bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlling of Solution Concentration on Nucleation During Hydrothermal Synthesis of Analcime
Authors: Lin I‐Chieh , Lo Huann‐Jih , Song Sheng‐Rong , Fang Jiann‐Neng , Chen Yaw‐Lin , Chen Huei‐Fen , Li Li‐Jun , Liu Chia‐Mei 
Published: May 2015

AbstractHydrothermal experiments of analcime nucleation and glass dissolution were carried out in autoclaves under the conditions of autogeneous pressures, temperatures of 150 °C ∼ 210 °C, and 0.25 M ∼ 0.75 M NaOH solutions. The curves of the glass dissolution and analcime formation are S‐shaped. Yet, the two curves are essentially parallel to each other. The time required for a complete dissolution of glass or the commencement of analcime formation is shorter when the concentration of NaOH solution or the temperature is higher. The amount of the weight percent of analcime synthesized is obviously less than the glass dissolved at a given time of an experiment. The weight difference between glass dissolved and analcime (dehydrated) formed is calculated to be represented as the solution concentration.During an experiment, the solution concentration increases gradually to a maximum, then decreases slowly to a constant value with time. On the other hand, nucleation is also gradually increased to a maximum, then is decreased finally to zero with time in a bell‐shaped curve. It is clear that nucleation of analcime is mainly controlled by the solution concentration.
The HPLC Enantioresolution of Selected Native or Derivatized Amino Acids on Teicoplanin Bonded Chiral Stationary Phase Using a Methanol‐Based Mobile Phase
Authors: Chen Shushi 
Published: May 2015

AbstractThe facile HPLC enantiomeric resolution of a variety of selected native or derivatized amino acids is carried out on the glycopeptide antibiotic teicoplanin bonded chiral stationary phase using a methanol‐based mobile phase and found very sensitive to the structural variations. This mobile phase is mainly composed of methanol. Organic additives such as acetic acid and triethylamine are introduced to the mobile phase in small percentages to control the analyte's retention time. Additive of low viscosity such as ethyl ether or petroleum ether is incorporated in the mobile phase as well to improve the resolution. Further increasing its percentage in the mobile phase deteriorates the resolution slightly; however, it extends the retention scale of enantiomers. The change in enantioselectivity is found to be insignificant under these circumstances. The hydrogen bonding and π‐π complexation in the hydrophobic pocket of teicoplanin chiral selector is believed to be the mechanism mainly responsible for the enantioresolution observed in this report.
Speciation of Arsenic in Environmental and Biological Samples
Authors: Aggarwal S. G. , Diwan B. D. , Agarwal S. , Gupta V. K. , Mundhara G. L. 
Published: May 2015

AbstractA novel arsine generator glass assembly is constructed and reported for the spectrophotometric determination and speciation of arsenic in real samples. In an arsine generator, sodium borohydride is added dropwise to the acidic sample solution and arsine thus formed is reacted with silver diethyldithiocarbamate (Ag‐DDTC) ‐ Tritron‐X (TX‐100) solution in pyridine to form a red coloured complex. The complex showed the absorption maximum at λmax 540 nm. The molar absorptivity of the method was found to be (1.55) × 104 L mole−1 cm−1 at this wavelength. The presence of non‐ionic surfactant, i.e. TX‐100 in the Ag‐DDTC solution, makes the method ≈ 3 times more sensitive than the conventional Ag‐DDTC method. Beer's law is obeyed in the concentration range of 0.05–2.80 mg L−1 of arsenic. The detection limit of the method was calculated to be 20 μg L−1 As. Speciation of arsenite from other forms of arsenic in sample solutions was carried out by extraction of arsenite with Pb‐DDTC in chloroform, followed by spectrophotometric determination. After arsenite separation the sample is used for the arsenate determination. Total arsenic was determined by acid decomposition of the same sample. The speciation data were found to be comparable (±2%) with ICP‐MS, with better precision (< 1%). The method has been successfully applied for the speciation of arsenic in drinking water and dust samples of arsenic affecting the Rajnandgaon district of Chhattisgarh, India, and urine and blood samples of patients with arsenical diseases. Concentration of total arsenic in tube‐well water of this area was 3–6 times more than the permissible limit. Dust samples contained less amounts of arsenic than the ground water.
Synthesis of 2‐Thioxohydropyridine‐3‐Carbonitrile, 2‐Alkylthiopyridine, Thienopyridine, Pyrazolopyridine Derivatives and Their Theoretical Calculations
Authors: Attaby Fawzy A. , Elghandour Ahmed H. H. , Mustafa Hussein M. , Ibrahem Yasser M. 
Published: May 2015

