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Sample records for study fragmentation reactions

  1. Studies of complex fragment emission in heavy ion reactions

    SciTech Connect

    Charity, R.J.; Sobotka, L.G.

    1992-01-01

    Our work involves the study of intermediate energy heavy-ion nuclear reactions. This work has two foci. On the one hand, we desire to learn about the properties of nuclear matter under abnormal conditions, in this energy domain, predominately low densities. This purpose runs abreast of the second, which is the study of the relevant reaction mechanisms. The two objectives are inexorably linked because our experimental laboratory for studying nuclear matter properties is a dynamic one. We are forced to ask how nuclear matter properties, such as phase transitions, are reflected in the dynamics of the reactions. It may be that irrefutable information about nuclear matter will not be extracted from the reaction work. Nevertheless, we are compelled to undertake this effort not only because it is the only game in town and as yet we do not know that information cannot be extracted, but also because of our second objective. The process leads to an understanding of the reaction mechanism themselves and therefore to the response characteristics of finite, perhaps non-equilibrium, strongly interacting systems. Our program has been: To study energy, mass, and angular momentum deposition by studying incomplete fusion reactions. To gain confidence that we understand how highly excited systems decompose by studying all emissions from the highly excited systems. To push these kinds of studies into the intermediate energy domain, with excitation function studies. And attempt to learn about the dynamics of the decays using particle-particle correlations. In the last effort, we have decided to focus on simple systems, where we believe, definitive statements are possible. These avenues of research share a common theme, large complex fragment production.

  2. Isobaric Analogue States Studied in Mirrored Fragmentation and Knockout Reactions

    SciTech Connect

    Bentley, M.A.; Pritychenko, B.; Paterson,I.; Brown,J.R.; Taylor,M.J.; Digen,C.Aa.; Adrich,P.; Bazin,D.; Cook.J.M.; Gade,A.; Glasmacher,T.; McDaniel,S.; Ratkiewicz,A.; Siwek,K.; D.Weisshaar,D.; Pritychenko,B.; Lenzi,S.M.

    2010-05-21

    A Gamma-ray spectroscopic study of excited states of isobaric multiplets has been performed in recent years, with a view to gaining a quantitative understanding of energy differences between excited states in terms of a range of Coulomb and other isospin breaking phenomena. Recently, the experimental programme has been augmented by a study of isobaric analogue states of mirror nuclei populated in mirrored fragmentation reactions. In this presentation, recent results on the T = 3/2 analogue states in the T{sub z} = {+-} 3/2 mirror pair {sup 53}Ni/{sup 53}Mn will be summarised. In this work, further strong evidence is found for the need to include an anomalous isospin-breaking two-body matrix element for angular-momentum couplings of J = 2, in addition the expected Coulomb contribution, in order to account for the experimental data.

  3. Application of isochronous mass spectrometry for the study of angular momentum population in projectile fragmentation reactions

    NASA Astrophysics Data System (ADS)

    Tu, X. L.; Kelić-Heil, A.; Litvinov, Yu. A.; Podolyák, Zs.; Zhang, Y. H.; Huang, W. J.; Xu, H. S.; Blaum, K.; Bosch, F.; Chen, R. J.; Chen, X. C.; Fu, C. Y.; Gao, B. S.; Ge, Z.; Hu, Z. G.; Liu, D. W.; Litvinov, S. A.; Ma, X. W.; Mao, R. S.; Mei, B.; Shuai, P.; Sun, B. H.; Sun, Y.; Sun, Z. Y.; Walker, P. M.; Wang, M.; Winckler, N.; Xia, J. W.; Xiao, G. Q.; Xing, Y. M.; Xu, X.; Yamaguchi, T.; Yan, X. L.; Yang, J. C.; Yuan, Y. J.; Zeng, Q.; Zhang, W.; Zhao, H. W.; Zhao, T. C.; Zhou, X. H.

    2017-01-01

    Isochronous mass spectrometry was applied to measure isomeric yield ratios of fragmentation reaction products. This approach is complementary to conventional γ -ray spectroscopy in particular for measuring yield ratios for long-lived isomeric states. Isomeric yield ratios for the high-spin I =19 /2 ℏ states in the mirror nuclei 53Fe and 53Co are measured to study angular momentum population following the projectile fragmentation of 78Kr at energies of ˜480 A MeV on a beryllium target. The 19/2 state isomeric ratios of 53Fe produced from different projectiles in the literature have also been extracted as a function of mass number difference between projectile and fragment (mass loss). The results are compared to abrabla07 model calculations. The isomeric ratios of 53Fe produced using different projectiles suggest that the theory underestimates not only the previously reported dependence on the spin but also the dependence on the mass loss.

  4. Theoretical Study of Projectile Fragmentations in Relativistic Heavy-Ion Reactions

    NASA Astrophysics Data System (ADS)

    Ogul, R.; Imal, H.; Ergun, A.; Buyukcizmeci, N.; Botvina, A. S.; Trautmann, W.

    2015-05-01

    We have investigated and interpreted the production cross sections and isotopic distributions of projectile-like residues in the reactions 124Sn + 124Sn and 112Sn + 112Sn at an incident beam energy of 1 GeV/nucleon measured with the FRS fragment separator at the GSI laboratory. For the interpretation of the data, calculations within the statistical multifragmentation model (SMM) for an ensemble of excited sources were performed with ensemble parameters. The possible modification of symmetry energy parameter, in the multifragmentation region at the low density and hot freeze-out environment, is studied. It is reconfirmed that a significant reduction of the symmetry energy term is found necessary to reproduce experimental results at these conditions. We have also found a decreasing trend of the symmetry energy for large neutron-rich fragments of low excitation energy which is interpreted as a nuclear-structure effect.

  5. Collision induced dissociation study of ester-based polyurethane fragmentation reactions.

    PubMed

    Gies, Anthony P; Hercules, David M

    2014-01-15

    A combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) collision induced dissociation (CID) and ion mobility separations (IMS) was used to study a complex mixture composed of unreacted polyester starting material (polybutylene adipate) and polyurethane (PUR) end products. Collision induced dissociation fragmentation identified two primary fragmentation mechanisms of PURs, which were used to generate a general fragmentation model. Predicted fragment ions were used to distinguish: (1) linear and cyclic PURs, (2) hard-block and soft-block PURS, (3) the degree of "blockiness" within hard- and soft-block PURs, (4) the location of the MDI linkages within each PUR chain, and (5) the relative intensities of various isobars intermingled within a precursor mass peak. These results were consistent with the observed IMS separations.

  6. A study to control chemical reactions using Si:2p core ionization: site-specific fragmentation.

    PubMed

    Nagaoka, Shin-ichi; Fukuzawa, Hironobu; Prümper, Georg; Takemoto, Mai; Takahashi, Osamu; Yamaguchi, Katsuhiro; Kakiuchi, Takuhiro; Tabayashi, Kiyohiko; Suzuki, Isao H; Harries, James R; Tamenori, Yusuke; Ueda, Kiyoshi

    2011-08-18

    In an aim to create a "sharp" molecular knife, we have studied site-specific fragmentation caused by Si:2p core photoionization of bridged trihalosilyltrimethylsilyl molecules in the vapor phase. Highly site-specific bond dissociation has been found to occur around the core-ionized Si site in some of the molecules studied. The site specificity in fragmentation and the 2p binding energy difference between the two Si sites depend in similar ways on the intersite bridge and the electronegativities of the included halogen atoms. The present experimental and computational results show that for efficient "cutting" the following conditions for the two atomic sites to be separated by the knife should be satisfied. First, the sites should be located far from each other and connected by a chain of saturated bonds so that intersite electron migration can be reduced. Second, the chemical environments of the atomic sites should be as different as possible.

  7. Studies of complex fragment emission in heavy ion reactions. Progress report, January 1, 1993--September 15, 1993

    SciTech Connect

    Charity, R.J.; Sobotka, L.G.

    1993-09-12

    The study of intermediate-energy heavy-ion nuclear reactions is reported. This work has two foci: the properties of nuclear matter under abnormal conditions, in this energy domain, predominately low densities and the study of the relevant reaction mechanisms. Nuclear matter properties, such as phase transitions, are reflected in the dynamics of the reactions. The process leads to an understanding of the reaction mechanism themselves and therefore to the response characteristics of finite, perhaps non-equilibrium, strongly interacting systems. The program has the following objectives: to study energy, mass, and angular momentum deposition by studying incomplete fusion reactions; to gain confidence in the understanding of how highly excited systems decompose by studying all emissions from the highly excited systems; to push these kinds of studies into the intermediate energy domain (where intermediate mass fragment emission is not improbable) with excitation function studies; and to learn about the dynamics of the decays using particle-particle correlations. The last effort focuses on simple systems, where definitive statements are possible. These avenues of research share a common theme, large complex fragment production. It is this feature, more than any other, which distinguishes the intermediate energy domain.

  8. Study on Fragments Emission in the 64Ni + 64Ni Reaction at 40 AMeV

    NASA Astrophysics Data System (ADS)

    Yang, Kun; Cao, Xiguang; Shi, Fudong; Liu, Xingquan; Zhang, Suyalatu; Huang, Meirong; Wang, Jiansong; Chen, Zhiqiang; Wada, R.; Kowalski, S.; Keutgen, T.; Hagel, K.; Bonasera, A.; B. Natowitz, J.; Materna, T.; L., Qin; K. Sahu, P.

    2012-05-01

    The multiplicity of fragments in Fermi energy heavy-ion collisions was experimentally extracted. Compared with the results of calculation using the antisymmetrized molecular dynamics (AMD) model which accounts for the primary fragments only, the results calculated using the AMD together with a statistical decay code GEMINI to account for the deexcitation of excited primary fragments are in better agreement with those extracted from the experiment. This observation indicates that the experimental multiplicity distribution may be significantly different from those of primary fragments.

  9. Studies of complex fragment emission in heavy ion reactions. Progress report, January 1, 1990--August 5, 1992

    SciTech Connect

    Charity, R.J.; Sobotka, L.G.

    1992-09-01

    Our work involves the study of intermediate energy heavy-ion nuclear reactions. This work has two foci. On the one hand, we desire to learn about the properties of nuclear matter under abnormal conditions, in this energy domain, predominately low densities. This purpose runs abreast of the second, which is the study of the relevant reaction mechanisms. The two objectives are inexorably linked because our experimental laboratory for studying nuclear matter properties is a dynamic one. We are forced to ask how nuclear matter properties, such as phase transitions, are reflected in the dynamics of the reactions. It may be that irrefutable information about nuclear matter will not be extracted from the reaction work. Nevertheless, we are compelled to undertake this effort not only because it is the only game in town and as yet we do not know that information cannot be extracted, but also because of our second objective. The process leads to an understanding of the reaction mechanism themselves and therefore to the response characteristics of finite, perhaps non-equilibrium, strongly interacting systems. Our program has been: To study energy, mass, and angular momentum deposition by studying incomplete fusion reactions. To gain confidence that we understand how highly excited systems decompose by studying all emissions from the highly excited systems. To push these kinds of studies into the intermediate energy domain, with excitation function studies. And attempt to learn about the dynamics of the decays using particle-particle correlations. In the last effort, we have decided to focus on simple systems, where we believe, definitive statements are possible. These avenues of research share a common theme, large complex fragment production.

  10. Fragmentation reactions of deprotonated peptides containing aspartic acid

    NASA Astrophysics Data System (ADS)

    Harrison, Alex G.; Young, Alex B.

    2006-09-01

    The fragmentation reactions of deprotonated peptides containing aspartic acid have been elucidated using MS2 and MS3 experiments and accurate mass measurements where necessary. The disposition of labile (N and O bonded) hydrogens in the fragmentation products has been studied by exchanging the labile hydrogens for deuterium whereby the [MD]- ion is formed on electrospray ionization. [alpha]-Aspartyl and [beta]-aspartyl dipeptides give very similar fragment ion spectra on collisional activation, involving for both species primarily formation of the y1 ion and loss of H2O from [MH]- followed by further fragmentation, thus precluding the distinction of the isomeric species by negative ion tandem mass spectrometry. Dipeptides of sequence HXxxAspOH give characteristic spectra different from the [alpha]- and [beta]-isomers. For larger peptides containing aspartic acid a common fragmentation reaction involves nominal cleavage of the NC bond N-terminal to the aspartic acid residue to form a c ion (deprotonated amino acid amide (c1) or peptide amide (cn)) and the complimentary product involving elimination of a neutral amino acid amide or peptide amide. When aspartic acid is in the C-terminal position this fragmentation reaction occurs from the [MH]- ion while when the aspartic acid is not in the C-terminal position the fragmentation reaction occurs mainly from the [MHH2O]- ion. The products of this NC bond cleavage reaction serve to identify the position of the aspartic acid residue in the peptide.

