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Sample records for theoretical mechanistic study

  1. The Curtius Rearrangement of Cyclopropyl- and Cyclopropenoyl Azides. A Combined Theoretical and Experimental Mechanistic Study

    Science.gov (United States)

    Tarwade, Vinod; Dmitrenko, Olga; Bach, Robert D.; Fox, Joseph M.

    2009-01-01

    A combined experimental and theoretical study addresses the concertedness of the thermal Curtius rearrangement. The kinetics of the Curtius rearrangements of methyl 1-azidocarbonyl cycloprop-2-ene-1-carboxylate and methyl 1-azidocarbonyl cyclopropane-1-carboxylate were studied by 1H NMR spectroscopy, and there is close agreement between calculated and experimental enthalpies and entropies of activation. Density Functional Theory (DFT) calculations (B3LYP/6-311+G(d,p)) on these same acyl azides suggest gas phase barriers of 27.8 and 25.1 kcal/mol. By comparison, gas phase activation barriers for the rearrangement of acetyl, pivaloyl and phenyl azides are 27.6, 27.4 and 30.0 kcal/mol, respectively. The barrier for the concerted Curtius reaction of acetyl azide at the CCSD(T)/6-311+G(d,p) level exhibited a comparable activation energy of 26.3 kcal/mol. Intrinsic reaction coordinate (IRC) analyses suggest that all of the rearrangements occur by a concerted pathway with the concomitant loss of N2. The lower activation energy for the rearrangement of methyl 1-azidocarbonyl cycloprop-2-ene-1-carboxylate relative to methyl 1-azidocarbonyl cyclopropane-1-carboxylate was attributed to a weaker bond between the carbonyl carbon and the three-member ring in the former compound. Calculations on the rearrangement of cycloprop-2-ene-1-oyl azides do not support π–stabilization of the transition state by the cyclopropene double bond. A comparison of reaction pathways at the CBS-QB3 level for the Curtius rearrangement versus the loss of N2 to form a nitrene intermediate provides strong evidence that the concerted Curtius rearrangement is the dominant process. PMID:18826325

  2. Mechanistic studies on the formation of linear polyethylene chain catalyzed by palladium phosphine-sulfonate complexes: experiment and theoretical studies.

    Science.gov (United States)

    Noda, Shusuke; Nakamura, Akifumi; Kochi, Takuya; Chung, Lung Wa; Morokuma, Keiji; Nozaki, Kyoko

    2009-10-07

    Linear polyethylene propagation starting from Pd phosphine-sulfonate complexes, Pd(CH(3))(L)(Ar(2)PC(6)H(4)SO(3)) (L = 2,6-lutidine, Ar = o-MeOC(6)H(4) (2a) and L = pyridine, Ar = Ph (2b)), was studied both experimentally and theoretically. Experimentally, highly linear polyethylene was obtained with Pd(CH(3))(L)(Ar(2)PC(6)H(4)SO(3)) complexes 2a and 2b. Formation of a long alkyl-substituted palladium complex (3) was detected as a result of ethylene oligomerization on a palladium center starting from methylpalladium complex. Additionally, well-defined ethyl and propyl complexes (6(Et) and 6(Pr)) were synthesized as stable n-alkyl palladium complexes. In spite of the existence of beta-hydrogens, the beta-hydride elimination to give 1-alkenes was very slow or negligible in all cases. On the other hand, isomerization of 1-hexene in the presence of a methylpalladium/phosphine-sulfonate complex 2a indicated that this catalyst system actually undergoes beta-hydride elimination and reinsertion to release internal alkenes. On the theoretical side, the relative energies were calculated for intermediates and transition states for chain-growth, chain-walking, and chain-transfer on the basis of the starting model complex Pd(n-C(3)H(7))(pyridine)(o-Me(2)PC(6)H(4)SO(3)) (8). First, cis/trans isomerization process via the Berry's pseudorotation was proposed for the Pd/phosphine-sulfonate system. The second oxygen atom of sulfonate group is involved in the isomerization process as the associative ligand, which is one of the most unique natures of the sulfonate group. Chain propagation was suggested to take place from the less stable alkylPd(ethylene) complex 10' with the TS of 27.4/27.7 ((E+ZPC)/G) kcal/mol. Possible beta-hydride elimination was suggested to occur under low concentration of ethylene: the highest-energy transition state to override for beta-hydride elimination was either >37.4/25.3 kcal/mol (TS(9-12)) or 29.1/27.4 kcal/mol (TS(8'-9') to reach 12'). The ethylene

  3. Dynamic kinetic resolution of allylic sulfoxides by Rh-catalyzed hydrogenation: a combined theoretical and experimental mechanistic study.

    Science.gov (United States)

    Dornan, Peter K; Kou, Kevin G M; Houk, K N; Dong, Vy M

    2014-01-08

    A dynamic kinetic resolution (DKR) of allylic sulfoxides has been demonstrated by combining the Mislow [2,3]-sigmatropic rearrangement with catalytic asymmetric hydrogenation. The efficiency of our DKR was optimized by using low pressures of hydrogen gas to decrease the rate of hydrogenation relative to the rate of sigmatropic rearrangement. Kinetic studies reveal that the rhodium complex acts as a dual-role catalyst and accelerates the substrate racemization while catalyzing olefin hydrogenation. Scrambling experiments and theoretical modeling support a novel mode of sulfoxide racemization which occurs via a rhodium π-allyl intermediate in polar solvents. In nonpolar solvents, however, the substrate racemization is primarily uncatalyzed. Computational studies suggest that the sulfoxide binds to rhodium via O-coordination throughout the catalytic cycle for hydrogenation.

  4. Mechanistic studies of olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Grubbs, R.H.

    1979-03-01

    A review covers studies of the olefin metathesis mechanism which indicated that the reaction proceeds by a non-pairwise mechanism; detailed mechanistic studies on the homogeneously and heterogeneously catalyzed metathesis; and stereochemical investigations.

  5. Theoretical Mechanistic and Kinetic Studies on Homogeneous Gas-Phase Formation of Polychlorinated Naphthalene from 2-Chlorophenol as Forerunner

    Directory of Open Access Journals (Sweden)

    Fei Xu

    2015-10-01

    Full Text Available Polychlorinated naphthalenes (PCNs are dioxins-like compounds and are formed along with polychlorinated dibenzo-p-dioxins (PCDDs and polychlorinated dibenzofurans (PCDFs in thermal and combustion procedures. Chlorophenols (CPs are the most important forerunners of PCNs. A comprehensive comprehension of PCN formation procedure from CPs is a precondition for reducing the discharge of PCNs. Experiments on the formation of PCNs from CPs have been hindered by PCN toxicity and short of precise detection methods for active intermediate radicals. In this work, PCN formation mechanism in gas-phase condition from 2-chlorophenol (2-CP as forerunner was studied by quantum chemistry calculations. Numbers of energetically advantaged formation routes were proposed. The rate constants of key elementary steps were calculated over 600–1200 K using canonical variational transition-state theory (CVT with small curvature tunneling contribution (SCT method. This study illustrates formation of PCNs with one chlorine atom loss from 2-CP is preferred over that without chlorine atom loss. In comparison with formation of PCDFs from 2-CP, PCN products are less chlorinated and have lower formation potential.

  6. Mechanistic Studies on Chabazite-Type Methanol-to-Olefin Catalysts: Insights from Time-Resolved UV/Vis Microspectroscopy Combined with Theoretical Simulations

    NARCIS (Netherlands)

    Van Speybroeck, V.; Hemelsoet, K.L.J.; De Wispelaere, K.; Qian, Q.; Van der Mynsbrugge, J.; De Sterck, B.; Weckhuysen, B.M.; Waroquier, M.

    2013-01-01

    The formation and nature of active sites for methanol conversion over solid acid catalyst materials are studied by using a unique combined spectroscopic and theoretical approach. A working catalyst for the methanol-to-olefin conversion has a hybrid organic–inorganic nature in which a cocatalytic

  7. Theoretical Kinetic and Mechanistic Studies on the Reactions of CF3CBrCH2 (2-BTP with OH and H Radicals

    Directory of Open Access Journals (Sweden)

    Huiting Bian

    2017-12-01

    Full Text Available CF3CBrCH2 (2-bromo-3,3,3-trifluoropropene, 2-BTP is a potential replacement for CF3Br; however, it shows conflicted inhibition and enhancement behaviors under different combustion conditions. To better understand the combustion chemistry of 2-BTP, a theoretical study has been performed on its reactions with OH and H radicals. Potential energy surfaces were exhaustively explored by using B3LYP/aug-cc-pVTZ for geometry optimizations and CCSD(T/aug-cc-pVTZ for high level single point energy refinements. Detailed kinetics of the major pathways were predicted by using RRKM/master-equation methodology. The present predictions imply that the –C(Br=CH2 moiety of 2-BTP is most likely to be responsible for its fuel-like property. For 2-BTP + OH, the addition to the initial adduct (CF3CBrCH2OH is the dominant channel at low temperatures, while the substitution reaction (CF3COHCH2 + Br and H abstraction reaction (CF3CBrCH + H2O dominates at high temperatures and elevated pressures. For 2-BTP + H, the addition to the initial adduct (CF3CBrCH3 also dominates the overall kinetics at low temperatures, while Br abstraction reaction (CF3CCH2 + HBr and β-scission of the adduct forming CF3CHCH2 + Br dominates at high temperatures and elevated pressures. Compared to 2-BTP + OH, the 2-BTP + H reaction tends to have a larger effect on flame suppression, given the fact that it produces more inhibition species.

  8. A theoretical study on the mechanistic highlights behind the Brønsted-acid dependent mer-fac isomerization of homoleptic carbenic iridium complexes for PhOLEDs.

    Science.gov (United States)

    Setzer, Tobias; Lennartz, Christian; Dreuw, Andreas

    2017-06-06

    Recently, a successful Brønsted-acid mediated geometric isomerization of the meridional homoleptic carbenic iridium(iii) complexes tris-(N-phenyl,N-methyl-benzimidazol-2-yl)iridium(iii) (1) and tris-(N-phenyl,N-benzyl-benzimidazol-2-yl)iridium(iii) (2) into their facial form has been reported. In the present work the pronounced acid-dependency of this particular isomerization procedure is revisited and additional mechanistic pathways are taken into account. Moreover, the acid-induced material decomposition is addressed. All calculations are carried out using density functional theory (DFT) while the environmental effects in solution are accounted for by the COSMO-RS model. The simulated results clearly reveal the outstanding importance of the complex interplay between acid strength, coordinating power of the corresponding base and the steric influence of the ligand system in contrast to the plain calculation of minimum energy pathways for selected complexes. Eventually, general rules to enhance the material-specific reaction yields are provided.

  9. AASHTO mechanistic-empirical pavement design guide parametric study.

    Science.gov (United States)

    2012-03-01

    This study focuses on assessing the robustness of the AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG v 1.1) for rigid pavement : design projects in Wisconsin. The primary tasks conducted in this study included performing sensitivity analys...

  10. MECHANISTIC STUDIES OF IMPROVED FOAM EOR PROCESSES

    Energy Technology Data Exchange (ETDEWEB)

    William R. Rossen

    2003-03-31

    . We find that such behavior is consistent with earlier models of foam viscosity in tubes, and a modified model for the low-quality regime can account for this behavior. It is not yet clear why this new regime appears in some cases and not in others. Simple modeling suggests that the answer may have to do with the sensitivity of gas trapping to pressure gradient. Research on Task 3 continued to focus on foam generation at limited pressure gradient in sandpacks. We investigated the effects of permeability, surfactant concentration and liquid injection rates on foam generation. In addition, a careful review of published studies showed that repeated snap-off is not a plausible mechanism of foam generation in homogeneous porous media beyond the stage of initial drainage from a fully liquid-saturated state. Snap-off has been the focus of much research on foam generation and is incorporated into most mechanistic foam simulators. This finding should force a reconsideration of its role in foam generation and properties in porous media.

  11. Cyclic voltammetry and reduction mechanistic studies of ...

    African Journals Online (AJOL)

    styrylpyrylium perchlorates have been evaluated using cyclic voltammetry, in comparison to their non-methylated derivatives values. The reduction peak of all studied compounds remained chemically irreversible. The presence of the ...

  12. Mechanistic insight into degradation of endocrine disrupting chemical by hydroxyl radical: An experimental and theoretical approach.

    Science.gov (United States)

    Xiao, Ruiyang; Gao, Lingwei; Wei, Zongsu; Spinney, Richard; Luo, Shuang; Wang, Donghong; Dionysiou, Dionysios D; Tang, Chong-Jian; Yang, Weichun

    2017-12-01

    Advanced oxidation processes (AOPs) based on formation of free radicals at ambient temperature and pressure are effective for treating endocrine disrupting chemicals (EDCs) in waters. In this study, we systematically investigated the degradation kinetics of bisphenol A (BPA), a representative EDC by hydroxyl radical (OH) with a combination of experimental and theoretical approaches. The second-order rate constant (k) of BPA with OH was experimentally determined to be 7.2 ± 0.34 × 10 9  M -1  s -1 at pH 7.55. We also calculated the thermodynamic and kinetic behaviors for the bimolecular reactions by density functional theory (DFT) using the M05-2X method with 6-311++G** basis set and solvation model based on density (SMD). The results revealed that H-abstraction on the phenol group is the most favorable pathway for OH. The theoretical k value corrected by the Collins-Kimball approach was determined to be 1.03 × 10 10  M -1  s -1 , which is in reasonable agreement with the experimental observation. These results are of fundamental and practical importance in understanding the chemical interactions between OH and BPA, and aid further AOPs design in treating EDCs during wastewater treatment processes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Mechanistic insights into the selective cyclization of indolines with alkynes and alkenes to produce six- and seven-membered 1,7-fused indolines via Rh(iii) catalysis: a theoretical study.

    Science.gov (United States)

    Han, Lingli; Zhang, Xinyu; Wang, Xingdong; Zhao, Fengyue; Liu, Shaojing; Liu, Tao

    2017-05-10

    The coupling reaction mechanisms of the Rh(iii)-catalyzed redox-neutral C7-selective aryl C-H functionalization of indolines with alkynes and alkenes have been theoretically investigated with the aid of the density functional theory (DFT) calculations. Our calculation results indicate that the active catalyst in this system is the cationic species [Cp*Rh(OAc)] + (2cat) instead of the neutral species Cp*Rh(OAc) 2 (1cat). The origin of forming different products associated with using different coupling partners was also rationalized in detail. For the coupling reaction of N-methoxycarbamoyl-protected indoline (1a) with alkyl alkyne (4a), the electronic effect plays a dominant role and causes the six-membered ring product to be the main product. For the coupling reaction of 1a with aryl alkyne (2a), through the replacement of alkyl alkyne with aryl alkyne, the steric effect serves as a crucial factor, compared with the electronic effect, and leads to the main seven-membered ring product. For the coupling reaction of 1a with acrylate (6a), the chemoselectivity is dictated by the steric effect and electronic effect.

  14. Combined experimental and theoretical mechanistic investigation of the Barbier allylation in aqueous media.

    Science.gov (United States)

    Dam, Johan Hygum; Fristrup, Peter; Madsen, Robert

    2008-04-18

    The Barbier allylation of a series of para-substituted benzaldehydes with allylbromide in the presence of Zn, In, Sn, Sb, Bi, and Mg was investigated using competition experiments. In all cases, the slope of the Hammett plots indicated a build-up of negative charge in the selectivity-determining step. For Zn, In, Sn, Sb, and Bi, an inverse secondary kinetic isotope effect was found (kH/kD = 0.75-0.95), which was compatible with the formation of a discrete organometallic species prior to allylation via a closed six-membered transition state. With Mg, a significantly larger build-up of negative charge along with a small positive secondary kinetic isotope effect (kH/kD = 1.06) indicated that the selectivity-determining step was the generation of the radical anion of benzaldehyde. The reaction through a six-membered transition state was modeled using density functional theory with the effect of solvent described by a polarized continuum model. The calculated secondary deuterium isotope effects based on this mechanism were found to be in good agreement with experimental values, thus adding further support to this mechanistic scenario.

  15. Experimental and Theoretical Mechanistic Investigation of the Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

    DEFF Research Database (Denmark)

    Olsen, Esben Paul Krogh; Singh, Thishana; Harris, Pernille

    2015-01-01

    The mechanism for the iridium-BINAP catalyzed dehydrogenative decarbonylation of primary alcohols with the liberation of molecular hydrogen and carbon monoxide was studied experimentally and computationally. The reaction takes place by tandem catalysis through two catalytic cycles involving...... cycles. One carbon monoxide ligand was shown to remain coordinated to iridium throughout the reaction, and release of carbon monoxide was suggested to occur from a dicarbonyl complex. IrH2Cl(CO)(rac-BINAP) was also synthesized and detected in the dehydrogenation of benzyl alcohol. In the same experiment......, IrHCl2(CO)(rac-BINAP) was detected from the release of HCl in the dehydrogenation and subsequent reaction with IrCl(CO)(rac-BINAP). This indicated a substitution of chloride with the alcohol to form a square planar iridium alkoxo complex that could undergo a beta-hydride elimination. A KIE of 1...

  16. Theoretical Advanced Study Institute: 2014

    Energy Technology Data Exchange (ETDEWEB)

    DeGrand, Thomas [Univ. of Colorado, Boulder, CO (United States)

    2016-08-17

    The Theoretical Advanced Study Institute (TASI) was held at the University of Colorado, Boulder, during June 2-27, 2014. The topic was "Journeys through the Precision Frontier: Amplitudes for Colliders." The organizers were Professors Lance Dixon (SLAC) and Frank Petriello (Northwestern and Argonne). There were fifty-one students. Nineteen lecturers gave sixty seventy-five minute lectures. A Proceedings was published. This TASI was unique for its large emphasis on methods for calculating amplitudes. This was embedded in a program describing recent theoretical and phenomenological developments in particle physics. Topics included introductions to the Standard Model, to QCD (both in a collider context and on the lattice), effective field theories, Higgs physics, neutrino interactions, an introduction to experimental techniques, and cosmology.

  17. Bioavailability and Pharmacokinetics of Genistein: Mechanistic Studies on its ADME

    Science.gov (United States)

    Yang, Zhen; Kulkarni, Kaustubh; Zhu, Wei; Hu, Ming

    2014-01-01

    Genistein, one of the most active natural flavonoids, exerts various biological effects including chemoprevention, antioxidation, antiproliferation and anticancer. More than 30 clinical trials of genistein with various disease indications have been conducted to evaluate its clinical efficacy. Based on many animals and human pharmacokinetic studies, it is well known that the most challenge issue for developing genistein as a chemoprevention agent is the low oral bioavailability, which may be the major reason relating to its ambiguous therapeutic effects and large interindividual variations in clinical trials. In order to better correlate pharmacokinetic to pharmacodynamics results in animals and clinical studies, an in-depth understanding of pharmacokinetic behavior of genistein and its ADME properties are needed. Numerous in vitro/in vivo ADME studies had been conducted to reveal the main factors contributing to the low oral bioavailability of genistein. Therefore, this review focuses on summarizing the most recent progress on mechanistic studies of genistein ADME and provides a systemic view of these processes to explain genistein pharmacokinetic behaviors in vivo. The better understanding of genistein ADME property may lead to development of proper strategy to improve genistein oral bioavailability via mechanism-based approaches. PMID:22583407

  18. A mechanistic study of Protein A chromatography resin lifetime.

    Science.gov (United States)

    Jiang, Canping; Liu, Jing; Rubacha, Michael; Shukla, Abhinav A

    2009-07-31

    A mechanistic study into Protein A chromatographic resin lifetime limitations is presented. Binding and mass transport properties of two widely used agarose-based Protein A resins were studied to distinguish between the roles of resin fouling due to product/impurity build-up and ligand degradation as contributory factors towards the decline in binding capacity with use. Cycling studies were conducted with and without product loading on the columns to separate out the influence of resin fouling. Ligand degradation under the mildly alkaline conditions used for column regeneration was determined to be the primary cause for Protein A resin capacity decline with usage. The use of lower concentrations of caustic and the use of stabilizing excipients to protect the Protein A ligand during cleaning and sanitization were found to be useful techniques in maintaining column performance. The results presented in this paper provide a clearer understanding of the causative factors that limit Protein A chromatographic resin lifetime. It is anticipated that these findings will assist in the development of more robust and economical downstream manufacturing processes for monoclonal antibody and Fc fusion protein purification.

  19. Theoretical studies of combustion dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, J.M. [Emory Univ., Atlanta, GA (United States)

    1993-12-01

    The basic objectives of this research program are to develop and apply theoretical techniques to fundamental dynamical processes of importance in gas-phase combustion. There are two major areas currently supported by this grant. One is reactive scattering of diatom-diatom systems, and the other is the dynamics of complex formation and decay based on L{sup 2} methods. In all of these studies, the authors focus on systems that are of interest experimentally, and for which potential energy surfaces based, at least in part, on ab initio calculations are available.

  20. Mechanistic studies of ethylene biosynthesis in higher plants

    International Nuclear Information System (INIS)

    McGeehan, G.M.

    1986-01-01

    Ethylene is a plant hormone that elicits a wide variety of responses in plant tissue. Among these responses are the hastening of abscission, ripening and senescence. In 1979 it was discovered that 1-amino-1-cyclopropane carboxylic acid is the immediate biosynthetic precursor to ethylene. Given the obvious economic significance of ethylene production the authors concentrated their studies on the conversion of ACC to ethylene. They delved into mechanistic aspects of ACC oxidation and they studied potential inhibitors of ethylene forming enzyme (EFE). They synthesized various analogs of ACC and found that EFE shows good stereodiscrimination among alkyl substituted ACC analogs with the 1R, 2S stereoisomer being processed nine times faster than the 1S, 2R isomer in the MeACC series. They also synthesized 2-cyclopropyl ACC which is a good competitive inhibitor of EFE. This compound also causes time dependent loss of EFE activity leading us to believe it is an irreversible inhibitor of ethylene formation. The synthesis of these analogs has also allowed them to develop a spectroscopic technique to assign the relative stereochemistry of alkyl groups. 13 C NMR allows them to assign the alkyl stereochemistry based upon gamma-shielding effects on the carbonyl resonance. Lastly, they measured kinetic isotope effects on the oxidation of ACC in vivo and in vitro and found that ACC is oxidized by a rate-determining 1-electron removal from nitrogen in close accord with mechanisms for the oxidation of other alkyl amines

  1. Neutron structure and mechanistic studies of diisopropyl fluorophosphatase (DFPase)

    International Nuclear Information System (INIS)

    Chen, Julian C.-H.; Mustyakimov, Marat; Schoenborn, Benno P.; Langan, Paul; Blum, Marc-Michael

    2010-01-01

    The structure and mechanism of diisopropyl fluorophosphatase (DFPase) have been studied using a variety of methods, including isotopic labelling, X-ray crystallography and neutron crystallography. The neutron structure of DFPase, mechanistic studies and subsequent rational design efforts are described. Diisopropyl fluorophosphatase (DFPase) is a calcium-dependent phosphotriesterase that acts on a variety of highly toxic organophosphorus compounds that act as inhibitors of acetylcholinesterase. The mechanism of DFPase has been probed using a variety of methods, including isotopic labelling, which demonstrated the presence of a phosphoenzyme intermediate in the reaction mechanism. In order to further elucidate the mechanism of DFPase and to ascertain the protonation states of the residues and solvent molecules in the active site, the neutron structure of DFPase was solved at 2.2 Å resolution. The proposed nucleophile Asp229 is deprotonated, while the active-site solvent molecule W33 was identified as water and not hydroxide. These data support a mechanism involving direct nucleophilic attack by Asp229 on the substrate and rule out a mechanism involving metal-assisted water activation. These data also allowed for the re-engineering of DFPase through rational design to bind and productively orient the more toxic S P stereoisomers of the nerve agents sarin and cyclosarin, creating a modified enzyme with enhanced overall activity and significantly increased detoxification properties

  2. THEORETICAL ASPECTS OF FILMMUSIC STUDY

    Directory of Open Access Journals (Sweden)

    Egorova Tatiana K.

    2014-04-01

    Full Text Available In this article, author analyzes the theoretical aspects of the film music study taking into account with modern realities in the development of world film-process and attempts to its scientific understanding. Need for innovation in this area is long overdue, because the existing on this topic nonfiction no longer meets the new aesthetic and art-practical achievements and innovations in the film music development at the XXI century. Related to the phenomenon of music in screen arts a number of new terms and concepts require a certain adjustment as well. Their range of action is not yet fully defined. Author of the article offered her version of their content-semantic interpretation (largely experimental designed to promote new research methods for the film music study.

  3. Antioxidative activity of caffeic acid: Mechanistic DFT study

    OpenAIRE

    Redžepović, Izudin; Marković, Svetlana; Tošović, Jelena

    2017-01-01

    This paper reports the results of comprehensive mechanistic investigations of the hydrogen atom transfer (HAT), radical adduct formation (RAF), single electron transfer – proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms of caffeic acid (CA). The goals of the work were achieved by simulating the reactions of CA with hydroxyl radical in benzene and water solutions. It was found that SET-PT is not a favourable antioxidative mechanism of CA. On the other h...

  4. Mechanistic study of aerosol dry deposition on vegetated canopies

    International Nuclear Information System (INIS)

    Petroff, A.

    2005-04-01

    The dry deposition of aerosols onto vegetated canopies is modelled through a mechanistic approach. The interaction between aerosols and vegetation is first formulated by using a set of parameters, which are defined at the local scale of one surface. The overall deposition is then deduced at the canopy scale through an up-scaling procedure based on the statistic distribution parameters. This model takes into account the canopy structural and morphological properties, and the main characteristics of the turbulent flow. Deposition mechanisms considered are Brownian diffusion, interception, initial and turbulent impaction, initially with coniferous branches and then with entire canopies of different roughness, such as grass, crop field and forest. (author)

  5. Mechanistic Studies at the Interface Between Organometallic Chemistry and Homogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Casey, Charles P

    2012-11-14

    the aldehyde carbon and of a proton from the CpOH unit to the aldehyde oxygen and support reduction of the aldehyde without its prior coordination to ruthenium. Another important step in the catalysis is the regeneration of 1 from reaction of H2 with the stable diruthenium bridging hydride complex 2. Studies of the microscopic reverse of this process (hydrogen evolution from 1 which occurs at 80°C) in the presence of alcohol (the product of aldehyde hydrogenation) have shown that a dihydrogen complex is formed reversibly at a rate much faster than hydrogen evolution. Kinetic and theoretical studies in collaboration with Professor Qiang Cui of Wisconsin indicated an important role for alcohol in mediating transfer of hydrogen to ruthenium. One key to developing more active catalysts was to destabilize the bridging hydride intermediate 2 to prevent its formation or to speed its conversion to a reactive monohydride 1 by reaction with H2. We found several successful ways to destabilize the bridging hydride and to obtain more active catalysts. Most recently, we discovered related iron catalysts for hydrogenation that do not form dimers; the cost advantage of iron catalysts is spectacular. Iron Catalysts. In an exciting development, we found that a related iron complex is also a very active ketone hydrogenation catalyst. This hydrogenation catalyst shows high chemoselectivity for aldehydes, ketones, and imines and isolated C=C, CºC, C-X, -NO2, epoxides, and ester functions are unaffected by the hydrogenation conditions. Mechanistic studies have established a reversible hydrogen transfer step followed by rapid dihydrogen activation. The same iron complex also catalyzes transfer hydrogenation of ketones.

  6. Biomarker Discovery and Mechanistic Studies of Prostate Cancer using Targeted Proteomic Approaches

    Science.gov (United States)

    2012-07-01

    density: a means of distinguishing benign prostatic hypertrophy and prostate cancer. J Urol 147: 815-816, 1992. 11. Catalona WJ, Richie JP, deKernion...Mechanistic Studies of Prostate Cancer using Targeted Proteomic Approaches PRINCIPAL INVESTIGATOR: Haining Zhu, Ph.D...Mechanistic Studies of Prostate Cancer using Targeted Proteomic Approaches 5b. GRANT NUMBER W81XWH-08-1-0430 5c. PROGRAM ELEMENT NUMBER 6

  7. Antioxidative activity of caffeic acid: Mechanistic DFT study

    Directory of Open Access Journals (Sweden)

    Redžepović Izudin

    2017-01-01

    Full Text Available This paper reports the results of comprehensive mechanistic investigations of the hydrogen atom transfer (HAT, radical adduct formation (RAF, single electron transfer – proton transfer (SET-PT, and sequential proton loss electron transfer (SPLET mechanisms of caffeic acid (CA. The goals of the work were achieved by simulating the reactions of CA with hydroxyl radical in benzene and water solutions. It was found that SET-PT is not a favourable antioxidative mechanism of CA. On the other hand, HAT and RAF are competitive, because HAT pathways yield thermodynamically more stable radical products, and RAF pathways require smaller activation barriers. In polar basic environment SPLET is a probable antioxidative mechanism of CA, with exceptionally large rate.

  8. Study of zircaloy corrosion to develop mechanistic understanding

    International Nuclear Information System (INIS)

    Ortner, S.; Swan, H.; Laferrere, A.; English, C.; Hyde, J.; Styman, P.; Jurkschat, K.; Hulme, H.; Pantelli, A.; Gass, M.; Allen, V.; Frankel, P.

    2015-01-01

    Predictions for the corrosion behaviour of Zircaloy cladding are based on empirical models. This results in significant uncertainties for forecasts beyond existing data e.g. for high burn-up, or when there has been a change in operating conditions. To allow for a more accurate prediction of corrosion behaviour a better understanding of the mechanisms involved is required. A program has been initiated with the aim of developing a detailed mechanistic understanding of out-of-pile Zircaloy corrosion behaviour. This paper reports the results of isothermal exposures of Zircaloy-4 to PWR water at 350 Celsius degrees. A variety of analytical techniques have been employed to analyse the corroded specimens, including scanning and transmission electron microscopy, atom probe tomography, micro-beam synchrotron X-ray diffraction and electron energy loss spectroscopy. When the results of these techniques are compared, it becomes evident that the periodic transition from slow to fast oxidation rates results from the accumulation of stress relief processes in the metal (particularly plastic deformation, but also oxygen and hydrogen dissolution); at the metal-oxide interface (decomposition of the flat interface into undulations); and in the oxide (cracking). These reduce the in-plane compressive stresses near the metal-oxide interface but ultimately balance them with in-plane tensile stresses which encourage through-thickness cracking, and the percolation of the environment to the metal-oxide interface. This is noticed only if allowance is made for out-of-plane stresses in the thin oxide. (authors)

  9. Mechanistic Studies in Friction and Wear of Bulk Materials

    Science.gov (United States)

    Sawyer, W. Gregory; Argibay, Nicolas; Burris, David L.; Krick, Brandon A.

    2014-07-01

    From the context of a contemporary understanding of the phenomenological origins of friction and wear of materials, we review insightful contributions from recent experimental investigations of three classes of materials that exhibit uniquely contrasting tribological behaviors: metals, polymers, and ionic solids. We focus on the past decade of research by the community to better understand the correlations between environment parameters, materials properties, and tribological behavior in systems of increasingly greater complexity utilizing novel synthesis and in situ experimental techniques. In addition to such review, and a half-century after seminal publications on the subject, we present recently acquired evidence linking anisotropy in friction response with anisotropy in wear behavior of crystalline ionic solids as a function of crystallographic orientation. Although the tribological behaviors of metals, polymers, and ionic solids differ widely, it is increasingly more evident that the mechanistic origins (such as fatigue, corrosion, abrasion, and adhesion) are essentially the same. However, we hope to present a clear and compelling argument favoring the prominent and irreplaceable role of in situ experimental techniques as a bridge between fundamental atomistic and molecular processes and emergent behaviors governing tribological contacts.

  10. Theoretical studies in nuclear physics

    International Nuclear Information System (INIS)

    Landau, R.H.; Madsen, V.A.

    1991-01-01

    This report discusses research in nuclear theory in the following areas: Isospin effects and charge exchange; inelastic and charge exchange scattering; momentum space proton scattering; pion scattering from nuclei; and antiproton studies. 14 refs

  11. Theoretical studies of unconventional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Groensleth, Martin Sigurd

    2008-07-01

    This thesis presents four research papers. In the first three papers we have derived analytical results for the transport properties in unconventional superconductors and ferromagnetic systems with multiple broken symmetries. In Paper I and parts of Paper II we have studied tunneling transport between two non-unitary ferromagnetic spin-triplet superconductors, and found a novel interplay between ferromagnetism and superconductivity manifested in the Josephson effect as a spin- and charge-current in the absence of an applied voltage across the junction. The critical amplitudes of these currents can be adjusted by the relative magnetization direction on each side of the junction. Furthermore, in Paper II, we have found a way of controlling a spin-current between two ferromagnets with spin-orbit coupling. Paper III considers a junction consisting of a ferromagnet and a non-unitary ferromagnetic superconductor, and we show that the conductance spectra contains detailed information about the superconducting gaps and pairing symmetry of the Cooper-pairs. In the last paper we present a Monte Carlo study of an effective Hamiltonian describing orbital currents in the CuO2 layers of high-temperature superconductive cuprates. The model features two intrinsically anisotropic Ising models, coupled through an anisotropic next-nearest neighbor interaction, and an Ashkin-Teller nearest neighbor fourth order coupling. We have studied the specific heat anomaly, as well as the anomaly in the staggered magnetization associated with the orbital currents and its susceptibility. We have found that in a limited parameter regime, the specific heat anomaly is substantially suppressed, while the susceptibility has a non-analytical peak across the order-disorder transition. The model is therefore a candidate for describing the breakup of hidden order when crossing the pseudo-gap line on the under-doped side in the phase diagram of high-temperature superconductors. (Author) 64 refs., figs

  12. A preliminary study of mechanistic approach in pavement design to accommodate climate change effects

    Science.gov (United States)

    Harnaeni, S. R.; Pramesti, F. P.; Budiarto, A.; Setyawan, A.

    2018-03-01

    Road damage is caused by some factors, including climate changes, overload, and inappropriate procedure for material and development process. Meanwhile, climate change is a phenomenon which cannot be avoided. The effects observed include air temperature rise, sea level rise, rainfall changes, and the intensity of extreme weather phenomena. Previous studies had shown the impacts of climate changes on road damage. Therefore, several measures to anticipate the damage should be considered during the planning and construction in order to reduce the cost of road maintenance. There are three approaches generally applied in the design of flexible pavement thickness, namely mechanistic approach, mechanistic-empirical (ME) approach and empirical approach. The advantages of applying mechanistic approach or mechanistic-empirical (ME) approaches are its efficiency and reliability in the design of flexible pavement thickness as well as its capacity to accommodate climate changes in compared to empirical approach. However, generally, the design of flexible pavement thickness in Indonesia still applies empirical approach. This preliminary study aimed to emphasize the importance of the shifting towards a mechanistic approach in the design of flexible pavement thickness.

  13. Reconstructing Middle Eocene Climate and Atmospheric Carbon Dioxide Concentration: Application of a mechanistic theoretical approach to fossil plants from the Messel Pit (Germany)

    Science.gov (United States)

    Grein, M.; Roth-Nebelsick, A.; Wilde, V.; Konrad, W.; Utescher, T.

    2009-12-01

    It is assumed that changes in atmospheric CO2 concentrations (from now on expressed as Ca) strongly influenced the development of global temperatures during parts of the Cenozoic. Thus, detailed knowledge of ancient Ca and its variations is of utmost importance for exploring the coupling of atmospheric CO2 and global climate change. Numerous techniques (such as carbon and boron isotopes) were applied in order to obtain Ca, with varying and sometimes even conflicting results. Stomatal density (number of stomata per leaf area) represents another promising proxy for the calculation of ancient Ca since many plants reduce the number of stomata (pores on the leaf surface used for gas exchange) under increasing Ca. As a reason it is assumed that plants try to adjust stomatal conductance in order to optimize their gas exchange (which means maximal assimilation at minimal transpiration). The common technique for calculating Ca from fossil stomatal frequency is to create empirical transfer functions of living plants derived from herbar material or greenhouse experiments. In the presented project, Ca of the Middle Eocene is calculated by applying a different approach which utilizes a mechanistic-theoretical calibration. It couples the processes of a) C3-photosynthesis, b) diffusion and c) transpiration with palaeoclimatic and leaf-anatomical data. The model also includes an optimisation principle supported by ecophysiological data. According to this optimisation principle, plants adjust their stomatal conductance in such a way that photosynthesis rates are constrained by optimal water use (transpiration). This model was applied in the present study to fossil plants from the Messel Pit near Darmstadt (Germany). In order to reconstruct Ca by using fossil plant taxa from Messel, numerous parameters which represent model input have to be estimated from measurements of living representatives. Furthermore, since climate parameters are also required by the model, quantitative

  14. Atomization of bismuthane in a dielectric barrier discharge: A mechanistic study

    Czech Academy of Sciences Publication Activity Database

    Kratzer, Jan; Zelina, Ondřej; Svoboda, Milan; Sturgeon, R. E.; Mester, Z.; Dědina, Jiří

    2016-01-01

    Roč. 88, č. 3 (2016), s. 1804-1811 ISSN 0003-2700 R&D Projects: GA ČR GA14-23532S Grant - others:GA AV ČR(CZ) M200311202 Institutional support: RVO:68081715 Keywords : dielectric barrier discharge * hydride generation * mechanistic study Subject RIV: CB - Analytical Chemistry , Separation Impact factor: 6.320, year: 2016

  15. Atomization of bismuthane in a dielectric barrier discharge: A mechanistic study

    Czech Academy of Sciences Publication Activity Database

    Kratzer, Jan; Zelina, Ondřej; Svoboda, Milan; Sturgeon, R. E.; Mester, Z.; Dědina, Jiří

    2016-01-01

    Roč. 88, č. 3 (2016), s. 1804-1811 ISSN 0003-2700 R&D Projects: GA ČR GA14-23532S Grant - others:GA AV ČR(CZ) M200311202 Institutional support: RVO:68081715 Keywords : dielectric barrier discharge * hydride generation * mechanistic study Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 6.320, year: 2016

  16. A MECHANISTIC STUDY OF RHODIUM TRI(ORTHO-TERT-BUTYLPHENYL)PHOSPHITE COMPLEXES AS HYDROFORMYLATION CATALYSTS

    NARCIS (Netherlands)

    JONGSMA, T; CHALLA, G; VANLEEUWEN, PWNM

    1991-01-01

    A mechanistic study of the hydroformylation cycle with a rhodium tri(o-t-butylphenyl)phosphite complex as catalyst is presented. Spectroscopic experiments prove that under hydroformylation conditions this complex is coordinated by only one phosphite. The complex has a high activity in the

  17. Towards an integrated experimental-theoretical approach for assessing the mechanistic basis of hair and feather morphogenesis.

    Science.gov (United States)

    Painter, K J; Hunt, G S; Wells, K L; Johansson, J A; Headon, D J

    2012-08-06

    In his seminal 1952 paper, 'The Chemical Basis of Morphogenesis', Alan Turing lays down a milestone in the application of theoretical approaches to understand complex biological processes. His deceptively simple demonstration that a system of reacting and diffusing chemicals could, under certain conditions, generate spatial patterning out of homogeneity provided an elegant solution to the problem of how one of nature's most intricate events occurs: the emergence of structure and form in the developing embryo. The molecular revolution that has taken place during the six decades following this landmark publication has now placed this generation of theoreticians and biologists in an excellent position to rigorously test the theory and, encouragingly, a number of systems have emerged that appear to conform to some of Turing's fundamental ideas. In this paper, we describe the history and more recent integration between experiment and theory in one of the key models for understanding pattern formation: the emergence of feathers and hair in the skins of birds and mammals.

  18. Mechanistic studies of neoplastic cell transformation by ionizing radiation

    International Nuclear Information System (INIS)

    Yang, T.C.; Craise, L.M.; Tobias, C.A.

    1982-01-01

    As part of the Biology and Medicine heavy-ion radiation program, we are systematically investigating the potential carcinogenic and mutagenic effects of high- and low-linear energy transfer (LET) radiation at the cellular level. From these studies, we anticipate additional insight into the molecular and cellular mechanisms of radiation carcinogenesis. Such results should provide quantitative information useful for assessing the undesirable biological effects of cosmic rays in space. Some of our recent experimental results are presented here

  19. Theoretical studies of chemical reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Schatz, G.C. [Argonne National Laboratory, IL (United States)

    1993-12-01

    This collaborative program with the Theoretical Chemistry Group at Argonne involves theoretical studies of gas phase chemical reactions and related energy transfer and photodissociation processes. Many of the reactions studied are of direct relevance to combustion; others are selected they provide important examples of special dynamical processes, or are of relevance to experimental measurements. Both classical trajectory and quantum reactive scattering methods are used for these studies, and the types of information determined range from thermal rate constants to state to state differential cross sections.

  20. Tissue-Engineered Heart Valves: A Call for Mechanistic Studies.

    Science.gov (United States)

    Blum, Kevin M; Drews, Joseph D; Breuer, Christopher K

    2018-02-13

    Heart valve disease carries a substantial risk of morbidity and mortality. Outcomes are significantly improved by valve replacement, but currently available mechanical and biological replacement valves are associated with complications of their own. Mechanical valves have a high rate of thromboembolism and require lifelong anticoagulation. Biological prosthetic valves have a much shorter lifespan, and they are prone to tearing and degradation. Both types of valves lack the capacity for growth, making them particularly problematic in pediatric patients. Tissue engineering has the potential to overcome these challenges by creating a neovalve composed of native tissue that is capable of growth and remodeling. The first tissue-engineered heart valve (TEHV) was created more than 20 years ago in an ovine model, and the technology has been advanced to clinical trials in the intervening decades. Some TEHVs have had clinical success, whereas others have failed, with structural degeneration resulting in patient deaths. The etiologies of these complications are poorly understood because much of the research in this field has been performed in large animals and humans, and, therefore, there are few studies of the mechanisms of neotissue formation. This review examines the need for a TEHV to treat pediatric patients with valve disease, the history of TEHVs, and a future that would benefit from extension of the reverse translational trend in this field to include small animal studies.

  1. Silicene catalyzed reduction of nitrobenzene to aniline: A mechanistic study

    Science.gov (United States)

    Morrissey, Christopher; He, Haiying

    2018-03-01

    The reduction of nitrobenzene to aniline has broad applications in chemical and pharmaceutical industries. The high reaction temperatures and pressures and unavoidable hazardous chemicals of current metal catalysts call for more environmentally friendly non-metal catalysts. In this study, the plausibility of silicene as a potential catalyst for nitrobenzene reduction is investigated with a focus on the distinct reaction mechanism based on the density functional theory. The direct reaction pathway was shown to be distinctly different from the Haber mechanism following PhNO2∗ → PhNO∗ → PhNHO∗ → PhNH2O∗ → PhNH2∗. The hydroxyl groups remain bound to silicene after aniline is formed and acquire a high activation barrier to remove.

  2. A mechanistic study of ciprofloxacin removal by kaolinite.

    Science.gov (United States)

    Li, Zhaohui; Hong, Hanlie; Liao, Libing; Ackley, Caren J; Schulz, Laura A; MacDonald, Roberta A; Mihelich, Amanda L; Emard, Shannon M

    2011-11-01

    As one of the most important soil components, kaolinite plays a vital role in transport and retention of ionizable contaminants in soils of warm and wet climate. Ciprofloxacin (Cip) is a second generation fluoroquinolone (FQ) antibiotic of high use. It has high aqueous solubility under high and low pH conditions and higher stability in soil system. In this study, the interactions between Cip and kaolinite in aqueous solution were investigated by batch experiments, XRD and FTIR analyses. Quantitative correlation between the exchangeable cations desorbed and Cip adsorbed confirmed experimentally that cation exchange was the dominant mechanism of Cip adsorption on kaolinite. Fitting of experimental data to the cation exchange model resulted in a selectivity coefficient of 27, suggesting a strong affinity of Cip on negatively charged kaolinite surfaces. At the adsorption maximum 190-200 Å(2) was available per Cip molecule, much larger than the Cip molecule area, confirming charge-limited instead of surface-limited Cip adsorption. The invariable d-spacing after uptake of different amounts of Cip suggested that the adsorption of Cip was on the external surfaces of kaolinite. As solution pH increased beyond 8, the amount of Cip adsorption decreased significantly and reached close to zero at pH 11. The high adsorption rate constant due to surface adsorption instead of intercalation and the wide distribution of kaolinite in different soils suggest that the fate and transport of Cip may be governed by the transport of colloidal sized clays. Copyright © 2011 Elsevier B.V. All rights reserved.

  3. Mechanistic study of inhibition of levofloxacin absorption by aluminum hydroxide.

    Science.gov (United States)

    Tanaka, M; Kurata, T; Fujisawa, C; Ohshima, Y; Aoki, H; Okazaki, O; Hakusui, H

    1993-01-01

    The mechanisms of reduction in absorption of levofloxacin (LVFX) by coadministration of aluminum hydroxide were studied. The partition coefficient of LVFX (0.1 mM) between chloroform and phosphate buffer (pH 5.0) was reduced by 60 to 70% with the addition of metal ions such as Cu2+, Al3+, and Fe2+ (0.8 mM), which indicated the formation of LVFX-metal ion chelates. However, there was no significant difference in absorption from rat intestine between the synthetic LVFX-Al3+ (1:1) chelate (6.75 mM) and LVFX (6.75 mM) in an in situ recirculation experiment. On the other hand, Al(NO3)3 (1.5 mM) significantly inhibited the absorption of LVFX (1.5 mM) by 20% of the control in the in situ ligated loop experiment, in which partial precipitation of aluminum hydroxide was observed in the dosing solution. Data for adsorption of LVFX and ofloxacin (OFLX) from aqueous solution by aluminum hydroxide were shown to fit Langmuir plots, and the adsorptive capacities (rmax) and the K values were 7.0 mg/g and 1.77 x 10(4) M-1 for LVFX and 7.4 mg/g and 1.42 x 10(4) M-1 for OFLX, respectively. The rate of adsorption of several quinolones (50 microM) onto aluminum hydroxide (2.5 mg/ml) followed the order norfloxacin (NFLX) (72.0%) > enoxacin (ENX) (61.0%) > OFLX (47.2%) approximately LVFX (48.1%). The elution rate of adsorbed quinolones with water followed the rank order LVFX (17.9%) approximately OFLX (20.9%) approximately ENX (18.3%) > NFLX (11.9%). These results strongly suggest that adsorption of quinolones by aluminum hydroxide reprecipitated in the small intestine would play an important role in the reduced bioavailability of quinolones after coadministration with aluminum-containing antacids. Images PMID:8257141

  4. Surfactants, interfaces and pores : a theoretical study

    NARCIS (Netherlands)

    Huinink, H.

    1998-01-01

    The aim of this study was to investigate the behavior of surfactants in porous media by theoretical means. The influence of curvature of a surface on the adsorption has been studied with a mean field lattice (MFL) model, as developed by Scheutjens and Fleer. An analytical theory has been

  5. Are Mechanistic and Statistical QSAR Approaches Really Different? MLR Studies on 158 Cycloalkyl-Pyranones.

    Science.gov (United States)

    Bhhatarai, Barun; Garg, Rajni; Gramatica, Paola

    2010-07-12

    Two parallel approaches for quantitative structure-activity relationships (QSAR) are predominant in literature, one guided by mechanistic methods (including read-across) and another by the use of statistical methods. To bridge the gap between these two approaches and to verify their main differences, a comparative study of mechanistically relevant and statistically relevant QSAR models, developed on a case study of 158 cycloalkyl-pyranones, biologically active on inhibition (Ki ) of HIV protease, was performed. Firstly, Multiple Linear Regression (MLR) based models were developed starting from a limited amount of molecular descriptors which were widely proven to have mechanistic interpretation. Then robust and predictive MLR models were developed on the same set using two different statistical approaches unbiased of input descriptors. Development of models based on Statistical I method was guided by stepwise addition of descriptors while Genetic Algorithm based selection of descriptors was used for the Statistical II. Internal validation, the standard error of the estimate, and Fisher's significance test were performed for both the statistical models. In addition, external validation was performed for Statistical II model, and Applicability Domain was verified as normally practiced in this approach. The relationships between the activity and the important descriptors selected in all the models were analyzed and compared. It is concluded that, despite the different type and number of input descriptors, and the applied descriptor selection tools or the algorithms used for developing the final model, the mechanistical and statistical approach are comparable to each other in terms of quality and also for mechanistic interpretability of modelling descriptors. Agreement can be observed between these two approaches and the better result could be a consensus prediction from both the models. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Theoretical and simulation studies of seeding methods

    Energy Technology Data Exchange (ETDEWEB)

    Pellegrini, Claudio [Univ. of California, Los Angeles, CA (United States)

    2017-12-11

    We report the theoretical and experimental studies done with the support of DOE-Grant DE-SC0009983 to increase an X-ray FEL peak power from the present level of 20 to 40 GW to one or more TW by seeding, undulator tapering and using the new concept of the Double Bunch FEL.

  7. THEORETICAL STUDY ON ELECTRONIC STRUCTURES AND ...

    African Journals Online (AJOL)

    THEORETICAL STUDY ON ELECTRONIC STRUCTURES AND SPECTROSCOPY OF TRIARYLBORANE SUBSTITUTED BY THIOPHENE. ... Also, the 13C chemical shifts of the carbon atoms on the phenyl rings in these compounds are upfield relative to those of the same carbon atoms in the parent compound.

  8. Can Supported Reduced Vanadium Oxides form H2from CH3OH? A Computational Gas-Phase Mechanistic Study.

    Science.gov (United States)

    González-Navarrete, Patricio; Andrés, Juan; Calatayud, Monica

    2018-02-01

    A detailed density functional theory study is presented to clarify the mechanistic aspects of the methanol (CH 3 OH) dehydrogenation process to yield hydrogen (H 2 ) and formaldehyde (CH 2 O). A gas-phase vanadium oxide cluster is used as a model system to represent reduced V(III) oxides supported on TiO 2 catalyst. The theoretical results provide a complete scenario, involving several reaction pathways in which different methanol adsorption sites are considered, with presence of hydride and methoxide intermediates. Methanol dissociative adsorption process is both kinetically and thermodynamically feasible on V-O-Ti and V═O sites, and it might lead to form hydride species with interesting catalytic reactivity. The formation of H 2 and CH 2 O on reduced vanadium sites, V(III), is found to be more favorable than for oxidized vanadium species, V(V), taking place along energy barriers of 29.9 and 41.0 kcal/mol, respectively.

  9. Safety, Efficacy, and Mechanistic Studies Regarding Citrus aurantium (Bitter Orange) Extract and p‐Synephrine

    OpenAIRE

    Stohs, Sidney J.

    2017-01-01

    Citrus aurantium L. (bitter orange) extracts that contain p‐synephrine as the primary protoalkaloid are widely used for weight loss/weight management, sports performance, appetite control, energy, and mental focus and cognition. Questions have been raised about the safety of p‐synephrine because it has some structural similarity to ephedrine. This review focuses on current human, animal, in vitro, and mechanistic studies that address the safety, efficacy, and mechanisms of action of bitter or...

  10. Theoretical studies on energetic materials bearing pentaflurosulphyl ...

    Indian Academy of Sciences (India)

    Theoretical studies on the compounds with SF5 groups. 1167. Table 2. Calculated total energies (E0), zero-point energies (ZPE), densities and heats of formation (HOFs) for the title energetic materials. E0 and ZPE are in a.u., HOFs are in kJ/mol, densities are in g/cm3. Compound. E0. ZPE. Hf, gas. Hf, sub. Hf, solid. Density.

  11. CO oxidation on gold nanoparticles: Theoretical studies

    DEFF Research Database (Denmark)

    Remediakis, Ioannis; Lopez, Nuria; Nørskov, Jens Kehlet

    2005-01-01

    We present a summary of our theoretical results regarding CO oxidation on both oxide-supported and isolated gold nanoparticles. Using Density Functional Theory we have studied the adsorption of molecules and the oxidation reaction of CO on gold clusters. Low-coordinated sites on the gold...... nanoparticles can adsorb small inorganic molecules such as O2 and CO, and the presence of these sites is the key factor for the catalytic properties of supported gold nanoclusters. Other contributions, induced by the presence of the support, can provide parallel channels for the reaction and modulate the final...

  12. Theoretical pluralism in psychoanalytic case studies

    Directory of Open Access Journals (Sweden)

    Jochem eWillemsen

    2015-09-01

    Full Text Available The aim of this study is to provide an overview of the scientific activity of different psychoanalytic schools of thought in terms of the content and production of case studies published on ISI Web of Knowledge. Between March 2013 and November 2013, we contacted all case study authors included in the online archive of psychoanalytic and psychodynamic case studies (www.singlecasearchive.com to inquire about their psychoanalytic orientation during their work with the patient. The response rate for this study was 45%. It appears that the two oldest psychoanalytic schools, Object-relations psychoanalysis and Ego psychology or ‘Classical psychoanalysis’ dominate the literature of published case studies. However, most authors stated that they feel attached to two or more psychoanalytic schools of thought. This confirms that the theoretical pluralism in psychoanalysis stretches to the field of single case studies. The single case studies of each psychoanalytic school are described separately in terms of methodology, patient, therapist, or treatment features. We conclude that published case studies features are fairly similar across different psychoanalytic schools. The results of this study are not representative of all psychoanalytic schools, as some do not publish their work in ISI ranked journals.

  13. Theoretical pluralism in psychoanalytic case studies

    Science.gov (United States)

    Willemsen, Jochem; Cornelis, Shana; Geerardyn, Filip M.; Desmet, Mattias; Meganck, Reitske; Inslegers, Ruth; Cauwe, Joachim M. B. D.

    2015-01-01

    The aim of this study is to provide an overview of the scientific activity of different psychoanalytic schools of thought in terms of the content and production of case studies published on ISI Web of Knowledge. Between March 2013 and November 2013, we contacted all case study authors included in the online archive of psychoanalytic and psychodynamic case studies (www.singlecasearchive.com) to inquire about their psychoanalytic orientation during their work with the patient. The response rate for this study was 45%. It appears that the two oldest psychoanalytic schools, Object-relations psychoanalysis and Ego psychology or “Classical psychoanalysis” dominate the literature of published case studies. However, most authors stated that they feel attached to two or more psychoanalytic schools of thought. This confirms that the theoretical pluralism in psychoanalysis stretches to the field of single case studies. The single case studies of each psychoanalytic school are described separately in terms of methodology, patient, therapist, or treatment features. We conclude that published case studies features are fairly similar across different psychoanalytic schools. The results of this study are not representative of all psychoanalytic schools, as some do not publish their work in ISI ranked journals. PMID:26483725

  14. Safety, Efficacy, and Mechanistic Studies Regarding Citrus aurantium (Bitter Orange) Extract and p-Synephrine.

    Science.gov (United States)

    Stohs, Sidney J

    2017-10-01

    Citrus aurantium L. (bitter orange) extracts that contain p-synephrine as the primary protoalkaloid are widely used for weight loss/weight management, sports performance, appetite control, energy, and mental focus and cognition. Questions have been raised about the safety of p-synephrine because it has some structural similarity to ephedrine. This review focuses on current human, animal, in vitro, and mechanistic studies that address the safety, efficacy, and mechanisms of action of bitter orange extracts and p-synephrine. Numerous studies have been conducted with respect to p-synephrine and bitter orange extract because ephedra and ephedrine were banned from use in dietary supplements in 2004. Approximately 30 human studies indicate that p-synephrine and bitter orange extracts do not result in cardiovascular effects and do not act as stimulants at commonly used doses. Mechanistic studies suggest that p-synephrine exerts its effects through multiple actions, which are discussed. Because p-synephrine exhibits greater adrenergic receptor binding in rodents than humans, data from animals cannot be directly extrapolated to humans. This review, as well as several other assessments published in recent years, has concluded that bitter orange extract and p-synephrine are safe for use in dietary supplements and foods at the commonly used doses. Copyright © 2017 The Authors Phytotherapy Research Published by John Wiley & Sons Ltd. Copyright © 2017 The Authors Phytotherapy Research Published by John Wiley & Sons Ltd.

  15. Safety, Efficacy, and Mechanistic Studies Regarding Citrus aurantium (Bitter Orange) Extract and p‐Synephrine

    Science.gov (United States)

    2017-01-01

    Citrus aurantium L. (bitter orange) extracts that contain p‐synephrine as the primary protoalkaloid are widely used for weight loss/weight management, sports performance, appetite control, energy, and mental focus and cognition. Questions have been raised about the safety of p‐synephrine because it has some structural similarity to ephedrine. This review focuses on current human, animal, in vitro, and mechanistic studies that address the safety, efficacy, and mechanisms of action of bitter orange extracts and p‐synephrine. Numerous studies have been conducted with respect to p‐synephrine and bitter orange extract because ephedra and ephedrine were banned from use in dietary supplements in 2004. Approximately 30 human studies indicate that p‐synephrine and bitter orange extracts do not result in cardiovascular effects and do not act as stimulants at commonly used doses. Mechanistic studies suggest that p‐synephrine exerts its effects through multiple actions, which are discussed. Because p‐synephrine exhibits greater adrenergic receptor binding in rodents than humans, data from animals cannot be directly extrapolated to humans. This review, as well as several other assessments published in recent years, has concluded that bitter orange extract and p‐synephrine are safe for use in dietary supplements and foods at the commonly used doses. Copyright © 2017 The Authors Phytotherapy Research Published by John Wiley & Sons Ltd. PMID:28752649

  16. Theoretical studies on aerosol agglomeration processes

    Energy Technology Data Exchange (ETDEWEB)

    Lehtinen, K.E.J. [VTT Energy, Espoo (Finland). Energy Use

    1997-12-31

    In this thesis, theoretical modeling of certain aerosol systems has been presented. At first, the aerosol general dynamic equation is introduced, along with a discretization routine for its numerical solution. Of the various possible phenomena affecting aerosol behaviour, this work is mostly focused on aerosol agglomeration. The fundamentals of aerosol agglomeration theory are thus briefly reviewed. The two practical applications of agglomeration studied in this thesis are flue gas cleaning using an electrical agglomerator and nanomaterial synthesis with a free jet reactor. In an electrical agglomerator the aerosol particles are charged and brought into an alternating electric field. The aim is to remove submicron particles from flue gases by collisions with larger particles before conventional gas cleaning devices that have a clear penetration window in the problematic 0.1-1{mu}m size range. A mathematical model was constructed to find out the effects of the different system parameters on the agglomerator`s performance. A crucial part of this task was finding out the collision efficiencies of particles of varying size and charge. The original idea was to use unipolar charging of the particles, and a laboratory scale apparatus was constructed for this purpose. Both theory and experiments clearly show that significant removal of submicron particles can not be achieved by such an arrangement. The theoretical analysis further shows that if the submicron particles and the large collector particles were charged with opposite polarity, significant removal of the submicron particles could be obtained. The second application of agglomeration considered in this thesis is predicting/controlling nanoparticle size in the gas-to-particle aerosol route to material synthesis. In a typical material reactor, a precursor vapor reacts to form molecules of the desired material. In a cooling environment, a particulate phase forms, the dynamics of which are determined by the rates of

  17. Mechanistic study of manganese-substituted glycerol dehydrogenase using a kinetic and thermodynamic analysis.

    Directory of Open Access Journals (Sweden)

    Baishan Fang

    Full Text Available Mechanistic insights regarding the activity enhancement of dehydrogenase by metal ion substitution were investigated by a simple method using a kinetic and thermodynamic analysis. By profiling the binding energy of both the substrate and product, the metal ion's role in catalysis enhancement was revealed. Glycerol dehydrogenase (GDH from Klebsiella pneumoniae sp., which demonstrated an improvement in activity by the substitution of a zinc ion with a manganese ion, was used as a model for the mechanistic study of metal ion substitution. A kinetic model based on an ordered Bi-Bi mechanism was proposed considering the noncompetitive product inhibition of dihydroxyacetone (DHA and the competitive product inhibition of NADH. By obtaining preliminary kinetic parameters of substrate and product inhibition, the number of estimated parameters was reduced from 10 to 4 for a nonlinear regression-based kinetic parameter estimation. The simulated values of time-concentration curves fit the experimental values well, with an average relative error of 11.5% and 12.7% for Mn-GDH and GDH, respectively. A comparison of the binding energy of enzyme ternary complex for Mn-GDH and GDH derived from kinetic parameters indicated that metal ion substitution accelerated the release of dioxyacetone. The metal ion's role in catalysis enhancement was explicated.

  18. Theoretical and experimental studies of elementary physics

    International Nuclear Information System (INIS)

    Bodek, A.; Ferbel, T.; Melissinos, A.C.; Slattery, P.; Tipton, P.; Das, A.; Hagen, C.R.; Rajeev, S.G.; Okubo, S.; Orr, L.

    1993-01-01

    The various components of the high-energy physics research program at the University of Rochester are presented. (I)Fixed-target experimentation at FNAL includes studies of direct photon production by p and π on H, Be, and Cu, and hybrid mesons and other physics issues in Coulomb excitation at high energies. (II)The status of the GEM (Gammas, Electrons, and Muons) Experiment at the SSC is given. (III)The D-Zero experiment at FNAL is reviewed. (IV)Deep inelastic lepton--nucleon scattering experiments are summarized: electron scattering experiments at SLAC, FNAL neutrino quad triplet runs, FNAL neutrino sign selected experiments, and SDC cosmic ray test and test beam calibration. (V)Studies of nonlinear QED at SLAC concentrated on a study of QED at critical field strength in intense laser--high-energy electron collisions. (VI)Development work on the Collider Detector at Fermilab (CDF) emphasized the CDF silicon vertex detector, the end plug calorimeter, and the SDC tile/fiber calorimetry. (VII)The theoretical physics effort is sketched

  19. Theoretical study of defect properties in metals

    International Nuclear Information System (INIS)

    Sindzingre, P.

    1987-01-01

    Several characteristic properties (formation and migration enthalpies and volumes, dipole tensors, effects on shear elastic constants) of several point defects (vacancy, divacancy, interstitial, di-interstitial) in different metals: f.c.c. metals (Al, Cu, Ag, Au), h.c.p. metals (Be, Mg, Zn, Cd, Na, Co, Ti, Zr), b.c.c. metals (Li, Na, K, Rb, Cs) have been calculated. The calculated properties are evaluated from static computations performed with pair potentials derived from pseudo-potential theory (for simple or noble metals) or deduced empirically. Results are compared with available experimental data with previous theoretical works. The first part of this work where we have studied point defects properties in f.c.c. metals lead us to suggest a more convincing interpretation of X-ray scattering and elastic relation measurements concerning interstitials in Al and Cu, and a new interpretation for X-ray scattering measurements concerning di-interstitials in Al. In the second part, devoted to h.c.p. metals we are brought to propose for each studied metal the interstitial configurations which yield the best agreement with experimental results. The third part, devoted to the study of point defects in alkalin b.c.c. metals lead us to interpret self-diffusion in these metals with the assumption of a simultaneous contribution of monovacancies, divacancies and interstitials [fr

  20. Mechanistic studies of copper(I)-catalyzed 1,3-halogen migration.

    Science.gov (United States)

    Van Hoveln, Ryan; Hudson, Brandi M; Wedler, Henry B; Bates, Desiree M; Le Gros, Gabriel; Tantillo, Dean J; Schomaker, Jennifer M

    2015-04-29

    An ongoing challenge in modern catalysis is to identify and understand new modes of reactivity promoted by earth-abundant and inexpensive first-row transition metals. Herein, we report a mechanistic study of an unusual copper(I)-catalyzed 1,3-migration of 2-bromostyrenes that reincorporates the bromine activating group into the final product with concomitant borylation of the aryl halide bond. A combination of experimental and computational studies indicated this reaction does not involve any oxidation state changes at copper; rather, migration occurs through a series of formal sigmatropic shifts. Insight provided from these studies will be used to expand the utility of aryl copper species in synthesis and develop new ligands for enantioselective copper-catalyzed halogenation.

  1. Pollution and skin: from epidemiological and mechanistic studies to clinical implications.

    Science.gov (United States)

    Krutmann, Jean; Liu, Wei; Li, Li; Pan, Xiaochuan; Crawford, Martha; Sore, Gabrielle; Seite, Sophie

    2014-12-01

    In recent years, the health effects associated with air pollution have been intensively studied. Most studies focus on air pollution effects on the lung and the cardiovascular system. More recently, however, epidemiological and mechanistic studies suggest that air pollution is also affecting skin integrity. This state-of-the-art review focuses on this latter aspect; it was developed with the collaboration of European and Chinese board of experts with specific interests in environmental health, clinical and basic research in dermatology and cosmetic dermatology. A literature review limited to pollution and health effects and (sensitive) skin was performed using PubMed. Review and original articles were chosen. We summarize the existing scientific evidence that air pollution exerts detrimental effects on human skin, discuss potential clinical implications and suggest specific and unspecific cosmetic protective measures. Copyright © 2014 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.

  2. Theoretical and experimental study of thermoacoustic engines

    Science.gov (United States)

    Raspet, Richard; Bass, Henry E.; Arnott, W. P.

    1992-12-01

    A three year study of thermoacoustic engines operating as prime movers and refrigerators was completed. The major thrust of this effort was the use and theoretical description of ceramic honeycomb structures as the active element in thermoacoustic engines. An air-filled demonstration prime mover was constructed and demonstrated at Acoustical Society of America and IEE meetings. A helium-filled test prime mover was designed and built an is being employed in studies of the threshold of oscillation as a function of temperature difference and pressure. In addition, acoustically based theories of the thermoacoustic engine have been developed and tested for a parallel plate stack at the Naval Postgraduate School and for a honeycomb stack at the University of Mississippi. Most of this work is described in detail in the attached publications. In this report we will give an overview of the research completed to date and its relationship to work performed at the Naval Postgraduate School and to future work at the University of Mississippi.

  3. Studies In Theoretical High Energy Particle Physics

    Energy Technology Data Exchange (ETDEWEB)

    Keung, Wai Yee [Univ. of Illinois, Chicago, IL (United States)

    2017-07-01

    This is a final technical report for grant no. DE-SC0007948 describing research activities in theoretical high energy physics at University of Illinois at Chicago for the whole grant period from July 1, 2012 to March 31, 2017.

  4. Theoretical aspects of coping strategies study

    OpenAIRE

    Kabiyeva, M.; Kasen, G. A.

    2015-01-01

    In article based on a thorough analysis of classical and modern foreign and domestic literature examines the notion of coping strategies, approaches to the understanding of coping. Theoretically proved that coping is an individual way to interact with the situation according to its own logic, psychological capabilities and its importance in human life, the level of development of coping resources provides a successful adaptation to stress. From the analysis of theoretical literature, we saw t...