AbstractCyanothioacetamide (1) reacted with but‐2‐enal (2) to give the corresponding 4‐methyl‐2‐sulfanylpyridine‐3‐carbonitrile (7) which was used as a good starting material for the synthesis of 1‐(3‐amino‐4‐methylthieno[2,3‐b]pyridin‐2‐yl)ethan‐1‐one (10), 3‐amino‐4‐methylthieno[2,3‐b]pyridine‐2‐carboxamide (15), 3‐amino‐4‐methylthieno[2,3‐b]pyridine‐2‐carboxylate (18) and 3‐amino‐4‐methylthieno[2,3‐b]pyridin‐2‐ylarylketone 25a‐c through its reactions with each of (1‐chloroacetone (8), 3‐chloropentane‐2,4‐dione (11) or ethyl 2‐chloro‐3‐oxo‐butanoate (19)), 2‐chloroacetamide (13), ethyl 2‐chloroacetate (16) and 2‐bromo‐1‐arylethan‐1‐one 23a‐c, respectively. Considering the data of elemental analyses, IR, 1HNMR, mass spectra and theoretical calculations, structures of the newly synthesized heterocyclic compounds were elucidated.
Chemical Constituents of Two Liverworts Metacalypogeia Alternifolia and Chandonanthus Hirtellus
Authors: Shy Horng‐Shing , Wu Chia‐Li , Paul Claudia , König Wilfried A. , Ean Uni‐Juni 
Published: May 2015

AbstractA novel linear dihydrodichromene derivative, metacalypogin, was identified from the Taiwanese liverwort Metacalypogeia alternifolia. Together with data from M. cordifolia, the chemical marker of the genus Metacalypogeia is obvious chroman derivatives, which is far different from that of Calypogeia, the other genus in the same family. In addition, two isomeric diterpenoids of cembrane‐type were identified from the Chinese liverwort Chandonanthus hirtellus. The relative stereostructures of the latter two isomers were proved by X‐ray crystallography. Both compounds were unstable in chloroform solution and further oxidized to the corresponding peroxy hemiacetal derivatives.
Complex Formation between the Lumenal Domain of Adenovirus E3–19k Protein and the Extracellular Domain of Class I MHC Molecule In Vitro
Authors: Liao Ping‐Hsi , Chen Te‐Hsiang , Liao Pei‐Yu 
Published: May 2015

AbstractThe Ad2 E3–19k protein inhibits the transport of newly synthesized class I MHC molecules to the cell surface, thereby interfering with antigen presentation. The details of the interaction between E3–19k protein and class I MHC molecules have not been well‐defined. In this present study, we describe the use of gel filtration HPLC for confirming the binding interaction of two domain proteins, E3–19k and MHC class I antigen, and subsequently the characterization of protein complex by SDS‐PAGE. Our results demonstrate the complex formation between Ad2 lumenal E3–19k (108 amino acids, wt 108) and HLA‐A*0201 molecule in vitro. Titration experiments will be employed in the future to determine stoichiometry and verify the specific interactions.
Comparative Adsorption of Lead(II) on Flake and Bead‐Types of Chitosan
Authors: Wan Ngah W. S. , Ab Ghani S. , Hoon L. L. 
Published: May 2015

