bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic Field and Magnetic Isotope Effects upon Reactions of Heavy Atom‐Centered Radicals
Authors: Hayashi Hisaharu , Wakasa Masanobu , Sakaguchi Yoshio 
Published: May 2015

AbstractWe present our recent studies on magnetic field effects (MFEs) observed in reactions of heavy atom‐centered radicals such as Si‐,P‐, Ge‐, and Sn‐radicals with a ns‐laser photolysis technique under magnetic fields of 0–10 T. Although the MFES of heavy atom‐centered radicals are much smaller than those of C‐radicals due to the spin‐orbit interaction of heavy atoms, we have found appreciable MFEs in many reactions of such heavy atom‐centered radicals. Comparing the MFES of C‐radicals with those of heavy atom‐centered ones, we have explained the MFEs of heavy atom‐centered radicals in terms of the Δg and relaxation mechanisms. We have found that the separation between the MFES due to the Δg mechanism and those due to the relaxation one is possible with the enhancement of spin relaxation by the addition of a paramagnetic ion.We have also tried to enrich magnetic isotopes of heavy atoms with the magnetic isotope effect (MIE), using the reactions which show fairly large MFES. Recently, we have succeeded in enriching 73Ge. This is the heaviest isotope which has so far been enriched with the MIE from samples of natural abundance.
Overlapping Resonances, Multiple Time Regime Evolution Laws and the Sampling of Phase Space in Unimolecular Processes
Authors: Remacle F. , Levine R. D. 
Published: May 2015

AbstractUnimolecular processes can be described as the decay of an ensemble of N excited resonances coupled to K decay channels. Resonances are metastable states characterized by a complex energy whose real part is the position of the state along the energy axis while the imaginary part gives the individual decay rate of the state. Resonances usually overlap in the RRKM regime. The degree of overlap is measured by the parameter R = <I>/dE where <I> is the average of the individual decay rates of the excited resonances and dE is the average spacing between their position. In the exact degeneracy limit, that is, for an infinite value of R, (N‐K) resonances have a zero width, so that a fraction of the initial excitation remains permanently trapped in the bound subspace. This trapping effect subsists in the non degenerate case but is not complete. We use a random coupling effective Hamiltonian model to discuss the effect of the degree of overlapping R, and of the number of resonances N and decay channels K, on the temporal evolution laws of the bound subspace and of the fragments. The decay law of the bound subspace and the temporal evolution of the yields in fragments exhibit several time regimes. This is due to the fact that after the diagonalization of the effective Hamiltonian, the decay widths of the resonances cluster into one group of K large widths and one group of (N‐K) small ones. The trapping effect is due to the (N‐K) small widths. The amount of trapping depends on the value of the degree of overlapping R, and for a given value of R, on the ratio N/K: large values of R and of N/K correspond to a large amount of trapping in the bound subspace for times long when compared to ħ/<I>. The temporal evolution laws of the yields in fragment are also strongly affected by the degree of overlapping and the value of the ratio N/K. Due to the reorganization of the partial widths which follows the diagonalization of the effective Hamiltonian, we show that the nature of the dominant product can change while increasing the value of R and N/K. We also discuss the time evolution of the sampling of phase space for a specific preparation in terms of these two parameters. The volume sampled is computed using an entropic measure. When the resonances overlap, there is not enough time to completely sample phase space prior to dissociation. The fraction sampled decreases as the amount of trapping in the bound phase space increases.
Low Pressure Chemical Vapor Deposition of III/V‐Nitrides Using Organometallics and Hydrazoic Acid Precursors
Authors: Bu Y. , Lin M. C. 
Published: May 2015