  11. Theoretical Study of the Reaction Formalhydrazone with Singlet Oxygen. Fragmentation of the C=N Bond, Ene Reaction, and Other Processes†

    PubMed Central

    Rudshteyn, Benjamin; Castillo, Álvaro; Ghogare, Ashwini A.; Liebman, Joel F.; Greer, Alexander

    2013-01-01

    Photobiologic and synthetic versatility of hydrazones has not yet been established with 1O2 as a route to commonly encountered nitrosamines. Thus, to determine whether the “parent” reaction of formalhydrazone and 1O2 leads to facile C=N bond cleavage and resulting nitrosamine formation, we have carried out CCSD(T)//DFT calculations and analyzed the energetics of the oxidation pathways. A [2 + 2] pathway occurs via diradicals and formation of 3-amino-1,2,3-dioxazetidine in a 16 kcal/mol process. Reversible addition or physical quenching of 1O2 occurs either on the formalhydrazone carbon for triplet diradicals at 2–3 kcal/mol, or on the nitrogen (N(3)) atom forming zwitterions at ~15 kcal/mol, although the quenching channel by charge-transfer interaction was not computed. The computations also predict a facile conversion of formalhydrazone and 1O2 to hydroperoxymethyl diazene in a low-barrier ‘ene’ process, but no 2-amino-oxaziridine-O-oxide (perepoxide-like) intermediate was found. A Benson-like analysis (group increment calculations) on the closed shell species are in accord with the quantum chemical results. PMID:24354600

  12. Cloning of DNA fragments: ligation reactions in agarose gel.

    PubMed

    Furtado, Agnelo

    2014-01-01

    Ligation reactions to ligate a desired DNA fragment into a vector can be challenging to beginners and especially if the amount of the insert is limiting. Although additives known as crowding agents, such as PEG 8000, added to the ligation mixes can increase the success one has with ligation reactions, in practice the amount of insert used in the ligation can determine the success or the failure of the ligation reaction. The method described here, which uses insert DNA in gel slice added directly into the ligation reaction, has two benefits: (a) using agarose as the crowding agent and (b) reducing steps of insert purification. The use of rapid ligation buffer and incubation of the ligation reaction at room temperature greatly increase the efficiency of the ligation reaction even for blunt-ended ligation.

  13. Structural Studies of Geosmin Synthase, a Bifunctional Sesquiterpene Synthase with αα Domain Architecture That Catalyzes a Unique Cyclization-Fragmentation Reaction Sequence.

    PubMed

    Harris, Golda G; Lombardi, Patrick M; Pemberton, Travis A; Matsui, Tsutomu; Weiss, Thomas M; Cole, Kathryn E; Köksal, Mustafa; Murphy, Frank V; Vedula, L Sangeetha; Chou, Wayne K W; Cane, David E; Christianson, David W

    2015-12-08

    Geosmin synthase from Streptomyces coelicolor (ScGS) catalyzes an unusual, metal-dependent terpenoid cyclization and fragmentation reaction sequence. Two distinct active sites are required for catalysis: the N-terminal domain catalyzes the ionization and cyclization of farnesyl diphosphate to form germacradienol and inorganic pyrophosphate (PPi), and the C-terminal domain catalyzes the protonation, cyclization, and fragmentation of germacradienol to form geosmin and acetone through a retro-Prins reaction. A unique αα domain architecture is predicted for ScGS based on amino acid sequence: each domain contains the metal-binding motifs typical of a class I terpenoid cyclase, and each domain requires Mg(2+) for catalysis. Here, we report the X-ray crystal structure of the unliganded N-terminal domain of ScGS and the structure of its complex with three Mg(2+) ions and alendronate. These structures highlight conformational changes required for active site closure and catalysis. Although neither full-length ScGS nor constructs of the C-terminal domain could be crystallized, homology models of the C-terminal domain were constructed on the basis of ∼36% sequence identity with the N-terminal domain. Small-angle X-ray scattering experiments yield low-resolution molecular envelopes into which the N-terminal domain crystal structure and the C-terminal domain homology model were fit, suggesting possible αα domain architectures as frameworks for bifunctional catalysis.

  14. Structural Studies of Geosmin Synthase, a Bifunctional Sesquiterpene Synthase with Alpha-Alpha Domain Architecture that Catalyzes a Unique Cyclization-Fragmentation Reaction Sequence

    PubMed Central

    Harris, Golda G.; Lombardi, Patrick M.; Pemberton, Travis A.; Matsui, Tsutomu; Weiss, Thomas M.; Cole, Kathryn E.; Köksal, Mustafa; Murphy, Frank V.; Vedula, L. Sangeetha; Chou, Wayne K.W.; Cane, David E.; Christianson, David W.

    2015-01-01

    Geosmin synthase from Streptomyces coelicolor (ScGS) catalyzes an unusual, metal-dependent terpenoid cyclization and fragmentation reaction sequence. Two distinct active sites are required for catalysis: the N-terminal domain catalyzes the ionization and cyclization of farnesyl diphosphate to form germacradienol and inorganic pyrophosphate (PPi), and the C-terminal domain catalyzes the protonation, cyclization, and fragmentation of germacradienol to form geosmin and acetone through a retro-Prins reaction. A unique αα domain architecture is predicted for ScGS based on amino acid sequence: each domain contains the metal-binding motifs typical of a class I terpenoid cyclase, and each domain requires Mg2+ for catalysis. Here, we report the X-ray crystal structure of the unliganded N-terminal domain of ScGS and the structure of its complex with 3 Mg2+ ions and alendronate. These structures highlight conformational changes required for active site closure and catalysis. Although neither full-length ScGS nor constructs of the C-terminal domain could be crystallized, homology models of the C-terminal domain were constructed based on ~36% sequence identity with the N-terminal domain. Small-angle X-ray scattering experiments yield low resolution molecular envelopes into which the N-terminal domain crystal structure and the C-terminal domain homology model were fit, suggesting possible αα domain architectures as frameworks for bifunctional catalysis. PMID:26598179

  15. Dissertation: Precompound Emission of Energetic Light Fragments in Spallation Reactions

    SciTech Connect

    Kerby, Leslie Marie

    2015-08-04

    Emission of light fragments (LF) from nuclear reactions is an open question. Different reaction mechanisms contribute to their production; the relative roles of each, and how they change with incident energy, mass number of the target, and the type and emission energy of the fragments is not completely understood. None of the available models are able to accurately predict emission of LF from arbitrary reactions. However, the ability to describe production of LF (especially at energies ≳ 30 MeV) from many reactions is important for different applications, such as cosmic-ray-induced Single Event Upsets (SEUs), radiation protection, and cancer therapy with proton and heavy-ion beams, to name just a few. The Cascade-Exciton Model (CEM) version 03.03 and the Los Alamos version of the Quark-Gluon String Model (LAQGSM) version 03.03 event generators in Monte Carlo N-Particle Transport Code version 6 (MCNP6) describe quite well the spectra of fragments with sizes up to ⁴He across a broad range of target masses and incident energies (up to ~ 5 GeV for CEM and up to ~ 1 TeV/A for LAQGSM). However, they do not predict the high energy tails of LF spectra heavier than ⁴He well. Most LF with energies above several tens of MeV are emitted during the precompound stage of a reaction. The current versions of the CEM and LAQGSM event generators do not account for precompound emission of LF larger than ⁴He. The aim of our work is to extend the precompound model in them to include such processes, leading to an increase of predictive power of LF-production in MCNP6. This entails upgrading the Modified Exciton Model currently used at the preequilibrium stage in CEM and LAQGSM. It also includes expansion and examination of the coalescence and Fermi break-up models used in the precompound stages of spallation reactions within CEM and LAQGSM. Extending our models to include emission of fragments heavier than ⁴He at the precompound stage has indeed provided results that have much

  16. A population genetics study of Anopheles darlingi (Diptera: Culicidae) from Colombia based on random amplified polymorphic DNA-polymerase chain reaction and amplified fragment lenght polymorphism markers.

    PubMed

    González, Ranulfo; Wilkerson, Richard; Suárez, Marco Fidel; García, Felipe; Gallego, Gerardo; Cárdenas, Heiber; Posso, Carmen Elisa; Duque, Myriam Cristina

    2007-06-01

    The genetic variation and population structure of three populations of Anopheles darlingi from Colombia were studied using random amplified polymorphic markers (RAPDs) and amplified fragment length polymorphism markers (AFLPs). Six RAPD primers produced 46 polymorphic fragments, while two AFLP primer combinations produced 197 polymorphic fragments from 71 DNA samples. Both of the evaluated genetic markers showed the presence of gene flow, suggesting that Colombian An. darlingi populations are in panmixia. Average genetic diversity, estimated from observed heterozygosity, was 0.374 (RAPD) and 0.309 (AFLP). RAPD and AFLP markers showed little evidence of geographic separation between eastern and western populations; however, the F ST values showed high gene flow between the two western populations (RAPD: F ST = 0.029; Nm: 8.5; AFLP: F ST = 0.051; Nm: 4.7). According to molecular variance analysis (AMOVA), the genetic distance between populations was significant (RAPD:phiST = 0.084; AFLP:phiST = 0.229, P < 0.001). The F ST distances and AMOVAs using AFLP loci support the differentiation of the Guyana biogeographic province population from those of the Chocó-Magdalena. In this last region, Chocó and Córdoba populations showed the highest genetic flow.

  17. Proton Mobility in b2 Ion Formation and Fragmentation Reactions of Histidine-Containing Peptides

    NASA Astrophysics Data System (ADS)

    Nelson, Carissa R.; Abutokaikah, Maha T.; Harrison, Alex G.; Bythell, Benjamin J.

    2016-03-01

    A detailed energy-resolved study of the fragmentation reactions of protonated histidine-containing peptides and their b2 ions has been undertaken. Density functional theory calculations were utilized to predict how the fragmentation reactions occur so that we might discern why the mass spectra demonstrated particular energy dependencies. We compare our results to the current literature and to synthetic b2 ion standards. We show that the position of the His residue does affect the identity of the subsequent b2 ion (diketopiperazine versus oxazolone versus lactam) and that energy-resolved CID can distinguish these isomeric products based on their fragmentation energetics. The histidine side chain facilitates every major transformation except trans-cis isomerization of the first amide bond, a necessary prerequisite to diketopiperazine b2 ion formation. Despite this lack of catalyzation, trans-cis isomerization is predicted to be facile. Concomitantly, the subsequent amide bond cleavage reaction is rate-limiting.

  18. Scaling phenomena of isobaric yields in projectile fragmentation, spallation, and fission reactions

    NASA Astrophysics Data System (ADS)

    Ma, Chun-Wang; Huang, Ling; Song, Yi-Dan

    2017-02-01

    Background: The isobaric ratio difference scaling phenomenon, which has been found for the fragments produced in projectile fragmentation reactions, is related to the nuclear density change in reaction systems. Purpose: To verify whether the isobaric ratio difference scaling exists in the fragments produced in the spallation and fission reactions. Methods: The isobaric ratio difference scaling, denoted by SΔ lnR21 , is in theory deduced within the framework of the canonical ensemble theory at the grand-canonical limitation. The fragments measured in a series of projectile fragmentation, spallation, and fission reactions have been analyzed. Results: A good SΔ lnR21 scaling phenomenon is shown for the fragments produced both in the projectile fragmentation reactions and in the spallation reactions, whereas the SΔ lnR21 scaling phenomenon for the fragments in the fission reaction is less obvious. Conclusions: The SΔ lnR21 scaling is used to probe the properties of the equilibrium system at the time of fragment formation. The good scaling of SΔ lnR21 suggests that the equilibrium state can be achieved in the projectile fragmentation and spallation reactions. Whereas in the fission reaction, the result of SΔ lnR21 indicates that the equilibrium of the system is hard to achieve.

  19. Mirrored Fragmentation Reactions--A New Technique for Probing Isospin Symmetry in Exotic Nuclei

    SciTech Connect

    Brown, J. R.; Bentley, M. A.; Taylor, M. J.; Aldrich, P.; Bazin, D.; Cook, J. M.; Diget, C. A.; Gade, A.; Glasmacher, T.; McDaniel, S. M.; Ratkiewicz, A.; Siwek, K.; Weisshaar, D.; Pritychenko, B.

    2008-05-12

    Gamma decays have been observed for the first time in the T{sub z} = -3/2 nucleus {sup 53}Ni. This represents the first gamma-spectroscopy of a T{sub z} = -3/2 nucleus heavier than A = 33. The nucleus was produced via a two-step fragmentation process, along with its mirror {sup 53}Mn. Differences in excitation energy between isobaric analogue states have been calculated and a preliminary interpretation attempted; shell model calculations are required to further understand these results. This work represents the first study of isobaric analogue states via mirrored fragmentation reactions and demonstrates the power of this new technique.

