bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic structure of oligoaniline doped by inorganic and organic acids
Authors: Yang Gang , Hou Wenhua , Feng Xiaomiao , Jiang Xuefan , Guo Jin 
Published: February 2008

AbstractThe electronic structure of doped‐oligoaniline with various dopants is investigated by means of DFT method. After doping by hydrochloric acid (HCl) and camphorsulfonic acid (HCSA), the alternation of bond‐lengths is decreased and the co‐planarity of adjacent aromatic rings is increased. The π‐conjugating effect is increased in the electronic nature of Ph‐N system because the electrons can be delocalized along the backbone of oligoaniline where the hydrogen bonds as a bridge transfer the electrons. The electronic structure of polaron and bipolaron conformation and their relative stability is discussed, indicating that the preferable conformation is dependant on various dopants. The calculation results reveal that there is a relatively stronger interaction between the organic dopant of HCSA and N atoms of PANI, and more charge transfer between PANI and HCSA is a reason for the fact that the conductivity of HCSA‐doped PANI is higher than that of HCl‐doped PANI. The doping mechanism is proposed based on the calculation results. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Theoretical study of olefin oxidation process on a dioxo‐μ‐oxo Mo catalyst
Authors: Griffe Beulah , Agrifoglio Giuseppe , Ruette Fernando , Brito Joaquín L. 
Published: February 2008

AbstractThe dimeric complex dioxo (μ‐oxo) thiocyanato of molybdenum(VI) bearing a 4,4′‐di‐ter‐butyl‐2,2′‐bipyridine ligand in trans conformation (complex 1) has been used in catalytic reactions of olefins (ethylene) oxidation, giving as intermediate a dimeric complex oxo bis (μ‐oxo) thiocyanato of molybdenum(V) in cis conformation (complex 2). Binding and electronic properties were calculated using the parametric quantum chemistry method for catalytic reactions, CATIVIC. The interaction of an ethylene molecule with complex 3 (cis version of complex 1) leads to the formation of the intermediate named complex 4. This complex is dissociated to form complex 5 plus ethylene oxide. Changes of electronic and bonding properties are analyzed in terms of atomic charge, orbital population, total binding energies, diatomic bond energies, diatomic energies, and Wiberg indexes, and equilibrium bond distances. The energy balance for the complete catalytic process is presented in a schematic way. Results confirm the extraordinary oxo‐transfer abilities of this complex, considering that the whole process is exothermic (−44 kcal/mol). Regeneration of the catalyst is also calculated by the interaction of H2O2 with complex 5. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Theoretical study of omeprazole behavior: Racemization barrier and decomposition reaction
Authors: Thais Bruni Aline , Castro Ferreira Márcia Miguel 
Published: February 2008

AbstractOmeprazole is a substituted benzimidazole which suppresses gastric‐acid secretion by means of H+, K+‐ATPase inhibition. It is an optically active drug with the sulfur of the sulfoxide being the chiral center. This pro‐drug can be easily converted into its respective sulfenamide at low pH. In this work, omeprazole has been studied in relation to racemization barrier and decomposition reaction. Quantum chemistry coupled to PCA chemometric method were used to find all minimum energy structures. Conformational analysis and calculation of racemization barriers were carried out by PM3 semiempirical method (Gaussian 98). The average racemization energy barrier for all minimum energy structures (43.56 kcal mol−1) can be related to the velocity constant in Eyring's equation. The enormous half‐life time at 100°C (9.04 × 104years) indicates that the process cannot be observed in human time scale. On the other hand, the difference of free energy change (Δ(ΔG) = −266.78 kcal mol−1) for the decomposition reaction shows that the process is favorable to the sulfenamide formation. The highly negative Δ(ΔG) obtained for the decomposition reaction shows that this process is extremely exothermic. This result explains why omeprazole decomposes and does not racemize. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Inductive and resonance effects based on core‐electron binding energy shift
Authors: Takahata Yuji 
Published: February 2008