AbstractIn and Ga nitride films have been deposited on various substrates using organometallics and hydrazoic acid (HN3) as nitrogen precursor. The film deposition was carried out under low pressure (10−510 −6 Torr) and low V/III ratios (1‐10). XPS analysis indicated that the ln(Ga):N atomic ratio of unity can be easily achieved by adjusting the experimental conditions. For the growth of InN on Si(100) substrate, 308‐nm photon beam is needed to speed up the film deposition rate. He(II) UPS spectra of InN films are in good agreement with the result of a pseudo‐potential calculation for InN valence band, while the spectra of GaN compare favorably with a recent semi‐ab‐initio calculation and with the UPS results of GaN single crystal films. The bandgap of our GaN films is ∼ 3.3 cV as determined by photoluminescence and UV‐VIS absorption spectra. Raman spectra taken from GaN Films showed peaks at 66 and 88 meV for TO and LO phonons, respectively, indicating a wurtzite structure of the GaN. In a corresponding X‐ray diffraction spectrum, the (002) peak is about 400 times more intense than that of the (101) peak, suggesting that the GaN layers are highly oriented with the c‐axis normal or nearly so to the Al2O3 substrate.
Probing Structure, Spectroscopy, Kinetics, and Dynamics on Metal Surfaces by Optical Second Harmonic Generation
Authors: Dai Hai‐Lung 
Published: May 2015

AbstractWith the intrinsic surface sensitivity, superior frequency and time resolution, and adaptability to all pressure conditions, optical second harmonic generation has proven a versatile and powerful diagnostic tool for surface science studies. Examples are provided in the use of surface second harmonic generation in elucidating the adsorption kinetics and structural transitions of molecular adlayers, detecting surface electronic transitions, and determining transient temperature changes on metal surfaces.
Graphical Determination of Monomer Shift, Dimer Shift and Dimerization Constant for Self‐Association: 2‐Isopropyl Phenol in C6D12 as an Example
Authors: Chen Jehn‐Shing , Shiau Jiin‐Chyuan , Fang Cheng‐Yu 
Published: May 2015

AbstractWe propose a graphical method to treat dilution shift in NMR spectra to determine the monomer shift, dimer shift and dimerization constant simultaneously and consistently for the system of monomer/dimer equilibrium. The salient features include avoiding error‐prone manual extrapolation to zero concentration to obtain a monomer shift, and providing consistent assessment and error estimation for the determination. The dilution shifts of 2‐isopropyl phenol in C6D12 serve to demonstrate this graphical method. The enthalpy and entropy of dimerization are determined via a van't Hoff plot from the temperature variation of the dimerization constant.
Chelation Properties of Highly Selective and Affinity Polymeric Complexing Agents
Authors: Lee N‐Ming , Liu Chuen‐Ying 
Published: May 2015

AbstractProcedures are described to prepare γ‐aminobutyrohydroxamate resin and its N‐methyl and O‐methyl derivatives. With the aid of a chemical method, IR and electronic spectra, and potentiometry, the chelating properties of these resins are compared with each other. The selectivity of resins for various metals is expected to be comparable to complexing properties of a monomer having a structure similar to that of active groups. This correlation was made quantitatively by measurement of metal capacity, fraction of sorption, pH and period for extraction of half the metal ions, stability constants etc. Not only γ‐aminobutyrohydroxamate resin but also its N‐methyl and O‐methyl derivatives exhibit much potential for application in chelation ion chromatography.
Formation of YBa2Cu408 Thick Films via Spray Pyrolysis
Authors: Sheen Shyang Roeng , Kao Ching Haai , Wu Maw‐Kuen , Chen Dian Hau , Huang Ju‐Chun , Cheng Chien Hong , Chang Chau Ting 
Published: May 2015

AbstractThick films of YBa2Cu4O8 superconductor were prepared by a spray‐pyrolysis coating technique using silver strip as the substrate. The precursor solution consisted of metal nitrates dissolved in a mixture of ethandiol and water. The solution was nebulized onto the heated substrates to obtain films as‐deposited. The temperature of deposition had a great effect on the morphology of the film. Sintering the films in flowing oxygen at 810 °C for 60 h yielded films with Tc(onset) = 82.0 K and Tc(zero) = 74.6 K. Films were characterized by x‐ray diffraction, scanning electron microscopy, transport and magnetic measurements.
Chemical Constituents from the Root and Aerial Parts of Rosa taiwanensis
Authors: Yang Shen‐Chyun , Fang Jim‐Min , Cheng Yu‐Shia 
Published: May 2015