AbstractThe adsorption of Pb(II) ions from aqueous solutions by chitosan flakes and beads was studied. The chitosan beads were prepared by casting an acidic chitosan solution into alkaline solution. Experiments were carried out as a function of pH, agitation period and initial concentration of Pb2+ ions. The uptake of Pb2+ ions from aqueous solution was determined from changes in concentration as measured by atomic absorption spectroscopy. The maximum uptake of Pb2+ ions on chitosan beads was greater than that on chitosan flakes. Adsorption isothermal data could be interpreted by the Langmuir equation. The experimental data of the adsorption equilibrium from Pb2+ ion solutions correlated well with the Langmuir isotherm equation. SEM analyses were also conducted for visual examination of the chitosan flakes and beads. Physical properties including surface area and average pore diameter were characterized by N2 adsorption experiment.
New Applications of an Old Theory ‐ the Rouse Theory ‐ in Polymer Dynamics and Viscoelasticity
Authors: Lin Y.‐H. 
Published: May 2015

AbstractAs recently shown by a close agreement between the calculated and measured viscoelastic spectra of a binary blend solution over a wide frequency range, the quantitative validity of the Rouse theory is discussed, pointing out why the traditional way of testing by a single parameter ‐ the viscosity ‐ is misleading. A “bird's‐eye” view of the Rouse theory in relation to various aspects of polymer dynamics and viscoelasticity is shown. This represents a fresh way of looking at some of interrelations between fundamental problems in chain dynamics. This paper illustrates the application potential of the Rouse theory by reviewing the research schemes that make use of the well‐tested theory to elucidate two fundamental problems: (1) onset of entanglement and (2) the motions associated with a single Rouse segment. It is shown that through careful designs of research, analyses in terms of the Rouse theory can provide vitally important and informing results.
Femtosecond Fluorescence Dynamics of trans‐Azobenzene in Hexane on Excitation to the S1(n, π*) State
Authors: Lu Ying‐Chih , Chang Chih‐Wei , Diau Eric Wei‐Guang 
Published: May 2015

AbstractFemtosecond fluorescence dynamics of trans‐azobenzene in hexane have been investigated on excitation to the S1(n, π*) state at 432 nm using the up‐conversion technique. Two transient components were observed to represent the fast and the slow S1 fluorescence dynamics in the wavelength range of 550–732 nm. Based on the results obtained from recent ab initio calculations (Ishikawa, T.; Noro, T.; Shoda, T., J. Chem. Phys. 2001, 115, 7503), a dynamical picture is given in the following. Upon initial excitation to the S1 state, the excited molecule is moving away from the first detection window within the observed 200–300 fs. The structural relaxation from the Franck‐Condon region may be responsible for the observed fast S1 dynamics with the driving force being the CNNC twisting motion along the rotational coordinate. For the rest of the motion on the S1 global potential surface, the excited molecule may search for the S0/S1 conical intersection for an efficient internal conversion to the ground state. The nuclear motions for the observed slow S1 dynamics not only involve the CNNC torsional coordinate but also the other degrees of freedom such as the CNN bending coordinate on the multidimensional S1 potential energy surface. The whole electronic relaxation process occurs within the observed 1–2 ps. The slow S1 dynamics were found to vary with the fluorescence wavelengths due to the influence of the solvent‐induced vibrational relaxation in the S1 state; the vibrational relaxation should occur on a time scale comparable to the time scale of the electronic relaxation (S1→S0 internal conversion).
Molecular Rydberg States and Ionization Energy Studied by Two‐Photon Resonant Ionization Spectroscopy
Authors: Chen Yit‐Tsong 
Published: May 2015

AbstractIn this article, I will review the excited valence/Rydberg states and ionization energies of vinyl chloride, propyne, and allyl radical that we have examined recently in our laboratory by 2+1 resonance enhanced multiphoton ionization (REMPI) spectroscopy. In these studies, we have emphasized spectroscopic investigations from the first excited electronic states to the first ionization energies of the molecules and radicals of interest. In spectroscopic analysis, successful electronic identifications have been facilitated with theoretical (ab initio and density functional) calculations. In particular, we have applied calculated Franck‐Condon factors to assist vibrational assignment for experimental vibronic spectra. The spectroscopic studies of these polyatomic excited valence/Rydberg states help us to illuminate the photodissociation pathways and to manifest the complicated chemical‐reaction mechanisms due to the multi‐dimensionality in polyatomic molecular potential energy surfaces.
On the First Overtone Spectra of Protonated Water Clusters [H+(H2O)3–5] in the Free‐OH Stretch Region
Authors: Wu C.‐C. , Chaudhuri C. , Jiang J. C. , Lee Y. T. , Chang H.‐C. 
Published: May 2015