AbstractIt was shown that core‐electron binding energy shift (ΔCEBE) could be used as a criterion of inductive (and resonant) effect at each ring carbon atom of substituted cyclohexanes (and benzenes). CEBEs were calculated using density‐functional theory with the scheme ΔEKS (PW86‐PW91)/TZP//HF/6‐31G*. The inductive effect thus calculated correlate highly with the Taft inductive effect (σI). The inductive effect in a substituted benzene can be well approximated by that determined in a substituted cyclohexane. Resonant effect was defined as the difference between ΔCEBE of a substituted benzene and ΔCEBE of a substituted cyclohexane. The resonance effect thus defined at para atom in substituted benzenes correlates fairly well with Taft (experimental) resonance effect (σR), very highly with Taft (theoretical) resonance effect (σR, theory) of literature. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Theoretical study of mechanism of cycloaddition reaction between dimethylmethylenesilylene and formaldehyde
Authors: Lu Xiu Hui , Yu Hai Bin , Che Xin , Xiang Ping Ping 
Published: February 2008

AbstractThe mechanism of cycloaddition reaction between singlet dimethylmethylenesilylene and formaldehyde has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy surface, it can be considered in thermodynamics and dynamics that reaction (1) and reaction (4) are the two dominant competitive reaction channels of cycloaddition reaction between dimethylmethylenesilylene and formaldehyde. The reaction process of reaction (1) is that: the two reactants (R1, R2) first form intermediates INT1a and INT1b through two reaction paths, a and b, which are barrier‐free exothermic reactions of 31.8 and 43.9 kJ/mol; then, INT1a and INT1b isomerize to a four‐membered ring product P1 via transition states TS1a and TS1b, with energy barriers of 26.3 and 24.4 kJ/mol. Reaction (4) also has two reaction paths, a and b, each of which consists of three steps are as follows: (i) the two reactants (R1, R2) first form intermediates INT3a and INT3b, which are barrier‐free exothermic reactions of 64.5 and 44.2 kJ/mol. (ii) INT3a and INT3b further react with formaldehyde (R2) to form intermediates INT4a and INT4b, through barrier‐free exothermic reactions of 22.9 and 22.2 kJ/mol. (iii) INT4a and INT4b then isomerize to form silapolycyclic product P4 via transition states TS4a and TS4b, with energy barriers of 39.7 and 29.3 kJ/mol. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Mechanistic investigation of vibrational fine structure in e‐H2 scattering using local complex potential‐based time dependent wave packet approach
Authors: Sarma Manabendra , Adhikari S. , Mishra Manoj K. 
Published: February 2008

AbstractThe structural features of vibrational excitation cross‐sections in resonant e‐H2 scattering have been investigated using a time dependent wave packet approach and a local complex potential to describe the 2Σ H anion. An analysis of the partial contributions to the vibrational excitation cross‐sections reveals that all features of the excitation profile result from simple interference between bound vibrational levels of H2 and H. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Research on the axis shape of an active catheter
Authors: Fu Yili , Li Xianling , Wang Shuguo , Liu Hao , Liang Zhaoguang 
Published: February 2008

AbstractBackgroundAn active catheter is a minimally invasive surgery catheter that can perform deflectable motions. The active catheter can be controlled from outside the body and moves like a snake, utilizing a multi‐joint mechanism with distributed shape memory alloy (SMA) actuators.MethodsIt was considered that the deflection curve of the axis of the catheter is determined by the output force of the SMA actuators. Based on the large deflection theory, the deflection curve equation of the axis of the catheter was derived, using the precise form of the curvature.ResultsThrough experimentation, the axial bending curve shape of the blended active catheter was measured precisely, and the experimental results were compared with the calculation results obtained from the large deflection theory and the circular arc hypothesis. The experimental results show that the curves calculated by large deflection theory are very close to the actual axis curves.ConclusionsAn active catheter prototype has been designed using the theory presented in this paper. Utilizing a vascular model, the active catheter‐based invasive surgery was simulated. The experiment confirmed that the large deflection theory calculation method can be used to guide the design of the active catheter. Copyright © 2008 John Wiley & Sons, Ltd.
Land vehicular propagation channel characterization of BGAN system
Authors: Gambaruto Elvio , Richharia M. , Trachtman Eyal 
Published: February 2008