AbstractThe root and aerial parts of Rosa taiwanensis Nakai contain the chemical constituents phenols, unsaturated acids, loliolide, abscisic acid, flavones, sterols, lupeol, betulin, betulinic acid, oleanolic acid and ursolic acid derivatives. Among them, 2α,3α‐dihydroxyurs‐12,19‐dien‐28‐oic acid and its C‐3 epimer are new compounds.
Resolution of Secondary α‐Ketoalcohols Catalyzed by Lipase and Inversion of Stereochemistry
Authors: Duh Tsai‐Hui , Wang Yi‐Fong , Wu Ming‐Jung 
Published: May 2015

AbstractSeveral α‐ketoalcohols of synthetic value were resolved using lipase as a catalyst. Lipoprotein lipase (LPL) provided the best rate of hydrolysis and kinetic differentiation. One of these optically pure α‐ketoalcohol was converted to (5)‐ibuprofen in good optical purity. The stereospecific inversion of (R)‐alcohol to (S)‐alcohol is described.
Synthesis of 2,5 ‐Bis(4‐methyl‐2‐thienyl)thiophene and 2,5‐Bis(4‐methyl‐2‐thienyl)pyrrole
Authors: Luo Thung‐Mei H. , Chen Liang‐Huei 
Published: May 2015

AbstractSyntheses of 2,5‐bis(4‐methyl‐2‐thienyl)thiophene 3 and 2,5‐bis(4‐methyl‐2‐thienyl)pyrrole 4 are described. The key step involves Stetter reaction between 4‐methyl‐2‐thiophenecarboxaldehyde and divinyl sulfone. Cyclizaton of the resulting 1,4‐bis‐(4‐methyl‐2‐thienyl)‐1,4‐butanedione 2 with Lawesson's reagent gives 2,5‐bis(4‐methyl‐2‐thienyl)thiophene 3, whereas condensation with ammonium acetate provides the 2,5‐bis(4‐methyl‐2‐thienyl)pyrrole 4.
Recently Developed Concepts for Studying and Understanding the Aggregation of Organic Molecules. Aggregating Tendencies of the Culprits of Arteriosclerosis
Authors: Jiang Xi‐Kui 
Published: May 2015

AbstractRecent developments in research on aggregation and self‐coiling of organic molecules are reviewed: structure and medium effects on aggregating tendencies, electrostatically stabilized aggregates (ESAg), co‐aggregating tendencies of cholesterols and the effect of chain‐folding, and neutral and effective deaggregators (deAgr).
α‐Carbonyl Radicals for Total Synthesis of Natural Products
Authors: Sha Chin‐Kang , Jean Tsong‐Shin , Yau Nei‐Tung , Huang Shih‐Jung , Chiou Ruey‐Torn , Young Jenn‐Fenn , Lih Shin‐Hong , Tseng Wei‐Hong 
Published: May 2015

AbstractIntramolecular cyclization of α‐carbonyl radicals to the trimethylsilylacetylenic side chain gives bicyclic vinylsilane ketones and enones. Application of this cyclization to total synthesis of (±)‐modhephene is described.
Light Induced Electron Transfer and Charge Separation of Porphyrin Compounds for Photoelectric Conversion
Authors: Cao Yi , Zhang Bao‐Wen , Qian Wen‐Yuan , Bai Jian‐Wei , Xiao Xu‐Rui , Jia Jian‐Guang 
Published: May 2015