AbstractThe gas‐phase near‐infrared spectra of protonated water clusters [H+(H2O)n, n = 3–5] have been obtained using a vibrational predissociation ion trap spectrometer coupled with a tunable optical parametric oscillator laser. The spectral bands in the frequency range from 7000 to 7500 cm−1 are assigned to the first overtone vibrations of non‐hydrogen‐bonded (free) OH stretches. Assignments of the spectra are made with reference to the data for H2O vapor, (H2O)2 in Ar matrices, and considering the presence of the excess proton in the clusters. Blue shifts of the bands are observed to increase with cluster size and are interpreted in terms of a charge screening effect. The observations have allowed determination of the anharmonicity coefficients of these cluster ions on the basis of the calculations using the term value expression of vibrational energy.
Local Structure and Electronic States of Li(Mn2‐xCox)O4 Studied by X‐ray Absorption Spectroscopy
Authors: Shen C. H. , Liu R. S. , Jang L.‐Y. , Lee J. F. , Chen J. M. 
Published: May 2015

AbstractThe local structure and electronic states of Co3+ substituted lithium manganate spinels of the composition Li(Mn2‐xCox)O4 (0 ≤ x ≤ 0.4) have been probed by X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS) spectroscopies at the Mn and Co edges. The substitution of Co3+ into the Mn sites causes an oxidation of Mn3+ to Mn4+, decreasing the localized Jahn‐Teller distortion of the lattice. This in turn leads to a shortening of the Mn‐O(M) bond length and a reduction in local structural disorder of the Mn(Co)O6 octahedra. The data show that the replacement of d4 Mn3+ by d6 Co3+ in the octahedral sites of the spinel structure eliminates the local disorder in the lattice around the Mn3+O6 octahedra which are distorted by Jahn‐Teller stabilization of the electronic state.
Functionalization of Molecularly Templated Mesoporous Silica
Authors: Yang Chia‐Min , Chao Kuei‐Jung 
Published: May 2015

AbstractThis review describes the chemistry of the formation and functionalization of molecularly templated mesoporous silica, as well as applications of functionalized mesoporous silica. The functionalization can be selectively placed on the internal or external surfaces, or even within the pore walls of mesoporous silica. Applications of functionalized mesoporous silica are highlighted on catalysis, sorption and separation, host‐guest synthesis of nanostructured materials and microelectronics.
Octasilsesquioxane Chemistry I. Attachment of Four Surface Bridges to Octasilsesquioxane Quasi‐cube Framework
Authors: Liu Ling‐Kang , Chu Jiane‐Bond , Slanina Zdenek , Chow Tahsin J. 
Published: May 2015

AbstractThe Pt/C catalyzed hydrosilylation of Si8O12(CH=CH2)8 and 8 equiv of HSiMe2Cl produced Si8O12(CH2CH2SiMe2Cl)8 that was de‐hydrochlorinated with 4 equiv of Z‐HOCH2CH2=CHCH2OH in the presence of excess TMEDA. This preparation resulted in the attachment of four surface bridges (‐CH2CH2SiMe2OCH2CH=CHCH2OSiMe2CH2CH2‐Z‐) on the quasi‐cube Si8O12 framework. As a parallel study, the theoretical calculations of Si8O12(‐CH2CH2SiH2OCH2CH=HCH2OSiH2CH2CH2‐Z‐)4 were carried out at PM3 semi‐empirical level to find optimized geometries for use in four subsequent ab initio computations using standard basis sets of 3–21G* and 6–31G*. The calculations suggest that one should expect about equimolar mixture of the tetra‐adducts produced by the bridging over the edges of the quasi‐cube, either over four parallel edges or over two orthogonal pairs of parallel edges, but not by bridging across the faces of the quasi‐cube.
Studies on the Reaction of α‐Chloroformylarylhydrazine Hydrochloride with Imidazole and 1,2,4‐Triazole
Authors: Chiu Chun‐Yen , Chung Jen‐Hua , Kuo Wen‐Fa , Yeh Mou‐Yung 
Published: May 2015