  5. Theoretical study of free electron laser physics

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Jae Gwon; Cho, Sung Oh; Jeong, Young Uk; Kim, Sun Kook; Lee, Byung Cheol; Cha, Byung Heon; Lee, Jong Min [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2000-04-01

    A theoretical study of free electron laser physics is presented in this report. In particular, an analysis is given of the free electron laser with a linearly polarized magnetic wiggler. We describe the basic electron dynamics and gain mechanism in a free electron laser by solving the one-body classical Lorentz force equations in the presence of a periodic magnetic field and a plane electromagnetic wave. Phase space paths for electrons analogously related to those of a simple pendulum are used to describe the laser gain and saturation, and the evolution of the electron beam energy and position distributions. We present an analysis of the single-mode problem and a self-consistent nonlinear treatment of the finite transverse dimensional effects associated with the free electron laser in a steady state. Results computed by applying an external D.C. electric field to the system are discussed for investigating efficiency enhancement of the free electron lasers. Finally optical guiding effect in small signal regime is described to investigate the possibility of amplifying radiation fields in very long wigglers for large gain and high extraction efficiency. 14 refs., 45 figs. (Author)

  6. Competitive gold-activation modes in terminal alkynes: an experimental and mechanistic study.

    Science.gov (United States)

    Gimeno, Ana; Cuenca, Ana B; Suárez-Pantiga, Samuel; de Arellano, Carmen Ramírez; Medio-Simón, Mercedes; Asensio, Gregorio

    2014-01-13

    The competition between π- and dual σ,π-gold-activation modes is revealed in the gold(I)-catalyzed heterocyclization of 1-(o-ethynylaryl)urea. A noticeable effect of various ligands in gold complexes on the choice of these activation modes is described. The cationic [Au(IPr)](+) (IPr=2,6-bis(diisopropylphenyl)imidazol-2-ylidene) complex cleanly promotes the π activation of terminal alkynes, whereas [Au(PtBu3 )](+) favors intermediate σ,π species. In this experimental and mechanistic study, which includes kinetic and cross-over experiments, several σ-gold, σ,π-gold, and other gold polynuclear reaction intermediates have been isolated and identified by NMR spectroscopy, X-ray diffraction, or MALDI spectrometry. The ligand control in the simultaneous or alternative π- and σ,π-activation modes is also supported by deuterium-labeling experiments. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Theoretical Study of a Spherical Plasma Focus

    Science.gov (United States)

    Ay, Yasar

    A theoretical model is developed for two concentric electrodes spherical plasma focus device in order to investigate the plasma sheath dynamics, radiative emission, and the ion properties. The work focuses on the model development of the plasma sheath dynamics and its validation, followed by studying of the radiation effects and the beam-ion properties in such unique geometry as a pulsed source for neutrons, soft and hard x-rays, and electron and ion beams. Chapter 1 is an introduction on fusion systems including plasma focus. Chapter 2 is an extensive literature survey on plasma focus modeling and experiments including the various radiations and their mechanism. Chapter 3 details modeling and validation of the plasma sheath dynamics model with comparison between hydrogen, deuterium, tritium and deuterium-tritium mixture for the production of pulsed neutrons. Chapter 4 is a study of the radiative phase, in which neutron yield is investigated, as well as the predicted beam-ion properties. Chapter 5 summarizes and discusses the results. Chapter 6 provides concluding remarks and proposed future works. The phases of the developed model are the rundown phase I, rundown phase II, the reflected phase and a radiative phase. The rundown phase I starts immediately after the completion of the gas breakdown and ends when the current sheath reaches the equator point of the spherical shape. Then immediately followed by rundown phase II to start and it ends when the shock front hits the axis, which is the beginning of the reflected shock phase. Reflected shock front moves towards the incoming current sheath and meets it which is both the end of the reflected shock phase and the beginning of the radiative phase. After the reflected shock front and the current sheath meet, the current sheath continues to move radially inward by compressing the produced plasma column until it reaches the axis. Since the discharge current contains important information about the plasma dynamic

  8. Application of comparative vibrational spectroscopic and mechanistic studies in analysis of fisetin structure

    Science.gov (United States)

    Dimitrić Marković, Jasmina M.; Marković, Zoran S.; Milenković, Dejan; Jeremić, Svetlana

    2011-12-01

    This paper addresses experimental and theoretical research in fisetin (2-(3,4-dihydroxyphenyl)-3,7-dihydroxychromen-4-one) structure by means of experimental IR and Raman spectroscopies and mechanistic calculations. Density Functional Theory calculations, with M05-2X functional and the 6-311+G (2df, p) basis set implemented in the Gaussian 09 package, are performed with the aim to support molecular structure, vibrational bands' positions and their intensities. Potential energy distribution (PED) values and the description of the largest vibrational contributions to the normal modes are calculated. The most intense bands appear in the 1650-1500 cm -1 wavenumber region. This region involves a combination of the C dbnd O, C2 dbnd C3 and C-C stretching vibrational modes. Most of the bands in the 1500-1000 cm -1 range involve C-C stretching, O-C stretching and in-plane C-C-H, C-O-H, C-C-O and C-C-C bending vibrations of the rings. The region below 1000 cm -1 is characteristic to the combination of in plane C-C-C-H, H-C-C-H, C-C-C-C, C-C-O-C and out of plane O-C-C-C, C-C-O-C, C-C-C-C torsional modes. The Raman spectra of baicalein and quercetin were used for qualitative comparison with fisetin spectrum and verification of band assignments. The applied detailed vibrational spectral analysis and the assignments of the bands, proposed on the basis of fundamentals, reproduced the experimental results with high degree of accuracy.

  9. Theoretical study of conjugated porphyrin polymers

    DEFF Research Database (Denmark)

    Pedersen, T.G.; Lynge, T.B.; Kristensen, P.K.

    2005-01-01

    for these applications. From a theoretical analysis of excitons in long metalloporphyrin chains, we demonstrate that the binding energy is much lower than in usual conjugated polymers. Our calculated absorption spectra are in good agreement with measurements. (c) 2004 Elsevier B.V. All rights reserved....

  10. Theoretical study of the electron paramagnetic resonance ...

    Indian Academy of Sciences (India)

    Abstract. The electron paramagnetic resonance (EPR) parameters (the g factors, hy- perfine structure constants and the superhyperfine parameters) for the tetragonal Ir2+ centre in NaCl are theoretically investigated from the perturbation formulas of these parameters for a 5d7 ion in tetragonally elongated octahedra.

  11. Theoretical Studies in Elementary Particle Physics

    Energy Technology Data Exchange (ETDEWEB)

    Collins, John C.; Roiban, Radu S

    2013-04-01

    This final report summarizes work at Penn State University from June 1, 1990 to April 30, 2012. The work was in theoretical elementary particle physics. Many new results in perturbative QCD, in string theory, and in related areas were obtained, with a substantial impact on the experimental program.

  12. EXPERIMENT AL AND THEORETICAL STUDY OF PRECAST ...

    African Journals Online (AJOL)

    In such type of construction, the fresh concrete can be directly poured on the precast beam elements and hollow concrete blocks, which bridge the space between the beams. However, the safety of such construction must be ensured through theoretical investigations supported by experimental verifications. The purpose of ...

  13. A Correlational Study of Students' Theoretical and Practical

    African Journals Online (AJOL)

    Galadanci & Mukhtar

    the examinations are theoretical; either in the form of multiple choice questions or essay questions. In a few subjects, such as. Physics, Chemistry and Biology, where the course of study has a substantial practical component over and above the theoretical component, students are given both theoretical and practical.

  14. Mechanistic and Technical Challenges in Studying the Human Microbiome and Cancer Epidemiology

    Science.gov (United States)

    2016-01-01

    This article reviews the significance of the microbiome in cancer epidemiology, mechanistic and technical challenges in the field, and characterization of the microbiome in different tumor types to identify biomarkers of risk, progression, and prognosis. Publications on the microbiome and cancer epidemiology were reviewed to analyze sample collection and processing, microbiome taxa characterization by 16S ribosomal RNA sequencing, and microbiome metabolite characterization (metabotyping) by nuclear magnetic resonance and mass spectrometry. The analysis identified methodology types, research design, sample types, and issues in integrating data from different platforms. Aerodigestive cancer epidemiology studies conducted by different groups demonstrated the significance of microbiome information in developing approaches to improve health. Challenges exist in sample preparation and processing (eg, standardization of methods for collection and analysis). These challenges relate to technology, data integration from “omics” studies, inherent bias in primer selection during 16S ribosomal RNA sequencing, the need for large consortia with well-characterized biospecimens, cause and effect issues, resilience of microbiota to exposure events (requires longitudinal studies), and expanding studies for fungal and viral diversity (most studies used bacterial 16S ribosomal RNA sequencing for microbiota characterization). Despite these challenges, microbiome and cancer epidemiology studies are significant and may facilitate cancer risk assessment, diagnosis, and prognosis. In the future, clinical trials likely will use microbiota modifications to improve the efficacy of existing treatments. PMID:27121074

  15. Mechanistic and Technical Challenges in Studying the Human Microbiome and Cancer Epidemiology.

    Science.gov (United States)

    Verma, Mukesh

    2017-04-01

    This article reviews the significance of the microbiome in cancer epidemiology, mechanistic and technical challenges in the field, and characterization of the microbiome in different tumor types to identify biomarkers of risk, progression, and prognosis. Publications on the microbiome and cancer epidemiology were reviewed to analyze sample collection and processing, microbiome taxa characterization by 16S ribosomal RNA sequencing, and microbiome metabolite characterization (metabotyping) by nuclear magnetic resonance and mass spectrometry. The analysis identified methodology types, research design, sample types, and issues in integrating data from different platforms. Aerodigestive cancer epidemiology studies conducted by different groups demonstrated the significance of microbiome information in developing approaches to improve health. Challenges exist in sample preparation and processing (eg, standardization of methods for collection and analysis). These challenges relate to technology, data integration from "omics" studies, inherent bias in primer selection during 16S ribosomal RNA sequencing, the need for large consortia with well-characterized biospecimens, cause and effect issues, resilience of microbiota to exposure events (requires longitudinal studies), and expanding studies for fungal and viral diversity (most studies used bacterial 16S ribosomal RNA sequencing for microbiota characterization). Despite these challenges, microbiome and cancer epidemiology studies are significant and may facilitate cancer risk assessment, diagnosis, and prognosis. In the future, clinical trials likely will use microbiota modifications to improve the efficacy of existing treatments.

  16. Studies in theoretical high energy particle physics

    International Nuclear Information System (INIS)

    Aratyn, H.; Brekke, L.; Keung, Wai-Yee; Sukhatme, U.

    1993-01-01

    Theoretical work on the following topics is briefly summarized: symmetry structure of conformal affine Toda model and KP hierarchy; solitons in the affine Toda and conformal affine Toda models; classical r-matrices and Poisson bracket structures on infinite-dimensional groups; R-matrix formulation of KP hierarchies and their gauge equivalence; statistics of particles and solitons; charge quantization in the presence of an Alice string; knotting and linking of nonabelian flux; electric dipole moments; neutrino physics in gauge theories; CP violation in the high energy colliders; supersymmetric quantum mechanics; parton structure functions in nuclei; dual parton model. 38 refs

  17. Theoretical studies in elementary particle physics

    International Nuclear Information System (INIS)

    Collins, J.

    1994-01-01

    This is a report on research conducted at Penn State University under grant number DE-FG02-90ER-40577, from November 1992 to present. The author is a member of the CTEQ collaboration (Coordinated Theoretical and Experimental Project on Quantitative QCD). Some of the work in CTEQ is described in this report. Topics which the authors work has touched include: polarized hard scattering; hard diffraction; small x and perturbative pomeron physics; gauge-invariant operators; fundamental QCD; heavy quarks; instantons and deep inelastic scattering; non-perturbative corrections to τ decay

  18. Reactivity of γ-Terpinene with NO3 radicals: experimental approach for kinetic and mechanistic study.

    Science.gov (United States)

    Fouqueau, Axel; Cirtog, Manuela; Le Quilleuc, Meryll; Cazaunau, Mathieu; Pangui, Edouard; Duncianu, Marius; Doussin, Jean-François; Picquet-Varrault, Bénédicte

    2017-04-01

    Biogenic Volatile Organic Compounds (BVOC) are highly emitted by vegetation and play a key role in atmospheric chemistry. They are very reactive with atmospheric oxidants (OH, NO3, ozone) and significantly contribute to the formation of Secondary Organic Aerosol (SOA) at the global scale [1]. In addition, night-time chemistry initiated by NO3 radicals leads to the formation of organic nitrates which behave as reservoirs for reactive nitrogen. However, the reactivity of NO3 radical with BVOCs other than isoprene and α- and β-pinene, remains poorly understood. Among the BVOCs, γ-Terpinene is one of the most emitted by vegetation[2]. Two kinetic works were previously published on γ-Terpinene [3] [4], but mechanistic has never been studied. Thus, the aim of this work is to study the reactivity of γ-Terpinene with NO3 by performing experiments in simulation chambers. Kinetic, mechanism and SOA yield will be investigated. For this purpose, two different simulation chambers have been used: - First one, consisting of a Pyrex reactor of 1 m3 [5] coupled to a long path in situ FTIR spectrometer and a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS) in NO+ mode which was internally developed in LISA, to measure organic nitrates concentration. - Second one, the CESAM chamber (http://cesam.cnrs.fr) [6] is a 4.2 m3 stainless steel chamber which permits to conduct SOA experiments at different temperature and relative humidity. In situ FTIR and PTR-ToF-MS are used to measure gaseous concentrations, and a SMPS was used to characterize particulate phase. Kinetic and mechanistic results will be discussed and compared with the literature values. References [1] Brown S. S., Stutz J., Nighttime radical observations and chemistry. Chem. Soc. Rev. (2012) 41, 6405-6447 [2] Helmig D., Klinger L.F., et al., Biogenic volatile organic compound emissions (BVOCs) I. Identifications from three continental sites in the U.S. Chemosphere. (1999), Vol. 38, No. 9, pp. 2163

  19. Utilizing Mechanistic Cross-Linking Technology to Study Protein-Protein Interactions: An Experiment Designed for an Undergraduate Biochemistry Lab

    Science.gov (United States)

    Finzel, Kara; Beld, Joris; Burkart, Michael D.; Charkoudian, Louise K.

    2017-01-01

    Over the past decade, mechanistic cross-linking probes have been used to study protein-protein interactions in natural product biosynthetic pathways. This approach is highly interdisciplinary, combining elements of protein biochemistry, organic chemistry, and computational docking. Herein, we described the development of an experiment to engage…

  20. Planarians as models of cadmium-induced neoplasia provide measurable benchmarks for mechanistic studies.

    Science.gov (United States)

    Voura, Evelyn B; Montalvo, Melissa J; Dela Roca, Kevin T; Fisher, Julia M; Defamie, Virginie; Narala, Swami R; Khokha, Rama; Mulligan, Margaret E; Evans, Colleen A

    2017-08-01

    Bioassays of planarian neoplasia highlight the potential of these organisms as useful standards to assess whether environmental toxins such as cadmium promote tumorigenesis. These studies complement other investigations into the exceptional healing and regeneration of planarians - processes that are driven by a population of active stem cells, or neoblasts, which are likely transformed during planarian tumor growth. Our goal was to determine if planarian tumorigenesis assays are amenable to mechanistic studies of cadmium carcinogenesis. To that end we demonstrate, by examining both counts of cell populations by size, and instances of mitosis, that the activity of the stem cell population can be monitored. We also provide evidence that specific biomodulators can affect the potential of planarian neoplastic growth, in that an inhibitor of metalloproteinases effectively blocked the development of the lesions. From these results, we infer that neoblast activity does respond to cadmium-induced tumor growth, and that metalloproteinases are required for the progression of cancer in the planarian. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Mechanistic studies of thioxanthone–carbazole as a one-component type II photoinitiator

    Energy Technology Data Exchange (ETDEWEB)

    Karaca, Nurcan; Karaca Balta, Demet; Ocal, Nuket; Arsu, Nergis, E-mail: nergisarsu@gmail.com

    2014-02-15

    A mechanistic study concerning photoinitiated free radical polymerization using Thioxanthone–Carbazole (TX–Cz) as a one-component Type II photoinitiator was performed. TX–Cz presented visible initiator characteristics with absorptions at 434 and 414 nm where the molar absorption coefficients were 2014 and 1754 L mol{sup −1} cm{sup −1}, respectively. Fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to study the photophysical properties of TX–Cz. In addition, photopolymerization of methyl methacrylate (MMA) showed that TX–Cz is efficient photoinitiator. To explain the initiation mechanism of TX–Cz, fluorescence and phosphorescence emission spectra of poly (methyl methacrylate) (PMMA) were also taken to see whether the initiator covalently bonded to the polymer. The postulated mechanism is based on inter- molecular reaction of the triplet, {sup 3}(TX–Cz){sup ⁎} with the carbazole moiety at ground state, TX–Cz. The photoinitiation efficiency of TX–Cz during gelation of multifunctional acrylates was also investigated by Photo-Differential Scanning Calorimetry (Photo-DSC) technique and high polymerization rates were obtained. -- Highlights: • Thioxanthone–Carbazole was used as visible light photoinitiator for radical polymerization of meth(acrylates). • The detailed photophysical properties of TX–Cz was reported. • Fluorescence quantum yield, phosphorescence lifetime , triplet energy and triplet lifetime were determined. • Photo-DSC was used to follow photopolymerizatin kinetics of acrylates.

  2. Kinetic and mechanistic studies of free-radical reactions in combustion

    Energy Technology Data Exchange (ETDEWEB)

    Tully, F.P. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    Combustion is driven by energy-releasing chemical reactions. Free radicals that participate in chain reactions carry the combustion process from reactants to products. Research in chemical kinetics enables us to understand the microscopic mechanisms involved in individual chemical reactions as well as to determine the rates at which they proceed. Both types of information are required for an understanding of how flames burn, why engines knock, how to minimize the production of pollutants, and many other important questions in combustion. In this program the authors emphasize accurate measurements over wide temperature ranges of the rates at which ubiquitous free radicals react with stable molecules. The authors investigate a variety of OH, CN, and CH + stable molecule reactions important to fuel conversion, emphasizing application of the extraordinarily precise technique of laser photolysis/continuous-wave laser-induced fluorescence (LP/cwLIF). This precision enables kinetic measurements to serve as mechanistic probes. Since considerable effort is required to study each individual reaction, prudent selection is critical. Two factors encourage selection of a specific reaction: (1) the rates and mechanisms of the subject reaction are required input to a combustion model; and (2) the reaction is a chemical prototype which, upon characterization, will provide fundamental insight into chemical reactivity, facilitate estimation of kinetic parameters for similar reactions, and constrain and test the computational limits of reaction-rate theory. Most studies performed in this project satisfy both conditions.

  3. Solar pond conception - experimental and theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Kurt, Huseyin [Zonguldak Karaelmas Univ., Technical Education Faculty, Karabuk (Turkey); Halici, Fethi [Sakarya Univ., Mechanical Engineering Dept., Adapazari (Turkey); Binark, A. Korhan [Marmara Univ., Technical Education Faculty, Istanbul (Turkey)

    2000-07-01

    A one dimensional transient mathematical model for predicting the thermal performance of the salt gradient solar pond is developed and presented. In this paper, the natural solar ponds and different artificial solar pond systems found in the literature are introduced. Necessary modifications are made on the experimental stand located in Istanbul Technical University, the experimental stand is introduced and natural phenomena produced in the pond by the different solar pond variations under natural conditions are observed. In the theoretical work based on a one dimensional unsteady state heat conduction model with internal heat generation, the energy and mass balance equations for the upper convective zone, the non-convective zone and the lower convective zone, all of which form the solar pond, are written in terms of differential equations. These equations are solved analytically and numerically. The results obtained from the analysis are compared with the experimental results. The temperature and the concentration profiles are separately presented in the figures. (Author)

  4. Isolation, characterization, and mechanistic studies of (-)-alpha-gurjunene synthase from Solidago canadensis.

    Science.gov (United States)

    Schmidt, C O; Bouwmeester, H J; Bülow, N; König, W A

    1999-04-15

    The leaves of the composite Solidago canadensis (goldenrod) were shown to contain (-)-alpha-gurjunene synthase activity. This sesquiterpene is likely to be the precursor for cyclocolorenone, a sesquiterpene ketone present in high amounts in S. canadensis leaves. (-)-alpha-Gurjunene synthase was purified to apparent homogeneity (741-fold) by anion-exchange chromatography (on several matrices), dye ligand chromatography, hydroxylapatite chromatography, and gel filtration. Chromatography on a gel filtration matrix indicated a native molecular mass of 48 kDa, and SDS-PAGE showed the enzyme to be composed of one subunit with a denatured mass of 60 kDa. Its maximum activity was observed at pH 7.8 in the presence of 10 mM Mg2+ and the KM value for the substrate farnesyl diphosphate was 5.5 microM. Over a range of purification steps (-)-alpha-gurjunene and (+)-gamma-gurjunene synthase activities copurified. In addition, the product ratio of the enzyme activity under several different assay conditions was always 91% (-)-alpha-gurjunene and 9% (+)-gamma-gurjunene. This suggests that the formation of these two structurally related products is catalyzed by one enzyme. For further confirmation, we carried out a number of mechanistic studies with (-)-alpha-gurjunene synthase, in which an enzyme preparation was incubated with deuterated substrate analogues. Based on mass spectrometry analysis of the products formed, a cyclization mechanism was postulated which makes it plausible that the synthase catalyzes the formation of both sesquiterpenes. Copyright 1999 Academic Press.

  5. A DFT study on the deprotonation antioxidant mechanistic step of ortho-substituted phenolic cation radicals

    International Nuclear Information System (INIS)

    Vafiadis, Anastasios P.; Bakalbassis, Evangelos G.

    2005-01-01

    The conformers of the 2-, 3- and 4-substituted phenolic cation radicals, 2-X-, 3-X- and 4-X-ArOH ·+ , and the respective phenoxyl radicals, ArO · , the intramolecular hydrogen bond strength (ΔH intra ) estimate along with the electronic effects of five electron withdrawing (EWG) and eight electron donating groups (EDG) on the gas-phase O-H proton dissociation enthalpies, (PDEs), of the short-lived, 2-X-ArOH ·+ , (involved in the single-electron transfer antioxidant mechanism), are studied at the DFT/B3LYP level of theory. EWG result to smaller PDEs, hence to stronger acidity; EDG to weaker acidity. The deprotonation antioxidant mechanistic step is not a rate-controlling step for 2-X-ArOH to scavenge free radicals. Approximate estimations of the ΔPDEs (hence acidities as well) can be derived from calculated structural and/or vibrational frequency values. ΔH intra s correlate reasonably with geometrical parameters for the closed-shell, neutral counterparts, in contrast with previous estimates

  6. Simple boron removal from seawater by using polyols as complexing agents: A computational mechanistic study

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Kyung; Eom, Ki Heon; Lim, Jun-Heok; Lee, Jea-Keun; Lee, Ju Dong; Won, Yong Sun [Pukyong National University, Busan (Korea, Republic of)

    2015-11-15

    The complexation of boric acid (B(OH){sub 3}), the primary form of aqueous boron at moderate pH, with polyols is proposed and mechanistically studied as an efficient way to improve membrane processes such as reverse osmosis (RO) for removing boron in seawater by increasing the size of aqueous boron compounds. Computational chemistry based on the density functional theory (DFT) was used to manifest the reaction pathways of the complexation of B(OH){sub 3} with various polyols such as glycerol, xylitol, and mannitol. The reaction energies were calculated as −80.6, −98.1, and −87.2 kcal/mol for glycerol, xylitol, and mannitol, respectively, indicating that xylitol is the most thermodynamically favorable for the complexation with B(OH){sub 3}. Moreover, the 1 : 2 molar ratio of B(OH)3 to polyol was found to be more favorable than the ratio of 1 : 1 for the complexation. Meanwhile, latest lab-scale actual RO experiments successfully supported our computational prediction that 2 moles of xylitol are the most effective as the complexing agent for 1 mole of B(OH){sub 3} in aqueous solution.

  7. Mechanistic insights on ethanol dehydrogenation on Pd-Au model catalysts: a combined experimental and DFT study.

    Science.gov (United States)

    Evans, E J; Li, H; Yu, Wen-Yueh; Mullen, G M; Henkelman, G; Mullins, C Buddie

    2017-11-22

    In this study, we have combined ultra-high vacuum (UHV) experiments and density functional theory (DFT) calculations to investigate ethanol (EtOH) dehydrogenation on Pd-Au model catalysts. Using EtOH reactive molecular beam scattering (RMBS), EtOH temperature-programmed desorption (TPD), and DFT calculations, we show how different Pd ensemble sizes on Au(111) can affect the mechanism for EtOH dehydrogenation and H 2 production. The Au(111) surface with an initial coverage of 2 monolayers of Pd (2 ML Pd-Au) had the highest H 2 yield. However, the 1 ML Pd-Au catalyst showed the highest selectivity and stability, yielding appreciable amounts of only H 2 and acetaldehyde. Arrhenius plots of H 2 production confirm that the mechanisms for EtOH dehydrogenation differed between 1 and 2 ML Pd-Au, supporting the perceived difference in selectivity between the two surfaces. DFT calculations support this difference in mechanism, showing a dependence of the initial dehydrogenation selectivity of EtOH on the size of Pd ensemble. DFT binding energies and EtOH TPD confirm that EtOH has increasing surface affinity with increasing Pd ensemble size and Pd coverage, indicating that surfaces with more Pd are more likely to induce an EtOH reaction instead of desorb. Our theoretical results show that the synergistic influence of atomic ensemble and electronic effects on Pd/Au(111) can lead to different H 2 association energies and EtOH dehydrogenation capacities at different Pd ensembles. These results provide mechanistic insights into ethanol's dehydrogenation interactions with different sites on the Pd-Au surface and can potentially aid in bimetallic catalyst design for applications such as fuel cells.

  8. Metal-Free α-C(sp3–H Functionalized Oxidative Cyclization of Tertiary N,N-Diaryl Amino Alcohols: Theoretical Approach for Mechanistic Pathway

    Directory of Open Access Journals (Sweden)

    Zakir Ullah

    2017-03-01

    Full Text Available The mechanistic pathway of TEMPO/I2-mediated oxidative cyclization of N,N-diaryl amino alcohols 1 was investigated. Based on direct empirical experiments, three key intermediates (aminium radical cation 3, α-aminoalkyl radical 4, and iminium 5, four types of reactive species (radical TEMPO, cationic TEMPO, TEMPO-I, and iodo radical, and three types of pathways ((1 SET/PCET mechanism; (2 HAT/1,6-H transfer mechanism; (3 ionic mechanism were assumed. Under the assumption, nine free energy diagrams were acquired through density functional theory calculations. From the comparison of solution-phase free energy, some possible mechanisms were excluded, and then the chosen plausible mechanisms were concretized using the more stable intermediate 7.

  9. Aminoglycoside Concentrations Required for Synergy with Carbapenems against Pseudomonas aeruginosa Determined via Mechanistic Studies and Modeling.

    Science.gov (United States)

    Yadav, Rajbharan; Bulitta, Jürgen B; Schneider, Elena K; Shin, Beom Soo; Velkov, Tony; Nation, Roger L; Landersdorfer, Cornelia B

    2017-12-01

    This study aimed to systematically identify the aminoglycoside concentrations required for synergy with a carbapenem and characterize the permeabilizing effect of aminoglycosides on the outer membrane of Pseudomonas aeruginosa Monotherapies and combinations of four aminoglycosides and three carbapenems were studied for activity against P. aeruginosa strain AH298-GFP in 48-h static-concentration time-kill studies (SCTK) (inoculum: 10 7.6 CFU/ml). The outer membrane-permeabilizing effect of tobramycin alone and in combination with imipenem was characterized via electron microscopy, confocal imaging, and the nitrocefin assay. A mechanism-based model (MBM) was developed to simultaneously describe the time course of bacterial killing and prevention of regrowth by imipenem combined with each of the four aminoglycosides. Notably, 0.25 mg/liter of tobramycin, which was inactive in monotherapy, achieved synergy (i.e., ≥2-log 10 more killing than the most active monotherapy at 24 h) combined with imipenem. Electron micrographs, confocal image analyses, and the nitrocefin uptake data showed distinct outer membrane damage by tobramycin, which was more extensive for the combination with imipenem. The MBM indicated that aminoglycosides enhanced the imipenem target site concentration up to 4.27-fold. Tobramycin was the most potent aminoglycoside to permeabilize the outer membrane; tobramycin (0.216 mg/liter), gentamicin (0.739 mg/liter), amikacin (1.70 mg/liter), or streptomycin (5.19 mg/liter) was required for half-maximal permeabilization. In summary, our SCTK, mechanistic studies and MBM indicated that tobramycin was highly synergistic and displayed the maximum outer membrane disruption potential among the tested aminoglycosides. These findings support the optimization of highly promising antibiotic combination dosage regimens for critically ill patients. Copyright © 2017 American Society for Microbiology.

  10. A Mechanistic Study of Arsenic (III) Rejection by Reverse Osmosis and Nanofiltration Membranes

    Science.gov (United States)

    Suzuki, Tasuma

    2009-01-01

    Reverse osmosis/nanofiltration (RO/NF) membranes are capable to provide an effective barrier for a wide range of contaminants (including disinfection by-products precursors) in a single treatment step. However, solute rejection mechanisms by RO/NF membranes are not well understood. The lack of mechanistic information arises from experimental…

  11. Theoretical Studies of Hydrogen Storage Alloys.

    Energy Technology Data Exchange (ETDEWEB)

    Jonsson, Hannes

    2012-03-22

    Theoretical calculations were carried out to search for lightweight alloys that can be used to reversibly store hydrogen in mobile applications, such as automobiles. Our primary focus was on magnesium based alloys. While MgH{sub 2} is in many respects a promising hydrogen storage material, there are two serious problems which need to be solved in order to make it useful: (i) the binding energy of the hydrogen atoms in the hydride is too large, causing the release temperature to be too high, and (ii) the diffusion of hydrogen through the hydride is so slow that loading of hydrogen into the metal takes much too long. In the first year of the project, we found that the addition of ca. 15% of aluminum decreases the binding energy to the hydrogen to the target value of 0.25 eV which corresponds to release of 1 bar hydrogen gas at 100 degrees C. Also, the addition of ca. 15% of transition metal atoms, such as Ti or V, reduces the formation energy of interstitial H-atoms making the diffusion of H-atoms through the hydride more than ten orders of magnitude faster at room temperature. In the second year of the project, several calculations of alloys of magnesium with various other transition metals were carried out and systematic trends in stability, hydrogen binding energy and diffusivity established. Some calculations of ternary alloys and their hydrides were also carried out, for example of Mg{sub 6}AlTiH{sub 16}. It was found that the binding energy reduction due to the addition of aluminum and increased diffusivity due to the addition of a transition metal are both effective at the same time. This material would in principle work well for hydrogen storage but it is, unfortunately, unstable with respect to phase separation. A search was made for a ternary alloy of this type where both the alloy and the corresponding hydride are stable. Promising results were obtained by including Zn in the alloy.

  12. Theoretical & Experimental Studies of Elementary Particles

    Energy Technology Data Exchange (ETDEWEB)

    McFarland, Kevin [Univ. of Rochester, NY (United States)

    2012-10-04

    Abstract High energy physics has been one of the signature research programs at the University of Rochester for over 60 years. The group has made leading contributions to experimental discoveries at accelerators and in cosmic rays and has played major roles in developing the theoretical framework that gives us our ``standard model'' of fundamental interactions today. This award from the Department of Energy funded a major portion of that research for more than 20 years. During this time, highlights of the supported work included the discovery of the top quark at the Fermilab Tevatron, the completion of a broad program of physics measurements that verified the electroweak unified theory, the measurement of three generations of neutrino flavor oscillations, and the first observation of a ``Higgs like'' boson at the Large Hadron Collider. The work has resulted in more than 2000 publications over the period of the grant. The principal investigators supported on this grant have been recognized as leaders in the field of elementary particle physics by their peers through numerous awards and leadership positions. Most notable among them is the APS W.K.H. Panofsky Prize awarded to Arie Bodek in 2004, the J.J. Sakurai Prizes awarded to Susumu Okubo and C. Richard Hagen in 2005 and 2010, respectively, the Wigner medal awarded to Susumu Okubo in 2006, and five principal investigators (Das, Demina, McFarland, Orr, Tipton) who received Department of Energy Outstanding Junior Investigator awards during the period of this grant. The University of Rochester Department of Physics and Astronomy, which houses the research group, provides primary salary support for the faculty and has waived most tuition costs for graduate students during the period of this grant. The group also benefits significantly from technical support and infrastructure available at the University which supports the work. The research work of the group has provided educational opportunities

  13. A correlational study of students' theoretical and practical ...

    African Journals Online (AJOL)

    A correlational study of students' theoretical and practical examinations scores in computer applications courses in Bayero University Kano. ... Science World Journal ... In other words, for a student to do well in any of the courses, he/she must perform well in both the theoretical and practical aspects of the examination.

  14. THEORETICAL STUDY OF THE CATALYTIC DESULFURIZATION ...

    African Journals Online (AJOL)

    a

    In the present study we have submitted the dihydrothiiren (Figure 1b), the methylthiiren (Figure 1c) and the methyldihydrothiiren (Figure 1d) to the same process before proceeding to their desulfurization behaviour in order to propose the sulfur atom elimination mechanism while studying methyl group influence on the thiiren ...

  15. Theoretical Study of Semiconductor Laser under Modulation

    Science.gov (United States)

    Boukari, O.; Hassine, L.; Dherbecourt, P.; Latry, O.; Ketata, M.; Bouchriha, H.

    2007-09-01

    In this paper we present a description of the chirp induced in a direct modulated DFB laser. Our study is follows two different approaches. The first approach is based on a resolution of the rate equations of laser; the second, on a simulation of a heterodyne system with the Optisystem software. This study enables us to visualize the chirp in the RF field. We also characterize it according to the injection current i(t) parameters, such as the amplitude and the frequency of the modulation. The aim of our study is to choose the appropriate values of these parameters, in order to use the direct modulated DFB laser as an optical tunable source for Coherent Optical Frequency Domain Reflectometry technique (C-OFDR). We demonstrate that the optical frequency of these lasers can be controlled via the injection current i(t) and it can be linearly swept (chirped) over some tens of gigahertz.

  16. Theoretical studies on energetic materials bearing pentaflurosulphyl ...

    Indian Academy of Sciences (India)

    Heats of formation (HOF) for a series of energetic materials containing SF5 group were studied by density functional theory. Results show that HOFs increase with the augmention of field effects of substituted groups. Addition of furazan or furoxan ring increases HOF of the energetic materials. All the SF5-containing ...

  17. A Theoretical Study of Leading Edge Noise

    Science.gov (United States)

    2008-05-01

    measurements of the noise radiated from a number of different airfoils made as -part of a companion study at Virginia lech . It was concluded that the...giving, at a distance r from the blade, and at an angle 9 to the direction of the unsteady loading, the sound spectrum as Spp(co)=( cocos &4itrcc) 2SLL

  18. Theoretical studies on the conformations of selenamides

    Indian Academy of Sciences (India)

    Unknown

    selenols, selenones, selenoamides, selenonium ylides, selenonium imides etc. have been studied in comparison with organosulphur compounds 1. Compounds containing Se–N bonds are rare. Flemmang et al 2 have reported the generation of nitrile N-selenides in the gas phase, which have Se–N ionic interactions.

  19. A Theoretical Study of Landing Mat Behavior

    Science.gov (United States)

    1969-07-01

    Waterways Experiment Station (WES) under Contract DACA 39-67-C-oohh, during the period July 1967 to March 1969. The study was conducted as a part of the...required functional relationship. If the functional relationship was to apply, of necessity , it had to satisfy each set of- data. Thus in order to

  20. Theoretical studies on energetic materials bearing pentaflurosulphyl

    Indian Academy of Sciences (India)

    Heats of formation (HOF) for a series of energetic materials containing SF5 group were studied by density functional theory. Results show that HOFs increase with the augmention of field effects of substituted groups. Addition of furazan or furoxan ring increases HOF of the energetic materials. All the SF5-containing ...

  1. Global Leadership Study: A Theoretical Framework

    Science.gov (United States)

    Perkins, Anne W.

    2009-01-01

    Traditional leadership theory and research courses do not adequately prepare students for cross-cultural leadership. This article notes six premises of Western theories and demonstrates the limitations of these premises in non-Western settings. A framework for the study of cross-cultural leadership, The Global Leadership-Learning Pyramid, is…

  2. Mechanistic studies on the OH-initiated atmospheric oxidation of selected aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Nehr, Sascha

    2012-07-01

    Benzene, toluene, the xylenes, and the trimethylbenzenes are among the most abundant aromatic trace constituents of the atmosphere mainly originating from anthropogenic sources. The OH-initiated atmospheric photo-oxidation of aromatic hydrocarbons is the predominant removal process resulting in the formation of O{sub 3} and secondary organic aerosol. Therefore, aromatics are important trace constituents regarding air pollution in urban environments. Our understanding of aromatic photo-oxidation processes is far from being complete. This work presents novel approaches for the investigation of OH-initiated atmospheric degradation mechanisms of aromatic hydrocarbons. Firstly, pulsed kinetic studies were performed to investigate the prompt HO{sub 2} formation from OH+ aromatic hydrocarbon reactions under ambient conditions. For these studies, the existing OH reactivity instrument, based on the flash photolysis/laser-induced fluorescence (FP/LIF) technique, was extended to the detection of HO{sub 2} radicals. The experimental design allows for the determination of HO{sub 2} formation yields and kinetics. Results of the pulsed kinetic experiments complement previous product studies and help to reduce uncertainties regarding the primary oxidation steps. Secondly, experiments with aromatic hydrocarbons were performed under atmospheric conditions in the outdoor atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction chamber) located at Forschungszentrum Juelich. The experiments were aimed at the evaluation of up-to-date aromatic degradation schemes of the Master Chemical Mechanism (MCMv3.2). The unique combination of analytical instruments operated at SAPHIR allows for a detailed investigation of HO{sub x} and NO{sub x} budgets and for the determination of primary phenolic oxidation product yields. MCMv3.2 deficiencies were identified and most likely originate from shortcomings in the mechanistic representation of ring

  3. Theoretical and experimental studies on the foundation theoretical and experimental studies on the foundation of mesomechanics

    Science.gov (United States)

    Chudnovsky, A.; Wu, S.

    1992-06-01

    The report summarizes a closely coupled experimental and theoretical investigation of various stages of Fracture Process: (1) accumulation of 'damage' on submicroscopical and microscopical scales leading to crack initiation; (2) slow (subcritical) crack growth and an evolution of the damage zone; (3) transition to dynamic crack growth and the catastrophic failure. The experimental part of the program is focused on the observation and quantitative characterization of damage preceding and accompanying crack initiation and growth. A special experimental setup for studying the fracture process under variable stress field is reported in Chapter 2. A leading role of crack-damage interaction in fracture process is well documented. A new formalism for solution of crack-microcrack array interaction problem and its successful implementation in the evaluation of crack layer driving forces is presented in Chapter 3. A new model of the process zone, which generalizes the well-known Dagdale-Barenblatt model is presented in Chapter 4. A new measure for material toughness and the prediction of R-curve behavior illustrate the practical application of our model. Experimental examinations of our model under various test conditions are reported in Chapters 4, 5 and 6. The development of the constitutive equations for Crack Layer evolution and their experimental examinations under stress relaxation, fatigue and creep conditions are reported in Chapters 5 and 6. An accelerated test procedure and the formulation of crack layer instability criteria as a substitution for the conventional fracture toughness parameters are also discussed in Chapter 6.

  4. Kinetic and mechanistic study of the atmospheric reaction of MBO331 with Cl atoms

    Science.gov (United States)

    Rodríguez, Diana; Rodríguez, Ana; Garzón, Andrés; Granadino-Roldán, José M.; Soto, Amparo; Aranda, Alfonso; Notario, Alberto

    2012-12-01

    The present work deals with the reaction of 3-methyl-3-buten-1-ol (MBO331) with Cl atoms, which has been investigated by gas chromatography with flame ionization detection (GC-FID) at atmospheric pressure in N2 or air, using the relative rate technique. The rate constant reaction at 298 ± 1 K was found to be (5.01 ± 0.70) × 10-10 cm3 molecule-1 s-1, using cyclohexane, octane and 1-butene as a reference compounds. The temperature dependence for the reaction was studied within the 298-333 K range. Additionally, a product identification under atmospheric conditions has been performed for the first time by GC-MS, with 3-methyl-3-butenal, methacrolein and chloroacetone being observed as degradation products. A theoretical study on the reaction at the QCISD(T)/6-311G**//MP2/6-311G** level was also carried out to obtain more information on the mechanism. From the theoretical study it can be predicted that Cl addition to the double bond proceeds through lower energy barriers than H-abstraction pathways and therefore is energetically favoured. Finally, atmospheric implications of the results obtained are discussed.

  5. Theoretical and experimental studies of thermolysin inhibition

    OpenAIRE

    Wuxiuer, Yimingjiang

    2008-01-01

    Zinc-metalloproteinases play a key role in the biosythesis and metabolism of different bioactive peptides. As a member of zinc-metalloproteinases, thermolysin has served as a model system to study the inhibition mechanism of other metalloproteinases. Inhibitors of thermolysin have considerable potential as therapeutic agents. In the present master thesis, docking calculations were performed and reported for 25 potent non-peptidal thermolysin inhibitors retrieved from literatures. Docking sof...

  6. THEORETICAL CONCEPT OF JOB SATISFACTION - A STUDY

    OpenAIRE

    Dr. A. Thangaswamy; D.Thiyagaraj

    2017-01-01

    Job satisfaction is one of the important factors that have drawn attention of the organization as well as academicians. In view of the rising competition as a result of globalisation, managers have placed great importance on the construct of job satisfaction. This may be due to the findings of many studies that job satisfaction is a significant determinant of organizational commitment. Highly satisfied employees will exert extra effort and contribute positively to the effectiveness and effici...

  7. Theoretical and experimental studies of elementary particles

    International Nuclear Information System (INIS)

    Bodek, A.; Ferbel, T.; Melissinos, A.C.; Olsen, S.L.; Slattery, P.; Tipton, P.; Das, A.; Hagen, C.R.; Rajeev, S.G.; Okubo, S.

    1991-01-01

    This report discusses: Fixed target experimentation at Fermilab; the D-zero collider experiment at Fermilab; deep inelastic lepton nucleon scattering; non-accelerator experiments and non-linear QED; the AMY experiment at TRISTAN and other activities at KEK; the collider detector at Fermilab; laser switched linac; preparations for experiments at the SSC; search for massive stable particles; and the Advanced Study Institute on techniques and concepts of high energy physics

  8. The mechanistic causes of peripheral intravenous catheter failure based on a parametric computational study

    OpenAIRE

    Piper, Russell; Carr, Peter J.; Kelsey, Lachlan J.; Bulmer, Andrew C.; Keogh, Samantha; Doyle, Barry J.

    2018-01-01

    Peripheral intravenous catheters (PIVCs) are the most commonly used invasive medical device, yet up to 50% fail. Many pathways to failure are mechanistic and related to fluid mechanics, thus can be investigated using computational fluid dynamics (CFD). Here we used CFD to investigate typical PIVC parameters (infusion rate, catheter size, insertion angle and tip position) and report the hemodynamic environment (wall shear stress (WSS), blood damage, particle residence time and venous stasis vo...

  9. Kinetics and mechanistic study of the gas-phase reaction of ozone with methylbutenol

    Science.gov (United States)

    Klawatsch-Carrasco, N.; Doussin, J. F.; Rea, G.; Wenger, J.; Carlier, P.

    2003-04-01

    Biogenic volatile organic compounds (BVOCs) account for around 90% of hydrocarbon emissions into the Earth's atmosphere ([1], [2]). Several thousand different BVOCs have been identified, the most well known being unsaturated hydrocarbons. However, over the last ten years an increasing number of oxygenated BVOCs, such as methylbutenol (MBO), have also been detected in field measurement campaigns and plant emission studies ([3], [4]). In order to determine the environmental impact of BVOCs, a thorough knowledge of the rates and mechanisms for their atmospheric degradation is required. The major atmospheric degradation processes for BVOCs are gas-phase reaction with hydroxyl radicals (OH), nitrate radicals (NO_3) and ozone (O_3). These reactions produce oxidised hydrocarbons, ozone and secondary organic aerosol and, as a result, exert a strong influence on the chemical composition of the atmosphere. Very few studies are available concerning the reactivity of MBO. To extend the available database on the atmospheric chemistry of biogenic compounds, the reaction of O_3 with MBO at 296(±2) K has been investigated in atmospheric simulation chambers at LISA in Créteil (France) and CRAC in Cork (Ireland), using complementary techniques such as FTIR spectroscopy, PFBHA derivatization with GC-MS detection and a particle sizer and counter. The rate constant for the reaction was determined using an absolute rate technique, yielding a value of (8.3±0.9)× 10-18 cm^3 molecule-1s-1. Mechanistic studies of the reaction lead to the following observations: a primary formation of only three carbonyl compounds, formaldehyde (yield=0.40±0.03), acetone (yield=0.27±0.02) and 2-methyl-2-hydroxy-propanal. In addition, there is a noticeable formation of aerosols at the very beginning of the reaction that seemed to depend on the relative humidity. References: [1] Wayne, R. P. (2000). 3rd edition. Oxford university press inc. Edition. [2] Finlayson-Pitts, B. and Pitts Jr, J. N. ( 2000

  10. Theoretical study of HBeO

    International Nuclear Information System (INIS)

    Zaidi, A.; Lahmar, S.; Lakhdar, Z. Ben; Rosmus, P.; Chambaud, G.

    2006-01-01

    Using multi-reference configuration interaction (MRCI) and coupled-cluster RCCSD(T) ab initio methods three-dimensional potential energy surfaces (PES) have been generated for the X 2 Π and A 2 Σ + states of HBeO. The two components of the X 2 Π electronic ground state form a linear-linear Renner-Teller pair. The HBeO structure is calculated to lie 11,917cm -1 above the BeOH isomer. A barrier on the A' PES of 10,920cm -1 relative to the HBeO minimum does not permit a spontaneous rearrangement. From variational Renner-Teller calculations the rovibronic levels of the X 2 Π state of the HBeO radical have been evaluated for J=12andJ=32. The eigenstates can not be unequivocally assigned by harmonic quantum numbers due to anharmonic resonances involving all three vibrational modes. In contrast with previous studies A 2 Σ + state is calculated above the X 2 Π (T e =9389cm -1 ). For some higher doublet and quartet states of BeOH and HBeO, MRCI vertical electronic transition energies are reported

  11. Theoretical studies of homogeneous catalysts mimicking nitrogenase.

    Science.gov (United States)

    Sgrignani, Jacopo; Franco, Duvan; Magistrato, Alessandra

    2011-01-10

    The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen 'fixation' via an iron molybdenum cofactor (FeMo-co) under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N₂ to various degrees. However, to date Mo(N₂)(HIPTN)₃N with (HIPTN)₃N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N₂. These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds.

  12. Theoretical Studies of Homogeneous Catalysts Mimicking Nitrogenase

    Directory of Open Access Journals (Sweden)

    Alessandra Magistrato

    2011-01-01

    Full Text Available The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen ‘fixation’ via an iron molybdenum cofactor (FeMo-co under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N2 to various degrees. However, to date Mo(N2(HIPTN3N with (HIPTN3N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N2. These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds.

  13. Theoretical and Experimental Studies in Accelerator Physics

    Energy Technology Data Exchange (ETDEWEB)

    Rosenzweig, James [Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy

    2017-03-08

    . We note also that PBPL graduates remain as close elaborators for the program after leaving UCLA. The UCLA PBPL program is a foremost developer of on-campus facilities, such as the Neptune and Pegasus Laboratories, providing a uniquely strong environment for student-based research. In addition, the PBPL is a strong user of off-campus national lab facilities, such as SLAC FACET and NLCTA, and the BNL ATF. UCLA has also vigorously participated in the development of these facilities. The dual emphases on off- and on-campus opportunities permit the PBPL to address in an agile way a wide selection of cutting-edge research topics. The topics embraced by this proposal illustrate this program aspect well. These include: GV/m dielectric wakefield acceleration/coherent Cerenkov radiation experiments at FACET (E-201) and the ATF; synergistic laser-excited dielectric accelerator and light source development; plasma wakefield (PWFA) experiments on “Trojan horse” ionization injection (FACET E-210), quasi-nonlinear PWFA at BNL and the production at Neptune high transformer ratio plasma wakes; the inauguration of a new type of RF photoinjector termed “hybrid” at UCLA, and application to PWFA; space-charge dominated beam and cathode/near cathode physics; the study of advanced IFEL systems, for very high energy gain and utilization of novel OAM modes; the physcis of inverse Compton scattering (ICS), with applications to e+ production and γγ colliders; electron diffraction; and advanced beam diagnostics using coherent imaging techniques. These subjects are addressed under the leadership of PBPL director Prof. James Rosenzweig in Task A, and Prof. Pietro Musumeci in Task J, which was initiated following his OHEP Outstanding Junior Investigator award.

  14. Phenomenological description of selected elementary chemical reaction mechanisms: An information-theoretic study

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel, R.O., E-mail: esquivel@xanum.uam.m [Departamento de Quimica, Universidad Autonoma Metropolitana, 09340 Mexico D.F. (Mexico); Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, 18071-Granada (Spain); Instituto Carlos I de Fisica Teorica y Computacional, Universidad de Granada, 18071-Granada (Spain); Flores-Gallegos, N.; Iuga, C.; Carrera, E.M. [Departamento de Quimica, Universidad Autonoma Metropolitana, 09340 Mexico D.F. (Mexico); Angulo, J.C. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, 18071-Granada (Spain); Instituto Carlos I de Fisica Teorica y Computacional, Universidad de Granada, 18071-Granada (Spain); Antolin, J. [Departamento de Fisica Aplicada, EUITIZ, Universidad de Zaragoza, 50018-Zaragoza (Spain); Instituto Carlos I de Fisica Teorica y Computacional, Universidad de Granada, 18071-Granada (Spain)

    2010-02-01

    The information-theoretic description of the course of two elementary chemical reactions allows a phenomenological description of the chemical course of the hydrogenic abstraction and the S{sub N}2 identity reactions by use of Shannon entropic measures in position and momentum spaces. The analyses reveal their synchronous/asynchronous mechanistic behavior.

  15. Phenomenological description of selected elementary chemical reaction mechanisms: An information-theoretic study

    International Nuclear Information System (INIS)

    Esquivel, R.O.; Flores-Gallegos, N.; Iuga, C.; Carrera, E.M.; Angulo, J.C.; Antolin, J.

    2010-01-01

    The information-theoretic description of the course of two elementary chemical reactions allows a phenomenological description of the chemical course of the hydrogenic abstraction and the S N 2 identity reactions by use of Shannon entropic measures in position and momentum spaces. The analyses reveal their synchronous/asynchronous mechanistic behavior.

  16. Theoretical Studies of Elementary Hydrocarbon Species and Their Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Wesley D. [Univ. of Georgia, Athens, GA (United States). Dept. of Chemistry. Center for Computational Quantum Chemistry; Schaefer, III, Henry F. [Univ. of Georgia, Athens, GA (United States). Dept. of Chemistry. Center for Computational Quantum Chemistry

    2015-11-14

    This is the final report of the theoretical studies of elementary hydrocarbon species and their reactions. Part A has a bibliography of publications supported by DOE from 2010 to 2016 and Part B goes into recent research highlights.

  17. Experimental and Theoretical Studies in Hydrogen-Bonding Organocatalysis

    Directory of Open Access Journals (Sweden)

    Matej Žabka

    2015-08-01

    Full Text Available Chiral thioureas and squaramides are among the most prominent hydrogen-bond bifunctional organocatalysts now extensively used for various transformations, including aldol, Michael, Mannich and Diels-Alder reactions. More importantly, the experimental and computational study of the mode of activation has begun to attract considerable attention. Various experimental, spectroscopic and calculation methods are now frequently used, often as an integrated approach, to establish the reaction mechanism, the mode of activation or explain the stereochemical outcome of the reaction. This article comprises several case studies, sorted according to the method used in their study. The aim of this review is to give the investigators an overview of the methods currently utilized for mechanistic investigations in hydrogen-bonding organocatalysis.

  18. Randomized controlled trials - mechanistic studies of testosterone and the cardiovascular system.

    Science.gov (United States)

    Jones, T Hugh; Kelly, Daniel M

    2018-02-09

    Testosterone deficiency is common in men with cardiovascular disease (CVD), and randomized placebo-controlled trials (RCTs) have reported beneficial effects of testosterone therapy on exercise-induced cardiac ischemia in chronic stable angina, functional exercise capacity, maximum oxygen consumption during exercise (VO 2max ) and muscle strength in chronic heart failure (CHF), shortening of the Q-T interval, and improvement of some cardiovascular risk factors. Testosterone deficiency is associated with an adverse CV risk profile and mortality. Clinical and scientific studies have provided mechanistic evidence to support and explain the findings of the RCTs. Testosterone is a rapid-onset arterial vasodilator within the coronary circulation and other vascular beds including the pulmonary vasculature and can reduce the overall peripheral systemic vascular resistance. Evidence has demonstrated that testosterone mediates this effect on vascular reactivity through calcium channel blockade (L-calcium channel) and stimulates potassium channel opening by direct nongenomic mechanisms. Testosterone also stimulates repolarization of cardiac myocytes by stimulating the ultra-rapid potassium channel-operated current. Testosterone improves cardiac output, functional exercise capacity, VO 2max and vagally mediated arterial baroreceptor cardiac reflex sensitivity in CHF, and other mechanisms. Independent of the benefit of testosterone on cardiac function, testosterone substitution may also increase skeletal muscle glucose metabolism and enhance muscular strength, both factors that could contribute to the improvement in functional exercise capacity may include improved glucose metabolism and muscle strength. Testosterone improves metabolic CV risk factors including body composition, insulin resistance, and hypercholesterolemia by improving both glucose utilization and lipid metabolism by a combination of genomic and nongenomic actions of glucose uptake and utilization expression of

  19. Randomized controlled trials – mechanistic studies of testosterone and the cardiovascular system

    Directory of Open Access Journals (Sweden)

    T Hugh Jones

    2018-01-01

    Full Text Available Testosterone deficiency is common in men with cardiovascular disease (CVD, and randomized placebo-controlled trials (RCTs have reported beneficial effects of testosterone therapy on exercise-induced cardiac ischemia in chronic stable angina, functional exercise capacity, maximum oxygen consumption during exercise (VO2max and muscle strength in chronic heart failure (CHF, shortening of the Q-T interval, and improvement of some cardiovascular risk factors. Testosterone deficiency is associated with an adverse CV risk profile and mortality. Clinical and scientific studies have provided mechanistic evidence to support and explain the findings of the RCTs. Testosterone is a rapid-onset arterial vasodilator within the coronary circulation and other vascular beds including the pulmonary vasculature and can reduce the overall peripheral systemic vascular resistance. Evidence has demonstrated that testosterone mediates this effect on vascular reactivity through calcium channel blockade (L-calcium channel and stimulates potassium channel opening by direct nongenomic mechanisms. Testosterone also stimulates repolarization of cardiac myocytes by stimulating the ultra-rapid potassium channel-operated current. Testosterone improves cardiac output, functional exercise capacity, VO2maxand vagally mediated arterial baroreceptor cardiac reflex sensitivity in CHF, and other mechanisms. Independent of the benefit of testosterone on cardiac function, testosterone substitution may also increase skeletal muscle glucose metabolism and enhance muscular strength, both factors that could contribute to the improvement in functional exercise capacity may include improved glucose metabolism and muscle strength. Testosterone improves metabolic CV risk factors including body composition, insulin resistance, and hypercholesterolemia by improving both glucose utilization and lipid metabolism by a combination of genomic and nongenomic actions of glucose uptake and utilization

  20. Theoretical study of nuclear physics with strangeness at Nankai University

    International Nuclear Information System (INIS)

    Ning Pingzhi

    2007-01-01

    Theoretical study of nuclear physics with strangeness from the nuclear physics group at Nankai university is briefly introduced. Theoretical calculations on hyperon mean free paths in nuclear medium have been done. The other 4 topics in the area of strangeness nuclear physics are the effect of different baryon impurities in nucleus, the heavy flavored baryon hypernuclei, the eta-mesons in nuclear matter and the properties of kaonic nuclei. (authors)

  1. Hydrolysis of Sulfur Dioxide in Small Clusters of Sulfuric Acid: Mechanistic and Kinetic Study.

    Science.gov (United States)

    Liu, Jingjing; Fang, Sheng; Wang, Zhixiu; Yi, Wencai; Tao, Fu-Ming; Liu, Jing-Yao

    2015-11-17

    The deposition and hydrolysis reaction of SO2 + H2O in small clusters of sulfuric acid and water are studied by theoretical calculations of the molecular clusters SO2-(H2SO4)n-(H2O)m (m = 1,2; n = 1,2). Sulfuric acid exhibits a dramatic catalytic effect on the hydrolysis reaction of SO2 as it lowers the energy barrier by over 20 kcal/mol. The reaction with monohydrated sulfuric acid (SO2 + H2O + H2SO4 - H2O) has the lowest energy barrier of 3.83 kcal/mol, in which the cluster H2SO4-(H2O)2 forms initially at the entrance channel. The energy barriers for the three hydrolysis reactions are in the order SO2 + (H2SO4)-H2O > SO2 + (H2SO4)2-H2O > SO2 + H2SO4-H2O. Furthermore, sulfurous acid is more strongly bonded to the hydrated sulfuric acid (or dimer) clusters than the corresponding reactant (monohydrated SO2). Consequently, sulfuric acid promotes the hydrolysis of SO2 both kinetically and thermodynamically. Kinetics simulations have been performed to study the importance of these reactions in the reduction of atmospheric SO2. The results will give a new insight on how the pre-existing aerosols catalyze the hydrolysis of SO2, leading to the formation and growth of new particles.

  2. STUDY OF THE SEMI-THEORETICAL RELATION OF THE ...

    African Journals Online (AJOL)

    ABSTRACT. This study has for objective to study the theoretical relation of the hydraulic jump by sill, evolving in an U-shaped channel, with a rough bed. Functional relations, in non- dimensional form, relating the jump characteristics, seeming the effect of the bed's roughness, are obtained. A comparative study with the ...

  3. Mechanistic studies of catalytic hydrogenation: gas tritiation and deuteration of 2-acetamidoacrylic acid and alpha-acetamidocinnamic acid

    International Nuclear Information System (INIS)

    Tang, Y.S.; Morimoto, H.; Un, S.; Rapoport, H.

    1986-01-01

    The difference of labeling in heterogeneous catalytic gas tritiations of 2-acetamidocinnamic acid and 2-acetamidoacrylic acid is demonstrated by 3 H NMR spectroscopy. The nonequivalent addition of tritium to the double bond of 2-acetamidoacrylic acid is due to simultaneous hydrogen-tritium exchange during adsorption on the catalyst surface. A new mechanistic interpretation has been proposed to explain the behavior of this substrate. These conclusions were substantiated by mass spectrometry results obtained using D 2 and deuterated solvents. Steric effects on vinylic exchange studied by GLRC were also reported. 2 refs.; 6 figs.; 3 tabs

  4. Optical graphene quantum dots gas sensors: Theoretical study

    Science.gov (United States)

    Raeyani, D.; Shojaei, S.; Ahmadi-Kandjani, S.

    2018-02-01

    In this work, we theoretically studied the changes of graphene quantum dots (GQD) absorption spectra under the influence of different gases to indicate optical gas sensing features of GQDs. The adsorption of gas molecules such as CO2, N2 and Ar on GQDs have been theoretically investigated through time-dependent density functional theory (TDDFT) calculations. Our study revealed that UV-Vis absorption spectrum of GQDs in the presence of CO2 undergoes considerable changes than that of N2 and Ar. The shift of maximum absorption wavelength for adsorption of CO2, N2 and Ar in same distance from GQD in addition to density of state (DOS) and orbital analyses have been obtained. To verify our theoretical results, comparison with experimental study has been done and good agreement has been observed. Comparing with electrical property of GQD, optical properties showed an efficient tool to be implemented in gas adsorption and paves the way towards GQD optical gas sensors.

  5. Mechanistic and kinetic study on the catalytic hydrolysis of COS in small clusters of sulfuric acid.

    Science.gov (United States)

    Li, Kai; Song, Xin; Zhu, Tingting; Wang, Chi; Sun, Xin; Ning, Ping; Tang, Lihong

    2018-01-01

    The catalytic hydrolysis of carbonyl sulfide (COS) and the effect of small clusters of H 2 O and H 2 SO 4 have been studied by theoretical calculations. The addition of H 2 SO 4 could increase the enthalpy change (ΔHCOS + H 2 SO 4 -H 2 O) reaction has the lowest energy barrier of 29.97 kcal/mol. Although an excess addition of H 2 O and H 2 SO 4 increases the energy barrier, decreases the catalytic hydrolysis, which is consistent with experimental observations. The order of the energy barriers for the three reactions from low to high are as follows: COS + H 2 SO 4 -H 2 O COS + H 2 O + H 2 SO 4 -H 2 O COS + H 2 O+(H 2 SO 4 ) 2 . Kinetic simulations show that the addition of H 2 SO 4 can increase the reaction rate constants. Consequently, adding an appropriate amount of sulfuric acid promotes the catalytic hydrolysis of COS both kinetically and thermodynamically. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Mechanistic and kinetic studies on the OH-initiated atmospheric oxidation of fluoranthene

    Energy Technology Data Exchange (ETDEWEB)

    Dang, Juan; Shi, Xiangli; Zhang, Qingzhu, E-mail: zqz@sdu.edu.cn; Hu, Jingtian; Chen, Jianmin; Wang, Wenxing

    2014-08-15

    The atmospheric oxidation of polycyclic aromatic hydrocarbons (PAHs) can generate toxic derivatives which contribute to the carcinogenic potential of particulate organic matter. In this work, the mechanism of the OH-initiated atmospheric oxidation of fluoranthene (Flu) was investigated by using high-accuracy molecular orbital calculations. All of the possible oxidation pathways were discussed, and the theoretical results were compared with the available experimental observation. The rate constants of the crucial elementary reactions were evaluated by the Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The main oxidation products are a range of ring-retaining and ring-opening chemicals containing fluoranthols, fluoranthones, fluoranthenequinones, nitro-fluoranthenes, dialdehydes and epoxides. The overall rate constant of the OH addition reaction is 1.72 × 10{sup −11} cm{sup 3} molecule{sup −1} s{sup −1} at 298 K and 1 atm. The atmospheric lifetime of Flu determined by OH radicals is about 0.69 days. This work provides a comprehensive investigation of the OH-initiated oxidation of Flu and should help to clarify its atmospheric conversion. - Highlights: • We studied a comprehensive mechanism of OH-initiated oxidation of fluoranthene. • We reported the formation pathways of fluoranthone, fluoranthenequinone and epoxide. • The rate constants of the crucial elementary steps were evaluated.

  7. Theoretical study on β-aminoacroleine; Density functional theory ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 124; Issue 3. Theoretical study on β-aminoacroleine; Density functional theory, atoms in molecules theory and natural bond orbitals studies. Heidar Raissi Mehdi Yoosefian Effat Moshfeghi Farzaneh Farzad. Volume 124 Issue 3 May 2012 pp 731-739 ...

  8. Theoretical studies on proton transfer reaction of 3 (5)-substituted ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 1. Theoretical studies on proton transfer reaction of 3(5)-substituted pyrazoles ... Abstract. The inter and intra molecular proton transfer reactions of a series of pyrazole derivatives have been studied by using density functional theory (DFT) andMP2 methods ...

  9. Theoretical study (ab initio and DFT methods) on acidic dissociation ...

    African Journals Online (AJOL)

    Analytical measurement of materials requires exact knowledge of their acid dissociation constant (pKa) values. In recent years, quantum mechanical calculations have been extensively used to study of acidities in the aqueous solutions and the results were compared with the experimental values. In this study, a theoretical ...

  10. Diffusion in liquids a theoretical and experimental study

    CERN Document Server

    Tyrrell, H J V

    1984-01-01

    Diffusion in Liquids: A Theoretical and Experimental Study aims to discuss the principles, applications, and advances in the field of diffusion, thermal diffusion, and thermal conduction in liquid systems. The book covers topics such as the principles of non-equilibrium thermodynamics; diffusion in binary and multicompetent systems; and experimental methods of studying diffusion processes in liquids. Also covered in the book are topics such as the theoretical interpretations of diffusion coefficients; hydrodynamic and kinetic theories; and diffusion in electrolyte systems. The text is recommen

  11. Cross-study and cross-omics comparisons of three nephrotoxic compounds reveal mechanistic insights and new candidate biomarkers

    International Nuclear Information System (INIS)

    Matheis, Katja A.; Com, Emmanuelle; Gautier, Jean-Charles; Guerreiro, Nelson; Brandenburg, Arnd; Gmuender, Hans; Sposny, Alexandra; Hewitt, Philip; Amberg, Alexander; Boernsen, Olaf; Riefke, Bjoern; Hoffmann, Dana; Mally, Angela; Kalkuhl, Arno; Suter, Laura; Dieterle, Frank; Staedtler, Frank

    2011-01-01

    The European InnoMed-PredTox project was a collaborative effort between 15 pharmaceutical companies, 2 small and mid-sized enterprises, and 3 universities with the goal of delivering deeper insights into the molecular mechanisms of kidney and liver toxicity and to identify mechanism-linked diagnostic or prognostic safety biomarker candidates by combining conventional toxicological parameters with 'omics' data. Mechanistic toxicity studies with 16 different compounds, 2 dose levels, and 3 time points were performed in male Crl: WI(Han) rats. Three of the 16 investigated compounds, BI-3 (FP007SE), Gentamicin (FP009SF), and IMM125 (FP013NO), induced kidney proximal tubule damage (PTD). In addition to histopathology and clinical chemistry, transcriptomics microarray and proteomics 2D-DIGE analysis were performed. Data from the three PTD studies were combined for a cross-study and cross-omics meta-analysis of the target organ. The mechanistic interpretation of kidney PTD-associated deregulated transcripts revealed, in addition to previously described kidney damage transcript biomarkers such as KIM-1, CLU and TIMP-1, a number of additional deregulated pathways congruent with histopathology observations on a single animal basis, including a specific effect on the complement system. The identification of new, more specific biomarker candidates for PTD was most successful when transcriptomics data were used. Combining transcriptomics data with proteomics data added extra value.

  12. Peroxyoxalate-chemiluminescence of Tinopal CBS as a commercially important optical brightener: Mechanistic study and quantification

    Energy Technology Data Exchange (ETDEWEB)

    Shamsipur, Mojtaba, E-mail: mshamsipur@yahoo.co [Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Zargoosh, Kiomars [Department of Chemistry, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Javad Chaichi, Mohammad; Tajbakhsh, Mahmood; Parach, Ali [Department of Chemistry, Mazandaran University, Babolsar (Iran, Islamic Republic of)

    2010-05-15

    The peroxyoxalate-chemiluminescence arising from reaction of bis(2,4,6-trichlorophenyl)oxalate with hydrogen peroxide in the presence of a brightener Tinopal CBS (2,2'-((1,1'-biphenyl)-4,4'-diyldi-2.1-ethenediyl)bisbenzene sulfonic acid, disodium salt) has been studied. The relationship between the chemiluminescence intensity and concentrations of bis(2,4,6-trichlorophenyl)oxalate, sodium salicylate (as catalyst), hydrogen peroxide and Tinopal CBS is reported. The chemiluminescence parameters including intensity at maximum chemiluminescence, time at maximum intensity, total light yield, theoretical maximum level of intensity and pseudo-first-order rate constants for the rise and fall of the chemiluminescence burst (k{sub r} and k{sub f}) were evaluated from computer fitting of the resulting intensity-time plots. The activation parameters E{sub a}, DELTAH, DELTAS and DELTAG for the rise and fall steps were evaluated from the temperature dependence of k{sub r} and k{sub f} values. The results were discussed in terms of chemically initiated electron transfer between a reactive intermediate and Tinopal CBS as fluorescence activator. A possible mechanism involving dioxetanone derivatives as intermediates is proposed. Since there is a linear relationship between reciprocal of chemiluminescence intensity and reciprocal of fluorescer concentration, an analytical method based on partial least squares (PLS) regression was proposed for quantitative determination of Tinopal CBS. Satisfactory results were obtained with percent relative prediction error (RPE%) of 2.52 and detection limit of 2.7x10{sup -5} M.