AbstractA series of artificial photosynthesis porphyrin compounds consisting of electron donor and electron acceptor (compounds 1‐6) were synthesized. Their spectroscopic behaviors in solution were investigated and the synthetic molecular devices were prepared with these molecules by using LB technique. It was indicated that multistep electron transfer and charge separation for these compounds actually occur, which is of great advantage to their photoelectric conversion. An efficient energy transfer process takes place for compound 6. A mechanism involving photoinduced electron transfer and multistep charge separation for these compounds was suggested. With only one monolayer of tetrad 1 LB film on the surface of Sn02 conductive glass, high photo‐driven voltage and current were obtained.
Conformational Behavior of Rigid and Dancing (1,3)(1,4)Cyclophanes
Authors: Lai Yee‐Hing 
Published: May 2015

AbstractAnnelation or substitution of the (1,4)‐bridged ring of [22](1,3)(1,4)cyclophane 4, such as in 8 and 9, respectively, result in two different conformational ground states in each case. Each conformational ground state involves a different destabilizing factor arising from one form of non‐bonding interaction. Only the conformers 8b and 9b were isolated experimentally. Their corresponding precursors 11 and 23 were also found to be conformationally rigid. Only the conformers 11a and 23a were isolated indicating an abrupt change in conformational preference going from the dithia[32]cyclophanes to the respective [22]cyclophanes. The selectively methylated [22]cyclophanes 27, 31 and 32 were, however, found to be conformationally mobile. There is an increase of about 10–15 kJ mol−1 in conformational energy barrier going from 4 to 27 or 31. This is consistent with the fact that the presence of the methyl substituents increases the relative conformational ground‐state energy more than it would affect the transition‐state energy. The conformational barrier of 32 was unexpectedly found to be similar to those of 27 and 31. This could be explained by a decrease in the transition‐state energy due to an inward bending of the (1,4)‐bridged ring accompanied by a decrease in conformational ground‐state energy due to an outward bending of the methyl groups in 32.
Studies on the Antisense Oligonucleotide Conjugate
Authors: Wang Lai‐Xin , Yang Ding‐Cheng , Lu You‐Yong , Takaki Yasuomi , Taira Kazunari , Li Tong , Zhang Li‐He 
Published: May 2015

AbstractFour oligonucleotides (15 mer) 13–16 and their conjugates 17–20 in which psoralen was covalently linked to 5′ end were synthesized. Compounds 16 and 20 contain the sequence which is complementary to the sense strand covering the first four codons and the upstream sequence close to the ribosome binding site of c‐Ha‐ras mRNA. It was found that compounds 16 and 20 inhibited the growth of cells that had been transformed by the c‐Ha‐ ras plasmid activated c‐Ha‐ ras oncogene. Compound 20 that carried psoralen was more efficient in inhibiting the growth of transformed cells than compound 16 without psoralen, suggesting that the psoralen might have increased permeability of oligodeoxynucleotides. A model experiment of duplex formation was pertinent to the idea that the inhibitory effect was caused by RNase H activity.
A Synthesis of (+)‐Oblongolide
Authors: Shing Tony K. M. , Yang Jun 
Published: May 2015

AbstractThe absolute configuration of natural oblongolide is reassigned as (3aS,5aR,7S,9aS,9bS)‐3a,5a,6,7,8,9,9a,9b‐octahydro‐7,9b‐dimethylnaphtho[1,2‐c]furan‐1(3H)‐one 2 by a 7‐stage synthesis of its enantiomer 1 from (+)‐citronellol involving a regioselective reduction and an intramolecular Diels‐Alder reaction (IMDA) as the key steps. (+)‐Citronellol was converted into methyl (2E,4E,10E)‐(S)‐(+)‐11‐tert‐butoxycarbonyl‐7‐methyl‐undeca‐2,4,10‐trienoate 7 by sequential Lemieux‐Johnson oxidation, Wittig reaction, pyridinium chlorochromate oxidation, and Wadsworth‐Emmons‐Homer alkenation. A regioselective reduction of the methoxycarbonyl group in 7 afforded tert‐butyl (2.E,8E,10E)‐(S)‐(+)‐2,6‐dimethyl‐12‐hydroxy‐dodeca‐2,8,10‐trienoate 8 from which (+)‐oblongolide was readily obtained via an IMDA reaction.
Receptor Mapping by Comparative Molecular Field Analysis of Phospholipase A2 Inhibitors
Authors: Deng Qiaolin , Cao Bin , Lai Luhua 
Published: May 2015