  20. Comparing the gas-phase fragmentation reactions of protonated and radical cations of the tripeptides GXR

    NASA Astrophysics Data System (ADS)

    Wee, Sheena; O'Hair, Richard A. J.; McFadyen, W. David

    2004-05-01

    Electrospray ionization (ESI) mass spectrometry of methanolic solutions of mixtures of the copper salt (2,2':6',2''-terpyridine)copper(II) nitrate monohydrate ([Cu(II)(tpy)(NO3)2].H2O) and a tripeptide GXR (where X = 1 of the 20 naturally occurring amino acids) yielded [Cu(II)(tpy)(GXR)][radical sign]2+ ions, which were then subjected to collision induced dissociation (CID). In all but one case (GRR), these [Cu(II)(tpy)(GXR)][radical sign]2+ ions fragment to form odd electron GXR[radical sign]+ radical cations with sufficient abundance to examine their gas-phase fragmentation reactions. The GXR[radical sign]+ radical cations undergo a diverse range of fragmentation reactions which depend on the nature of the side chain of X. Many of these reactions can be rationalized as arising from the intermediacy of isomeric distonic ions in which the charge (i.e. proton) is sequestered by the highly basic arginine side chain and the radical site is located at various positions on the tripeptide including the peptide back bone and side chains. The radical sites in these distonic ions often direct the fragmentation reactions via the expulsion of small radicals (to yield even electron ions) or small neutrals (to form radical cations). Both classes of reaction can yield useful structural information, allowing for example, distinction between leucine and isoleucine residues. The gas-phase fragmentation reactions of the GXR[radical sign]+ radical cations are also compared to their even electron [GXR+H]+ and [GXR+2H]2+ counterparts. The [GXR+H]+ ions give fewer sequence ions and more small molecule losses while the [GXR+2H]2+ ions yield more sequence information, consistent with the [`]mobile proton model' described in previous studies. In general, all three classes of ions give complementary structural information, but the GXR[radical sign]+ radical cations exhibit a more diverse loss of small species (radicals and neutrals). Finally, links between these gas-phase results and key

  1. Radiation induced redox reactions and fragmentation of constituent ions in ionic liquids. 1. Anions.

    PubMed

    Shkrob, Ilya A; Marin, Timothy W; Chemerisov, Sergey D; Wishart, James F

    2011-04-14

    Room temperature ionic liquids (IL) find increasing use for the replacement of organic solvents in practical applications, including their use in solar cells and electrolytes for metal deposition, and as extraction solvents for the reprocessing of spent nuclear fuel. The radiation stability of ILs is an important concern for some of these applications, as previous studies suggested extensive fragmentation of the constituent ions upon irradiation. In the present study, electron paramagnetic resonance (EPR) spectroscopy has been used to identify fragmentation pathways for constituent anions in ammonium, phosphonium, and imidazolium ILs. Many of these detrimental reactions are initiated by radiation-induced redox processes involving these anions. Scission of the oxidized anions is the main fragmentation pathway for the majority of the practically important anions; (internal) proton transfer involving the aliphatic arms of these anions is a competing reaction. For perfluorinated anions, fluoride loss following dissociative electron attachment to the anion can be even more prominent than this oxidative fragmentation. Bond scission in the anion was also observed for NO(3)(-) and B(CN)(4)(-) anions and indirectly implicated for BF(4)(-) and PF(6)(-) anions. Among small anions, CF(3)SO(3)(-) and N(CN)(2)(-) are the most stable. Among larger anions, the derivatives of benzoate and imide anions were found to be relatively stable. This stability is due to suppression of the oxidative fragmentation. For benzoates, this is a consequence of the extensive sharing of unpaired electron density by the π-system in the corresponding neutral radical; for the imides, this stability could be the consequence of N-N σ(2)σ(*1) bond formation involving the parent anion. While fragmentation does not occur for these "exceptional" anions, H atom addition and electron attachment are prominent. Among the typically used constituent anions, aliphatic carboxylates were found to be the least

  2. Radiation induced redox reactions and fragmentation of constituent ions in ionic liquids. I. Anions.

    SciTech Connect

    Shkrob, I. A.; Marin, T.; Chemerisov, S.; Wishart, J.

    2011-04-14

    Room temperature ionic liquids (IL) find increasing use for the replacement of organic solvents in practical applications, including their use in solar cells and electrolytes for metal deposition, and as extraction solvents for the reprocessing of spent nuclear fuel. The radiation stability of ILs is an important concern for some of these applications, as previous studies suggested extensive fragmentation of the constituent ions upon irradiation. In the present study, electron paramagnetic resonance (EPR) spectroscopy has been used to identify fragmentation pathways for constituent anions in ammonium, phosphonium, and imidazolium ILs. Many of these detrimental reactions are initiated by radiation-induced redox processes involving these anions. Scission of the oxidized anions is the main fragmentation pathway for the majority of the practically important anions; (internal) proton transfer involving the aliphatic arms of these anions is a competing reaction. For perfluorinated anions, fluoride loss following dissociative electron attachment to the anion can be even more prominent than this oxidative fragmentation. Bond scission in the anion was also observed for NO{sub 3}{sup -} and B(CN){sub 4}{sup -} anions and indirectly implicated for BF{sub 4}{sup -} and PF{sub 6}{sup -} anions. Among small anions, CF{sub 3}SO{sub 3}{sup -} and N(CN){sub 2}{sup -} are the most stable. Among larger anions, the derivatives of benzoate and imide anions were found to be relatively stable. This stability is due to suppression of the oxidative fragmentation. For benzoates, this is a consequence of the extensive sharing of unpaired electron density by the {pi}-system in the corresponding neutral radical; for the imides, this stability could be the consequence of N-N {sigma}{sup 2}{sigma}*{sup 1} bond formation involving the parent anion. While fragmentation does not occur for these 'exceptional' anions, H atom addition and electron attachment are prominent. Among the typically used

  3. Sugar fragmentation in the maillard reaction cascade: isotope labeling studies on the formation of acetic acid by a hydrolytic beta-dicarbonyl cleavage mechanism.

    PubMed

    Davídek, Tomas; Devaud, Stéphanie; Robert, Fabien; Blank, Imre

    2006-09-06

    The formation of acetic acid was elucidated based on volatile reaction products and related nonvolatile key intermediates. The origin and yield of acetic acid were determined under well-controlled conditions (90-120 degrees C, pH 6-8). Experiments with various 13C-labeled glucose isotopomers in the presence of glycine revealed all six carbon atoms being incorporated into acetic acid: C-1/C-2 ( approximately 70%), C-3/C-4 ( approximately 10%), and C-5/C-6 (approximately 20%). Acetic acid is a good marker of the 2,3-enolization pathway since it is almost exclusively formed from 1-deoxy-2,3-diulose intermediates. Depending on the pH, the acetic acid conversion yield reached 85 mol % when using 1-deoxy-2,3-hexodiulose (1) as a precursor. Hydrolytic beta-dicarbonyl cleavage of 1-deoxy-2,4-hexodiuloses was shown to be the major pathway leading to acetic acid from glucose without the intermediacy of any oxidizing agents. The presence of key intermediates was corroborated for the first time, i.e., tetroses and 2-hydroxy-3-oxobutanal, a tautomer of 1-hydroxy-2,3-butanedione, also referred to as 1-deoxy-2,3-tetrodiulose. The hydrolytic beta-dicarbonyl cleavage represents a general pathway to organic acids, which corresponds to an acyloin cleavage or a retro-Claisen type reaction. Although alternative mechanisms must exist, the frequently reported hydrolytic alpha-dicarbonyl cleavage of 1 can be ruled out as a pathway forming carboxylic acids.

  4. Fission fragment mass distributions in 35Cl+Sm,154144 reactions

    NASA Astrophysics Data System (ADS)

    Tripathi, R.; Sodaye, S.; Sudarshan, K.; Nayak, B. K.; Jhingan, A.; Pujari, P. K.; Mahata, K.; Santra, S.; Saxena, A.; Mirgule, E. T.; Thomas, R. G.

    2015-08-01

    Background: A new type of asymmetric fission was observed in β -delayed fission of 180Tl [Phys. Rev. Lett. 105, 252502 (2010), 10.1103/PhysRevLett.105.252502] as symmetric mass distribution would be expected based on conventional shell effects leading to the formation of N =50 fragments. Following this observation, theoretical calculations were carried out which predict asymmetric mass distribution for several mercury isotopes around mass region of ˜180 at low and moderate excitation energies [Moller, Randrup, and Sierk, Phys. Rev. C 85, 024306 (2012), 10.1103/PhysRevC.85.024306; Andreev, Adamian, and Antonenko, Phys. Rev. C 86, 044315 (2012), 10.1103/PhysRevC.86.044315]. Studies on fission fragment mass distribution are required in this mass region to investigate this newly observed phenomenon. Purpose: The fission fragment mass distributions have been measured in 35Cl+Sm,154144 reactions at Elab=152.5 ,156.1 ,and 163.7 MeV populating compound nuclei in the mass region of ˜180 with variable excitation energy and neutron number to investigate the nature of mass distribution. Method: The fission fragment mass distribution has been obtained by measuring the "time of flight (TOF)" of fragments with respect to the beam pulse using two multiwire proportional counters placed at θlab=±65 .5∘ with respect to the beam direction. From the TOF of fragments, their velocities were determined, which were used to obtain mass distribution taking the compound nucleus as the fissioning system. Results: For both systems, mass distributions, although, appear to be symmetric, could not be fitted well by a single Gaussian. The deviation from a single Gaussian fit is more pronounced for the 35Cl+144Sm reaction. A clear flat top mass distribution has been observed for the 35Cl+144Sm reaction at the lowest beam energy. The mass distribution is very similar to that observed in the 40Ca+142Nd reaction, which populated a similar compound nucleus, but for the pronounced dip in the

  5. DFT STUDIES OF DP-3 AMYLOSE FRAGMENTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study extends our work on mono- and disaccharides to structures with three glucose residues by two alpha-[1-4] bridges, denoted herein as DP-3's. DFT optimization studies of DP-3 fragments have been carried out at the B3LYP/6-311++G** level of theory. Different hydroxymethyl conformations (gg...

  6. Polymerization behavior of Klenow fragment and Taq DNA polymerase in short primer extension reactions.

    PubMed

    Zhao, Guojie; Guan, Yifu

    2010-10-01

    DNA polymerases amplify DNA fragments through primer extension reactions. However, polymerization behavior of short primers in the primer extension process has not been systematically explored. In this study, we examined the minimal primer length required for primer extension, and the effect of primer length, mismatches and other conditions on DNA polymerization using a non-radioactive method. Under the condition we conducted, the shortest primers polymerized by Klenow fragment (KF) and Taq DNA polymerase in our experiments were respectively heptamer and octamer. The extension efficiency was also affected by the up-stream overhanging structure of the primer-template complex. We hypothesized a simple model to interpret these observations based on the polymerase structures. Furthermore, it was found that the longer the primer, the more efficient is the primer extension. These polymerization behavior of short primers lay foundation about DNA polymerization mechanism and development of novel nucleic acid detection assays.

  7. A Population Genetics Study of Anopheles Darlingi (Diptera: Culicidae) from Colombia Based on Random Amplified Polymorphic DNA-Polymerase Chain Reaction and Amplified Fragment Length Polymorphism Markers

    DTIC Science & Technology

    2007-06-01

    0.029; Nm: 8.5; AFLP: FST = 0.05/; Nm: 4.7). According to molecular variance analysis (AMOYA), the genetic distance between populations was...series of population studies were conducted. using mor- phological and molecular tools (Manguin 1999). ori- ented toward clarifying both taxonomic status...and ge- netic structure within its range of distribution. Lounibos and Conn (2000) recently reviewed the use of molecular markers in the study of the

  8. Evaluation of Microbial Diversity in Wetland through Polymerase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP)

    DTIC Science & Technology

    2006-06-01

    MICROBIAL DIVERSITY IN WETLANDS THROUGH POLYMERASE CHAIN REACTION ( PCR ) AND RESTRICTION FRAGMENT LENGTH POLYMORPHISM ( RFLP ) THESIS Presented to the...MICROBIAL DIVERSITY IN WETLANDS THROUGH POLYMERASE CHAIN REACTION ( PCR ) AND RESTRICTION FRAGMENT LENGTH POLYMORPHISM ( RFLP ) Gregory K. Joseph, B.A...AFIT/GES/ENV/06J-02 EVALUATION OF MICROBIAL DIVERSITY IN WETLANDS THROUGH POLYMERASE CHAIN REACTION ( PCR ) AND RESTRICTION FRAGMENT LENGTH

  9. Conformational studies of cellulosic fragments by DFT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The study of cellulosic fragments by DFTr is a continuation of our efforts to produce quality structural data that will be valuable to those working in the field of cellulose structure and enzymatic degradation. Using a reduced basis set and density functional DFTr (B3LYP), optimization of cellulosi...

  10. Fragmentation of 3-hydroxyflavone; a computational and mass spectrometric study.

    PubMed

    Lewars, Errol G; March, Raymond E

    2007-01-01

    In a recent study of the collision-induced dissociation of protonated and deprotonated molecules of 3-, 5-, 6-, 7-, 2'-, 3'- and 4'-hydroxyflavone, it was observed that the ratio, gamma, of the propensities for cross-ring cleavage (CRC) to ring opening (RO) varied by a factor of 660, i.e., from 0.014:1 (for deprotonated 3-hydroxyflavone) to 9.27:1 (for deprotonated 5-hydroxyflavone). An explanation for the variation of gamma was presented in terms of experimental NMR (13)C and (1)H spectra modified by computation. Deprotonated 3-hydroxyflavone exhibited the highest ion signal intensity for fragmentation following RO relative to that for CRC in that gamma = 0.014:1. Because no chemical computations of the fragmentation of protonated and deprotonated monohydroxyflavone molecules have been carried out thus far, the basis on which fragmentation mechanisms for deprotonated 3-hydroxyflavone have been proposed is principally chemical intuition. The energy states of product ions formed in the fragmentation of deprotonated 3-hydroxyflavone molecules were computed by the CBS-4M method implemented in Gaussian 03. The overly demanding calculations needed to handle diradicals reliably and directly were circumvented by a process in which each of the bond-breaking reactions was approximated by a process that gave two monoradicals. Bond energies were calculated, with one exception, from the approximation reactions as the energy of products minus the energy of reactants.

  11. Growth of fullerene fragments using the Diels-Alder cycloaddition reaction: first step towards a C60 synthesis by dimerization.

    PubMed

    Mojica, Martha; Méndez, Francisco; Alonso, Julio A

    2013-02-13

    Density Functional Theory has been used to model the Diels-Alder reactions of the fullerene fragments triindenetriphenilene and pentacyclopentacorannulene with ethylene and 1,3-butadiene. The purpose is to prove the feasibility of using Diels-Alder cycloaddition reactions to grow fullerene fragments step by step, and to dimerize fullerene fragments, as a way to obtain C₆₀. The dienophile character of the fullerene fragments is dominant, and the reaction of butadiene with pentacyclopentacorannulene is favored.

  12. Nuclear reaction studies

    SciTech Connect

    Alexander, J.M.; Lacey, R.A.

    1994-11-01

    Research focused on the statistical and dynamical properties of ``hot`` nuclei formed in symmetric heavy-ion reactions. Theses included ``flow`` measurements and the mechanism for multifragment disassembly. Model calculations are being performed for the reactions C+C, Ne+Al, Ar+Sc, Kr+Nb, and Xe+La. It is planned to study {sup 40}Ar reactions from 27 to 115 MeV/nucleon. 2 figs., 41 refs.