  13. Theoretical studies of the spin-Hamiltonian parameters for the ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 70; Issue 4. Theoretical studies of the spin-Hamiltonian parameters for the orthorhombic Pr4+ centers in Sr2CeO4 ... Author Affiliations. Wen-Lin Feng1. Department of Applied Physics, Chongqing Institute of Technology, Chongqing 400050, People Republic of China ...

  14. A combined electrochemical and theoretical study of pyridine-based ...

    Indian Academy of Sciences (India)

    PARUL DOHARE

    2018-02-01

    Feb 1, 2018 ... mild steel (MS) in 1 M hydrochloric acid solution using electrochemical experiments and theoretical study. The results ... Quantum chemical calculations and Monte Carlo simulations were used to understand metal-inhibitor interaction and ...... steel in Bacil- lus sp. inoculated artificial seawater Corros. Sci.

  15. Generation, structure and reactivity of arynes: A theoretical study

    Indian Academy of Sciences (India)

    Generation, structure and reactivity of arynes: A theoretical study. PETER G S DKHAR and R H DUNCAN LYNGDOH*. Department of Chemistry, North-Eastern Hill University, Bijni Complex,. Shillong 793 003, India. MS received 20 September 1999; revised 14 February 2000. Abstract. The semiempirical AM1 SCF-MO ...

  16. Trends In The Study Of Language Variation:Theoretical And ...

    African Journals Online (AJOL)

    Register study, stylistics, sociolinguistics, discourse analysis, and English for specific purposes all deal with language variation. This can be gleaned from several perspectives. In this paper, however, we have tried to look at the issue of variation from two main perspectives namely: the theoretical and the taxonomic.

  17. Piezoelectricity in quasicrystals: A group-theoretical study

    Indian Academy of Sciences (India)

    Group-theoretical methods have been accepted as exact and reliable tools in studying the physical properties of crystals and quasicrystalline materials. By group representation theory, the maximum number of non-vanishing and independent second- order piezoelectric coefficients required by the seven pentagonal and ...

  18. Theoretical study of the mechanism of proton transfer in tautomeric ...

    Indian Academy of Sciences (India)

    Unknown

    Theoretical study of the mechanism of proton transfer in tautomeric systems: Alloxan. RITA KAKKAR*, BHUPENDRA K SARMA and VANDANA KATOCH. Department of Chemistry, University of Delhi, Delhi 110 007, India e-mail: rita_kakkar@vsnl.com. MS received 12 July 1999; revised 18 January 2000. Abstract.

  19. Theoretical study of catalytic hydrogenation of oxirane and its methyl ...

    African Journals Online (AJOL)

    C3H6O) is its methyl derivative. Theoretical studies on catalytic hydrogenation of both compounds, in presence of aluminium chloride (AlCl3) catalyst, are carried out. The products of reactions are ethanol and propan-1-ol from oxirane and ...

  20. A combined electrochemical and theoretical study of pyridine-based ...

    Indian Academy of Sciences (India)

    PARUL DOHARE

    2018-02-01

    Feb 1, 2018 ... mild steel (MS) in 1 M hydrochloric acid solution using electrochemical experiments and theoretical study. The results showed that all the three DAPs act as mixed type corrosion inhibitors, and are adsorbed on MS surface by following Langmuir adsorption isotherm. The methyl-substituted DAP-1 showed ...

  1. Theoretical study on mechanism, kinetics, and thermochemistry of ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 127; Issue 6. Theoretical study on mechanism, kinetics, and thermochemistry of the gas phase reaction of 2,2,2-trifluoroethyl butyrate with OH radicals at 298 K. Nand Kishor Gour Bhupesh Kumar Mishra Hari Ji Singh. Regular Articles Volume 127 Issue 6 June 2015 ...

  2. Theoretical study of the mechanism of proton transfer in tautomeric ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 113; Issue 4. Theoretical study of the mechanism of proton transfer in tautomeric systems: Alloxan ... The N-H bond is almost broken, while the O-H bond is only partially formed in the transition state. The other stabilizing effect in aqueous solution is due to bulk solvent ...

  3. Theoretical study of the mechanism of proton transfer in tautomeric ...

    Indian Academy of Sciences (India)

    Theoretical study of the mechanism of proton transfer in tautomeric systems: Alloxan ... reason is the almost complete separation of the two entities, i.e. the alloxan anion and the hydronium ion in the latter case, indicating that in this case a dissociative mechanism of the kind encountered in acid-base equilibria is operating.

  4. Theoretical study and numerical simulation of secondary flow in channels

    Energy Technology Data Exchange (ETDEWEB)

    Fort, J.; Halama, J.; Hrusova, M.; Kozel, K. [Technical Univ. Prague (Czech Republic). Dept. of Technical Mathematics; Skvor, M. [Ceska Akademie Ved, Prague (Czech Republic). Inst. of Thermomechanics

    1999-12-01

    Presented work deals with flow in a 3D curved channel of constant curvature and constant rectangular cross-section. Properties of typical secondary flow structures are theoretically studied. Some cases of subsonic flow were simulated numerically by two different finite volume methods. Numerical results are compared with experimental data. (orig.)

  5. Theoretical study and numerical simulation of secondary flow in channels

    Energy Technology Data Exchange (ETDEWEB)

    Fort, J.; Halama, J.; Hrusova, M.; Kozel, K. (Technical Univ. Prague (Czech Republic). Dept. of Technical Mathematics); Skvor, M. (Ceska Akademie Ved, Prague (Czech Republic). Inst. of Thermomechanics)

    1999-01-01

    Presented work deals with flow in a 3D curved channel of constant curvature and constant rectangular cross-section. Properties of typical secondary flow structures are theoretically studied. Some cases of subsonic flow were simulated numerically by two different finite volume methods. Numerical results are compared with experimental data. (orig.)

  6. Experimental and theoretical studies on a novel helical architecture ...

    Indian Academy of Sciences (India)

    Sci. Vol. 128, No. 12, December 2016, pp. 1895–1904. c Indian Academy of Sciences. DOI 10.1007/s12039-016-1195-9. Experimental and theoretical studies on a novel helical architecture driven by hydrogen and halogen bonding interactions. QING ZHU LIUa, SHAN SHAN WANGa, TENG FEI WANGa, JIAN GUO LINa,∗.

  7. Synthesis, experimental and theoretical studies of two cocrystals in 1 ...

    Indian Academy of Sciences (India)

    Abstract. This paper reports synthesis, characterization and theoretical studies of two 1:1 stoichiometric ratio cocrystals of 4,4'-bithiazole-2,2'-diamine (DABTZ) with 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) and 1,3-bis(4-pyridyl)ethane (bpa). These cocrystal compounds have been prepared by slow evaporation method and ...

  8. A comparative kinetic and mechanistic study between tetrahydrozoline and naphazoline toward photogenerated reactive oxygen species.

    Science.gov (United States)

    Criado, Susana; García, Norman A

    2010-01-01

    Kinetic and mechanistic aspects of the vitamin B2 (riboflavin [Rf])-sensitized photo-oxidation of the imidazoline derivates (IDs) naphazoline (NPZ) and tetrahydrozoline (THZ) were investigated in aqueous solution. The process appears as important on biomedical grounds, considering that the vitamin is endogenously present in humans, and IDs are active components of ocular medicaments of topical application. Under aerobic visible light irradiation, a complex picture of competitive interactions between sensitizer, substrates and dissolved oxygen takes place: the singlet and triplet ((3)Rf*) excited states of Rf are quenched by the IDs: with IDs concentrations ca. 5.0 mM and 0.02 mM Rf, (3)Rf* is quenched by IDs, in a competitive fashion with dissolved ground state oxygen. Additionally, the reactive oxygen species: O(2)((1)Delta(g)), O(2)(*-), HO(*) and H(2)O(2), generated from (3)Rf* and Rf(*-), were detected with the employment of time-resolved methods or specific scavengers. Oxygen uptake experiments indicate that, for NPZ, only H(2)O(2) was involved in the photo-oxidation. In the case of THZ, O(2)(*-), HO(*) and H(2)O(2) were detected, whereas only HO(*) was unambiguously identified as THZ oxidative agents. Upon direct UV light irradiation NPZ and THZ generate O(2)((1)Delta(g)), with quantum yields of 0.2 (literature value, employed as a reference) and 0.08, respectively, in acetonitrile.

  9. Thermal tides and studies to tune the mechanistic tidal model using UARS observations

    Directory of Open Access Journals (Sweden)

    V. A. Yudin

    Full Text Available Monthly simulations of the thermal diurnal and semidiurnal tides are compared to High-Resolution Doppler Imager (HRDI and Wind Imaging Interferometer (WINDII wind and temperature measurements on the Upper-Atmosphere Research Satellite (UARS. There is encouraging agreement between the observations and the linear global mechanistic tidal model results both for the diurnal and semidiurnal components in the equatorial and mid-latitude regions. This gives us the confidence to outline the first steps of an assimilative analysis/interpretation for tides, dissipation, and mean flow using a combination of model results and the global measurements from HRDI and WINDII. The sensitivity of the proposed technique to the initial guess employed to obtain a best fit to the data by tuning model parameters is discussed for the January and March 1993 cases, when the WINDII day and night measurements of the meridional winds between 90 and 110 km are used along with the daytime HRDI measurements. Several examples for the derivation of the tidal variables and decomposition of the measured winds into tidal and mean flow components using this approach are compared with previous tidal estimates and modeling results for the migrating tides. The seasonal cycle of the derived diurnal tidal amplitudes are discussed and compared with radar observation between 80 and 100 km and 40°S and 40°N.

  10. Thermal tides and studies to tune the mechanistic tidal model using UARS observations

    Directory of Open Access Journals (Sweden)

    V. A. Yudin

    1997-09-01

    Full Text Available Monthly simulations of the thermal diurnal and semidiurnal tides are compared to High-Resolution Doppler Imager (HRDI and Wind Imaging Interferometer (WINDII wind and temperature measurements on the Upper-Atmosphere Research Satellite (UARS. There is encouraging agreement between the observations and the linear global mechanistic tidal model results both for the diurnal and semidiurnal components in the equatorial and mid-latitude regions. This gives us the confidence to outline the first steps of an assimilative analysis/interpretation for tides, dissipation, and mean flow using a combination of model results and the global measurements from HRDI and WINDII. The sensitivity of the proposed technique to the initial guess employed to obtain a best fit to the data by tuning model parameters is discussed for the January and March 1993 cases, when the WINDII day and night measurements of the meridional winds between 90 and 110 km are used along with the daytime HRDI measurements. Several examples for the derivation of the tidal variables and decomposition of the measured winds into tidal and mean flow components using this approach are compared with previous tidal estimates and modeling results for the migrating tides. The seasonal cycle of the derived diurnal tidal amplitudes are discussed and compared with radar observation between 80 and 100 km and 40°S and 40°N.

  11. Planning for climate change: The need for mechanistic systems-based approaches to study climate change impacts on diarrheal diseases.

    Science.gov (United States)

    Mellor, Jonathan E; Levy, Karen; Zimmerman, Julie; Elliott, Mark; Bartram, Jamie; Carlton, Elizabeth; Clasen, Thomas; Dillingham, Rebecca; Eisenberg, Joseph; Guerrant, Richard; Lantagne, Daniele; Mihelcic, James; Nelson, Kara

    2016-04-01

    Increased precipitation and temperature variability as well as extreme events related to climate change are predicted to affect the availability and quality of water globally. Already heavily burdened with diarrheal diseases due to poor access to water, sanitation and hygiene facilities, communities throughout the developing world lack the adaptive capacity to sufficiently respond to the additional adversity caused by climate change. Studies suggest that diarrhea rates are positively correlated with increased temperature, and show a complex relationship with precipitation. Although climate change will likely increase rates of diarrheal diseases on average, there is a poor mechanistic understanding of the underlying disease transmission processes and substantial uncertainty surrounding current estimates. This makes it difficult to recommend appropriate adaptation strategies. We review the relevant climate-related mechanisms behind transmission of diarrheal disease pathogens and argue that systems-based mechanistic approaches incorporating human, engineered and environmental components are urgently needed. We then review successful systems-based approaches used in other environmental health fields and detail one modeling framework to predict climate change impacts on diarrheal diseases and design adaptation strategies. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Mechanistic Studies of Ethylene and α-Olefin Co-oligomerization Catalyzed by Chromium-PNP Complexes.

    Science.gov (United States)

    Do, Loi H; Labinger, Jay A; Bercaw, John E

    2012-07-23

    To explore the possibility of producing a narrow distribution of mid- to long-chain hydrocarbons from ethylene as a chemical feedstock, co-oligomerization of ethylene and linear α-olefins (LAOs) was investigated, using a previously reported chromium complex, [CrCl(3)(PNP(OMe))] (1, where PNP(OMe) = N,N-bis(bis(o-methoxyphenyl)phosphino)methylamine). Activation of 1 by treatment with modified methylaluminoxane (MMAO) in the presence of ethylene and 1-hexene afforded mostly C(6) and C(10) alkene products. The identities of the C(10) isomers, assigned by detailed gas chromatographic and mass spectrometric analyses, strongly support a mechanism that involves five- and seven-membered metallacyclic intermediates comprising of ethylene and LAO units. Using 1-heptene as a mechanistic probe, it was established that 1-hexene formation from ethylene is competitive with formation of ethylene/LAO co-trimers, and that co-trimers derived from one ethylene and two LAO molecules are also generated. Complex 1/MMAO is also capable of converting 1-hexene to C(12) dimers and C(18) trimers, albeit with poor efficiency. The mechanistic implications of these studies are discussed and compared to previous reports of olefin co-trimerization.

  13. Homogenous Pd-catalyzed asymmetric hydrogenation of unprotected indoles: scope and mechanistic studies.

    Science.gov (United States)

    Duan, Ying; Li, Lu; Chen, Mu-Wang; Yu, Chang-Bin; Fan, Hong-Jun; Zhou, Yong-Gui

    2014-05-28

    An efficient palladium-catalyzed asymmetric hydrogenation of a variety of unprotected indoles has been developed that gives up to 98% ee using a strong Brønsted acid as the activator. This methodology was applied in the facile synthesis of biologically active products containing a chiral indoline skeleton. The mechanism of Pd-catalyzed asymmetric hydrogenation was investigated as well. Isotope-labeling reactions and ESI-HRMS proved that an iminium salt formed by protonation of the C═C bond of indoles was the significant intermediate in this reaction. The important proposed active catalytic Pd-H species was observed with (1)H NMR spectroscopy. It was found that proton exchange between the Pd-H active species and solvent trifluoroethanol (TFE) did not occur, although this proton exchange had been previously observed between metal hydrides and alcoholic solvents. Density functional theory calculations were also carried out to give further insight into the mechanism of Pd-catalyzed asymmetric hydrogenation of indoles. This combination of experimental and theoretical studies suggests that Pd-catalyzed hydrogenation goes through a stepwise outer-sphere and ionic hydrogenation mechanism. The activation of hydrogen gas is a heterolytic process assisted by trifluoroacetate of Pd complex via a six-membered-ring transition state. The reaction proceeds well in polar solvent TFE owing to its ability to stabilize the ionic intermediates in the Pd-H generation step. The strong Brønsted acid activator can remarkably decrease the energy barrier for both Pd-H generation and hydrogenation. The high enantioselectivity arises from a hydrogen-bonding interaction between N-H of the iminium salt and oxygen of the coordinated trifluoroacetate in the eight-membered-ring transition state for hydride transfer, while the active chiral Pd complex is a typical bifunctional catalyst, effecting both the hydrogenation and hydrogen-bonding interaction between the iminium salt and the coordinated

  14. Mechanistic study of plasma damage to porous low-k: Process development and dielectric recovery

    Science.gov (United States)

    Shi, Hualiang

    Low-k dielectrics with porosity are being introduced to reduce the RC delay of Cu/low-k interconnect. However, during the O2 plasma ashing process, the porous low-k dielectrics tend to degrade due to methyl depletion, moisture uptake, and densification, increasing the dielectric constant and leakage current. This dissertation presents a study of the mechanisms of plasma damage and dielectric recovery. The kinetics of plasma interaction with low-k dielectrics was investigated both experimentally and theoretically. By using a gap structure, the roles of ion, photon, and radical in producing damage on low-k dielectrics were differentiated. Oxidative plasma induced damage was proportional to the oxygen radical density, enhanced by VUV photon, and increased with substrate temperature. Ion bombardment induced surface densification, blocking radical diffusion. Two analytical models were derived to quantify the plasma damage. Based on the radical diffusion, reaction, and recombination inside porous low-k dielectrics, a plasma altered layer model was derived to interpret the chemical effect in the low ion energy region. It predicted that oxidative plasma induced damage can be reduced by decreasing pore radius, substrate temperature, and oxygen radical density and increasing carbon concentration and surface recombination rate inside low-k dielectrics. The model validity was verified by experiments and Monte-Carlo simulations. This model was also extended to the patterned low-k structure. Based on the ion collision cascade process, a sputtering yield model was introduced to interpret the physical effect in the high ion energy region. The model validity was verified by checking the ion angular and energy dependences of sputtering yield using O2/He/Ar plasma, low-k dielectrics with different k values, and a Faraday cage. Low-k dielectrics and plasma process were optimized to reduce plasma damage, including increasing carbon concentration in low-k dielectrics, switching plasma

  15. Applications of Electrospray Ionization Mass Spectrometry in Mechanistic Studies and Catalysis Research

    Czech Academy of Sciences Publication Activity Database

    Schröder, Detlef

    2012-01-01

    Roč. 45, č. 9 (2012), s. 1521-1532 ISSN 0001-4842 Grant - others:European Research Council(XE) AdG HORIZOMS Institutional support: RVO:61388963 Keywords : cross-coupling reactions * Baylis–Hillman reaction * molecular-dynamics simulations * solution-phase mechanism * gas-phase * infrared-spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 20.833, year: 2012

  16. Drug and Alcohol Studies (Volume 2: Theoretical Studies)

    OpenAIRE

    MacGregor, S; Thom, B

    2014-01-01

    VOLUME TWO: THEORETICAL PERSPECTIVES Excerpt from Drug, Set and Setting: The Basis for Controlled Intoxicant Use N. Zinberg Sociocultural Anthropology and Alcohol and Drug Research Geoffrey Hunt and Judith Barker Towards a Unified Theory Addiction Is a Brain Disease and It Matters Alan Leshner Drug Dependence A. Thomas McLellan et al A Chronic Mental Illness Alcohol Dependence Griffith Edwards and Milton Gross Provisional Description of a Clinical Syndrome Illicit Drugs and the Rise of Epidem...

  17. Mechanistic studies of formic acid oxidation at polycarbazole supported Pt nanoparticles

    International Nuclear Information System (INIS)

    Moghaddam, Reza B.; Pickup, Peter G.

    2013-01-01

    Highlights: •A polycarbazole support decreases the accumulation of adsorbed intermediates on Pt during formic acid oxidation. •Polycarbazole causes a bilayer of Cu to form on Pt nanoparticles during Cu underpotential deposition. •XPS suggests that both of these effects are due to electron donation from the metal (Pt or Cu) into the polymer π-system. -- Abstract: Mechanistic aspects of the promotion of formic acid oxidation at Pt nanoparticles supported on a thin layer of polycarbazole (PCZ) have been investigated by voltammetry and X-ray photoelectron spectroscopy (XPS). The Pt nanoparticles were drop coated onto a glassy carbon (GC) electrode coated with a ca. 9 nm layer of electrochemically deposited polycarbazole. After 500 s of formic acid oxidation at 0 V vs. SCE, the current at a GC/PCZ/Pt electrode was 25 times higher than at a GC/Pt electrode. Voltammetry in formic acid free H 2 SO 4 following potentiostatic oxidation of formic acid revealed that there was less accumulation of adsorbed intermediates for the polycarbazole supported Pt nanoparticles than for those deposited directly onto the glassy carbon with, 50% more Pt sites remaining available for the GC/PCZ/Pt electrode relative to the GC/Pt electrode. Independent CO stripping experiments revealed only slight differences, while Cu underpotential deposition surprisingly resulted in the deposition of a ca. two-fold excess of Cu on the polycarbazole supported particles. This observation was supported by XPS which also revealed a second Cu signal at a higher binding energy, suggesting electron donation into the conjugated π system of the polymer. Such an interaction of Pt with the polycarbazole may be responsible for its higher activity for formic acid oxidation

  18. Detailed Mechanistic Studies on Palladium-Catalyzed Selective C-H Olefination with Aliphatic Alkenes: A Significant Influence of Proton Shuttling.

    Science.gov (United States)

    Deb, Arghya; Hazra, Avijit; Peng, Qian; Paton, Robert S; Maiti, Debabrata

    2017-01-18

    Directing group-assisted regioselective C-H olefination with electronically biased olefins is well studied. However, the incorporation of unactivated olefins has remained largely unsuccessful. A proper mechanistic understanding of olefination involving unactivated alkenes is therefore essential for enhancing their usage in future. In this Article, detailed experimental and computational mechanistic studies on palladium catalyzed C-H olefination with unactivated, aliphatic alkenes are described. The isolation of Pd(II) intermediates is shown to be effective for elucidating the elementary steps involved in catalytic olefination. Reaction rate and order determination, control experiments, isotopic labeling studies, and Hammett analysis have been used to understand the reaction mechanism. The results from these experimental studies implicate β-hydride elimination as the rate-determining step and that a mechanistic switch occurs between cationic and neutral pathway. Computational studies support this interpretation of the experimental evidence and are used to uncover the origins of selectivity.

  19. Theoretical study of electron transport throughout some molecular structures

    Science.gov (United States)

    Abbas, Mohammed A. A.; Hanoon, Falah H.; Al-Badry, Lafy F.

    2017-11-01

    The present work is a theoretical study of the electronic properties of some molecular structures. The system that takes into account in the study is left lead-donor-molecule-acceptor-right lead. The molecule, such as (phenyl, biphenyl, triphenyl, naphthalene, anthracene, and phenanthrene), is threaded by magnetic flux. This work contains two parts. First is computing density of states of the molecular structures as a closed system by density functional theory (DFT). Second is calculating the transmission probability and electric current of such molecular structures as an open system by steady-state theoretical model. Furthermore, the most important effects, taking into consideration are quantum interference, magnetic flux, and interface structure. Our results show that the connection of the molecule to the two leads, the number of rings, the magnetic flux, and the geometrical structure of the molecule play an important role in determining the energy gap of molecular structures.

  20. A theoretical and experimental study of microshield circuits

    Science.gov (United States)

    Dib, Nihad I.; Drayton, Rhonda F.; Katehi, Linda P. B.

    1993-05-01

    The novel type of monolithic planar transmission line presently studied theoretically and experimentally operates without via-holes or ground-equalizing air bridges; it also radiates less than conventional coplanar waveguides and furnishes a wide range of impedances in virtue of its many design parameters. The space-domain integral equation method is used to analyze several discontinuities of the proposed line. It is shown that the proposed line discontinuities radiate less than the corresponding coplanar waveguide cases.

  1. Information Theoretic Studies and Assessment of Space Object Identification

    Science.gov (United States)

    2014-03-24

    AFRL-OSR-VA-TR-2014-0119 INFORMATION THEORETIC STUDIES AND ASSESMENTS OF SPACE-OBJECT IDENTIFICATION Sudhakar Prasad UNIVERSITY OF NEW MEXICO Final...5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME...S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING / MONITORING AGENCY NAME(S) AND

  2. Sociomateriality: a theoretical framework for studying distributed medical education.

    Science.gov (United States)

    MacLeod, Anna; Kits, Olga; Whelan, Emma; Fournier, Cathy; Wilson, Keith; Power, Gregory; Mann, Karen; Tummons, Jonathan; Brown, Peggy Alexiadis

    2015-11-01

    Distributed medical education (DME) is a type of distance learning in which students participate in medical education from diverse geographic locations using Web conferencing, videoconferencing, e-learning, and similar tools. DME is becoming increasingly widespread in North America and around the world.Although relatively new to medical education, distance learning has a long history in the broader field of education and a related body of literature that speaks to the importance of engaging in rigorous and theoretically informed studies of distance learning. The existing DME literature is helpful, but it has been largely descriptive and lacks a critical "lens"-that is, a theoretical perspective from which to rigorously conceptualize and interrogate DME's social (relationships, people) and material (technologies, tools) aspects.The authors describe DME and theories about distance learning and show that such theories focus on social, pedagogical, and cognitive considerations without adequately taking into account material factors. They address this gap by proposing sociomateriality as a theoretical framework allowing researchers and educators to study DME and (1) understand and consider previously obscured actors, infrastructure, and other factors that, on the surface, seem unrelated and even unimportant; (2) see clearly how the social and material components of learning are intertwined in fluid, messy, and often uncertain ways; and (3) perhaps think differently, even in ways that disrupt traditional approaches, as they explore DME. The authors conclude that DME brings with it substantial investments of social and material resources, and therefore needs careful study, using approaches that embrace its complexity.

  3. Experimental and theoretical study on the electrospinning nanoporous fibers process

    International Nuclear Information System (INIS)

    Zhao, Jianghui; Si, Na; Xu, Lan; Tang, Xiaopeng; Song, Yanhua; Sun, Zhaoyang

    2016-01-01

    Porous materials can be prepared by sol–gel method, hydrothermal synthesis method, electrospinning and other methods. In this paper, electrospun porous nanofibers were prepared by adjusting electrospinning parameters. And the properties of obtained porous nanofiber mats were investigated. Theoretical analysis and experiment research were carried out to research mechanical mechanism of electrospun porous nanofibers, and could be used to optimize and control the porous structure. The theoretical analysis results were further verified according to the experimental data. In addition, Bernoulli equation was used to study the electrospinning “splaying” process. We found the ratio of pore width to pore length was varied along with the variation of the internal pressure of the jet, and the internal pressure of the jet increases with the velocity of the charged jet decreases. - Highlights: • Mechanical mechanism of electrospun porous nanofibers process was studied. • A simplifying gas–liquid two-phase flow model was established. • Bernoulli equation was used to study the electrospinning “splaying” process. • The theoretical results were in good agreement with the experimental data. • The electrospinning parameters affected the surface morphology of charged jet.

  4. Synthesis of highly reactive polyisobutylene with FeCl3/ether complexes in hexane; kinetic and mechanistic studies

    KAUST Repository

    Kumar, Rajeev Ananda

    2015-01-01

    The kinetics and mechanism of the polymerization of isobutylene catalyzed by FeCl3·ether complexes in hexane at 0°C were investigated. The polymerization rates increased in the diisopropyl ether< 2-chloroethyl ethyl ether < bis(2-chloroethyl) ether order, attributed to electronic effects. The polymerization rates increased with increasing initiator and catalyst concentrations. The first order plots, however, deviated from the linear suggesting that the cation concentration decreases with time. The previously proposed mechanism is inadequate to explain this finding. The decrease in the polymerization rate with time is explained by the low solubility of the H+ROR′FeCl4 - complexes that precipitate during polymerization. Based on mechanistic studies the revised mechanism now also includes the equilibrium H+ROR′FeCl4 - ⇋ HCl + FeCl3·ROR′.

  5. THEORETICAL AND EXPERIMENTAL STUDY OF STRUCTURES SUBJECTED TO EARTHQUAKES

    Energy Technology Data Exchange (ETDEWEB)

    Soubirou, A.

    1967-12-31

    The object of the study was the investigation of the behaviour of structures subject to earthquakes. After .describing and analysing seismic movements, useful concepts for earthquake-proofing structures are lintroduced. Then, the dynamic behaviour of systems with n degrees of freedom was studied in order to evolve the theoretical computation of seismic behaviour, a typical application being reticulated structures. The next stage was showing the computational procedure for seismic spectra and the natural frequencies of buildings, an attempt being made to define earthquake-proofing criteria for a special type of reinforced-concrete construction. . The last matter dealt with is elastoplastic behaviour of structures, a study of increasingly growing importance.

  6. Experimental and Theoretical Studies of Atmosphereic Inorganic Chlorine Chemistry

    Science.gov (United States)

    Sander, Stanley P.; Friedl, Randall R.

    1993-01-01

    Over the last five years substantial progress has been made in defining the realm of new chlorine chemistry in the polar stratosphere. Application of existing experimental techniques to potentially important chlorine-containing compounds has yielded quantitative kinetic and spectroscopic data as well as qualitative mechanistic insights into the relevant reactions.

  7. Determinant Factors for Arterial Hemodynamics in Hypertension: Theoretical Insights From a Computational Model-Based Study.

    Science.gov (United States)

    Liang, Fuyou; Guan, Debao; Alastruey, Jordi

    2018-03-01

    Hypertension is a well-documented predictive factor for cardiovascular events. Clinical studies have extensively demonstrated the differential hemodynamic consequences of various antihypertensive drugs, but failed to clearly elucidate the underlying mechanisms due to the difficulty in performing a quantitative deterministic analysis based on clinical data that carry confounding information stemming from interpatient differences and the nonlinearity of cardiovascular hemodynamics. In the present study, a multiscale model of the cardiovascular system was developed to quantitatively investigate the relationships between hemodynamic variables and cardiovascular properties under hypertensive conditions, aiming to establish a theoretical basis for assisting in the interpretation of clinical observations or optimization of therapy. Results demonstrated that heart period, central arterial stiffness, and arteriolar radius were the major determinant factors for blood pressures and flow pulsatility indices both in large arteries and in the microcirculation. These factors differed in the degree and the way in which they affect hemodynamic variables due to their differential effects on wave reflections in the vascular system. In particular, it was found that the hemodynamic effects of varying arteriolar radius were considerably influenced by the state of central arterial stiffness, and vice versa, which implied the potential of optimizing antihypertensive treatment by selecting proper drugs based on patient-specific cardiovascular conditions. When analyzed in relation to clinical observations, the simulated results provided mechanistic explanations for the beneficial pressure-lowering effects of vasodilators as compared to β-blockers, and highlighted the significance of monitoring and normalizing arterial stiffness in the treatment of hypertension.

  8. Theoretical study of fractal growth and stability on surface

    DEFF Research Database (Denmark)

    Dick, Veronika V.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2009-01-01

    We perform a theoretical study of the fractal growing process on surface by using the deposition, diffusion, aggregation method. We present a detailed analysis of the post-growth processes occurring in a nanofractal on surface. For this study we developed a method which describes the internal...... dynamics of particles in a fractal and accounts for their diffusion and detachment. We demonstrate that these kinetic processes are responsible for the formation of the final shape of the islands on surface after the post-growth relaxation....

  9. Theoretical studies of reactions at transition metal centers

    International Nuclear Information System (INIS)

    Rappe, A.K.; Goddard, W.A. III

    1981-01-01

    The considerations discussed for ab initio theoretical studies are the type of basis set and the levels of electron correlation or lack of correlation. The prototype systems described are C1 2 M=X, where M = Ti, Cr, and Mo, and X = CH 2 , NH, and O. These studies are utilized in examining metathesis by high-oxidation-state Cr and Mo complexes. Metathesis of olefins by the Cr complexes is unfavorable because of a competing reaction involving cyclopropane elimination. Metathesis by Mo complexes is more favorable, and it is concluded that the active catalyst is an oxo-carbene complex

  10. Enantioselective polymerization of epoxides using biaryl-linked bimetallic cobalt catalysts: A mechanistic study

    KAUST Repository

    Ahmed, Syud M.

    2013-12-18

    The enantioselective polymerization of propylene oxide (PO) using biaryl-linked bimetallic salen Co catalysts was investigated experimentally and theoretically. Five key aspects of this catalytic system were examined: (1) the structural features of the catalyst, (2) the regio- and stereoselectivity of the chain-growth step, (3) the probable oxidation and electronic state of Co during the polymerization, (4) the role of the cocatalyst, and (5) the mechanism of monomer enchainment. Several important insights were revealed. First, density functional theory (DFT) calculations provided detailed structural information regarding the regio- and stereoselective chain-growth step. Specifically, the absolute stereochemistry of the binaphthol linker determines the enantiomer preference in the polymerization, and the interaction between the salen ligand and the growing polymer chain is a fundamental aspect of enantioselectivity. Second, a new bimetallic catalyst with a conformationally flexible biphenol linker was synthesized and found to enantioselectively polymerize PO, though with lower enantioselectivity than the binaphthol linked catalysts. Third, DFT calculations revealed that the active form of the catalyst has two active exo anionic ligands (chloride or carboxylate) and an endo polymer alkoxide which can ring-open an adjacent cobalt-coordinated epoxide. Fourth, calculations showed that initiation is favored by an endo chloride ligand, while propagation is favored by the presence of two exo carboxylate ligands. © 2013 American Chemical Society.

  11. Dopant-induced ignition of helium nanoplasmas—a mechanistic study

    Science.gov (United States)

    Heidenreich, Andreas; Schomas, Dominik; Mudrich, Marcel

    2017-12-01

    Helium (He) nanodroplets irradiated by intense near-infrared laser pulses form a nanoplasma by avalanche-like electron impact ionizations (EIIs) even at lower laser intensities where He is not directly field ionized, provided that the droplets contain a few dopant atoms which provide seed electrons for the EII avalanche. In this theoretical paper on calcium and xenon doped He droplets we elucidate the mechanism which induces ionization avalanches, termed ignition. We find that the partial loss of seed electrons from the activated droplets starkly assists ignition, as the Coulomb barrier for ionization of helium is lowered by the electric field of the dopant cations, and this deshielding of the cation charges enhances their electric field. In addition, the dopant ions assist the acceleration of the seed electrons (slingshot effect) by the laser field, supporting EIIs of He and also causing electron loss by catapulting electrons away. The dopants’ ability to lower the Coulomb barriers at He as well as the slingshot effect decrease with the spatial expansion of the dopant, causing a dependence of the dopants’ ignition capability on the dopant mass. Here, we develop criteria (impact count functions) to assess the ignition capability of dopants, based on (i) the spatial overlap of the seed electron cloud with the He atoms and (ii) the overlap of their kinetic energy distribution with the distribution of Coulomb barrier heights at He. The relatively long time delays between the instants of dopant ionization and ignition (incubation times) for calcium doped droplets are determined to a large extent by the time it takes to deshield the dopant ions.

  12. Theoretical and experimental study of fenofibrate and simvastatin

    Science.gov (United States)

    Nicolás Vázquez, Inés; Rodríguez-Núñez, Jesús Rubén; Peña-Caballero, Vicente; Ruvalcaba, Rene Miranda; Aceves-Hernandez, Juan Manuel

    2017-12-01

    Fenofibrate, an oral fibrate lipid lowering agent, and simvastatin, which reduces plasma levels of low-density lipoprotein cholesterol, are active pharmaceutical ingredients (APIs), currently in the market. We characterized these APIs by thermal analysis and conducted X-ray powder diffraction techniques. Studies should be carried out in the formulation stage before the final composition of a polypill may be established. Thus, it was found in thermochemical studies that both compounds present no chemical interactions in an equimolar mixture of solid samples at room temperature. Theoretical studies were employed to determine possible interactions between fenofibrate and simvastatin. A very weak intramolecular hydrogen bond is formed between the hydroxyl group (O5H5) of the simvastatin with chlorine and carbonyl group (C11O4, C1O2) of the fenofibrate molecule. These weak energy hydrogen bonds have no effect on the chemical stability of the compounds studied. The results were obtained using Density Functional Theory methods; particularly the BPE1BPE and B3LYP functional and 6-31++G** basis set. The values of energy show good approximation when are compared with similar calculations previously reported. Infrared spectra of monomers and dimers were obtained via theoretical calculations.

  13. A theoretical study for RTE-based parameter identification problems

    International Nuclear Information System (INIS)

    Tang, Jinping; Han, Bo; Han, Weimin

    2013-01-01

    This paper provides a theoretical study of reconstructing absorption and scattering coefficients based on the radiative transport equation (RTE) by using the total variation regularization method. The function space for solutions of the RTE is a natural one from the form of the boundary value problem of the RTE. We analyze the continuity and differentiability of the forward operator. We then show that the total variation regularization method can be applied for a stable solution. Convergence of the total variation-minimizing solution in the sense of the Bregman distance is also obtained. (paper)

  14. Theoretical study on perylene derivatives as fluorescent sensors for amines

    Science.gov (United States)

    Lathiotakis, Nektarios N.; Kerkines, Ioannis S. K.; Theodorakopoulos, Giannoula; Petsalakis, Ioannis D.

    2018-01-01

    A theoretical study is presented on perylene diimide (PDI) and perylene monoimide (PMI) and their action as sensors of amines in solution. Density functional theory (DFT) and Time dependent DFT (TDDFT) calculations are carried out on complexes of PDI and PMI with aniline in THF solution. The optimized geometries for the complexes have aniline lying parallel above the perylene at 3.15 Å and with binding energy of 0.53 eV in the ground state. The results on the excited states are consistent with a photoinduced electron transfer (PET) mechanism. The effective aniline-perylene distance resulting from a Mulliken's approach is 3.61 Å.

  15. Iron Complexes of Peptide Conjugates: Theoretical and Spectroscopic Study

    Czech Academy of Sciences Publication Activity Database

    Šebestík, Jaroslav; Šafařík, Martin; Bouř, Petr

    2011-01-01

    Roč. 96, č. 4 (2011), s. 506-506 ISSN 1097-0282. [ American Peptide Symposium /22./. 25.06.2011-30.06.2011, San Diego] R&D Projects: GA ČR GA203/07/1517; GA MŠk(CZ) LH11033; GA ČR GAP208/11/0105 Grant - others:AV ČR(CZ) M200550902 Institutional research plan: CEZ:AV0Z40550506 Keywords : deferipron * ferric complexes * Raman spectra * DFT study * peptide Subject RIV: CF - Physical ; Theoretical Chemistry

  16. Theoretical studies of the electronic structure of small metal clusters

    Science.gov (United States)

    Jordan, K. D.

    1982-01-01

    Theoretical studies of the electronic structure of metal clusters, in particular clusters of Group IIA and IIB atoms were conducted. Early in the project it became clear that electron correlation involving d orbitals plays a more important role in the binding of these clusters than had been previously anticipated. This necessitated that computer codes for calculating two electron integrals and for constructing the resulting CI Hamiltonions be replaced with newer, more efficient procedures. Program modification, interfacing and testing were performed. Results of both plans are reported.

  17. Theoretical Study of the Diastereofacial Isomers of Aldrin and Dieldrin

    Directory of Open Access Journals (Sweden)

    Zoran Zdravkovski

    2006-02-01

    Full Text Available The Diels-Alder reaction of hexachlorocyclopentadiene with norbornadiene givesaldrin but theoretically three other diastereofacial isomers are possible. On oxidation theseisomers can generate eight adducts one of which is known as dieldrin. All these, as well asthe corresponding reactions with hexafluorocyclopenadiene were studied by semiempirical(AM1 and PM3 and hybrid density functional (B3LYP methods. Besides the energy levels,the transition states were calculated for the reactions leading to the diastereofacial isomers ofaldrin, which indicate that aldrin is the favored product of the reaction both fromthermodynamic and kinetic point of view.

  18. Theoretical studies of parallel current in the presence of fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, M. [Nihon Univ., College of Industrial Technology, Narashino, Chiba (Japan); Shiinab, S. [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Aizawa, M.; Osanai, Y. [Nihon University, Institute of Quantum Science, College of Science and Technology, Tokyo (Japan)

    2004-07-01

    Effects of electrostatic fluctuations on the current parallel to the magnetic field theoretically studied for magnetically confined plasmas. Based upon a closed set of equations for the ensemble-averaged distribution function and the response function to an infinitesimal external perturbation, a radial diffusion equation for the bootstrap and ohmic current densities is derived. The anomalous radial diffusion due to fluctuations as well as the finite-banana width effect is shown to significantly modify the conventional bootstrap current near the magnetic axis. It is also shown that this modification leads to the possibility of the completely bootstrapped tokamak. (authors)

  19. Mechanistic Aspects of the Reversible Binding of SO2 on Arylplatinum Complexes: Experimental and ab Initio Studies

    NARCIS (Netherlands)

    Koten, G. van; Albrecht, M.A.; Gossage, R.A.; Frey, H.; Ehlers, A.W.; Baerends, E.J.; Merbach, A.E.

    2001-01-01

    The detailed mechanism of the reversible binding and fast exchange of SO2 on the organoplatinum(II) complex [PtI(NCN)], 1, has been studied experimentally in solution (C2F4Br2) using low-temperature NMR spectroscopy and theoretically by ab initio calculations. Direct bonding of SO2 and formation of

  20. Theoretical study of near-threshold electron-molecule scattering

    International Nuclear Information System (INIS)

    Morrison, M.A.

    1989-01-01

    We have been engaged in carrying out a foundation study on problems pertaining to near-threshold nuclear excitations in e-H 2 scattering. The primary goals of this study are: to investigate the severity and nature of the anticipated breakdown of the adiabatic-nuclei (AN) approximation, first for rotation only (in the rigid-rotator approximation), and then for vibration; to determine a data base of accurate ab initio cross sections for this important system; to implement and test accurate, computationally-tractable model potentials for exchange and polarization effects; and to begin the exploration of alternative scattering theories for near-threshold collisions. This study has provided a well-defined theoretical context for our future investigations. Second, it has enabled us to identify and quantify several serious problems in the theory of near-threshold electron-molecule scattering that demand attention. And finally, it has led to the development of some of the theoretical and computational apparatus that will form the foundation of future work. In this report, we shall review our progress to date, emphasizing work completed during the current contract year. 17 refs., 5 figs., 1 tab

  1. An experimental and theoretical study of reaction steps relevant to the methanol-to-hydrocarbons reaction

    Energy Technology Data Exchange (ETDEWEB)

    Svelle, Stian

    2004-07-01

    The primary objective of the present work is to obtain new insight into the reaction mechanism of the zeolite catalyzed methanol-to-hydrocarbons (MTH) reaction. It was decided to use both experimental and computational techniques to reach this goal. An investigation of the n-butene + methanol system was therefore initiated. Over time, it became apparent that it was possible to determine the rate for the methylation of n-butene by methanol. The ethene and propene systems were therefore reexamined in order to collect kinetic information also for those cases. With the development of user-friendly quantum chemistry programs such as the Gaussian suite of programs, the possibility of applying quantum chemical methods to many types of problems has become readily available even for non-experts. When performing mechanistic studies, there is quite often a considerable synergy effect when combining experimental and computational approaches. The methylation reactions mentioned above turned out to be an issue well suited for quantum chemical investigations. The incentive for examining the halomethane reactivity was the clear analogy to the MTH reaction system. Alkene dimerization was also a reaction readily examined with quantum chemistry. As discussed in the introduction of this thesis, polymethylbenzenes, or their cationic counterparts, are suspected to be key intermediates in the MTH reaction. It was therefore decided to investigate the intrinsic reactivity of these species in the gas-phase by employing sophisticated mass spectrometric (MS) techniques in collaboration with the MS group at the Department of Chemistry, University of Oslo The data thus obtained will also be compared with results from an ongoing computational study on gas phase polymethylbenzenium reactivity. 6 papers presenting various studies are included. The titles are: 1) A Theoretical Investigation of the Methylation of Alkenes with Methanol over Acidic Zeolites. 2) A Theoretical Investigation of the

  2. Final Report for the DOE-BES Program Mechanistic Studies of Activated Hydrogen Release from Amine-Boranes

    Energy Technology Data Exchange (ETDEWEB)

    Larry G. Sneddon; R. Thomas Baker

    2013-01-13

    Effective storage of hydrogen presents one of the most significant technical gaps to successful implementation of the hydrogen economy, particularly for transportation applications. Amine boranes, such as ammonia borane H3NBH3 and ammonia triborane H3NB3H7, have been identified as promising, high-capacity chemical hydrogen storage media containing potentially readily released protic (N-H) and hydridic (B-H) hydrogens. At the outset of our studies, dehydrogenation of ammonia borane had been studied primarily in the solid state, but our DOE sponsored work clearly demonstrated that ionic liquids, base-initiators and/or metal-catalysts can each significantly increase both the rate and extent of hydrogen release from amine boranes under moderate conditions. Our studies also showed that depending upon the activation method, hydrogen release from amine boranes can occur by very different mechanistic steps and yield different types of spent-fuel materials. The fundamental understanding that was developed during this grant of the pathways and controlling factors for each of these hydrogen-release mechanisms is now enabling continuing discovery and optimization of new chemical-hydride based hydrogen storage systems.

  3. Paving asphalts : reduction of oxidative hardening of asphalts by treatment with hydrated lime : a mechanistic study

    Science.gov (United States)

    1977-04-01

    This study showed that lime treatment removes polar, viscosity-building components and reduces the susceptibility of the asphalt to laboratory oxidative hardening. The beneficial effects of lime treatment in reducing asphalt oxidative hardening were ...

  4. Mechanistic Studies of Hafnium-Pyridyl Amido-Catalyzed 1-Octene Polymerization and Chain Transfer Using Quench-Labeling Methods.

    Science.gov (United States)

    Cueny, Eric S; Johnson, Heather C; Anding, Bernie J; Landis, Clark R

    2017-08-30

    Chromophore quench-labeling applied to 1-octene polymerization as catalyzed by hafnium-pyridyl amido precursors enables quantification of the amount of active catalyst and observation of the molecular weight distribution (MWD) of Hf-bound polymers via UV-GPC analysis. Comparison of the UV-detected MWD with the MWD of the "bulk" (all polymers, from RI-GPC analysis) provides important mechanistic information. The time evolution of the dual-detection GPC data, concentration of active catalyst, and monomer consumption suggests optimal activation conditions for the Hf pre-catalyst in the presence of the activator [Ph 3 C][B(C 6 F 5 ) 4 ]. The chromophore quench-labeling agents do not react with the chain-transfer agent ZnEt 2 under the reaction conditions. Thus, Hf-bound polymeryls are selectively labeled in the presence of zinc-polymeryls. Quench-labeling studies in the presence of ZnEt 2 reveal that ZnEt 2 does not influence the rate of propagation at the Hf center, and chain transfer of Hf-bound polymers to ZnEt 2 is fast and quasi-irreversible. The quench-label techniques represent a means to study commercial polymerization catalysts that operate with high efficiency at low catalyst concentrations without the need for specialized equipment.

  5. A Combined Theoretical and Experimental Study for Silver Electroplating

    Science.gov (United States)

    Liu, Anmin; Ren, Xuefeng; An, Maozhong; Zhang, Jinqiu; Yang, Peixia; Wang, Bo; Zhu, Yongming; Wang, Chong

    2014-01-01

    A novel method combined theoretical and experimental study for environmental friendly silver electroplating was introduced. Quantum chemical calculations and molecular dynamic (MD) simulations were employed for predicting the behaviour and function of the complexing agents. Electronic properties, orbital information, and single point energies of the 5,5-dimethylhydantoin (DMH), nicotinic acid (NA), as well as their silver(I)-complexes were provided by quantum chemical calculations based on density functional theory (DFT). Adsorption behaviors of the agents on copper and silver surfaces were investigated using MD simulations. Basing on the data of quantum chemical calculations and MD simulations, we believed that DMH and NA could be the promising complexing agents for silver electroplating. The experimental results, including of electrochemical measurement and silver electroplating, further confirmed the above prediction. This efficient and versatile method thus opens a new window to study or design complexing agents for generalized metal electroplating and will vigorously promote the level of this research region.

  6. The Intersection of HPV Epidemiology, Genomics and Mechanistic Studies of HPV-Mediated Carcinogenesis.

    Science.gov (United States)

    Mirabello, Lisa; Clarke, Megan A; Nelson, Chase W; Dean, Michael; Wentzensen, Nicolas; Yeager, Meredith; Cullen, Michael; Boland, Joseph F; Schiffman, Mark; Burk, Robert D

    2018-02-13

    Of the ~60 human papillomavirus (HPV) genotypes that infect the cervicovaginal epithelium, only 12-13 "high-risk" types are well-established as causing cervical cancer, with HPV16 accounting for over half of all cases worldwide. While HPV16 is the most important carcinogenic type, variants of HPV16 can differ in their carcinogenicity by 10-fold or more in epidemiologic studies. Strong genotype-phenotype associations embedded in the small 8-kb HPV16 genome motivate molecular studies to understand the underlying molecular mechanisms. Understanding the mechanisms of HPV genomic findings is complicated by the linkage of HPV genome variants. A panel of experts in various disciplines gathered on 21 November 2016 to discuss the interdisciplinary science of HPV oncogenesis. Here, we summarize the discussion of the complexity of the viral-host interaction and highlight important next steps for selected applied basic laboratory studies guided by epidemiological genomic findings.

  7. A Mechanistic Study of Hydroboration of 1-Octene with 1,3,2 ...

    African Journals Online (AJOL)

    dithiaborinane in their ground states have been studied using density functional theory (DFT) at the B3LYP/3-21+G and B3LYP/6-31+G(d) levels. Hydroboration and disproportionation transition states have been determined and activation energies ...

  8. 1 H NMR-Based Kinetic-Mechanistic Study of the Intramolecular ...

    African Journals Online (AJOL)

    A 1H NMR study of the acid-catalyzed, intramolecular trans-esterification between isomeric 2-exo-3-exo-dihydroxybornane monoacrylate esters has afforded insights into the reaction mechanism and permitted the determination of kinetic and thermodynamic parameters for the pseudo-first-order processes. KEYWORDS ...

  9. Alcohol in moderation, cardioprotection, and neuroprotection: epidemiological considerations and mechanistic studies.

    Science.gov (United States)

    Collins, Michael A; Neafsey, Edward J; Mukamal, Kenneth J; Gray, Mary O; Parks, Dale A; Das, Dipak K; Korthuis, Ronald J

    2009-02-01

    In contrast to many years of important research and clinical attention to the pathological effects of alcohol (ethanol) abuse, the past several decades have seen the publication of a number of peer-reviewed studies indicating the beneficial effects of light-moderate, nonbinge consumption of varied alcoholic beverages, as well as experimental demonstrations that moderate alcohol exposure can initiate typically cytoprotective mechanisms. A considerable body of epidemiology associates moderate alcohol consumption with significantly reduced risks of coronary heart disease and, albeit currently a less robust relationship, cerebrovascular (ischemic) stroke. Experimental studies with experimental rodent models and cultures (cardiac myocytes, endothelial cells) indicate that moderate alcohol exposure can promote anti-inflammatory processes involving adenosine receptors, protein kinase C (PKC), nitric oxide synthase, heat shock proteins, and others which could underlie cardioprotection. Also, brain functional comparisons between older moderate alcohol consumers and nondrinkers have received more recent epidemiological study. In over half of nearly 45 reports since the early 1990s, significantly reduced risks of cognitive loss or dementia in moderate, nonbinge consumers of alcohol (wine, beer, liquor) have been observed, whereas increased risk has been seen only in a few studies. Physiological explanations for the apparent CNS benefits of moderate consumption have invoked alcohol's cardiovascular and/or hematological effects, but there is also experimental evidence that moderate alcohol levels can exert direct "neuroprotective" actions-pertinent are several studies in vivo and rat brain organotypic cultures, in which antecedent or preconditioning exposure to moderate alcohol neuroprotects against ischemia, endotoxin, beta-amyloid, a toxic protein intimately associated with Alzheimer's, or gp120, the neuroinflammatory HIV-1 envelope protein. The alcohol

  10. Effects of noise on vascular function, oxidative stress, and inflammation: mechanistic insight from studies in mice.

    Science.gov (United States)

    Münzel, Thomas; Daiber, Andreas; Steven, Sebastian; Tran, Lan P; Ullmann, Elisabeth; Kossmann, Sabine; Schmidt, Frank P; Oelze, Matthias; Xia, Ning; Li, Huige; Pinto, Antonio; Wild, Philipp; Pies, Kai; Schmidt, Erwin R; Rapp, Steffen; Kröller-Schön, Swenja

    2017-10-01

    Epidemiological studies indicate that traffic noise increases the incidence of coronary artery disease, hypertension and stroke. The underlying mechanisms remain largely unknown. Field studies with nighttime noise exposure demonstrate that aircraft noise leads to vascular dysfunction, which is markedly improved by vitamin C, suggesting a key role of oxidative stress in causing this phenomenon. We developed a novel animal model to study the vascular consequences of aircraft noise exposure. Peak sound levels of 85 and mean sound level of 72 dBA applied by loudspeakers for 4 days caused an increase in systolic blood pressure, plasma noradrenaline and angiotensin II levels and induced endothelial dysfunction. Noise increased eNOS expression but reduced vascular NO levels because of eNOS uncoupling. Noise increased circulating levels of nitrotyrosine, interleukine-6 and vascular expression of the NADPH oxidase subunit Nox2, nitrotyrosine-positive proteins and of endothelin-1. FACS analysis demonstrated an increase in infiltrated natural killer-cells and neutrophils into the vasculature. Equal mean sound pressure levels of white noise for 4 days did not induce these changes. Comparative Illumina sequencing of transcriptomes of aortic tissues from aircraft noise-treated animals displayed significant changes of genes in part responsible for the regulation of vascular function, vascular remodelling, and cell death. We established a novel and unique aircraft noise stress model with increased blood pressure and vascular dysfunction associated with oxidative stress. This animal model enables future studies of molecular mechanisms, mitigation strategies, and pharmacological interventions to protect from noise-induced vascular damage. © The Author 2017. Published by Oxford University Press on behalf of the European Society of Cardiology.

  11. Effects of noise on vascular function, oxidative stress, and inflammation: mechanistic insight from studies in mice

    Science.gov (United States)

    Münzel, Thomas; Daiber, Andreas; Steven, Sebastian; Tran, Lan P.; Ullmann, Elisabeth; Kossmann, Sabine; Schmidt, Frank P.; Oelze, Matthias; Xia, Ning; Li, Huige; Pinto, Antonio; Wild, Philipp; Pies, Kai; Schmidt, Erwin R.; Rapp, Steffen; Kröller-Schön, Swenja

    2017-01-01

    Abstract Aims Epidemiological studies indicate that traffic noise increases the incidence of coronary artery disease, hypertension and stroke. The underlying mechanisms remain largely unknown. Field studies with nighttime noise exposure demonstrate that aircraft noise leads to vascular dysfunction, which is markedly improved by vitamin C, suggesting a key role of oxidative stress in causing this phenomenon. Methods and results We developed a novel animal model to study the vascular consequences of aircraft noise exposure. Peak sound levels of 85 and mean sound level of 72 dBA applied by loudspeakers for 4 days caused an increase in systolic blood pressure, plasma noradrenaline and angiotensin II levels and induced endothelial dysfunction. Noise increased eNOS expression but reduced vascular NO levels because of eNOS uncoupling. Noise increased circulating levels of nitrotyrosine, interleukine-6 and vascular expression of the NADPH oxidase subunit Nox2, nitrotyrosine-positive proteins and of endothelin-1. FACS analysis demonstrated an increase in infiltrated natural killer-cells and neutrophils into the vasculature. Equal mean sound pressure levels of white noise for 4 days did not induce these changes. Comparative Illumina sequencing of transcriptomes of aortic tissues from aircraft noise-treated animals displayed significant changes of genes in part responsible for the regulation of vascular function, vascular remodelling, and cell death. Conclusion We established a novel and unique aircraft noise stress model with increased blood pressure and vascular dysfunction associated with oxidative stress. This animal model enables future studies of molecular mechanisms, mitigation strategies, and pharmacological interventions to protect from noise-induced vascular damage. PMID:28329261

  12. A Mechanistic Study of Hydroboration of 1-Octene with 1,3,2 ...

    African Journals Online (AJOL)

    NJD

    the hydroboration kinetics study, due to the low percentage of. BH3·SMe2 obtained. This reduces the possible ... This means that the B-H bond breaks and the B-OH bond forms. After oxidation, these reagents are not useful in ... under inert atmosphere and low temperatures (ca. 5 °C). 2.3. Hydroboration of 1-Octene with 1,3 ...

  13. Rapid tissue regeneration induced by intracellular ATP delivery-A preliminary mechanistic study.

    Directory of Open Access Journals (Sweden)

    Harshini Sarojini

    Full Text Available We have reported a new phenomenon in acute wound healing following the use of intracellular ATP delivery-extremely rapid tissue regeneration, which starts less than 24 h after surgery, and is accompanied by massive macrophage trafficking, in situ proliferation, and direct collagen production. This unusual process bypasses the formation of the traditional provisional extracellular matrix and significantly shortens the wound healing process. Although macrophages/monocytes are known to play a critical role in the initiation and progression of wound healing, their in situ proliferation and direct collagen production in wound healing have never been reported previously. We have explored these two very specific pathways during wound healing, while excluding confounding factors in the in vivo environment by analyzing wound samples and performing in vitro studies. The use of immunohistochemical studies enabled the detection of in situ macrophage proliferation in ATP-vesicle treated wounds. Primary human macrophages and Raw 264.7 cells were used for an in vitro study involving treatment with ATP vesicles, free Mg-ATP alone, lipid vesicles alone, Regranex, or culture medium. Collagen type 1α 1, MCP-1, IL-6, and IL-10 levels were determined by ELISA of the culture supernatant. The intracellular collagen type 1α1 localization was determined with immunocytochemistry. ATP-vesicle treated wounds showed high immunoreactivity towards BrdU and PCNA antigens, indicating in situ proliferation. Most of the cultured macrophages treated with ATP-vesicles maintained their classic phenotype and expressed high levels of collagen type 1α1 for a longer duration than was observed with cells treated with Regranex. These studies provide the first clear evidence of in situ macrophage proliferation and direct collagen production during wound healing. These findings provide part of the explanation for the extremely rapid tissue regeneration, and this treatment may hold

  14. Alcohol in Moderation, Cardioprotection and Neuroprotection: Epidemiological Considerations and Mechanistic Studies

    OpenAIRE

    Collins, Michael A.; Neafsey, Edward J.; Mukamal, Kenneth J.; Gray, Mary O.; Parks, Dale A.; Das, Dipak K.; Korthuis, Ronald J.

    2008-01-01

    In contrast to many years of important research and clinical attention to the pathological effects of alcohol (ethanol) abuse, the past several decades have seen the publication of a number of peer-reviewed studies indicating beneficial effects of light-moderate, non-binge consumption of varied alcoholic beverages, as well as experimental demonstrations that moderate alcohol exposure can initiate typically cytoprotective mechanisms. A considerable body of epidemiology associates moderate alco...

  15. Tightly Coupled Mechanistic Study of Materials in the Extreme Space Environment

    Science.gov (United States)

    2016-10-11

    Japan Society for Aeronautical and Space Sciences, Vol. 46, 2003, pp. 24-30. 2. Wang, J. , Cao, Y., Kafafy, R., Pierru, J...tomography.” Ultramicroscopy 132, 121-128 (2013) 19. Rahnamoun, A.; van Duin, A. C. T. Journal of Physical Chemistry A 2014, 118, 2780. 20. Hong, S... Journal of Physical Chemistry C 119, 17876-17886. 21. Verners, O., Psofogiannakis, G., and van Duin, A., 2015. Comparative molecular dynamics study

  16. Mechanistic Studies on the Use of Polygonum multiflorum for the Treatment of Hair Graying

    OpenAIRE

    Han, Ming-Nuan; Lu, Jian-Mei; Zhang, Guang-Yuan; Yu, Jie; Zhao, Rong-Hua

    2015-01-01

    Polygonum multiflorum is a traditional Chinese medicine with a long history in hair growth promotion and hair blackening. The purpose of the study was to examine the effect and the mechanism of Polygonum multiflorum in hair blackening. C57BL/6 mice hair fade was induced with H2O2 and used in this research. Hair pigmentogenesis promotion activities of Polygonum Multiflorum Radix (PMR, raw crude drug), Polygonum Multiflorum Radix Preparata (PMRP, processed crude drug), and their major chemical ...

  17. Soybean peroxidase-mediated degradation of an azo dye- a detailed mechanistic study.

    Science.gov (United States)

    Ali, Liaquat; Algaithi, Rowdha; Habib, Hosam M; Souka, Usama; Rauf, Muhammad A; Ashraf, S Salman

    2013-12-05

    Peroxidases are emerging as an important class of enzymes that can be used for the efficient degradation of organic pollutants. However, detailed studies identifying the various intermediates produced and the mechanisms involved in the enzyme-mediated pollutant degradation are not widely published. In the present study, the enzymatic degradation of an azo dye (Crystal Ponceau 6R, CP6R) was studied using commercially available soybean peroxidase (SBP) enzyme. Several operational parameters affecting the enzymatic degradation of dye were evaluated and optimized, such as initial dye concentration, H2O2 dosage, mediator amount and pH of the solution. Under optimized conditions, 40 ppm dye solution could be completely degraded in under one minute by SBP in the presence of H2O2 and a redox mediator. Dye degradation was also confirmed using HPLC and TOC analyses, which showed that most of the dye was being mineralized to CO2 in the process. Detailed analysis of metabolites, based on LC/MS results, showed that the enzyme-based degradation of the CP6R dye proceeded in two different reaction pathways- via symmetric azo bond cleavage as well as asymmetric azo bond breakage in the dye molecule. In addition, various critical transformative and oxidative steps such as deamination, desulfonation, keto-oxidation are explained on an electronic level. Furthermore, LC/MS/MS analyses confirmed that the end products in both pathways were small chain aliphatic carboxylic acids.

  18. Soybean peroxidase-mediated degradation of an azo dye– a detailed mechanistic study

    Science.gov (United States)

    2013-01-01

    Background Peroxidases are emerging as an important class of enzymes that can be used for the efficient degradation of organic pollutants. However, detailed studies identifying the various intermediates produced and the mechanisms involved in the enzyme-mediated pollutant degradation are not widely published. Results In the present study, the enzymatic degradation of an azo dye (Crystal Ponceau 6R, CP6R) was studied using commercially available soybean peroxidase (SBP) enzyme. Several operational parameters affecting the enzymatic degradation of dye were evaluated and optimized, such as initial dye concentration, H2O2 dosage, mediator amount and pH of the solution. Under optimized conditions, 40 ppm dye solution could be completely degraded in under one minute by SBP in the presence of H2O2 and a redox mediator. Dye degradation was also confirmed using HPLC and TOC analyses, which showed that most of the dye was being mineralized to CO2 in the process. Conclusions Detailed analysis of metabolites, based on LC/MS results, showed that the enzyme-based degradation of the CP6R dye proceeded in two different reaction pathways- via symmetric azo bond cleavage as well as asymmetric azo bond breakage in the dye molecule. In addition, various critical transformative and oxidative steps such as deamination, desulfonation, keto-oxidation are explained on an electronic level. Furthermore, LC/MS/MS analyses confirmed that the end products in both pathways were small chain aliphatic carboxylic acids. PMID:24308857

  19. β-Elemene: Mechanistic Studies on Cancer Cell Interaction and Its Chemosensitization Effect

    Science.gov (United States)

    Jiang, Ziyu; Jacob, Joe A.; Loganathachetti, Dinesh S.; Nainangu, Prasannabalaji; Chen, Baoan

    2017-01-01

    Over the past decade, screening and identifying novel compounds for their biomedical applications has become an upcoming area of research. Identifying the molecular mechanisms of these compounds has become an integral part of anticancer research. β-elemene, a sesquiterpene, is renowned for its anticancer activity against a variety of cell lines. Recent studies on β-elemene have elucidated that it possesses anti-proliferative effect on cancer cells by creating an apoptotic trigger. Interestingly, it also induces protective autophagy in some cancerous cell lines and is less cytotoxic compared to other widely accepted chemotherapeutic agents. This provides an edge with the perception of limited toxicity to normal cells. This mini-review precisely focuses on the studies performed to identify the mechanism of anticancer activity of β-elemene against cancer cells of multiple origin. In accordance to the evaluation made by the studies mentioned, apoptosis has been identified to be most possible reason behind anticancer activity exerted by β-elemene against a variety of cancer cell lines. Cell cycle arrest and necrosis have been credited to be possible alternate mechanisms for the anticancer effect of β-elemene. PMID:28337141

  20. Mechanistic study of nickel based catalysts for oxygen evolution and methanol oxidation in alkaline medium

    Science.gov (United States)

    Chen, Dayi; Minteer, Shelley D.

    2015-06-01

    Nickel based catalysts have been studied as catalysts for either organic compound (especially methanol) oxidation or oxygen evolution reactions in alkaline medium for decades, but methanol oxidation and oxygen evolution reactions occur at a similar potential range and pH with nickel based catalysts. In contrast to previous studies, we studied these two reactions simultaneously under various pH and methanol concentrations with electrodes containing a series of NiOOH surface concentrations. We found that nickel based catalysts are more suitable to be used as oxygen evolution catalysts than methanol oxidation catalysts based on the observation that: The rate-determining step of methanol oxidation involves NiOOH, OH- and methanol while high methanol to OH- ratio could poison the NiOOH sites. Since NiOOH is involved in the rate-determining step, methanol oxidation suffers from high overpotential and oxygen evolution is favored over methanol oxidation in the presence of an equivalent amount (0.1 M) of alkali and methanol.

  1. Empirical Force Fields for Mechanistic Studies of Chemical Reactions in Proteins.

    Science.gov (United States)

    Das, A K; Meuwly, M

    2016-01-01

    Following chemical reactions in atomistic detail is one of the most challenging aspects of current computational approaches to chemistry. In this chapter the application of adiabatic reactive MD (ARMD) and its multistate version (MS-ARMD) are discussed. Both methods allow to study bond-breaking and bond-forming processes in chemical and biological processes. Particular emphasis is put on practical aspects for applying the methods to investigate the dynamics of chemical reactions. The chapter closes with an outlook of possible generalizations of the methods discussed. © 2016 Elsevier Inc. All rights reserved.

  2. Optimization of Grignard Addition to Esters: Kinetic and Mechanistic Study of Model Phthalide using Flow Chemistry

    DEFF Research Database (Denmark)

    Pedersen, Michael J.; Born, Stephen; Neuenschwander, Ulrich

    2018-01-01

    The kinetics of sequential addition of a distinct Grignard species onto a lactone is studied by flow chemistry. The experimental data are shown to be consistent with a kinetic model based on four reaction steps, reaction of ester to magnesium hemiacetal, rearrangement to ketone (forward...... and backward) and reaction of ketone to tertiary alcohol upon quenching. The experimental derived reaction mechanism is supported by ab initio molecular computations, and the predicted activation energy is in good agreement with the experimental observations. The Grignard reaction follows a substrate...

