bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical study of mechanism of cycloaddition reaction between dimethylmethylene carbene and formaldehyde
Authors: Lu Xiu Hui , Wu Wei Rong , Che Xin , Han Jun Feng , Shi Le Yi 
Published: June 2009

AbstractThe cycloaddition mechanism of forming a polycyclic compound between singlet dimethylmethylene carbene(R1) and formaldehyde(R2) 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 the different conformations are calculated with CCSD(T)//MP2/6‐31G* method. From the potential energy profile, it can be predicted that the dominant reaction pathway of the cycloadditional reaction between singlet dimethylmethylene carbene and formaldehyde consists of two steps: (1) the two reactants(R1, R2) firstly form an energy‐enricheded intermediate (INT1a) through a barrier‐free exothermic reaction of ΔE = 11.3 kJ/mol. (2) Intermediate (INT1a) then isomerizes to a three‐membered product (P1) via a transition state (TS1a) with an energy barrier of 20.0 kJ/mol. The dominant reaction has an excellent selectivity and differs considerably from its competitive reactions in reaction rate. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Theoretical study of mechanism of forming a silapolycyclic compound between methylenesilylene and acetone
Authors: Tian Chun Liang , Yu Hai Bin , Lu Xiu Hui 
Published: June 2009

AbstractThe mechanism of the cycloaddition reaction of forming a silapolycyclic compound between singlet methylenesilylene and acetone 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 the different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy profile, we predict that the cycloaddition reaction of forming a silapolycyclic compound between singlet methylenesilylene and acetone has two competitive dominant reaction pathways. First dominant reaction pathway consists of four steps: (I) the two reactants (R1, R2) first form an intermediate (INT1) through a barrier‐free exothermic reaction of 46.2 kJ/mol; (II) intermediate (INT1) then isomerizes to a planar four‐membered ring product (P3) via transition state (TS3) with an energy barrier of 47.1 kJ/mol; (III) planar four‐membered ring product (P3) further reacts with acetone (R2) to form an intermediate (INT4), which is also a barrier‐free exothermic reaction of 40.0 kJ/mol; (IV) intermediate (INT4) isomerizes to a silapolycyclic compound (P4) via transition state (TS4) with an energy barrier of 57.0 kJ/mol. Second dominant reaction pathway consists of three steps: (I) the two reactants (R1, R2) first form a four‐membered ring intermediate (INT2) through a barrier‐free exothermic reaction of 0.5 kJ/mol; (II) INT2 further reacts with acetone (R2) to form an intermediate (INT5), which is also a barrier‐free exothermic reaction of 45.4 kJ/mol; (III) intermediate (INT5) isomerizes to a silapolycyclic compound (P5) via transition state (TS5) with an energy barrier of 49.3 kJ/mol. P4 and P5 are isomeric compounds. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Theoretical studies on the mechanism of formation of a heteropolycyclic germanic compound between dimethyl‐germylidene and ethylene
Authors: Tian Chun Liang , Xu Yue Hua , Lu Xiu Hui 
Published: June 2009

AbstractMechanism of the cycloadditional reaction between singlet dimethyl‐germylidene (R1) and ethylene (R2) 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 the different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy profile, it can be predicted that the dominant reaction pathway of the cycloadditional reaction of forming a heteropolycyclic germanic compound between singlet dimethyl‐germylidene and ethylene consists of three steps: (1) the two reactants (R1, R2) first form a three‐membered intermediate (INT1) through a barrier‐free exothermic reaction of 39.6 kJ/mol. (2) Three‐membered intermediate (INT1) isomerizes to an active four‐membered intermediate (INT2) via a transition state (TS2), for which the barrier is 50.1 kJ/mol. (3) Four‐membered intermediate (INT2) reacts further with ethylene (R2) to form a heteropolycyclic germanic compound (P3), which is also a barrier‐free exothermic reaction of 87.7 kJ/mol. This dominant reaction has an excellent selectivity and differs considerably from its competitive reactions in thermodynamic property and reaction rate. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Rapid separation and identification of furocoumarins in Angelica dahurica by high‐performance liquid chromatography with diode‐array detection, time‐of‐flight mass spectrometry and quadrupole ion trap mass spectrometry
Authors: Zhang Hai , Gong Chungui , Lv Lei , Xu Yuanjie , Zhao Liang , Zhu Zhenyu , Chai Yifeng , Zhang Guoqing 
Published: June 2009