AbstractThis paper summarizes the results of a measurement campaign, which set out to characterize Inmarsat's broadband global area network extension (BGAN‐X) L‐band land vehicular (LV) channels as a function of elevation angle and candidate antenna systems. Measurements were conducted with three types of directional antennas on motorway routes around London using Inmarsat's Indian Ocean Region (IOR), Atlantic Ocean Region‐East (AOR‐E) and Atlantic Ocean Region‐West (AOR‐W) satellite transmissions, corresponding to elevation angles of, respectively, ∼7.5°, ∼13° and ∼30°. Simultaneous recordings of data on two types of directive receivers enabled correlation of several channel parameters. Statistics were used to refine a baseline model that derived BGAN‐X LV channel parameters by scaling the statistics obtained from an omni‐directional antenna receiver. The measurements demonstrate that Ricean mean and Ricean factor vary significantly over the chosen routes at elevation angles below ∼13°. Further, the Doppler shift of the direct path can be predicted accurately. A qualitative analysis indicates that the multi‐path Doppler spread is generally (not always) caused by uniform scattering around the vehicle over short distances and undergoes spatial filtering due to the receiver antenna. A technique was established to derive statistics of a two‐state Markovian channel model at any specified fading threshold by gathering tracking system state, thereby allowing one to ascertain service expectations and operational parameters such as connection time‐out of a packet‐switched system or reliability threshold of a circuit‐switched system. The technique was used to identify and select appropriate routes, particularly for the IOR and the AOR‐W regions. Data analysis is in progress to establish the reason for the slow variations of signal mean at low‐elevation angles in Ricean conditions and to derive appropriate statistical models. Furthermore, image processing of the video recordings is expected to reveal the extent of optical and RF fades correlation. Copyright © 2008 John Wiley & Sons, Ltd.
Aspects of Latex Particle Size Control for Improved Water Blush Resistance
Authors: Starostin Natasha , Harvey Scott , Carlson Gary 
Published: February 2008

AbstractLatex films have a tendency to “blush” when exposed to water. The swelling of trapped hydrophilic material, which results in pockets with different refractive indices, is proposed as a possible model for blushing. A pressure‐sensitive latex was developed on the basis of this model. The blush was improved by the choice of the surfactant and control of the particle diameter. The resulting latex has an unusual particle growth behavior during polymerization. The particle size distribution (PSD) was characterized by dynamic light scattering (DLS), electron microscopy (SEM/TEM) and atomic force microscopy (AFM). The data are in a good agreement with our proposed growth model. SCANNING 30: 000–000, 2008. © 2008 Wiley Periodicals, Inc.
A novel nano‐bubble inflation method for determining the viscoelastic properties of ultrathin polymer films
Authors: O'connell P. A. , McKenna G. B. 
Published: February 2008

AbstractWe describe a novel experimental technique for measuring the absolute creep compliance of ultrathin polymer films. The method is based on the classical bubble inflation technique for measuring the biaxial creep compliance of films, reduced in size to measure films with thicknesses down to at least 11.3 nm. The method uses the imaging capabilities of the atomic force microscope (AFM) to determine the time evolution of the geometry of nano‐bubbles and thus avoids the problems with data interpretation that can arise due to “contact mechanics” issues when the AFM is used as a direct mechanical testing device. SCANNING 30: 000–000, 2008. © 2008 Wiley Periodicals, Inc.
A simple method for the removal of thiols on gold surfaces using an NH4OH–H2O2–H2O solution
Authors: Kim Dae Jung , Pitchimani Rajasekar , Snow David E. , Hope‐Weeks Louisa J. 
Published: February 2008