AbstractIn structure‐based design of phospholipase A2 inhibitors, comparative molecular field analysis is performed on known phospholipase A2 (PLA2) inhibitors to build a pseudo‐receptor map of the enzyme, which is compared to maps from probe searches with proton and methane. The pseudo‐receptor map resembled in steric properties to the map from a probe search. Hence known ligands can be used to deduce the shape and chemical properties of the binding site of a receptor. Useful information for drug design can be obtained from such receptor mapping.
Molecular Orbital Calculations on 2, 4, 6‐Trinitrotoluene
Authors: Chen P. C. 
Published: May 2015

AbstractThree ab initio calculations (HF/6‐3IG, HF/6‐3IG*, and HF/6‐3IG**) on 2,4,6‐trinitrotoluene were made, The results compare well with xray data, except dihedral angles of NO2 relative to the plane of the benzene ring. The deviations are attributed to packing forces and steric effects in the crystal. The most stable structure was a torsional angle 10° of the methyl top with the benzene ring, unlike toluene. The rotational barriers of the methyl top and the 4‐nitro group are small. Hydrogen bonding, dipole moments and total atomic charges arc calculated.
Programmed‐Temperature Vaporizing (PTV) Liners to Introduce Chlorinated and Sulfur Compounds into a Capillary Gas Chromatograph
Authors: Sye Wen‐Fa , Shu Chia‐Ching 
Published: May 2015

AbstractIntroduction of a sample at a programmed temperature is an attractive approach both for dilute samples in large volumes and to prevent discrimination inside the syringe needle with this injection into a capillary gas Chromatograph. Quantitative data obtained with glass liners packed with trapping materials including glass wool, Tenax TA, Chromosorb 101 and Thermotrap‐TA to analyze chlorinated and sulfur compounds are compared. To eliminate the solvent, these vapors were vented through the injection port cap, which provided greater efficiency than through the split line.
Resolution of Ibuprofen Catalyzed with Free and Immobilized Lipases
Authors: Tai Dar‐Fu , Huang Chi‐Yuan , Chao Yunn‐Hsin , Luo Jih‐Mei , Lin Yi‐Tsong , Wu Shih‐Hsiung 
Published: May 2015

AbstractEnzymatic hydrolyses of ibuprofen esters produced 99% optically pure S‐(+)‐ibuprofen. The ee values of two enantiomers of ibuprofen were determined on a HPLC equipped with a chiral column.
Formation of Tetraacetal Oxa‐Cages and Convex Oxa‐Cages on Ozonolysis of Bicyclo[2.2.2] Octenes
Authors: Lin Chu‐Chung , Wu Hsieii‐Jen 
Published: May 2015

AbstractTetraacetal oxa‐cage compounds 5a and 5b and convex oxa‐cage compounds 7a and 8b are synthesized in a short sequence. Ozonolysis of endo adducts 2a and 2b in dichloromethane at −78 °C followed by reduction with dimethylsulfide gave tetraacetal oxa‐cages 5a and 5b in 35% yields respectively. Ozonolysis of 2a in dichloromethane at −78 °C followed by treatment with triethylamine gave the convex oxa‐cage 7a in 34% yield. These results support an acid‐base proton transfer between the final ozonides and the base. The reasons that these oxa‐cage compounds formed in low yields are discussed. The synthesis of tetraacetal oxa‐cage 14, possessing aromatic substitutents directly on the skeleton of the oxa‐cage, is accomplished.
Formal Syntheses of (±)‐Verbenalol and (±)‐Udoteatrial
Authors: Tai Huo‐Mu , Yang Chau‐Chen , Chang Nein‐Chen 
Published: May 2015