AbstractHigh‐performance liquid chromatography with diode‐array detection (HPLC/DAD), time‐of‐flight mass spectrometry (HPLC/TOFMS) and quadrupole ion trap mass spectrometry (HPLC/QITMS) were used for separation, identification and structural analysis of furocoumarins in Angelica dahurica. Two furocoumarins (imperatorin and isoimperatorin) in Angelica dahurica extract were identified unambiguously by comparing their relative retention times, characteristic ultraviolet information and accurate mass measurement. A formula database of known furocoumarins in Angelica dahurica was established, against which the other 21 furocoumarins were identified effectively based on the accurate extract masses and formulae acquired by HPLC/TOFMS. In order to distinguish the isomers, multi‐stage mass spectrometry (MSn, ion trap mass spectrometry) was used. General fragmentation behavior of the furocoumarins in the ion trap mass spectrometer was studied by the two furocoumarin standards, and their fragmentation rules in MSn spectra were summarized. These deduced fragmentation rules of furocoumarins were successfully implemented in distinguishing the three groups of isomers in Angelica dahurica by HPLC/QITMS. By using the three different analytical techniques, 23 furocoumarins in Angelica dahurica were tentatively identified within 30 min. Finally, HPLC/TOFMS fingerprints of Angelica dahurica were established by which it can be concluded that a rapid and effective method based on the three analytical techniques for identification of chemical components was established. This can provide help for further quality control of Angelica dahurica and pharmacology mechanism study of furocoumarins in Angelica dahurica. Copyright © 2009 John Wiley & Sons, Ltd.
High‐temperature mass spectrometric study of the vaporization processes in the system CaO‐MgO‐Al2O3‐Cr2O3‐FeO‐SiO2
Authors: Wang L. J. , Stolyarova V. L. , Lopatin S. I. , Seetharaman S. 
Published: June 2009

AbstractKnudsen effusion mass spectrometry was used to study vaporization processes and thermodynamic properties of twenty samples of chromium‐containing slags in the CaO‐MgO‐Al2O3‐Cr2O3‐FeO‐SiO2 system in the temperature range 1850–2750 K. Tungsten cells were used and Cr2O3 solid was used as a reference material. The system was calibrated using liquid gold. As FeO was the first emanating vapor species, monitoring of the chromium‐containing species could be carried out only after the complete vaporization of FeO. This, however, was found to have very little impact on the concentration of the slags investigated. During the measurements, the ion current intensities of CrO+ and CrO species in the mass spectra of the vapor over the CaO‐MgO‐Al2O3‐Cr2O3‐FeO‐SiO2 samples were monitored and compared with those corresponding to solid Cr2O3. Data on the partial pressures of vapor species as well as the activities of Cr2O3 as a function of temperature were obtained. The results are expected to be valuable in the optimization of slag composition in high alloy steelmaking processes. Copyright © 2009 John Wiley & Sons, Ltd.
Probing the limits of liquid droplet laser desorption mass spectrometry in the analysis of oligonucleotides and nucleic acids
Authors: Hoffmann Jan , Schmidt Thorsten. L. , Heckel Alexander , Brutschy Bernd 
Published: June 2009