  13. Microscopic Calculation of Fission Fragment Energies for the 239Pu(nth,f) Reaction

    SciTech Connect

    Younes, W; Gogny, D

    2011-10-03

    We calculate the total kinetic and excitation energies of fragments produced in the thermal-induced fission of {sup 239}Pu. This result is a proof-of-principle demonstration for a microscopic approach to the calculation of fission-fragment observables for applied data needs. In addition, the calculations highlight the application of a fully quantum mechanical description of scission, and the importance of exploring scission configurations as a function of the moments of the fragments, rather than through global constraints on the moments of the fissioning nucleus. Using a static microscopic calculation of configurations at and near scission, we have identified fission fragments for the {sup 239}Pu (n{sub th}, f) reaction and extracted their total kinetic and excitation energies. Comparison with data shows very good overall agreement between theory and experiment. Beyond their success as a proof of principle, these calculations also highlight the importance of local constraints on the fragments themselves in microscopic calculations.

  14. Simple plate-based, parallel synthesis of disulfide fragments using the CuAAC click reaction.

    PubMed

    Turner, David M; Tom, Christopher T M B; Renslo, Adam R

    2014-12-08

    Disulfide exchange screening is a site-directed approach to fragment-based lead discovery that requires a bespoke library of disulfide-containing fragments. Previously, we described a simple one-pot, two-step synthesis of disulfide fragments from amine- or acid-bearing starting materials. Here, we describe the synthesis of disulfide fragments that bear a 1,4-substituted-1,2,3-triazole linkage between disulfide and molecular diversity element. This work establishes the compatibility of copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) chemistry with a one-pot, two-step reaction sequence that can be readily parallelized. We performed 96 reactions in a single deep-well microtiter plate, employing 48 alkynes and two different azide linker reagents. From this effort, a total of 81 triazole-containing disulfide fragments were obtained in useful isolated yields. Thus, CuAAC chemistry offers an experimentally convenient method to rapidly prepare disulfide fragments that are structurally distinct from fragments accessed via amide, sulfonamide, or isocyanate chemistries.

  15. Mutagenicity Assessment of Organophosphates using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism Assay

    PubMed Central

    Bhinder, Preety; Chaudhry, Asha

    2013-01-01

    Objectives: In this study we have evaluated the mutagenicity of organophosphate pesticides acephate, chlorpyrifos, and profenofos using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay with the mosquito Culex quinquefasciatus taken as an experimental model. Materials and Methods: Second instar larvae were treated with LC20 of each pesticide for 24 h and mutations induced in the sequence of mitochondrial COII gene (690bp) were studied from restriction patterns generated with AluI, PacI, and PsiI restriction endonucleases. Results: Variations in the number and size of digested fragments were recorded from treated individuals compared with controls showing that the restriction enzymes created a cut at different locations. In addition, sequences of COII gene from control and treated individuals were also used to confirm the RFLP patterns. From the sequence alignment data, it was found that mutations caused the destruction and generation of restriction sites in the gene sequence of treated individuals. Conclusion: This study indicates that all the three pesticides had potential to induce mutations in the normal sequence of COII gene and also advocates the use of PCR-RFLP assay as an efficient, rapid, and sensitive technique to detect mutagenicity of pesticides. PMID:24403735

  16. Interplay between compound and fragments aspects of nuclear fission and heavy-ion reaction

    SciTech Connect

    Moller, Peter; Iwamoto, A; Ichikawa, I

    2010-09-10

    The scission point in nuclear fission plays a special role where one-body system changes to two-body system. Inverse of this situation is realized in heavy-ion fusion reaction where two-body system changes to one body system. Among several peculiar phenomena expected to occur during this change, we focus our attention to the behavior of compound and fragments shell effects. Some aspects of the interplay between compound and fragments shell effect are discussed related to the topics of the fission valleys in the potential energy surface of actinide nuclei and the fusion-like trajectory found in the cold fusion reaction leading to superheavy nuclei.

  17. Construction of an antimyoglobin single-chain variable fragment with rapid reaction kinetics.

    PubMed

    Jang, Jun-Hyuck; Kim, Dong-Hyung; Paek, Se-Hwan; Woo, Eui-Jeon; Kim, Young-Wan

    2016-01-01

    Antibodies with rapid reaction kinetics (high association and dissociation rates), named reversible antibodies, are used to perform continuous monitoring of sensitive disease biomarkers. In cases of acute myocardial infarction (AMI), continuous monitoring and early diagnosis are important. Human myoglobin (Myo) is a useful biomarker for AMI during the early stage after the onset of symptoms. In this study, a single-chain variable fragment (scFv) specific to Myo was derived from an IgG antibody that has rapid reaction kinetics. Enzyme-linked immunosorbent assay revealed that recombinant scFv exhibited 3.8-fold reduced affinity compared with the parent IgG antibody based on the antibody concentration necessary for 50% of the maximum signal. The scFv retained the rapid reaction kinetic mode with average kon and koff of 2.63 × 10(5) M(-1) Sec(-1) and 3.25 × 10(-3) Sec(-1) , respectively, which were reduced to 10- and 2.3-fold compared with those of the parent antibody. The equilibrium constant for the association of the scFv (KA = 8.09 × 10(7) M(-1) ) was 4.6-fold lower than that of its parent IgG antibody. This scFv may be a starting point for further mutagenesis/kinetic and structural analyses providing valuable insight into the mechanism of reversible antibodies.

  18. Exothermic Surface Reactions in Alumina-Aluminum Shell-Core Nanoparticles with Iodine Oxide Decomposition Fragments

    DTIC Science & Technology

    2014-02-22

    AND SUBTITLE Sa. CONTRACT NUMBER Exothennic smface reactions in alumina-aluminum shell-core W911NF-11-1-0439 nanoprui icles with iodine oxide...is observed for aluminum and an iodine -containing oxidizer. This PIR is exothermic and precedes the main exothennic reaction conesponding to aluminum...combustion. For the aluminum and iodine oxide system, exothennic smface chemistiy was recently predicted for I-0 fragments fonning bridge bonds with

  19. Nuclear fragmentation and charge-exchange reactions induced by pions in the Δ -resonance region

    NASA Astrophysics Data System (ADS)

    Feng, Zhao-Qing

    2016-11-01

    The dynamics of the nuclear fragmentations and the charge exchange reactions in pion-nucleus collisions near the Δ (1232) resonance energies has been investigated within the Lanzhou quantum molecular dynamics transport model. An isospin-, momentum-, and density-dependent pion-nucleon potential is implemented in the model, which influences the pion dynamics, in particular the kinetic energy spectra, but weakly impacts the fragmentation mechanism. The absorption process in pion-nucleon collisions to form the Δ (1232) resonance dominates the heating mechanism of the target nucleus. The excitation energy transferred to the target nucleus increases with the pion kinetic energy and is similar for both π-- and π+-induced reactions. The magnitude of fragmentation of the target nucleus weakly depends on the pion energy. The isospin ratio in the pion double-charge exchange is influenced by the isospin ingredient of target nucleus.

  20. The Conversion of Smaller Borane Fragments to Larger Structures. Systematics of Boron Hydride Reactions.

    DTIC Science & Technology

    1984-12-31

    Robert W. Parry and Goji Kodama Contract DAAG-29-8rl-K-Ol0l S. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT, TASK S Department of...Entered; THE CONVERSION OF SMALLER BORANE FRAGMENTS TO LARGER STRUCTURES - SYSTEMATICS OF BORON HYDRIDE REACTIONS FINAL REPORT ROBERT W. PARRY AND GOJI

  1. Purification and characterization of Fab fragments with rapid reaction kinetics against myoglobin.

    PubMed

    Song, Hyung-Nam; Kim, Dong-Hyung; Park, Sung-Goo; Lee, Myung Kyu; Paek, Se-Hwan; Woo, Eui-Jeon

    2015-01-01

    Myoglobin is an early biomarker for acute myocardial infarction. Recently, we isolated the antibody IgG-Myo2-7ds, which exhibits unique rapid reaction kinetics toward human myoglobin antigen. Antibodies with rapid dissociation kinetics are thought to be premature IgG forms that are produced during the early stage of in vivo immunization. In the present study, we identified the epitope region of the IgG-Myo2-7ds antibody to be the C-terminal region of myoglobin, which corresponds to 144-154 aa. The Fab fragment was directly purified by papain cleavage and protein G affinity chromatography and demonstrated kinetics of an association constant of 4.02 × 10(4) M(-1) s(-1) and a dissociation constant of 2.28 × 10(-2) s(-1), which retained the unique reaction kinetics of intact IgG-Myo2-7ds antibodies. Because a rapid dissociation antibody can be utilized for antibody recycling, the results from this study would provide a platform for the development of antibody engineering in potential diagnostic areas such as a continuous monitoring system for heart disease.

  2. The Family Circle: A Study in Fragmentation

    ERIC Educational Resources Information Center

    Bronfenbrenner, Urie

    1976-01-01

    Presents data describing the fragmentation of the family, suggests causes for the fragmentation, and offers suggestions for reversing the trend. The suggestions focus on day care, part-time employment practices, enhancing the position of women, and work and responsibility. (IRT)

  3. Influence of fragment reaction of relativistic heavy charged particles on heavy-ion radiotherapy

    NASA Astrophysics Data System (ADS)

    Matsufuji, Naruhiro; Fukumura, Akifumi; Komori, Masataka; Kanai, Tatsuaki; Kohno, Toshiyuki

    2003-06-01

    The production of projectile fragments is one of the most important, but not yet perfectly understood, problems to be considered when planning for the utilization of high-energy heavy charged particles for radiotherapy. This paper reports our investigation of the fragments' fluence and linear energy transfer (LET) spectra produced from various incident ions using an experimental approach to reveal these physical qualities of the beams. Polymethyl methacrylate, as a substitute for the human body, was used as a target. A ΔE-E counter telescope with a plastic scintillator and a BGO scintillator made it possible to identify the species of fragments based on differences of various elements. By combining a gas-flow proportional counter with a counter telescope system, LET spectra as well as fluence spectra of the fragments were derived for each element down from the primary particles to hydrogen. Among them, the information on hydrogen and helium fragments was derived for the first time. The result revealed that the number of light fragments, such as hydrogen and helium, became larger than the number of primaries in the vicinity of the range end. However, the greater part of the dose delivered to a cell was still governed by the primaries. The calculated result of a simulation used for heavy-ion radiotherapy indicated room for improving the reaction model.

  4. Carbon fragmentation measurements and validation of the Geant4 nuclear reaction models for hadrontherapy.

    PubMed

    De Napoli, M; Agodi, C; Battistoni, G; Blancato, A A; Cirrone, G A P; Cuttone, G; Giacoppo, F; Morone, M C; Nicolosi, D; Pandola, L; Patera, V; Raciti, G; Rapisarda, E; Romano, F; Sardina, D; Sarti, A; Sciubba, A; Scuderi, V; Sfienti, C; Tropea, S

    2012-11-21

    Nuclear fragmentation measurements are necessary when using heavy-ion beams in hadrontherapy to predict the effects of the ion nuclear interactions within the human body. Moreover, they are also fundamental to validate and improve the Monte Carlo codes for their use in planning tumor treatments. Nowadays, a very limited set of carbon fragmentation cross sections are being measured, and in particular, to our knowledge, no double-differential fragmentation cross sections at intermediate energies are available in the literature. In this work, we have measured the double-differential cross sections and the angular distributions of the secondary fragments produced in the (12)C fragmentation at 62 A MeV on a thin carbon target. The experimental data have been used to benchmark the prediction capability of the Geant4 Monte Carlo code at intermediate energies, where it was never tested before. In particular, we have compared the experimental data with the predictions of two Geant4 nuclear reaction models: the Binary Light Ions Cascade and the Quantum Molecular Dynamic. From the comparison, it has been observed that the Binary Light Ions Cascade approximates the angular distributions of the fragment production cross sections better than the Quantum Molecular Dynamic model. However, the discrepancies observed between the experimental data and the Monte Carlo simulations lead to the conclusion that the prediction capability of both models needs to be improved at intermediate energies.

  5. Carbon fragmentation measurements and validation of the Geant4 nuclear reaction models for hadrontherapy

    NASA Astrophysics Data System (ADS)

    De Napoli, M.; Agodi, C.; Battistoni, G.; Blancato, A. A.; Cirrone, G. A. P.; Cuttone, G.; Giacoppo, F.; Morone, M. C.; Nicolosi, D.; Pandola, L.; Patera, V.; Raciti, G.; Rapisarda, E.; Romano, F.; Sardina, D.; Sarti, A.; Sciubba, A.; Scuderi, V.; Sfienti, C.; Tropea, S.

    2012-11-01

    Nuclear fragmentation measurements are necessary when using heavy-ion beams in hadrontherapy to predict the effects of the ion nuclear interactions within the human body. Moreover, they are also fundamental to validate and improve the Monte Carlo codes for their use in planning tumor treatments. Nowadays, a very limited set of carbon fragmentation cross sections are being measured, and in particular, to our knowledge, no double-differential fragmentation cross sections at intermediate energies are available in the literature. In this work, we have measured the double-differential cross sections and the angular distributions of the secondary fragments produced in the 12C fragmentation at 62 A MeV on a thin carbon target. The experimental data have been used to benchmark the prediction capability of the Geant4 Monte Carlo code at intermediate energies, where it was never tested before. In particular, we have compared the experimental data with the predictions of two Geant4 nuclear reaction models: the Binary Light Ions Cascade and the Quantum Molecular Dynamic. From the comparison, it has been observed that the Binary Light Ions Cascade approximates the angular distributions of the fragment production cross sections better than the Quantum Molecular Dynamic model. However, the discrepancies observed between the experimental data and the Monte Carlo simulations lead to the conclusion that the prediction capability of both models needs to be improved at intermediate energies.