  3. Mechanistic studies aimed at the development of single site metal alkoxide catalysts for the production of polyoxygenates from renewable resources.

    Energy Technology Data Exchange (ETDEWEB)

    Chisholm, Malcolm H. [The Ohio State Univ., Columbus, OH (United States)

    2015-12-15

    The work proposed herein follows on directly from the existing 3 year grant and the request for funding is for 12 months to allow completion of this work and graduation of current students supported by DOE. The three primary projects are as follows. 1.) A comparative study of the reactivity of LMg(OR) (solvent), where L= a β-diiminate or pyrromethene ligand, in the ring-opening of cyclic esters. 2.) The homopolymerization of expoxides, particularly propylene oxide and styrene oxide, and their copolymerizations with carbon dioxide or organic anhydrides to yield polycarbonates or polyesters, respectively. 3.) The development of well-defined bismuth (III) complexes for ring-opening polymerizations that are tolerant of both air and water. In each of these topics special emphasis is placed on developing a detailed mechanistic understanding of the ring-opening event and how this is modified by the employment of specific metal and ligand combinations. This document also provides a report on findings of the past grant period that are not yet in the public domain/published and shows how the proposed work will bring the original project to conclusion.

  4. Cationic Pd(II-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

    Directory of Open Access Journals (Sweden)

    Takashi Nishikata

    2016-05-01

    Full Text Available Cationic palladium(II complexes have been found to be highly reactive towards aromatic C–H activation of arylureas at room temperature. A commercially available catalyst [Pd(MeCN4](BF42 or a nitrile-free cationic palladium(II complex generated in situ from the reaction of Pd(OAc2 and HBF4, effectively catalyzes C–H activation/cross-coupling reactions between aryl iodides, arylboronic acids and acrylates under milder conditions than those previously reported. The nature of the directing group was found to be critical for achieving room temperature conditions, with the urea moiety the most effective in promoting facile coupling reactions at an ortho C–H position. This methodology has been utilized in a streamlined and efficient synthesis of boscalid, an agent produced on the kiloton scale annually and used to control a range of plant pathogens in broadacre and horticultural crops. Mechanistic investigations led to a proposed catalytic cycle involving three steps: (1 C–H activation to generate a cationic palladacycle; (2 reaction of the cationic palladacycle with an aryl iodide, arylboronic acid or acrylate, and (3 regeneration of the active cationic palladium catalyst. The reaction between a cationic palladium(II complex and arylurea allowed the formation and isolation of the corresponding palladacycle intermediate, characterized by X-ray analysis. Roles of various additives in the stepwise process have also been studied.

  5. Development and mechanistic studies of an optimized receptor for trimethyllysine using iterative redesign by dynamic combinatorial chemistry.

    Science.gov (United States)

    Pinkin, Nicholas K; Waters, Marcey L

    2014-09-28

    A new small molecule receptor, A2N, has been identified that binds specifically to trimethyllysine (Kme3) with sub-micromolar affinity. This receptor was discovered through the iterative redesign of a monomer known to incorporate through dynamic combinatorial chemistry (DCC) into a previously reported receptor for Kme3, A2B. In place of monomer B, the newly designed monomer N introduces an additional cation-π interaction into the binding pocket, resulting in more favorable binding to Kme3 by 1.3 kcal mol(-1), amounting to a 10-fold improvement in affinity and a 5-fold improvement in selectivity over Kme2. This receptor exhibits the tightest affinity and greatest selectivity for KMe3-containing peptides reported to date. Comparative studies of A2B and A2N provide mechanistic insight into the driving force for both the higher affinity and higher selectivity of A2N, indicating that the binding of KMe3 to A2N is both enthalpically and entropically more favorable. This work demonstrates the ability of iterative redesign coupled with DCC to develop novel selective receptors with the necessary affinity and selectivity required for biological applications.

  6. A kinetic mechanistic study of acid-catalyzed alkylation of isobutane with C4-olefins at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Doshi, B.M.

    1978-01-01

    A kinetic and mechanistic study of sulfuric acid-catalyzed alkylation of isobutane with C/sub 4/-Olefins at Low Temperatures(-20/sup 0/ to 0/sup 0/C) was based on a new two-step reaction sequence in which the desired first-step reactions are between acid and olefin to form sulfates and the desired second-step reactions are between sulfates and isobutane to form mostly trimethylpentanes. Linear butenes formed stable sulfates that formed alkylates of exceptionally high quality, up to 100 Research octane, whereas isobutylene and trimethylpentene mainly polymerized during the first step, and the alkylate produced had only 90 Research octane. Trimethylpentanes and dimethylhexanes, when contacted with concentrated sulfuric acid at -10/sup 0/ to +25/sup 0/C, degraded and isomerized to form C/sub 4/-C/sub 9/ and higher isoparaffins and acid-soluble hydrocarbons (conjunct polymers). For the two-step process and the degradation and isomerization reactions, kinetic models based on reaction at the interface were developed; but for isoolefins, a polymerization-cracking sequence (via C/sub 12/- and even C/sub 16/-olefins) is the preferred route. Commercial applications of the results are proposed.

  7. Time-resolved and mechanistic study of the photochemical uncaging reaction of the o-hydroxycinnamic caged compound.

    Science.gov (United States)

    Yu, Youqing; Wu, Lidan; Zou, Xiaoran; Dai, Xiaojuan; Liu, Kunhui; Su, Hongmei

    2013-08-22

    The o-hydroxycinnamic derivatives represent efficient caged compounds that can realize quantification of delivery upon uncaging, but there has been lack of time-resolved and mechanistic studies. We used time-resolved infrared (TRIR) spectroscopy to investigate the photochemical uncaging dynamics of the prototype o-hydroxycinnamic compound, (E)-3-(2-hydroxyphenyl)-acrylic acid ethyl ester (HAAEE), leading to coumarin and ethanol upon uncaging. Taking advantage of the specific vibrational marker bands and the IR discerning capability, we have identified and distinguished two key intermediate species, the cis-isomers of HAAEE and the tetrahedral intermediate, in the transient infrared spectra, thus providing clear spectral evidence to support the intramolecular nucleophilic addition mechanism following the trans-cis photoisomerization. Moreover, the product yields of coumarin upon uncaging were observed to be greatly affected by the solvent polarity, suppressed in CH2Cl2 but enhanced in D2O/CH3CN with the increasing volume ratio of D2O. The highly solvent-dependent behavior indicates E1 elimination of the tetrahedral intermediate to give rise to the final uncaging product coumarin. The photorelease rate of coumarin was directly characterized from TRIR (3.6 × 10(6) s(-1)), revealing the promising application of such o-hydroxycinnamic compound in producing fast alcohol jumps. The TRIR results provide the first time-resolved detection and thus offer direct dynamical information about this photochemical uncaging reaction.

  8. A mechanistic study on the destabilization of whole inactivated influenza virus vaccine in gastric environment.

    Science.gov (United States)

    Choi, Hyo-Jick; Ebersbacher, Charles F; Kim, Min-Chul; Kang, Sang-Moo; Montemagno, Carlo D

    2013-01-01

    Oral immunization using whole inactivated influenza virus vaccine promises an efficient vaccination strategy. While oral vaccination was hampered by harsh gastric environment, a systematic understanding about vaccine destabilization mechanisms was not performed. Here, we investigated the separate and combined effects of temperature, retention time, pH, and osmotic stress on the stability of influenza vaccine by monitoring the time-dependent morphological change using stopped-flow light scattering. When exposed to osmotic stress, clustering of vaccine particles was enhanced in an acidic medium (pH 2.0) at ≥25°C. Fluorescence spectroscopic studies showed that hyper-osmotic stress at pH 2.0 and 37°C caused a considerable increase in conformational change of antigenic proteins compared to that in acidic iso-osmotic medium. A structural integrity of membrane was destroyed upon exposure to hyper-osmotic stress, leading to irreversible morphological change, as observed by undulation in stopped-flow light scattering intensity and transmission electron microscopy. Consistent with these analyses, hemagglutination activity decreased more significantly with an increasing magnitude of hyper-osmotic stress than in the presence of the hypo- and iso-osmotic stresses. This study shows that the magnitude and direction of the osmotic gradient has a substantial impact on the stability of orally administrated influenza vaccine.

  9. A mechanistic study on the Hooker oxidation: synthesis of novel indane carboxylic acid derivatives from lapachol.

    Science.gov (United States)

    Eyong, Kenneth O; Puppala, Manohar; Kumar, Ponminor Senthil; Lamshöft, Marc; Folefoc, Gabriel N; Spiteller, Michael; Baskaran, Sundarababu

    2013-01-21

    The Hooker oxidation is one of the most intriguing transformations wherein lapachol (1) is readily converted to norlapachol (2) in very good yield. This one-pot reaction involves a very intricate mechanism in which the alkyl side chain of lapachol is shortened by one carbon unit. Previous studies have unequivocally established the involvement of an indane carboxylic acid derivative 3, as a key intermediate (Hooker intermediate), and its simultaneous conversion to norlapachol (2) via the oxidative cleavage of vicinol diol and subsequent intramolecular aldol reaction of the resulting keto acid. However, the formation of the key Hooker intermediate 3 from lapachol (1) remains ambiguous. The present study has thrown some light on the formation of the key intermediate 3 from lapachol (1) via benzilic acid rearrangement of the corresponding labile o-diquinone intermediate 8 derived from lapachol. The involvement of o-diquinone intermediate 8 in the Hooker oxidation has been further established by trapping of this labile intermediate as the corresponding phenazine derivative 9. The involvement of benzilic acid rearrangement as a key step in the Hooker oxidation is further shown with a variety of o-quinones prepared from lapachol (1).

  10. A mechanistic study on the destabilization of whole inactivated influenza virus vaccine in gastric environment.

    Directory of Open Access Journals (Sweden)

    Hyo-Jick Choi

    Full Text Available Oral immunization using whole inactivated influenza virus vaccine promises an efficient vaccination strategy. While oral vaccination was hampered by harsh gastric environment, a systematic understanding about vaccine destabilization mechanisms was not performed. Here, we investigated the separate and combined effects of temperature, retention time, pH, and osmotic stress on the stability of influenza vaccine by monitoring the time-dependent morphological change using stopped-flow light scattering. When exposed to osmotic stress, clustering of vaccine particles was enhanced in an acidic medium (pH 2.0 at ≥25°C. Fluorescence spectroscopic studies showed that hyper-osmotic stress at pH 2.0 and 37°C caused a considerable increase in conformational change of antigenic proteins compared to that in acidic iso-osmotic medium. A structural integrity of membrane was destroyed upon exposure to hyper-osmotic stress, leading to irreversible morphological change, as observed by undulation in stopped-flow light scattering intensity and transmission electron microscopy. Consistent with these analyses, hemagglutination activity decreased more significantly with an increasing magnitude of hyper-osmotic stress than in the presence of the hypo- and iso-osmotic stresses. This study shows that the magnitude and direction of the osmotic gradient has a substantial impact on the stability of orally administrated influenza vaccine.

  11. A mechanistic study on the simultaneous elimination of soot and nitric oxide from engine exhaust

    KAUST Repository

    Raj, Abhijeet

    2011-04-01

    The non-catalytic interaction between soot and nitric oxide (NO) resulting in their simultaneous elimination was studied on different types of reactive site present on soot. The reaction mechanism proposed previously was extended by including seven new reaction pathways for which the reaction energetics and kinetics were studied using density functional theory and transition state theory. This has led to the calculation of a new rate for the removal of carbon monoxide (CO) from soot. The new pathways have been added to our polycyclic aromatic hydrocarbon (PAH) growth model and used to simulate the NO-soot interaction to form CO, N2 and N2O. The simulation results show satisfactory agreement with experiment for the new CO removal rate. The NO-soot reaction was found to depend strongly on the soot site type and temperature. For a set of temperatures, computed PAH structures were analysed to determine the functional groups responsible for the decrease in the reactivity of soot with NO with increasing reaction time. In isothermal conditions, it was found that as temperature is increased, the number of oxygen atoms remaining on the soot surface decreases, while the number of nitrogen atoms increases for a given reaction time. © 2010 Elsevier Ltd. All rights reserved.

  12. Mechanistic study of the interaction of uranyl ions with zirconium oxide and zirconium silicate

    International Nuclear Information System (INIS)

    Lomenech, C.

    2002-04-01

    This work deals with structural and thermodynamic studies of the sorption of uranyl species on zircon and zirconia. After determination of the specific areas, of the pH of the isoelectric points, and of the sorption site numbers, thermodynamic data were obtained using alpha spectrometry, for different uranyl concentrations, different background electrolytes (NaClO 4 or KNO 3 ) and different ionic strengths. The structural identification of the surface complexes and sorption sites was carried out using several spectroscopies: XPS spectroscopy allowed a determination of the nature of the sorption sites (≡Zr-O- on zirconia and ≡Si-O- on zircon). Whereas fluorescence decay measurements gave the number of surface species, the combined use of XPS spectroscopy and laser spectro-fluorimetry enabled us to correlate differences in bonding energies and emission wavelengths with differences in the nature of the background electrolyte or in the pH of sorption; DRIFT spectroscopy was a powerful tool for the determination of the presence of sorbed uranyl nitrate species. EXAFS results clearly showed a splitting of the equatorial oxygen atoms in two shells, corresponding to a polydentate, inner-sphere complex. EXAFS results also indicated strong similarities between dry samples and in situ experiments, which confirms the validity of all the spectroscopic measurements. Macroscopic thermodynamic data were then modeled using a surface complexation model (2 pK and constant capacitance models), the results of the structural study being used as constraints for the simulation code FITEQL. (author)

  13. The myotoxicity of organic cosolvents following intramuscular injection: Characterization and mechanistic studies

    International Nuclear Information System (INIS)

    Brazeau, G.A.

    1989-01-01

    An in vitro rat muscle model for myotoxicity estimation was first developed. This system, which utilizes creatine kinase release as an index of myotoxicity, allows the myotoxicity of intramuscular solutions to be rapidly screened, without the limitations associated with published methods. This in vitro myotoxicity screening technique was validated against in vivo myotoxicity data in rabbits. The concentration-myotoxicity relationships were determined for the aqueous solutions of each of the cosolvents. The myotoxicity of mixed solvents consisting of propylene glycol, ethanol, and water was shown to be additive. This relationship of linear combination did not apply to ternary mixtures containing polyethylene glycol 400, which appeared to exert a protective effect in these mixtures. The possible mechanisms of organic cosolvent-induced myotoxicity were investigated. Myotoxicity was shown not to be linearly correlated with simple physicochemical properties nor with linear combinations of these properties. Results from biochemical studies suggested that organic cosolvent-induced creatine kinase release was caused by alterations in intracellular calcium homeostasis and not by direct solubilization of the sarcolemma. A final study explored the effect of muscle damage on the intramuscular bioavailability of a model compound dissolved in three cosolvent solutions with similar physicochemical properties but with different myotoxicities. Relative-bioavailability of a 14 C-diazepam tracer dose was not different among these solutions, while the in vivo myotoxicity of the solutions varied ten fold. These initial findings suggest that intramuscular drug bioavailability does not appear to be affected by skeletal muscle damage

  14. Using Mechanistic Studies to Model Riparian Tree Establishment Under Environmental Flow Scenarios on Regulated Rivers

    Science.gov (United States)

    Stella, J. C.; Battles, J. J.; McBride, J. R.; Orr, B. K.

    2007-12-01

    In the Central Valley of California, pioneer cottonwood and willow species dominate the near-river forests. Historically, seedling recruitment for these disturbance-adapted species coincided with spring floods. Changes in flow timing and magnitude due to river regulation have decreased the success of seedling cohorts and contributed to the decline of these riparian tree populations. In order to address gaps in our understanding of these species and potential restoration strategies, we field-calibrated a conceptual model of seedling recruitment for the dominant pioneer woody species, Populus fremontii, Salix gooddingii, and S. exigua. We conducted experiments to identify seedling desiccation thresholds and seed longevity, used field studies to measure seedling competition and seasonal seed release patterns, and modeled interannual differences in dispersal timing using a degree-day model. These studies were integrated into a recruitment model that generates annual estimates of seedling density and bank elevation based on inputs of seasonal river discharge, seed dispersal timing, and seedling mortality from desiccation. The model predictions successfully captured interannual and species-level patterns in recruitment observed independently throughout a 20-km reach of the lower Tuolumne River from 2002-04. The model correctly predicted that seedling densities were highest in 2004 and lowest in 2003, and that S. exigua recruitment would be less extensive than for the two tree species. This work shows promise as both a quantitative approach linking hydrology, climate and plant community dynamics, and as a process-based framework for guiding flow releases and other management actions to restore riparian tree population along Central Valley rivers.

  15. Atmospheric degradation of alkylfurans with chlorine atoms: Product and mechanistic study

    Science.gov (United States)

    Villanueva, F.; Cabañas, B.; Monedero, E.; Salgado, S.; Bejan, I.; Martin, P.

    As part of a study on the oxidation mechanism of heterocyclic aromatic compounds, some aspects of the atmospheric chemistry of several alkyl derivatives of furan have been investigated. The aim of this work was to identify the products of the reactions of chlorine atoms with 2-methylfuran, 2-ethylfuran and 2,5-dimethylfuran. Experiments were performed in two different smog chambers at 296 ± 2 K and 1000 ± 20 mbar of synthetic air. The experimental investigation was carried out using in situ long-path FTIR absorption spectroscopy and both SPME-GC/FID-ECD and SPME-GC/MS as sampling and detection techniques. The major primary products from the addition reaction channel were 4-oxo-2-pentenoyl chloride and formaldehyde for the reactions of 2-methylfuran and 2,5-dimethylfuran; 4-oxo-2-hexenoyl chloride and acetaldehyde for the reaction of 2-ethylfuran and 5-chloro-2(5H)-furanone for the reactions of both 2-methylfuran and 2-ethylfuran. Other minor products were 4-oxo-2-pentenal, 4-oxo-2-hexenal and 3-hexene-2,5-dione for the 2-methylfuran, 2-ethylfuran and 2,5-dimethylfuran reactions, respectively. From the abstraction pathway, HCl, furfural, 2-acetylfuran, 5-methylfurfural, maleic anhydride and 5-hydroxy-2(5H)-furanone were detected. The formation of furfural, 2-acetylfuran and 5-methylfurfural confirmed the H-atom abstraction from the alkyl group of 2-methylfuran, 2-ethylfuran and 2,5-dimethylfuran, respectively. This mechanism was not observed in previous studies with OH and NO 3 radicals. A mechanism is proposed to explain the main reaction products observed. The observed products confirm that addition of Cl atoms to the double bond of the alkylfuran is the dominant reaction pathway.

  16. Electrocatalysis in alkaline media: Mechanistic studies of fuel cell reactions on well-defined model catalysts

    Science.gov (United States)

    Spendelow, Jacob S.

    Scanning tunneling microscopy and electrochemical techniques have been used to study several electrocatalytic reactions occurring on Pt(111) and Pt(111)/Ru surfaces in alkaline media. The reactions chosen, CO oxidation, methanol oxidation, and oxygen reduction, are relevant to direct methanol fuel cells (DMFCs). Each is relatively slow, and therefore requires high loading of precious metal catalysts to achieve sufficient fuel cell power density. The focus of these studies has been on determining mechanisms and limiting factors in each reaction. Special attention has been given to the role of adsorbed Ru and the role of Pt defects in enhancing catalytic activity. All defects were found to be more active than terraces for CO oxidation on Pt(111) in alkaline media at DMFC-relevant potentials. Step-typed defects enhance methanol dehydrogenation, but kink-type defects are inactive for this reaction. All defects are inactive for oxygen reduction. These observations can be explained in terms of the local geometric and electronic structure at defects. Adsorbate-adsorbate repulsions, with resultant effects on activation barriers, control the rates of CO oxidation, as well as methanol oxidation. In the case of CO, coverage-dependent CO-CO repulsions and OH-OH repulsions on defects both enhance kinetics. In the case of methanol, repulsive interactions with CO decrease the rate of methanol dehydrogenation, thus giving rise to the CO poisoning effect. Ru was found to promote both methanol dehydrogenation and CO oxidation on adjacent Pt sites. Ru enhances methanol dehydrogenation through two distinct ligand effects: it increases the intrinsic dehydrogenation activity of adjacent Pt sites, and it causes CO to diffuse away from these active sites, decreasing the CO poisoning effect. A Ru ligand effect also enhances CO oxidation by weakening the Pt-CO bond. Ru supplies adsorbed OH for bifunctional CO oxidation, but since Pt defects can also supply OH in alkaline media, the Ru

  17. Theoretical study of asymmetric super-rotors: Alignment and orientation

    Science.gov (United States)

    Omiste, Juan J.

    2018-02-01

    We report a theoretical study of the optical centrifuge acceleration of an asymmetric top molecule interacting with an electric static field by solving the time-dependent Schrödinger equation in the rigid rotor approximation. A detailed analysis of the mixing of the angular momentum in both the molecular and the laboratory fixed frames allows us to deepen the understanding of the main features of the acceleration process, for instance, the effective angular frequency of the molecule at the end of the pulse. For the case of the SO2 molecular super-rotor, we show numerically that it rotates around one internal axis and that its dynamics is confined to the plane defined by the polarization axis of the laser, in agreement with experimental findings. Furthermore, we consider the orientation patterns induced by the dc field, showing the characteristics of their structure as a function of the strength of the static field and the initial configuration of the fields.

  18. Theoretical Study of Irradiation Effects in Close Binaries

    Directory of Open Access Journals (Sweden)

    Srinivasa Rao, M.

    2009-06-01

    Full Text Available The effect of irradiation is studied in a close binary systemassuming that the secondary component is a point source, moving in a circularorbit. The irradiation effects are calculatedon the atmosphere of the primary component in a 3-dimensional Cartesiancoordinate geometry. In treating the reflection effect theoretically, the totalradiation $(S_mathrm{T}$ is obtained as the sum of the radiation of 1 the effect ofirradiation on the primary component which is calculated by using onedimensional rod model $(S_mathrm{r}$ and 2 the self radiation of the primarycomponent which is calculated by using the solution of radiative transferequation in spherical symmetry $(S_mathrm{s}$. The radiation field is estimated alongthe line of sight of the observer at infinity. It is shown how the radiationfield changes depending on the position of the secondary component.

  19. Electrochemistry of chlorogenic acid: experimental and theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Namazian, Mansoor [Department of Chemistry, Yazd University, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of)]. E-mail: namazian@yazduni.ac.ir; Zare, Hamid R. [Department of Chemistry, Yazd University, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of)

    2005-08-10

    Cyclic voltammetry, chronoamperometry and rotating disk electrode voltammetry as well as quantum chemical methods, are used for electrochemical study of chlorogenic acid, as an important biological molecule. The standard formal potential, diffusion coefficient, and heterogeneous electron transfer rate constant of chlorogenic acid in aqueous solution are investigated. Acidic dissociation constant of chlorogenic acid is also obtained. Quantum mechanical calculations on oxidation of chlorogenic acid in aqueous solution, using density functional theory are presented. The change of Gibbs free energy and entropy of oxidation of chlorogenic acid are calculated using thermochemistry calculations. The calculations in aqueous solution are carried out with the use of polarizable continuum solvation method. Theoretical standard electrode potential of chlorogenic acid is achieved to be 0.580 V versus standard calomel electrode (SCE) which is in agreement with the experimental value of 0.617 V obtained experimentally in this work. The difference is consistent with the values we previously reported for other quinone derivatives.

  20. Theoretical and Experimental Study of Plasmonic Polymer Solar Cells

    DEFF Research Database (Denmark)

    Mirsafaei, Mina; Adam, Jost; Madsen, Morten

    The organic bulk hetero-junction solar cell has remarkable advantages such as low cost, mechanical flexibility and simple process techniques. Recently, low-band gap photoactive materials have obtained a significant attention due to their potential to absorb a wider range of the solar spectrum...... to attain higher power conversion efficiencies. Many low-band gap photoactive materials, however, still show a relatively low external quantum efficiency of less than 60% [1]. One possible approach to improve the device performance is to increase the light absorption in the active layer. This may, amongst...... other approaches, be achieved by using nano- or micro-structures that trap light at specific wavelengths [2], or by using the localized surface plasmon resonance effect of metal nanoparticles in the devices. In this work, we theoretically studied planar polymer solar cell based on finite-difference time...

  1. Experimental and theoretical studies of buoyant-thermo capillary flow

    International Nuclear Information System (INIS)

    Favre, E.; Blumenfeld, L.; Soubbaramayer

    1996-01-01

    In the AVLIS process, uranium metal is evaporated using a high power electron gun. We have prior discussed the power balance equation in the electron beam evaporation process and pointed out, among the loss terms, the importance of the power loss due to the convective flow in the molten pool driven by buoyancy and thermo capillarity. An empirical formula has been derived from model experiments with cerium, to estimate the latter power loss and that formula can be used practically in engineering calculations. In order to complete the empirical approach, a more fundamental research program of theoretical and experimental studies have been carried out in Cea-France, with the objective of understanding the basic phenomena (heat transport, flow instabilities, turbulence, etc.) occurring in a convective flow in a liquid layer locally heated on its free surface

  2. A theoretical study on critical phenomena of magnetic soft modes

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Xiaoyan [Department of Mathematics, Shanghai University, 99 Shangda Road, 200444 Shanghai (China); Yang, Guohong [Department of Physics, Shanghai University, 99 Shangda Road, 200444 Shanghai (China); Shanghai Key Lab for Astrophysics, 100 Guilin Road, 200234 Shanghai (China); Yan, Ming, E-mail: myan@shu.edu.cn [Department of Physics, Shanghai University, 99 Shangda Road, 200444 Shanghai (China)

    2017-02-01

    Below a threshold magnetic field, domain structures in ferromagnetic samples may start to nucleate from the initially saturated state via either continuous or discontinuous phase transitions. Such processes are usually accompanied by the occurrence of soft spin-wave modes at the critical point. In this paper, we present a theoretical study on the critical phenomena of uniform soft modes in a macrospin model and spatially non-uniform ones in ferromagnetic thin films. The critical exponents of the mode frequency and its polarization are derived. The value is found to be equal to one half, which is directly related to the breaking of a reflection-symmetry in the phase transition. At the critical point, the soft mode becomes linearly polarized, which provides an additional measurable effect of the critical phenomena.

  3. Mechanistic Studies on the Use of Polygonum multiflorum for the Treatment of Hair Graying.

    Science.gov (United States)

    Han, Ming-Nuan; Lu, Jian-Mei; Zhang, Guang-Yuan; Yu, Jie; Zhao, Rong-Hua

    2015-01-01

    Polygonum multiflorum is a traditional Chinese medicine with a long history in hair growth promotion and hair blackening. The purpose of the study was to examine the effect and the mechanism of Polygonum multiflorum in hair blackening. C57BL/6 mice hair fade was induced with H2O2 and used in this research. Hair pigmentogenesis promotion activities of Polygonum Multiflorum Radix (PMR, raw crude drug), Polygonum Multiflorum Radix Preparata (PMRP, processed crude drug), and their major chemical constituent TSG were investigated. The regulation effects of several cytokines and enzymes such as POMC, α-MSH, MC1R, ASIP, MITF, TYR, TRP-1, and TRP-2 were investigated. PMR group gave out the most outstanding black hair among all groups with the highest contents of total melanin, α-MSH, MC1R, and TYR. Promotion of hair pigmentogenesis was slightly decreased after processing in the PMRP group. TSG as the major constituent of PMR showed weaker hair color regulation effects than both PMR and PMRP. PMR, but not PMRP, should be used to blacken hair. The α-MSH, MC1R, and TYR were the major targets in the medicinal use of PMR in hair graying. Chemical constituents other than TSG may contribute to the hair color regulation activity of PMR.

  4. Mechanistic Studies on the Use of Polygonum multiflorum for the Treatment of Hair Graying

    Directory of Open Access Journals (Sweden)

    Ming-Nuan Han

    2015-01-01

    Full Text Available Polygonum multiflorum is a traditional Chinese medicine with a long history in hair growth promotion and hair blackening. The purpose of the study was to examine the effect and the mechanism of Polygonum multiflorum in hair blackening. C57BL/6 mice hair fade was induced with H2O2 and used in this research. Hair pigmentogenesis promotion activities of Polygonum Multiflorum Radix (PMR, raw crude drug, Polygonum Multiflorum Radix Preparata (PMRP, processed crude drug, and their major chemical constituent TSG were investigated. The regulation effects of several cytokines and enzymes such as POMC, α-MSH, MC1R, ASIP, MITF, TYR, TRP-1, and TRP-2 were investigated. PMR group gave out the most outstanding black hair among all groups with the highest contents of total melanin, α-MSH, MC1R, and TYR. Promotion of hair pigmentogenesis was slightly decreased after processing in the PMRP group. TSG as the major constituent of PMR showed weaker hair color regulation effects than both PMR and PMRP. PMR, but not PMRP, should be used to blacken hair. The α-MSH, MC1R, and TYR were the major targets in the medicinal use of PMR in hair graying. Chemical constituents other than TSG may contribute to the hair color regulation activity of PMR.

  5. A mechanistic study of the uniform corrosion of copper in compacted clay-sand soil

    International Nuclear Information System (INIS)

    Litke, C.D.; Ryan, S.R.; King, F.

    1992-08-01

    The results of a study of the mechanism of uniform corrosion of copper under simulated nuclear fuel waste disposal conditions are presented. Evidence is given that suggests that the rate-controlling process is the transport of copper corrosion products away from the corroding surface. In the experiments described here, the copper diffused through a column of compacted clay-sand buffer. The properties of the buffer material, especially its ability to sorb copper species, are significant in determining the rate of uniform corrosion of copper. The evidence that copper diffusion is rate-controlling stems from the effect of γ-radiation on the tests. In the presence of γ-radiation, copper diffused farther along the column of compacted buffer material than in the unirradiated tests, but the corrosion rate was lower. These two effects can be best explained in terms of a slow copper-diffusion process. Irradiation is thought to reduce the extent of sorption of copper by the clay component of the buffer. This results in a more mobile copper species and a smaller interfacial flux of copper (i.e., a lower corrosion rate)

  6. Mechanistic Study of the Inhibitory Effect of Kaempferol on Uterine Fibroids In Vitro.

    Science.gov (United States)

    Li, Yanxia; Ding, Zhaoxia; Wu, Chuanzhong

    2016-12-08

    BACKGROUND This study examined the effect of kaempferol on uterine fibroids in vitro and the underlying mechanism, and investigated the potential of kaempferol as a clinical drug for the treatment of uterine fibroids. MATERIAL AND METHODS Uterine fibroid tissue and surrounding smooth muscle tissue were collected for primary culture. Different concentrations of kaempferol (12 μM, 24 μM, and 48 μM) were used to treat the cells for 24, 48, and 72 hours. Ethanol was used in the control group. A CCK-8 colorimetric assay was used to detect cell proliferation. Real-time PCR and immunoblot were used to detect estrogen receptor (ER), insulin-like growth factor-1 (IGF-1), and vascular endothelial growth factor (VEGF) levels in mRNA and protein. RESULTS The differences in proliferation at different time points and concentrations of kaempferol were statistically significant. The inhibitory effect of kaempferol on mRNA levels of ER and IGF, and protein levels of ER, VEGF, and IGF-1 were positively correlated with kaempferol concentration. Changes in kaempferol concentration showed no effect on VEGF mRNA expression. Treatment with kaempferol significantly lowered myocardin levels in uterine fibroid tissue compared to normal uterine smooth muscle (PKaempferol might be used for clinical treatment of uterine fibroids due to its inhibitory effect on the proliferation of uterine fibroids cells.

  7. MECHANISTICAL STUDIES ON THE FORMATION AND NATURE OF THE 'XCN' (OCN-) SPECIES IN INTERSTELLAR ICES

    International Nuclear Information System (INIS)

    Bennett, C. J.; Jones, B.; Knox, E.; Perry, J.; Kim, Y. S.; Kaiser, R. I.

    2010-01-01

    We conducted laboratory experiments on the interaction of ionizing radiation in the form of energetic electrons with interstellar model ices to investigate the nature and possible routes to form the 'XCN' species as observed at 4.62 μm (2164 cm -1 ) in the interstellar medium. Our laboratory experiments provided compelling evidence that the isocyanide ion (OCN - ) presents the carrier of the 'XCN' feature in interstellar ices. Most importantly, the studies exposed-based on kinetic fits of the temporal profiles of important reactants, intermediates, and products-that two formation mechanisms can lead to the production of the isocyanide ion (OCN - ) in low-temperature interstellar ices. In carbon monoxide-ammonia ices, unimolecular decomposition of ammonia leads to reactive NH 2 and NH radical species, which in turn can react with neighboring carbon monoxide to form ultimately the isocyanide ion (OCN - ); this process also involves a fast proton transfer to a base molecule in the surrounding ice. Second, cyanide ions (CN - )-formed via unimolecular decomposition of methylamine (CH 3 NH 2 ) via a methanimine (CH 2 NH) intermediate-can react with suprathermal oxygen atoms forming the isocyanide ion (OCN - ). We also discuss that the isocyanide ion (OCN - ) can be used as a molecular tracer to determine, for instance, the development stage of young stellar objects and also the chemical history of ices processed by ionizing radiation.

  8. Mechanistic insights into the vascular effects of blueberries: Evidence from recent studies.

    Science.gov (United States)

    Cutler, Brett Ronald; Petersen, Chrissa; Anandh Babu, Pon Velayutham

    2017-06-01

    Cardiovascular disease is the leading cause of death in the United States. Dietary habits influence a variety of cardiovascular complications such as peripheral artery disease, heart failure, and kidney disease. We along with others have previously reported the cardiovascular beneficial effects of dietary flavonoids. Anthocyanins, one class of flavonoids widely available in berries, have recently drawn wide scientific attention because of their diverse health benefits. Epidemiological, clinical, and animal studies indicate that blueberry anthocyanins exert protection against cardiovascular complications by acting on multiple targets in the vascular system. These include activating endothelial nitric oxide synthase signaling, reducing oxidative stress, improving inflammatory pathways, and ameliorating dyslipidemia. Anthocyanins are extensively metabolized in humans suggesting that their vascular benefits are likely mediated by their circulating metabolites. However, the bioactivities of blueberry metabolites are unknown. Evaluating the bioactivities of metabolites, analyzing their structure-activity relationship, and well-designed human trials are needed to understand the potential vascular effects of blueberries and their metabolites. Understanding the vascular effects will provide a solid scientific foundation to recommend blueberries to improve vascular health. This review highlights the recent developments in the understanding of the vascular effects of blueberries with special emphasis on the molecular mechanisms involved. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Mechanistic Study of Silver Nanoparticle's Synthesis by Dragon's Blood Resin Ethanol Extract and Antiradiation Activity.

    Science.gov (United States)

    Hasan, Murtaza; Iqbal, Javed; Awan, Umer; Saeed, Yasmeen; Ranran, Yuan; Liang, Yanli; Dai, Rongji; Deng, Yulin

    2015-02-01

    Biological synthesis of nanoparticles is best way to avoid exposure of hazardous materials as compared to chemical manufacturing process which is a severe threat not only to biodiversity but also to environment. In present study, we reported a novel method of finding antiradiation compounds by bioreducing mechanism of silver nanoparticles formation using 50% ethanol extract of Dragons blood, a famous Chinese herbal plant. Color change during silver nanoparticles synthesis was observed and it was confirmed by ultra violet (UV) visible spectroscopy at wave length at 430 nm after 30 min of reaction at 60 °C. Well dispersed round shaped silver nanoparticles with approximate size (4 nm to 50 nm) were measured by TEM and particle size analyser. Capping of biomolecules on Ag nanoparticles was characterized by FTIR spectra. HPLC analysis was carried out to find active compounds in the extract. Furthermore, antiradiation activity of this extract was tested by MTT assay in vitro after incubating the SH-SY5Y cells for 24 h at 37 °C. The results indicate that presence of active compounds in plant extract not only involves in bioreduction process but also shows response against radiation. The dual role of plant extract as green synthesis of nanoparticles and exhibit activity against radiation which gives a new way of fishing out active compounds from complex herbal plants.

  10. Synthesis of nickel nanoparticles by hydrazine reduction: mechanistic study and continuous flow synthesis

    International Nuclear Information System (INIS)

    Eluri, Ravi; Paul, Brian

    2012-01-01

    The continuous synthesis of nickel nanoparticles (NiNPs) in a static microchannel T-mixer by the reduction of NiCl 2 ·6H 2 O in the presence of ethylene glycol without a stabilizing/capping agent was investigated. The nanoparticles were formed in accordance with the modified polyol process with hydrazine used as a reducing agent and NaOH as a catalyst for nanoparticle formation. The reaction mechanism for NiNP formation was investigated in batch with the help of Fourier transform infrared spectroscopy and X-ray diffraction (XRD) techniques. Parameters were found for reducing reaction times from 60 to 1 min. The effects of temperature (60–120 °C) and NaOH concentration (0.1 and 0.5 M) on batch-processed particle characteristics were also studied using XRD, transmission electron microscope and electron microprobe analysis. Average particle size was reduced from 9.2 ± 2.9 to 5.4 ± 0.9 nm at higher temperature and NaOH concentration. Adaptation of this chemistry to a static microchannel T-mixer for continuous synthesis resulted in smooth, spherical particles. Increases in the reaction temperature from 120 to 130 °C resulted in a narrow size distribution of 5.3 ± 1 nm and also resulted in magnetic properties of 5.1 emu/g (saturation magnetization), 1.1 emu/g (remanent magnetization), and 62 Oe (coercivity).

  11. Mechanistic Studies of Anti-Hyperpigmentary Compounds: Elucidating Their Inhibitory and Regulatory Actions

    Directory of Open Access Journals (Sweden)

    Rosanna Y. Y. Lam

    2014-08-01

    Full Text Available Searching for depigmenting agents from natural sources has become a new direction in the cosmetic industry as natural products are generally perceived as relatively safer. In our previous study, selected Chinese medicines traditionally used to treat hyperpigmentation were tested for anti-hyperpigmentary effects using a melan-a cell culture model. Among the tested chemical compounds, 4-ethylresorcinol, 4-ethylphenol and 1-tetradecanol were found to possess hypopigmentary effects. Western blot analysis, reverse transcriptase polymerase chain reaction (RT-PCR, cyclic adenosine monophosphate (cAMP assay, protein kinase A (PKA activity assay, tyrosinase inhibition assay and lipid peroxidation inhibition assay were performed to reveal the underlying cellular and molecular mechanisms of the hypopigmentary effects. 4-Ethylresorcinol and 4-ethylphenol attenuated mRNA and protein expression of tyrosinase-related protein (TRP-2, and possessed antioxidative effect by inhibiting lipid peroxidation. 1-Tetradecanol was able to attenuate protein expression of tyrosinase. The hypopigmentary actions of 4-ethylresorcinol, 4-ethylphenol and 1-tetradecanol were associated with regulating downstream proteins along the PKA pathway. 4-Ethylresorcinol was more effective in inhibiting melanin synthesis when compared to 4-ethylphenol and 1-tetradecanol.

  12. Mechanistic studies of pericardial edema in early life stages (ELS) of medaka (Oryzias latipes)

    Energy Technology Data Exchange (ETDEWEB)

    Villalobos, S.A.; Fan, T.W.M.; Higashi, R.M.; Hinton, D.E. [Univ. of California, Davis, CA (United States)

    1995-12-31

    Pericardial edema (PE), a manifestation of developmental toxicity in fish ELS, may compromise stock recruitment and survival. However, the mechanism underlying this common lesion is unknown. Possible mechanisms for PE in ELS of medaka were studied by metabolic and morphologic methods. In the laboratory, medaka embryos readily develop PE after brief exposure to dioxin, trichloroethylene (TCE) soot extract, or thiobencarb. Histopathological analyses, regardless of agent, indicated widespread edema without cellular infiltrates in pericardial and peritoneal cavities and in subepithelial spaces of skin. Additionally, endothelia of sinus venosus and adjacent atrium were enlarged. Walls of dilated sinoatrial compartments showed subendothelial fluid accumulation. Ethoxyresorufin O-deethylase activity (indicator of CYPL A induction), considerably higher in embryos exposed to dioxin and TCE soot, was suppressed by thiobencarb. In vivo {sup 31}P nuclear magnetic resonance (NMR) spectroscopy of living embryos (pregastrula through hatching) previously treated with thiobencarb, showed a temporary depression of ATP and phosphocreatine levels, with an apparent transient alkalinization in intracellular (possibly yolk sac) pH. Results indicate that induction of CYP1A is not a requirement for development of PE, and that ionic imbalances and/or metabolic disorders following exposure may be causative factor(s).

  13. Mechanistic studies on reactivities of organometallic macrocyclic complexes of chromium and cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Shu.

    1990-12-10

    Reaction pathways leading to the formation and cleavage of a transition metal-carbon bond at various oxidation states of the metal occupy a central position in understanding many enzymatic reactions and designing catalysts. The report is divided into six parts that (1) focus on the homolysis vs heterolysis of a C-Cr(III) bond, (2) describes a unique chain reaction and a S{sub E}2 reaction I{sub 2} and RCrL{sup 2+}, (3) concerns the oxidation of organochromium(III) complexes by dihalide and pseudo-dihalide radical anions generated by pulse radiolysis, (4) concentrates on the oxidation mechanism of RCr(H{sub 2}O){sup 2+} and the fate of RCr(H{sub 2}O){sup 3+} as well as the corresponding reduction potentials, (5) extends study of organocobalt complexes with attention to reduction induced cleavages of a transition metal-carbon bond, and (6) describes the crystallization of ((CH{sub 3}){sub 4}N)(Co(dmgBF{sub 2}){sub 2}py) and reports its molecular structure as determined by x-ray diffraction. 182 refs., 25 figs., 16 tabs. (BM)

  14. Mechanistic studies on reactivities of organometallic macrocyclic complexes of chromium and cobalt

    International Nuclear Information System (INIS)

    Shi, Shu.

    1990-01-01

    Reaction pathways leading to the formation and cleavage of a transition metal-carbon bond at various oxidation states of the metal occupy a central position in understanding many enzymatic reactions and designing catalysts. The report is divided into six parts that (1) focus on the homolysis vs heterolysis of a C-Cr(III) bond, (2) describes a unique chain reaction and a S E 2 reaction I 2 and RCrL 2+ , (3) concerns the oxidation of organochromium(III) complexes by dihalide and pseudo-dihalide radical anions generated by pulse radiolysis, (4) concentrates on the oxidation mechanism of RCr(H 2 O) 2+ and the fate of RCr(H 2 O) 3+ as well as the corresponding reduction potentials, (5) extends study of organocobalt complexes with attention to reduction induced cleavages of a transition metal-carbon bond, and (6) describes the crystallization of [(CH 3 ) 4 N][Co(dmgBF 2 ) 2 py] and reports its molecular structure as determined by x-ray diffraction. 182 refs., 25 figs., 16 tabs. (BM)

  15. Mechanistic Study on the Degradation of Thermal Barrier Coatings Induced by Volcanic Ash Deposition

    Science.gov (United States)

    Arai, Masayuki

    2017-08-01

    Thermal stress generated on thermal barrier coatings (TBCs) by volcanic ash (VA) deposition was assessed measuring the tip deflection of a multilayered beam structure as a function of temperature. The TBC in this study was deposited onto the surface of a blade utilized in a land-based gas turbine which is composed of 8 wt.%Y2O3-ZrO2/CoNiCrAlY on a Ni-based superalloy. The VA-deposited TBC sample was heated at 1453 K, and the effect of VA deposition on TBC delamination was examined in comparison with a TBC sample without VA deposition as a reference. On the basis of the VA attack damage mechanism which was investigated via the tip deflection measurement and a comprehensive microstructure examination, a damage-coupled constitutive model was proposed. The proposed model was based on the infiltration of the molten VA inside pores and phase transformations of yttria -tabilized zirconia in the TBC system. The numerical analysis results, which were simulated utilizing the finite element code installing the developed constitutive model, showed us that VA attack on the TBC sample induced near-interfacial cracks because of a significant increasing in the coating stress.

  16. Structural and Mechanistic Studies of Pesticin, a Bacterial Homolog of Phage Lysozymes*

    Science.gov (United States)

    Patzer, Silke I.; Albrecht, Reinhard; Braun, Volkmar; Zeth, Kornelius

    2012-01-01

    Yersinia pestis produces and secretes a toxin named pesticin that kills related bacteria of the same niche. Uptake of the bacteriocin is required for activity in the periplasm leading to hydrolysis of peptidoglycan. To understand the uptake mechanism and to investigate the function of pesticin, we combined crystal structures of the wild type enzyme, active site mutants, and a chimera protein with in vivo and in vitro activity assays. Wild type pesticin comprises an elongated N-terminal translocation domain, the intermediate receptor binding domain, and a C-terminal activity domain with structural analogy to lysozyme homologs. The full-length protein is toxic to bacteria when taken up to the target site via the outer or the inner membrane. Uptake studies of deletion mutants in the translocation domain demonstrate their critical size for import. To further test the plasticity of pesticin during uptake into bacterial cells, the activity domain was replaced by T4 lysozyme. Surprisingly, this replacement resulted in an active chimera protein that is not inhibited by the immunity protein Pim. Activity of pesticin and the chimera protein was blocked through introduction of disulfide bonds, which suggests unfolding as the prerequisite to gain access to the periplasm. Pesticin, a muramidase, was characterized by active site mutations demonstrating a similar but not identical residue pattern in comparison with T4 lysozyme. PMID:22593569

  17. Mechanistic Study of Adsorption of Acid Orange-7 over Aluminum Oxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ekta Khosla

    2013-01-01

    Full Text Available The adsorption behavior of acid orange-7 (AO-7 on aluminum oxide nanoparticles (ANP generated by sol-gel method has been investigated to understand the physicochemical process involved and to explore the potential use of nano particles in textile effluent treatment and management. The results revealed that ANP can remove AO-7 dye up to 97.6 mg/g at 303 K. The adsorption process is found to be pH dependent and the optimum pH obtained is 2.0. The equilibrium was established in 1 h. Langmuir, Freundlich, and Temkin Isotherm models were applied on the system. Scanning electron microscopic analysis reveals eye-catching nanoporous morphology of the material. The results of FTIR spectroscopy reveal that the process is electrostatic complexation mechanism driven. XRD studies revealed nanocrystalline structure of ANP. BET surface area measurement suggests high pore volume and surface area of adsorbent. The kinetic measurements suggest pseudo-second-order kinetic processes. The thermodynamic measurements suggest that all processes are endothermic accompanied with negative ΔG° and positive ΔS°, ΔH°.

  18. Toughening of nanocelluose/PLA composites via bio-epoxy interaction: Mechanistic study

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Xiangtao [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bocharova, Vera [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tekinalp, Halil L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Cheng, Shiwang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kisliuk, Alexander [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sokolov, Alexei P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kunc, Vlastimil [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Peter, William H. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ozcan, Soydan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)

    2017-11-07

    While PLA possesses modest to good strength and stiffness, broader application is hindered by its brittle nature. The aim of this study was to develop strong and tough polymeric materials from renewable biomaterials and understand the underlying interactions and mechanisms. Cellulose nanofibrils (CNFs) and epoxidized soybean oil (ESO) were compounded with poly(lactic acid) (PLA) to create a PLA-CNF-ESO tertiary nanocomposite system. Tensile and dynamic mechanical analyses were performed to see how variations in ESO and CNF content affect mechanical properties such as strength, modulus, ductility, and toughness. It was found that at low CNF levels (10 wt %) the addition of ESO can improve the ductility of the nanocomposites 5- to 10-fold with only slight losses in strength and modulus, while at higher CNF levels (20 and 30 wt %), ESO exhibited little effect on mechanical properties, possibly due to percolation of CNFs in the matrix, dominating stress transfer. Therefore, it is important to optimize CNF and ESO amounts in composites to achieve materials with both high strength and high toughness. As a result, efforts have been made to understand the underlying mechanisms of the mechanical behavior of one class of these composites via thermal, dynamic mechanical, morphological, and Raman analyses.

  19. A structural and mechanistic study of π-clamp-mediated cysteine perfluoroarylation.

    Science.gov (United States)

    Dai, Peng; Williams, Jonathan K; Zhang, Chi; Welborn, Matthew; Shepherd, James J; Zhu, Tianyu; Van Voorhis, Troy; Hong, Mei; Pentelute, Bradley L

    2017-08-11

    Natural enzymes use local environments to tune the reactivity of amino acid side chains. In searching for small peptides with similar properties, we discovered a four-residue π-clamp motif (Phe-Cys-Pro-Phe) for regio- and chemoselective arylation of cysteine in ribosomally produced proteins. Here we report mutational, computational, and structural findings directed toward elucidating the molecular factors that drive π-clamp-mediated arylation. We show the significance of a trans conformation prolyl amide bond for the π-clamp reactivity. The π-clamp cysteine arylation reaction enthalpy of activation (ΔH ‡ ) is significantly lower than a non-π-clamp cysteine. Solid-state NMR chemical shifts indicate the prolyl amide bond in the π-clamp motif adopts a 1:1 ratio of the cis and trans conformation, while in the reaction product Pro3 was exclusively in trans. In two structural models of the perfluoroarylated product, distinct interactions at 4.7 Å between Phe1 side chain and perfluoroaryl electrophile moiety are observed. Further, solution 19 F NMR and isothermal titration calorimetry measurements suggest interactions between hydrophobic side chains in a π-clamp mutant and the perfluoroaryl probe. These studies led us to design a π-clamp mutant with an 85-fold rate enhancement. These findings will guide us toward the discovery of small reactive peptides to facilitate abiotic chemistry in water.

  20. Mechanistic study and modeling of radionuclides retention by the hydrated calcium silicates (HCS) of cements

    International Nuclear Information System (INIS)

    Pointeau, I.

    2000-09-01

    This work attempts to investigate the modelling of radioisotopes (Cs + , Pb 2+ , Eu 3+ ) immobilization in cement matrix, in the frame of the design of engineered barrier of a deep radwaste repository. The model development concept consists of three major steps: - surface chemistry modelling of the calcium silicate hydrate CSH, used to simulate hydrated cement behaviour; - solid analysis of the batch sorption experiments: identification of the uptake mechanism; - both previous steps are used, with isotherm data, in the modelling of the radioisotopes immobilization in the CSH matrix. Final results: (all modelling are available for all the range of studied Ca/Si ratios and have been validated with predictive calculations). - A thermodynamic modelling of the CSH surface chemistry has been developed. The labile calcium and proton sorption constants on silanol sites (>SiOH) have been extracted. - Cs + is sorbed on two sites. The silanol site (weak site) has a high site density (10 sites.nm -2 ), which accounts for the CSH unsaturation in high [CS + ]. A strong site is also identified. - Pb 2+ immobilization in CSH matrix is modelled with surface equilibria and solubility equilibrium. - Eu 3+ fixation has been investigated with solid analysis: Site-Selective anti Time-Resolved Luminescence Spectroscopy, XPS and SEM-EDS. Eu 3+ thus does not precipitate in CSH water but is sorbed on the CSH surface (high hydroxylated environment). Europium is also (minority site) inserted in the CSH framework. (author)

  1. Mechanistic studies of the metabolic chiral inversion of (R)-ibuprofen in humans

    International Nuclear Information System (INIS)

    Baillie, T.A.; Adams, W.J.; Kaiser, D.G.; Olanoff, L.S.; Halstead, G.W.; Harpootlian, H.; Van Giessen, G.J.

    1989-01-01

    The metabolic chiral inversion of R-(-)-ibuprofen has been studied in human subjects by means of specific deuterium labeling and stereoselective gas chromatography-mass spectrometry methodology. After simultaneous p.o. administration of a mixture of R-(-)-ibuprofen (300 mg) and R-(-)-[3,3,3-2H3]ibuprofen (304 mg) to four adult male volunteers, the enantiomeric composition and deuterium content of the drug in serum, and of the drug and its principal metabolites in urine, were followed over a period of 24 hr. The results of these analyses indicated that: (1) conversion of R-(-)- to S-(+)-ibuprofen takes place with complete retention of deuterium at the beta-methyl (C-3) position; (2) chiral inversion of R-(-)-[2H3]ibuprofen is not subject to a discernible deuterium isotope effect; and (3) replacement of the beta-methyl hydrogen atoms by deuterium has no effect on any of the serum pharmacokinetic parameters for R-(-)- or S-(+)-ibuprofen. These data indicate that the process whereby R-(-)-ibuprofen undergoes metabolic inversion in human subjects does not involve 2,3-dehydroibuprofen as an intermediate, and that the underlying mechanism cannot, therefore, entail a desaturation/reduction sequence

  2. Transcranial direct current stimulation to lessen neuropathic pain after spinal cord injury: a mechanistic PET study.

    Science.gov (United States)

    Yoon, Eun Jin; Kim, Yu Kyeong; Kim, Hye-Ri; Kim, Sang Eun; Lee, Youngjo; Shin, Hyung Ik

    2014-01-01

    It is suggested that transcranial direct current stimulation (tDCS) can produce lasting changes in corticospinal excitability and can potentially be used for the treatment of neuropathic pain. However, the detailed mechanisms underlying the effects of tDCS are unknown. We investigated the underlying neural mechanisms of tDCS for chronic pain relief using [(18)F]-fluorodeoxyglucose positron emission tomography ([(18)F]FDG-PET). Sixteen patients with neuropathic pain (mean age 44.1 ± 8.6 years, 4 females) due to traumatic spinal cord injury received sham or active anodal stimulation of the motor cortex using tDCS for 10 days (20 minutes, 2 mA, twice a day). The effect of tDCS on regional cerebral glucose metabolism was evaluated by [(18)F]FDG-PET before and after tDCS sessions. There was a significant decrease in the numeric rating scale scores for pain, from 7.6 ± 0.5 at baseline to 5.9 ± 1.8 after active tDCS (P = .016). We found increased metabolism in the medulla and decreased metabolism in the left dorsolateral prefrontal cortex after active tDCS treatment compared with the changes induced by sham tDCS. Additionally, an increase in metabolism after active tDCS was observed in the subgenual anterior cingulate cortex and insula. The results of this study suggest that anodal stimulation of the motor cortex using tDCS can modulate emotional and cognitive components of pain and normalize excessive attention to pain and pain-related information.

  3. Mechanistic studies of Gemcitabine-loaded nanoplatforms in resistant pancreatic cancer cells

    International Nuclear Information System (INIS)

    Papa, Anne-Laure; Basu, Sudipta; Sengupta, Poulomi; Banerjee, Deboshri; Sengupta, Shiladitya; Harfouche, Rania

    2012-01-01

    Pancreatic cancer remains the deadliest of all cancers, with a mortality rate of 91%. Gemcitabine is considered the gold chemotherapeutic standard, but only marginally improves life-span due to its chemical instability and low cell penetrance. A new paradigm to improve Gemcitabine’s therapeutic index is to administer it in nanoparticles, which favour its delivery to cells when under 500 nm in diameter. Although promising, this approach still suffers from major limitations, as the choice of nanovector used as well as its effects on Gemcitabine intracellular trafficking inside pancreatic cancer cells remain unknown. A proper elucidation of these mechanisms would allow for the elaboration of better strategies to engineer more potent Gemcitabine nanotherapeutics against pancreatic cancer. Gemcitabine was encapsulated in two types of commonly used nanovectors, namely poly(lactic-co-glycolic acid) (PLGA) and cholesterol-based liposomes, and their physico-chemical parameters assessed in vitro. Their mechanisms of action in human pancreatic cells were compared with those of the free drug, and with each others, using cytotoxity, apoptosis and ultrastructural analyses. Physico-chemical analyses of both drugs showed high loading efficiencies and sizes of less than 200 nm, as assessed by dynamic light scattering (DLS) and transmission electron microscopy (TEM), with a drug release profile of at least one week. These profiles translated to significant cytotoxicity and apoptosis, as well as distinct intracellular trafficking mechanisms, which were most pronounced in the case of PLGem showing significant mitochondrial, cytosolic and endoplasmic reticulum stresses. Our study demonstrates how the choice of nanovector affects the mechanisms of drug action and is a crucial determinant of Gemcitabine intracellular trafficking and potency in pancreatic cancer settings

  4. Mechanistic studies of nitrations and oxidations in solutions of dinitrogen pentaoxide in nitric acid

    Energy Technology Data Exchange (ETDEWEB)

    Willmer, R.F.

    1992-01-01

    Mechanisms of nitrations in solutions of dinitrogen pentaoxide in nitric acid of 1,2,4-trichloro-5-nitrobenzene and 1,2-dichloro-4-nitrobenzene have been proposed. The kinetics and products of the nitration, in the title medium, of substantially deactivated benzoic acids and benzaldehydes have been investigated. Kinetics of nitration of some substituted benzoic acids in nitric acid solutions containing dinitrogen pentaoxide or nitronium trifluoro-methanesulphonate (nitronium triflate) have been compared. Rate coefficients for reactions in dinitrogen pentaoxide solutions were generally similar to those from nitronium triflate solutions of the same estimated nitronium ion concentration. Yields of aromatic products of nitration of some benzoic acid derivatives in the nitric acid solutions have been determined. Nitrodecarboxylation of 4-fluorobenzoic acid occurs as a result of nitronium ion attach at C(1). The competition between oxidation to the corresponding benzoic acid and nitration in the aromatic ring of some substituted benzaldehydes has been probed by kinetic and product studies. 4-Carboxybenzaldehyde is nitrated but more deactivated substrates are predominantly oxidized. Rapid reversible gem-dinitrate formation occurs in concentrated dinitrogen pentaoxide solutions. The equilibrium extent of formation of [alpha]-deuterio-(4-nitropheny)-dinitratomethane from [alpha]-deuterio-4-nitrobenzaldehyde is reported. 4-nitrobenzaldehyde and the gem-dinitrate are oxidized in processes in which [alpha]-hydrogen loss is at least partially rate determining. The relative rates of oxidation in nitronium triflate solutions suggest that the [alpha]-hydrogen is removed as a hydride ion in that medium. There is evidence for the intrusion of a radical mechanism of nitration in concentrated solutions of dinitrogen pentaoxide. (4-Nitrophenyl)dinitratomethane was produced on the addition of 4-nitrobenzaldehyde to a solution of dinitrogen pentaoxide in dichloromethane.

  5. Mechanistic studies with solubilized rat liver steroid 5 alpha-reductase: Elucidation of the kinetic mechanism

    International Nuclear Information System (INIS)

    Levy, M.A.; Brandt, M.; Greway, A.T.

    1990-01-01

    A solubilized preparation of steroid 5 alpha-reductase from rat liver has been used in studies focused toward an understanding of the kinetic mechanism associated with enzyme catalysis. From the results of analyses with product and dead-end inhibitors, a preferentially ordered binding of substrates and release of products from the surface of the enzyme is proposed. The observations from these experiments were identical with those using the steroid 5 alpha-reductase activity associated with rat liver microsomes. The primary isotope effects on steady-state kinetic parameters when [4S-2H]NADPH was used also were consistent with an ordered kinetic mechanism. Normal isotope effects were observed for all three kinetic parameters (Vm/Km for both testosterone and NADPH and Vm) at all substrate concentrations used experimentally. Upon extrapolation to infinite concentration of testosterone, the isotope effect on Vm/Km for NADPH approached unity, indicating that the nicotinamide dinucleotide phosphate is the first substrate binding to and the second product released from the enzyme. The isotope effects on Vm/Km for testosterone at infinite concentration of cofactor and on Vm were 3.8 +/- 0.5 and 3.3 +/- 0.4, respectively. Data from the pH profiles of these three steady-state parameters and the inhibition constants (1/Ki) of competitive inhibitors versus both substrates indicate that the binding of nicotinamide dinucleotide phosphate involves coordination of its anionic 2'-phosphate to a protonated enzyme-associated base with an apparent pK near 8.0. From these results, relative limits have been placed on several of the internal rate constants used to describe the ordered mechanism of the rat liver steroid 5 alpha-reductase

  6. Combining Solvent Isotope Effects with Substrate Isotope Effects in Mechanistic Studies of Alcohol and Amine Oxidation by Enzymes*

    Science.gov (United States)

    Fitzpatrick, Paul F.

    2014-01-01

    Oxidation of alcohols and amines is catalyzed by multiple families of flavin-and pyridine nucleotide-dependent enzymes. Measurement of solvent isotope effects provides a unique mechanistic probe of the timing of the cleavage of the OH and NH bonds, necessary information for a complete description of the catalytic mechanism. The inherent ambiguities in interpretation of solvent isotope effects can be significantly decreased if isotope effects arising from isotopically labeled substrates are measured in combination with solvent isotope effects. The application of combined solvent and substrate (mainly deuterium) isotope effects to multiple enzymes is described here to illustrate the range of mechanistic insights that such an approach can provide. PMID:25448013

  7. Mechanistic study of the toxicity of ionizing radiation in Daphnia magna

    Energy Technology Data Exchange (ETDEWEB)

    Parisot, F.; Alonzo, F. [Institut de Radioprotection et de Surete Nucleaire, IRSN/PRP-ENV/SERIS/LECO, Laboratoire d' Ecotoxicologie des Radionucleides, Cadarache (France); Bourdineaud, J.P. [UMR CNRS 5805 EPOC - OASU Station Marine d' Arcachon Universite Bordeaux 1, Arcachon (France); Poggiale, J.C. [Mediterranean Institute of Oceanography - MIO - UMR 7294 Pytheas Institute - OSU, Aix-Marseille University, Marseille (France)

    2014-07-01

    In the last decade, the ecological impact of ionizing radiation has emerged as a growing scientific concern for ecosystems protection. However, the assessment of potential radiological effects on the environment is hampered by both a gap of available scientific data and a lack in proven methods. Understanding how ionizing radiation affects wildlife at biologically and ecologically relevant scales is a major issue in environmental protection. This issue is one of the objectives of the Strategic Research Agenda (SRA) developed in the framework of the European program STAR (Strategy for Allied Radioecology). In this context, the present PhD project aims to evaluate chronic effects of external Cs-137 gamma radiation at low doses on a representative species of aquatic ecosystems, the cladoceran crustacean Daphnia magna. More precisely, the objectives of this study are to evaluate multi-generational effects of irradiation on: (i) genotoxic effects and their potential consequences on survival, somatic growth and fecundity, (ii) the energy budget and (iii) the population dynamics of Daphnia. An experimental design was developed to expose daphnids to low doses of ionizing radiation ranging from 0,008 to 32 mGy.h{sup -1} across 3 successive generations (75 days). DNA damages were assessed using random amplified polymorphic DNA and real time PCR (RAPD - PCR). Effects on survival, somatic growth and fecundity were monitored for 21-25 days in each generation, from hatching to release of brood 5. Our aim is to: examine a potential correlation between molecular (DNA) damage and effects observed at the individual level (survival, somatic growth and fecundity) across generations and test the suitability of DNA damage as an early indice of future trans-generational effects. As a future perspective, individual and molecular effects data will be analysed using a DEBtox model (Dynamic Energy Budget Applied to Toxicology) in order to identify the metabolic modes of action of ionizing

  8. Mechanistic Studies of the Spore Photoproduct Lyase (SPL) via a Single Cysteine Mutation

    Science.gov (United States)

    Yang, Linlin; Lin, Gengjie; Nelson, Renae S.; Jian, Yajun; Telser, Joshua; Li, Lei

    2012-01-01

    5-thyminyl-5,6-dihydrothymine (also called spore photoproduct or SP) is the exclusive DNA photo-damage product in bacterial endospores. It is repaired by a radical SAM (S-adenosylmethionine) enzyme, the spore photoproduct lyase (SPL), at the bacterial early germination phase. Our previous studies proved that SPL utilizes the 5′-dA• generated by SAM cleavage reaction to abstract the H6proR atom to initiate the SP repair process. The resulting thymine allylic radical was suggested to take an H atom from an unknown protein source, most likely the cysteine 141. Here we show that C141 can be readily alkylated in the native SPL by iodoacetamide treatment, suggesting that it is accessible to the TpT radical. SP repair by the SPL C141A mutant yields TpTSO2− and TpT simultaneously from the very beginning of the reaction; no lag phase is observed for the TpTSO2− formation. Should any other protein residue serve as the H donor, its presence would result in TpT as the major product at least for the first enzyme turnover. These observations provide strong evidence to support C141 as the direct H atom donor. Moreover, due to the lack of this intrinsic H donor, the C141A mutant produces TpT via an unprecedented thymine cation radical reduction (proton coupled electron transfer) process, contrasting to the H atom transfer mechanism in the WT SPL reaction. The C141A mutant repairs SP at a rate which is ~3-fold slower than the WT enzyme. Formation of TpTSO2− and TpT exhibit a Vmax deuterium kinetic isotope effect (KIE) of 1.7 ± 0.2 respectively, which is smaller than the DVmax KIE of 2.8 ± 0.3 determined in the WT SPL reaction. These findings suggest that removing the intrinsic H atom donor disturbs the rate-limiting process in the enzyme catalysis. As expected, the pre-reduced C141A mutant only supports ~ 0.4 turnover, which is in sharp contrast to the > 5 turnovers exhibited by the WT SPL reaction, suggesting that the enzyme catalytic cycle (SAM regeneration) is

  9. Theoretical study of diaquamalonatozinc (II) single crystal for ...

    Indian Academy of Sciences (India)

    The aim of the present paper is to employ theoretical methods to investigate the zero field splitting (ZFS) parameter and to investigate the position of the dopant in the host. These theoretical calculations have been compared with the empirical results. The superposition model (SPM)with themicroscopic spin-Hamiltonian ...

  10. Theoretical Studies of Elementary Hydrocarbon Species and Their Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Wesley D. [University of Georgia, Department of Chemistry and Center for Computational Quantum Chemistry; Schaefer, Henry F. [University of Georgia, Center for Computational Quantum Chemistry

    2018-04-08

    The research program supported by this DOE grant carried out both methodological development and computational applications of first-principles theoretical chemistry based on quantum mechanical wavefunctions, as directed toward understanding and harnessing the fundamental chemical physics of combustion. To build and refine the world’s database of thermochemistry, spectroscopy, and chemical kinetics, predictive and definitive computational methods are needed that push the envelope of modern electronic structure theory. The application of such methods has been made to gain comprehensive knowledge of the paradigmatic reaction networks by which the n- and i-propyl, t-butyl, and n-butyl radicals are oxidized by O2. Numerous ROO and QOOH intermediates in these R + O2 reaction systems have been characterized along with the interconnecting isomerization transition states and the barriers leading to fragmentation. Other combustion-related intermediates have also been studied, including methylsulfinyl radical, cyclobutylidene, and radicals derived from acetaldehyde and vinyl alcohol. Theoretical advances have been achieved and made available to the scientific community by implementation into PSI4, an open-source electronic structure computer package emphasizing automation, advanced libraries, and interoperability. We have pursued the development of universal explicitly correlated methods applicable to general electronic wavefunctions, as well as a framework that allows multideterminant reference functions to be expressed as a single determinant from quasiparticle operators. Finally, a rigorous analytical tool for correlated wavefunctions has been created to elucidate dispersion interactions, which play essential roles in many areas of chemistry, but whose effects are often masked and enigmatic. Our research decomposes and analyzes the coupled-cluster electron correlation energy in molecular systems as a function of interelectronic distance. Concepts

  11. Polyester Textiles as a Source of Microplastics from Households: A Mechanistic Study to Understand Microfiber Release During Washing.