AbstractIn the present work we demonstrate the advantages of LILBID mass spectrometry (laser‐induced liquid bead ion desorption) in the analysis of nucleic acids and large oligonucleotides. For established methods like matrix‐assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI), the mass analysis of oligonucleotides or of noncovalent oligonucleotide‐protein complexes, in particular of very large ones, still represents a considerable challenge either due to the lack of native solutions or nonspecific adduct formation or due to a reduced salt tolerance or a high charge state of the ions. With LILBID, oligonucleotides, solvated in micro‐droplets of aqueous buffer at certain pH and ion strength, are brought into the gas phase by laser ablation. We show that our method is able to detect single‐ and double‐stranded oligonucleotides with high softness, demonstrated by the buffer dependence of the melting of a duplex. The absolute sensitivity is in the attomole range concomitant with a total analyte consumption in the femtomole region. The upper mass limit of oligonucleotides still detected with good signal‐to‐noise ratio with LILBID is the 1.66 MDa plasmid pUC19. With DNA ladders from short duplexes with sticky ends, we show that LILBID correctly reflects the relative thermodynamic stabilities of the ladders. Moreover, as an example for a specific DNA–protein complex we show that a NF‐κB p50 homodimer binds sequence specifically to its match DNA. In summary we demonstrate that LILBID, although presently performed only with low mass resolution, due to these advantages, is an alternative mass spectrometric method for the analysis of oligonucleotides in general and of specific noncovalent nucleic acid–protein complexes in particular. Copyright © 2009 John Wiley & Sons, Ltd.
Compatibility of electron ionization and soft ionization methods in gas chromatography/orthogonal time‐of‐flight mass spectrometry
Authors: Hejazi Leila , Ebrahimi Diako , Hibbert D. Brynn , Guilhaus Michael 
Published: June 2009

AbstractOrthogonal acceleration time‐of‐flight (oa‐TOF) mass spectrometry (MS) was coupled to gas chromatography (GC) to measure ion yields (ratio of ion counts to number of neutrals entering the ion source) and signal‐to‐noise (S/N) in the electron ionization (EI) mode (hard ionization) as well as in the soft ionization modes of chemical ionization (CI), electron capture negative ion chemical ionization (NICI) and field ionization (FI). Mass accuracies of the EI and FI modes were also investigated. Sixteen structurally diverse volatile organic compounds were chosen for this study. The oa‐TOF mass analyzer is highly suited for FI MS and provided an opportunity to compare the sensitivity of this ionization method to the more conventional ionization methods. Compared to the widely used quadrupole mass filter, the oa‐TOF platform offers significantly greater mass accuracy and therefore the possibility of determining the empirical formula of analytes. The findings of this study showed that, for the instrument used, EI generated the most ions with the exception of compounds able to form negative ions readily. Lower ion yields in the FI mode were generally observed but the chromatograms displayed greater S/N and in many cases gave spectra dominated by a molecular ion. Ion counts in CI are limited by the very small apertures required to maintain sufficiently high pressures in the ionization chamber. Mass accuracy for molecular and fragment ions was attainable at close to manufacturer's specifications, thus providing useful information on molecular ions and neutral losses. The data presented also suggests a potentially useful instrumental combination would result if EI and FI spectra could be collected simultaneously or in alternate scans during GC/MS. Copyright © 2009 John Wiley & Sons, Ltd.
Hydrophilic interaction chromatography/tandem mass spectrometry for the simultaneous determination of three polar non‐structurally related compounds, imipenem, cilastatin and an investigational β‐lactamase inhibitor, MK‐4698, in biological matrices
Authors: Xu Yang , Xie Wei , Miller‐Stein Cynthia M. , Woolf Eric J. 
Published: June 2009

AbstractA method coupling hydrophilic interaction chromatography (HILIC) with tandem mass spectrometry (MS/MS) has been developed for the simultaneous determination of three polar non‐structurally related compounds – a carbapenem antibiotic, imipenem (IMP), a renal dehydropeptidase inhibitor, cilastatin (CIL), and an investigational β‐lactamase inhibitor, MK‐4698 (BLI), in rat plasma, monkey plasma and mouse blood. The analytes were extracted through protein precipitation, chromatographed on a Waters Atlantis HILIC column, and detected on a Sciex API4000 mass spectrometer using a Turbo‐Ion Spray ion source in positive ionization mode following multiple‐reaction monitoring (MRM). The assay dynamic range was 0.1–100 µg/mL for IMP, CIL and BLI, respectively, using a total of 20–25 µL biologic samples, and the total HPLC/MS/MS run time was 4 min/injection. The assay was found to be sensitive, selective and reproducible. The challenges, namely, sample stability, blood sample processing, matrix effect in monkey study samples, and dilution re‐assays for the limited mouse blood samples, are resolved and discussed. This technique allowed rapid analysis of polar compounds in biologic matrixes with satisfactory chromatographic retention and increased throughput. Copyright © 2009 John Wiley & Sons, Ltd.
Using multivariate statistical methods to model the electrospray ionization response of GXG tripeptides based on multiple physicochemical parameters
Authors: Raji M. A. , Fryčák P. , Temiyasathit C. , Kim S. B. , Mavromaras G. , Ahn J.‐M. , Schug K. A. 
Published: June 2009