  6. Low energy electron induced fragmentation and reactions of DNA and its molecular components

    NASA Astrophysics Data System (ADS)

    Bass, Andrew

    2005-05-01

    Much research has been stimulated by the recognition that ionizing radiation can, in condensed matter, generate large numbers of secondary electrons with energies less than 20 eV [1] and by the experimental demonstration that such electrons may induce both single and double strand breaks in plasmid DNA [2]. Identifying the underlying mechanisms involves several research methodologies, from further experiments with DNA to studies of the electron interaction with the component `sub-units' of DNA in both the gas and condensed phases [3]. In particular, understanding electron-induced strand break damage, the type of damage most difficult for organisms to repair, necessitates study of the sub-units of DNA back-bone, and here Tetrahyrofuran (THF) and its derivatives, provide a useful model for the furyl ring at the centre of the deoxyribose sugar. In this contribution, we review with particular reference to DNA and related molecules, the use of electron spectroscopy and mass spectrometry to study electron-induced fragmentation and reactions in thin molecular solids. We describe a newly completed instrument that combines laser post-ionization with a time-of-flight mass analyzer for highly sensitive ion and neutral detection. Use of the instrument is illustrated with results for THF and derivatives. Anion desorption measurements reveal the role of transient negative ions (TNI) and Dissociative Electron Attachment in significant molecular fragmentation and permit effective cross sections for this electron-induced damage to be obtained. The neutral yield functions also illustrate the importance of TNI, mirroring features seen in recently measured cross sections for electron induced aldehyde production in THF [4]. 1. J. A. Laverne and S. M. Pimblott, Radiat. Res. 141, 208 (1995) 2. B. Boudaiffa, et al, Science 287, 1658 (2000) 3. L. Sanche. Physica Scripta. 68, C108, (2003) 4. S.-P. Breton, et al.,J. Chem. Phys. 121, 11240 (2004)

  7. Tungsten fragmentation in nuclear reactions induced by high-energy cosmic-ray protons

    SciTech Connect

    Chechenin, N. G. Chuvilskaya, T. V.; Shirokova, A. A.; Kadmenskii, A. G.

    2015-01-15

    Tungsten fragmentation arising in nuclear reactions induced by cosmic-ray protons in space-vehicle electronics is considered. In modern technologies of integrated circuits featuring a three-dimensional layered architecture, tungsten is frequently used as a material for interlayer conducting connections. Within the preequilibrium model, tungsten-fragmentation features, including the cross sections for the elastic and inelastic scattering of protons of energy between 30 and 240 MeV; the yields of isotopes and isobars; their energy, charge, and mass distributions; and recoil energy spectra, are calculated on the basis of the TALYS and EMPIRE-II-19 codes. It is shown that tungsten fragmentation affects substantially forecasts of failures of space-vehicle electronics.

  8. Ontology aided modeling of organic reaction mechanisms with flexible and fragment based XML markup procedures.

    PubMed

    Sankar, Punnaivanam; Aghila, Gnanasekaran

    2007-01-01

    The mechanism models for primary organic reactions encoding the structural fragments undergoing substitution, addition, elimination, and rearrangements are developed. In the proposed models, each and every structural component of mechanistic pathways is represented with flexible and fragment based markup technique in XML syntax. A significant feature of the system is the encoding of the electron movements along with the other components like charges, partial charges, half bonded species, lone pair electrons, free radicals, reaction arrows, etc. needed for a complete representation of reaction mechanism. The rendering of reaction schemes described with the proposed methodology is achieved with a concise XML extension language interoperating with the structure markup. The reaction scheme is visualized as 2D graphics in a browser by converting them into SVG documents enabling the desired layouts normally perceived by the chemists conventionally. An automatic representation of the complex patterns of the reaction mechanism is achieved by reusing the knowledge in chemical ontologies and developing artificial intelligence components in terms of axioms.

  9. Measurements of charge distributions of the fragments in the low energy fission reaction

    NASA Astrophysics Data System (ADS)

    Wang, Taofeng; Han, Hongyin; Meng, Qinghua; Wang, Liming; Zhu, Liping; Xia, Haihong

    2013-01-01

    The measurement for charge distributions of fragments in spontaneous fission 252Cf has been performed by using a unique style of detector setup consisting of a typical grid ionization chamber and a ΔΕ-Ε particle telescope, in which a thin grid ionization chamber served as the ΔΕ-section and the E-section was an Au-Si surface barrier detector. The typical physical quantities of fragments, such as mass number and kinetic energies as well as the deposition in the gas ΔΕ detector and E detector were derived from the coincident measurement data. The charge distributions of the light fragments for the fixed mass number A2* and total kinetic energy (TKE) were obtained by the least-squares fits for the response functions of the ΔΕ detector with multi-Gaussian functions representing the different elements. The results of the charge distributions for some typical fragments are shown in this article which indicates that this detection setup has the charge distribution capability of Ζ:ΔΖ>40:1. The experimental method developed in this work for determining the charge distributions of fragments is expected to be employed in the neutron induced fissions of 232Th and 238U or other low energy fission reactions.

  10. Selective control over fragmentation reactions in polyatomic molecules using impulsive laser alignment.

    PubMed

    Xie, Xinhua; Doblhoff-Dier, Katharina; Xu, Huailiang; Roither, Stefan; Schöffler, Markus S; Kartashov, Daniil; Erattupuzha, Sonia; Rathje, Tim; Paulus, Gerhard G; Yamanouchi, Kaoru; Baltuška, Andrius; Gräfe, Stefanie; Kitzler, Markus

    2014-04-25

    We investigate the possibility of using molecular alignment for controlling the relative probability of individual reaction pathways in polyatomic molecules initiated by electronic processes on the few-femtosecond time scale. Using acetylene as an example, it is shown that aligning the molecular axis with respect to the polarization direction of the ionizing laser pulse does not only allow us to enhance or suppress the overall fragmentation yield of a certain fragmentation channel but, more importantly, to determine the relative probability of individual reaction pathways starting from the same parent molecular ion. We show that the achieved control over dissociation or isomerization pathways along specific nuclear degrees of freedom is based on a controlled population of associated excited dissociative electronic states in the molecular ion due to relatively enhanced ionization contributions from inner valence orbitals.

  11. Fission fragment mass distributions in reactions forming the {sup 213}Fr compound nucleus

    SciTech Connect

    Appannababu, S.; Mukherjee, S.; Deshmukh, N. N.; Rath, P. K.; Singh, N. L.; Nayak, B. K.; Thomas, R. G.; Choudhury, R. K.; Sugathan, P.; Jhingan, A.; Negi, D.; Prasad, E.

    2011-03-15

    The fission fragment mass angle correlations and mass ratio distributions have been investigated for the two systems {sup 16}O+{sup 197}Au and {sup 27}Al+{sup 186}W, leading to the same compound nucleus {sup 213}Fr around the Coulomb barrier energies. Systematic analysis of the variance of the mass distributions as a function of temperature and angular momentum suggests true compound nuclear fission for both the reactions, indicating the absence of nonequilibrium fission processes.

  12. Study of leading hadrons in gluon and quark fragmentation

    NASA Astrophysics Data System (ADS)

    Abdallah, J.; Abreu, P.; Adam, W.; Adzic, P.; Albrecht, T.; Alemany-Fernandez, R.; Allmendinger, T.; Allport, P. P.; Amaldi, U.; Amapane, N.; Amato, S.; Anashkin, E.; Andreazza, A.; Andringa, S.; Anjos, N.; Antilogus, P.; Apel, W.-D.; Arnoud, Y.; Ask, S.; Asman, B.; Augustin, J. E.; Augustinus, A.; Baillon, P.; Ballestrero, A.; Bambade, P.; Barbier, R.; Bardin, D.; Barker, G. J.; Baroncelli, A.; Battaglia, M.; Baubillier, M.; Becks, K.-H.; Begalli, M.; Behrmann, A.; Ben-Haim, E.; Benekos, N.; Benvenuti, A.; Berat, C.; Berggren, M.; Berntzon, L.; Bertrand, D.; Besancon, M.; Besson, N.; Bloch, D.; Blom, M.; Bluj, M.; Bonesini, M.; Boonekamp, M.; Booth, P. S. L.; Borisov, G.; Botner, O.; Bouquet, B.; Bowcock, T. J. V.; Boyko, I.; Bracko, M.; Brenner, R.; Brodet, E.; Bruckman, P.; Brunet, J. M.; Buschbeck, B.; Buschmann, P.; Calvi, M.; Camporesi, T.; Canale, V.; Carena, F.; Castro, N.; Cavallo, F.; Chapkin, M.; Charpentier, Ph.; Checchia, P.; Chierici, R.; Chliapnikov, P.; Chudoba, J.; Chung, S. U.; Cieslik, K.; Collins, P.; Contri, R.; Cosme, G.; Cossutti, F.; Costa, M. J.; Crennell, D.; Cuevas, J.; D'Hondt, J.; Dalmau, J.; da Silva, T.; da Silva, W.; Della Ricca, G.; de Angelis, A.; de Boer, W.; de Clercq, C.; de Lotto, B.; de Maria, N.; de Min, A.; de Paula, L.; di Ciaccio, L.; di Simone, A.; Doroba, K.; Drees, J.; Eigen, G.; Ekelof, T.; Ellert, M.; Elsing, M.; Espirito Santo, M. C.; Fanourakis, G.; Fassouliotis, D.; Feindt, M.; Fernandez, J.; Ferrer, A.; Ferro, F.; Flagmeyer, U.; Foeth, H.; Fokitis, E.; Fulda-Quenzer, F.; Fuster, J.; Gandelman, M.; Garcia, C.; Gavillet, Ph.; Gazis, E.; Gokieli, R.; Golob, B.; Gomez-Ceballos, G.; Goncalves, P.; Graziani, E.; Grosdidier, G.; Grzelak, K.; Guy, J.; Haag, C.; Hallgren, A.; Hamacher, K.; Hamilton, K.; Haug, S.; Hauler, F.; Hedberg, V.; Hennecke, M.; Herr, H.; Hoffman, J.; Holmgren, S.-O.; Holt, P. J.; Houlden, M. A.; Jackson, J. N.; Jarlskog, G.; Jarry, P.; Jeans, D.; Johansson, E. K.; Johansson, P. D.; Jonsson, P.; Joram, C.; Jungermann, L.; Kapusta, F.; Katsanevas, S.; Katsoufis, E.; Kernel, G.; Kersevan, B. P.; Kerzel, U.; King, B. T.; Kjaer, N. J.; Kluit, P.; Kokkinias, P.; Kourkoumelis, C.; Kouznetsov, O.; Krumstein, Z.; Kucharczyk, M.; Lamsa, J.; Leder, G.; Ledroit, F.; Leinonen, L.; Leitner, R.; Lemonne, J.; Lepeltier, V.; Lesiak, T.; Liebig, W.; Liko, D.; Lipniacka, A.; Lopes, J. H.; Lopez, J. M.; Loukas, D.; Lutz, P.; Lyons, L.; MacNaughton, J.; Malek, A.; Maltezos, S.; Mandl, F.; Marco, J.; Marco, R.; Marechal, B.; Margoni, M.; Marin, J.-C.; Mariotti, C.; Markou, A.; Martinez-Rivero, C.; Masik, J.; Mastroyiannopoulos, N.; Matorras, F.; Matteuzzi, C.; Mazzucato, F.; Mazzucato, M.; Mc Nulty, R.; Meroni, C.; Migliore, E.; Mitaroff, W.; Mjoernmark, U.; Moa, T.; Moch, M.; Moenig, K.; Monge, R.; Montenegro, J.; Moraes, D.; Moreno, S.; Morettini, P.; Mueller, U.; Muenich, K.; Mulders, M.; Mundim, L.; Murray, W.; Muryn, B.; Myatt, G.; Myklebust, T.; Nassiakou, M.; Navarria, F.; Nawrocki, K.; Nicolaidou, R.; Nikolenko, M.; Oblakowska-Mucha, A.; Obraztsov, V.; Olshevski, A.; Onofre, A.; Orava, R.; Osterberg, K.; Ouraou, A.; Oyanguren, A.; Paganoni, M.; Paiano, S.; Palacios, J. P.; Palka, H.; Papadopoulou, Th. D.; Pape, L.; Parkes, C.; Parodi, F.; Parzefall, U.; Passeri, A.; Passon, O.; Peralta, L.; Perepelitsa, V.; Perrotta, A.; Petrolini, A.; Piedra, J.; Pieri, L.; Pierre, F.; Pimenta, M.; Piotto, E.; Podobnik, T.; Poireau, V.; Pol, M. E.; Polok, G.; Pozdniakov, V.; Pukhaeva, N.; Pullia, A.; Rames, J.; Read, A.; Rebecchi, P.; Rehn, J.; Reid, D.; Reinhardt, R.; Renton, P.; Richard, F.; Ridky, J.; Rivero, M.; Rodriguez, D.; Romero, A.; Ronchese, P.; Roudeau, P.; Rovelli, T.; Ruhlmann-Kleider, V.; Ryabtchikov, D.; Sadovsky, A.; Salmi, L.; Salt, J.; Sander, C.; Savoy-Navarro, A.; Schwickerath, U.; Sekulin, R.; Siebel, M.; Sisakian, A.; Smadja, G.; Smirnova, O.; Sokolov, A.; Sopczak, A.; Sosnowski, R.; Spassov, T.; Stanitzki, M.; Stocchi, A.; Strauss, J.; Stugu, B.; Szczekowski, M.; Szeptycka, M.; Szumlak, T.; Tabarelli, T.; Taffard, A. C.; Tegenfeldt, F.; Timmermans, J.; Tkatchev, L.; Tobin, M.; Todorovova, S.; Tome, B.; Tonazzo, A.; Tortosa, P.; Travnicek, P.; Treille, D.; Tristram, G.; Trochimczuk, M.; Troncon, C.; Turluer, M.-L.; Tyapkin, I. A.; Tyapkin, P.; Tzamarias, S.; Uvarov, V.; Valenti, G.; van Dam, P.; van Eldik, J.; van Remortel, N.; van Vulpen, I.; Vegni, G.; Veloso, F.; Venus, W.; Verdier, P.; Verzi, V.; Vilanova, D.; Vitale, L.; Vrba, V.; Wahlen, H.; Washbrook, A. J.; Weiser, C.; Wicke, D.; Wickens, J.; Wilkinson, G.; Winter, M.; Witek, M.; Yushchenko, O.; Zalewska, A.; Zalewski, P.; Zavrtanik, D.; Zhuravlov, V.; Zimin, N. I.; Zintchenko, A.; Zupan, M.; Delphi Collaboration

    2006-12-01

    The study of quark jets in e+e- reactions at LEP has demonstrated that the hadronisation process is reproduced well by the Lund string model. However, our understanding of gluon fragmentation is less complete. In this study enriched quark and gluon jet samples of different purities are selected in three-jet events from hadronic decays of the Z collected by the DELPHI experiment in the LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are defined by requiring a rapidity gap and their sum of charges is studied. An excess of leading systems with total charge zero is found for gluon jets in all cases, when compared to Monte Carlo simulations with JETSET (with and without Bose-Einstein correlations included) and ARIADNE. The corresponding leading systems of quark jets do not exhibit such an excess. The influence of the gap size and of the gluon purity on the effect is studied and a concentration of the excess of neutral leading systems at low invariant masses (≲ 2 GeV /c2) is observed, indicating that gluon jets might have an additional hitherto undetected fragmentation mode via a two-gluon system. This could be an indication of a possible production of gluonic states as predicted by QCD.