Abstractα‐Imidazolformylarylhydrazine 2 and α‐[1,2,4]triazolformylarylhydrazine 3 have been synthesized through the nucleophilic substitution reaction of 1 with imidazole and 1,2,4‐triazole, respectively. 2,2′‐Diaryl‐2H,2′H‐[4,4′]bi[[1,2,4]‐triazolyl]‐3,3′‐dione 4 was obtained from the cycloaddition of α‐chloroformylarylhydrazine hydrochloride 1 with 1,2,4‐triazole at 60 °C and in absence of n‐Bu3N. The inducing factor for cycloaddition of 1 with 1,2,4‐triazole was ascertained as hydrogen ion by the formation of 4 from the reaction of 3 with hydrochloric acid. 4 was also acquired from the reaction of 3 with 1 and this could confirm the reaction route for cycloaddition of 1 with 1,2,4‐triazole. Some acylation reagents were applied to induce the cyclization reaction of 2 and 3.1 possessing chloroformyl group could induce the cyclization of 2 to give 2‐aryl‐4‐(2‐aryl‐4‐vinyl‐semicarbazide‐4‐yl)‐2,4‐dihydro‐[1,2,4]‐triazol‐3‐one 6. 7 was obtained from the cyclization of 2 induced by some acyl chlorides. Acetic acid anhydride like acetyl chloride also could react with 2 to produce 7D. 5‐Substituted‐3‐aryl‐3H‐[1,3,4]oxadiazol‐2‐one 8 was produced from the cyclization reaction of 3 induced by some acyl chlorides or acetic acid anhydride. The 1,2,4‐triazole group of 3 played a role as a leaving group in the course of cyclization reaction. This was confirmed by the same product 8 which was acquired from the reaction of 1, possessing a better leaving group: Cl, with some acyl chlorides or acetic acid anhydride.
Hypervalent Iodine(III) Mediated Synthesis of 2‐Substituted‐5‐Aryloxazoles
Authors: Kang Iou‐Jiun , Wang Huey‐Min , Lin Mei‐Ling , Chen Ling‐Ching 
Published: May 2015

AbstractA direct and efficient method for the preparation of 2‐substituted‐5‐aryloxazoles was realized by reaction of aryl methyl ketones with various nitriles in the presence of phenyliodine(III) triflate.
Synthesis of Pyrimidines, Thienopyrimidines and Pyrazolopyrimidine
Authors: El‐Dean Ade L. M. Kamal , Abdel‐Moneam Maisa E. 
Published: May 2015

Abstract5‐Ethoxycarbonyl‐4‐methyl‐2‐phenylpyrimidin‐6(1H)‐thione (3), which was prepared from the reaction of ethyl β‐aminocrotonate 1 with benzoyl isothiocyanate (2) in refluxing acetone, was reacted with halo compounds to give S‐alkyl derivatives 4a‐h. Treatment of compounds 4a‐c with sod. ethoxide cyclized into thienopyrimidine 10a‐c. Hydrazinolysis of compound 3 gave hydroxypyrazolopyrimidine derivative 6. Also the latter compound was obtained upon heating compound 4a with hydrazine hydrate under neat conditions, but when compound 4a refluxed with hydrazine hydrate in ethanol the corresponding carbohydrazide 5 was produced.
Novel Cyanine Dyes: Synthesis, Characterization and Photosensitization‐Structure Correlation
Authors: Shindy H. A. , El‐Maghraby M. A. , Eissa F. M. 
Published: May 2015

AbstractNovel furo, thieno and pyrrolo[2,3‐b]pyrazole cyanine dyes were synthesized. The structure‐photosensitization properties correlation of the dyes were examined in 95% ethanol solution by absorption spectroscopy. The chemical structure of the starting biheterocyclic compounds and their derived cyanine dyes were confirmed by elemental analysis, IR and 1H NMR spectroscopy.
Synthesis of 2,2′‐Biflavanones from Flavone via Electrolytic Reductive Coupling
Authors: Chen Arh‐Hwang , Cheng Chieh‐Yuan , Chen Chia‐Wen 
Published: May 2015