AbstractThe removal behavior of self‐assembled monolayers (SAMs) of thiol molecules on a gold substrate by an NH4OH–H2O2–H2O solution was studied using attenuated total reflectance infrared spectroscopy (ATR‐IR) and atomic force microscopy (AFM). Furthermore, the impact of the concentration of NH4OH and H2O2 in the solution and reaction temperature on the SAM removal rate and efficiency was explored. The SAM removal rate and efficiency were significantly influenced by the concentration of NH4OH rather than H2O2. The solution containing the 2 : 1 molar ratio of NH4OH : H2O2 among three different solutions showed the highest removal rate and efficiency in the removal of 11‐mercapto‐1‐undecanol. The increase in the reaction temperature resulted in the enhancement on the SAM removal rate, but it led to the fast delamination of the gold layer. These results may be useful in the regeneration of sensor surfaces relying on gold/thiol chemistry. SCANNING 30: 000–000, 2008. © 2008 Wiley Periodicals, Inc.
Mitigating dead‐time effects during multivariate analysis of ToF‐SIMS spectral images
Authors: Keenan Michael R. , Smentkowski Vincent S. , Ohlhausen James A. (Tony) , Kotula Paul G. 
Published: February 2008

AbstractToF‐SIMS spectra are formed by bombarding a surface with a pulse of primary ions and detecting the resultant ionized surface species using a time‐of‐flight mass spectrometer. Typically, the detector is a time‐to‐digital converter. Once an ion is detected using such detectors, the detector becomes insensitive to the arrival of additional ions for a period termed as the (detector) dead‐time. Under commonly used ToF‐SIMS data acquisition conditions, the time interval over which ions arising from a single chemical species reach the detector is on the order of the detector dead‐time. Thus, only the first ion reaching the detector at any given mass is counted. The event registered by the data acquisition system, then, is the arrival of one or more ions at the detector. This behavior causes ToF‐SIMS data to violate, in the general case, the assumption of linear additivity that underlies many multivariate statistical analysis techniques. In this article, we show that high‐mass‐resolution ToF‐SIMS spectral‐image data follow a generalized linear model, and we propose a data transformation and scaling procedure that enables such data sets to be successfully analyzed using standard methods of multivariate image analysis. Copyright © 2008 John Wiley & Sons, Ltd.
Compatibilizing effect of functionalized polystyrene blends: a study of morphology, thermal, and mechanical properties
Authors: Shabbir Saima , Zulfiqar Sonia , Lieberwirth Ingo , Kausar Ayesha , Sarwar Muhammad Ilyas 
Published: February 2008

AbstractPolystyrene (PS), being an amorphous polymer is immiscible with other polymers. To engender miscible blends, PS has been functionalized with an active amino‐functional group on the molecular chains of PS to yield amino‐substituted polystyrene (APS), which serves as a reactive compatibilizer. The compatibilization effect of amino functionalized polystyrene on the rubber toughening was explored and results were compared in terms of morphology, thermal, and mechanical properties of PS/SEBS‐g‐MA versus APS/SEBS‐g‐MA blends. In addition, the effect of rubber content on the blend morphology and mechanical properties were investigated. An appreciable change in the thermal stability of APS blends in comparison with PS blend has been probed. A marked correlation has been observed between phase morphology and thermal stability. Use of APS produced the compatibilized blends which render improved blend morphology, enhanced thermal and mechanical properties. Optimal thermal, morphological and mechanical profiles were depicted by 20‐wt% APS blend. Copyright © 2008 John Wiley & Sons, Ltd.
Innovative Starch Derivatives as Textile Auxiliaries for Application in Sizing, Finishing and Flocculation
Authors: Hebeish Aly , Aly Amal Ahmed , El‐Shafei Amira Mohamed , Zaghloul Saad 
Published: February 2008