  13. Study of leading hadrons in gluon and quark fragmentation

    NASA Astrophysics Data System (ADS)

    DELPHI Collaboration; Abdallah, J.; Abreu, P.; Adam, W.; Adzic, P.; Albrecht, T.; Alemany-Fernandez, R.; Allmendinger, T.; Allport, P. P.; Amaldi, U.; Amapane, N.; Amato, S.; Anashkin, E.; Andreazza, A.; Andringa, S.; Anjos, N.; Antilogus, P.; Apel, W.-D.; Arnoud, Y.; Ask, S.; Asman, B.; Augustin, J. E.; Augustinus, A.; Baillon, P.; Ballestrero, A.; Bambade, P.; Barbier, R.; Bardin, D.; Barker, G. J.; Baroncelli, A.; Battaglia, M.; Baubillier, M.; Becks, K.-H.; Begalli, M.; Behrmann, A.; Ben-Haim, E.; Benekos, N.; Benvenuti, A.; Berat, C.; Berggren, M.; Berntzon, L.; Bertrand, D.; Besancon, M.; Besson, N.; Bloch, D.; Blom, M.; Bluj, M.; Bonesini, M.; Boonekamp, M.; Booth, P. S. L.; Borisov, G.; Botner, O.; Bouquet, B.; Bowcock, T. J. V.; Boyko, I.; Bracko, M.; Brenner, R.; Brodet, E.; Bruckman, P.; Brunet, J. M.; Buschbeck, B.; Buschmann, P.; Calvi, M.; Camporesi, T.; Canale, V.; Carena, F.; Castro, N.; Cavallo, F.; Chapkin, M.; Charpentier, Ph.; Checchia, P.; Chierici, R.; Chliapnikov, P.; Chudoba, J.; Chung, S. U.; Cieslik, K.; Collins, P.; Contri, R.; Cosme, G.; Cossutti, F.; Costa, M. J.; Crennell, D.; Cuevas, J.; D'Hondt, J.; Dalmau, J.; da Silva, T.; da Silva, W.; Della Ricca, G.; de Angelis, A.; de Boer, W.; de Clercq, C.; de Lotto, B.; de Maria, N.; de Min, A.; de Paula, L.; di Ciaccio, L.; di Simone, A.; Doroba, K.; Drees, J.; Eigen, G.; Ekelof, T.; Ellert, M.; Elsing, M.; Espirito Santo, M. C.; Fanourakis, G.; Fassouliotis, D.; Feindt, M.; Fernandez, J.; Ferrer, A.; Ferro, F.; Flagmeyer, U.; Foeth, H.; Fokitis, E.; Fulda-Quenzer, F.; Fuster, J.; Gandelman, M.; Garcia, C.; Gavillet, Ph.; Gazis, E.; Gokieli, R.; Golob, B.; Gomez-Ceballos, G.; Goncalves, P.; Graziani, E.; Grosdidier, G.; Grzelak, K.; Guy, J.; Haag, C.; Hallgren, A.; Hamacher, K.; Hamilton, K.; Haug, S.; Hauler, F.; Hedberg, V.; Hennecke, M.; Herr, H.; Hoffman, J.; Holmgren, S.-O.; Holt, P. J.; Houlden, M. A.; Jackson, J. N.; Jarlskog, G.; Jarry, P.; Jeans, D.; Johansson, E. K.; Johansson, P. D.; Jonsson, P.; Joram, C.; Jungermann, L.; Kapusta, F.; Katsanevas, S.; Katsoufis, E.; Kernel, G.; Kersevan, B. P.; Kerzel, U.; King, B. T.; Kjaer, N. J.; Kluit, P.; Kokkinias, P.; Kourkoumelis, C.; Kouznetsov, O.; Krumstein, Z.; Kucharczyk, M.; Lamsa, J.; Leder, G.; Ledroit, F.; Leinonen, L.; Leitner, R.; Lemonne, J.; Lepeltier, V.; Lesiak, T.; Liebig, W.; Liko, D.; Lipniacka, A.; Lopes, J. H.; Lopez, J. M.; Loukas, D.; Lutz, P.; Lyons, L.; MacNaughton, J.; Malek, A.; Maltezos, S.; Mandl, F.; Marco, J.; Marco, R.; Marechal, B.; Margoni, M.; Marin, J.-C.; Mariotti, C.; Markou, A.; Martinez-Rivero, C.; Masik, J.; Mastroyiannopoulos, N.; Matorras, F.; Matteuzzi, C.; Mazzucato, F.; Mazzucato, M.; Mc Nulty, R.; Meroni, C.; Migliore, E.; Mitaroff, W.; Mjoernmark, U.; Moa, T.; Moch, M.; Moenig, K.; Monge, R.; Montenegro, J.; Moraes, D.; Moreno, S.; Morettini, P.; Mueller, U.; Muenich, K.; Mulders, M.; Mundim, L.; Murray, W.; Muryn, B.; Myatt, G.; Myklebust, T.; Nassiakou, M.; Navarria, F.; Nawrocki, K.; Nicolaidou, R.; Nikolenko, M.; Oblakowska-Mucha, A.; Obraztsov, V.; Olshevski, A.; Onofre, A.; Orava, R.; Osterberg, K.; Ouraou, A.; Oyanguren, A.; Paganoni, M.; Paiano, S.; Palacios, J. P.; Palka, H.; Papadopoulou, Th. D.; Pape, L.; Parkes, C.; Parodi, F.; Parzefall, U.; Passeri, A.; Passon, O.; Peralta, L.; Perepelitsa, V.; Perrotta, A.; Petrolini, A.; Piedra, J.; Pieri, L.; Pierre, F.; Pimenta, M.; Piotto, E.; Podobnik, T.; Poireau, V.; Pol, M. E.; Polok, G.; Pozdniakov, V.; Pukhaeva, N.; Pullia, A.; Rames, J.; Read, A.; Rebecchi, P.; Rehn, J.; Reid, D.; Reinhardt, R.; Renton, P.; Richard, F.; Ridky, J.; Rivero, M.; Rodriguez, D.; Romero, A.; Ronchese, P.; Roudeau, P.; Rovelli, T.; Ruhlmann-Kleider, V.; Ryabtchikov, D.; Sadovsky, A.; Salmi, L.; Salt, J.; Sander, C.; Savoy-Navarro, A.; Schwickerath, U.; Sekulin, R.; Siebel, M.; Sisakian, A.; Smadja, G.; Smirnova, O.; Sokolov, A.; Sopczak, A.; Sosnowski, R.; Spassov, T.; Stanitzki, M.; Stocchi, A.; Strauss, J.; Stugu, B.; Szczekowski, M.; Szeptycka, M.; Szumlak, T.; Tabarelli, T.; Taffard, A. C.; Tegenfeldt, F.; Timmermans, J.; Tkatchev, L.; Tobin, M.; Todorovova, S.; Tome, B.; Tonazzo, A.; Tortosa, P.; Travnicek, P.; Treille, D.; Tristram, G.; Trochimczuk, M.; Troncon, C.; Turluer, M.-L.; Tyapkin, I. A.; Tyapkin, P.; Tzamarias, S.; Uvarov, V.; Valenti, G.; van Dam, P.; van Eldik, J.; van Remortel, N.; van Vulpen, I.; Vegni, G.; Veloso, F.; Venus, W.; Verdier, P.; Verzi, V.; Vilanova, D.; Vitale, L.; Vrba, V.; Wahlen, H.; Washbrook, A. J.; Weiser, C.; Wicke, D.; Wickens, J.; Wilkinson, G.; Winter, M.; Witek, M.; Yushchenko, O.; Zalewska, A.; Zalewski, P.; Zavrtanik, D.; Zhuravlov, V.; Zimin, N. I.; Zintchenko, A.; Zupan, M.

    2006-12-01

    The study of quark jets in ee reactions at LEP has demonstrated that the hadronisation process is reproduced well by the Lund string model. However, our understanding of gluon fragmentation is less complete. In this study enriched quark and gluon jet samples of different purities are selected in three-jet events from hadronic decays of the Z collected by the DELPHI experiment in the LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are defined by requiring a rapidity gap and their sum of charges is studied. An excess of leading systems with total charge zero is found for gluon jets in all cases, when compared to Monte Carlo simulations with JETSET (with and without Bose Einstein correlations included) and ARIADNE. The corresponding leading systems of quark jets do not exhibit such an excess. The influence of the gap size and of the gluon purity on the effect is studied and a concentration of the excess of neutral leading systems at low invariant masses (≲2 GeV/c) is observed, indicating that gluon jets might have an additional hitherto undetected fragmentation mode via a two-gluon system. This could be an indication of a possible production of gluonic states as predicted by QCD.

  14. Studies on the HLA-DRB1 genotypes in Japanese women with severe pre-eclampsia positive and negative for anticardiolipin antibody using a polymerase chain reaction-restriction fragment length polymorphism method.

    PubMed

    Takakuwa, K; Honda, K; Ishii, K; Hataya, I; Yasuda, M; Tanaka, K

    1999-12-01

    The human leukocyte antigen (HLA)-DR genotype was determined in 54 Japanese women with severe pre-eclampsia in order to elucidate the relationship between HLA-DR antigen systems and pre-eclampsia. The patients were divided into two groups according to positivity for the anticardiolipin antibody (ACA), i.e. one patient group negative for ACA (n = 41) and the other patient group positive for ACA (n = 13). The frequency of each HLA-DRB1 allele in both groups was compared with that in 81 normally fertile Japanese women who had not experienced pre-eclampsia. The genotypes of HLA-DR antigens were determined using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The frequency of DRB1*04 and DRB1*0403 in the patient group positive for the ACA was significantly higher compared with that in the group of normal fertile women (P< 0.05). The frequency of each HLA-DRB1 allele was not significantly different between patient group with pre-eclampsia negative for ACA and group of normal fertile women. These results suggest a difference in the immunogenetic background between the patient groups with severe pre-eclampsia positive and negative for the ACA.

  15. Global transformation and fate of SOA: Implications of low-volatility SOA and gas-phase fragmentation reactions

    NASA Astrophysics Data System (ADS)

    Shrivastava, Manish; Easter, Richard C.; Liu, Xiaohong; Zelenyuk, Alla; Singh, Balwinder; Zhang, Kai; Ma, Po-Lun; Chand, Duli; Ghan, Steven; Jimenez, Jose L.; Zhang, Qi; Fast, Jerome; Rasch, Philip J.; Tiitta, Petri

    2015-05-01

    Secondary organic aerosols (SOA) are large contributors to fine-particle loadings and radiative forcing but are often represented crudely in global models. We have implemented three new detailed SOA treatments within the Community Atmosphere Model version 5 (CAM5) that allow us to compare the semivolatile versus nonvolatile SOA treatments (based on some of the latest experimental findings) and to investigate the effects of gas-phase fragmentation reactions. The new treatments also track SOA from biomass burning and biofuel, fossil fuel, and biogenic sources. For semivolatile SOA treatments, fragmentation reactions decrease the simulated annual global SOA burden from 7.5 Tg to 1.8 Tg. For the nonvolatile SOA treatment with fragmentation, the burden is 3.1 Tg. Larger differences between nonvolatile and semivolatile SOA (up to a factor of 5) exist in areas of continental outflow over the oceans. According to comparisons with observations from global surface Aerosol Mass Spectrometer measurements and the U.S. Interagency Monitoring of Protected Visual Environments (IMPROVE) network measurements, the FragNVSOA treatment, which treats SOA as nonvolatile and includes gas-phase fragmentation reactions, agrees best at rural locations. Urban SOA is underpredicted, but this may be due to the coarse model resolution. All three revised treatments show much better agreement with aircraft measurements of organic aerosols (OA) over the North American Arctic and sub-Arctic in spring and summer, compared to the standard CAM5 formulation. This is mainly due to the oxidation of SOA precursor gases from biomass burning, not included in standard CAM5, and long-range transport of biomass burning OA at high altitudes. The revised model configurations that include fragmentation (both semivolatile and nonvolatile SOA) show much better agreement with MODerate resolution Imaging Spectrometers (MODIS) aerosol optical depth data over regions dominated by biomass burning during the summer

  16. Orbital deflection of fragments produced through peripheral reactions of heavy nuclei at 290 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Momota, S.; Kanazawa, M.; Kitagawa, A.; Sato, S.

