var. Minor (Blume) Sherff
Authors: Chang Ming‐Huey , Wang Guei‐Jane , Kuo Yueh‐Hsiung , Lee Ching‐Kuo 
Published: May 2015

AbstractAnew and 20 known compounds were isolated from Bidens pilosa L. var. minor (Blume) Sherff. The new compound was determined as 7‐phenyl‐hepta‐4,6‐diyne‐2‐ol by various physical techniques (MS, IR, UV, 1H‐, 13C‐NMR, and 2D‐NMR).
An Instrumental Correction for the Determination of Mercury in Biological and Sediment Samples Using Cold Vapor Atomic Absorption Spectrophotometry
Authors: Chen Meng‐Hsien , Chou Chiu‐Long 
Published: May 2015

AbstractLow recovery rate and inconsistent measurements were found in the determination of mercury by method of cold vapor atomic absorption spectrophotometry using the hydride formation system (Hitachi HFS‐2, Hitachi Ltd., Tokyo). To overcome this problem of insufficient reaction time we developed a simple T‐joint device attaching to the commercial HFS‐2 system for the determination of mercury in various biological tissues and sediment samples. The T‐joint device was designed to combine sample and reductant injection which increased the reaction time of the sample allowing a complete formation of mercury vapor and speeding up the analysis process in comparison to the traditional cold vapor atomic absorption spectrometric method. Recoveries of mercury were in the range 95% ‐ 100%. The corrected procedure gave precise and accurate readings with several certified reference materials: NIES No. 2 from the Japan Environment Agency; IAEA‐356 from the International Atomic Energy Association, and DOLT‐2, DORM‐2, TORT‐2, PACS‐1 and MESS‐2 from the National Research Council of Canada. Simple acid digestion methods were developed based on the sample Hg level and the nature of the sample. The sample detection limits were 0.0125 μg g−1 fresh weight and 0.0625 μg g−1 dry weight for biological samples, and as low as 0.0125 μg g−1 dry weight for sediment samples. These analytical protocols we established met the general requirements in environmental research and monitoring of mercury pollution.
Total Synthesis of Carpacin and its Geometric Isomer as a Cancer Chemopreventer
Authors: Tseng Tsui‐Hwa , Tsheng Yen‐Min , Lee Yean‐Jang , Hsu Hsing‐Ling 
Published: May 2015

AbstractCarpacin (1a), an antidepressant in Asiatic folk medicine from the Carpano tree, is achieved in which the longest linear sequence is only four steps in over all yield 67% from commercially available Sesamol. The key transformations in the synthesis are the selective palladium‐catalyzed coupling reactions of aryl bromide with Grignard reagents. The first preparation of its geometric isomer (1b) is described. Highlights of the synthesis include Pd‐catalyzed coupling, selective hydrogenation, and Wittig reactions. Carpacin was examined as a potential inhibitor of carcinogenesis.