    Science.gov (United States)

    Hernandez, Edgar; Nowack, Bernd; Mitrano, Denise M

    2017-06-20

    Microplastic fibers make up a large proportion of microplastics found in the environment, especially in urban areas. There is good reason to consider synthetic textiles a major source of microplastic fibers, and it will not diminish since the use of synthetic fabrics, especially polyester, continues to increase. In this study we provide quantitative data regarding the size and mass of microplastic fibers released from synthetic (polyester) textiles during simulated home washing under controlled laboratory conditions. Consideration of fabric structure and washing conditions (use of detergents, temperature, wash duration, and sequential washings) allowed us to study the propensity of fiber shedding in a mechanistic way. Thousands of individual fibers were measured (number, length) from each wash solution to provide a robust data set on which to draw conclusions. Among all the variables tested, the use of detergent appeared to affect the total mass of fibers released the most, yet the detergent composition (liquid or powder) or overdosing of detergent did not significantly influence microplastic release. Despite different release quantities due to the addition of a surfactant (approximately 0.025 and 0.1 mg fibers/g textile washed, without and with detergent, respectively), the overall microplastic fiber length profile remained similar regardless of wash condition or fabric structure, with the vast majority of fibers ranging between 100 and 800 μm in length irrespective of wash cycle number. This indicates that the fiber staple length and/or debris encapsulated inside the fabric from the yarn spinning could be directly responsible for releasing stray fibers. This study serves as a first look toward understanding the physical properties of the textile itself to better understand the mechanisms of fiber shedding in the context of microplastic fiber release into laundry wash water.

  12. High-throughput identification of off-targets for the mechanistic study of severe adverse drug reactions induced by analgesics

    International Nuclear Information System (INIS)

    Pan, Jian-Bo; Ji, Nan; Pan, Wen; Hong, Ru; Wang, Hao; Ji, Zhi-Liang

    2014-01-01

    Drugs may induce adverse drug reactions (ADRs) when they unexpectedly bind to proteins other than their therapeutic targets. Identification of these undesired protein binding partners, called off-targets, can facilitate toxicity assessment in the early stages of drug development. In this study, a computational framework was introduced for the exploration of idiosyncratic mechanisms underlying analgesic-induced severe adverse drug reactions (SADRs). The putative analgesic-target interactions were predicted by performing reverse docking of analgesics or their active metabolites against human/mammal protein structures in a high-throughput manner. Subsequently, bioinformatics analyses were undertaken to identify ADR-associated proteins (ADRAPs) and pathways. Using the pathways and ADRAPs that this analysis identified, the mechanisms of SADRs such as cardiac disorders were explored. For instance, 53 putative ADRAPs and 24 pathways were linked with cardiac disorders, of which 10 ADRAPs were confirmed by previous experiments. Moreover, it was inferred that pathways such as base excision repair, glycolysis/glyconeogenesis, ErbB signaling, calcium signaling, and phosphatidyl inositol signaling likely play pivotal roles in drug-induced cardiac disorders. In conclusion, our framework offers an opportunity to globally understand SADRs at the molecular level, which has been difficult to realize through experiments. It also provides some valuable clues for drug repurposing. - Highlights: • A novel computational framework was developed for mechanistic study of SADRs. • Off-targets of drugs were identified in large scale and in a high-throughput manner. • SADRs like cardiac disorders were systematically explored in molecular networks. • A number of ADR-associated proteins were identified

  13. High-throughput identification of off-targets for the mechanistic study of severe adverse drug reactions induced by analgesics

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Jian-Bo [Department of Chemical Biology, College of Chemistry and Chemical Engineering, The Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiamen, Fujian 361005 (China); Ji, Nan; Pan, Wen; Hong, Ru [State Key Laboratory of Stress Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102 (China); Wang, Hao [Department of Chemical Biology, College of Chemistry and Chemical Engineering, The Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiamen, Fujian 361005 (China); Ji, Zhi-Liang, E-mail: appo@xmu.edu.cn [State Key Laboratory of Stress Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102 (China); Department of Chemical Biology, College of Chemistry and Chemical Engineering, The Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiamen, Fujian 361005 (China)

    2014-01-01

    Drugs may induce adverse drug reactions (ADRs) when they unexpectedly bind to proteins other than their therapeutic targets. Identification of these undesired protein binding partners, called off-targets, can facilitate toxicity assessment in the early stages of drug development. In this study, a computational framework was introduced for the exploration of idiosyncratic mechanisms underlying analgesic-induced severe adverse drug reactions (SADRs). The putative analgesic-target interactions were predicted by performing reverse docking of analgesics or their active metabolites against human/mammal protein structures in a high-throughput manner. Subsequently, bioinformatics analyses were undertaken to identify ADR-associated proteins (ADRAPs) and pathways. Using the pathways and ADRAPs that this analysis identified, the mechanisms of SADRs such as cardiac disorders were explored. For instance, 53 putative ADRAPs and 24 pathways were linked with cardiac disorders, of which 10 ADRAPs were confirmed by previous experiments. Moreover, it was inferred that pathways such as base excision repair, glycolysis/glyconeogenesis, ErbB signaling, calcium signaling, and phosphatidyl inositol signaling likely play pivotal roles in drug-induced cardiac disorders. In conclusion, our framework offers an opportunity to globally understand SADRs at the molecular level, which has been difficult to realize through experiments. It also provides some valuable clues for drug repurposing. - Highlights: • A novel computational framework was developed for mechanistic study of SADRs. • Off-targets of drugs were identified in large scale and in a high-throughput manner. • SADRs like cardiac disorders were systematically explored in molecular networks. • A number of ADR-associated proteins were identified.

  14. Intermanual transfer effect in young children after training in a complex skill: mechanistic, pseudorandomized, pretest-posttest study.

    Science.gov (United States)

    Romkema, Sietske; Bongers, Raoul M; van der Sluis, Corry K

    2015-05-01

    Intermanual transfer implies that motor skills learned on one side of the body transfer to the untrained side. This effect was previously noted in adults practicing with a prosthesis simulator. The study objective was to determine whether intermanual transfer is present in children practicing prosthetic handling. A mechanistic, pseudorandomized, pretest-posttest design was used. The study was conducted in a primary school in the Netherlands. The participants were children who were able-bodied (N=48; 25 boys, 23 girls; mean age=5.1 years) and randomly assigned to an experimental group or a control group. The experimental group performed 5 training sessions using a prosthesis simulator on the training arm. Before (pretest), immediately after (posttest), and 6 days after (retention test) the training program, their ability to handle the prosthesis with the contralateral (test) arm was measured. The control group only performed the tests. Half of the children performed the tests with the dominant hand, and the other half performed the tests with the nondominant hand. During the tests, movement time and control of force were measured. An interaction effect of group by test was found for movement time. Post hoc tests revealed significant improvement in the experimental group between the posttest and the retention test. No force control effect was found. Only children who were able-bodied were included. Measurements should have been masked and obtained without tester interference. The fact that 4 children whose results were slower than the mean result discontinued training may have biased the findings. The intermanual transfer effect was present in 5-year-old children undergoing training in prosthetic handling. After training of one hand, children's movement times for the other, untrained hand improved. This finding may be helpful for training children who are novice users of a prosthesis. © 2015 American Physical Therapy Association.

  15. Experimental and Theoretical Study of Microwave-Active Materials

    National Research Council Canada - National Science Library

    Mei, Wai-Ning

    2001-01-01

    .... The results to date indicate the SCAD method produces accurate physical parameters. They are also using thin-film techniques to fabricate metastable materials predicted by the theoretical calculations to have useful or interesting properties.

  16. The loss of ecosystem services due to land degradation. Integration of mechanistic and probabilistic models in an Ethiopian case study

    Science.gov (United States)

    Cerretelli, Stefania; Poggio, Laura; Gimona, Alessandro; Peressotti, Alessandro; Black, Helaina

    2017-04-01

    Land and soil degradation are widespread especially in dry and developing countries such as Ethiopia. Land degradation leads to ecosystems services (ESS) degradation, because it causes the depletion and loss of several soil functions. Ethiopia's farmland faces intense degradation due to deforestation, agricultural land expansion, land overexploitation and overgrazing. In this study we modelled the impact of physical factors on ESS degradation, in particular soil erodibility, carbon storage and nutrient retention, in the Ethiopian Great Rift Valley, northwestern of Hawassa. We used models of the Sediment retention/loss, the Nutrient Retention/loss (from the software suite InVEST) and Carbon Storage. To run the models we coupled soil local data (such as soil organic carbon, soil texture) with remote sensing data as input in the parametrization phase, e.g. to derive a land use map, to calculate the aboveground and belowground carbon, the evapotraspiration coefficient and the capacity of vegetation to retain nutrient. We then used spatialised Bayesian Belief Networks (sBBNs) predicting ecosystem services degradation on the basis of the results of the three mechanistic models. The results show i) the importance of mapping of ESS degradation taking into consideration the spatial heterogeneity and the cross-correlations between impacts ii) the fundamental role of remote sensing data in monitoring and modelling in remote, data-poor areas and iii) the important role of spatial BBNs in providing spatially explicit measures of risk and uncertainty. This approach could help decision makers to identify priority areas for intervention in order to reduce land and ecosystem services degradation.

  17. Intermanual transfer in training with an upper-limb myoelectric prosthesis simulator: a mechanistic, randomized, pretest-posttest study.

    Science.gov (United States)

    Romkema, Sietske; Bongers, Raoul M; van der Sluis, Corry K

    2013-01-01

    Intermanual transfer may improve prosthetic handling and acceptance if used in training soon after an amputation. The purpose of this study was to determine whether intermanual transfer effects can be detected after training with a myoelectric upper-limb prosthesis simulator. A mechanistic, randomized, pretest-posttest design was used. A total of 48 right-handed participants (25 women, 23 men) who were able-bodied were randomly assigned to an experimental group or a control group. The experimental group performed a training program of 5 days' duration using the prosthesis simulator. To determine the improvement in skill, a test was administered before, immediately after, and 6 days after training. The control group only performed the tests. Training was performed with the unaffected arm, and tests were performed with the affected arm (the affected arm simulating an amputated limb). Half of the participants were tested with the dominant arm and half with the nondominant arm. Initiation time was defined as the time from starting signal until start of the movement, movement time was defined as the time from the beginning of the movement until completion of the task, and force control was defined as the maximal applied force on a deformable object. The movement time decreased significantly more in the experimental group (F₂,₉₂=7.42, P=.001, η²(G)=.028) when compared with the control group. This finding is indicative of faster handling of the prosthesis. No statistically significant differences were found between groups with regard to initiation time and force control. We did not find a difference in intermanual transfer between the dominant and nondominant arms. The training utilized participants who were able-bodied in a laboratory setting and focused only on transradial amputations. Intermanual transfer was present in the affected arm after training the unaffected arm with a myoelectric prosthesis simulator, and this effect did not depend on laterality. This

  18. Why did high-dose rosuvastatin not improve cardiac remodeling in chronic heart failure? Mechanistic insights from the UNIVERSE study.

    Science.gov (United States)

    Ashton, Emma; Windebank, Emma; Skiba, Marina; Reid, Christopher; Schneider, Hans; Rosenfeldt, Franklin; Tonkin, Andrew; Krum, Henry

    2011-02-03

    Statins are often prescribed for prevention of atherosclerotic outcomes in patients who have chronic heart failure (CHF), if this has an ischaemic etiology. These agents may also possess additional properties, independent of effects on blood lipid levels, which may have an effect on cardiac remodeling. However, beneficial effects were not observed in the recent UNIVERSE trial. We prospectively planned a sub-study of UNIVERSE to explore relevant mechanistic effects of rosuvastatin, including effects on collagen turnover and plasma coenzyme Q10 (CoQ) levels. Additionally, CoQ levels in CHF patients receiving chronic statin therapy were measured. CoQ levels were significantly reduced after 26 weeks of rosuvastatin statin therapy (n = 32), compared to placebo (n = 37) in CHF patients in UNIVERSE trial. Patients with CHF (n = 56) matched for age, gender and severity of disease who had been taking statins for 12 months or longer had CoQ levels of 847 ± 344 nmol/L, significantly lower than 1065.4 ± 394 nmol/L in UNIVERSE patients at baseline (p = 0.0001). Serum types I and III N-terminal procollagen peptide (PINP and PIIINP), measures of collagen turnover which can contribute to cardiac fibrosis were significantly increased in the rosuvastatin group compared to baseline in UNIVERSE patients (PINP: p = 0.03, PIIINP: p = 0.001). In conclusion putative beneficial effects of statin therapy on cardiac remodeling in UNIVERSE may have been negated by increases in collagen turnover markers as well as a reduction in plasma CoQ levels in these patients with CHF. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  19. Theoretical study on absorption and emission spectra of adenine analogues.

    Science.gov (United States)

    Liu, Hongxia; Song, Qixia; Yang, Yan; Li, Yan; Wang, Haijun

    2014-04-01

    Fluorescent nucleoside analogues have attracted much attention in studying the structure and dynamics of nucleic acids in recent years. In the present work, we use theoretical calculations to investigate the structural and optical properties of four adenine analogues (termed as A1, A2, A3, and A4), and also consider the effects of aqueous solution and base pairing. The results show that the fluorescent adenine analogues can pair with thymine to form stable H-bonded WC base pairs. The excited geometries of both adenine analogues and WC base pairs are similar to the ground geometries. The absorption and emission maxima of adenine analogues are greatly red shifted compared with nature adenine, the oscillator strengths of A1 and A2 are stronger than A3 and A4 in both absorption and emission spectra. The calculated low-energy peaks in the absorption spectra are in good agreement with the experimental data. In general, the aqueous solution and base pairing can slightly red-shift both the absorption and emission maxima, and can increase the oscillator strengths of absorption spectra, but significantly decrease the oscillator strengths of A3 in emission spectra.

  20. A theoretical and spectroscopic study of conformational structures of piroxicam

    Science.gov (United States)

    Souza, Kely Ferreira de; Martins, José A.; Pessine, Francisco B. T.; Custodio, Rogério

    2010-02-01

    Piroxicam (PRX) has been widely studied in an attempt to elucidate the causes and mechanisms of its side effects, mainly the photo-toxicity. In this paper fluorescence spectra in non-protic solvents and different polarities were carried out along with theoretical calculations. Preliminary potential surfaces of the keto and enol forms were obtained at AM1 level of theory providing the most stable conformers, which had their structure re-optimized through the B3LYP/CEP-31G(d,p) method. From the optimized structures, the electronic spectra were calculated using the TD-DFT method in vacuum and including the solvent effect through the PCM method and a single water molecule near PRX. A new potential surface was constructed to the enol tautomer at DFT level and the most stable conformers were submitted to the QST2 calculations. The experimental data showed that in apolar media, the solution fluorescence is raised. Based on conformational analysis for the two tautomers, keto and enol, the results indicated that the PRX-enol is the main tautomer related to the drug fluorescence, which is reinforced by the spectra results, as well as the interconvertion barrier obtained from the QST2 calculations. The results suggest that the PRX one of the enol conformers presents great possibility of involvement in the photo-toxicity mechanisms.

  1. Experimental and theoretical study of Co sorption in clay montmorillonites

    Science.gov (United States)

    Gil Rebaza, A. V.; Montes, M. L.; Taylor, M. A.; Errico, L. A.; Alonso, R. E.

    2018-03-01

    Montmorillonite (MMT) clays are 2:1 layered structures which in natural state may allocate different hydrated cations such as M-nH2O (M = Na, Ca, Fe, etc) in its interlayer space. Depending on the capability for ion sorption, these materials are interesting for environmental remediation. In this work we experimentally study the Co sorption in a natural Na-MMT using UV-visible spectrometry and XRD on semi-oriented samples, and then analyze the sorption ability of this clay by means of ab initio calculation performed on pristine MMT. The structural properties of Na-MMT and Co-adsorbed MMT, and the hyperfine parameters at different atomic sites were analyzed and compared with the experimental ones for the first, and for the case of the hyperfine parameters, presented for the first time for the last. The theoretical predictions based on total energy considerations confirm that Co incorporation replacing Na is energetically favorable. Also, the basal spacing d001 experimentally obtained is well reproduced.

  2. Theoretical studies of potential energy surfaces and computational methods

    Energy Technology Data Exchange (ETDEWEB)

    Shepard, R. [Argonne National Laboratory, IL (United States)

    1993-12-01

    This project involves the development, implementation, and application of theoretical methods for the calculation and characterization of potential energy surfaces involving molecular species that occur in hydrocarbon combustion. These potential energy surfaces require an accurate and balanced treatment of reactants, intermediates, and products. This difficult challenge is met with general multiconfiguration self-consistent-field (MCSCF) and multireference single- and double-excitation configuration interaction (MRSDCI) methods. In contrast to the more common single-reference electronic structure methods, this approach is capable of describing accurately molecular systems that are highly distorted away from their equilibrium geometries, including reactant, fragment, and transition-state geometries, and of describing regions of the potential surface that are associated with electronic wave functions of widely varying nature. The MCSCF reference wave functions are designed to be sufficiently flexible to describe qualitatively the changes in the electronic structure over the broad range of geometries of interest. The necessary mixing of ionic, covalent, and Rydberg contributions, along with the appropriate treatment of the different electron-spin components (e.g. closed shell, high-spin open-shell, low-spin open shell, radical, diradical, etc.) of the wave functions, are treated correctly at this level. Further treatment of electron correlation effects is included using large scale multireference CI wave functions, particularly including the single and double excitations relative to the MCSCF reference space. This leads to the most flexible and accurate large-scale MRSDCI wave functions that have been used to date in global PES studies.

  3. Optical activity in planar chiral metamaterials: Theoretical study

    International Nuclear Information System (INIS)

    Bai, Benfeng; Svirko, Yuri; Turunen, Jari; Vallius, Tuomas

    2007-01-01

    A thorough theoretical study of the optical activity in planar chiral metamaterial (PCM) structures, made of both dielectric and metallic media, is conducted by the analysis of gammadion-shaped nanoparticle arrays. The general polarization properties are first analyzed from an effective-medium perspective, by analogy with natural optical activity, and then verified by rigorous numerical simulation, some of which are corroborated by previous experimental results. The numerical analysis suggests that giant polarization rotation (tens of degrees) may be achieved in the PCM structures with a thickness of only hundreds of nanometers. The artificial optical activity arises from circular birefringence induced by the structural chirality and is enhanced by the guided-mode or surface-plasmon resonances taking place in the structures. There are two polarization conversion types in the dielectric PCMs, whereas only one type in the metallic ones. Many intriguing features of the polarization property of PCMs are also revealed and explained: the polarization effect is reciprocal and vanishes in the symmetrically layered structures; the effect occurs only in the transmitted field, but not in the reflected field; and the polarization spectra of two enantiomeric PCM structures are mirror symmetric to each other. These remarkable properties pave the way for the PCMs to be used as polarization elements in new-generation integrated optical systems

  4. A mechanistic study of the addition of alcohol to a five-membered ring silene via a photochemical reaction.

    Science.gov (United States)

    Su, Ming-Der

    2016-03-21

    The mechanism for the photochemical rearrangement of a cyclic divinyldisilane (1-Si) in its first excited state ((1)π → (1)π*) is determined using the CAS/6-311G(d) and MP2-CAS/6-311++G(3df,3pd) levels of theory. The photoproduct, a cyclic silene, reacts with various alcohols to yield a mixture of cis- and trans- adducts. The two reaction pathways are denoted as the cis- addition path (path A) and the trans-addition path (path B). These model studies demonstrate that conical intersections play a crucial role in the photo-rearrangements of cyclic divinyldisilanes. The theoretical evidence also demonstrates that the addition of alcohol to a cyclic divinyldisilane follows the reaction path: cyclic divinyldisilane → Franck-Condon region → conical intersection → photoproduct (cyclic silene) → local intermediate (with alcohol) → transition state → cis- or trans-adduct. The theoretical studies demonstrate that the steric effects as well as the concentrations of CH3OH must have a dominant role in determining the yields of the final adducts by stereochemistry. The same mechanism for the carbon derivative (1-C) is also considered in this work. However, the theoretical results indicate that 1-C does not undergo a methanol addition reaction via the photochemical reaction pathway, since its energy of conical intersection (S1/S0-CI-C) is more than that of its FC (FC-C). The reason for these phenomena could be that the atomic radius of carbon is much smaller than that of silicon (77 and 117 pm, respectively). As a result, the conformation for 1-C is more sterically congested than that for 1-Si, along the 1,3-silyl-migration pathway.

  5. Combining solvent isotope effects with substrate isotope effects in mechanistic studies of alcohol and amine oxidation by enzymes.

    Science.gov (United States)

    Fitzpatrick, Paul F

    2015-11-01

    Oxidation of alcohols and amines is catalyzed by multiple families of flavin- and pyridine nucleotide-dependent enzymes. Measurement of solvent isotope effects provides a unique mechanistic probe of the timing of the cleavage of the OH and NH bonds, necessary information for a complete description of the catalytic mechanism. The inherent ambiguities in interpretation of solvent isotope effects can be significantly decreased if isotope effects arising from isotopically labeled substrates are measured in combination with solvent isotope effects. The application of combined solvent and substrate (mainly deuterium) isotope effects to multiple enzymes is described here to illustrate the range of mechanistic insights that such an approach can provide. This article is part of a Special Issue entitled: Enzyme Transition States from Theory and Experiment. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Theoretical Studies Of Nucleation Kinetics And Nanodroplet Microstructure

    International Nuclear Information System (INIS)

    Wilemski, Gerald

    2009-01-01

    The goals of this project were to (1) explore ways of bridging the gap between fundamental molecular nucleation theories and phenomenological approaches based on thermodynamic reasoning, (2) test and improve binary nucleation theory, and (3) provide the theoretical underpinning for a powerful new experimental technique, small angle neutron scattering (SANS) from nanodroplet aerosols, that can probe the compositional structure of nanodroplets. This report summarizes the accomplishments of this project in realizing these goals. Publications supported by this project fall into three general categories: (1) theoretical work on nucleation theory (2) experiments and modeling of nucleation and condensation in supersonic nozzles, and (3) experimental and theoretical work on nanodroplet structure and neutron scattering. These publications are listed and briefly summarized in this report.

  7. Theoretical study on device efficiency of pulsed liquid jet pump

    International Nuclear Information System (INIS)

    Gao Chuanchang; Lu Hongqi; Wang Shicheng; Cheng Mingchuan

    2001-01-01

    The influence of the main factors on device efficiency of pulsed liquid jet pump with gas-liquid piston is analysed, the theoretical equation and its time-averaged solution of pulsed liquid jet pump device efficiency are derived. The theoretical and experimental results show that the efficiency of transmission of energy and mass to use pulsed jet is greatly raised, compared with steady jet, in the same device of liquid jet pump. The calculating results of time-averaged efficiency of pulsed liquid jet pump are approximately in agreement with the experimental results in our and foreign countries

  8. Studying stellar rotation and convection theoretical background and seismic diagnostics

    CERN Document Server

    Belkacem, Kévin; Neiner, Coralie; Lignières, Francois; Green, John

    2013-01-01

    This volume synthesizes the results of work carried out by several international teams of the SIROCO (Seismology for Rotation and Convection) collaboration. It provides the theoretical background required to interpret the huge quantity of high-quality observational data recently provided by space experiments such as CoRoT and Kepler. Asteroseismology allows astrophysicists to test, to model and to understand stellar structure and evolution as never before. The chapters in this book address the two groups of topics summarized as "Stellar Rotation and Associated Seismology" as well as "Stellar Convection and Associated Seismology". The book offers the reader solid theoretical background knowledge and adapted seismic diagnostic techniques.

  9. Assessing the ability of mechanistic volatilization models to simulate soil surface conditions: a study with the Volt'Air model.

    Science.gov (United States)

    Garcia, L; Bedos, C; Génermont, S; Braud, I; Cellier, P

    2011-09-01

    Ammonia and pesticide volatilization in the field is a surface phenomenon involving physical and chemical processes that depend on the soil surface temperature and water content. The water transfer, heat transfer and energy budget sub models of volatilization models are adapted from the most commonly accepted formalisms and parameterizations. They are less detailed than the dedicated models describing water and heat transfers and surface status. The aim of this work was to assess the ability of one of the available mechanistic volatilization models, Volt'Air, to accurately describe the pedo-climatic conditions of a soil surface at the required time and space resolution. The assessment involves: (i) a sensitivity analysis, (ii) an evaluation of Volt'Air outputs in the light of outputs from a reference Soil-Vegetation-Atmosphere Transfer model (SiSPAT) and three experimental datasets, and (iii) the study of three tests based on modifications of SiSPAT to establish the potential impact of the simplifying assumptions used in Volt'Air. The analysis confirmed that a 5 mm surface layer was well suited, and that Volt'Air surface temperature correlated well with the experimental measurements as well as with SiSPAT outputs. In terms of liquid water transfers, Volt'Air was overall consistent with SiSPAT, with discrepancies only during major rainfall events and dry weather conditions. The tests enabled us to identify the main source of the discrepancies between Volt'Air and SiSPAT: the lack of gaseous water transfer description in Volt'Air. They also helped to explain why neither Volt'Air nor SiSPAT was able to represent lower values of surface water content: current classical water retention and hydraulic conductivity models are not yet adapted to cases of very dry conditions. Given the outcomes of this study, we discuss to what extent the volatilization models can be improved and the questions they pose for current research in water transfer modeling and parameterization

  10. EXPERIMENTAL AND THEORETICAL NMR STUDY OF 4-(1 ...

    African Journals Online (AJOL)

    Preferred Customer

    increased to cover various kinds of compounds, including biological, inorganic and organometallic compounds [8]. 1D and 2D hetero- and homonuclear NMR methods enable to get full assignments and structural information of organic compounds [9-11]. For the theoretical NMR investigations, the gauge including atomic ...

  11. Theoretical studies of ethylnitrolic acid using Gaussian | Nikafshar ...

    African Journals Online (AJOL)

    The tautomerism of all possible forms of ethylnitrolic acid was investigated theoretically in various environment including gas phase, ethanol, dimethyl sulfoxide (DMSO) and water. The calculations were carried out at DFT/B3LYP and MP2 of theory singly. It was found that, form of B eythynitrolic acid is the most stable isomer ...

  12. Theoretical Studies of Small-System Thermodynamics in Energetic Materials

    Science.gov (United States)

    2016-01-06

    molecular explosives and interfaces between explosive constituent materials. Exploring how the fundamental thermodynamic properties and energy...SECURITY CLASSIFICATION OF: This is a comprehensive theoretical research program to investigate the fundamental principles of small-system thermodynamics ...a.k.a. nanothermodynamics). The proposed work is motivated by our desire to better understand the fundamental dynamics and thermodynamics of

  13. Experimental and theoretical study of magnetohydrodynamic ship models.

    Science.gov (United States)

    Cébron, David; Viroulet, Sylvain; Vidal, Jérémie; Masson, Jean-Paul; Viroulet, Philippe

    2017-01-01

    Magnetohydrodynamic (MHD) ships represent a clear demonstration of the Lorentz force in fluids, which explains the number of students practicals or exercises described on the web. However, the related literature is rather specific and no complete comparison between theory and typical small scale experiments is currently available. This work provides, in a self-consistent framework, a detailed presentation of the relevant theoretical equations for small MHD ships and experimental measurements for future benchmarks. Theoretical results of the literature are adapted to these simple battery/magnets powered ships moving on salt water. Comparison between theory and experiments are performed to validate each theoretical step such as the Tafel and the Kohlrausch laws, or the predicted ship speed. A successful agreement is obtained without any adjustable parameter. Finally, based on these results, an optimal design is then deduced from the theory. Therefore this work provides a solid theoretical and experimental ground for small scale MHD ships, by presenting in detail several approximations and how they affect the boat efficiency. Moreover, the theory is general enough to be adapted to other contexts, such as large scale ships or industrial flow measurement techniques.

  14. Experimental and theoretical study of magnetohydrodynamic ship models.

    Directory of Open Access Journals (Sweden)

    David Cébron

    Full Text Available Magnetohydrodynamic (MHD ships represent a clear demonstration of the Lorentz force in fluids, which explains the number of students practicals or exercises described on the web. However, the related literature is rather specific and no complete comparison between theory and typical small scale experiments is currently available. This work provides, in a self-consistent framework, a detailed presentation of the relevant theoretical equations for small MHD ships and experimental measurements for future benchmarks. Theoretical results of the literature are adapted to these simple battery/magnets powered ships moving on salt water. Comparison between theory and experiments are performed to validate each theoretical step such as the Tafel and the Kohlrausch laws, or the predicted ship speed. A successful agreement is obtained without any adjustable parameter. Finally, based on these results, an optimal design is then deduced from the theory. Therefore this work provides a solid theoretical and experimental ground for small scale MHD ships, by presenting in detail several approximations and how they affect the boat efficiency. Moreover, the theory is general enough to be adapted to other contexts, such as large scale ships or industrial flow measurement techniques.

  15. Mechanistic Studies and Modeling Reveal the Origin of Differential Inhibition of Gag Polymorphic Viruses by HIV-1 Maturation Inhibitors.

    Science.gov (United States)

    Lin, Zeyu; Cantone, Joseph; Lu, Hao; Nowicka-Sans, Beata; Protack, Tricia; Yuan, Tian; Yang, Hong; Liu, Zheng; Drexler, Dieter; Regueiro-Ren, Alicia; Meanwell, Nicholas A; Cockett, Mark; Krystal, Mark; Lataillade, Max; Dicker, Ira B

    2016-11-01

    HIV-1 maturation inhibitors (MIs) disrupt the final step in the HIV-1 protease-mediated cleavage of the Gag polyprotein between capsid p24 capsid (CA) and spacer peptide 1 (SP1), leading to the production of infectious virus. BMS-955176 is a second generation MI with improved antiviral activity toward polymorphic Gag variants compared to a first generation MI bevirimat (BVM). The underlying mechanistic reasons for the differences in polymorphic coverage were studied using antiviral assays, an LC/MS assay that quantitatively characterizes CA/SP1 cleavage kinetics of virus like particles (VLPs) and a radiolabel binding assay to determine VLP/MI affinities and dissociation kinetics. Antiviral assay data indicates that BVM does not achieve 100% inhibition of certain polymorphs, even at saturating concentrations. This results in the breakthrough of infectious virus (partial antagonism) regardless of BVM concentration. Reduced maximal percent inhibition (MPI) values for BVM correlated with elevated EC50 values, while rates of HIV-1 protease cleavage at CA/SP1 correlated inversely with the ability of BVM to inhibit HIV-1 Gag polymorphic viruses: genotypes with more rapid CA/SP1 cleavage kinetics were less sensitive to BVM. In vitro inhibition of wild type VLP CA/SP1 cleavage by BVM was not maintained at longer cleavage times. BMS-955176 exhibited greatly improved MPI against polymorphic Gag viruses, binds to Gag polymorphs with higher affinity/longer dissociation half-lives and exhibits greater time-independent inhibition of CA/SP1 cleavage compared to BVM. Virological (MPI) and biochemical (CA/SP1 cleavage rates, MI-specific Gag affinities) data were used to create an integrated semi-quantitative model that quantifies CA/SP1 cleavage rates as a function of both MI and Gag polymorph. The model outputs are in accord with in vitro antiviral observations and correlate with observed in vivo MI efficacies. Overall, these findings may be useful to further understand antiviral

  16. Crystal structure and theoretical studies on quinoline phosphate

    Science.gov (United States)

    Ben Issa, T.; Ghalla, H.; Marzougui, S.; Benhamada, L.

    2017-12-01

    The crystal structure of (C9H7N) H3PO4 (QP) was determined from single crystals obtained by slow evaporation methods (space group Pī; a = 7.5508(3) Å, b = 7.9705(3) Å, c = 8.6849(3) Å; α = 77.3725(18)°, β = 82.6225(19)°, γ = 74.9829(19)°). The crystal structure of QP is built up from infinite hydrogen bonding inorganic chains of (H3PO4)n lay parallel to the an axis, which are also connected to the quinoline rings through hydrogen bonds in a 3D arrangement. The structure was examined through atoms in molecules (AIM) topological and Hirshfeld surface (HS) analyses and its molecular structure optimized by theoretical density functional (DFT) calculations. The QP observed IR absorptions between 4000 and 400 cm-1 were assigned on the basis of the calculated theoretical vibrational modes.

  17. Spectroscopic Analysis of Neurotransmitters: A Theoretical and Experimental Raman Study

    Science.gov (United States)

    Alonzo, Matthew

    Surface-enhanced Raman spectroscopy (SERS) was applied to investigate the feasibility in the detection and monitoring of the dopamine (DA) neurotransmitter adsorbed onto silver nanoparticles (Ag NPs) at 10-11 molar, a concentration far below physiological levels. In addition, density functional theory (DFT) calculations were obtained with the Gaussian-09 analytical suite software to generate the theoretical molecular configuration of DA in its neutral, cationic, anionic, and dopaminequinone states for the conversion of computer-simulated Raman spectra. Comparison of theoretical and experimental results show good agreement and imply the presence of dopamine in all of its molecular forms in the experimental setting. The dominant dopamine Raman bands at 750 cm-1 and 795 cm-1 suggest the adsorption of dopaminequinone onto the silver nanoparticle surface. The results of this experiment give good insight into the applicability of using Raman spectroscopy for the biodetection of neurotransmitters.

  18. Rovibrational and temperature effects in theoretical studies of NMR parameters

    DEFF Research Database (Denmark)

    Faber, Rasmus; Kaminsky, Jakub; Sauer, Stephan P. A.

    2016-01-01

    The demand for high precision calculations of NMR shieldings (or their related values, chemical shifts δ) and spin-spin coupling constants facilitating and supporting detailed interpretations of NMR spectra increases hand in hand with the development of computational techniques and hardware...... resources. Highly sophisticated calculations including even relativistic effects are nowadays possible for these properties. However, NMR parameters depend not only on molecular structure and environment but also on molecular flexibility and temperature and the apparent success of theoretical predictions...

  19. Theoretical studies in weak, electromagnetic and strong interactions. Attachments

    International Nuclear Information System (INIS)

    Nandi, S.

    1999-01-01

    The project covered a wide area of current research in theoretical high-energy physics. This included Standard Model (SM) as well as physics beyond the Standard Model. Specific topics included supersymmetry (SUSY), perturbative quantum chromodynamics (QCD), a new weak interaction for the third family (called topflavor), neutrino masses and mixings, topcolor model, Pade approximation, and its application to perturbative QCD and other physical processes

  20. Theoretical studies of lipid bilayer electroporation using molecular dynamics simulations

    Science.gov (United States)

    Levine, Zachary Alan

    system where lipids can become damaged or severely impacted from interacting with reactive oxygen species, and these events become more frequent with age. The results are then compared to experiments where we show agreement between our simulations, theoretical models, and experiments with peroxidized cells in our lab. In Chapter 3 I outline a set of unique metrics which can be used to quantitatively measure the life cycle of a discrete electropore for the first time, across multiple lipid species, and I compare these results to analytical models where we find good agreement with theory. In Chapter 4 I use the life cycle of an electropore as a tool to measure the effects of electrolyte and lipid headgroup charge on electroporation compared to electrolyte-free and zwitterionic systems, in addition to presenting ion binding isotherms to determine the validity of our simulated electrolyte models. Chapters 5 and 6 focus on the roles of water and lipid respectively on electroporation using simplified water:vacuum systems, osmotic swelling simulations, systems at varying temperature, and systems where we successfully modulated the electropore radius using customized time-dependent electric fields. I conclude this dissertation with a brief summary of these studies followed by a short outlook on the future of electroporation simulations as a whole.

  1. Integrating mechanistic organism--environment interactions into the basic theory of community and evolutionary ecology.

    Science.gov (United States)

    Baskett, Marissa L

    2012-03-15

    This paper presents an overview of how mechanistic knowledge of organism-environment interactions, including biomechanical interactions of heat, mass and momentum transfer, can be integrated into basic theoretical population biology through mechanistic functional responses that quantitatively describe how organisms respond to their physical environment. Integrating such functional responses into simple community and microevolutionary models allows scaling up of the organism-level understanding from biomechanics both ecologically and temporally. For community models, Holling-type functional responses for predator-prey interactions provide a classic example of the functional response affecting qualitative model dynamics, and recent efforts are expanding analogous models to incorporate environmental influences such as temperature. For evolutionary models, mechanistic functional responses dependent on the environment can serve as fitness functions in both quantitative genetic and game theoretic frameworks, especially those concerning function-valued traits. I present a novel comparison of a mechanistic fitness function based on thermal performance curves to a commonly used generic fitness function, which quantitatively differ in their predictions for response to environmental change. A variety of examples illustrate how mechanistic functional responses enhance model connections to biologically relevant traits and processes as well as environmental conditions and therefore have the potential to link theoretical and empirical studies. Sensitivity analysis of such models can provide biologically relevant insight into which parameters and processes are important to community and evolutionary responses to environmental change such as climate change, which can inform conservation management aimed at protecting response capacity. Overall, the distillation of detailed knowledge or organism-environment interactions into mechanistic functional responses in simple population

  2. Synthetic Applications and Mechanistic Studies of the Hydroxide-Mediated Cleavage of Carbon-Carbon Bonds in Ketones

    DEFF Research Database (Denmark)

    Mazziotta, Andrea; Makarov, Ilya S.; Fristrup, Peter

    2017-01-01

    The hydroxide-mediated cleavage of ketones into alkanes and carboxylic acids has been reinvestigated and the substrate scope extended to benzyl carbonyl compounds. The transformation is performed with a 0.05 M ketone solution in refluxing xylene in the presence of 10 equiv of potassium hydroxide....... The reaction constitutes a straightforward protocol for the synthesis of certain phenyl-substituted carboxylic acids from 2-phenylcycloalkanones. The mechanism was investigated by kinetic experiments which indicated a first order reaction in hydroxide and a full negative charge in the rate-determining step....... The studies were complemented by a theoretical investigation where two possible pathways were characterized by DFT/M06-2X. The calculations showed that the scission takes place by nucleophilic attack of hydroxide on the ketone followed by fragmentation of the resulting oxyanion into the carboxylic acid...

  3. Synthetic Applications and Mechanistic Studies of the Hydroxide-Mediated Cleavage of Carbon-Carbon Bonds in Ketones.

    Science.gov (United States)

    Mazziotta, Andrea; Makarov, Ilya S; Fristrup, Peter; Madsen, Robert

    2017-06-02

    The hydroxide-mediated cleavage of ketones into alkanes and carboxylic acids has been reinvestigated and the substrate scope extended to benzyl carbonyl compounds. The transformation is performed with a 0.05 M ketone solution in refluxing xylene in the presence of 10 equiv of potassium hydroxide. The reaction constitutes a straightforward protocol for the synthesis of certain phenyl-substituted carboxylic acids from 2-phenylcycloalkanones. The mechanism was investigated by kinetic experiments which indicated a first order reaction in hydroxide and a full negative charge in the rate-determining step. The studies were complemented by a theoretical investigation where two possible pathways were characterized by DFT/M06-2X. The calculations showed that the scission takes place by nucleophilic attack of hydroxide on the ketone followed by fragmentation of the resulting oxyanion into the carboxylic acid and a benzyl anion.

  4. A DFT Mechanistic Study on Ethylene Tri- and Tetramerization with Cr/PNP Catalysts: Single versus Double Insertion Pathways.

    Science.gov (United States)

    Britovsek, George J P; McGuinness, David S

    2016-11-14

    The mechanism of ethylene trimerization and tetramerization with a chromium-diphosphinoamine (Cr-PNP) catalyst system has been studied by theoretical (DFT) methods. Two representative ligands have been explored, namely Ph 2 PN(Me)PPh 2 and (o-MeC 6 H 4 ) 2 PN(Me)P(o-MeC 6 H 4 ) 2 . Calculations on the former ligand reveal how a combination of single and double ethylene insertion mechanisms may lead to 1-hexene, 1-octene and the major side products (cyclopentanes and n-alkanes). For the latter ligand, introduction of o-alkyl substitution leads to a more sterically congested active species, which suppresses the available pathways for tetramerization and side product formation. Hence, the high selectivity of o-aryl substituted PNP ligands for trimerization can be rationalized. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Kinetic and mechanistic studies of reactive intermediates in photochemical and transition metal-assisted oxidation, decarboxylation and alkyl transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Carraher, Jack McCaslin [Iowa State Univ., Ames, IA (United States)

    2014-01-01

    Reactive species like high-valent metal-oxo complexes and carbon and oxygen centered radicals are important intermediates in enzymatic systems, atmospheric chemistry, and industrial processes. Understanding the pathways by which these intermediates form, their relative reactivity, and their fate after reactions is of the utmost importance. Herein are described the mechanistic detail for the generation of several reactive intermediates, synthesis of precursors, characterization of precursors, and methods to direct the chemistry to more desirable outcomes yielding ‘greener’ sources of commodity chemicals and fuels.

  6. Theoretical studies of permeability inversion from seismoelectric logs

    Science.gov (United States)

    Hu, H.; Guan, W.; Zhao, W.

    2012-04-01

    Permeability is one of the most important parameters for evaluating the level of difficulty in oil and gas exploitation. A quick, continuous and accurate in-situ estimate of reservoir permeability is highly significant. Stoneley wave logs have been used to determine formation permeability (Tang and Cheng, 1996). However, the inversion errors of this method are too big in low-permeability formations, especially in high-porosity and low-permeability formations resulting from the high clay content in pores. In this study, we propose to invert permeability by using the full waveforms of seismoelectric logs with low frequencies. This method is based on the relationship of permeability with the ratio of the electric excitation intensity to the pressure field's (REP) with respect to the Stoneley wave in seismoelectric logs. By solving the governing equations for electrokinetic coupled wavefields in homogeneous fluid-saturated porous media (Pride, 1994), we calculate the full waveforms of the borehole seismoelectric wavefields excited by a point pressure source and investigate frequency-dependent excitation intensities of the mode waves and excitation intensities of the real branch points in seismoelectric logs. It is found that the REP's phase, which reflects the phase discrepancy between the Stoneley-wave-induced electric field and the acoustic pressure, is sensitive to formation permeability. To check the relation between permeability and REP's phase qualitatively, an approximate expression of the tangent of the REP's argument is derived theoretically as tan(θEP) ≈-ωc/ω = -φη/ (2πfα ∞ρfκ0), where θEPdenotes the arguments of the REP and their principal value is the REP's phase,ω is the angular frequency,ωc is a critical angular frequency that separates the low-frequency viscous flow from the high-frequency inertial flow, φ is the porosity, α∞ is the tortuosity, κ0 is the Darcy permeability, ρf and η are the density and the viscosity of the pore

  7. Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

    DEFF Research Database (Denmark)

    Phatak, C.; Petford-Long, A. K.; Beleggia, Marco

    2014-01-01

    Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We present...... a theoretical model describing how the shape of a nanoparticle affects its polarization in the absence of screening charges, and quantify the electron-optical phase shift for detecting ferroelectric signals with phase-sensitive techniques in a transmission electron microscope. We provide an example phase shift...

  8. Theoretical study of magnetoelectric effects in noncentrosymmetric and cuprate superconductors

    Science.gov (United States)

    Kashyap, Manoj K.

    A century after the discovery of superconductivity at the lab of Kamerlingh Onnes in 1911, it is noticeable that the phenomenon is quite ubiquitous in nature. In addition to a long list of superconducting alloys and compounds, almost half the elements in the periodic table superconduct. By the late seventies, superconductivity was thought to be well understood. This turned out to be a myth, with the discovery of unconventional superconductors that defied Bardeen-Cooper-Schrieffer (BCS) theory. Cuprates have been the most prominent example among them ever since their discovery in 1986 by Bednorz and Muller. Another example of non-compliance with BCS theory lie among noncentrosymmetric superconductors. In this dissertation, magnetoelectric (ME) effects in these two classes of superconductors have been studied from different perspectives, utilizing Ginzburg-Landau (GL) theory. Even though GL theory was proposed before the BCS theory, it was not given much importance due to its phenomenological nature until Gor'kov proved that it is a limiting form of the microscopic BCS theory. However today, in the absence of any complete microscopic theory to explain superconductivity in unconventional superconductors, Ginzburg-Landau theory is an important tool to move ahead and qualitatively understand the behavior of varied superconducting systems. Noncentrosymmetric superconductors have generated much theoretical interest since 2004 despite been known for long. The absence of inversion symmetry in non- centrosymmetric superconductors allows for extra terms called Lifshitz invariants in the Ginzburg-Landau functional. This leads to magnetoelectric effects that do not exist in centrosymmetric superconductors. One manifestation of this is in the vortex structure in materials with a cubic point group O. In particular, a current is predicted to flow parallel to the applied magnetic field in such a vortex in addition to the usual vortex supercurrents. In this work, we present both

  9. Protonation of caffeine: A theoretical and experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Bahrami, Hamed [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Tabrizchi, Mahmoud, E-mail: m-tabriz@cc.iut.ac.ir [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Farrokhpour, Hossein [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2013-03-29

    Highlights: ► Protonation of caffeine was examined by ion mobility spectrometry equipped with two ionization sources. ► Experimental and theoretical evidence was collected to assign the observed peaks to caffeine related ionic species. ► A new concept of “internal proton affinity”, the protonation tendency for each atom in a molecule, was defined. - Abstract: Protonation of caffeine was examined by ion mobility spectrometry equipped with two ionization sources, corona discharge (CD) and UV photoionization. Three peaks were observed in ion mobility spectrum by simultaneously running the two ionization sources. Experimental and theoretical evidence was collected to link the observed peaks to caffeine related ionic species. One peak was attributed to the M{sup +} ion while the other two were assigned to different protonated isomers of caffeine. In the case of CD ionization source, it was observed that different sites of caffeine compete for protonation and their relative intensities, depends on the sample concentration as well as the nature of the reactant ions. The new concept of “internal proton affinity” (IPA) was defined to express the tendency of holding the added proton for each atom in a molecule.

  10. Crystal growth, characterization and theoretical studies of 4-aminopyridinium picrate

    Science.gov (United States)

    Aditya Prasad, A.; Muthu, K.; Rajasekar, M.; Meenatchi, V.; Meenakshisundaram, S. P.

    2015-01-01

    Single crystals of 4-aminopyridinium picrate (APP) were grown by slow evaporation of a mixed solvent system methanol-acetone (1:1, v/v) containing equimolar quantities of 4-aminopyridine and picric acid. Structure is elucidated by single crystal XRD analysis and the crystal belongs to monoclinic system with four molecules in the unit cell (space group P21/c) and the cell parameter values are, a = 8.513 Å (±0.015), b = 11.33 Å (±0.02), c = 14.33 Å (±0.03) and β = 104.15° (±0.019), V = 1340 A3 (±6) with refined R factors R1 = 0.0053 and wR2 = 0.0126. The electron density mapping is interpreted to find coordinates for each atom in the crystallized molecules. The various functional groups present in the molecule are confirmed by FT-IR analysis. UV-visible spectral analysis was used to determine the band gap energy of 4-aminopyridinium picrate. Powder X-ray diffraction pattern reveals the crystallinity of the as-grown crystal and it closely resembles the simulated XRD from the single crystal XRD analysis. Scanning electron microscopy reveals the surface morphology of the grown crystal. Optimized geometry is derived by Hartree-Fock theory calculations and the first-order molecular hyperpolarizability (β), theoretically calculated bond length, bond angles and excited state energy from theoretical UV-vis spectrum were estimated.

  11. Poroelastic toughening in polymer gels: A theoretical and numerical study

    Science.gov (United States)

    Noselli, Giovanni; Lucantonio, Alessandro; McMeeking, Robert M.; DeSimone, Antonio

    2016-09-01

    We explore the Mode I fracture toughness of a polymer gel containing a semi-infinite, growing crack. First, an expression is derived for the energy release rate within the linearized, small-strain setting. This expression reveals a crack tip velocity-independent toughening that stems from the poroelastic nature of polymer gels. Then, we establish a poroelastic cohesive zone model that allows us to describe the micromechanics of fracture in gels by identifying the role of solvent pressure in promoting poroelastic toughening. We evaluate the enhancement in the effective fracture toughness through asymptotic analysis. We confirm our theoretical findings by means of numerical simulations concerning the case of a steadily propagating crack. In broad terms, our results explain the role of poroelasticity and of the processes occurring in the fracturing region in promoting toughening of polymer gels.

  12. Theoretical Advanced Study Institute in Elementary Particle Physics

    CERN Document Server

    2017-01-01

    The program will consist of a pedagogical series of lectures and seminars. Lectures will be given over a four-week period, three or four lectures per day, Monday through Friday. The audience will be composed primarily of advanced theoretical graduate students. Experimentalists with a strong background in theory are also encouraged to apply. Some post-doctoral fellows will be admitted, but preference will be given to applicants who will not have received their Ph.D. before 2017. The minimum background needed to get full benefit of TASI is a knowledge of quantum field theory (including RGEs) and familiarity with the Standard Model. Some familiarity with SUSY would be helpful. We hope to provide some subsidy, but students will need partial support from other sources. Rooms, meals, and access to all facilities will be provided at reasonable rates in beautifully located dormitories at the University of Colorado.

  13. Theoretical study of third sound in a layered superfluid film

    International Nuclear Information System (INIS)

    Cheng, E.; Saam, W.F.; Cole, M.W.; Treiner, J.

    1993-01-01

    The authors present a calculation of the third sound speed c 3 of thin 4 He films adsorbed on H 2 , Li, Mg, graphite and H 2 -plated graphite. The results show a clear correlation of oscillations in c 3 , with a period of one atomic layer, with the layering phenomena observed in adsorption isotherms. Comparison is made with recent experimental results for helium films on solid H 2 by Shirron and Mochel and by Brisson, Mester and Silvera. The theoretical analysis suggests explanations for disagreements between different interpretations of data. A standard way of determining the number of so-called inert layers is questioned. Other available experimental data on graphite and H 2 -plated graphite are also discussed

  14. We need theoretical physics approaches to study living systems

    Science.gov (United States)

    Blagoev, Krastan B.; Shukla, Kamal; affil="3" >Herbert Levine,

    2013-08-01

    Living systems, as created initially by the transition from assemblies of large molecules to self-reproducing information-rich cells, have for centuries been studied via the empirical toolkit of biology. This has been a highly successful enterprise, bringing us from the vague non-scientific notions of vitalism to the modern appreciation of the biophysical and biochemical bases of life. Yet, the truly mind-boggling complexity of even the simplest self-sufficient cells, let alone the emergence of multicellular organisms, of brain and consciousness, and to ecological communities and human civilizations, calls out for a complementary approach. In this editorial, we propose that theoretical physics can play an essential role in making sense of living matter. When faced with a highly complex system, a physicist builds simplified models. Quoting Philip W Anderson's Nobel prize address, 'the art of model-building is the exclusion of real but irrelevant parts of the problem and entails hazards for the builder and the reader. The builder may leave out something genuinely relevant and the reader, armed with too sophisticated an experimental probe, may take literally a schematized model. Very often such a simplified model throws more light on the real working of nature....' In his formulation, the job of a theorist is to get at the crux of the system by ignoring details and yet to find a testable consequence of the resulting simple picture. This is rather different than the predilection of the applied mathematician who wants to include all the known details in the hope of a quantitative simulacrum of reality. These efforts may be practically useful, but do not usually lead to increased understanding. To illustrate how this works, we can look at a non-living example of complex behavior that was afforded by spatiotemporal patterning in the Belousov-Zhabotinsky reaction [1]. Physicists who worked on this system did not attempt to determine all the relevant chemical intermediates

  15. Theoretical studies in nuclear reactions and nuclear structure

    International Nuclear Information System (INIS)

    1989-08-01

    During the past year, research in theoretical nuclear physics at the University of Maryland attained a number of exciting and important results. These are described in some detail throughout the report, but some of the highlights are as follows: large N c QCD has been shown to place strong constraints on vacuum effects of hadronic field theories; color dielectric models of hadrons have been understood in terms of lattice QCD; we have completed a relativistic analysis of proton scattering to test virtual pair contributions; we have also re-derived the Mandelzweig-Wallace two-body Dirac equation in covariant form, and applied it to the atomic two-body bound states: hydrogen, muonium and positronium; we have carried out the first calculation of the triton binding energy with a realistic quark-based nucleon-nucleon interaction and have learned that new kinds of nonlocalities in the tensor force may produce unexpected results; and we have shown that the Quadronium Conjecture can lead to spontaneous creation of the atom with low momentum as required by the observations, and are constructing a model to quantify the Quadronium phenomenology of the e + e - Puzzle

  16. Theoretical studies in medium-energy nuclear and hadronic physics

    International Nuclear Information System (INIS)

    Horowitz, C.J.; Macfarlane, M.H.; Matsui, T.; Serot, B.D.

    1993-01-01

    A proposal for theoretical nuclear physics research is made for the period April 1, 1993 through March 31, 1996. Research is proposed in the following areas: relativistic many-body theory of nuclei and nuclear matter, quasifree electroweak scattering and strange quarks in nuclei, dynamical effects in (e,e'p) scattering at large momentum transfer, investigating the nucleon's parton sea with polarized leptoproduction, physics of ultrarelativistic nucleus endash nucleus collisions, QCD sum rules and hadronic properties, non-relativistic models of nuclear reactions, and spin and color correlations in a quark-exchange model of nuclear matter. Highlights of recent research, vitae of principal investigators, and lists of publications and invited talks are also given. Recent research dealt primarily with medium-energy nuclear physics, relativistic theories of nuclei and the nuclear response, the nuclear equation of state under extreme conditions, the dynamics of the quark endash gluon plasma in relativistic heavy-ion collisions, and theories of the nucleon endash nucleon force

  17. Theoretical and Experimental Studies of Elementary Particle Physics

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Harold G [Indiana University; Kostelecky, V Alan [Indiana University; Musser, James A [Indiana University

    2013-07-29

    The elementary particle physics research program at Indiana University spans a broad range of the most interesting topics in this fundamental field, including important contributions to each of the frontiers identified in the recent report of HEPAP's Particle Physics Prioritization Panel: the Energy Frontier, the Intensity Frontier, and the Cosmic Frontier. Experimentally, we contribute to knowledge at the Energy Frontier through our work on the D0 and ATLAS collaborations. We work at the Intensity Frontier on the MINOS and NOvA experiments and participate in R&D for LBNE. We are also very active on the theoretical side of each of these areas with internationally recognized efforts in phenomenology both in and beyond the Standard Model and in lattice QCD. Finally, although not part of this grant, members of the Indiana University particle physics group have strong involvement in several astrophysics projects at the Cosmic Frontier. Our research efforts are divided into three task areas. The Task A group works on D0 and ATLAS; Task B is our theory group; and Task C contains our MINOS, NOvA, and LBNE (LArTPC) research. Each task includes contributions from faculty, senior scientists, postdocs, graduate and undergraduate students, engineers, technicians, and administrative personnel. This work was supported by DOE Grant DE-FG02-91ER40661. In the following, we describe progress made in the research of each task during the final period of the grant, from November 1, 2009 to April 30, 2013.

  18. A unified theoretical and experimental study of anisotropic hardening

    International Nuclear Information System (INIS)

    Boehler, J.P.; Raclin, J.

    1981-01-01

    The purpose of this work is to develop a consistent formulation of the constitutive relations regarding anisotropic hardening materials. Attention is focused on the appearance and the evolution of mechanical anisotropies during irreversible processes, such as plastic forming and inelastic deformation of structures. The representation theorems for anisotropic tensor functions constitute a theoretical basis, allowing to reduce arbitrariness and to obtain a unified formulation of anisotropic hardening. In this approach, a general three-dimensional constitutive law is developed for prestrained initially orthotropic materials. Introduction of the plastic behavior results in the general forms of both the flow-law and the yield criterion. The developed theory is then specialized for the case of plane stress and different modes of anisotropic hardening are analyzed. A new generalization of the Von Mises criterion is proposed, in considering a homogeneous form of order two in stress and employing the simplest combinations of the basic invariants entering the general form of the yield condition. The proposed criterion involves specific terms accounting for the initial anisotropy, the deformation induced anisotropy and correlative terms between initial and induced anisotropy. The effects of prestrainings result in both isotropic and anisotropic hardening. An adequate experimental program, consisting of uniaxial tensile tests on oriented specimens of prestrained sheet-metal, was performed, in order to determine the specific form and the evolution of the anisotropic failure criterion for soft-steel subjected to different irreversible prestrainings. (orig.)

  19. COMPARATIVE STUDY ON METAL IONS ADSORPTION ON A LOW COST CARBONACEOUS ADSORBENT KINETIC EQUILIBRIUM AND MECHANISTIC STUDIES

    OpenAIRE

    S. Arivoli, M. Hema, C. Barathiraja

    2008-01-01

    A carbonaceous adsorbent prepared from an indigenous waste and treated by acid was tested for its efficiency in removing metal ions of Fe(II), Co(II) and Ni(II). The process parameters studied included agitation time, initial metal ion concentration, carbon dosage, pH, other ions and temperature. The kinetics of adsorption followed first order reaction equation and the rate was mainly controlled by intraparticle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibriu...

  20. Mechanistic study on ultrasound assisted pretreatment of sugarcane bagasse using metal salt with hydrogen peroxide for bioethanol production.

    Science.gov (United States)

    Ramadoss, Govindarajan; Muthukumar, Karuppan

    2016-01-01

    This study presents the ultrasound assisted pretreatment of sugarcane bagasse (SCB) using metal salt with hydrogen peroxide for bioethanol production. Among the different metal salts used, maximum holocellulose recovery and delignification were achieved with ultrasound assisted titanium dioxide (TiO2) pretreatment (UATP) system. At optimum conditions (1% H2O2, 4 g SCB dosage, 60 min sonication time, 2:100 M ratio of metal salt and H2O2, 75°C, 50% ultrasound amplitude and 70% ultrasound duty cycle), 94.98 ± 1.11% holocellulose recovery and 78.72 ± 0.86% delignification were observed. The pretreated SCB was subjected to dilute acid hydrolysis using 0.25% H2SO4 and maximum xylose, glucose and arabinose concentration obtained were 10.94 ± 0.35 g/L, 14.86 ± 0.12 g/L and 2.52 ± 0.27 g/L, respectively. The inhibitors production was found to be very less (0.93 ± 0.11 g/L furfural and 0.76 ± 0.62 g/L acetic acid) and the maximum theoretical yield of glucose and hemicellulose conversion attained were 85.8% and 77%, respectively. The fermentation was carried out using Saccharomyces cerevisiae and at the end of 72 h, 0.468 g bioethanol/g holocellulose was achieved. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis of pretreated SCB was made and its morphology was studied using scanning electron microscopy (SEM). The compounds formed during the pretreatment were identified using gas chromatography-mass spectrometry (GC-MS) analysis. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. COMPARATIVE STUDY ON METAL IONS ADSORPTION ON A LOW COST CARBONACEOUS ADSORBENT KINETIC EQUILIBRIUM AND MECHANISTIC STUDIES

    Directory of Open Access Journals (Sweden)

    S. Arivoli, M. Hema, C. Barathiraja

    2008-01-01

    Full Text Available A carbonaceous adsorbent prepared from an indigenous waste and treated by acid was tested for its efficiency in removing metal ions of Fe(II, Co(II and Ni(II. The process parameters studied included agitation time, initial metal ion concentration, carbon dosage, pH, other ions and temperature. The kinetics of adsorption followed first order reaction equation and the rate was mainly controlled by intraparticle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity obtained from the Langmuir isotherm plots was found around 28mg/g for all selected metal ions at an initial pH of 6. The temperature variation study showed that the metal ions adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying pH of the metal ion solutions. The type I and II isotherms obtained, positive H0 values, pH dependent results and desorption of metal ions in mineral acid suggests that the adsorption of metal ions on this type of adsorbent involves both chemisorption and physical adsorption mechanisms.

  2. Theoretical Studies of Spectroscopic Line Mixing in Remote Sensing Applications

    Science.gov (United States)

    Ma, Q.

    2015-12-01

    The phenomenon of collisional transfer of intensity due to line mixing has an increasing importance for atmospheric monitoring. From a theoretical point of view, all relevant information about the collisional processes is contained in the relaxation matrix where the diagonal elements give half-widths and shifts, and the off-diagonal elements correspond to line interferences. For simple systems such as those consisting of diatom-atom or diatom-diatom, accurate fully quantum calculations based on interaction potentials are feasible. However, fully quantum calculations become unrealistic for more complex systems. On the other hand, the semi-classical Robert-Bonamy (RB) formalism, which has been widely used to calculate half-widths and shifts for decades, fails in calculating the off-diagonal matrix elements. As a result, in order to simulate atmospheric spectra where the effects from line mixing are important, semi-empirical fitting or scaling laws such as the ECS and IOS models are commonly used. Recently, while scrutinizing the development of the RB formalism, we have found that these authors applied the isolated line approximation in their evaluating matrix elements of the Liouville scattering operator given in exponential form. Since the criterion of this assumption is so stringent, it is not valid for many systems of interest in atmospheric applications. Furthermore, it is this assumption that blocks the possibility to calculate the whole relaxation matrix at all. By eliminating this unjustified application, and accurately evaluating matrix elements of the exponential operators, we have developed a more capable formalism. With this new formalism, we are now able not only to reduce uncertainties for calculated half-widths and shifts, but also to remove a once insurmountable obstacle to calculate the whole relaxation matrix. This implies that we can address the line mixing with the semi-classical theory based on interaction potentials between molecular absorber and

  3. Theoretical studies of mutual diffusivities and surface properties in ...

    Indian Academy of Sciences (India)

    properties, thus underlining the importance of thermodynamic studies for liquid binary alloys. In this study, the transport and surface properties of Cd–Ga liquid alloys are determined from energetics and derivatives from experimental thermodynamic data. Cd–Ga alloys have been studied by many authors [14–16]. The alloy ...

  4. Heavy leptons: theoretical study of the implications of their existence

    International Nuclear Information System (INIS)

    Ragiadakos, C.

    1978-01-01

    The following points are studied: the possibility of an internal structure of heavy leptons and its manifestation; a study of the production of neutral heavy leptons in e + -e - collisions; consequences of the lumaton (heavy lepton having strong interactions) hypothesis; the introduction of a muon number violating mechanism in gauge theories. A gauge model characterized by the symmetries: left-right and quarks-leptons is also studied. A general review of the heavy leptons is given [fr

  5. A theoretical study on the B3 phases of ZnSe: Structural and ...

    Indian Academy of Sciences (India)

    KHOIROM Kabita

    2017-06-20

    Jun 20, 2017 ... fabrication of blue light emitting diodes, quantum well devices, infrared window lenses etc. It crystallizes in four-fold coordinated zinc-blende (ZB) structure that is in B3 phase under ambient pressure. ZnSe is intensively studied, experimentally as well as theoretically, using different methods. Theoretical ...

  6. Joint Experimental and Theoretical Study on Vibrational Excitation Cross Sections for Electron Collisions with Diacetylene

    Czech Academy of Sciences Publication Activity Database

    Čurík, Roman; Paidarová, Ivana; Allan, M.; Čársky, Petr

    2014-01-01

    Roč. 118, č. 41 (2014), s. 9734-9744 ISSN 1089-5639 R&D Projects: GA ČR GAP208/11/0452; GA MŠk LD14088 Institutional support: RVO:61388955 Keywords : diacetylenes * electron collision * theoretical study Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.693, year: 2014

  7. Theoretical study of diaquamalonatozinc(II) single crystal for ...

    Indian Academy of Sciences (India)

    MITESH CHAKRABORTY

    2017-11-28

    Nov 28, 2017 ... trons with non-zero spin [1,2]. Studies using electron magnetic resonance (EMR) spectroscopy or electron spin resonance (ESR) spectroscopy provide information about zero field splitting (ZFS) parameters and local site symmetry of transition metal ions doped in diamagnetic host [3,4]. Studies of electronic ...

  8. Experimental and theoretical study of precast beam-slab construction

    African Journals Online (AJOL)

    Part of the experimental program was dedicated to the study of mix design for the production of suitable hollow concrete beam tiles which bridge the space between the precast beam elements. The second part of the test program included the study of the precast beam element alone in order to investigate the response ...

  9. Theoretical Cognitive Principles Observed in the Social Studies Classroom

    Science.gov (United States)

    Walker, Juan; Langan, Elise; Kemp, Andrew; Pagnotti, John; Russell, William

    2016-01-01

    Pre-service elementary social studies teachers in the south eastern United States participated in a mixed methods study to determine the degree to which they utilized critical thinking skills. Insight Assessments administered analysis of their reflections, critical thinking skills, and dispositions test. The researchers developed a post survey for…

  10. Theoretical studies of non inductive current drive in compact toroids

    NARCIS (Netherlands)

    Farengo, R; Lifschitz, AF; Caputi, KI; Arista, NR; Clemente, RA

    Three non inductive current drive methods that can be applied to compact toroids axe studied. The use of neutral beams to drive current in field reversed configurations and spheromaks is studied using a Monte Carlo code that includes a complete ionization package and follows the exact particle

  11. Theoretical study on the structural effect of some organic ...

    African Journals Online (AJOL)

    A quantitative structure property relationship (QSPR) analysis of some organic compounds (imines or Schiff bases) is studied. The corrosion inhibition efficiencies of these imines have been studied by using AM1 (Austin model 1) Hamiltonian SCF-MO method and QSPR analysis. One of the most promising semiempirical ...

  12. Theoretical and Experimental Studies of Magneto-Rayleigh-Taylor Instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Yue Ying [University of Michigan, Ann Arbor, MI (United States); Gilgenbach, Ronald [University of Michigan, Ann Arbor, MI (United States)

    2013-07-07

    Magneto-Rayleigh-Taylor instability (MRT) is important to magnetized target fusion, wire-array z-pinches, and equation-of-state studies using flyer plates or isentropic compression. It is also important to the study of the crab nebula. The investigators performed MRT experiments on thin foils, driven by the mega-ampere linear transformer driver (LTD) facility completed in their laboratory. This is the first 1-MA LTD in the USA. Initial experiments on the seeding of MRT were performed. Also completed was an analytic study of MRT for a finite plasma slab with arbitrary magnetic fields tangential to the interfaces. The effects of magnetic shear and feedthrough were analyzed.

  13. Theoretical and experimental study of mixed solvent electrolytes

    International Nuclear Information System (INIS)

    Cummings, P.T.; O'Connell, J.P.

    1990-01-01

    In the original proposal to study mixed solvent electrolyte solutions, four major goals were formulated: fundamental modeling of mixed solvent electrolytes using numerically solved integral equation approximation theories; evaluation of intermolecular pair potential models by computer simulation of selected systems for comparison with experiment and the numerical integral equation studies; development of fundamentally based correlations for the thermodynamic properties of mixed solvent electrolyte solutions using analytically solvable statistical mechanical models; and extension of experimental database on mixed solvent electrolytes by performing vapor-liquid equilibrium measurements on selected systems. This paper discusses the progress on these goals

  14. Theoretical provisions for the discharge at TJ-1 (Preliminary study)

    International Nuclear Information System (INIS)

    Guasp, J.