    2017-02-01

    The orbital deflection phenomenon of reaction products formed through peripheral reactions of heavy nuclei at intermediate energy is studied to examine the contributions of the Coulomb potential and nuclear potential that act between the projectile and target nuclei. The angular distributions of fragments produced in 1-nucleon removal and exchange reactions of 40Ar and 84Kr beams with C, Al, Nb, Tb, and Au targets at 290 MeV/nucleon were observed. A significant deflection effect was successfully identified in observed angular distributions at energies as low as Ei = 100 MeV/nucleon. The deflection effect increases with the atomic number of the target nuclei. The observed deflection effect is consistently explainable using the classical deflection angle, which is obtained with respect to a simple framework of the Coulomb potential and the real part of the energy-dependent nuclear potential, and the characteristic impact parameter between the projectile and target nuclei.

  17. Protein hydrogen exchange studied by the fragment separation method.

    PubMed

    Englander, J J; Rogero, J R; Englander, S W

    1985-05-15

    The potential of hydrogen-exchange studies for providing detailed information on protein structure and structural dynamics has not yet been realized, largely because of the continuing inability to correlate measured exchange behavior with the parts of a protein that generate that behavior. J. Rosa and F. M. Richards (1979, J. Mol. Biol. 133, 399-416) pioneered a promising approach to this problem in which tritium label at exchangeable proton sites can be located by fragmenting the protein, separating the fragments, and measuring the label carried by each fragment. However, severe losses of tritium label during the fragment separation steps have so far rendered the results ambiguous. This paper describes methods that minimize losses of tritium label during the fragment separation steps and correct for losses that do occur so that the label can be unambiguously located and even quantified. Steps that promote adequate fragment isolation are also described.

  18. Fission fragments mass distributions of nuclei populated by the multinucleon transfer channels of the 18O + 232Th reaction

    NASA Astrophysics Data System (ADS)

    Léguillon, R.; Nishio, K.; Hirose, K.; Makii, H.; Nishinaka, I.; Orlandi, R.; Tsukada, K.; Smallcombe, J.; Chiba, S.; Aritomo, Y.; Ohtsuki, T.; Tatsuzawa, R.; Takaki, N.; Tamura, N.; Goto, S.; Tsekhanovich, I.; Petrache, C. M.; Andreyev, A. N.

    2016-10-01

    It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multinucleon transfer channels of the 18O + 232Th reaction are used to study fission of fourteen nuclei 231,232,233,234Th, 232,233,234,235,236Pa, and 234,235,236,237,238U. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel, in selected bins of excitation energy. In particular, the mass distributions of 231,234Th and 234,235,236Pa are measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation-dissipation model.

  19. Microfluidic device for integrated restriction digestion reaction and resulting DNA fragment analysis.

    PubMed

    Xie, Hua; Li, Bowei; Zhong, Runtao; Qin, Jianhua; Zhu, Yisheng; Lin, Bingcheng

    2008-12-01

    A microfluidic system combining temperature-controlled reactor, analyte delivery, chip electrophoresis (CE) separation, and fluorescence detection was developed, in which the heaters, resistance temperature detectors, enzymatic reactors, CE channels, and pneumatic valves/pumps were integrated onto a single glass-PDMS chip. The microdevice was used to perform the digestion reaction, followed by on-line electrophoresis separation and detection of the resulting fragments with endonuclease BamHI and FokI as models. Pneumatic valves/pumps served not only for isolating the reaction region from the separation medium to prevent contamination, but also for delivering and quantitatively diluting the fluid from the reaction chamber to the CE section. Thus enzymatic reaction and electrophoresis separation could be insulated and connected as needed. A dynamic coating procedure with the use of PVP and mannitol was firstly adopted for glass-PDMS hybrid chip-based DNA separations, leading to an improved separation efficiency with reproducible migration time and theoretical plates. The expected 263- and 287-bp digestion products of BamHI and FokI were definitely verified by the size-based electrophoretic separation and detection. The whole integrated reaction-CE system can be manipulated in a simple manner with good reproducibility, which is expected to be applied in other on-line analysis of various biochemical reactions.

  20. Substituent effects on the gas-phase fragmentation reactions of sulfonium ion containing peptides.

    PubMed

    Sierakowski, James; Amunugama, Mahasilu; Roberts, Kade D; Reid, Gavin E

    2007-01-01

    The multistage mass spectrometric (MS/MS and MS3) gas-phase fragmentation reactions of methionine side-chain sulfonium ion containing peptides formed by reaction with a series of para-substituted phenacyl bromide (XBr where X=CH2COC6H4R, and R=--COOH, --COOCH3, --H, --CH3 and --CH2CH3) alkylating reagents have been examined in a linear quadrupole ion trap mass spectrometer. MS/MS of the singly (M+) and multiply ([M++nH](n+1)+) charged precursor ions results in exclusive dissociation at the fixed charge containing side chain, independently of the amino acid composition and precursor ion charge state (i.e., proton mobility). However, loss of the methylphenacyl sulfide side-chain fragment as a neutral versus charged (protonated) species was observed to be highly dependent on the proton mobility of the precursor ion, and the identity of the phenacyl group para-substituent. Molecular orbital calculations were performed at the B3LYP/6-31+G** level of theory to calculate the theoretical proton affinities of the neutral side-chain fragments. The log of the ratio of neutral versus protonated side-chain fragment losses from the derivatized side chain were found to exhibit a linear dependence on the proton affinity of the side-chain fragmentation product, as well as the proton affinities of the peptide product ions. Finally, MS3 dissociation of the nominally identical neutral and protonated loss product ions formed by MS/MS of the [M++H]2+ and [M++2H]3+ precursor ions, respectively, from the peptide GAILM(X)GAILK revealed significant differences in the abundances of the resultant product ions. These results suggest that the protonated peptide product ions formed by gas-phase fragmentation of sulfonium ion containing precursors in an ion trap mass spectrometer do not necessarily undergo intramolecular proton 'scrambling' prior to their further dissociation, in contrast to that previously demonstrated for peptide ions introduced by external ionization sources.

  1. Refolded scFv Antibody Fragment against Myoglobin Shows Rapid Reaction Kinetics

    PubMed Central

    Song, Hyung-Nam; Jang, Jun-Hyuck; Kim, Young-Wan; Kim, Dong-Hyung; Park, Sung-Goo; Lee, Myung Kyu; Paek, Se-Hwan; Woo, Eui-Jeon

    2014-01-01

    Myoglobin is one of the early biomarkers for acute myocardial infarction. Recently, we have screened an antibody with unique rapid reaction kinetics toward human myoglobin antigen. Antibodies with rapid reaction kinetics are thought to be an early IgG form produced during early stage of in vivo immunization. We produced a recombinant scFv fragment for the premature antibody from Escherichia coli using refolding technology. The scFv gene was constructed by connection of the VH–VL sequence with a (Gly4Ser)3 linker. The scFv fragment without the pelB leader sequence was expressed at a high level, but the solubility was extremely low. A high concentration of 8 M urea was used for denaturation. The dilution refolding process in the presence of arginine and the redox reagents GSH and GSSH successfully produced a soluble scFv protein. The resultant refolded scFv protein showed association and dissociation values of 9.32 × 10−4 M−1·s−1 and 6.29 × 10−3 s−1, respectively, with an affinity value exceeding 107 M−1 (kon/koff), maintaining the original rapid reaction kinetics of the premature antibody. The refolded scFv could provide a platform for protein engineering for the clinical application for diagnosis of heart disease and the development of a continuous biosensor. PMID:25530617

  2. Polymerase chain reaction-restriction fragment length polymorphism analysis of a 16S rRNA gene fragment for authentication of four clam species.

    PubMed

    Fernandez, Alicia; García, Teresa; Gonzalez, Isabel; Asensio, Luis; Rodriguez, Miguel Angel; Hernández, Pablo E; Martin, Rosario

    2002-04-01

    Specific identification of four clam species, Ruditapes decussatus (grooved carpet shell), Venerupis pullastra (pullet carpet shell), Ruditapes philippinarum (Japanese carpet shell), and Venerupis rhomboides (yellow carpet shell), was achieved by polymerase chain reaction-restriction fragment length polymorphism analysis of a fragment of the mitochondrial 16S rRNA gene. Amplification of DNA isolated from the foot muscle produced fragments of 511 bp for V. pullastra, 523 bp for R. decussatus, 545 bp for R. philippinarum, and 502 bp for V. rhomboides. The restriction profiles obtained by agarose gel electrophoresis when amplicons were digested with endonucleases BsmAI and BsrI allowed unequivocal identification of the four clam species. This approach would be less costly, simpler, and quicker than conventional sequencing of polymerase chain reaction products followed by detailed comparison of individual sequences, especially when large numbers of samples need to be analyzed.

  3. Radiation induced redox reactions and fragmentation of constituent ions in ionic liquids II. Imidazolium cations.

    SciTech Connect

    Shkrob, I. A.; Marin, T. W.; Chemerisov, S. D.; Hatcher, J.; Wishart, J.

    2011-04-14

    In part 1 of this study, radiolytic degradation of constituent anions in ionic liquids (ILs) was examined. The present study continues the themes addressed in part 1 and examines the radiation chemistry of 1,3-dialkyl substituted imidazolium cations, which currently comprise the most practically important and versatile class of ionic liquid cations. For comparison, we also examined 1,3-dimethoxy- and 2-methyl-substituted imidazolium and 1-butyl-4-methylpyridinium cations. In addition to identification of radicals using electron paramagnetic resonance spectroscopy (EPR) and selective deuterium substitution, we analyzed stable radiolytic products using {sup 1}H and {sup 13}C nuclear magnetic resonance (NMR) and tandem electrospray ionization mass spectrometry (ESMS). Our EPR studies reveal rich chemistry initiated through 'ionization of the ions': oxidation and the formation of radical dications in the aliphatic arms of the parent cations (leading to deprotonation and the formation of alkyl radicals in these arms) and reduction of the parent cation, yielding 2-imidazolyl radicals. The subsequent reactions of these radicals depend on the nature of the IL. If the cation is 2-substituted, the resulting 2-imidazolyl radical is relatively stable. If there is no substitution at C(2), the radical then either is protonated or reacts with the parent cation forming a C(2)-C(2) {sigma}{sigma}*-bound dimer radical cation. In addition to these reactions, when methoxy or C{sub {alpha}}-substituted alkyl groups occupy the N(1,3) positions, their elimination is observed. The elimination of methyl groups from N(1,3) was not observed. Product analyses of imidazolium liquids irradiated in the very-high-dose regime (6.7 MGy) reveal several detrimental processes, including volatilization, acidification, and oligomerization. The latter yields a polymer with m/z of 650 {+-} 300 whose radiolytic yield increases with dose (0.23 monomer units per 100 eV for 1-methyl-3-butylimidazolium

  4. Radiation induced redox reactions and fragmentation of constituent ions in ionic liquids. 2. Imidazolium cations.

    PubMed

    Shkrob, Ilya A; Marin, Timothy W; Chemerisov, Sergey D; Hatcher, Jasmine L; Wishart, James F

    2011-04-14

    In part 1 of this study, radiolytic degradation of constituent anions in ionic liquids (ILs) was examined. The present study continues the themes addressed in part 1 and examines the radiation chemistry of 1,3-dialkyl substituted imidazolium cations, which currently comprise the most practically important and versatile class of ionic liquid cations. For comparison, we also examined 1,3-dimethoxy- and 2-methyl-substituted imidazolium and 1-butyl-4-methylpyridinium cations. In addition to identification of radicals using electron paramagnetic resonance spectroscopy (EPR) and selective deuterium substitution, we analyzed stable radiolytic products using (1)H and (13)C nuclear magnetic resonance (NMR) and tandem electrospray ionization mass spectrometry (ESMS). Our EPR studies reveal rich chemistry initiated through "ionization of the ions": oxidation and the formation of radical dications in the aliphatic arms of the parent cations (leading to deprotonation and the formation of alkyl radicals in these arms) and reduction of the parent cation, yielding 2-imidazolyl radicals. The subsequent reactions of these radicals depend on the nature of the IL. If the cation is 2-substituted, the resulting 2-imidazolyl radical is relatively stable. If there is no substitution at C(2), the radical then either is protonated or reacts with the parent cation forming a C(2)-C(2) σσ*-bound dimer radical cation. In addition to these reactions, when methoxy or C(α)-substituted alkyl groups occupy the N(1,3) positions, their elimination is observed. The elimination of methyl groups from N(1,3) was not observed. Product analyses of imidazolium liquids irradiated in the very-high-dose regime (6.7 MGy) reveal several detrimental processes, including volatilization, acidification, and oligomerization. The latter yields a polymer with m/z of 650 ± 300 whose radiolytic yield increases with dose (~0.23 monomer units per 100 eV for 1-methyl-3-butylimidazolium trifluorosulfonate). Gradual

  5. Feasibility of Traveling Wave Direct Energy Conversion of Fission Reaction Fragments

    NASA Technical Reports Server (NTRS)

    Tarditi, A. G.; George, J. A.; Miley, G. H.; Scott, J. H.