AbstractInnovative starch‐based polymeric products were synthesized for utilization as sizing agents, flocculants, and finishing agents. The synthesis involved reaction of starch and hydrolyzed starches with monochlorotriazinyl‐β‐cyclodextrin (MCT‐β‐CD) to yield starch grafted with cyclodextrin (St‐g‐CD). The latter was further reacted with 3‐chloro‐2‐hydroxypropyltrimethylammonium chloride (Quat‐188) to effect cationization of St‐g‐CD. Grafting of starch with cyclodextrin and cationization with Quat‐188 were concurrently expedited by reacting starch with both MCT‐β‐CD and Quat‐188 in a one‐step process using NaOH as catalyst. Maximization of the reaction of starch‐g‐CD with Quat‐188 (expressed as%N) and the concurrent reaction of starch with MCT‐β‐CD and Quat‐188 could be achieved at 40ºC for 90 and 120 min, respectively, by using NaOH as catalyst at concentrations of 8 and 15 mmol, respectively. These reaction conditions were employed to prepare six innovative polymeric starch derivatives. Derivatives I, II and III represent St‐g‐CD prepared from hydrolyzed starches having different molecular sizes after being cationized with Quat‐188. Derivatives IV, V and VI represent those prepared from reacting the hydrolyzed starch with both MCT‐β‐CD and Quat‐188 in a one‐step process. The six derivatives were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Although all six derivatives bear cyclodextrin and Quat‐188 moieties, their characters and properties differ considerably, which was reflected on their efficiency as flocculants and sizing agents and as additive in durable press finishing (DP) of cotton fabric. The efficiency of the six derivatives when applied in these fields depends on the molecular size of the parent starch, the graft content of the in St‐g‐CD, the extent of cationization and the condition of application. At any event, however, the innovative derivatives in question exhibit salient features which advocate them for application in sizing, flocculation and DP finishing.
Pasting Behavior of Amylose, Amylopectin and Their Mixtures as Determined by RVA Curves and First Derivatives
Authors: Juhász Réka , Salgó András 
Published: February 2008

AbstractThe relationship between amylose to amylopectin ratio and functional properties of maize starch blends (system I) and “model mixtures” (system II) made of waxy and high amylose maize starch were investigated using the Rapid Visco Analyser (RVA). A 4‐5% difference in amylose content caused significant difference in RVA curves and their first derivatives. Based on the first derivative of the RVA curves four different parameters (Peak 2, Peak Time 2, Peak 3, Peak Time 3) were defined. Peak viscosity and parameters were negatively correlated with amylose content confirming that amylopectin is mainly responsible for water uptake. The final viscosity of starch was very high and decreased as amylopectin or amylose was added, indicating that this parameter is the most sensitive to interactions in starch. In system II amount and characteristics of amylopectin seemed to primarily determine the pasting properties. Traditional RVA curves and parameters proved to be feasible to detect the differences between gel properties of the two systems after cooling. First derivative viscograms and alternative parameters seemed to be suitable to demonstrate the importance of interactions between the starch components during gelatinization. Our results confirmed that the Rapid Visco Analyser is a sensitive rheological tool for evaluating effects of starch structure and chemical composition on functional properties providing valuable help for food technologists.
Morphological and Crystalline Properties of Starches from New Sources‐Traditional Chinese Medicines (TCMs)
Authors: Yu Jinglin , Wang Shujun 
Published: February 2008

AbstractIn China, there are many starch‐rich Traditional Chinese Medicines (TCMs) such as Fritillaria, Rhizoma Dioscorea Thunb., Pueraria Lobata Ohwi, Alisma Orientalis Juzep. and Polygonum Multiflorum Thunb. The low‐molecular weight bioactive ingredients present in these TCMs have been studied widely. However, starches are always ignored and discarded during the isolation of the small‐molecule active components, which results in large wastes of TCM resources. In order to understand and explore these new starches, the morphological and crystalline properties of starches from six TCMs have been evaluated. The starches differ in granular shape and size. The F. ussurensis Maxim. (FUM), F. cirrhosa D. Don. (FCD) and Rhizoma Dioscorea Thunb. (RDT) starches have larger granules than the other three TCM starches. Alisma Orientalis Juzep. (AOJ) starch possesses the smallest granules among the six starches. Polygonum Multiflorum Thunb. (PMT) starch has the lowest integrity of granule shape. RDT starch and Pueraria Lobata Ohwi (PLO) starches display the characteristics of typical C‐type diffraction pattern. FUM starch and FCD starch show typical B‐type diffraction pattern. AOJ and PMT starches have the strongest diffraction peaks at 17.8°, 20.1° and 27.4º which is indicative of an A‐type diffraction pattern.