    1981-01-01

    Using the transport code PLASMATOR a numerical study about the TJ-1 discharge (a Tokamak close to be installed at JEN) has been made, observing the behaviour under huge variations on the transport coefficients as well as on density and current. Noteworthy a scaling law of the kind τ E ∼n θ has been contested at not too high density, The model insensibility upon the initial values has been confirmed and the effects of variations on the recycling coefficient and the rate rise of current studied too. Finally comparisons with alternative models have been accomplished. (Author) 29 refs

  15. A theoretical study on the optical properties of black silicon

    Science.gov (United States)

    Ma, Shijun; Liu, Shuang; Xu, Qinwei; Xu, Junwen; Lu, Rongguo; Liu, Yong; Zhong, Zhiyong

    2018-03-01

    There is a wide application prospect in black silicon, especially in solar cells and photoelectric detectors. For further optimization of black silicon, it is important to study its optical properties. Especially, the influence of the surface nanostructures on these properties and the light propagation within the nanostructures are relevant. In this paper, two kinds of black silicon models are studied via the finite differences time domain method. The simulated reflectance spectra matches well with the measured curve. Also, the light intensity distribution within the nanostructures shows that near 80% of the incident light are redirected and subjected to internal reflection, which provides powerful support for the good light trapping properties of black silicon.

  16. A Theoretical Study of Subsurface Drainage Model Simulation of ...

    African Journals Online (AJOL)

    A three-dimensional variable-density groundwater flow model, the SEAWAT model, was used to assess the influence of subsurface drain spacing, evapotranspiration and irrigation water quality on salt concentration at the base of the root zone, leaching and drainage in salt affected irrigated land. The study was carried out ...

  17. Theoretical Study of Physiochemical Properties of Insulin-Like Growth

    African Journals Online (AJOL)

    dell

    biological problems, the empirical force fields, have great difficulty in simulating folding of. Insulin-like Growth Factor 1 (IGF-1). In an effort to understand the conformational preferences that may be attributed to stereoelectronic effects, a number of computational studies were carried out. Monte Carlo, Molecular Dynamics and ...

  18. Theoretical Study of Physiochemical Properties of Insulin-like ...

    African Journals Online (AJOL)

    The computational approach to studying structural changes in a wide range of physical and biological problems, the empirical force fields, have great difficulty in simulating folding of Insulin-like Growth Factor 1 (IGF-1). In an effort to understand the conformational preferences that may be attributed to stereoelectronic effects, ...

  19. Theoretical study of the catalytic desulfurization mechanism of ...

    African Journals Online (AJOL)

    The desulfurization process of compounds implicates two steps. The first step is the adsorption process on the catalytic site and the second, the breaking of the carbon-heteroatom bond leading to the heteroatom elimination. The adsorption process of thiiren have been studied and published in previous works. The results ...

  20. Theoretical Study of Spin Crossover in 30 Iron Complexes

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta

    2016-01-01

    Spin crossover was studied in 30 iron complexes using density functional theory to quantify the direction and magnitude of dispersion, relativistic effects, zero-point energies, and vibrational entropy. Remarkably consistent entropy−enthalpy compensation was identified. Zero-point energies favor...

  1. Theoretical study on the molecular and crystal structures of nitrogen ...

    Indian Academy of Sciences (India)

    of NF3 has been improved by a number of workers3–6 and has been patented. Nitrogen trifluoride can also be formed by direct fluorination of ammonia. It is a stable gas with strong oxidizing properties. It can be used as a potential oxidant for spacecraft propulsion. Decades ago, studies on the compound have been made: ...

  2. Connecting theoretical and empirical studies of trait-mediated interactions

    Czech Academy of Sciences Publication Activity Database

    Bolker, B.; Holyoak, M.; Křivan, Vlastimil; Rowe, L.; Schmitz, O.

    2003-01-01

    Roč. 84, č. 5 (2003), s. 1101-1114 ISSN 0012-9658 Institutional research plan: CEZ:AV0Z5007907 Keywords : community models * competition * empirical study Subject RIV: EH - Ecology, Behaviour Impact factor: 3.701, year: 2003

  3. A theoretical parametric study of Water Flooding | Ohirhian | Journal ...

    African Journals Online (AJOL)

    A multidimensional mathematical model derived by combining equation of continuity and Darcy's law and solved using the strongly implicit procedure (SIP) has been used to study the effects of permeability distribution, shape of the relative permeability and capillary pressure curves, ratio of water to oil viscosity, and amount ...

  4. Theoretical studies of the dynamics of chemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, A.F. [Argonne National Laboratory, IL (United States)

    1993-12-01

    Recent research effort has focussed on several reactions pertinent to combustion. The formation of the formyl radical from atomic hydrogen and carbon monoxide, recombination of alkyl radicals and halo-alkyl radicals with halogen atoms, and the thermal dissociation of hydrogen cyanide and acetylene have been studied by modeling. In addition, the inelastic collisions of NCO with helium have been investigated.

  5. Theoretical study (Lagrangian modeling) of turbulent particulate dispersion

    Science.gov (United States)

    Berlemont, A.; Grancher, M. S.; Desjonqueres, P.

    A study aimed at improving the prediction and knowledge of two phase phenomena in a turbomachine is presented. A code to three dimensionally simulate particle dispersion, taking account of turbulent droplet evaporation, and which can be easily integrated into the DIAMANT code, is developed. Lagrangian modeling of particle dispersion is used. The influence of turbulence on evaporation appears to be non-negligible and must therefore be taken into account in droplet turbulent transfer problems.

  6. A theoretical study on interaction of proline with gold cluster

    Indian Academy of Sciences (India)

    Abstract. Interaction of proline with gold cluster was studied using density functional theory (DFT). Two types of mixed basis sets UB3LYP/6-311++G ∪ LANL2MB and UB3LYP/6-311++G ∪ LANL2DZ were used for optimization of complex structures. Proline interacts with gold cluster either through one anchor bond, N–Au ...

  7. The Case Study Approach: Some Theoretical, Methodological and Applied Considerations

    Science.gov (United States)

    2013-06-01

    studies have a long history of use and account for a large portion of articles and books in various disciplines, such as psychology , sociology...photographs, videotapes, projective techniques and psychological testing, life histories and the like (Stake 1995; Tellis 1997; Yin 2009). Hence, case...Choudrie (2007) examined the behaviours of employees including understanding of the humanistic elements such as meta-abilities (i.e. cognitive skills

  8. Theoretical study of adsorption of lithium atom on carbon nanotube

    OpenAIRE

    Senami, Masato; Ikeda, Yuji; Fukushima, Akinori; Tachibana, Akitomo

    2011-01-01

    We investigate the adsorption of lithium atoms on the surface of the (12, 0) single wall carbon nanotube (SWCNT) by using ab initio quantum chemical calculations. The adsorption of one lithium atom on the inside of this SWCNT is favored compared to the outside. We check this feature by charge transfer and regional chemical potential density. The adsorption of multiple lithium atoms on the interior of the SWCNT is studied in terms of adsorption energy and charge transfer. We show that repulsiv...

  9. Theoretical study on the molecular and crystal structures of nitrogen ...

    Indian Academy of Sciences (India)

    The molecular and crystal structure of the adduct NF3·BF3 was studied computationally using density functional theory. It shows that the adduct exists in the form of a complex but is not ionic. The heats of formation in the gas and the condensed phase of the adduct are −1266.09 and −1276.37 kJ·mol−1, respectively, which ...

  10. Dynamic behavior of hybrid sodium bearings. Theoretical and experimental studies

    International Nuclear Information System (INIS)

    Guidez, J.; Juignet, N.; Queval, M.

    1981-08-01

    The primary sodium pump shaft lower section of a fast breeder reactor is guided by a hydrostatic sodium bearing. This recess type bearing is supplied via orifices restrictors. Sodium is sampled at hight pressure at the diffuser outlet and is then centrifuged towards the orifices restrictors. Bearing stiffness and damping data is essential for the study of rotor dynamic behavior. Two points in particular may then be studied: - calculation of rotor instability ranges and critical speeds, - dynamic behavior of the rotor in the event of an earthquake. As regards the bearing design, the problem is to obtain the pressure fields in the liquid film. The integration of these pressure fields will then give the stiffness coefficients. The damping coefficients can then be obtained by the same calculation after slight displacement. The Reynolds equation can be used to study the liquid film (under any conditions for the turbulent and inertia effects). Then the computer code DELPAL is explained that solves the modified Reynolds equation using a finite element method. The presentation of tests conducted in 1981 on the Super-Phenix 1 full scall bearing (diameter 850 mm) in water is made. In conclusion this paper describes a method for calculating the stiffness and damping matrices of a hydrostatic bearing using the DELPAL calculation code and shows the loop of behavior tests on a bearing with sinusoidal excitation. The results, obtained by calculation and by testing, are indispensable when calculating the dynamic behavior of the shaft line

  11. Comparative theoretical and experimental study on novel tri-quinoline system and its anticancer studies

    Science.gov (United States)

    Gayathri, Kasirajan; Radhika, Ramachandran; Shankar, Ramasamy; Malathi, Mahalingam; Savithiri, Krishnaswamy; Sparkes, Hazel A.; Howard, Judith A. K.; Mohan, Palathurai Subramaniam

    2017-04-01

    A novel compound 2-chloro-3,6-bis-(quinolin-8-yloxymethyl)-quinoline 3 bearing a tri-quinoline moiety has been synthesized from 2-chloro-3,6-dimethyl quinoline 1 and 8-hydroxy quinoline 2 using dry acetone and K2CO3 as a base. 3 has been characterized by using FT-IR, FT-Raman, UV-Vis, 1H NMR, 13C NMR spectra and single crystal X-ray diffraction methods. We have also made a combined experimental and theoretical study on the molecular structure, vibrational spectra, NMR, FT-IR, FT-Raman and UV-Vis spectra of 2-chloro-3,6-bis-(quinolin-8-yloxymethyl)-quinoline. The theoretical studies of the title compound have been evaluated by using density functional theory calculations using B3LYP/6-31+G(d,p) and M06-2X/6-31+G(d,p) level of theories. The calculated theoretical values were found to be in good agreement with the experimental findings. The single crystal structure 3 crystallized in the orthorhombic space group Pna21. The compound 3 exhibits higher cytotoxicity in human cervical cancer cell lines (HeLa) than human breast cancer cell lines (MCF7).

  12. Theoretical and numerical study of cyclotron in space charge conditions

    International Nuclear Information System (INIS)

    Cazoll, V.

    1988-11-01

    During the last decade, the need of high ion beam intensities urged the cyclotron laboratories to amplify the efforts to study the space charge effects in these machines. The cyclotron space charge effects are intimately linked to two specific features of this kind of accelerator; - the beam is formed of a succession of bunches having about the same size for transverse and longitudinal dimensions, - the radial and longitudinal motions are strongly coupled. The analytical model developed in this thesis explains some effects produced by the space charge forces. It describes the motion of an ion contained in a bunch. This ion moves under the effects of the guiding field forces, the accelerator cyclotron field forces and the space charge forces created by the other particles of the bunch. The solutions of the first order differential equations describe the small motion around one particle, which is taken as a reference particle. These solutions are valid in the vicinity of the bunch center, where the space charge forces are considered linear. The results of the model are compared with those obtained from a multiparticle code. This code has been already used successfully at GANIL (the Great National Heavy Ions Accelerator). The evolution of the whole beam has also been studied with this code, which takes into acount the non linear space charge effects and all the couplings. The results obtained by the numerical study of a proposed new injector for the cyclotrons of GANIL shows that it is possible to obtain an important increase of the beam intensity [fr

  13. Theoretical Studies of Optical Properties of Silver Nanoparticles

    International Nuclear Information System (INIS)

    Ye-Wan, Ma; Zhao-Wang, Wu; Li-Hua, Zhang; Jie, Zhang

    2010-01-01

    Optical properties of silver nanoparticles such as extinction, absorption and scattering efficiencies are studied based on Green's function theory. The numerical simulation results show that optical properties of silver nanoparticles are mainly dependent on their sizes and geometries; the localized plasmon resonance peak is red shifted when the dielectric constant of the particle's surrounding medium increases or when a substrate is presented. The influences of wave polarizations, the incident angles of light, the composite silver and multiply-layers on the plasmon resonance are also reported. The numerical simulation of optical spectra is a very useful tool for nanoparticle growth and characterization. (fundamental areas of phenomenology(including applications))

  14. Role of hot electron transport in scintillators: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Huihui [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, Key Lab. of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen Univ. (China); Li, Qi [Physical Sciences Division, IBM TJ Watson Research Center, Yorktown Heights, NY (United States); Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Lu, Xinfu; Williams, R.T. [Department of Physics, Wake Forest University, Winston Salem, NC (United States); Qian, Yiyang [College of Engineering and Applied Science, Nanjing University (China); Wu, Yuntao [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN (United States)

    2016-10-15

    Despite recent intensive study on scintillators, several fundamental questions on scintillator properties are still unknown. In this work, we use ab-initio calculations to determine the energy dependent group velocity of the hot electrons from the electronic structures of several typical scintillators. Based on the calculated group velocities and optical phonon frequencies, a Monte-Carlo simulation of hot electron transport in scintillators is carried out to calculate the thermalization time and diffusion range in selected scintillators. Our simulations provide physical insights on a recent trend of improved proportionality and light yield from mixed halide scintillators. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. A theoretical study on free monopolar spacial change

    International Nuclear Information System (INIS)

    Camargo, P.C. de.

    1975-01-01

    Assuming planar symmetry and an arbitrary charge distribution that spreads through the sample, the one-carrier free-space-charge motion is studied in insulators solids. Using the method of characteristics we can reduce the problem to the resolution of a system of two ordinary first order differential equations. Results are applied to linear, exponential and S.C.L. current charge distributions, under short-circuit conditions. The charge distribution for several times and the discharge currents are presented. The results are compared with those from an approximated method, based on variational principles. (author) [pt

  16. Theoretical study of adsorption of lithium atom on carbon nanotube

    Directory of Open Access Journals (Sweden)

    Masato Senami

    2011-12-01

    Full Text Available We investigate the adsorption of lithium atoms on the surface of the (12,0 single wall carbon nanotube (SWCNT by using ab initio quantum chemical calculations. The adsorption of one lithium atom on the inside of this SWCNT is favored compared to the outside. We check this feature by charge transfer and regional chemical potential density. The adsorption of multiple lithium atoms on the interior of the SWCNT is studied in terms of adsorption energy and charge transfer. We show that repulsive force between lithium atoms destabilizes a system for the large number of lithium atoms.

  17. Hydroxyl radical induced transformation of phenylurea herbicides: A theoretical study

    International Nuclear Information System (INIS)

    Mile, Viktória; Harsányi, Ildikó; Kovács, Krisztina; Földes, Tamás; Takács, Erzsébet; Wojnárovits, László

    2017-01-01

    Aromatic ring hydroxylation reactions occurring during radiolysis of aqueous solutions are studied on the example of phenylurea herbicides by Density Functional Theory calculations. The effect of the aqueous media is taken into account by using the Solvation Model Based on Density model. Hydroxyl radical adds to the ring because the activation free energies (0.4–47.2 kJ mol −1 ) are low and also the Gibbs free energies have high negative values ((−27.4) to (−5.9) kJ mol −1 ). According to the calculations in most of cases the ortho- and para-addition is preferred in agreement with the experimental results. In these reactions hydroxycyclohexadienyl type radicals form. In a second type reaction, when loss of chlorine atom takes place, OH/Cl substitution occurs without cyclohexadienyl type intermediate. - Highlights: • Attack of • OH to aniline, phenol, fenuron, monuron, diuron was studied by DFT. • Ortho-para directing is suggested with –NH 2 , –OH and –NHCON(CH 3 ) 2 groups. • • OH addition to the ring gives hydroxycyclohexadienyl radical. • Attack at C-Cl leads to • OH/Cl substitution without cyclohexadienyl intermediate.

  18. Structural and theoretical studies of mixed metal oxides

    International Nuclear Information System (INIS)

    Butler, V.

    1982-10-01

    Diffuse neutron scattering studies were made first on powdered samples of uranium/cerium oxide and, secondly, on single crystals of stoichiometric and reduced thorium/cerium oxide. The powder studies show that at low dopant concentrations, the cation distribution is random but, as the dopant concentration increases, considerable short range ordering takes place on the cation sublattice. The presence of oxygen vacancies at high temperature, when the cations are mobile, does not appear to affect the distribution of the cations. Powder neutron diffraction was carried out on stoichiometric and reduced samples of uranium/cerium oxide and, for comparison, on a reduced sample of 20 mole% CeO 2 in ThO 2 . In the former samples, separation of a second phase occurs on reduction of samples containing >= 20 mole% CeO 2 and, at all dopant concentrations, the level of reduction achieved is well below the expected value. The thorium/cerium oxide sample, on the other hand, is single-phase and fully reduced. Calculations performed using computer simulation techniques show that, in doped CeO 2 and ZrO 2 , the radius of the dopant ion is extremely important in determining the magnitude of the dopant-vacancy interaction and hence the ionic conductivity of the material. The results are discussed. (author)

  19. Experimental and theoretical study of cascade solar stills in Iran

    International Nuclear Information System (INIS)

    Tabrizi, F.F.; Sharak, A.Z.

    2009-01-01

    Due to low annual rainfall, most of Iran is dominated by arid and semi-arid areas. The solar radiation intensity is extremely high in most of the country. The need to produce fresh water from brackish water is considerably high, especially in dry regions. Desalination of brackish water may become a competitive potential water resource to meet potable water demand, and as the price of oil goes higher, using solar energy for water desalinisation becomes more economical. This paper presented a study that involved mathematical modeling of the first solar still in Iran. The cumulative fresh water production and water temperature were calculated as a function of time. The obtained results were verified by one month daily-based experimental data. The paper also provided background information on the Koshk village, situated in the south part of Iran near Badar Abbas city. Various investigations regarding meteorological conditions, economical considerations, and technical and operational appropriateness demonstrated that the cascade solar still is suitable for desalination of brackish water. 100 solar stills were installed at the site to provide potable water for a nearby village. It was concluded that the model could be used to simulate and optimize the effective design parameters in future studies. 6 refs., 7 figs

  20. Experimental and theoretical study of deformable mirror actuator arrays

    Science.gov (United States)

    Pilar, Jan; Bonora, Stefano; Lucianetti, Antonio; Jelinkova, Helena; Mocek, Tomas

    2015-01-01

    Deformable mirrors have gained increasing interest in many different fields of application including laser physics, and they are becoming a universal tool for correcting optical aberrations of laser beams especially in large scale laser systems. One of the most common types of deformable mirror is a bimorph design which uses two plates of piezomaterial to which single electrodes are connected. These electrodes form the actuator array and their layout defines the resulting performance of the mirror to some extent. In the end all types of deformable mirrors currently used use an actuator array of some sort. To estimate the significance and effect of different actuator layout and shapes of actuators, an experimental study was performed. Four different commonly used actuator arrays were compared using photo-controlled deformable mirror. Using such device allows to study the effect of actuator layout separately from all other effects, since the device remains the same including all its imperfections. The experimental results are compared with numerical simulations and discussion is presented.

  1. Theoretical study of the luminance distribution on the Venus disk

    International Nuclear Information System (INIS)

    Bigourd, C.; Deuze, J.L.; Devaux, C.; Herman, M.; Lenoble, J.

    1974-01-01

    The analysis of the sunlight scattered by Venus gives some insight upon its clouds. The measurements of polarized light are probably more sensitive to the nature of their constituents, and some recent studies seem to be able to give a satisfactory interpretation of this part of the scattered light. But the polarized light concerns the upper part of the clouds, and it is interesting to compare these with intensity measurements. The phase curves, for the integrated light, leave some indetermination, so we have studied if the intensity distribution on the Venus disk could give more accurate informations. This work based on some plates kindly communicated by A. Dolfus, and analysed at Meudon Observatory, is more a preliminary investigation of the sensitivity of the method than an interpretation of the partial results presented. A simple model, of homogeneous plane parallel cloud, has been used, and the influence of various parameters has been tested (single scattering albedo, refractive index of particles and size distribution, optical depth of the cloud). (Auth.)

  2. Singlet oxygen reactions with flavonoids. A theoretical-experimental study.

    Directory of Open Access Journals (Sweden)

    Javier Morales

    Full Text Available Detection of singlet oxygen emission, λ(max = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T, and the reactive reaction rate constant, k(r, for the reaction between singlet oxygen and several flavonoids. Values of k(T determined in deuterated water, ranging from 2.4×10(7 M(-1 s(-1 to 13.4×10(7 M(-1 s(-1, for rutin and morin, respectively, and the values measured for k(r, ranging from 2.8×10(5 M(-1 s(-1 to 65.7×10(5 M(-1 s(-1 for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

  3. Singlet oxygen reactions with flavonoids. A theoretical-experimental study.

    Science.gov (United States)

    Morales, Javier; Günther, Germán; Zanocco, Antonio L; Lemp, Else

    2012-01-01

    Detection of singlet oxygen emission, λ(max) = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T), and the reactive reaction rate constant, k(r), for the reaction between singlet oxygen and several flavonoids. Values of k(T) determined in deuterated water, ranging from 2.4×10(7) M(-1) s(-1) to 13.4×10(7) M(-1) s(-1), for rutin and morin, respectively, and the values measured for k(r), ranging from 2.8×10(5) M(-1) s(-1) to 65.7×10(5) M(-1) s(-1) for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

  4. C-H functionalization of sp(3) centers with aluminum: a computational and mechanistic study of the Baddeley reaction of decalin.

    Science.gov (United States)

    Lyall, Catherine L; Sato, Makoto; Uosis-Martin, Mario; Asghar, Syeda Farina; Jones, Matthew D; Williams, Ian H; Lewis, Simon E

    2014-10-01

    Decalin undergoes reaction with aluminum trichloride and acetyl chloride to form a tricyclic enol ether in good yield, as first reported by Baddeley. This eye-catching transformation, which may be considered to be an aliphatic Friedel-Crafts reaction, has not previously been studied mechanistically. Here we report experimental and computational studies to elucidate the mechanism of this reaction. We give supporting evidence for the proposition that, in the absence of unsaturation, an acylium ion acts as a hydride acceptor, forming a tertiary carbocation. Loss of a proton introduces an alkene, which reacts with a further acylium ion. A concerted 1,2-hydride shift/oxonium formation, followed by elimination, leads to formation of the observed product.

  5. Oxidation of alginate and pectate biopolymers by cerium(IV) in perchloric and sulfuric acid solutions: A comparative kinetic and mechanistic study.

    Science.gov (United States)

    Fawzy, Ahmed

    2016-03-15

    The kinetics of oxidation of alginate (Alg) and pectate (Pec) carbohydrate biopolymers was studied by spectrophotometry in aqueous perchloric and sulfuric acid solutions at fixed ionic strengths and temperature. In both acids, the reactions showed a first order dependence on [Ce(IV)], whereas the orders with respect to biopolymer concentrations are less than unity. In perchloric acid, the reactions exhibited less than unit orders with respect to [H(+)] whereas those proceeded in sulfuric acid showed negative fractional-first order dependences on [H(+)]. The effect of ionic strength and dielectric constant was studied. Probable mechanistic schemes for oxidation reactions were proposed. In both acids, the final oxidation products were characterized as mono-keto derivatives of both biopolymers. The activation parameters with respect to the slow step of the mechanisms were computed and discussed. The rate laws were derived and the reaction constants involved in the different steps of the mechanisms were calculated. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Theoretical study of the crossover into hydrodynamic regime in graphene

    Science.gov (United States)

    Ho, Derek; Yudhistira, Indra; Hu, Ben Yu-Kuang; Adam, Shaffique

    Experiments on graphene have recently succeeded in entering the hydrodynamic regime, as demonstrated by successful observations of strong violation of Wiedemann-Franz law, the Gurzhi effect and electronic Poiseuille flow. It is known that electronic systems enter the hydrodynamic regime when electron-electron scattering dominates over electron-impurity and electron-phonon scattering. However, a quantitative study of this transition from the Fermi liquid to hydrodynamic regime is still lacking. In view of this, we quantitatively analyze the electron-electron, electron-impurity and electron-phonon scattering rates as a function of temperature, charge doping and disorder (charge puddle) strength. This yields a quantitative understanding of the onset of hydrodynamic electronic behavior in graphene samples. This work is supported by the National Research Foundation of Singapore under its Fellowship program (NRF-NRFF2012-01) and by the Singapore Ministry of Education and Yale-NUS College through Grant No. R-607-265-01312.

  7. Theoretical study of lithium clusters by electronic stress tensor

    International Nuclear Information System (INIS)

    Ichikawa, Kazuhide; Nozaki, Hiroo; Komazawa, Naoya; Tachibana, Akitomo

    2012-01-01

    We study the electronic structure of small lithium clusters Li n (n = 2 ∼ 8) using the electronic stress tensor. We find that the three eigenvalues of the electronic stress tensor of the Li clusters are negative and degenerate, just like the stress tensor of liquid. This leads us to propose that we may characterize a metallic bond in terms of the electronic stress tensor. Our proposal is that in addition to the negativity of the three eigenvalues of the electronic stress tensor, their degeneracy characterizes some aspects of the metallic nature of chemical bonding. To quantify the degree of degeneracy, we use the differential eigenvalues of the electronic stress tensor. By comparing the Li clusters and hydrocarbon molecules, we show that the sign of the largest eigenvalue and the differential eigenvalues could be useful indices to evaluate the metallicity or covalency of a chemical bond.

  8. A theoretical-experimental study of backup bearings

    DEFF Research Database (Denmark)

    Lampe Linhares da Fonseca, Cesar Augusto

    The backup bearing is a mechanical component designed to improve the safety and reliability of Active Magnetic Bearings (AMBs). Rotors levitated by AMBs can be subjected to delevitation and consequently to impacts if a power loss happens because real-time active control is necessary to keep them...... running. When impacting on a stator surface, the rotor can develop a dangerous behavior caused by the friction force known as the full annular backward whirl. In this situation, the rotor will describe a trajectory around the surface of the bearing at a dominant superharmonic frequency and with large...... radial forces. Remaining in this condition, it may lead to permanent damage or total failure of the machine. This is why the backup bearing design has to be carefully planned and investigated as to whether it helps to protect the integrity of the machine. This PhD thesis provides a comprehensive study...

  9. Exergy performance of different space heating systems: A theoretical study

    DEFF Research Database (Denmark)

    Kazanci, Ongun Berk; Shukuya, Masanori; Olesen, Bjarne W.

    2016-01-01

    Three space heating systems (floor heating with different floor covering resistances, radiator heating with different working temperatures, warm-air heating with and without heat recovery) were compared using a natural gas fired condensing boiler as the heat source. For the floor heating systems......, the effects of floor covering resistance on the whole system performance were studied using two heat sources; a natural gas fired condensing boiler and an air-source heat pump. The heating systems were also compared in terms of auxiliary exergy use for pumps and fans. The low temperature floor heating system...... performed better than other systems in terms of exergy demand. The use of boiler as a heat source for a low-exergy floor heating system creates a mismatch in the exergy supply and demand. Although an air-source heat pump could be a better heat source, this depends on the origin of the electricity supplied...

  10. Theoretical Study of Watershed Eco-Compensation Standards

    Science.gov (United States)

    Yan, Dandan; Fu, Yicheng; Liu, Biu; Sha, Jinxia

    2018-01-01

    Watershed eco-compensation is an effective way to solve conflicts over water allocation and ecological destruction problems in the exploitation of water resources. Despite an increasing interest in the topic, the researches has neglected the effect of water quality and lacked systematic calculation method. In this study we reviewed and analyzed the current literature and proposedatheoretical framework to improve the calculation of co-compensation standard.Considering the perspectives of the river ecosystems, forest ecosystems and wetland ecosystems, the benefit compensation standard was determined by the input-output corresponding relationship. Based on the opportunity costs related to limiting development and water conservation loss, the eco-compensation standard was calculated.In order to eliminate the defects of eco-compensation implementation, the improvement suggestions were proposed for the compensation standard calculation and implementation.

  11. Hydrogen detection by a boron sheet: A theoretical study .

    Science.gov (United States)

    Dominguez, F. Javier; Novotny, Michal; Krstic, Predrag S.

    A single boron sheet is now considered as a new nanomaterial with promising applications in electronics and as a sensor device. In this study we present quantum-classical molecular dynamic (QCMD) calculation of reflection, adsorption, and transmission processes of hydrogen impacting at energy in range 0.25 to 100 eV on a single boron sheet. Quantum-mechanical component of our QCMD approach is self-consistent charge tight binding density functional theory method (SCC-DFTB,). We consider the corrugated boron sheet as our target, created experimentally, and compare our results with those reported for graphene, showing noticeable differences. Research supported by CONACyT postdoctoral scholarship to FJD and the Fulbright Comission (Grant 15160939) to MN. Results were obtained using the LI-red cluster at IACS.

  12. Hydroxyl radical induced transformation of phenylurea herbicides: A theoretical study

    Science.gov (United States)

    Mile, Viktória; Harsányi, Ildikó; Kovács, Krisztina; Földes, Tamás; Takács, Erzsébet; Wojnárovits, László

    2017-03-01

    Aromatic ring hydroxylation reactions occurring during radiolysis of aqueous solutions are studied on the example of phenylurea herbicides by Density Functional Theory calculations. The effect of the aqueous media is taken into account by using the Solvation Model Based on Density model. Hydroxyl radical adds to the ring because the activation free energies (0.4-47.2 kJ mol-1) are low and also the Gibbs free energies have high negative values ((-27.4) to (-5.9) kJ mol-1). According to the calculations in most of cases the ortho- and para-addition is preferred in agreement with the experimental results. In these reactions hydroxycyclohexadienyl type radicals form. In a second type reaction, when loss of chlorine atom takes place, OH/Cl substitution occurs without cyclohexadienyl type intermediate.

  13. 1,2-Propanediol. Comprehensive experimental and theoretical study

    International Nuclear Information System (INIS)

    Verevkin, Sergey P.; Emel'yanenko, Vladimir N.; Nell, Gernot

    2009-01-01

    The standard (p 0 =0.1MPa) molar enthalpy of formation at the temperature 298.15 K of the liquid 1,2-propanediol was measured using combustion calorimetry. Molar enthalpies of vaporization of isomeric 1,2-propanediols were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. Thermochemical investigations of 1,2-ethanediol and 1,2-propanediol available in the literature were collected and combined with own experimental results. This collection together with the new experimental results reported here has helped to resolve contradictions in the available sublimation enthalpies data and to recommend consistent and reliable set of vaporization and formation enthalpies for both diols under study. Ab initio calculations of gaseous molar enthalpy of formation of 1,2-ethanediol and 1,2-propanediol have been performed using the G3MP2 method and results are in excellent agreement with the selected experimental data.

  14. Theoretical Study of Sodium-Water Surface Reaction Mechanism

    Science.gov (United States)

    Kikuchi, Shin; Kurihara, Akikazu; Ohshima, Hiroyuki; Hashimoto, Kenro

    Computational study of the sodium-water reaction at the gas (water) - liquid (sodium) interface has been carried out using the ab initio (first-principle) method. A possible reaction channel has been identified for the stepwise OH bond dissociations of a single water molecule. The energetics including the binding energy of a water molecule on the sodium surface, the activation energies of the bond cleavages, and the reaction energies, have been evaluated, and the rate constants of the first and second OH bond-breakings have been compared. It was found that the estimated rate constant of the former was much larger than the latter. The results are the basis for constructing the chemical reaction model used in a multi-dimensional sodium-water reaction code, SERAPHIM, being developed by Japan Atomic Energy Agency (JAEA) toward the safety assessment of the steam generator (SG) in a sodium-cooled fast reactor (SFR).

  15. Theoretical study of sodium-water surface reaction mechanism

    International Nuclear Information System (INIS)

    Kikuchi, Shin; Kurihara, Akikazu; Ohshima, Hiroyuki; Hashimoto, Kenro

    2012-01-01

    Computational study of the sodium-water reaction at the gas (water) - liquid (sodium) interface has been carried out using the ab initio (first-principle) method. A possible reaction channel has been identified for the stepwise OH bond dissociations of a single water molecule. The energetics including the binding energy of a water molecule on the sodium surface, the activation energies of the bond cleavages, and the reaction energies, have been evaluated, and the rate constants of the first and second OH bond-breakings have been compared. It was found that the estimated rate constant of the former was much larger than the latter. The results are the basis for constructing the chemical reaction model used in a multi-dimensional sodium-water reaction code, SERAPHIM, being developed by Japan Atomic Energy Agency (JAEA) toward the safety assessment of the steam generator (SG) in a sodium-cooled fast reactor (SFR). (author)

  16. Chemical functionalization of graphene via aryne cycloaddition: a theoretical study.

    Science.gov (United States)

    Zhao, Jing-xiang; Wang, Hong-xia; Gao, Bo; Wang, Xiao-guang; Cai, Qing-hai; Wang, Xuan-zhang

    2012-06-01

    Chemical functionalization of graphene provides a promising route to improve its solubility in water and organic solvents as well as modify its electronic properties, thus significantly expanding its potential applications. In this article, by using density functional theory (DFT) methods, we have studied the effects of the chemical functionalization of graphenes via aryne cycloaddition on its properties. We found that the adsorption of an isolated aryne group on the graphene sheet is very weak with the adsorption energy of -0.204 eV, even though two new single C-C interactions are formed between the aryne group and the graphene. However, the interaction of graphene with the aryne group can be greatly strengthened by (i) substituting the H-atoms in aryne group with F-, Cl-, -NO(2) (electron-withdrawing capability), or CH(3)-group (electron-donating capability), and (ii) increasing the coverage of the adsorbed aryne groups on the graphene sheet. As expected, the strongest bonding is found on the graphene edges, in which the adsorbed aryne groups prefer to be far away from each other. Interestingly, chemical functionalization with aryne groups leads to an opening of the band gap of graphene, which is dependent on the coverage of the adsorbed aryne groups. The present work provides an insight into the modifications of graphene with aryne groups in experiment.

  17. Theoretical study of spin Hall effect in conjugated Organic semiconductors

    Science.gov (United States)

    Mahani, M. R.; Delin, A.

    The spin Hall effect (SHE), a direct conversion between electronic and spin currents, is a rapidly growing branch of spintronics. The study of SHE in conjugated polymers has gained momentum recently due to the weak spin-orbit couplings and hyperfine interactions in these materials. Our calculations of SHE based on the recent work, are the result of the misalignment of pi-orbitals in triads consisting of three molecules. In disordered organics, where the electronic conduction is through hopping of the electrons among randomly oriented molecules, instead of identifying a hopping triad to represent the entire system, we numerically solve the master equations for electrical and spin hall conductivities by summing the contributions from all triads in a sufficiently large system. The interference between the direct and indirect hoppings in these triads leads to SHE proportional to the orientation vector of molecule at the first order of spin-orbit coupling. Hence, our results show, the degree of molecular alignment as well as the strength of the spin-orbit coupling can be used to control the SHE in organics.

  18. Theoretical study for the interlamellar aminoalcohol functionalization of kaolinite

    International Nuclear Information System (INIS)

    Hou, Xin-Juan; Li, Huiquan; Liu, Qinfu; Cheng, Hongfei; He, Peng; Li, Shaopeng

    2015-01-01

    Graphical abstract: - Highlights: • The results indicated that aminoalcohols exist with a mixing of intercalation and grafting. • Aminoalcohols can form strong hydrogen bonds with Al octahedral sheet. • The interaction between aminoalcohols and Si tetrahedral sheet are mainly attributed by vdW force. • Aminoalcohols grafting or intercalating on kaolinite have strong reactivity as electron donors. - Abstract: Fundamental problems related to aminoalcohols intercalating on kaolinite were investigated by using density functional theory method. This study examines the adsorption modes of diethanolamine and triethanolamine on kaolinite, the role of hydrogen bonds and van der Waals (vdW) forces between aminoalcohols and interlayer of kaolinite, and the change of molecular orbital occupancies of functionalized kaolinite. Results show that functionalized kaolinite is physically intercalated and covalently grafted by aminoalcohols. Non-covalent interaction analysis provides a visualized description that intercalated aminoalcohols form strong hydrogen bonds with Al octahedral sheet, and the interaction between aminoalcohols and Si tetrahedral sheet is mainly attributed to weak vdW force. The analysis of molecular orbital occupancies for kaolinite complex showed that the functionalized kaolinite has strong chemical reactivity as electron donors on the sites of grafted or intercalated aminoalcohols for further chemical reaction with other materials

  19. Theoretical and numerical study of heat transfer deterioration in HPLWR

    International Nuclear Information System (INIS)

    Palko, D.; Anglart, H.

    2007-01-01

    A numerical investigation of the Heat Transfer Deterioration (HTD) phenomena is performed using the low-Re k - ω turbulence model. Steady state Reynolds-averaged Navier-Stokes equations are solved together with equations for the transport of enthalpy and turbulence. Equations are solved for the supercritical water flow at different pressures, using water properties from the standard IAPWS tables. All cases are extensively validated against experimental data. The influence of buoyancy on the HTD is demonstrated for different mass flow rates in the heated pipes. Numerical results prove that the RANS low-Re turbulence modeling approach is fully capable to simulate the heat transfer in pipes with the water flow at supercritical pressures. A study of buoyancy influence shows that for the low mass flow rates of coolant, the influence of buoyancy forces on the heat transfer in heated pipes is significant. For the high flow rates, buoyancy influence could be neglected and there are clearly other mechanisms causing the decrease in heat transfer at high coolant flow rates. (author)

  20. Theoretical study of bismuth-doped cadmium telluride

    Science.gov (United States)

    Menendez-Proupin, E.; Rios-Gonzalez, J. A.; Pena, J. L.

    Cadmium telluride heavily doped with bismuth has been proposed as an absorber with an intermediate band for solar cells. Increase in the photocurrent has been shown recently, although the overall cell efficiency has not improved. In this work, we study the electronic structure and the formation energies of the defects associated to bismuth impurities. We have performed electronic structure calculations within generalized density functional theory, using the exchange-correlation functional HSE(w) , where the range-separation parameter w has been tuned to reproduce the CdTe bandgap. Improving upon previous reports, we have included the spin-orbit interaction, which modifies the structure of the valence band and the energy levels of bismuth. We have found that interstitial Bi (Bii) tends to occupy Cd vacancies, cadmium substitution (BiCd) creates single donor level, while tellurium substitution (BiTe) is a shallow single acceptor. We investigate the interaction between these point defects and how can they be combined to create a partially filled intermediate band. Supported by FONDECYT Grant 1130437, CONACYT-SENER SUSTENTABILIDAD ENERGETICA/project CeMIE-Sol PY-207450/25 and PY-207450/26. JARG acknowledges CONACYT fellowship for research visit. Powered@NLHPC (ECM-02).

  1. Theoretical study for the interlamellar aminoalcohol functionalization of kaolinite

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Xin-Juan [Key Laboratory of Green Process and Engineering, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Li, Huiquan, E-mail: hqli@home.ipe.ac.cn [Key Laboratory of Green Process and Engineering, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Liu, Qinfu; Cheng, Hongfei [School of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083 (China); He, Peng; Li, Shaopeng [Key Laboratory of Green Process and Engineering, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China)

    2015-08-30

    Graphical abstract: - Highlights: • The results indicated that aminoalcohols exist with a mixing of intercalation and grafting. • Aminoalcohols can form strong hydrogen bonds with Al octahedral sheet. • The interaction between aminoalcohols and Si tetrahedral sheet are mainly attributed by vdW force. • Aminoalcohols grafting or intercalating on kaolinite have strong reactivity as electron donors. - Abstract: Fundamental problems related to aminoalcohols intercalating on kaolinite were investigated by using density functional theory method. This study examines the adsorption modes of diethanolamine and triethanolamine on kaolinite, the role of hydrogen bonds and van der Waals (vdW) forces between aminoalcohols and interlayer of kaolinite, and the change of molecular orbital occupancies of functionalized kaolinite. Results show that functionalized kaolinite is physically intercalated and covalently grafted by aminoalcohols. Non-covalent interaction analysis provides a visualized description that intercalated aminoalcohols form strong hydrogen bonds with Al octahedral sheet, and the interaction between aminoalcohols and Si tetrahedral sheet is mainly attributed to weak vdW force. The analysis of molecular orbital occupancies for kaolinite complex showed that the functionalized kaolinite has strong chemical reactivity as electron donors on the sites of grafted or intercalated aminoalcohols for further chemical reaction with other materials.

  2. Theoretical study of the relativistic molecular rotational g-tensor

    International Nuclear Information System (INIS)

    Aucar, I. Agustín; Gomez, Sergio S.; Giribet, Claudia G.; Ruiz de Azúa, Martín C.

    2014-01-01

    An original formulation of the relativistic molecular rotational g-tensor valid for heavy atom containing compounds is presented. In such formulation, the relevant terms of a molecular Hamiltonian for non-relativistic nuclei and relativistic electrons in the laboratory system are considered. Terms linear and bilinear in the nuclear rotation angular momentum and an external uniform magnetic field are considered within first and second order (relativistic) perturbation theory to obtain the rotational g-tensor. Relativistic effects are further analyzed by carrying out the linear response within the elimination of the small component expansion. Quantitative results for model systems HX (X=F, Cl, Br, I), XF (X=Cl, Br, I), and YH + (Y=Ne, Ar, Kr, Xe, Rn) are obtained both at the RPA and density functional theory levels of approximation. Relativistic effects are shown to be small for this molecular property. The relation between the rotational g-tensor and susceptibility tensor which is valid in the non-relativistic theory does not hold within the relativistic framework, and differences between both molecular parameters are analyzed for the model systems under study. It is found that the non-relativistic relation remains valid within 2% even for the heavy HI, IF, and XeH + systems. Only for the sixth-row Rn atom a significant deviation of this relation is found

  3. Theoretical study of the relativistic molecular rotational g-tensor

    Energy Technology Data Exchange (ETDEWEB)

    Aucar, I. Agustín, E-mail: agustin.aucar@conicet.gov.ar; Gomez, Sergio S., E-mail: ssgomez@exa.unne.edu.ar [Institute for Modeling and Technological Innovation, IMIT (CONICET-UNNE) and Faculty of Exact and Natural Sciences, Northeastern University of Argentina, Avenida Libertad 5400, W3404AAS Corrientes (Argentina); Giribet, Claudia G.; Ruiz de Azúa, Martín C. [Physics Department, Faculty of Exact and Natural Sciences, University of Buenos Aires and IFIBA CONICET, Ciudad Universitaria, Pab. I, 1428 Buenos Aires (Argentina)

    2014-11-21

    An original formulation of the relativistic molecular rotational g-tensor valid for heavy atom containing compounds is presented. In such formulation, the relevant terms of a molecular Hamiltonian for non-relativistic nuclei and relativistic electrons in the laboratory system are considered. Terms linear and bilinear in the nuclear rotation angular momentum and an external uniform magnetic field are considered within first and second order (relativistic) perturbation theory to obtain the rotational g-tensor. Relativistic effects are further analyzed by carrying out the linear response within the elimination of the small component expansion. Quantitative results for model systems HX (X=F, Cl, Br, I), XF (X=Cl, Br, I), and YH{sup +} (Y=Ne, Ar, Kr, Xe, Rn) are obtained both at the RPA and density functional theory levels of approximation. Relativistic effects are shown to be small for this molecular property. The relation between the rotational g-tensor and susceptibility tensor which is valid in the non-relativistic theory does not hold within the relativistic framework, and differences between both molecular parameters are analyzed for the model systems under study. It is found that the non-relativistic relation remains valid within 2% even for the heavy HI, IF, and XeH{sup +} systems. Only for the sixth-row Rn atom a significant deviation of this relation is found.

  4. Canister displacement in KBS-3V. A theoretical study

    International Nuclear Information System (INIS)

    Boergesson, Lennart; Hernelind, Jan

    2006-02-01

    The vertical displacement of the canister in the KBS-3V concept has been studied in a number of consolidation and creep calculations using the FE-program ABAQUS. The creep model used for the calculations is based on Singh-Mitchell's creep theory, which has been adapted to and verified for the buffer material MX-80 in earlier tests. A porous elastic model with Drucker-Prager plasticity has been used for the consolidation calculations. For simplicity the buffer has been assumed to be water saturated from start. In one set of calculations only the consolidation and creep in the buffer without considering the interaction with the backfill was studied. In the other set of calculations the interaction with the backfill was included for a backfill consisting of an in situ compacted mixture of 30% bentonite and 70% crushed rock. The motivation to also study the behaviour of the buffer alone was that the final choice of backfill material and backfilling technique is not made yet so that set of calculations simulates a backfill that has identical properties with the buffer. The two cases represent two extreme cases, one with a backfill that has a low stiffness and the lowest allowable swelling pressure and one that has the highest possible swelling pressure and stiffness. The base cases in the calculations correspond to the final average density at saturation of 2,000 kg/m 3 with the expected swelling pressure of 7 MPa in a buffer. In order to study the sensitivity of the system to loss in bentonite mass and swelling pressure seven additional calculations were done with reduced swelling pressure down to 80 kPa corresponding to a density at water saturation of about 1,500 kg/m 3 . The calculations included two stages, where the first stage models the swelling and consolidation that takes place in order for the buffer to reach force equilibrium. This stage takes place during the saturation phase and the subsequent consolidation/swelling phase. The second stage models the

  5. Enhanced piezoelectricity of monolayer phosphorene oxides: a theoretical study.

    Science.gov (United States)

    Yin, Huabing; Zheng, Guang-Ping; Gao, Jingwei; Wang, Yuanxu; Ma, Yuchen

    2017-10-18

    Two-dimensional (2D) piezoelectric materials have potential applications in miniaturized sensors and energy conversion devices. In this work, using first-principles simulations at different scales, we systematically study the electronic structures and piezoelectricity of a series of 2D monolayer phosphorene oxides (POs). Our calculations show that the monolayer POs have tunable band gaps along with remarkable piezoelectric properties. The calculated piezoelectric coefficient d 11 of 54 pm V -1 in POs is much larger than those of 2D transition metal dichalcogenide monolayers and the widely used bulk α-quartz and AlN, and almost reaches the level of the piezoelectric effect in recently discovered 2D GeS. Furthermore, two other considerable piezoelectric coefficients, i.e., d 31 and d 26 with values of -10 pm V -1 and 21 pm V -1 , respectively, are predicted in some monolayer POs. We also examine the correlation between the piezoelectric coefficients and energy stability. The enhancement of piezoelectricity for monolayer phosphorene by oxidation will broaden the applications of phosphorene and phosphorene derivatives in nano-sized electronic and piezotronic devices.

  6. Thermochemical study of cyanopyrazines: Experimental and theoretical approaches

    International Nuclear Information System (INIS)

    Miranda, Margarida S.; Morais, Victor M.F.; Matos, M. Agostinha R.

    2006-01-01

    The standard (p - bar =0.1MPa) molar energy of combustion, at T=298.15K, of crystalline 2,3-dicyanopyrazine was measured by static bomb calorimetry, in oxygen atmosphere. The standard molar enthalpy of sublimation, at T=298.15K, was obtained by Calvet Microcalorimetry, allowing the calculation of the standard molar enthalpy of formation of the compound, in the gas phase, at T=298.15K: Δ f H m - bar (g)=(518.7+/-3.4)kJ.mol -1 . In addition, the geometries of all cyanopyrazines were obtained using density functional theory with the B3LYP functional and two basis sets: 6-31G* and 6-311G**. These calculations were then used for a better understanding of the relation between structure and energetics of the cyanopyrazine systems. These calculations also reproduce measured standard molar enthalpies of formation with some accuracy and do provide estimates of this thermochemical parameter for those compounds that could not be studied experimentally, namely the tri- and tetracyanopyrazines: the strong electron withdrawing cyano group on the pyrazine ring makes cyanopyrazines highly destabilized compounds

  7. Wave-Created Mud Suspensions: A Theoretical Study

    Directory of Open Access Journals (Sweden)

    Jochen Kämpf

    2018-03-01

    Full Text Available We studied wave-created high-density mud suspensions (fluid mud using a one-dimensional water column (1DV model that includes k-ε turbulence closure at a high vertical resolution with a vertical grid spacing of 1 mm. The k-ε turbulence model includes two sediment-related dissipation terms associated with vertical density stratification and viscous drag of flows around sediment particles. To this end, the calibrated model reproduces the key characteristics (maximum concentration and thickness of fluid mud layers created in laboratory experiments over a large range of wave velocities from 10 to 55 cm/s. The findings demonstrate that the equilibrium near-bed mud concentration, Cb, is solely determined from the balance between erosion and deposition fluxes, whereas the thickness of the fluid mud layer is mainly controlled by sediment-induced density stratification, which dissipates turbulence and hence eliminates turbulent sediment diffusivity at the top of the fluid mud layer, the lutocline. Our model stands in contrast to those that suggest that upward sediment diffusion is close to zero at the interface between the fluid mud layer and the overlying fluid. Instead, our model suggests that the upward diffusive flux of fluid mud flows peak at the lutocline and is compensated for enhanced settling fluxes just above it. Our model findings also support the existence of the gelling-ignition process, which is critical for the development of fluid mud beds in modern sedimentary environments.

  8. Theoretical Framework of the filmed Interview in Communication Studies

    Directory of Open Access Journals (Sweden)

    LEBTAHI Yannick

    2016-07-01

    Full Text Available In the Social Sciences today, there are a variety of ways to approach the various areas of investigation and a wide range of observational methods. Depending on academic background and research interests, researchers explore and emphasize certain approaches and categorizations at the expense of others in the implementation of their audiovisual investigations. These observations lead us to first question the definition of image in its connection to the object of research and its status and, secondly, to identify the diversity of current practices and uses. Indeed, the status of an image changes according to the media used and the contexts of reception. The circulation of images promotes exchange and connection between the various groups of actors. If we awkwardly accompany images, we risk unwittingly betraying their original meaning. Furthermore, there is the possibility of conflicts or unintended distortions linked to the activities of projection and identification. Our goal will be to propose a methodological framework and establish an initial model for all researchers in Communication Studies using the audiovisual method. Finally, the researcher accepts not only to properly conduct his research, but also to present an audiovisual project taking into account from the start advantages, constraints, issues of influence and scientific impact.

  9. Theoretical Study of Ethylene Oligomerization by an Organometallic Nickel Catalyst.

    Science.gov (United States)

    Fan, L.; Krzywicki, A.; Somogyvari, A.; Ziegler, T.

    1996-06-19

    The mechanism for ethylene oligomerization by (acac)NiH has been studied using density functional theory (DFT). The transition states for chain propagation and chain termination were optimized and the related reaction barriers calculated. Several possible mechanisms were considered for the chain termination step. Chain termination by beta-hydrogen elimination was found to be energetically unfavorable, and is not likely to be important. Instead, beta-hydrogen transfer to the incoming ethylene unit seems to be operative. The most favorable beta-hydrogen transfer pathway has two transition states. The first leads from a weak pi-complex between an incoming ethylene unit and (acac)NiCH(2)CH(2)R to an intermediate in which the two olefins C(2)H(4) and H(2)CCHR both are strongly pi-complexed to the nickel hydride (acac)NiH. The second barrier takes the intermediate to another weak pi-complex between (acac)NiCH(2)CH(3) and H(2)C=CHR from which the oligomer H(2)C=CHR can be released and the catalyst (acac)NiCH(2)CH(3) regenerated. Due to the mechanism of chain termination, the actual catalyst is proposed to be (acac)NiCH(2)CH(3) whereas (acac)NiH serves as a precursor or precatalyst.

  10. Benchmark thermodynamic properties of methylanisoles: Experimental and theoretical study

    International Nuclear Information System (INIS)

    Emel’yanenko, Vladimir N.; Zaitseva, Ksenia V.; Agapito, Filipe; Martinho Simões, José A.; Verevkin, Sergey P.

    2015-01-01

    Highlights: • Thermochemistry of 2-, 3-, and 4-methylanisoles was studied. • Liquid state enthalpies of formation were measured by calorimetry. • Vaporisation enthalpies were derived from by transpiration method. • Ab initio enthalpies of formation are in excellent agreement with experiment. • A new paradigm for obtaining thermochemistry of liquid compounds was suggested. - Abstract: Accurate standard molar enthalpy of formation values in the liquid phase can be obtained by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporisation. The procedure is illustrated for 2-, 3-, and 4-methyl-anisoles. Using the W1-F12 and G4 quantum-chemical methods, the gas-phase enthalpies of formation of these compounds at T = 298.15 K were computed. Molar enthalpies of vaporisation for these isomers were measured by the transpiration method. Combining the experimental and the high-level ab initio values, the standard molar enthalpies of formation in the liquid phase for all three isomers were derived and compared with those determined for 2- and 4-methyl-anisoles by using combustion calorimetry

  11. A theoretical study on vomitoxin and its tautomers

    Energy Technology Data Exchange (ETDEWEB)

    Tuerker, Lemi [Middle East Technical University, Department of Chemistry, 06531 Ankara (Turkey)], E-mail: lturker@metu.edu.tr; Guemues, Selcuk [Middle East Technical University, Department of Chemistry, 06531 Ankara (Turkey); Yuezuencue Yil Universitesi, Kimya Boeluemue, 65080 Kampues, Van (Turkey)

    2009-04-15

    In the present work, the structural and electronic properties of vomitoxin (deoxynivalenol, a mycotoxin) and all of its possible tautomers have been investigated by the application of B3LYP/6-31G(d,p) type quantum chemical calculations. According to the results of the calculations, tautomer V{sub 4} has been found to be the most stable one among all the structures both in the gas and aqueous phases. The calculations also indicated that, vomitoxin and V{sub 2} possess the deepest and the highest lying HOMO levels, respectively. Hence, V{sub 2} is to be more susceptible to oxidations than the others. On the other hand, V{sub 5}(S) and vomitoxin have the lowest and the next lowest LUMO energies, respectively. Whereas, V{sub 1} and V{sub 2} possess quite highly lying (within the group) LUMO energy levels which result in comparatively unfavorable reduction potentials. Some important geometrical and physicochemical properties and the calculated IR spectra of the systems have also been reported in the study.

  12. Theoretical and computational studies in protein folding, design, and function

    Science.gov (United States)

    Morrissey, Michael Patrick

    2000-10-01

    In this work, simplified statistical models are used to understand an array of processes related to protein folding and design. In Part I, lattice models are utilized to test several theories about the statistical properties of protein-like systems. In Part II, sequence analysis and all-atom simulations are used to advance a novel theory for the behavior of a particular protein. Part I is divided into five chapters. In Chapter 2, a method of sequence design for model proteins, based on statistical mechanical first-principles, is developed. The cumulant design method uses a mean-field approximation to expand the free energy of a sequence in temperature. The method successfully designs sequences which fold to a target lattice structure at a specific temperature, a feat which was not possible using previous design methods. The next three chapters are computational studies of the double mutant cycle, which has been used experimentally to predict intra-protein interactions. Complete structure prediction is demonstrated for a model system using exhaustive, and also sub-exhaustive, double mutants. Nonadditivity of enthalpy, rather than of free energy, is proposed and demonstrated to be a superior marker for inter-residue contact. Next, a new double mutant protocol, called exchange mutation, is introduced. Although simple statistical arguments predict exchange mutation to be a more accurate contact predictor than standard mutant cycles, this hypothesis was not upheld in lattice simulations. Reasons for this inconsistency will be discussed. Finally, a multi-chain folding algorithm is introduced. Known as LINKS, this algorithm was developed to test a method of structure prediction which utilizes chain-break mutants. While structure prediction was not successful, LINKS should nevertheless be a useful tool for the study of protein-protein and protein-ligand interactions. The last chapter of Part I utilizes the lattice to explore the differences between standard folding, from

  13. A theoretical study of bubble motion in surfactant solutions

    Science.gov (United States)

    Wang, Yanping

    1999-08-01

    We examine the effect of surfactants on a spherical gas bubble rising steadily in an infinite fluid at low and order one Reynolds number with order one and larger Peclet numbers. Our mathematical model is based on the Navier-Stokes equations coupled with a convection- diffusion equation together with appropriate interfacial conditions. The nonlinearity of the equations and boundary conditions, and the coupling between hydrodynamics and surfactant transport make the problem very challenging. When a bubble rises in a fluid containing surface-active agents, surfactant adsorbs onto the bubble surface at the leading edge, convects to the trailing edge by the surface flow and desorbs into the bulk along the interface. This adsorption develops a surface concentration gradient on the interface that makes the surface tension at the back end relatively lower than that at the front end, and thus retards the bubble velocity. Because of surfactant impurities unavoidably present in materials, this retardation can cause a problem in materials processing in space and glass processing when bubbles are created during chemical reactions. Thus the study of how to remobilize (remove the surfactant gradient on the surface) the bubble surface becomes necessary. Many studies have been done on this retarding effects of the surfactant on a moving bubble. However, most were focused on the retarding effect due to a trace amount of surfactant, in which case the bubble velocity monotonically decreases as the bulk concentration increases. The question of how to remobilize the bubble surface remains unanswered. In this work, we will show that the bubble velocity can be controlled by remobilizing the bubble interface using the surfactant concentration. This technique not only can be used to maximize the bubble velocity, but also can be used to maximize mass transfer on purifying materials and extracting materials from mixtures. In the first part of the work, we illustrate numerically that the

  14. Theoretical and experimental studies on emissions from wood combustion

    Energy Technology Data Exchange (ETDEWEB)

    Skreiberg, Oeyvind

    1997-12-31

    This thesis discusses experiments on emissions from wood log combustion and single wood particle combustion, both caused by incomplete combustion and emissions of nitric and nitrous oxide, together with empirical and kinetic NO{sub x} modelling. Experiments were performed in three different wood stoves: a traditional stove, a staged air stove and a stove equipped with a catalytic afterburner. Ideally, biomass fuel does not give a net contribution to the greenhouse effect. However, incomplete combustion was found to result in significant greenhouse gas emissions. Empirical modelling showed the excess air ratio and the combustion chamber temperature to be the most important input variables controlling the total fuel-N to NO{sub x} conversion factor. As the result of an international round robin test of a wood stove equipped with a catalytic afterburner, particle emission measurements were found to be the best method to evaluate the environmental acceptability of the tested stove, since the particle emission level was least dependent of the national standards, test procedures and calculation procedures used. In batch single wood particle combustion experiments on an electrically heated small-scale fixed bed reactor the fuel-N to NO conversion factor varied between 0.11-0.86 depending on wood species and operating conditions. A parameter study and homogeneous kinetic modelling on a plug flow reactor showed that, depending on the combustion compliance in question, there is an optimum combination of primary excess air ratio, temperature and residence time that gives a maximum conversion of fuel-N to N{sub 2}. 70 refs., 100 figs., 26 tabs.

  15. Absorption heat cycles. An experimental and theoretical study

    International Nuclear Information System (INIS)

    Abrahamsson, K.

    1993-09-01

    A flow sheeting programme, SHPUMP, was developed for simulating different absorption heat cycles. The programme consists of ten different modules which allow the user to construct his own absorption cycle. The ten modules configurate evaporators, absorbers, generators, rectifiers, condensers, solution heat exchangers, pumps, valves, mixers and splitters. Seven basic and well established absorption cycles are available in the configuration data base of the programme. A new Carnot model is proposed heat cycles. Together with exergy analysis, general equations for the Carnot coefficient of performance and equations for thermodynamic efficiency, exergetic efficiency and exergy index, are derived, discussed and compared for both absorption heat pumps and absorption heat transformers. Utilizing SHPUMP, simulation results are presented for different configurations where absorption heat cycles are suggested to be incorporated in three different unit operations within both pulp and paper and oleochemical industries. One of the application studies reveled that an absorption heat transformer incorporated with an evaporation plant in a major pulp and paper industry, would save 18% of the total prime energy consumption in one of the evaporation plants. It was also concluded that installing an absorption heat pump in a paper drying plant would result in steam savings equivalent to 12 MW. An experimental absorption heat transformer unit operating with self-circulation has been modified and thoroughly tested. A reference heat transformer plant has been designed and installed in a major pulp and paper mill where it is directly incorporated with one of the evaporation plants. Preliminary plant operation data are presented. 72 refs, 63 figs, 33 tabs

  16. Theoretical Study of Amplitude Modulation Application during Radio Frequency Electrocoagulation

    Directory of Open Access Journals (Sweden)

    V. A. Karpuhin

    2015-01-01

    Full Text Available This article concerns the investigation results of influence of the amplitude-modulated acting signal parameters on the thermoelectric characteristics of biological tissues for a specified geometry of the working electrode section during RF mono-polar electrocoagulation. The geometric model ‘electrode - a biological tissue’ was suggested to study the distribution of power and temperature fields in biological tissue during mono-polar coagulation. The model of biological tissue is represented as a cylinder and the needle electrode is an ellipsoid immersed in the biological tissue. The heat and quasi-electrostatics equations are used as a mathematical model. These equations are solved in Comsol Multiphysics environment.As a result, we have got the following findings: the technique of calculating parameters of the PAM acting signal which has a fixed carrier frequency for the needle electrode of a specified geometry and the immersion depth in biological tissues is suggested. Parameters of PAM signal are determined for this electrode geometry. These parameters provide a 60 ... 80°C heating range of biological tissues near the working part of the tool for different amplitudes of acting signal during RF coagulation. It has been found out that both the temperature and the relaxation frequency of biological tissue depend on exposure time for the needle electrode of a specified geometry and immersion depth of the working part of tool into biological tissue.It is shown that the relaxation frequency of the biological tissue, subjected to the radiofrequency pulses, linearly depends on its heating temperature and can be used as a numerical criterion for maintaining the specified temperature conditions. It is found that the relaxation frequency of the biological tissue depends on the contact area of the tool working part and biological tissues. To reduce this dependence it is necessary to provide automatic current control of the output action.

  17. Theoretical studies in nuclear reactions and nuclear structure

    International Nuclear Information System (INIS)

    1992-05-01

    Research in the Maryland Nuclear Theory Group focusses on problems in four basic areas of current relevance. Hadrons in nuclear matter; the structure of hadrons; relativistic nuclear physics and heavy ion dynamics and related processes. The section on hadrons in nuclear matter groups together research items which are aimed at exploring ways in which the properties of nucleons and the mesons which play a role in the nuclear force are modified in the nuclear medium. A very interesting result has been the finding that QCD sum rules supply a new insight into the decrease of the nucleon's mass in the nuclear medium. The quark condensate, which characterizes spontaneous chiral symmetry breaking of the late QCD vacuum, decreases in nuclear matter and this is responsible for the decrease of the nucleon's mass. The section on the structure of hadrons contains progress reports on our research aimed at understanding the structure of the nucleon. Widely different approaches are being studied, e.g., lattice gauge calculations, QCD sum rules, quark-meson models with confinement and other hedgehog models. A major goal of this type of research is to develop appropriate links between nuclear physics and QCD. The section on relativistic nuclear physics represents our continuing interest in developing an appropriate relativistic framework for nuclear dynamics. A Lorentz-invariant description of the nuclear force suggests a similar decrease of the nucleon's mass in the nuclear medium as has been found from QCD sum rules. Work in progress extends previous successes in elastic scattering to inelastic scattering of protons by nuclei. The section on heavy ion dynamics and related processes reports on research into the e + e - problem and heavy ion dynamics

  18. Theoretical studies of structure and dynamics of chalcogenide glasses

    Science.gov (United States)

    Inam, Fakharul

    In this work, the structural and dynamical properties of Ge-Se and Ag-Ge-Se glasses, using first principle molecular dynamics simulations, is presented. Raman and calorimetric studies on GeXSe1- x glasses have provided evidence for the existence of the intermediate phase (IP) in chalcogenides and other glasses. Here we thoroughly discuss the ab-initio models of Ge XSe1-x glasses over a wide composition range and provide an atomistic picture of the IP. A thorough analysis of our models reveals that the IP in these glasses may arise from the competition between amorphous GeSe2 and a polymeric a-Se phases, which gives rise to the non-monotonic evolution (a topological feature of the IP) of the network parameters through the IP window. A qualitative comparison is made between the topological features extracted from the models and the experiments. A possible electronic signature of the IP in terms of the shift in the conduction edge energy in the IP range is predicted. The results agree with the shift in the white line position for the Se atoms in the K-edge X-Ray Absorption Near Edge Structure (XANES) spectra. A microscopic picture of the silver dynamics in GeSe3 :Ag glass is presented. The dynamics of Ag is explored at two temperatures: 300K and 700K. In the relaxed GeSe3 glass network, it is shown that the Ag occupies trapping centers (TC) that exist between pairs of suitably separated host sites. The charge state of the Ag in the glass network is computed and it is shown that Ag is neutral if weakly bonded and is Ag+ if in a trapping center. The dynamics of the Ag is shown to be largely effected by the neighboring host sties. At room temperature, Ag is mainly trapped at the TC with small hopping probability between neighboring TCs. At higher temperature (700 K), the Ag motion is diffusive and is proceeded via a trapping-release dynamics between supertraps or cages consisting of multiple trapping center sites in a small volume. Our work offers a first

  19. Experimental and Theoretical Study of Microturbine-Based BCHP System

    International Nuclear Information System (INIS)

    Fairchild, P.D.

    2001-01-01

    On-site and near-site distributed power generation (DG), as part of a Buildings Cooling, Heating and Power (BCHP) system, brings both electricity and waste heat from the DG sources closer to the end user's electric and thermal loads. Consequently, the waste heat can be used as input power for heat-activated air conditioners, chillers, and desiccant dehumidification systems; to generate steam for space heating; or to provide hot water for laundry, kitchen, cleaning services and/or rest rooms. By making use of what is normally waste heat, BCHP systems meet a building's electrical and thermal loads with a lower input of fossil fuel, yielding resource efficiencies of 40 to 70% or more. To ensure the success of BCHP systems, interactions of a DG system-such as a microturbine and thermal heat recovery units under steady-state modes of operation with various exhaust back pressures-must be considered. This article studies the performance and emissions of a 30-kW microturbine over a range of design and off-design conditions in steady-state operating mode with various back pressures. In parallel with the experimental part of the project, a BCHP mathematical model was developed describing basic thermodynamic and hydraulic processes in the system, heat and material balances, and the relationship of the balances. to the system configuration. The model can determine the efficiency of energy conversion both for an individual microturbine unit and for the entire BCHP system for various system configurations and external loads. Based on actual data Tom a 30-kW microturbine, linear analysis was used to obtain an analytical relationship between the changes in the thermodynamic and hydraulic parameters of the system. The actual data show that, when the backpressure at the microturbine exhaust outlet is increased to the maximum of 7 in. WC (0.017 atm), the microturbine's useful power output decreases by from 3.5% at a full power setting of 30 kW to 5.5% at a one-third power setting (10

  20. [Ni0]-catalyzed Co-oligomerization of 1,3-butadiene and ethylene: a theoretical mechanistic investigation of competing routes for generation of linear and cyclic C10-olefins.