AbstractResponse factors were determined for twelve GXG peptides (where G stands for glycine and X is any of alanine [A], arginine [R], asparagine [N], aspartic acid [D], glycine [G], histidine [H], leucine [L], lysine [K], phenylalanine [F], serine [S], tyrosine [Y], valine [V]) by electrospray ionization mass spectrometry (ESI‐MS). The response factors were measured using a novel flow injection method. This new method is based on the Gaussian distribution of analyte concentration resulting from band‐broadening dispersion experienced by the analyte upon passage through an extended volume of PEEK tubing. This method removes the need for preparing a discrete series of standard solutions to assess concentration‐dependent response. Relative response factors were calculated for each peptide with reference to GGG. The observed trends in the relative response factors were correlated with several analyte physicochemical parameters, chosen based on current understanding of ion release from charged droplets during the ESI process. These include analyte properties: nonpolar surface area; polar surface area; gas‐phase basicity; proton affinity; and Log D. Multivariate statistical analysis using multiple linear regression, decision tree, and support vector regression models were investigated to assess their potential for predicting ESI response based on the analyte properties. The support vector regression model was more versatile and produced the least predictive error following 12‐fold cross‐validation. The effect of variation in solution pH on the relative response factors is highlighted, as evidenced by the different predictive models obtained for peptide response at two pH values (pH = 6.0 and 9.0). The relationship between physicochemical parameters and associated ionization efficiencies for GXG tripeptides is discussed based on the equilibrium partitioning model. Copyright © 2009 John Wiley & Sons, Ltd.
Evolution of the BK polyomavirus: epidemiological, anthropological and clinical implications
Authors: Yogo Yoshiaki , Sugimoto Chie , Zhong Shan , Homma Yukio 
Published: June 2009

AbstractBK polyomavirus (BKV) is essentially ubiquitous in all human populations worldwide. Asymptomatic infection with this virus occurs during early childhood, leading to life‐long persistence in the kidney. BKV has four subtypes that can be identified using serological and genotyping methods. The evolutionary aspects of BKV have remained poorly understood due to the limited availability of BKV genomes, since urinary excretion of BKV DNA is detected primarily in immunocompromised individuals. However, we have found that BKV DNA sequences can often be amplified from non‐immunocompromised elderly individuals, using a highly sensitive polymerase chain reaction (PCR) with highly concentrated urinary DNA as the source of viral DNA. Using this approach, we have PCR‐amplified and sequenced a large number of partial and complete BKV genomes from various human populations worldwide and conducted a series of evolutionary studies using these sequences. We have shown that subtypes I and IV evolved into four and six subgroups, respectively, with each having a close relationship with a particular human population. In addition, we have provided evidence supporting the hypothesis that BKV strains with the archetypal transcriptional control region (TCR) circulate in the human population. In this review, we describe these findings and discuss their epidemiological, anthropological and clinical implications. Copyright © 2009 John Wiley & Sons, Ltd.
Feature extraction through local learning
Authors: Sun Yijun , Wu Dapeng 
Published: June 2009