AbstractFlavone (1) was easily reduced by using the electrochemical method to give two hydrodimers of 2,2′‐biflavanone(racemate) (5a) and 2,2′‐biflavanone(meso) (5b) and one reductive product of flavanone (6). Their yields were dependent on the nature of electrodes, the kinds of supporting electrolytes and the reaction temperature. They were found to afford higher yields of 2,2′‐biflavanone(racemate) (5a) and 2,2′‐biflavanone (meso) (5b) (32.4% and 24.8%, 35.8% and 13.4%, respectively,) in the reaction conditions of Pb(‐)/C(+)‐H2SO4‐7F/mol and C(‐)/C(+)‐H2SO4‐5F/mol.
CeCl3/Sm System Induced Reductive Cleavage of the Se‐Se Bond in Diaryl Diselenides: A Novel Method for the Synthesis of β‐Selenoesters and β‐Selenonitriles
Authors: Li Xue , Zhang Songlin , Wang Yulu , Zhang Yongmin 
Published: May 2015

AbstractThe Se‐Se bond in diselenides was reduced by CeCl3/Sm system to produce selenolate anions, which react with α,β‐unsaturated esters or α,β‐unsaturated nitriles to afford β‐selenoesters and β‐selenonitriles, respectively.
1,3‐Dicyclohexylcarbodiimide, an Effective Activating Agent for H‐Phosphonate Chemistry
Authors: Padiya Kamlesh J. , Mohe Nikhil U. , Patil Prashant S. , Pal Ravindra R. , Salunkhe Manikrao M. 
Published: May 2015

Abstract1,3‐Dicyclohexylcarbodiimide (DCC) has been exploited as an activating agent for nucleoside‐H‐phosphonates in the solution as well as solid phase synthesis of oligonucleotide and is effective in terms of speed and coupling efficiency.
Mononuclear Iron(III) and Manganese(III) Complexes with Substituted Salicylaldimine Ligands: Structure, Magnetic Properties, and Catalytic Activity of Olefins‐Epoxidation
Authors: Cheng Sheng‐Chuan , Chang Cheng‐Wei , Wei Ho‐Hsiang , Lee Gene‐Hsiang , Wang Yu 
Published: May 2015

AbstractTwo mononuclear manganese(III) and iron(III) complexes with substituted salicylaldimine ligands, [MnL(H2O)2]Cl·H2O (1) and [FeL(H2O)(Cl)]CH3CN (2) [H2L = N,N′‐(1,1‐cyclohexane)bis(3‐methoxysalicylaldimine)] were prepared and characterized. The X‐ray crystal structure shows that 1 and 2 centers are six‐coordinate with distorted octahedral geometry. In 1, the hydrogen bonding of water molecules form a quasi one‐dimensional chain structure. The temperature dependence of magnetic susceptibility measurements for complexes of 1 and 2 was analyzed in terms of the zero‐field splitting (D) spin‐Hamiltonian formula with D = 2.0 cm−1 for 1 and J = 7.5 cm−1, and D = 0.01 cm−1 for 2, respectively. The complexes of 1 and 2 activate the epoxidation of cis‐stilbene or α‐methylstyrene by NaOCl. With 1 the epoxides were produced in 75% yield with cis:trans = 12:88 from cis‐stilbene and 82% from α‐methylstyrene, and with 2 the epoxides were produced in 43% with cis:trans = 30:70 from cis‐stilbene and 71% from α‐methylstyrene.
Synthesis and Crystal Structure of Tristropocryptands
Authors: Shindo Kimio , Wakabayashi Hidetugu , Kurihara Teruo , Zhang Luo‐Chenz , Ebata Keisuke , Sakurai Hideki , Nozoe (The Late) Tetsuo 
Published: May 2015

AbstractTreatment of benzo[b]cyclohepta[e][1,4]oxazines (4) with 1.2 equiv. of tris(2‐aminoethyl)amine (13) in methanol at 80 °C gave 1,4,12,15,18,26,31,39‐octaazapentacyclo[13.13.13.05,11.019,25.032,3]pentetraconta‐4,6,8,10,18,20,22,24,31,33,35,37‐dodecacenes (14), armed tropocoronands (15), and tropopodands (16). The structure of tristropocryptand 14a was determined by the X‐ray diffraction method.