    Science.gov (United States)

    Tobisch, Sven

    2004-01-14

    A detailed theoretical investigation of the mechanism for the [Ni(0)]-catalyzed co-oligomerization of 1,3-butadiene and ethylene to afford linear and cyclic C(10)-olefins is presented. Crucial elementary processes have been carefully explored for a tentative catalytic cycle, employing a gradient-corrected density functional theory (DFT) method. The favorable route for oxidative coupling starts from the prevalent [Ni(0)(eta(2)-butadiene)(2)(ethylene)] form of the active catalyst through oxidative coupling between the two eta(2)-butadienes. The initial eta(3),eta(1)(C(1))-octadienediyl-Ni(II) product is the active precursor for ethylene insertion, which preferably takes place into the syn-eta(3)-allyl-Ni(II) bond of the prevalent eta(3)-syn,eta(1)(C(1)),Delta-cis isomer. The insertion is driven by a strong thermodynamic force, giving rise entirely to eta(3),eta(1),Delta-trans-decatrienyl-Ni(II) forms, with the eta(3)-anti,eta(1),Delta-trans isomer almost exclusively generated. Occurrence of allyl,eta(1),Delta-cis isomers, however, is precluded on both kinetic and thermodynamic grounds, thereby rationalizing the observation that cis-DT and cis,cis-CDD are never formed. Linear and cyclic C(10)-olefins are generated in a highly stereoselective fashion, with trans-DT and cis,trans-CDD as the only isomers, along competing routes of stepwise transition-metal-assisted H-transfer (DT) and reductive CC elimination under ring closure (CDD), respectively, that start from the prevalent eta(3)-anti,eta(1),Delta-trans-decatrienyl-Ni(II) species. The role of allylic conversion in the octadienediyl-Ni(II) and decatrienyl-Ni(II) complexes has been analyzed. As a result of the detailed exploration of all important elementary steps, a theoretically verified, refined catalytic cycle is proposed and the regulation of the selectivity for formation of linear and cyclic C(10)-olefins is elucidated.

  1. Theoretical Study on the Flow of Refilling Stage in a Safety Injection Tank

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jun Sang [Halla Univ. Daejeon (Korea, Republic of)

    2017-10-15

    In this study, a theoretical analysis was performed to the flow of refilling stage in a safety injection tank, which is the core cooling system of nuclear power plant in an emergency. A theoretical model was proposed with a nonlinear governing equation defining on the flow of the refilling process of the coolant. Utilizing the Taylor-series expansion, the 1st - order approximation flow equation was obtained, along with its analytic solution of closed type, which could predict accurately the variations of free surface height and flow rate of the coolant. The availability of theoretical result was confirmed by comparing with previous experimental results.

  2. An in-depth analysis of theoretical frameworks for the study of care coordination

    Directory of Open Access Journals (Sweden)

    Sabine Van Houdt

    2013-06-01

    Full Text Available Introduction: Complex chronic conditions often require long-term care from various healthcare professionals. Thus, maintaining quality care requires care coordination. Concepts for the study of care coordination require clarification to develop, study and evaluate coordination strategies. In 2007, the Agency for Healthcare Research and Quality defined care coordination and proposed five theoretical frameworks for exploring care coordination. This study aimed to update current theoretical frameworks and clarify key concepts related to care coordination. Methods: We performed a literature review to update existing theoretical frameworks. An in-depth analysis of these theoretical frameworks was conducted to formulate key concepts related to care coordination.Results: Our literature review found seven previously unidentified theoretical frameworks for studying care coordination. The in-depth analysis identified fourteen key concepts that the theoretical frameworks addressed. These were ‘external factors’, ‘structure’, ‘tasks characteristics’, ‘cultural factors’, ‘knowledge and technology’, ‘need for coordination’, ‘administrative operational processes’, ‘exchange of information’, ‘goals’, ‘roles’, ‘quality of relationship’, ‘patient outcome’, ‘team outcome’, and ‘(interorganizational outcome’.Conclusion: These 14 interrelated key concepts provide a base to develop or choose a framework for studying care coordination. The relational coordination theory and the multi-level framework are interesting as these are the most comprehensive.

  3. [Nursing practice based on theoretical models: a qualitative study of nurses' perception].

    Science.gov (United States)

    Amaducci, Giovanna; Iemmi, Marina; Prandi, Marzia; Saffioti, Angelina; Carpanoni, Marika; Mecugni, Daniela

    2013-01-01

    Many faculty argue that theory and theorizing are closely related to the clinical practice, that the disciplinary knowledge grows, more relevantly, from the specific care context in which it takes place and, moreover, that knowledge does not proceed only by the application of general principles of the grand theories to specific cases. Every nurse, in fact, have  a mental model, of what may or may not be aware, that motivate and substantiate every action and choice of career. The study describes what the nursing theoretical model is; the mental model and the tacit  knowledge underlying it. It identifies the explicit theoretical model of the professional group that rapresents nursing partecipants, aspects of continuity with the theoretical model proposed by this degree course in Nursing.. Methods Four focus groups were made which were attended by a total of 22 nurses, rapresentatives of almost every Unit of Reggio Emilia Hospital's. We argue that the theoretical nursing model of each professional group is the result of tacit knowledge, which help to define the personal mental model, and the theoretical model, which explicitly underlying theoretical content learned applied consciously and reverted to / from nursing practice. Reasoning on the use of theory in practice has allowed us to give visibility to a theoretical model explicitly nursing authentically oriented to the needs of the person, in all its complexity in specific contexts.

  4. Kinetic and mechanistic studies of reactive intermediates in photochemical and transition metal-assisted oxidation, decarboxylation and alkyl transfer reactions

    Science.gov (United States)

    Carraher, Jack McCaslin

    Reactive species like high-valent metal-oxo complexes and carbon and oxygen centered radicals are important intermediates in enzymatic systems, atmospheric chemistry, and industrial processes. Understanding the pathways by which these intermediates form, their relative reactivity, and their fate after reactions is of the utmost importance. Herein are described the mechanistic detail for the generation of several reactive intermediates, synthesis of precursors, characterization of precursors, and methods to direct the chemistry to more desirable outcomes yielding 'greener' sources of commodity chemicals and fuels. High-valent Chromium from Hydroperoxido-Chromium(III). The decomposition of pentaaquahydroperoxido chromium(III) ion (hereafter Cr aqOOH2+) in acidic aqueous solutions is kinetically complex and generates mixtures of products (Craq3+, HCrO 4-, H2O2, and O2). The yield of high-valent chromium products (known carcinogens) increased from a few percent at pH 1 to 70 % at pH 5.5 (near biological pH). Yields of H 2O2 increased with acid concentration. The reproducibility of the kinetic data was poor, but became simplified in the presence of H2O2 or 2,2‧-azinobis(3-ethylbenzothiazoline-6-sulfonate) dianion (ABTS2-). Both are capable of scavenging strongly oxidizing intermediates). The observed rate constants (pH 1, [O2] ≤ 0.03 mM) in the presence of these scavengers are independent of [scavenger] and within the error are the same (k,ABTS2- = (4.9 +/- 0.2) x 10-4 s-1 and kH2O2 = (5.3 +/- 0.7) x 10-4 s-1); indicating involvement of the scavengers in post-rate determining steps. In the presence of either scavenger, decomposition of CrOOH2+ obeyed a two-term rate law, k obs / s-1 = (6.7 +/- 0.7) x 10-4 + (7.6 +/- 1.1) x 10-4 [H+]. Effect of [H+] on the kinetics and the product distribution, cleaner kinetics in the presence of scavengers, and independence of kobs on [scavenger] suggest a dual-pathway mechanism for the decay of Craq OOH2+. The H+-catalyzed path

  5. Toward a Theoretical Framework for Studying Climate Change Policies: Insights from the Case Study of Singapore

    Directory of Open Access Journals (Sweden)

    Ai Sian Ng

    2017-07-01

    Full Text Available The world decided in December 2015 to take actions to reduce global warming. To contribute toward this goal, this research examines possible policy levers for inclusion in the climate change ratification plan. A case study of the measures taken by the Republic of Singapore, a low-lying 719.2 km2 island without natural resources in Asia, is conducted. Being vulnerable to climate change impact and yet having to balance her people’s needs and economic progress with limited resources, the measures taken by this small country could offer policy insights for small states and states without access to alternative energy sources. This research analyzes the online policy documents posted by eleven organizations to answer the main research question of identifying policy levers as theoretical constructs to form a framework that can be used to study climate change policies. A qualitative data analysis software, QSR NVivo 10, is used to classify the proposed nodes developed by the researchers using a system perspective integrating the insights from the key international climate change frameworks with the theoretical concepts from the model of pro-environmental behavior. The findings can offer insights toward developing a new contextual influence framework, which can help strengthen policy development and outcome measurement.

  6. Recent STM, DFT and HAADF-STEM studies of sulfide-based hydrotreating catalysts: Insight into mechanistic, structural and particle size effects

    DEFF Research Database (Denmark)

    Besenbacher, Flemming; Brorson, M.; Clausen, B.S.

    2008-01-01

    The present article will highlight some recent experimental and theoretical studies of both unpromoted MoS2 and promoted Co-Mo-S and NiMo-S nanostructures. Particular emphasis will be given to discussion of our scanning tunnelling microscopy (STM), density functional theory (I)FT), and high-angle...

  7. AIEgens for dark through-bond energy transfer: design, synthesis, theoretical study and application in ratiometric Hg2+sensing.

    Science.gov (United States)

    Chen, Yuncong; Zhang, Weijie; Cai, Yuanjing; Kwok, Ryan T K; Hu, Yubing; Lam, Jacky W Y; Gu, Xinggui; He, Zikai; Zhao, Zheng; Zheng, Xiaoyan; Chen, Bin; Gui, Chen; Tang, Ben Zhong

    2017-03-01

    A novel dark through-bond energy transfer (DTBET) strategy is proposed and applied as the design strategy to develop ratiometric Hg 2+ sensors with high performance. Tetraphenylethene ( TPE ) derivatives with aggregation-induced emission (AIE) characteristics are selected as dark donors to eliminate emission leakage from the donors. The TBET mechanism has been adopted since it experiences less influence from spectral overlapping than Förster resonance energy transfer (FRET), making it more flexible for developing cassettes with large pseudo-Stokes shifts. In this work, energy transfer from the TPE derivatives (dark donor) to a rhodamine moiety (acceptor) was illustrated through photophysical spectroscopic studies and the energy transfer efficiency (ETE) was found to be up to 99%. In the solution state, no emission from the donors was observed and large pseudo-Stokes shifts were achieved (>280 nm), which are beneficial for biological imaging. Theoretical calculations were performed to gain a deeper mechanistic insight into the DTBET process and the structure-property relationship of the DTBET cassettes. Ratiometric Hg 2+ sensors were rationally constructed based on the DTBET mechanism by taking advantage of the intense emission of TPE aggregates. The Hg 2+ sensors exhibited well resolved emission peaks. >6000-fold ratiometric fluorescent enhancement is also achieved and the detection limit was found to be as low as 0.3 ppb. This newly proposed DTBET mechanism could be used to develop novel ratiometric sensors for various analytes and AIEgens with DTBET characteristics will have great potential in various areas including light harvesting materials, environmental science, chemical sensing, biological imaging and diagnostics.

  8. Theoretical studies of field-reversed configurations (FRC) and experimental study of the FRC during translation

    International Nuclear Information System (INIS)

    Siemon, R.E.; Armstrong, W.T.; Chrien, R.E.

    1985-01-01

    Theoretical studies of FRC stability and transport are summarized. Finite Larmor radius theories are shown to be unreliable for explaining the experimentally observed stability to tilting. Control of the n=2 rotational instability has been demonstrated in two-dimensional hybrid code simulations, and the stability appears to be described within MHD if the nearly square equilibria that result from quadrupole fields are taken into account. Simulations of the lower hybrid drift instability in parameter regimes relevant to experiments show good agreement with a non-local theory of the instability. A 1.5-dimensional transport code shows agreement with the energy confinement time but disagreement with the flux loss time observed in FRX-C. The process of FRC translation in which the plasma is formed, translated into a DC solenoid and trapped by magnetic mirrors, has been studied in the FRX-C/T experiment. Efficient transfer of particles, energy and internal magnetic flux are observed with no enhancement of loss processes over in-situ FRC experiments. The axial velocity of the FRC can be estimated reasonably well with a simple model based on conservation of energy. Internal magnetic field probing during translation shows the expected structure of poloidal field and a complex distribution of generally weak toroidal fields. Measurements of radiated power indicate that radiation is a small fraction of the total plasma power loss (typically 8%). Translation has facilitated scaling studies of confinement over a wider range of parameters than were achieved by in-situ FRX-C experiments. For example, the variable xsub(s), the ratio of the separatrix radius to the metal wall radius, has been increased to about 0.7 by allowing the FRC to expand during translation. In all cases, particle confinement times agree within a factor of two with predictions by models that assume a lower hybrid drift resistivity. However, for the conditions studied there are indications that the experimental

  9. Couples coping with cancer: exploration of theoretical frameworks from dyadic studies.

    Science.gov (United States)

    Regan, Tim W; Lambert, Sylvie D; Kelly, Brian; Falconier, Mariana; Kissane, David; Levesque, Janelle V

    2015-12-01

    A diagnosis of cancer and subsequent treatment are distressing not only for the person directly affected, but also for their intimate partner. The aim of this review is to (a) identify the main theoretical frameworks underpinning research addressing dyadic coping among couples affected by cancer, (b) summarise the evidence supporting the concepts described in these theoretical frameworks, and (c) examine the similarities and differences between these theoretical perspectives. A literature search was undertaken to identify descriptive studies published between 1990 and 2013 (English and French) that examined the interdependence of patients' and partners' coping, and the impact of coping on psychosocial outcomes. Data were extracted using a standardised form and reviewed by three of the authors. Twenty-three peer-reviewed manuscripts were identified, from which seven theoretical perspectives were derived: Relationship-Focused Coping, Transactional Model of Stress and Coping, Systemic-Transactional Model (STM) of dyadic coping, Collaborative Coping, Relationship Intimacy model, Communication models, and Coping Congruence. Although these theoretical perspectives emphasised different aspects of coping, a number of conceptual commonalities were noted. This review identified key theoretical frameworks of dyadic coping used in cancer. Evidence indicates that responses within the couple that inhibit open communication between partner and patient are likely to have an adverse impact on psychosocial outcomes. Models that incorporate the interdependence of emotional responses and coping behaviours within couples have an emerging evidence base in psycho-oncology and may have greatest validity and clinical utility in this setting. Copyright © 2015 John Wiley & Sons, Ltd.

  10. Study of the semi-theoretical relation of the hydraulic jump evolving ...

    African Journals Online (AJOL)

    This study has for objective to study the theoretical relation of the hydraulic jump by sill, evolving in an U-shaped channel, with a rough bed. Functional relations, in non-dimensional form, relating the jump characteristics, seeming the effect of the bed's roughness, are obtained. A comparative study with the hydraulic jump in ...

  11. Unraveling molecular mechanistic differences in liver metabolism between lean and fat lines of Pekin duck (Anas platyrhynchos domestica): a proteomic study.

    Science.gov (United States)

    Zheng, Aijuan; Chang, Wenhuan; Hou, Shuisheng; Zhang, Shu; Cai, Huiyi; Chen, Guilan; Lou, Ruiying; Liu, Guohua

    2014-02-26

    Duck is one of the major poultry meat sources for human consumption. To satisfy different eating habits, lean and fat strains of Pekin ducks have been developed. The objective of this study was to determine the molecular mechanistic differences in liver metabolism between two duck strains. The liver proteome of the Pekin duck lines was compared on days 1, 14, 28, and 42 posthatching using 2-DE based proteomics. There was a different abundance of 76 proteins in the livers of the two duck lines. Fat ducks strongly expressed proteins related to pathways of glycolysis, ATP synthesis, and protein catabolism, suggesting enhanced fat deposition rather than protein retention. In contrast, highly expressed proteins in lean ducks improved protein anabolism and reduced protein catabolism, resulting in an enhancement of lean meat deposition. Along with the decrease in fat deposition, the immune system of the lean duck strain may be enhanced by enhanced expression of proteins involved in stress response, immune defense, and antioxidant functions. These results indicate that selection pressure has shaped the two duck lines differently resulting in different liver metabolic capacities. These observed variations between the two strains at the molecular level are matched with physiological changes in growth performance and meat production. This information may have beneficial impacts in areas such as genetic modification through the manipulation of target proteins or genes in specific pathways to improve the efficiency of duck meat production. The objective of this study was to unravel molecular mechanistic differences in liver metabolism between lean and fat Pekin duck (Anas platyrhynchos domestica) strains. There was a different abundance of 76 proteins in the livers of the two duck lines. Enhanced protein expression in the fat ducks related to pathways of glycolysis, ATP synthesis and protein catabolism suggesting increased fat deposition rather than protein retention. In

  12. Mechanistic aspects of ionic reactions in flames

    DEFF Research Database (Denmark)

    Egsgaard, H.; Carlsen, L.

    1993-01-01

    Some fundamentals of the ion chemistry of flames are summarized. Mechanistic aspects of ionic reactions in flames have been studied using a VG PlasmaQuad, the ICP-system being substituted by a simple quartz burner. Simple hydrocarbon flames as well as sulfur-containing flames have been investigated...

  13. Epidemiological studies that ignore mechanism of disease causation are flawed and mechanistic evidence demonstrates that vaccines cause autism

    OpenAIRE

    Arumugham, Vinu

    2017-01-01

    Since vaccinologists are themselves ignorant of vaccine mechanisms, how can we expect epidemiologists to understand the mechanisms? So most epidemiological studies ignore mechanism of adverse event causation. If you ignore mechanism, you cannot design the study with appropriate controls. So the results of such epidemiological studies have to be discarded due to confounding. Proven mechanism involved in cow's milk contaminated vaccines causing folate receptor antibody related autism is des...

  14. Mechanistic studies on the lipid-raising coffee diterpenes cafestol and kahweol in monkeys, mice and man

    NARCIS (Netherlands)

    Roos, de B.

    2000-01-01

    Cafestol and kahweol are lipid-raising diterpenes present in unfiltered coffee. The objective of this thesis was to study their lipid-raising action in man. Unravelling this action might lead to new insights into the regulation of serum cholesterol levels.

    We first studied

  15. Advanced REACH Tool (ART) : Calibration of the mechanistic model

    NARCIS (Netherlands)

    Schinkel, J.; Warren, N.; Fransman, W.; Tongeren, M. van; McDonnell, P.; Voogd, E.; Cherrie, J.W.; Tischer, M.; Kromhout, H.; Tielemans, E.

    2011-01-01

    The mechanistic model of the Advanced Reach Tool (ART) provides a relative ranking of exposure levels from different scenarios. The objectives of the calibration described in this paper are threefold: to study whether the mechanistic model scores are accurately ranked in relation to exposure

  16. Mechanistic approach to stability studies as a tool for the optimization and development of new products based on L. rhamnosus Lcr35® in compliance with current regulations.

    Directory of Open Access Journals (Sweden)

    Claudia Muller

    Full Text Available Probiotics are of great current interest in the pharmaceutical industry because of their multiple effects on human health. To beneficially affect the host, an adequate dosage of the probiotic bacteria in the product must be guaranteed from the time of manufacturing to expiration date. Stability test guidelines as laid down by the ICH-Q1A stipulate a minimum testing period of 12 months. The challenge for producers is to reduce this time. In this paper, a mechanistic approach using the Arrhenius model is proposed to predict stability. Applied for the first time to laboratory and industrial probiotic powders, the model was able to provide a reliable mathematical representation of the effects of temperature on bacterial death (R(2>0.9. The destruction rate (k was determined according to the manufacturing process, strain and storage conditions. The marketed product demonstrated a better stability (k = 0.08 months(-1 than the laboratory sample (k = 0.80 months(-1. With industrial batches, k obtained at 6 months of studies was comparable to that obtained at 12 months, evidence of the model's robustness. In addition, predicted values at 12 months were greatly similar (±30% to those obtained by real-time assessing the model's reliability. This method could be an interesting approach to predict the probiotic stability and could reduce to 6 months the length of stability studies as against 12 (ICH guideline or 24 months (expiration date.

  17. CF3CH(ONO)CF3: Synthesis, IR spectrum, and use as OH radical source for kinetic and mechanistic studies

    DEFF Research Database (Denmark)

    Andersen, Mads Peter Sulbæk; Hurley, MD; Ball, JC

    2003-01-01

    The synthesis, IR spectrum, and first-principles characterization of CF3CH(ONO)CF3 as well as its use as an OH radical source in kinetic and mechanistic studies are reported. CF3CH(ONO)CF3 exists in two conformers corresponding to rotation about the RCO-NO bond. The more prevalent trans conformer...... accounts for the prominent IR absorption features at frequencies (cm(-1)) of 1766 (N=O stretch), 1302, 12 10, and 1119 (C-F stretches), and 761 (O-N-O bend); the cis conformer contributes a number of distinct weaker features. CF3CH(ONO)CF3 was readily photolyzed using fluorescent blacklamps to generate CF3......C(O)CF3 and, by implication, OH radicals in 100% yield. CF3CH(ONO)CF3 photolysis is a convenient source of OH radicals in the studies of the yields of CO, CO2, HCHO, and HC(O)OH products which can be difficult to measure using more conventional OH radical sources (e.g., CH3ONO photolysis). CF3CH...

  18. A theoretical study of pump–probe experiment in single-layer ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 82; Issue 6. A theoretical study of pump–probe experiment in single-layer, bilayer and multilayer graphene ... Here we use it as a tool to study the phenomenon of anomalous Rabi oscillations in graphene that was predicted recently in single-layer graphene.

  19. Curriculum, Curriculum Development, Curriculum Studies? Problematising Theoretical Ambiguities in Doctoral Theses in the Education Field

    Science.gov (United States)

    du Preez, Petro; Simmonds, Shan

    2014-01-01

    Theoretical ambiguities in curriculum studies result in conceptual mayhem. Accordingly, they hinder the development of the complicated conversation on curriculum as a verb. This article aims to contribute to reconceptualizing curriculum studies as a dynamic social practice that aspires to thinking and acting with intelligences and sensitivity so…

  20. THEORETICAL AND METHODOLOGICAL APPROACHES TO THE STUDY OF PROTEST ACTIVITY IN THE WESTERN SOCIOLOGICAL THOUGHT

    OpenAIRE

    Купрєєва, Ю. О.

    2015-01-01

    In this article the author discusses the main theoretical and methodological approaches to the study of protest activity. Among them - the theory of collective behavior, the relative deprivation theory, the new social movements theory and the resource mobilization theory. Highlighted their strengths and weaknesses. Focused on the new direction of protest studies connected with the development of the Internet.

  1. Theoretical/Computational Studies of High-Temperature Superconductivity from Quantum Magnetism

    Science.gov (United States)

    2016-06-09

    AFRL-AFOSR-VA-TR-2016-0204 Theoretical/Computational Studies of High-Temperature Superconductivity from Quantum Magnetism Jose Rodriguez CALIFORNIA...TITLE AND SUBTITLE Theoretical/Computational Studies of High-Temperature Superconductivity from Quantum Magnetism 5a.  CONTRACT NUMBER 5b.  GRANT...SUBJECT TERMS quantum magnetism , HTS, superconductivity 16.  SECURITY CLASSIFICATION OF: 17.  LIMITATION OF       ABSTRACT UU 18.  NUMBER        OF

  2. Theoretical and experimental study of modes associated to ion cyclotron heating on TFR

    International Nuclear Information System (INIS)

    Pignol, L.

    1985-05-01

    In this work, the ion cyclotron wave evolution is followed thanks to a coherent scattering device using carbon dioxide laser radiation. A theoretical part presents the dispersion equation that obey the waves excited in the plasma by antenna emitting ion cyclotron frequency. Then measurements given by the diagnostic are given. Fast and slow waves evidenced theoretically, are experimentally observed. Two simple theoretical models allow to extract physical quantities characteristics of the two modes. These two modes are followed along the radial coordinate of the tore and their behavior through the hybrid curve is studied. measured spectra shape is shown to confirm the described numerical code validity. Time study of the slow wave shows of internal relaxation phenomenon of plasma [fr

  3. Theoretical and experimental studies on critical heat flux in subcooled boiling and vertical flow geometry

    International Nuclear Information System (INIS)

    Staron, E.

    1996-01-01

    Critical Heat Flux is a very important subject of interest due to design, operation and safety analysis of nuclear power plants. Every new design of the core must be thoroughly checked. Experimental studies have been performed using freon as a working fluid. The possibility of transferring of results into water equivalents has been proved. The experimental study covers vertical flow, annular geometry over a wide range of pressure, mass flow and temperature at inlet of test section. Theoretical models of Critical Heat Flux have been presented but only those which cover DNB. Computer programs allowing for numerical calculations using theoretical models have been developed. A validation of the theoretical models has been performed in accordance with experimental results. (author). 83 refs, 32 figs, 4 tabs

  4. EFFICIENCY OF ISO 9001 IN PORTUGAL: A QUALITATIVE STUDY FROM A HOLISTIC THEORETICAL PERSPECTIVE

    Directory of Open Access Journals (Sweden)

    Alcina Dias

    2013-03-01

    Full Text Available The purpose of this paper is to analy se the efficiency of ISO 9001 from a holistic theoretical approach where the Contingency theory, the Institutional theory and the Resources-Based View are integrated. The study was carried out in companies of different sectors of activity in Portugal, based on a qualitative methodology (interviews. The fact of the interviews having been undertaken under an ISO 9001 structure made it easier for companies to grasp the issues under investigation. An ISO 9001 characterisation was carried out on a theoretical framework approach and findings point out efficiency gains and revealed that the absence of ISO 9001 would work as a competitive disadvantage. The contribution of this research aims to reinforce the state of art as concerns the theoretical scope of analysis of these issues enriched by the case study achievement.

  5. Ni adsorption and Ni-Al LDH precipitation in a sandy aquifer: An experimental and mechanistic modeling study

    NARCIS (Netherlands)

    Regelink, I.C.; Temminghoff, E.J.M.

    2011-01-01

    Mining activities and industries have created nickel (Ni) contaminations in many parts of the world. The objective of this study is to increase our understanding of Ni adsorption and Nickel-Aluminium Layered Double Hydroxide (Ni-Al LDH) precipitation to reduce Ni mobility in a sandy soil aquifer. At

  6. MECHANISTIC STUDIES OF SURFACE CATALYZED H2O2 DECOMPOSITION AND CONTAMINANT DEGRADATION IN THE PRESENCE OF SAND. (R823402)

    Science.gov (United States)

    This study examined the mechanism and kinetics of surface catalyzed hydrogen peroxide decomposition and degradation of contaminants in the presence of sand collected from an aquifer and a riverbed. Batch experiments were conducted using variable sand concentrations (0.2 to 1.0&nb...

  7. Intermanual Transfer in Training With an Upper-Limb Myoelectric Prosthesis Simulator : A Mechanistic, Randomized, Pretest-Posttest Study

    NARCIS (Netherlands)

    Romkema, Sietske; Bongers, Raoul M.; van der Sluis, Corry K.

    Background. Intermanual transfer may improve prosthetic handling and acceptance if used in training soon after an amputation. Objective. The purpose of this study was to determine whether intermanual transfer effects can be detected after training with a myoelectric upper-limb prosthesis simulator.

  8. Intermanual Transfer Effect in Young Children After Training in a Complex Skill : Mechanistic, Pseudorandomized, Pretest-Posttest Study

    NARCIS (Netherlands)

    Romkema, Sietske; Bongers, Raoul M.; van der Sluis, Corry K.

    Background. Intermanual transfer implies that motor skills learned on one side of the body transfer to the untrained side. This effect was previously noted in adults practicing with a prosthesis simulator. Objective. The study objective was to determine whether intermanual transfer is present in

  9. Adhesion of nano-sized particles to the surface of bacteria: mechanistic study with the extended DLVO theory.

    Science.gov (United States)

    Hwang, Geelsu; Ahn, Ik-Sung; Mhin, Byung Jin; Kim, Ju-Young

    2012-09-01

    Due to the increasing production and application of nanoparticles, their release into the environment would be inevitable, which requires a better understanding of their fate in the environment. When considering their toxic behavior or biodegradation as their fate, their adhesion to the cell surface must be the first step to be thoroughly studied. In this study, nano-sized polymeric particles of urethane acrylate with various hydrophobicity and ionic properties were synthesized as model nanoparticles, and their adhesion to Pseudomonas putida strains was monitored. The higher hydrophobicity and positive charge density on the particle surface exhibited the larger adhesion to the bacteria, whereas negative charge density on the particle hindered their adhesion to the bacteria, albeit high hydrophobicity of particle. These observations were successfully explained with the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Achieving Reversible H2/H+ Interconversion at Room Temperature with Enzyme-Inspired Molecular Complexes: A Mechanistic Study

    Energy Technology Data Exchange (ETDEWEB)

    Priyadarshani, Nilusha; Dutta, Arnab; Ginovska-Pangovska, Bojana; Buchko, Garry W.; O' Hagan, Molly J.; Raugei, Simone; Shaw, Wendy J.

    2016-09-02

    Inspired by the contribution of the protein scaffold to the efficiency with which enzymes function, we report the first molecular complex that is reversible for electrocatalytic H2 production/oxidation at room temperature in methanol. [Ni(PCy2NPhe2)2]2+ (CyPhe; PR2NR’2 = 1,5-diaza-3,7-diphosphacyclooctane, Cy=cyclohexyl, Phe=phenylalanine), shows reversible behavior in acidic methanol with peripheral phenylalanine groups providing key contributions to the catalytic behavior. The importance of the aromatic rings is implicated in achieving reversibility, based on the lack of reversibility of similar complexes, [Ni(PCy2NAmino Acid2)2]2+, containing arginine (CyArg) or glycine (CyGly). A complex with an added OH group on the ring, (CyTyr; Tyr=Tyrosine), also shows similar behavior. NMR studies reveal a significantly slower rate of chair-boat isomerization for the CyPhe relative to other derivatives, suggesting that the aromatic groups provide structural control by interacting with each other, an observation supported by molecular dynamics studies. NMR studies also show extremely fast proton movement, with a proton pathway from the Ni-H through the pendant amine to the –COOH group. Further, studies of acomplex without the –COOH group, [Ni(PCy2NTym2)2]2+ (CyTym; Tym=Tyramine), are not reversible and have slow proton movement from the pendant amine, demonstrating the essential nature of the –COOH group in achieving reversibility. Finally, methanol is demonstrated to play a critical contributing role. The influence of multiple factors on reversibility for this synthetic catalyst is a demonstration of the intricate interplay between the first, second, and outer coordination spheres and resembles the complexity observed in metalloenzymes.

  11. Mechanistic and conformational studies on the interaction of anti-inflammatory drugs, isoxicam and tenoxicam with bovine serum albumin

    Energy Technology Data Exchange (ETDEWEB)

    Punith, Reeta; Katrahalli, Umesha; Kalanur, Shankara S. [Department of Chemistry, Karnatak University, Dharwad 580 003 (India); Jaldappagari, Seetharamappa, E-mail: jseetharam@yahoo.co [Department of Chemistry, Karnatak University, Dharwad 580 003 (India)

    2010-11-15

    The mechanism of interaction of the non-steroidal anti-inflammatory drugs, isoxicam (IXM) and tenoxicam (TXM) with bovine serum albumin (BSA) has been studied using spectroscopic techniques, viz., spectrofluorescence, circular dichroism (CD), UV-visible absorption and FT-IR under simulative physiological conditions. Stern-Volmer analysis of fluorescence quenching data shows the presence of the static quenching mechanism. Thermodynamic parameters (negative {Delta}H{sup 0} and positive {Delta}S{sup 0} values obtained in the present study) revealed that the hydrophobic interactions played a major role in the interaction of these drugs with BSA. The distance, r between the donor (BSA) and acceptor (IXM/TXM) was calculated based on the Forster's theory of non-radiation energy transfer and the values were observed to be 3.85 nm and 2.60 nm in IXM-BSA and TXM-BSA system, respectively. CD and FT-IR studies indicated that the binding of IXM/TXM to BSA induced conformational changes in BSA. The effect of common ions on the binding of IXM/TXM to BSA has been investigated.

  12. Chelated Nitrogen-Sulphur-Codoped TiO2: Synthesis, Characterization, Mechanistic, and UV/Visible Photocatalytic Studies

    Directory of Open Access Journals (Sweden)

    Hayat Khan

    2017-01-01

    Full Text Available This study presents in detail the physicochemical, photoluminescent, and photocatalytic properties of carboxylic acid chelated nitrogen-sulphur-codoped TiO2. From the Fourier transform infrared spectroscopic study, it was revealed that the formate group formed bidentate bridging linkage while the acetate group coordinated in a bidentate chelating mode with a titanium precursor. In compliance with X-ray diffraction data, the anatase to rutile transformation temperature was extended due to carboxylic acid chelation and NS codoping. Raman analysis indicated four Raman peaks at 146, 392, 512, and 632 cm−1 for the precalcined chelated TiO2; on incorporation with NS dopants, an increase in Raman intensity for these peaks was recorded, indicating the structure stability of the anatase phase. Furthermore, X-ray photoelectron spectroscopic study revealed the presence of anionic doping of nitrogen and cationic doping of sulphur in the lattice of TiO2. When evaluating the UV-visible photodegradation rate of 4-chlorophenol, the modified TiO2 (NS0.06-TFA showed the highest photocatalytic activity. In connection with the activity tests, several scavenger agents were employed to elucidate the significance of the different reactive oxidizing species during the photocatalytic process. Moreover, the transfer pathways of photogenerated carriers and the photocatalytic reaction mechanism of modified TiO2 were also explained in detail.

  13. A SAR-based mechanistic study on the combined toxicities of sulfonamides and quorum sensing inhibitors on Escherichia coli.

    Science.gov (United States)

    Chen, C; Wang, D; Wang, H; Lin, Z; Fang, Z

    2017-07-01

    Quorum sensing inhibitors (QSIs) are promising alternatives to antibiotics, but they are discharged into the environment after their use cycle. This poses joint effects on the organisms in the environment. Therefore, it is of great importance to study the combined toxicities of QSIs and antibiotics. In this study, we investigated the single and combined toxicities of four potential QSIs and 11 sulfonamides (SAs) on Escherichia coli. The results revealed that the single toxicities of SAs were greater than those of QSIs, and the toxicities were found positively related to the binding energies (E bind ) with their target proteins, for both antibiotics and QSIs. The combined toxicities of the binary mixtures were observed to be either antagonism or addition. The antagonism could be explained by the phenomenon that QSIs changed SAs molecules into ionic forms, preventing the SA molecules entering the bacteria. Furthermore, it was found that the ratios of the effective concentration (the actual concentration involved in the interaction with the proteins) in the antagonistic cases were higher than those in the additive cases. This study would benefit both rational use of the drug combination and ecological risk assessment of antibiotics and QSIs in the real environment.

  14. Absorption enhancement, mechanistic and toxicity studies of medium chain fatty acids, cyclodextrins and bile salts as peroral absorption enhancers.

    Science.gov (United States)

    Sharma, Pradeep; Varma, Manthena V S; Chawla, Harmander P S; Panchagnula, Ramesh

    2005-01-01

    The objective of the present investigation was to evaluate an oral 'drug delivery' approach, which involves co-administration of absorption enhancers (AEs). The representative low permeable hydrophilic (biopharmaceutic classification system (BCS) Class III) drugs used in the study comprised of cefotaxime sodium and ceftazidime pentahydrate, whereas low permeable lipophilic (BCS Class IV) drugs include cyclosporin A and lovastatin. AEs from three different chemical classes, namely, medium chain fatty acids (sodium caprylate and caprate), cyclodextrins (beta-cyclodextrin, hydroxypropyl beta-cyclodextrin) and bile salts (sodium cholate and deoxycholate) were evaluated for absorption enhancement efficacy, mechanism of action and toxicity using in vitro everted intestinal sac model. These AEs were found to enhance intestinal permeability of drugs from 2- to 27-fold. Light microscopy studies of intestinal sac incubated with AEs for 120 min revealed morphological changes in absorptive mucosa and rank order of toxicity were cyclodextrins>bile salts congruent with medium chain fatty acids. Fluorescence polarization studies indicated that brush bordered membrane vesicles labeled with lipophilic (DPH, 12AS) and hydrophilic dyes (ANS), when treated with AEs exhibited concentration and time dependent decrease in fluorescence polarization. Total protein released in presence of AEs was more than control but considerably less than EDTA (0.58% w/v), which is known to cause toxic release of proteins from cell. Overall, AEs were found to significantly enhance drug permeability by decreasing lipid membrane fluidity and/or interacting with hydrophilic domains of membrane, and has the potential to improve oral delivery.

  15. Kinetics and mechanistic study of n-alkane hydroisomerization reaction on Pt-doped γ-alumina catalyst

    Directory of Open Access Journals (Sweden)

    Abhishek Dhar

    2017-12-01

    Full Text Available The catalysts γ-alumina (GA, the reference catalyst and Pt doped γ-alumina (PGA-s were synthesized using a simple sol-gel technique, in which at first preparation of porous base (GA, then impregnation of platinum salt over the base and finally reduction of platinum in the surface of the support were done. These catalysts prepared in different mole ratios of Pt:Al as 2:1, 1:1 and 1:2 are named as PGA-1, PGA-2 and PGA-3 respectively. The isomerization of n-alkanes (n-hexane, n-heptane and n-octane were investigated over the synthesized catalysts. The 2-methyl pentane (2-MP, 2,2-dimethyl pentane (2,2-DMP and 2,3-dimethyl hexane (2,3-DMH are the major products of respective isomerization of n-hexane, n-heptane and n-octane, besides a small amount of other branched isomers are also produced. The product distribution is comparable to that reported for Pt based other catalysts. The optimal mole ratios of Pt:Al is 1:1 (PGA-2 gives quite good catalytic activity for isomerization of n-alkane. Even through in reusability study, PGA-2 gives better performance than others. We have mainly focused on kinetic study, reaction mechanism behind isomerization and calculated the order of reactions and activation energies of the isomerization reactions in the present work. Keywords: Isomerization, n-alkanes, Catalyst, Reaction mechanism, Kinetics study, Activation energy

  16. A mechanistic study and computational prediction of iron, cobalt and manganese cyclopentadienone complexes for hydrogenation of carbon dioxide.

    Science.gov (United States)

    Ge, Hongyu; Chen, Xiangyang; Yang, Xinzheng

    2016-10-13

    A series of cobalt and manganese cyclopentadienone complexes are proposed and examined computationally as promising catalysts for hydrogenation of CO 2 to formic acid with total free energies as low as 20.0 kcal mol -1 in aqueous solution. Density functional theory study of the newly designed cobalt and manganese complexes and experimentally reported iron cyclopentadienone complexes reveals a stepwise hydride transfer mechanism with a water or a methanol molecule assisted proton transfer for the cleavage of H 2 as the rate-determining step.

  17. Mechanistic and single-dose in vivo therapeutic studies of Cry5B anthelmintic action against hookworms.

    Directory of Open Access Journals (Sweden)

    Yan Hu

    Full Text Available Hookworm infections are one of the most important parasitic infections of humans worldwide, considered by some second only to malaria in associated disease burden. Single-dose mass drug administration for soil-transmitted helminths, including hookworms, relies primarily on albendazole, which has variable efficacy. New and better hookworm therapies are urgently needed. Bacillus thuringiensis crystal protein Cry5B has potential as a novel anthelmintic and has been extensively studied in the roundworm Caenorhabditis elegans. Here, we ask whether single-dose Cry5B can provide therapy against a hookworm infection and whether C. elegans mechanism-of-action studies are relevant to hookworms.To test whether the C. elegans invertebrate-specific glycolipid receptor for Cry5B is relevant in hookworms, we fed Ancylostoma ceylanicum hookworm adults Cry5B with and without galactose, an inhibitor of Cry5B-C. elegans glycolipid interactions. As with C. elegans, galactose inhibits Cry5B toxicity in A. ceylanicum. Furthermore, p38 mitogen-activated protein kinase (MAPK, which controls one of the most important Cry5B signal transduction responses in C. elegans, is functionally operational in hookworms. A. ceylanicum hookworms treated with Cry5B up-regulate p38 MAPK and knock down of p38 MAPK activity in hookworms results in hypersensitivity of A. ceylanicum adults to Cry5B attack. Single-dose Cry5B is able to reduce by >90% A. ceylanicum hookworm burdens from infected hamsters, in the process eliminating hookworm egg shedding in feces and protecting infected hamsters from blood loss. Anthelmintic activity is increased about 3-fold, eliminating >97% of the parasites with a single 3 mg dose (∼30 mg/kg, by incorporating a simple formulation to help prevent digestion in the acidic stomach of the host mammal.These studies advance the development of Cry5B protein as a potent, safe single-dose anthelmintic for hookworm therapy and make available the information of how

  18. N-Heterocycle-Forming Amino/Carboperfluoroalkylations of Aminoalkenes by Using Perfluoro Acid Anhydrides: Mechanistic Studies and Applications Directed Toward Perfluoroalkylated Compound Libraries.

    Science.gov (United States)

    Kawamura, Shintaro; Dosei, Kento; Valverde, Elena; Ushida, Kiminori; Sodeoka, Mikiko

    2017-12-01

    This work describes a practical and efficient method for synthesizing a diverse array of perfluoroalkylated amines, including N-heterocycles, to afford perfluoroalkylated chemical libraries as potential sources of drug candidates, agrochemicals, and probe molecules for chemical-biology research. Perfluoro acid anhydrides, which are commonly used in organic synthesis, were employed as a perfluoroalkyl source for intramolecular amino- and carbo-perfluoroalkylations of aminoalkenes, affording perfluoroalkylated N-heterocycles, including: aziridines, pyrrolidines, benzothiazinane dioxides, indolines, and hydroisoquinolinones. Diacyl peroxides were generated in situ from the perfluoro acid anhydrides with urea·H 2 O 2 , and allowed to react with aminoalkenes in the presence of copper catalyst to control the product selectivity between amino- and carbo-perfluoroalkylations. To illustrate the synthetic utility of bench-stable trifluoromethylated aziridine, which was prepared on a gram scale, we used it to synthesize a wide variety of trifluoromethylated amines including complex molecules, such as trifluoromethylated tetrahydroharmine and spiroindolone. A mechanistic study of the role of the copper catalyst in the aminotrifluoromethylation of allylamine suggested that Cu(I) accelerates CF 3 radical formation via decomposition of diacyl peroxide, which appears to be the turnover-limiting step, while Cu(II) controls the product selectivity.

  19. Silver vanadium oxide and silver vanadium phosphorous oxide dissolution kinetics: a mechanistic study with possible impact on future ICD battery lifetimes.

    Science.gov (United States)

    Bock, David C; Takeuchi, Kenneth J; Marschilok, Amy C; Takeuchi, Esther S

    2013-10-14

    Material design strategies for energy storage applications can be considered in two major categories: (1) control of structure and composition and (2) material dimensional control such as the implementation of nanomaterials. Characterization of electrochemical properties determines energy content and possible viability for potential application. Equally critical yet more challenging is quantifying the non-Faradaic parasitic reactions of the active materials and the relationship to battery life. Understanding the significant factors associated with battery lifetimes for the implantable cardioverter defibrillator (ICD) is critical for the development of new ICD batteries. In situ dissolution of the cathode material has been identified as a major factor in premature end of life for ICD batteries. This study contains the kinetic analyses of silver and vanadium dissolution from the benchmark silver vanadium oxide (SVO) material and two silver vanadium phosphorous oxide (SVPO-H and SVPO-R) materials with differing physical properties in a non-aqueous ICD battery electrolyte. A comparison of the kinetic and mechanistic results for SVO, SVPO-H and SVPO-R provides insight for future material design approaches.

  20. Kinetic and Mechanistic Study of the pH-Dependent Activation (Epoxidation) of Prodrug Treosulfan Including the Reaction Inhibition in a Borate Buffer.

    Science.gov (United States)

    Romański, Michał; Ratajczak, Whitney; Główka, Franciszek

    2017-07-01

    A prodrug treosulfan (T) undergoes a pH-dependent activation to epoxide derivatives. The process seems to involve an intramolecular Williamson reaction (IWR) but clear kinetic evidence is lacking. Moreover, a cis-diol system present in the T structure is expected to promote complexation with boric acid. As a result, the prodrug epoxidation would be inhibited; however, this phenomenon has not been investigated. In this article, the effect of pH on the kinetics of T conversion to its monoepoxide was studied from a mechanistic point of view. Also, the influence of boric acid on the reaction kinetics was examined. The rate constants observed for the activation of T (k obs ) in acetate, phosphate, and carbonate buffers satisfied the equation logk obs  = -7.48 + 0.96 pH. The reaction was inhibited in the excess of boric acid over T, and the k obs decreased with increasing borate buffer concentration. The experimental results were consistent with the inhibition model that included the formation of a tetrahedral, anionic T-boric acid monoester. To conclude, in nonborate buffers, the T activation to (2S,3S)-1,2-epoxybutane-3,4-diol 4-methanesulfonate follows IWR mechanism. A borate buffer changes the reaction kinetics and complicates kinetic analysis. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  1. Mechanistic Study on the Solution-Phase n-Doping of 1,3-Dimethyl-2-aryl-2,3-dihydro-1H-benzoimidazole Derivatives

    Science.gov (United States)

    Naab, Benjamin D.; Guo, Song; Olthof, Selina; Evans, Eric G. B.; Wei, Peng; Millhauser, Glenn L.; Kahn, Antoine; Barlow, Stephen; Marder, Seth R.; Bao, Zhenan

    2014-01-01

    The discovery of air-stable n-dopants for organic semiconductor materials has been hindered by the necessity of high-energy HOMOs and the air sensitivity of compounds that satisfy this requirement. One strategy for circumventing this problem is to utilize stable precursor molecules that form the active doping complex in situ during the doping process or in a postdeposition thermal- or photo-activation step. Some of us have reported on the use of 1H-benzimidazole (DMBI) and benzimidazolium (DMBI-I) salts as solution- and vacuum-processable n-type dopant precursors, respectively. It was initially suggested that DMBI dopants function as single-electron radical donors wherein the active doping species, the imidazoline radical, is generated in a postdeposition thermal annealing step. Herein we report the results of extensive mechanistic studies on DMBI-doped fullerenes, the results of which suggest a more complicated doping mechanism is operative. Specifically, a reaction between the dopant and host that begins with either hydride or hydrogen atom transfer and which ultimately leads to the formation of host radical anions is responsible for the doping effect. The results of this research will be useful for identifying applications of current organic n-doping technology and will drive the design of next-generation n-type dopants that are air stable and capable of doping low-electron-affinity host materials in organic devices. PMID:24011269

  2. Studies of extractant molecules in solution and at liquid-liquid interfaces: structural and mechanistic aspects of synergy effects

    International Nuclear Information System (INIS)

    Baaden, Marc

    2000-01-01

    Molecular dynamics simulations reported herein provide new important insights into cation recognition and complexation in solution as well as liquid-liquid extraction, with a particular focus on the microscopic events taking place at the interface between two immiscible liquids. Preliminary studies concerned the representation of the trivalent rare earth cations La 3+ , Eu 3+ and Yb 3+ in force field simulations, probing structural and energetic features on an experimentally characterized model system based on substituted pyridine dicarboxamide ligands. Complexation of such cations by a novel calixarene derivative was investigated showing unexpected features, such as the position of the cation in the complex. Independent experimental studies published subsequently support these findings. Another part of the work is related to industrial liquid-liquid extraction systems using tri-n-butyl phosphate (TBP) as co-solvent, extractant, surfactant and synergist. We investigate 1) concentration effects simulating up to 60 TBP at a water/chloroform interface, 2) acidity using a neutral and ionic model of HNO 3 and 3) synergistic aspects of mixed TBP/calixarene extraction systems. These simulations provide the first microscopic insights into such issues. We finally addressed the topic of solute transfer across the water/chloroform interface. The potential of mean force for such a process has been calculated by both standard methods and novel approaches [fr

  3. Mechanistic Study of Electrolyte Additives to Stabilize High-Voltage Cathode-Electrolyte Interface in Lithium-Ion Batteries.

    Science.gov (United States)

    Gao, Han; Maglia, Filippo; Lamp, Peter; Amine, Khalil; Chen, Zonghai

    2017-12-27

    Current developments of electrolyte additives to stabilize electrode-electrolyte interface in lithium-ion batteries highly rely on a trial-and-error search, which involves repetitive testing and intensive amount of resources. The lack of understandings on the fundamental protection mechanisms of the additives significantly increases the difficulty for the transformational development of new additives. In this study, we investigated two types of individual protection routes to build a robust cathode-electrolyte interphase at high potentials: (i) a direct reduction in the catalytic decomposition of the electrolyte solvent; and (ii) formation of a "corrosion inhibitor film" that prevents severely attack and passivation from protons that generated from the solvent oxidation, even the decomposition of solvent cannot be mitigated. Effect of two exemplary electrolyte additives, lithium difluoro(oxalato)borate (LiDFOB) and 3-hexylthiophene (3HT), on LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC 622) cathode were investigated to validate our hypothesis. It is demonstrated that understandings of both electrolyte additives and solvent are essential and careful balance between the cathode protection mechanism of additives and their side effects is critical to obtain optimum results. More importantly, this study opens up new directions of rational design of functional electrolyte additives for the next-generation high-energy-density lithium-ion chemistries.

  4. Kinetic and Mechanistic Studies of Oxidation of an Antiallergic Drug with Bromamine-T in Acid and Alkaline Media

    International Nuclear Information System (INIS)

    Puttaswamy; Anu Sukhdev

    2012-01-01

    Cetrizine dihydrochloride (CTZH) is widely used as an anti-allergic drug. Sodium N-bromo-p-toluenesulfonamide or bromamine-T (BAT) is the bromine analogue of chloramine-T (CAT) and is found to be a better oxidizing agent than CAT. In the present research, the kinetics of oxidation of CTZH with BAT in acid and alkaline media was studied at 313 K. The experimental rate laws obtained are: -d[BAT]/dt = k[BAT] [CTZH] 0.80 [H + ] -0.48 in acid medium and -d[BAT]/dt = k[BAT][CTZH] 0.48 [OH - ] 0.52 [PTS] -0.40 in alkaline medium where PTS is p-toluenesulfonamide. Activation parameters and reaction constants were evaluated. The solvent isotope effect was studied using D 2 O. The dielectric effect is positive. The stoichiometry of the reaction was found to be 1:1 and the oxidation products were identified as 4-chlorobenzophenone and (2-piperazin-1-yl-ethoxy)-acetic acid in both media. The rate of oxidation of CTZH is faster in acid medium. Suitable mechanisms and related rate laws have been worked out

  5. Isotopic effects in mechanistic studies of biotransformations of fluorine derivatives of L-alanine catalysed by L-alanine dehydrogenase

    International Nuclear Information System (INIS)

    Szymańska-Majchrzak, Jolanta; Pałka, Katarzyna; Kańska, Marianna

    2017-01-01

    Synthesis of 3-fluoro-[2- 2 H]-L-alanine (3-F-[ 2 H]-L-Ala) in reductive amination of 3-fluoropyruvic acid catalysed by L-alanine dehydrogenase (AlaDH) was described. Fluorine derivative was used to study oxidative deamination catalysed by AlaDH applied kinetic (for 3-F-L-Ala in H 2 O - KIE’s on V max : 1.1; on V max /K M : 1.2; for 3-F-L-Ala in 2 H 2 O – on V max : 1.4; on V max /K M : 2.1) and solvent isotope effect methods (for 3-F-L-Ala - SIE’s on V max : 1.0; on V max /K M : 0.87; for 3-F-[2- 2 H]-L-Ala – on V max : 1.4; on V max /K M : 1.5). Studies explain some details of reaction mechanism. - Highlights: • Synthesis of 3-fluoro-[2- 2 H]-L-alanine was performed. • The reactions were catalysed using the enzyme L-alanine dehydrogenase. • Performed reactions involved fluorinated analogues of L-alanine. • Solvent isotope effects of deuterium were determined. • Kinetic isotope effects were determined for obtained 3-fluoro-L-alanine. • The mechanism of reaction catalysed by L-alanine dehydrogenase was proposed.

  6. Adsorption of Chromium Ion by Acid Activated Low Cost Carbon-Kinetic, Mechanistic, Thermodynamic and Equilibrium Studies

    Directory of Open Access Journals (Sweden)

    S. Arivoli

    2008-01-01

    Full Text Available A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing chromium ion. The parameters studied include agitation time, initial chromium ion concentration, carbon dose, pH and temperature. The adsorption followed first order reaction equation and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm obtained from the Langmuir isotherm plots were 27.40, 26.06, 26.06 and 26.17 mg/g respectively at an initial pH of 7.0 at 30, 40, 50 and 60°C. The temperature variation study showed that the chromium ion adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the chromium ion solutions. Almost 70% removal of chromium ion was observed at 60°C. The Langmuir and Freundlich isotherms obtained, positive ∆H0 value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of chromium ion on PDC involves physisorption mechanism.

  7. Kinetic, Mechanistic, Thermodynamic and Equilibrium Studies on the Adsorption of Rhodamine B by Acid Activated Low Cost Carbon

    Directory of Open Access Journals (Sweden)

    S. Arivoli

    2008-01-01

    Full Text Available A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing Rhodamine B (RDB. The parameters studied include agitation time, initial dye concentration, carbon dose, pH and temperature. The adsorption followed first order reaction equation and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm obtained from the Langmuir isotherm plots were 51.546, 47.236, 44.072 and 41.841 mg/g respectively at an initial pH of 7.0 at 30, 40, 50 and 60°C. The temperature variation study showed that the Rhodamine B adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the Rhodamine B solutions. Almost 90% removal of Rhodamine B was observed at 60°C. The Langmuir and Freundlich isotherms obtained, positive ΔH0 value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of Rhodamine B on PSC involves physisorption mechanism.

  8. Synthesis, structure-activity relationships, and mechanistic studies of 5-arylazo-tropolone derivatives as novel xanthine oxidase (XO) inhibitors.

    Science.gov (United States)

    Sato, Daisuke; Kisen, Takuya; Kumagai, Mina; Ohta, Kiminori

    2018-01-15

    Xanthine oxidase (XO) is an enzyme that contains molybdenum at the active site and catalyzes the oxidation of purine bases to uric acid. Even though XO inhibitors are widely used for the treatment of hyperuricemia and gout, only very few such compounds are clinically used as drugs for the treatment of these diseases. Given the unique physicochemical properties of tropolone, i.e., its chelating effect and the pKa value that is similar to that of carboxylic acid, we have synthesized 22 5-arylazotropolone derivatives as potential XO inhibitors. In vitro enzyme-inhibitory assays for XO revealed that 3-nitro derivative 1j showed the most potent XO inhibitory activity, which is by one order of magnitude more potent than allopurinol. An enzyme-kinetic study revealed that 1j inhibited the production of uric acid by XO both competitively and non-competitively. A docking-simulation study of 1j with XO suggested that the carbonyl and hydroxyl groups of the tropolone ring interact with the hydroxy group that acts as a ligand for molybdenum and the amino acid residues around the active site of XO. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Mechanistic Study of Electrolyte Additives to Stabilize High-Voltage Cathode–Electrolyte Interface in Lithium-Ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Han [Chemical; Maglia, Filippo [BMW Group, Munich 80788, Germany; Lamp, Peter [BMW Group, Munich 80788, Germany; Amine, Khalil [Chemical; Chen, Zonghai [Chemical

    2017-12-13

    Current developments of electrolyte additives to stabilize electrode-electrolyte interface in Li-ion batteries highly rely on a trial-and-error search, which involves repetitive testing and intensive amount of resources. The lack of understandings on the fundamental protection mechanisms of the additives significantly increases the difficulty for the transformational development of new additives. In this study, we investigated two types of individual protection routes to build a robust cathode-electrolyte interphase at high potentials: (i) a direct reduction in the catalytic decomposition of the electrolyte solvent; and (ii) formation of a “corrosion inhibitor film” that prevents severely attack and passivation from protons that generated from the solvent oxidation, even the decomposition of solvent cannot not mitigated. Effect of three exemplary electrolyte additives: (i) lithium difluoro(oxalato)borate (LiDFOB); (ii) 3-hexylthiophene (3HT); and (iii) tris(hexafluoro-iso-propyl)phosphate (HFiP), on LiNi0.6Mn0.2Co0.2O2 (NMC 622) cathode were investigated to validate our hypothesis. It is demonstrated that understandings of both electrolyte additives and solvent are essential and careful balance between the cathode protection mechanism of additives and their side effects is critical to obtain optimum results. More importantly, this study opens up new directions of rational design of functional electrolyte additives for the next generation high-energy density lithium-ion chemistries.

  10. Atmospheric chemistry of HFC-134a. Kinetic and mechanistic study of the CF3CFHO2 + NO2 reaction

    DEFF Research Database (Denmark)

    Møgelberg, T.E.; Nielsen, O.J.; Sehested, J.

    1994-01-01

    A pulse radiolysis system was used to study the kinetics of the reaction of CF3CFHO2 with NO2. By monitoring the rate of the decay of NO2 using its absorption at 400 nm the reaction rate constant was determined to be k = (5.0 +/- 0.5) x 10(-12) cm3 molecule-1 s-1. A long path length Fourier......-transform infrared technique was used to investigate the thermal decomposition of the product CF3CFHO2NO2. At 296 K in the presence of 700 Torr of air, decomposition of CF3CFHO2NO2 was rapid (greater than 90% decomposition within 3 min). The results are discussed in the context of atmospheric chemistry of CF3CFH2...

  11. Application of a Pyroprobe-Deuterium NMR System: Deuterium Tracing and Mechanistic Study of Upgrading Process for Lignin Model Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ben, Haoxi; Jarvis, Mark W.; Nimlos, Mark R.; Gjersing, Erica L.; Sturgeon, Matthew R.; Foust, Thomas D.; Ragauskas, Arthur J.; Biddy, Mary J.

    2016-04-21

    In this study, a pyroprobe-deuterium (2H) NMR system has been used to identify isotopomer products formed during the deuteration and ring opening of lignin model compounds. Several common model compounds for lignin and its upgraded products, including guaiacol, syringol, toluene, p-xylene, phenol, catechol, cyclohexane, methylcyclohexane, and methylcyclopentane, have been examined for selective ring opening. Similar pathways for upgrading of toluene and p-xylene has been found, which will undergo hydrogenation, methyl group elimination, and ring opening process, and benzene, cyclohexane, and methylcyclohexane have been found as major intermediates before ring opening. Very interestingly, the 2H NMR analysis for the deuterium-traced ring opening of catechol on Ir/..gamma..-Al2O3 is almost identical to the ring opening process for phenol. The ring opening processes for guaiacol and syringol appeared to be very complicated, as expected. Benzene, phenol, toluene, cyclohexane, and methylcyclohexane have been determined to be the major products.

  12. Comparative study of cyto- and genotoxic potential with mechanistic insights of tungsten oxide nano- and microparticles in lung carcinoma cells.

    Science.gov (United States)

    Chinde, Srinivas; Poornachandra, Y; Panyala, Archana; Kumari, Srinivas Indu; Yerramsetty, Suresh; Adicherla, Harikrishna; Grover, Paramjit

    2018-02-06

    The exigency of semiconductor and super capacitor tungsten oxide nanoparticles (WO 3 NPs) is increasing in various sectors. However, limited information on their toxicity and biological interactions are available. Hence, we explored the underlying mechanisms of toxicity induced by WO 3 NPs and their microparticles (MPs) using different concentrations (0-300 μg ml -1 ) in human lung carcinoma (A549) cells. The mean size of WO 3 NPs and MPs by transmission electron microscopy was 53.84 nm and 3.88 μm, respectively. WO 3 NPs induced reduction in cell viability, membrane damage and the degree of induction was size- and dose-dependent. There was a significant increase in the percentage tail DNA and micronuclei formation at 200 and 300 μg ml -1 after 24 hours of exposure. The DNA damage induced by WO 3 NPs could be attributed to increased oxidative stress and inflammation through reactive oxygen species generation, which correlated with the depletion of reduced glutathione content, catalase and an increase in malondialdehyde levels. Cellular uptake studies unveiled that both the particles were attached/surrounded to the cell membrane according to their size. In addition, NP inhibited the progression of the cell cycle in the G 2 /M phase. Other studies such as caspase-9 and -3 and Annexin-V-fluorescein isothiocyanate revealed that NPs induced intrinsic apoptotic cell death at 200 and 300 μg ml -1 concentrations. However, in comparison to NPs, WO 3 MPs did not incite any toxic effects at the tested concentrations. Under these experimental conditions, the no-observed-significant-effect level of WO 3 NPs was determined to be ≤200 μg ml -1 in A549 cells. Copyright © 2018 John Wiley & Sons, Ltd.

  13. Interaction of 2-aminopyrimidine with dichloro-[1-alkyl-2-(naphthylazo imidazole]palladium(II complexes : Kinetic and mechanistic studies

    Directory of Open Access Journals (Sweden)

    Saha Sushanta

    2007-10-01

    Full Text Available Abstract Background The anticancer properties of cisplatin and palladium(II complexes stem from the ability of the cis-MCl2 fragment to bind to DNA bases. However, cisplatin also interacts with non-cancer cells, mainly through bonding molecules containing -SH groups, resulting in nephrotoxicity. This has aroused interest in the design of palladium(II complexes of improved activity and lower toxicity. The reaction of DNA bases with palladium(II complexes with chelating N,N/donors of the cis-MCl2 configuration constitutes a model system that may help explore the mechanism of cisplatin's anticancer activity. Heterocyclic compounds are found widely in nature and are essential to many biochemical processes. Amongst these naturally occurring compounds, the most thoroughly studied is that of pyrimidine. This was one of the factors that encouraged this study into the kinetics and mechanism of the interaction of 2-aminopyrimidine (2-NH2-Pym with dichloro-{1-alkyl-2-(α-naphthylazoimidazole}palladium(II [Pd(α-NaiRCl2, 1] and dichloro-{1-alkyl-2-(β-naphthylazoimidazole}palladium(II [Pd(β-NaiRCl2, 2] complexes where the alkyl R = Me (a, Et (b, or Bz (c. Results 2-NH2-Pym reacts with 1a, 1b, and 1c to yield [{1-alkyl-2-(α-naphthylazoimidazole}bis(2-aminopyrimidine]palladium(II (3a, 3b, 3c dichloride and with 2a, 2b, and 2c to yield [{1-alkyl-2-(β-naphthylazoimidazole}bis(2-aminopyrimidine]palladium(II (4a, 4b, 4c dichloride in an acetonitrile (MeCN medium. The products were characterized using spectroscopic techniques (FT-IR, UV-Vis, NMR. The ligand substitution reactions follow second order kinetics – first order dependence on the concentration of the Pd(II complex and 2-NH2-Pym. Addition of LiCl to the reaction does not influence its rate. The thermodynamic parameters (standard enthalpy of activation, Δ‡H° and standard entropy of activation, Δ‡S° were determined from variable temperature kinetic studies. The magnitude of the second order

  14. Mechanistic Studies of Charge Injection from Metallic Electrodes into Organic Semiconductors Mediated by Ionic Functionalities: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Thuc-Quyen [UCSB; Bazan, Guillermo [UCSB; Mikhailovsky, Alexander [UCSB

    2014-04-15

    cost. During the execution of the project, main efforts were focused on the synthesis of new charge-bearing organic materials, such as CPEs and COEs, and block copolymers with neutral and ionic segments, studies of mechanisms responsible for the charge injection modulation in devices with ionic interlayers, and use of naturally occurring charged molecules for creation of enhanced devices. The studies allowed PIs to demonstrate the usefulness of the proposed approach for the improvement of operational parameters in model OLED and FET systems resulting in increased efficiency, decreased contact resistance, and possibility to use stable metals for fabrication of device electrodes. The successful proof-of-the-principle results potentially promise development of light-weight, low fabrication cost devices which can be used in consumer applications such as displays, solar cells, and printed electronic devices. Fundamental mechanisms responsible for the phenomena observed have been identified thus advancing the fundamental knowledgebase.

  15. Metal, bond energy, and ancillary ligand effects on actinide-carbon σ-bond hydrogenolysis. A kinetic and mechanistic study

    International Nuclear Information System (INIS)

    Lin, Z.; Marks, T.J.

    1987-01-01

    A kineticmechanistic study of actinide hydrocarbyl ligand hydrogenolysis (An-R + H 2 → An-H + RH) is reported. For the complex Cp' 2 TH(CH 2 -t-Bu)(O-t-Bu)(Cp' = eta 5 -Me 5 C 5 ), the rate law is first-order in organoactinide and first-order in H 2 , with k/sub H2/k/sub D2/ = 2.5 (4) and k/sub THF/k/sub toluene/ = 2.9 (4). For a series of complexes, hydrogenolysis rates span a range of ca. 10 5 with Cp' 2 ThCH 2 C(CH 3 ) 2 CH 2 ≅ Cp' 2 U(CH 2 -t-Bu) (too rapid to measure accurately) > Cp' 2 Th(CH 2 -t-Bu)[OCH(t-Bu) 2 ] = Cp' 2 Th(CH 2 -t-Bu)(O-t-Bu) > Cp' 2 Th(CH 2 -t-Bu)(Cl) > Me 2 Si(Me 4 C 5 ) 2 Th(n-Bu) 2 > Cp' 2 Th(n-Bu) 2 ≅ Cp' 2 ThMe 2 > Cp' 2 Th(Me)(O 3 SCF 3 ) > Cp' 2 Th(n-Bu)[OCG(t-Bu) 2 ] ≅ Cp' 2 Th(Me)[OSiMe 2 (t-Bu)] > Cp' 2 ZrMe 2 = Cp' 2 Th(rho-C 6 H 4 NMe 2 )(O-tu-Bu) > Cp' 2 Th(Ph)(O-t-Bu) > Cp' 2 U(Me)[OCH(t-Bu) 2 ] > Cp' 2 Th(Me)[OCH(t-Bu) 2 ]. In the majority of cases, the rate law is cleanly first-order in organoactinide over 3 or more half-lives. However, for Cp' 2 ThMe 2 → (Cp' 2 ThH 2 ) 2 , an intermediate is observe by NMR that is probably [Cp' 2 Th(Me)(μ-H)] 2 . For Cp' 2 Th(Me)(O 3 SCF 3 ), a follow-up reaction, which consumes Cp' 2 TH(H)(O 3 SCF 3 ) is detected. Variable-temperature kinetic studies yield ΔH** = 3.7 (2) kcalmol and ΔS double dagger = -50.8 (7) eu for Cp' 2 Th(CH 2 -t-Bu)(O-t-Bu) and ΔH double dagger = 9 (2) kcalmol and ΔS double dagger = -45 (5) eu for Cp' 2 U(Me)[OCH(O-t-Bu) 2

  16. Long-term habituation (LTH in the crab Chasmagnathus: a model for behavioral and mechanistic studies of memory

    Directory of Open Access Journals (Sweden)

    H. Maldonado

    1997-07-01

    Full Text Available A decade of studies on long-term habituation (LTH in the crab Chasmagnathus is reviewed. Upon sudden presentation of a passing object overhead, the crab reacts with an escape response that habituates promptly and for at least five days. LTH proved to be an instance of associative memory and showed context, stimulus frequency and circadian phase specificity. A strong training protocol (STP (³15 trials, intertrial interval (ITI of 171 s invariably yielded LTH, while a weak training protocol (WTP (£10 trials, ITI = 171 s invariably failed. STP was used with a presumably amnestic agent and WTP with a presumably hypermnestic agent. Remarkably, systemic administration of low doses was effective, which is likely to be due to the lack of an endothelial blood-brain barrier. LTH was blocked by inhibitors of protein and RNA synthesis, enhanced by protein kinase A (PKA activators and reduced by PKA inhibitors, facilitated by angiotensin II and IV and disrupted by saralasin. The presence of angiotensins and related compounds in the crab brain was demonstrated. Diverse results suggest that LTH includes two components: an initial memory produced by spaced training and mainly expressed at an initial phase of testing, and a retraining memory produced by massed training and expressed at a later phase of testing (retraining. The initial memory would be associative, context specific and sensitive to cycloheximide, while the retraining memory would be nonassociative, context independent and insensitive to cycloheximide

  17. Spotlight on the use of new natural surfactants in colloidal gas aphron (CGA) fluids: A mechanistic study

    Science.gov (United States)

    Ali Ahmadi, Mohammad; Galedarzadeh, Morteza; Reza Shadizadeh, Seyed

    2017-12-01

    Colloidal gas aphron-based (CGA) drilling fluids are defined as gas bubbles with diameters in ranges of 10 to 100 microns which are created by intensive stirring of an aphronizer surfactant solution at high speed. Furthermore, CGA-based drilling fluid properties like stability and aphron size distribution extremely depend on the inherent characteristics of the aphronizer surfactant. The selection of an appropriate surface active agent plays a vital role in the generation of micro-bubbles with the favorable characteristics. The primary motivation behind this paper is to evaluate the potential of new natural surfactants as aphronizer in CGA-based drilling fluids. Here, two new natural based surfactants derived from roots of Glycyrrhiza glabra and leaves of Matricaria recutita plant are implemented for the preparation of aphron-based fluids. The physico-chemical properties of the aphronized fluids prepared from these surfactants are studied by different fundamental tests comprising rheological characterizations, bubble size measurements, and stability tests. The effect of polymer and surfactant concentration was also evaluated. According to the experimental outcomes of this research, the two introduced natural surfactants are appropriate for generating CGA-based drilling fluids while they have no environmental impacts and have very low cost in comparison to commercial and industrial surfactants.