AbstractRELIEF is considered one of the most successful algorithms for assessing the quality of features. It has been recently proved that RELIEF is an online learning algorithm that solves a convex optimization problem with a margin‐based objective function. Starting from this mathematical interpretation, we propose a novel feature extraction algorithm, referred to as local feature extraction (LFE), as a natural generalization of RELIEF. LFE collects discriminant information through local learning and can be solved as an eigenvalue decomposition problem with a closed‐form solution. A fast implementation of LFE is derived. Compared to principal component analysis, LFE also has a clear physical meaning and can be implemented easily with a comparable computational cost. Compared to other feature extraction algorithms, LFE has an explicit mechanism to remove irrelevant features. Experiments on synthetic and real‐world data are presented. The results demonstrate the effectiveness of the proposed algorithm. © 2009 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 2: 34‐47, 2009
Reflections on trends and challenges in internationalizing an Ontario community college
Authors: Grabove Valerie L. 
Published: June 2009

AbstractMarket‐driven in its efforts to increase revenue, internationalization at Niagara College Canada is in evidence primarily at the institutional level and marginalized at the academic level. However, a byproduct has been the gradual evolution of internationalized academic programs and curricula as academic staff external to the International Department become more sensitive to and educated in the notion of internationalization.
Education for world‐mindedness: Beyond superficial notions of internationalization
Authors: Van Gyn Geraldine , Schuerholz‐Lehr Sabine , Caws Catherine , Preece Allison 
Published: June 2009

AbstractAn internationalized curriculum requires that we extend our actions far beyond concerns of course content to include pedagogies that promote cross‐cultural understanding and facilitate the development of the knowledge, skills, and values that will enable students, both domestic and international, to successfully engage with others in an increasingly interconnected and interdependent world.
From the inside out: Learning to understand and appreciate multiple voices through telling identities
Authors: Turniansky Bobbie , Tuval Smadar , Mansur Ruth , Barak Judith , Gidron Ariela 
Published: June 2009

AbstractInternationalizing higher education is not simply a matter of adding international content. If one of the roles of higher education is to prepare students to survive and thrive in an uncertain, globalized world, we and our students have to develop a multicultural attitude that is both sensitive to, and appreciative of, cultural diversity.
Bridging the distance: Service learning in international perspective
Authors: Florman Jean C. , Just Craig , Naka Tomomi , Peterson Jim , Seaba Hazel H. 
Published: June 2009

AbstractPartnering with Rotary International and residents of Xicotepec, Mexico, the University of Iowa Colleges of Engineering, Pharmacy, and Liberal Arts & Sciences have created a cross‐disciplinary, international service‐learning course whose impact through the years will respond to student‐learning and community‐identified needs.
Effects of decabrominated diphenyl ether (PBDE 209) on voltage‐gated sodium channels in primary cultured rat hippocampal neurons
Authors: Xing Tai‐Ran , Yong Wu , Chen Liang , Tang Ming‐Liang , Wang Ming , Chen Ju‐Tao , Ruan Di‐Yun 
Published: June 2009

AbstractPolybrominated diphenyl ethers (PBDEs) are widely used as flame‐retardant additives. But the application of PBDEs has been challenged due to their toxicity, especially neurotoxicity. In this study, we investigated the effects of decabrominated diphenyl ether (PBDE 209), the major PBDEs product, on voltage‐gated sodium channels (VGSCs) in primary cultured rat hippocampal neurons. Employing the whole‐cell patch‐clamp technique, we found that PBDE 209 could irreversibly decrease voltage‐gated sodium channel currents (INa) in a very low dose and in a concentration‐dependent manner. We had systematically explored the effects of PBDE 209 onINaand found that PBDE 209 could shift the activation and inactivation ofINatoward hyperpolarizing direction, slow down the recovery from inactivation ofINa, and decrease the fraction of activated sodium channels. These results suggested that PBDE 209 could affect VGSCs, which may lead to changes in electrical activities and contribute to neurotoxicological damages. We also showed that ascorbic acid, as an antioxidant, was able to mitigate the inhibitory effects of PBDE 209 on VGSCs, which suggested that PBDE 209 might inhibitINathrough peroxidation. Our findings provide new insights into the mechanism for the neurological symptoms caused by PBDE 209. © 2009 Wiley Periodicals, Inc. Environ Toxicol 25: 400–408, 2010.