AbstractA formal total synthesis of (±)‐verbenalol 1 and (±)‐udoteatrial 2 is described. Tie key intermediate is diiodolactone 7.
Oxidation of Tricarbonyl (η1 η2‐but‐3‐en‐1‐yl)iron(0)and Tricarbonyl (η3‐allyl)iron(0) Anion Complexes with Dioxygen
Authors: Hwu Chong‐Chen , Yeh Ming‐Chang P. 
Published: May 2015

AbstractThe addition of reactive carbanions to tricarbonyl(η4‐1,3‐diene)iron(0) complexes proceeded at −78 °C to give putative tricarbonyl(η1,η2‐but‐3‐en‐1‐y1)iron(0) anion complexes and at 25 °C to produce postulated tricarbonyl(η3‐allyl)iron(O) anion complexes; trapping of reactive intermediates with dioxygen produced γ,δ‐unsaturated acids and allylic alcohols, respectively.
Ultrasound Promoted 1, 3‐Dipolar Cycloaddition Reactions of Nitrile Oxides with α, β‐Unsaturated Acetals
Authors: Lu Ta‐Jung , Sheu Lij‐Jyi 
Published: May 2015

AbstractThe 1,3‐dipolar cycloaddition reactions of nitrile oxides and α,β‐unsaturated 1,3‐dioxolanes were effectively accelerated by ultrasound irradiation to give the A2‐isoxazolines with yields and regioselectivities surpassing those of the corresponding thermal reactions.
Effect of Strong Irradiation on Raman Magnetic Resonance in an AX Spin System
Authors: Ye Chaohui , Miao Xija , Jiang Bang‐Chin , Hwangsp Lian‐Pin 
Published: May 2015

AbstractIn Raman magnetic resonance an initially prepared multiple quantum coherence (MQC) in a spin system introduces all the possible single quantum (SQ) and multiple quantum (MQ) NMR signals when an irradiation is applied during the detection period. If the irradiation is weak, the induced signals include those MQs up to the very order of this given MQC, while in the strong irradiation case, those MQs beyond the very order of the given MQC will also appear. An analytical approach based on the product formalism is developed to predict the intensities and frequencies of these induced signals. The analysis provides a complete treatment to cover both cases of weak and strong irradiation. It is also demonstrated with an AX spin system. Experimental results are in qualitative agreement with the analysis.
Multiple Quantum Transitions Induced by Irradiating Single Quantum Coherence in a Heteronuclear Spin System
Authors: Jiang Bang‐Chih , Miao Xijia , Hwang Lian‐Pin , Ye Chaohui 
Published: May 2015

AbstractIn a heteronuclear spin system, with initially prepared single quantum (SQ) coherence of X‐spin, the irradiation of the proton spins will induce all the possible transitions including those SQs and multiple quanta (MQs) available in the system to be studied. The MQs appear in a rather weak irradiation while a strong irradiation results in a complete decoupling situation. Theoretical analysis is made to explain this phenomenon and is agreed qualitatively with experiments in the CH2 group. This phenomenon of MQ induction may happen in a decoupling experiment, when the effective irradiation strength is rather weak and it may also provide a convenient approach to create and then to manipulate MQ coherences in heteronuclear spin systems.
Brønsted Acidity and Aluminum Substitution Characteristics of Si(nAi) Sites in Zeolites: A Theoretical MNDO Calculation
Authors: Prasad S. , Liu Shans‐Bin 
Published: May 2015

AbstractThe Brønsted acidity of the various Si(nAl) sites present in zeolites is evaluated from proton binding energy and LUMO energy calculated by the semiempirical MNDO quantum chemical method. The two calculated energy values both exhibit a linear correlation with the existing 29Si NMR chemical shift and the IR hydroxyl stretching frequency data. The inter‐convertibility between different Si(nAl) sites during an alumination or dealumination process is also evaluated based on the calculated substitution energy. The results indicate that alumination processes are less favorable to occur in zeolites than dealumination processes and the latter is more likely to occur for Si(nAl) clusters that contain the maximum number of aluminum nearest neighbors.