  18. Regulatory dendritic cells for promotion of liver transplant operational tolerance: Rationale for a clinical trial and accompanying mechanistic studies.

    Science.gov (United States)

    Thomson, Angus W; Humar, Abhinav; Lakkis, Fadi G; Metes, Diana M

    2017-10-31

    Dendritic cells (DC) are rare, bone marrow (BM)-derived innate immune cells that critically maintain self-tolerance in the healthy steady-state. Regulatory DC (DCreg) with capacity to suppress allograft rejection and promote transplant tolerance in pre-clinical models can readily be generated from BM precursors or circulating blood monocytes. These DCreg enhance allograft survival via various mechanisms, including promotion of regulatory T cells. In non-human primates receiving minimal immunosuppressive drug therapy (IS), infusion of DCreg of donor origin, one week before transplant, safely prolongs renal allograft survival and selectively attenuates anti-donor CD8 + memory T cell responses in the early post-transplant period. Based on these observations, and in view of the critical need to reduce patient dependence on non-specific IS agents that predispose to cardiometabolic side effects and renal insufficiency, we will conduct a first-in-human safety and preliminary efficacy study of donor-derived DCreg infusion to achieve early (18 months post-transplant) complete IS withdrawal in low-risk, living donor liver transplant recipients receiving standard-of-care IS (mycophenolate mofetil, tacrolimus and steroids). We will test the hypothesis that, although donor-derived DCreg are short-lived, they will induce robust donor-specific T cell hyporesponsiveness. We will examine immunological mechanisms by sequential analysis of blood and tissue samples, incorporating cutting-edge technologies. Copyright © 2017 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.

  19. A mechanistic study on Decontamination of Methyl Orange Dyes from Aqueous Phase by Mesoporous Pulp Waste and Polyaniline.

    Science.gov (United States)

    Li, Donglin; Yang, Yonggang; Li, Chaozheng; Liu, Yufang

    2017-04-01

    The dispersion-corrected density functional theory (DFT-D3) is used to investigate the mechanism of mesoporous pulp waste (MPW) and polyaniline (PANI) adsorptive removal methyl orange (MO) dye from their aqueous solutions. The results are absolutely reliable because of the sufficiently accurate method although such big systems are studied. It is demonstrated that hydrogen bond and Van Der Waals interactions play a significant role in MO adsorption by MPW and PANI. For MO adsorption by MPW, hydrogen bond and Van Der Waals interactions are both weakened in S 1 state. In contrast, hydrogen bond and Van Der Waals interactions between PANI and MO are both enhanced in S 1 state. The thermodynamic parameters such as enthalpy and free energy change reveal that the MO adsorption by MPW and PANI are spontaneous and exothermic. The adsorption of MO on MPW is less favorable in S 1 state and the adsorption of MO on PANI is more favorable in S 1 state. Therefore, the photoexcitation should be controlled during the MO adsorption by MPW and applied for MO adsorption by PANI. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Spin-dependent Hall effect in degenerate semiconductors: a theoretical study

    International Nuclear Information System (INIS)

    Idrish Miah, M

    2008-01-01

    The spin-dependent Hall (SDH) effect in degenerate semiconductors is investigated theoretically. Starting from a two-component drift-diffusion equation, an expression for SDH voltage (V SDH ) is derived, and drift and diffusive contributions to V SDH are studied. For the possible enhancement of the diffusive part, degenerate and nondegenerate cases are examined. We find that due to an increase in the diffusion coefficient V SDH increases in a degenerate semiconductor, consistent with the experimental observations. The expression for V SDH is reduced in three limiting cases, namely diffusive, drift-diffusion crossover and drift, and is analysed. The results agree with those obtained in recent theoretical investigations.

  1. Theoretical study of band alignment in nano-porous ZnO interacting with substituted Phthalocyanines

    OpenAIRE

    Wahnón Benarroch, Perla; Palacios Clemente, Pablo

    2011-01-01

    The aim of this work is the theoretical study of the band alignment between the two components of a hybrid organic-inorganic solar-cell. The working organic molecules are metal tetra-sulphonated phthalocyanines (M-Pc) and the inorganic material is nano-porous ZnO growth in the 001 direction. The theoretical calculations are being made using the density functional theory (DFT) using a GGA functional with the SIESTA code, which projects electron wave functions and density onto a real space grid...

  2. Red/blue shifting hydrogen bonds in acetonitrile-dimethyl sulphoxide solutions: FTIR and theoretical studies

    Science.gov (United States)

    Kannan, P. P.; Karthick, N. K.; Mahendraprabu, A.; Shanmugam, R.; Elangovan, A.; Arivazhagan, G.

    2017-07-01

    FTIR spectra of neat acetonitrile (AN), dimethyl sulphoxide (DMSO) and their binary solutions at various mole fractions have been recorded at room temperature. Theoretical calculations have also been carried out on acetonitrile (monomer, dimer), dimethyl sulphoxide (monomer, dimer) and AN - DMSO complex molecules. 1:2 (AN:DMSO) and 2:1 complexation through the red shifting (AN) C - H ⋯ O = S(DMSO) and blue shifting (DMSO) C - H ⋯ N ≡ C(AN) hydrogen bonds has been identified. The experimental and theoretical studies favour the presence of both the monomer and dimer in liquid AN, but only closed dimers in DMSO. The dipole-dipole interactions existed in AN and DMSO dimers disappear in the complex molecules. Partial π bond between S and O atoms, and three lone pair of electrons on oxygen atom of DMSO have been noticed theoretically.

  3. Impaired circulating CD4+ LAP+ regulatory T cells in patients with acute coronary syndrome and its mechanistic study.

    Directory of Open Access Journals (Sweden)

    Zheng-Feng Zhu

    Full Text Available OBJECTIVE: CD4(+ latency-associated peptide (LAP(+ regulatory T cells (Tregs are a newly discovered T cell subset in humans and the role of these cells in patients with acute coronary syndrome (ACS has not been explored. We designed to investigate whether circulating frequency and function of CD4(+LAP(+ Tregs are defective in ACS. METHODS: One hundred eleven ACS patients (acute myocardial infarction and unstable angina and 117 control patients were enrolled in the study. The control patients consisted of chronic stable angina (CSA and chest pain syndrome (CPS. The frequencies of circulating CD4(+LAP(+ Tregs and the expression of the transmembrane protein glycoprotein-A repetitions predominant (GARP on CD4(+ T cells were determined by flow cytometry. The function of CD4(+LAP(+ Tregs was detected using thymidine uptake. Serum interleukin-10 (IL-10 and transforming growth factor-β protein (TGF-β levels were detected using ELISA and expression of GARP mRNA in peripheral blood mononuclear cells (PBMCs was measured by real time-polymerase chain reaction. RESULTS: We found ACS patients had a significantly lower frequency of circulating CD4(+LAP(+ Tregs, and the function of these cells was reduced compared to controls. The expression of GARP in CD4(+ T cells and the serum levels of TGF-β in ACS patients were lower than those of control patients. The serum levels of IL-10 were similar between the two cohorts. CONCLUSIONS: A novel regulatory T cell subset, defined as CD4(+LAP(+ T cells is defective in ACS patients.

  4. Mechanistic Studies of Cobalt-Catalyzed C(sp2)-H Borylation of Five-Membered Heteroarenes with Pinacolborane.

    Science.gov (United States)

    Obligacion, Jennifer V; Chirik, Paul J

    2017-07-07

    Studies into the mechanism of cobalt-catalyzed C(sp 2 )-H borylation of five-membered heteroarenes with pinacolborane (HBPin) as the boron source established the catalyst resting state as the trans -cobalt(III) dihydride boryl, ( iPr PNP)Co(H) 2 (BPin) ( iPr PNP = 2,6-( i Pr 2 PCH 2 ) 2 (C 5 H 3 N)), at both low and high substrate conversions. The overall first-order rate law and observation of a normal deuterium kinetic isotope effect on the borylation of benzofuran versus benzofuran-2- d 1 support H 2 reductive elimination from the cobalt(III) dihydride boryl as the turnover-limiting step. These findings stand in contrast to that established previously for the borylation of 2,6-lutidine with the same cobalt precatalyst, where borylation of the 4-position of the pincer occurred faster than the substrate turnover and arene C-H activation by a cobalt(I) boryl is turnover-limiting. Evaluation of the catalytic activity of different cobalt precursors in the C-H borylation of benzofuran with HBPin established that the ligand design principles for C- H borylation depend on the identities of both the arene and the boron reagent used: electron-donating groups improve catalytic activity of the borylation of pyridines and arenes with B 2 Pin 2 , whereas electron-withdrawing groups improve catalytic activity of the borylation of five-membered heteroarenes with HBPin. Catalyst deactivation by P-C bond cleavage from a cobalt(I) hydride was observed in the C-H borylation of arene substrates with C-H bonds that are less acidic than those of five-membered heteroarenes using HBPin and explains the requirement of B 2 Pin 2 to achieve synthetically useful yields with these arene substrates.

  5. Effect of Garlic, Gingko, and St. John's Wort Extracts on the Pharmacokinetics of Fexofenadine: A Mechanistic Study.

    Science.gov (United States)

    Turkanovic, Jasmina; Ward, Michael B; Gerber, Jacobus P; Milne, Robert W

    2017-05-01

    The aim of this study was to determine the effects of garlic and ginkgo herbal extracts on the pharmacokinetics of the P-glycoprotein (P-gp)/organic anion-transporting polypeptides (Oatps) substrate fexofenadine. Male rats were dosed orally with garlic (120 mg/kg), ginkgo (17 mg/kg), St. John's wort (SJW; 1000 mg/kg; positive control), or Milli-Q water for 14 days. On day 15, rats either were administered fexofenadine (orally or i.v.), had their livers isolated and perfused with fexofenadine, or had their small intestines divided into four segments (SI-SIV) and analyzed for P-gp and Oatp1a5. In vivo, SJW increased the clearance of i.v. administered fexofenadine by 28%. Garlic increased the area under the curve 0-∞ and maximum plasma concentration of orally administered fexofenadine by 47% and 85%, respectively. Ginkgo and SJW had no effect on the oral absorption of fexofenadine. In the perfused liver, garlic, ginkgo, and SJW increased the biliary clearance of fexofenadine with respect to perfusate by 71%, 121%, and 234%, respectively. SJW increased the biliary clearance relative to the liver concentration by 64%. The ratio of liver to perfusate concentrations significantly increased in all treated groups. The expression of Oatp1a5 in SI was increased by garlic (88%) and SJW (63%). There were no significant changes in the expression of P-gp. Induction of intestinal Oatp1a5 by garlic may explain the increased absorption of orally administered fexofenadine. Ginkgo had no effect on the expression of intestinal P-gp or Oatp1a5. A dual inductive effect by SJW on opposing intestinal epithelial transport by Oatp1a5 and P-gp remains a possibility. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

  6. A mechanistic study on the reaction pathways leading to benzene and naphthalene in cellulose vapor phase cracking

    International Nuclear Information System (INIS)

    Norinaga, Koyo; Yang, Huamei; Tanaka, Ryota; Appari, Srinivas; Iwanaga, Keita; Takashima, Yuka; Kudo, Shinji; Shoji, Tetsuya; Hayashi, Jun-ichiro

    2014-01-01

    The reaction pathways leading to aromatic hydrocarbons such as benzene and naphthalene in gas-phase reactions of multi-component mixtures derived from cellulose fast pyrolysis were studied both experimentally and numerically. A two-stage tubular reactor was used for evaluating the reaction kinetics of secondary vapor phase cracking of the nascent pyrolysates at temperature ranging from 400 to 900 °C, residence time from 0.2 to 4.3 s, and at 241 kPa. The products of alkyne and diene were identified from the primary pyrolysis of cellulose even at low temperature range 500–600 °C. These products include acetylene, propyne, propadiene, vinylacetylene, and cyclopentadiene. Experiments were also numerically validated by a detailed chemical kinetic model consisting of more than 8000 elementary step-like reactions with over 500 chemical species. Acceptable capabilities of the kinetic model in predicting concentration profiles of the products enabled us to assess reaction pathways leading to benzene and naphthalene via the alkyne and diene from primary pyrolysates of cellulose. C 3 alkyne and diene are primary precursors of benzene at 650 °C, while combination of ethylene and vinylacetylene produces benzene dominantly at 850 °C. Cyclopentadiene is a prominent precursor of naphthalene. Combination of acetylene with propyne or allyl radical leads to the formation of cyclopentadiene. Furan and acrolein are likely important alkyne precursors in cellulose pyrolysis at low temperature, whereas dehydrogenations of olefins are major route to alkyne at high temperatures. - Highlights: • Analytical pyrolysis experiments provided data for kinetic modeling. • Detailed chemical kinetic model was used and evaluated. • Alkyne and diene were important intermediates for aromatic hydrocarbon formation. • Reaction pathways leading to aromatic hydrocarbons were proposed

  7. Peptide inhibitor of complement C1 (PIC1, a novel suppressor of classical pathway activation: mechanistic studies and clinical potential

    Directory of Open Access Journals (Sweden)

    Julia A Sharp

    2014-08-01

    Full Text Available The classical pathway of complement plays multiple physiological roles including modulating immunological effectors initiated by adaptive immune responses as well as an essential homeostatic role in the clearance of damaged self-antigens. However, dysregulated classical pathway activation is associated with antibody-initiated, inflammatory diseases processes like cold agglutinin disease (CAD, acute intravascular hemolytic transfusion reaction (AIHTR and acute/hyperacute transplantation rejection. To date, only one putative classical pathway inhibitor, C1 esterase inhibitor (C1-INH, is currently commercially available and its only approved indication is for replacement treatment in hereditary angioedema (HAE, which is predominantly a kinin pathway disease. Given the variety of disease conditions in which the classical pathway is implicated, development of therapeutics that specifically inhibit complement initiation represents a major unmet medical need. Our laboratory has identified a peptide that specifically inhibits the classical and lectin pathways of complement. In vitro studies have demonstrated that these Peptide Inhibitors of Complement C1 (PIC1 bind to the collagen-like region of the initiator molecule of the classical pathway, C1q. PIC1 binding to C1q blocks activation of the associated serine proteases (C1s-C1r-C1r-C1s and subsequent downstream complement activation. Rational design optimization of PIC1 has resulted in the generation of a highly potent derivative of fifteen amino acids. PIC1 inhibits classical pathway mediated complement activation in ABO incompatibility in vitro as well as inhibiting classical pathway activation in vivo in rats. This review will focus on the pre-clinical development of PIC1 and discuss its potential as a therapeutic in antibody-mediated classical pathway disease, specifically AIHTR.

  8. Aqueous Leaf Extract of Withania somnifera as a Potential Neuroprotective Agent in Sleep-deprived Rats: a Mechanistic Study.

    Science.gov (United States)

    Manchanda, Shaffi; Mishra, Rachana; Singh, Rumani; Kaur, Taranjeet; Kaur, Gurcharan

    2017-05-01

    Modern lifestyle and sustained stress of professional commitments in the current societal set up often disrupts the normal sleep cycle and duration which is known to lead to cognitive impairments. In the present study, we report whether leaf extract of Withania somnifera (Ashwagandha) has potential neuroprotective role in acute stress of sleep deprivation. Experiments were performed on three groups of adult Wistar rats: group 1 (vehicle treated-undisturbed sleep [VUD]), group 2 (vehicle treated-sleep deprived [VSD]), and group 3 (ASH-WEX treated-sleep deprived [WSD]). Groups 1 and 2 received single oral feeding of vehicle and group 3 received ASH-WEX orally (140 mg/kg or 1 ml/250 g of body weight) for 15 consecutive days. Immediately after this regimen, animals from group 1 were allowed undisturbed sleep (between 6 a.m. and 6 p.m.), whereas rats of groups 2 and 3 were deprived of sleep during this period. We observed that WSD rats showed significant improvement in their performance in behavioral tests as compared to VSD group. At the molecular level, VSD rats showed acute change in the expression of proteins involved in synaptic plasticity, cell survival, and apoptosis in the hippocampus region of brain, which was suppressed by ASH-WEX treatment thus indicating decreased cellular stress and apoptosis in WSD group. This data suggest that Ashwagandha may be a potential agent to suppress the acute effects of sleep loss on learning and memory impairments and may emerge as a novel supplement to control SD-induced cognitive impairments.

  9. From nanocontainer to nanocatalyst: Mechanistic studies of [2+2] photodimerization of coumarin derivatives within cucurbit[8]uril

    Science.gov (United States)

    Pemberton, Barry Charles

    Controlling photoreactions remains a formidable challenge to chemists who have developed several approaches with varying degrees of success to achieve high reactivity/selectivity. Following nature's footprints, chemists have explored the use of confined media for controlling photoreactions. This thesis explores catalytic aspects of a water-soluble supramolecule known as a cucurbituril. Cucurbituril is a macrocyclic oligomer with a large enough cavity to sequester two guest molecules of appropriate size. The guest molecules explored in this thesis is coumarins. The model investigation involves host-guest complexes between cucurbit[8]uril (CB[8]) and coumarin to study the [2+2] photodimerization in water through various spectroscopic techniques. Our initial investigations explored the formation of host-guest complexes with coumarin guests that interacted with CB[8] host. This host guest complexation was used to explore and control photochemical reaction and photophysical properties of encapsulated coumarin guest molecules. The host-guest complexation was found to be dependent on the polarity of the coumarin and the volume constraints imparted by the CB[8] cavity. Observational insights from various coumarins provided insights into formation of host-guest complexes with CB[8]. Some coumarins do not form complexes but if they do they can form 1:1 and 1:2 host guest complexes as well as dynamic host-guest complexes (mixture of 1:1 and 1:2 host-guest complexes). Using dynamic host-guest complexes, we explored the use of CB[8] as a photocatalysts. Photodimerization of 6-methylcoumarin was explored as a model system to understand the supramolecular aspects of photocatalysis. The mechanism for photocatalysis was elucidated using various spectroscopic techniques. Both steady state and time-resolved experiments were carried to ascertain the thermodynamic and kinetic aspects of the supramolecular catalytic process. Spectroscopic investigations provided insights into vital role

  10. A mechanistic study of Toxoplasma gondii ROP18 inhibiting differentiation of C17.2 neural stem cells

    Directory of Open Access Journals (Sweden)

    Xian Zhang

    2017-11-01

    Full Text Available Abstract Background Congenital infection of Toxoplasma gondii is an important factor causing birth defects. The neural stem cells (NSCs are found to be one of the target cells for the parasite during development of the brain. As a key virulence factor of the parasite that hijacks host cellular functions, ROP18 has been demonstrated to mediate the inhibition of host innate and adaptive immune responses through specific binding different host immunity related molecules. However, its pathogenic actions in NSCs remain elusive. Results In the present study, ROP18 recombinant adenovirus (Ad-ROP18 was constructed and used to infect C17.2 NSCs. After 3d- or 5d–culture in differentiation medium, the differentiation of C17.2 NSCs and the activity of the Wnt/β-catenin signaling pathway were detected. The results showed that the protein level of βIII-tubulin, a marker of neurons, in the Ad-ROP18-transfected C17.2 NSCs was significantly decreased, indicating that the differentiation of C17.2 NSCs was inhibited by the ROP18. The β-catenin level in the Ad-ROP18-transfected C17.2 NSCs was found to be lower than that in the Ad group. Also, neurogenin1 (Ngn1 and neurogenin2 (Ngn2 were downregulated significantly (P < 0.05 in the Ad-ROP18-transfected C17.2 NSCs compared to the Ad group. Accordingly, the TOP flash/FOP flash dual-luciferase report system showed that the transfection of Ad-ROP18 decreased the Wnt/β-catenin pathway activity in the C17.2 NSCs. Conclusions The inhibition effect of the ROP18 from T. gondii (TgROP18 on the neuronal differentiation of C17.2 NSCs was at least partly mediated through inhibiting the activity of the Wnt/β-catenin signaling pathway, eventually resulting in the downregulation of Ngn1 and Ngn2. The findings help to better understand potential mechanisms of brain pathology induced by TgROP18.

  11. Mechanistic studies of the inhibition of MutT dGTPase by the carcinogenic metal Ni(II).

    Science.gov (United States)

    Porter, D W; Nelson, V C; Fivash, M J; Kasprzak, K S

    1996-12-01

    Promutagenic 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) levels are increased in DNA of animals exposed to carcinogenic metals, such as Ni(II). Besides being generated directly in genomic DNA, 8-oxo-dG may be incorporated there from 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP), a product of oxidative damage to the nucleotide pool. The Escherichia coli dGTPase MutT, and analogous dGTPases in rats and humans, have been suggested as a defense against such incorporation because they hydrolyze 8-oxo-dGTP to 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-monophosphate (8-oxo-dGMP). MutT and its mammalian counterparts are Mg(II)-dependent enzymes. Ni(II), in turn, is known to interact antagonistically with Mg(II) in biological systems. Thus, we hypothesized that Ni(II) might inhibit the activity of MutT. As an initial examination of this hypothesis, we conducted enzyme kinetic studies of MutT to determine the effect of Ni(II) on MutT activity and the mechanisms involved. As found, Ni(II) inhibited MutT in a concentration-dependent manner when either dGTP or 8-oxo-dGTP was the nucleotide substrate. Ni(II) was determined to be an uncompetitive inhibitor of MutT with respect to Mg(II) when dGTP was the substrate, with apparent Ki of 1.2 mM Ni(II), and a noncompetitive inhibitor with respect to Mg(II) when 8-oxo-dGTP was the substrate, with apparent Ki of 0.9 mM Ni(II). Hence, the two metal cations did not compete with each other for binding at the MutT active site. This makes it difficult to predict Ni(II) effects on 8-oxo-dGTPases of other species. However, based upon the amino acid sequences of human and rat MutT-like dGTPases, their capacity for Ni(II) binding should be greater than that of MutT. Whether this could lead to stronger inhibition of those enzymes by Ni(II), or not, remains to be investigated.

  12. Mechanistic studies of anticancer aptamer AS1411 reveal a novel role for nucleolin in regulating Rac1 activation.

    Science.gov (United States)

    Reyes-Reyes, E Merit; Šalipur, Francesca R; Shams, Mitra; Forsthoefel, Matthew K; Bates, Paula J

    2015-08-01

    AS1411 is a G-rich quadruplex-forming oligodeoxynucleotide that binds specifically to nucleolin, a protein found on the surface and in the cytoplasm of most malignant cells but absent from the surface/cytoplasm of most normal cells. AS1411 has shown promising clinical activity and is being widely used as a tumor-targeting agent, but its mechanism of action is not fully understood. Previously, we showed that AS1411 is taken up in cancer cells by macropinocytosis (fluid phase endocytosis) and subsequently stimulates further macropinocytosis by a nucleolin-dependent mechanism. In the current study, we have investigated the significance and molecular mechanisms of AS1411-induced macropinocytosis. Our results indicate that the antiproliferative activity of AS1411 in various cell lines correlated with its capacity to stimulate macropinocytosis. In DU145 prostate cancer cells, AS1411 induced activation of EGFR, Akt, p38, and Rac1. Activation of Akt and p38 were not critical for AS1411 activity because Akt activation was not observed in all AS1411-responsive cell lines and knockdown of p38 had no effect on AS1411's ability to inhibit proliferation. On the other hand, activation of EGFR and Rac1 appeared to play a role in AS1411 activity in all cancer cell lines examined (DU145, MDA-MB-468, A549, LNCaP) and their inhibition significantly reduced AS1411-mediated macropinocytosis and AS1411 antiproliferative activity. Interestingly, downregulation of nucleolin expression by siRNA also produced a substantial increase in activated Rac1, revealing a previously unknown role for nucleolin as a negative regulator of Rac1 activation. Our results are consistent with a model whereby AS1411 binding to nucleolin leads to sustained activation of Rac1 and causes methuosis, a novel type of nonapoptotic cell death characterized by hyperstimulation of macropinocytosis. We speculate that methuosis is a tumor/metastasis suppressor mechanism that opposes the malignant functions of Rac1 and that

  13. Theoretical study, and infrared and Raman spectra of copper(II) chelated complex with dibenzoylmethane

    DEFF Research Database (Denmark)

    Nekoei, A.-R.; Vakili, M.; Hakimi-Tabar, M.

    2014-01-01

    There are some discrepancies in both the vibrational assignments and in the metal-ligand (M-L) bond strengths predicted in the previous studies on the copper (II) chelated complex of dibenzoylmethane, Cu(dbm)2. Also, there is a lack of theoretical structure, Raman spectrum and full vibrational as...

  14. [Habermas and Paulo Freire: theoretical referrals for the study on communication in nursing].

    Science.gov (United States)

    Larocca, Liliana Muller; Mazza, Verônica de Azevedo

    2003-08-01

    The present work has the objective of introducing the ideas of Jürgen Habermas and Paulo Freire about the dialogue as a fundamental human phenomenon, data on their trajectories of life, ideological approaches when locating the human being through history and their relevance as theoretical referrals for the study on communication in the process of the nurse's work.

  15. A Comparative Study of Theoretical Graph Models for Characterizing Structural Networks of Human Brain

    Directory of Open Access Journals (Sweden)

    Xiaojin Li

    2013-01-01

    Full Text Available Previous studies have investigated both structural and functional brain networks via graph-theoretical methods. However, there is an important issue that has not been adequately discussed before: what is the optimal theoretical graph model for describing the structural networks of human brain? In this paper, we perform a comparative study to address this problem. Firstly, large-scale cortical regions of interest (ROIs are localized by recently developed and validated brain reference system named Dense Individualized Common Connectivity-based Cortical Landmarks (DICCCOL to address the limitations in the identification of the brain network ROIs in previous studies. Then, we construct structural brain networks based on diffusion tensor imaging (DTI data. Afterwards, the global and local graph properties of the constructed structural brain networks are measured using the state-of-the-art graph analysis algorithms and tools and are further compared with seven popular theoretical graph models. In addition, we compare the topological properties between two graph models, namely, stickiness-index-based model (STICKY and scale-free gene duplication model (SF-GD, that have higher similarity with the real structural brain networks in terms of global and local graph properties. Our experimental results suggest that among the seven theoretical graph models compared in this study, STICKY and SF-GD models have better performances in characterizing the structural human brain network.

  16. A Theoretical Framework to Study Variations in Workplace Violence Experienced by Emergency Responders

    NARCIS (Netherlands)

    L. van Reemst (Lisa)

    2016-01-01

    textabstractEmergency responders are often sent to the front line and are often confronted with aggression and violence in inter- action with citizens. According to previous studies, some professionals experience more workplace violence than others. In this article, the theoretical framework to

  17. A theoretical framework to study variations in workplace violence experienced by emergency responders

    NARCIS (Netherlands)

    L. van Reemst (Lisa)

    2016-01-01

    markdownabstractEmergency responders are often sent to the front line and are often confronted with aggression and violence in interaction with citizens. According to previous studies, some professionals experience more workplace violence than others. In this article, the theoretical framework to

  18. Theoretical study of the ground state of (EDO-TTF)(2)PF6

    NARCIS (Netherlands)

    Linker, Gerrit-Jan; van Duijnen, Piet Th.; van Loosdrecht, Paul H.M.; Broer, Ria

    2015-01-01

    In this paper we present a theoretical study of the nature of the ground state of the (EDO-TTF)(2)PF6 charge transfer salt by using ab initio quantum chemical theory for clusters in vacuum, for embedded clusters and for the periodic system. Exemplary for other organic charge transfer systems, we

  19. Theoretical and experimental study of high-Q resonant modes in terahertz optical systems

    NARCIS (Netherlands)

    Jellema, Willem; Withington, S.; Trappe, Neil; Murphy, J. A.; Wild, Wolfgang

    2004-01-01

    The existence of multiple reflections in terahertz optical system causes numerous problems in applications ranging from astronomical to medical instrumentation. We have performed a detailed theoretical study, using waveguide and free-space modal matching, of the high-Q modes that appear on THz

  20. Theoretical studies on the stability of the salts formed by DTDO with ...

    Indian Academy of Sciences (India)

    Toggle navigation. Logo of the Indian Academy of Sciences. Indian Academy of Sciences. Home · About ... Home; Journals; Journal of Chemical Sciences; Volume 127; Issue 4. Theoretical studies on the stability of the salts formed by ... Keywords. Salts; conformations; stability; density functional theory, energetic materials.

  1. Coulomb drag in anisotropic systems: a theoretical study on a double-layer phosphorene

    NARCIS (Netherlands)

    Saberi-Pouya, S.; Vazifehshenas, T.; Farmanbar Gelepordsari, M.; Salavati-Fard, T.

    2016-01-01

    We theoretically study the Coulomb drag resistivity in a double-layer electron system with highly anisotropic parabolic band structure using Boltzmann transport theory. As an example, we consider a double-layer phosphorene on which we apply our formalism. This approach, in principle, can be tuned

  2. Theoretical study on ground-state triple proton transfer for formic ...

    Indian Academy of Sciences (India)

    Theoretical study on ground-state proton/H-atom exchange in formic acid clusters through different H-bonded bridges. HUA FANG. Department of Chemistry and Material Science, College of Science, Nanjing Forestry University, Nanjing 210037, People's Republic of China. Email: susanfang20@gmail.com. Contents.

  3. Theoretical study of the reactivity trends in the Cl-abstraction ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 123; Issue 5. Theoretical study of the reactivity trends in the Cl-abstraction reactions of CHCl3 + CHX·−/CX 2 · − (X = Cl, Br and I). Jun Xi Liang Zhi Yuan Geng Yong Cheng Wang. Volume 123 Issue 5 September 2011 pp 755-763 ...

  4. Theoretical study of two-element array of equilateral triangular patch ...

    Indian Academy of Sciences (India)

    The radiation characteristics of a two-element array of equilateral triangular patch microstrip antenna on a ferrite substrate are studied theoretically by considering the presence of bias magnetic field in the direction of propagation of electromagnetic waves. It is found that the natural modes of propagation in the direction of ...

  5. Interaction between adrenaline and dibenzo-18-crown-6: Electrochemical, nuclear magnetic resonance, and theoretical study

    Science.gov (United States)

    Yu, Zhang-Yu; Liu, Tao; Wang, Xue-Liang

    2014-12-01

    The interaction between adrenaline (Ad) and dibenzo-18-crown-6 (DB18C6) was studied by cyclic voltammetry, nuclear magnetic resonance spectroscopy, and the theoretical calculations, respectively. The results show that DB18C6 will affect the electron transfer properties of Ad. DB18C6 can form stable supramolecular complexes with Ad through ion-dipole and hydrogen bond interactions.

  6. Electronic structure of copper phthalocyanine : An experimental and theoretical study of occupied and unoccupied levels

    NARCIS (Netherlands)

    Evangelista, Fabrizio; Carravetta, Vincenzo; Stefani, Giovanni; Jansik, Branislav; Alagia, Michele; Stranges, Stefano; Ruocco, Alessandro

    2007-01-01

    An experimental and theoretical study of the electronic structure of copper phthalocyanine (CuPc) molecule is presented. We performed x-ray photoemission spectroscopy (XPS) and photoabsorption [x-ray absorption near-edge structure (XANES)] gas phase experiments and we compared the results with

  7. Structural changes in 2-diarylthiophene-substituted starburst compounds upon charging: a theoretical and spectroelectrochemical study.

    Science.gov (United States)

    Solc, Roland; Lukes, Vladimír; Rapta, Peter; Hartmann, Horst; Dunsch, Lothar

    2008-12-01

    The role of charging in structural changes of 2-diarylaminothiophene-substituted starburst compounds is clarified by combining theoretical and spectroelectrochemical studies. A systematic and comparative theoretical calculation based on density functional theory and semiempirical Austin Model 1 (AM1) calculations is performed on the neutral and charged states of four model tris(5-diarylamino-5-thienyl)-terminated starburst compounds with a central triphenylamine and 1,3,5-triphenylbenzene moiety. Our results indicate that the charging of molecules leads to structural changes by quinoid-type components mostly on the dendrimers terminated by phenothiazinyl fragments. Based on the optimal geometries, the spectroscopic properties were calculated using the semiempirical Zerner's intermediate neglect overlap method. The presented theoretical results and the spin electron distributions of charged states and their spectra are supported by the spectroelectrochemical observations caused by the different electron localization within the studied molecules after charging. The satisfactory agreement between theoretical electronic transitions and experimental values indicates that a rational design of tunable molecular layers in organic devices based on the starburst compounds described is possible.

  8. Theoretical spectroscopic study of the conjugate microcystin-LR-europium cryptate

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Julio G.; Dutra, Jose Diogo L.; Costa Junior, Nivan B. da; Freire, Ricardo O., E-mail: rfreire@ufs.br [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Departamento de Quimica; Alves Junior, Severino; Sa, Gilberto F. de [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Quimica Fundamental

    2013-02-15

    In this work, theoretical tools were used to study spectroscopic properties of the conjugate microcystin-LR-europium cryptate. The Sparkle/AM1 model was applied to predict the geometry of the system and the INDO/S-CIS model was used to calculate the excited state energies. Based on the Judd-Ofelt theory, the intensity parameters were predicted and a theoretical model based on the theory of the 4f-4f transitions was applied to calculate energy transfer and backtransfer rates, radiative and non-radiative decay rates, quantum efficiency and quantum yield. A detailed study of the luminescent properties of the conjugate Microcystin-LR-europium cryptate was carried out. The results show that the theoretical quantum yield of luminescence of 23% is in good agreement with the experimental value published. This fact suggests that this theoretical protocol can be used to design new systems in order to improve their luminescence properties. The results suggest that this luminescent system may be a good conjugate for using in assay ELISA for detection by luminescence of the Microcystin-LR in water. (author)

  9. Curriculum, curriculum development, curriculum studies? Problematising theoretical ambiguities in doctoral theses in the education field

    Directory of Open Access Journals (Sweden)

    Petro du Preez

    2014-06-01

    Full Text Available Theoretical ambiguities in curriculum studies result in conceptual mayhem. Accordingly, they hinder the development of the complicated conversation on curriculum as a verb. This article aims to contribute to reconceptualizing curriculum studies as a dynamic social practice that aspires to thinking and acting with intelligences and sensitivity so as to understand oneself and others. It also raises awareness that equating all forms of research on curriculum with curriculum studies dilutes the scope of the conversation. This exploration asks two key questions: What is the nature of doctoral theses in the field of education's theoretical contributions to nuances of curriculum (curriculum, curriculum development, and curriculum studies? In what ways do these theses perpetuate or even add to current ambiguities in the discipline of curriculum studies? The exploration of these two questions draws on a critical meta-study of 511 theses completed in South African universities (2005-2012 conducted using a three level process. It appears that the main detractions of these theses are that some of them see curriculum studies as a dumping ground and others make no theoretical contribution to the discipline. The article concludes by suggesting ways which would encourage the intellectual advancement of curriculum studies through rigorous disciplinarity.

  10. Acridone derivative 8a induces oxidative stress-mediated apoptosis in CCRF-CEM leukemia cells: application of metabolomics in mechanistic studies of antitumor agents.

    Directory of Open Access Journals (Sweden)

    Yini Wang

    Full Text Available A new acridone derivative, 2-aminoacetamido-10-(3, 5-dimethoxy-benzyl-9(10H-acridone hydrochloride (named 8a synthesized in our lab shows potent antitumor activity, but the mechanism of action remains unclear. Herein, we report the use of an UPLC/Q-TOF MS metabolomic approach to study the effects of three compounds with structures optimized step-by-step, 9(10H-acridone (A, 10-(3,5-dimethoxybenzyl-9(10H-acridone (I, and 8a, on CCRF-CEM leukemia cells and to shed new light on the probable antitumor mechanism of 8a. Acquired data were processed by principal component analysis (PCA and orthogonal partial least squares discriminant analysis (OPLS-DA to identify potential biomarkers. Comparing 8a-treated CCRF-CEM leukemia cells with vehicle control (DMSO, 23 distinct metabolites involved in five metabolic pathways were identified. Metabolites from glutathione (GSH and glycerophospholipid metabolism were investigated in detail, and results showed that GSH level and the reduced/oxidized glutathione (GSH/GSSG ratio were significantly decreased in 8a-treated cells, while L-cysteinyl-glycine (L-Cys-Gly and glutamate were greatly increased. In glycerophospholipid metabolism, cell membrane components phosphatidylcholines (PCs were decreased in 8a-treated cells, while the oxidative products lysophosphatidylcholines (LPCs were significantly increased. We further found that in 8a-treated cells, the reactive oxygen species (ROS and lipid peroxidation product malondialdehyde (MDA were notably increased, accompanied with decrease of mitochondrial transmembrane potential, release of cytochrome C and activation of caspase-3. Taken together our results suggest that the acridone derivative 8a induces oxidative stress-mediated apoptosis in CCRF-CEM leukemia cells. The UPLC/Q-TOF MS based metabolomic approach provides novel insights into the mechanistic studies of antitumor drugs from a point distinct from traditional biological investigations.

  11. How to use mechanistic effect models in environmental risk assessment of pesticides: Case studies and recommendations from the SETAC workshop MODELINK.

    Science.gov (United States)

    Hommen, Udo; Forbes, Valery; Grimm, Volker; Preuss, Thomas G; Thorbek, Pernille; Ducrot, Virginie

    2016-01-01

    Mechanistic effect models (MEMs) are useful tools for ecological risk assessment of chemicals to complement experimentation. However, currently no recommendations exist for how to use them in risk assessments. Therefore, the Society of Environmental Toxicology and Chemistry (SETAC) MODELINK workshop aimed at providing guidance for when and how to apply MEMs in regulatory risk assessments. The workshop focused on risk assessment of plant protection products under Regulation (EC) No 1107/2009 using MEMs at the organism and population levels. Realistic applications of MEMs were demonstrated in 6 case studies covering assessments for plants, invertebrates, and vertebrates in aquatic and terrestrial habitats. From the case studies and their evaluation, 12 recommendations on the future use of MEMs were formulated, addressing the issues of how to translate specific protection goals into workable questions, how to select species and scenarios to be modeled, and where and how to fit MEMs into current and future risk assessment schemes. The most important recommendations are that protection goals should be made more quantitative; the species to be modeled must be vulnerable not only regarding toxic effects but also regarding their life history and dispersal traits; the models should be as realistic as possible for a specific risk assessment question, and the level of conservatism required for a specific risk assessment should be reached by designing appropriately conservative environmental and exposure scenarios; scenarios should include different regions of the European Union (EU) and different crops; in the long run, generic MEMs covering relevant species based on representative scenarios should be developed, which will require EU-level joint initiatives of all stakeholders involved. The main conclusion from the MODELINK workshop is that the considerable effort required for making MEMs an integral part of environmental risk assessment of pesticides is worthwhile, because

  12. Theoretical Study of the Effects of Di-Muonic Molecules on Muon-Catalyzed Fusion

    Science.gov (United States)

    2012-03-01

    MOLECULES ON MUON -CATALYZED FUSION DISSERTATION Eugene V. Sheely, Lieutenant Colonel, USA DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY...THEORETICAL STUDY OF THE EFFECTS OF DI-MUONIC MOLECULES ON MUON -CATALYZED FUSION DISSERTATION Presented to the Faculty...potential of enhancing the muon -catalyzed fusion reaction rate. In order to study these di-muonic molecules a method of non-adiabatic quantum mechanics

  13. Studying Scale-Up and Spread as Social Practice: Theoretical Introduction and Empirical Case Study.

    Science.gov (United States)

    Shaw, James; Shaw, Sara; Wherton, Joseph; Hughes, Gemma; Greenhalgh, Trisha

    2017-07-07

    Health and care technologies often succeed on a small scale but fail to achieve widespread use (scale-up) or become routine practice in other settings (spread). One reason for this is under-theorization of the process of scale-up and spread, for which a potentially fruitful theoretical approach is to consider the adoption and use of technologies as social practices. This study aimed to use an in-depth case study of assisted living to explore the feasibility and usefulness of a social practice approach to explaining the scale-up of an assisted-living technology across a local system of health and social care. This was an individual case study of the implementation of a Global Positioning System (GPS) "geo-fence" for a person living with dementia, nested in a much wider program of ethnographic research and organizational case study of technology implementation across health and social care (Studies in Co-creating Assisted Living Solutions [SCALS] in the United Kingdom). A layered sociological analysis included micro-level data on the index case, meso-level data on the organization, and macro-level data on the wider social, technological, economic, and political context. Data (interviews, ethnographic notes, and documents) were analyzed and synthesized using structuration theory. A social practice lens enabled the uptake of the GPS technology to be studied in the context of what human actors found salient, meaningful, ethical, legal, materially possible, and professionally or culturally appropriate in particular social situations. Data extracts were used to illustrate three exemplar findings. First, professional practice is (and probably always will be) oriented not to "implementing technologies" but to providing excellent, ethical care to sick and vulnerable individuals. Second, in order to "work," health and care technologies rely heavily on human relationships and situated knowledge. Third, such technologies do not just need to be adopted by individuals; they need

  14. Intake and time dependence of blueberry flavonoid-induced improvements in vascular function: a randomized, controlled, double-blind, crossover intervention study with mechanistic insights into biological activity.

    Science.gov (United States)

    Rodriguez-Mateos, Ana; Rendeiro, Catarina; Bergillos-Meca, Triana; Tabatabaee, Setareh; George, Trevor W; Heiss, Christian; Spencer, Jeremy Pe

    2013-11-01

    There are very limited data regarding the effects of blueberry flavonoid intake on vascular function in healthy humans. We investigated the impact of blueberry flavonoid intake on endothelial function in healthy men and assessed potential mechanisms of action by the assessment of circulating metabolites and neutrophil NADPH oxidase activity. Two randomized, controlled, double-blind, crossover human-intervention trials were conducted with 21 healthy men. Initially, the impact of blueberry flavonoid intake on flow-mediated dilation (FMD) and polyphenol absorption and metabolism was assessed at baseline and 1, 2, 4, and 6 h after consumption of blueberry containing 766, 1278, and 1791 mg total blueberry polyphenols or a macronutrient- and micronutrient-matched control drink (0 mg total blueberry polyphenols). Second, an intake-dependence study was conducted (from baseline to 1 h) with 319, 637, 766, 1278, and 1791 mg total blueberry polyphenols and a control. We observed a biphasic time-dependent increase in FMD, with significant increases at 1-2 and 6 h after consumption of blueberry polyphenols. No significant intake-dependence was observed between 766 and 1791 mg. However, at 1 h after consumption, FMD increased dose dependently to ≤766 mg total blueberry polyphenol intake, after which FMD plateaued. Increases in FMD were closely linked to increases in circulating metabolites and by decreases in neutrophil NADPH oxidase activity at 1-2 and 6 h. Blueberry intake acutely improves vascular function in healthy men in a time- and intake-dependent manner. These benefits may be mechanistically linked to the actions of circulating phenolic metabolites on neutrophil NADPH oxidase activity. This trial was registered at clinicaltrials.gov as NCT01292954 and NCT01829542.

  15. Wave propagation in bubble, two-component, two-phase flows. Theoretical and experimental study

    International Nuclear Information System (INIS)

    Micaelli, Jean-Claude

    1982-01-01

    This research thesis first reports the theoretical study of pressure and vacuum rate waves (of low amplitude) propagating through two-phase flows. This study is performed by using hybrid models. These models, based on assessment equations averaged for each phase, are developed by using a stochastic processing of the gas phase behaviour. This stochastic processing allows the model closure. The author highlights, in the case of vacuum rate waves, the importance of mass effects, interface friction and interface heat transfer. An experimental study is performed by using a vertical test section equipped with resistive probes and pressure sensors, and a signal processing unit (Fourier transform, inter-spectrum). Experimental results are confirmed by theoretical results, and leads to quantitative information on laws governing the interaction between phases which are necessary for model closure [fr

  16. Theoretical and experimental study of an energy-reinforced braking radiation photon beam

    International Nuclear Information System (INIS)

    Bertin, Pierre-Yves

    1966-01-01

    This research thesis reports the theoretical study of a photon beam raised towards high energies, its experimental implementation, the definition of a gamma spectrometry method which aimed at checking various hypotheses used in the beam theoretical study. After a presentation of the theory of phenomena of electron braking radiation, of materialisation of photons into positon-negaton pair, and of issues related to multiple Coulomb diffusion, the author reports the study of the different solutions which allow a photon beam to be obtained. A braking radiation of mono-kinetic electron has been used. This braking radiation is reinforced by absorption of low energy protons in a column of lithium hydride. The author describes how the beam is built up, and the experimental approach. He describes how raw data are processed to get rid of the influence of the multiple Coulomb diffusion and of the braking radiation. Experimental results are compared with those obtained by convolution of photon spectra and differential cross section

  17. Synthesis and Theoretical Study of Molecularly Imprinted Nanospheres for Recognition of Tocopherols

    Directory of Open Access Journals (Sweden)

    Chartchalerm Isarankura-Na-Ayudhya

    2009-08-01

    Full Text Available Molecular imprinting is a technology that facilitates the production of artificial receptors toward compounds of interest. The molecularly imprinted polymers act as artificial antibodies, artificial receptors, or artificial enzymes with the added benefit over their biological counterparts of being highly durable. In this study, we prepared molecularly imprinted polymers for the purpose of binding specifically to tocopherol (vitamin E and its derivative, tocopherol acetate. Binding of the imprinted polymers to the template was found to be two times greater than that of the control, non-imprinted polymers, when using only 10 mg of polymers. Optimization of the rebinding solvent indicated that ethanol-water at a molar ratio of 6:4 (v/v was the best solvent system as it enhanced the rebinding performance of the imprinted polymers toward both tocopherol and tocopherol acetate with a binding capacity of approximately 2 mg/g of polymer. Furthermore, imprinted nanospheres against tocopherol was successfully prepared by precipitation polymerization with ethanol-water at a molar ratio of 8:2 (v/v as the optimal rebinding solvent. Computer simulation was also performed to provide mechanistic insights on the binding mode of template-monomer complexes. Such polymers show high potential for industrial and medical applications, particularly for selective separation of tocopherol and derivatives.

  18. Electronic properties of diphenyl-s-tetrazine and some related oligomers. An spectroscopic and theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Moral, Monica; Garcia, Gregorio [Departamento de Quimica Fisica y Analitica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain); Penas, Antonio [Departamento de Quimica Inorganica y Organica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain); Garzon, Andres; Granadino-Roldan, Jose M. [Departamento de Quimica Fisica y Analitica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain); Melguizo, Manuel [Departamento de Quimica Inorganica y Organica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain); Fernandez-Gomez, Manuel, E-mail: mfg@ujaen.es [Departamento de Quimica Fisica y Analitica, Facultad de Ciencias Experimentales, Universidad de Jaen, Campus las Lagunillas, E23071 Jaen (Spain)

    2012-10-26

    Highlights: Black-Right-Pointing-Pointer We study properties of Ph{sub 2}Tz and (PhTz){sub n}Ph as candidates for organic electronics. Black-Right-Pointing-Pointer The synthesis of Ph{sub 2}Tz was performed through a modified Pinner-type reaction. Black-Right-Pointing-Pointer IR/Raman spectra allowed to conclude that Ph{sub 2}Tz is nearly planar in liquid phase. Black-Right-Pointing-Pointer Electronic structure was studied by UV-Vis/TD-DFT methods in different solvents. Black-Right-Pointing-Pointer Bandgap, E{sub LUMO}, electron mobility predict some n-type character for limit polymer. -- Abstract: This work presents a theoretical and spectroscopic study on the electronic and structural properties of the diphenyl-s-tetrazine molecule (Ph{sub 2}Tz) and some oligomeric derivatives. Ph{sub 2}Tz was synthesized through a variation of Pinner-type reaction which uses N-acetylcysteine as catalyst. Insight into the structure and electronic properties of the title compound was obtained through IR, Raman, UV-Vis spectra in different solvents, and theoretical calculations. Theoretical studies have been extended to different n-mers derivatives up to an ideal molecular wire through the oligomeric approximation, predicting this way electronic properties such as LUMO energy levels, electron affinity and reorganization energy in order to assess their possible applications in molecular electronics.

  19. A theoretical study of rotatable renewable energy system for stratospheric airship

    International Nuclear Information System (INIS)

    Lv, Mingyun; Li, Jun; Zhu, Weiyu; Du, Huafei; Meng, Junhui; Sun, Kangwen

    2017-01-01

    Highlights: • A new rotatable renewable energy system is designed for stratospheric airship. • A theoretical model of optimal rotation angle and required area are studied. • The effects of latitude and date on output energy per day are investigated. • The advantages of the rotatable renewable energy system are studied. - Abstract: Renewable energy system is very critical for solving the energy problem of a long endurance stratospheric airship. Output performance of the traditional solar array fixed on the upper surface of the airship remains to be improved to reduce the area and weight of renewable energy system. Inspired by the solar tracking system and kirigami, a rotatable renewable energy system (mainly including solar array) is designed to improve the current status of the energy system. The advantages of the rotatable solar array are studied using a MATLAB computer program based on the theoretical model established in this paper. The improvements in output energy and required area of the solar array were compared between the traditional airship and improved one. Studies had shown that the rotatable renewable energy system made the total weight of energy system decreased by 1000 kg when the maximum design speed of the airship was greater than 22 m/s. The results demonstrate that the rotatable renewable energy system for the airship can be a good way to improve the output performance of solar array, and the conceptual design and theoretical model suggest a pathway towards solving the energy problem of a stratospheric airship.

  20. Theoretical model simulations for the global Thermospheric Mapping Study (TMS) periods

    Science.gov (United States)

    Rees, D.; Fuller-Rowell, T. J.

    Theoretical and semiempirical models of the solar UV/EUV and of the geomagnetic driving forces affecting the terrestrial mesosphere and thermosphere have been used to generate a series of representative numerical time-dependent and global models of the thermosphere, for the range of solar and geoamgnetic activity levels which occurred during the three Thermospheric Mapping Study periods. The simulations obtained from these numerical models are compared with observations, and with the results of semiempirical models of the thermosphere. The theoretical models provide a record of the magnitude of the major driving forces which affected the thermosphere during the study periods, and a baseline against which the actual observed structure and dynamics can be compared.

  1. Generation of pulsed Bessel-Gauss beams using passive axicon-theoretical and experimental studies.

    Science.gov (United States)

    Parsa, Shahrzad; Fallah, Hamid Reza; Ramezani, Mohsen; Soltanolkotabi, Mahmood

    2012-10-20

    We studied the conditions for generating passive Bessel-Gauss beams by using an axicon. We designed an appropriate Gaussian resonator and extracted a quasi-fundamental Gaussian mode from a pulsed Nd:YAG laser pumped by a Xenon flash lamp and measured its parameters, such as propagation factor, divergence angle, and Rayleigh range. Then we generated passive Bessel-Gauss beams using an axicon and investigated their propagation properties, theoretically and experimentally. For example, for the axicon of 1°, the output energy and the Rayleigh range of the generated Bessel-Gauss beams were measured to be 58 mJ and 229.3 mm, respectively. We compared these properties with our results of the Gaussian mode. Finally, by using axicons with different apex angles, and also by changing the beam spot size on the axicon, we generated Bessel-Gauss beams and studied their properties theoretically and experimentally.

  2. RECENT DEVELOPMENTS OF THE FINANCIAL REPORTING MODEL: THEORETICAL STUDIES IN REVIEW

    OpenAIRE

    Bonaci Carmen Giorgiana; Matis Dumitru

    2011-01-01

    Our paper analyzes the manner in which the financial reporting model evolved towards fair value accounting. After a brief introduction into the context of financial reporting at international level, the analysis focuses on the accounting model of fair value. This is done by synthesizing main studies in accounting research literature that analyze fair value accounting through a theoretical approach. The analysis being developed relies on literature review methodology. The main purpose of the d...

  3. Isolation, spectroscopic characterization, X-ray, theoretical studies as well as in vitro cytotoxicity of Samarcandin

    Czech Academy of Sciences Publication Activity Database

    Ghoran, S.H.; Atabaki, V.; Babaei, E.; Olfatkhah, S.R.; Dušek, Michal; Eigner, Václav; Soltani, A.; Khalaji, A.D.

    2016-01-01

    Roč. 66, Jun (2016), s. 27-32 ISSN 0045-2068 R&D Projects: GA ČR GA15-12653S; GA MŠk LO1603 EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : cytotoxicity * NMR * sesquiterpene coumarin * theoretical study * TD-DFT * X-ray Subject RIV: CC - Organic Chemistry Impact factor: 3.231, year: 2016

  4. Theoretical studies on the α decay half-lives of hyper and normal ...

    Indian Academy of Sciences (India)

    The α decay half-lives of hyper and normal isotopes of Po nuclei are studied in the present work. The inclusion of Λ – N interaction changes the half-life for α decay. The theoretical predictions on the α decay half-lives of normal Po isotopes are compared with experimental results and are seen to be matching well with each ...

  5. Theoretical Studies of TE-Wave Propagation as a Diagnostic for Electron Cloud

    International Nuclear Information System (INIS)

    Penn, Gregory E.; Vay, Jean-Luc

    2010-01-01

    The propagation of TE waves is sensitive to the presence of an electron cloud primarily through phase shifts generated by the altered dielectric function, but can also lead to polarization changes and other effects, especially in the presence of magnetic fields. These effects are studied theoretically and also through simulations using WARP. Examples are shown related to CesrTA parameters, and used to observe different regimes of operation as well as to validate estimates of the phase shift.

  6. Theoretical and experimental study of the instabilities of air-lift pumping systems

    International Nuclear Information System (INIS)

    Cachard, Francois de

    1989-01-01

    Air-lifts are pumping systems which operate by air injection into the conduct containing the fluid to be transferred. They are notably used for corroding or radioactive liquids. Their instabilities which result in highly pulsed flows, do not comply with many applications. This research thesis reports a theoretical and experimental study which aimed at developing a numeric modelling which can be a practical tool to analyse air-lift performance and stability [fr

  7. Contribution to the theoretical study of metallic systems containing rare earths: hyperfine interactions and exchange coupling

    International Nuclear Information System (INIS)

    Troper, A.

    1978-01-01

    A theoretical study involving rare earth impurities, which were embedded in transition metals (s-p or noble), from the point of view of the hyperfine interactions is presented. A model was created to describe a d-resonance (Anderson-Moriya) acting on a s-p conduction band which was strongly perturbed by a slater-koster potential, used to describe the rare earths which were diluted in matrices of transition elements. (author)

  8. The mechanism for the rhodium-catalyzed decarbonylation of aldehydes: A combined experimental and theoretical study

    DEFF Research Database (Denmark)

    Fristrup, Peter; Kreis, Michael; Palmelund, Anders

    2008-01-01

    that similar mechanisms are operating. A DFT (B3LYP) study of the catalytic cycle indicated a rapid oxidative addition into the C(O)-H bond followed by a rate-limiting extrusion of CO and reductive elimination. The theoretical kinetic isotope effects based on this mechanism were in excellent agreement...... with the experimental values for both substrates, but only when migratory extrusion of 00 was selected as the rate-determining step....

  9. Theoretical study on ground-state proton/H-atom exchange in formic ...

    Indian Academy of Sciences (India)

    Theoretical study on ground-state proton/H-atom exchange in formic acid clusters through different H-bonded .... the pKa of the proton wire, faster is the rate of proton transfer. It is obvious that the features of the H- ..... tances in TS could be ascribed to the higher basicity (as. Table 4. Mulliken partial charges of selected atoms ...

  10. High Performance Computer Cluster for Theoretical Studies of Roaming in Chemical Reactions

    Science.gov (United States)

    2016-08-30

    High-performance Computer Cluster for Theoretical Studies of Roaming in Chemical Reactions A dedicated high-performance computer cluster was...purchased in order to carry out extensive and state-of-the art computations of chemical reaction dynamics. The specific aim of this computational research...is the detailed elucidation of the recently reported “roaming” pathway in gas-phase chemical reactions . Several complex reaction systems

  11. Annual Report 2013-2014: Theoretical Studies of Nerve Agents Adsorbed on Surfaces

    Science.gov (United States)

    2014-07-08

    Photoassisted removal of sarin vapor in air under UV light irradiation. Journal of Photochemistry and Photobiology a- Chemistry 2007, 188, 143-148...with an ester linkage to an aliphatic group. Coloring scheme as follows: C (gray), H (white), O (red), P (orange), F ( blue ). Most nerve agents act...magnesium oxide. Journal of Physical Chemistry B 2004, 108, 5294-5303. 7. Michalkova, A.; Paukku, Y .; Majumdar, D.; Leszczynski, J., Theoretical study

  12. Theoretical and Computational Studies of Rare Earth Substitutes: A Test-bed for Accelerated Materials Development

    Energy Technology Data Exchange (ETDEWEB)

    Benedict, Lorin X. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-26

    Hard permanent magnets in wide use typically involve expensive Rare Earth elements. In this effort, we investigated candidate permanent magnet materials which contain no Rare Earths, while simultaneously exploring improvements in theoretical methodology which enable the better prediction of magnetic properties relevant for the future design and optimization of permanent magnets. This included a detailed study of magnetocrystalline anisotropy energies, and the use of advanced simulation tools to better describe magnetic properties at elevated temperatures.

  13. Theoretical Studies of Gas Phase Elementary and Carbon Nanostructure Growth Reactions

    Science.gov (United States)

    2013-09-19

    photodissociation reactions of ketene, methylamine, formic acid , methyl ethyl ketone, acetone and NO3. For instance, for NO3, a totally unknown...to photodissociation reactions of ketene, methylamine, formic acid , methyl ethyl ketone, acetone and NO3. For instance, for NO3, a totally unknown...THEORETICAL STUDIES OF GAS PHASE ELEMENTARY AND CARBON NANOSTRUCTURE GROWTH REACTIONS KEIJI MOROKUMA EMORY UNIVERSITY 09/19/2013 Final Report

  14. Theoretical studies on the decay half-lives of hyper and normal ...

    Indian Academy of Sciences (India)

    K P SANTHOSH

    2018-02-10

    Feb 10, 2018 ... Abstract. The α decay half-lives of hyper and normal isotopes of Po nuclei are studied in the present work. The inclusion of –N interaction changes the half-life for α decay. The theoretical predictions on the α decay half-lives of normal Po isotopes are compared with experimental results and are seen to be ...

  15. Theoretical study of the lowest-lying electronic states of Aluminium monoiodide

    International Nuclear Information System (INIS)

    Taher, F.; Kabbani, A.; Ani-El Houte, W.

    2004-01-01

    Full text.The spectroscopic study of Aluminium monohalides, especially the Aluminium monoiodide, is important for monitoring such species in high temperature fast-flow reactors. Theoretical calculations of AlI are not available, whereas several studies have been done for the other aluminium monohalides. In this work, CAS-SCF/MRCI calculations are performed for the lowest-lying electronic states of AlI in a range of internuclear distance between 2.30 A and 2.80 A. Ab-initio calculations have been effectuated by using the computational chemistry program Molpro. The basis set used in this study for aluminium atom is that used by Langhoff for aluminium monohalides, of contractions using atomic natural orbitals and a pseudopotential is used for iode. Accurate theoretical spectroscopic constants and potential curves are obtained for the ground state X 1 Σ + and the first excited states a 3 Π and A 1 Π. The calculated values of Te, ωe, ωexe and re of these states are compatible with the experimental results. An ordering of states is represented for the lowest five predicted singlet and lowest five predicted triplet states. These results provide a big support to determine the analogy in the ordering of the electronic states in AlF, AlBr and AlI respectively at lower energies. These theoretical results identify a set of electronic singlet and triplet states unobserved experimentally

  16. Synthesis, characterization, investigation of biological activity and theoretical studies of hydrazone compounds containing choloroacetyl group

    Science.gov (United States)

    Cukurovali, Alaaddin; Yilmaz, Engin

    2014-10-01

    In this study, three new hydrazide-hydrazone derivative compounds which contain choloroacetyl group have been synthesized and characterized. In the characterization, spectral techniques such as IR, 1H NMR, 13C NMR and UV-Vis spectroscopy techniques were used. Antibacterial effects of the synthesized compounds were investigated against Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. In the theoretical calculations Gaussian 09 software was used with the DFT/6-311+(d,p) basis set. Experimental X-ray analysis of compounds has not been studied. Theoretical bond lengths of synthesized compounds were compared with experimental bond lengths of a similar compound. Theoretical and experimental bond lengths are in good agreement with R2: 0.896, 0.899 and 0.900 for compounds 1, 2, and 3, respectively. For antibacterial activity, the most effective one was found to be N‧-(4-bromobenzylidene)-2-chloro-N-(4-(3-methyl-3-phenylcyclobutyl)-thiazol-2-yl) acetohydrazide against P.aeroginaosa ATTC 27853, among the studied compounds.

  17. Characterization and Mechanistic Studies of a Novel Melanoma-Targeting Construct Containing IκBa for Specific Inhibition of Nuclear Factor-κB Activity

    Directory of Open Access Journals (Sweden)

    Hong Zhou

    2010-10-01

    Full Text Available The transcription factor nuclear factor-κB (NF-κB is a central mediator of growth and homeostasis for both normal and neoplastic cells. IκBα is the natural intracellular inhibitor of NF-κB and can effectively complex with and thereby inhibit the biologic activity and translocation of NF-κB to the nucleus. We designed a fusion protein designated IκBα/scFvMEL composing of human IκBα and the single-chain antibody scFvMEL, targets melanoma gp240 antigen. Cells treated with IκBα/scFvMEL before irradiation showed specifically inhibition of both constitutive and radiation-induced NF-κB activity on gp240 antigen-positive A375M cells. Pretreatment of A375M cells with IκBα/scFvMEL significantly sensitized melanoma cells to ionizing radiation assessed using a clonogenic survival assay. Mechanistic studies showed that IκBα/scFvMEL, when exogenously added to A375M cells, could be coimmunoprecipitated with the p65 subunit of NF-κB. IκBα/scFvMEL inhibited in a time and/or dose-dependent manner of tumor necrosis factor α- or radiation-induced NF-κB activity in vitro. IκBα/scFvMEL was also shown to specifically inhibit the translocation of the NF-κB p65 subunit to the cell nucleus and NF-κB-mediated gene transcription. Further, initial studies showed that mice bearing well-established A375M xenografts were treated (intravenously with IκBα/scFvMEL and showed a significant suppression of tumor growth. We also observed a decrease in levels of Bcl-2 and Bcl-XL signaling events downstream of NF-κB in the tumor model. These studies demonstrate for the first time that tumor cell-targeted delivery of IκBα may be beneficial for the treatment of melanoma when combined with standard anticancer therapies such as radiation.

  18. FEELINGS OF INSECURITY IN CONTEXT: THEORETICAL PERSPECTIVES FOR STUDYING FEAR OF CRIME IN LATE LIFE

    Directory of Open Access Journals (Sweden)

    Liesbeth De Donder

    2009-01-01

    Full Text Available This paper broadens theoretical perspectives on fear of crime in late life by exploring the concept against the backdrop of a changing society. Since the emergence of the first studies that address fear of crime in late life, research overemphasizes the search for related independent variables being heedless of a thorough theoretical framework. Recent researchers, however, perceive the construct of ‘fear of crime’ as an ‘umbrella’ concept, which encompasses crime related fear and more diffuse ‘feelings of insecurity’. In response to a lack of macro-theorizing, this article illuminates some of the most important characteristics and descriptions of contemporary societies that are relevant to fear of crime. It is shown that in relation to fear of crime, the macro-level of society can be conceptualized as having four important ambivalences. In conclusion, the article

  19. Spin-dependent Hall effect in degenerate semiconductors: a theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Idrish Miah, M [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)], E-mail: m.miah@griffith.edu.au

    2008-10-15

    The spin-dependent Hall (SDH) effect in degenerate semiconductors is investigated theoretically. Starting from a two-component drift-diffusion equation, an expression for SDH voltage (V{sub SDH}) is derived, and drift and diffusive contributions to V{sub SDH} are studied. For the possible enhancement of the diffusive part, degenerate and nondegenerate cases are examined. We find that due to an increase in the diffusion coefficient V{sub SDH} increases in a degenerate semiconductor, consistent with the experimental observations. The expression for V{sub SDH} is reduced in three limiting cases, namely diffusive, drift-diffusion crossover and drift, and is analysed. The results agree with those obtained in recent theoretical investigations.

  20. Theoretical and experimental study of collectrons for epithermal neutron flux in reactors

    International Nuclear Information System (INIS)

    Agu, M.N.

    1986-01-01

    A theoretical study of nuclear reactions and electric charge displacements arising in sensitivity to thermal and epithermal neutrons in collectrons allowed a computer code conception. Collectrons in Rhodium, Silver, Cobalt, Hafnium, Erbium, Gadolinium and Holmium have been tested in different radiation fields given by neutron or gamma filters irradiated in different places of Melusine and Siloe reactors. Some emitters were covered with different steel, nickel or zircaloy thicknesses. Theoretical and experimental results are consistent; that validate the computer code and show possibilities and necessity of covering collectron emitters to reduce or cancel the gamma sensitivity and to improve response instantaneity. A selective measurement of epithermal neutron flux can by this way, made by associating two types of collectrons [fr