    2013-01-01

    Fission fragment direct energy conversion has been considered in the past for the purpose of increasing nuclear power plant efficiency and for advanced space propulsion. Since the fragments carry electric charge (typically in the order of 20 e) and have 100 MeV-range kinetic energy, techniques utilizing very high-voltage DC electrodes have been considered. This study is focused on a different approach: the kinetic energy of the charged fission fragments is converted into alternating current by means of a traveling wave coupling scheme (Traveling Wave Direct Energy Converter, TWDEC), thereby not requiring the utilization of high voltage technology. A preliminary feasibility analysis of the concept is introduced based on a conceptual level study and on a particle simulation model of the beam dynamics.

  6. Polymerase chain reaction-restriction fragment length polymorphism authentication of raw meats from game birds.

    PubMed

    Rojas, María; González, Isabel; Fajardo, Violeta; Martín, Irene; Hernández, Pablo E; García, Teresa; Martín, Rosario

    2008-01-01

    Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis has been applied to the identification of meats from quail (Coturnix coturnix), pheasant (Phasianus colchicus), red-legged partridge (Alectoris rufa), guinea fowl (Numida meleagris), capercaillie (Tetrao urogallus), Eurasian woodcock (Scolopax rusticola), woodpigeon (Columba palumbus), and song thrush (Turdus philomelos). PCR amplification was performed using a set of primers flanking a conserved region of approximately 720 base pairs (bp) from the mitochondrial 12S rRNA gene. Restriction site analysis based on sequence data from this DNA fragment permitted the selection of AluI and BfaI endonucleases for species identification. The restriction profiles obtained when amplicons were digested with the chosen enzymes allowed the unequivocal identification of all game bird species analyzed. However, the use of the PCR-RFLP technique described is limited to raw meat authentication. It is not suitable for cooked products because thermal treatment strongly accelerates DNA degradation leading to difficulties in amplifying the 720 bp fragment.

  7. Ecological study of social fragmentation, poverty, and suicide

    PubMed Central

    Whitley, Elise; Gunnell, David; Dorling, Daniel; Smith, George Davey

    1999-01-01

    Objectives To investigate the association between suicide and area based measures of deprivation and social fragmentation. Design Ecological study. Setting 633 parliamentary constituencies of Great Britain as defined in 1991. Main outcome measures Age and sex specific mortality rates for suicide and all other causes for 1981-92. Results Mortality from suicide and all other causes increased with increasing Townsend deprivation score, social fragmentation score, and abstention from voting in all age and sex groups. Suicide mortality was most strongly related to social fragmentation, whereas deaths from other causes were more closely associated with Townsend score. Constituencies with absolute increases in social fragmentation and Townsend scores between 1981 and 1991 tended to have greater increases in suicide rates over the same period. The relation between change in social fragmentation and suicide was largely independent of Townsend score, whereas the association with Townsend score was generally reduced after adjustment for social fragmentation. Conclusions Suicide rates are more strongly associated with measures of social fragmentation than with poverty at a constituency level. Key messagesPlace of residence may affect health, and mortality from most common diseases tends to be higher in areas characterised by low socioeconomic positionResearch dating back over 100 years suggests that social fragmentation may influencesuicideIn the 1980s and 1990s, parliamentary constituencies with high levels of social fragmentation had high rates of suicide, independent of deprivationConstituencies with the greatest increases in social fragmentation between 1981 and 1991 also had the greatest increases in suicide rates over the same periodAny targeting of suicide prevention may be more effective if aimed at socially fragmented rather than deprived areas PMID:10521194

  8. Rock fragment movement in shallow rill flow - A laboratory study

    NASA Astrophysics Data System (ADS)

    Becker, Kerstin; Wirtz, Stefan; Seeger, Manuel; Gronz, Oliver; Remke, Alexander; Iserloh, Thomas; Brings, Christine; Casper, Markus; Ries, Johannes B.

    2014-05-01

    Studies concerning rill erosion mainly deal with the erosion and transport of fine material. The transport of rock fragments is examined mostly for mountain rivers. But there are important differences between the conditions and processes in rivers and in rills: (1) In most cases, the river cuts into a coarse substrate, where fine material is sparse, whereas rill erosion occurs on arable land. So the main part of the substrate is fine material and only single rock fragments influence the processes. (2) In rivers, the water depth is relatively high. There are a lot of studies about hydraulic parameters in such flows, but there is almost nothing known about hydraulic conditions in surface runoff events of a few centimeters. Additionally, little information exists about the rock fragment movement as a part of rill erosion processes on arable land. This knowledge should be increased because rock fragments cause non-stationary water turbulences in rills, which enhance the erosive force of flowing water. Field experiments can only show the fact that a certain rock fragment has moved: The starting point and the final position can be estimated. But the moving path and especially the initiation of the movement is not detectable under field conditions. Hence, we developed a laboratory setup to analyze the movement of rock fragments depending on rock fragment properties (size, form), slope gradient, flow velocity and surface roughness. By observing the rock fragments with cameras from two different angles we are able (1) to measure the rotation angles of a rock fragment during the experiment and (2) to deduce different rock fragment movement patterns. On this poster we want to present the experimental setup, developed within the scope of a master thesis, and the results of these experiments.

  9. Global transformation and fate of SOA: Implications of Low Volatility SOA and Gas-Phase Fragmentation Reactions

    SciTech Connect

    Shrivastava, ManishKumar B.; Easter, Richard C.; Liu, Xiaohong; Zelenyuk, Alla; Singh, Balwinder; Zhang, Kai; Ma, Po-Lun; Chand, Duli; Ghan, Steven J.; Jiminez, J. L.; Zhang, Qibin; Fast, Jerome D.; Rasch, Philip J.; Tiitta, P.

    2015-05-16

    Secondary organic aerosols (SOA) are large contributors to fine particle loadings and radiative forcing, but are often represented crudely in global models. We have implemented three new detailed SOA treatments within the Community Atmosphere Model version 5 (CAM5) that allow us to compare the semi-volatile versus non-volatile SOA treatments (based on some of the latest experimental findings) and also investigate the effects of gas-phase fragmentation reactions. For semi-volatile SOA treatments, fragmentation reactions decrease simulated SOA burden from 7.5 Tg to 1.8 Tg. For the non-volatile SOA treatment with fragmentation, the burden is 3.1 Tg. Larger differences between non-volatile and semi-volatile SOA (upto a factor of 5) correspond to continental outflow over the oceans. Compared to a global dataset of surface Aerosol Mass Spectrometer measurements and the US IMPROVE network measurements, the non-volatile SOA with fragmentation treatment (FragNVSOA) agrees best at rural locations. Urban SOA is under-predicted but this may be due to the coarse model resolution. All our three revised treatments show much better agreement with aircraft measurements of organic aerosols (OA) over the N. American Arctic and sub-Arctic in spring and summer, compared to the standard CAM5 formulation. This is due to treating SOA precursor gases from biomass burning, and long-range transport of biomass burning OA at elevated levels. The revised model configuration that include fragmentation (both semi-volatile and non-volatile SOA) show much better agreement with MODIS AOD data over regions dominated by biomass burning during the summer, and predict biomass burning as the largest global source of OA followed by biogenic and anthropogenic sources. The non-volatile and semi-volatile configuration predict the direct radiative forcing of SOA as -0.5 W m-2 and -0.26 W m-2 respectively, at top of the atmosphere, which are higher than previously estimated by most models, but in reasonable

  10. Reaction between radicals and N-alkoxyamines As coordinated cleavage with fragmentation

    NASA Astrophysics Data System (ADS)

    Denisov, E. T.; Shestakov, A. F.

    2015-08-01

    Quantum chemical calculations of the enthalpy and activation energy of two reactions with MeO{2/⊙} attacking the CH- and CH2-groups of 2,2,6,6-tetramethylpiperidineoxy-2'-butane are performed. It is shown that the cleavage of hydrogen atoms is accompanied by coordinated breaking of N-O-bonds in the former case and C-O-bonds in the latter. Based on the obtained results, a new scheme is proposed for the cyclic mechanism behind the cleavage of chains on nitroxyl radicals in oxidizing hydrocarbons and polymers that agrees with experimental data. At the center of this cyclic mechanism lies the fast exothermic reaction between peroxyl radicals and N-alkoxyamine with the cleavage of H atoms and the coordinated fragmentation of molecules. Using the model of intersecting parabolas, an algorithm for calculating the enthalpies, activation energies, and rate constants of these reactions with the participation of alkyl, alkoxy, aminyl, peroxyl, phenoxyl, thiyl, and hydroxyl radicals is proposed.

  11. Physical and dynamical studies of meteors. [radar observation of fragmentation

    NASA Technical Reports Server (NTRS)

    Southworth, R. B.; Sekanina, Z.

    1974-01-01

    Distribution of meteors in streams detected in the synoptic-year meteor sample plus a study of the fragmentation characteristics of the synoptic-year meteor sample are presented. Population coefficients and dispersion coefficients were determined for each meteor stream. These two parameters serve to determine the number of definite members of the stream in the sample used, and to estimate the actual space density of meteor streams. From results of the fragmentation study, it appears that the main body of most radar meteors does not ablate fragments layer by layer, but collapses rather suddenly under dynamic pressures on the order of 0,0002 dynes/cm. Furthermore, it is believed that fragmentation does not cause a serious selection effect in the radar meteor data.

  12. Holliday junctions generate super-bright antibodies and antibody fragments in sortase-catalyzed reactions

    PubMed Central

    Li, Zeyang; Theile, Christopher S.; Chen, Guan-Yu; Bilate, Angelina M.; Duarte, Joao N.; Avalos, Ana M.; Fang, Tao; Barberena, Roberto; Sato, Shuji; Ploegh, Hidde L.

    2015-01-01

    Site-specific modification of proteins with fluorophores can render a protein fluorescent without compromising its function. To avoid self-quenching of multiple fluorophores installed in close proximity, we used Holliday junctions to label proteins site-specifically. Holliday junctions enable modification with multiple fluorophores at reasonably precise spacing. We designed a Holliday junction with three of its four arms modified with a fluorophore of choice and the remaining arm equipped with a dibenzocyclooctyne substituent to render it reactive with an azide-modified, fluorescent single domain antibody fragment or an intact immunoglobulin, produced in a sortase-catalyzed reaction. We conclude that fluorescent Holliday junctions improve fluorescence yields for both single domain and full-sized antibodies, without deleterious effects on antigen binding. PMID:26252716

  13. Fission Cross Sections and Fission-Fragment Mass Yields via the Surrogate Reaction Method

    SciTech Connect

    Jurado, B.; Kessedjian, G.; Aiche, M.; Barreau, G.; Bidaud, A.; Czajkowski, S.; Dassie, D.; Haas, B.; Mathieu, L.; Osmanov, B.; Ahmad, I.

    2008-04-17

    The surrogate reaction method is a powerful tool to infer neutron-induced data of short-lived nuclei. After a short overview of the experimental techniques employed in the present surrogate experiments, we will concentrate on a recent measurement to determine neutron-induced fission cross sections for the actinides {sup 242,243}Cm and {sup 241}Am. The latest direct neutron-induced measurement for the {sup 243}Cm fission cross section is questioned by our results, since there are differences of more than 60% in the 0.7 to 7 MeV neutron energy range. Our experimental set-up has also enabled us to measure for the first time the fission fragment ''pseudo-mass'' distributions of {sup 243,244,245}Cm and {sup 242}Am compound nuclei in the excitation energy range from a few MeV to about 25 MeV.

  14. Light Charged Particles and Intermediate Mass Fragments from the Reactions 486, 550, 640, and 730 Mev KRYPTON-86 + COPPER-63

    NASA Astrophysics Data System (ADS)

    Boger, John Thomas

    1992-01-01

    A detailed study has been made of the reaction ^{86}Kr + ^ {63}Cu at incident energies of 486, 550, 640, and 730 MeV. Measurements include cross sections, angular distributions, and energy spectra for light charged particles (^{1,2,3}H and ^4He), intermediate mass fragments (IMF) (4 <= Z <= 17), and heavy fragments (Z >= 18). Coincidences between light charged particles and between particles and fragments have also been measured to obtain exclusive cross sections, energy spectra, and angular distributions. Statistical model analysis of the energy spectra for ^1 H and ^4He detected in coincidence with the fragments has allowed estimation of ^1 H and ^4He multiplicities associated with the evaporation residues, fragments, and composite nuclei prior to scission. In particular, the light charged particle multiplicities for the IMF's have allowed for the derivation of their primary masses. This in turn has permitted refined measurements of the kinetic energies of the primary IMF's. The ^{86}Kr bombarding energies were selected so that the excitation energies of the composite nuclei (^{149} Tb*) were matched to those of other entrance channel reactions that produce the same composite nuclei. A close comparison of cross sections, energy spectra, angular distributions, and particle multiplicities for these matched entrance channels has provided the means for a detailed test of the Bohr Independence Hypothesis. Results of this comparison indicate extensive shape and thermal equilibration of the composite nuclei over the excitation energy range of 128 to 231 MeV. This conclusion is reached even for nuclear systems whose decay lifetimes are expected to be similar to their relaxation times. For the 640 MeV ^{86} Kr + ^{63}Cu reaction, cross sections were measured for IMF's of 4 <= Z <= 17 in singles and in coincidence with heavy fragments. Three sources for IMF production have been identified: (1) asymmetric binary fission, (2) sequential binary fission, and (3) simultaneous

  15. Experimental and numerical study on fragmentation of steel projectiles

    NASA Astrophysics Data System (ADS)

    Råkvaag, K. G.; Børvik, T.; Hopperstad, O. S.; Westermann, I.

    2012-08-01

    A previous experimental study on penetration and perforation of circular Weldox 460E target plates with varying thicknesses struck by blunt-nose projectiles revealed that fragmentation of the projectile occurred if the target thickness or impact velocity exceeded a certain value. Thus, numerical simulations that do not account for fragmentation during impact can underestimate the perforation resistance of protective structures. Previous numerical studies have focused primarily on the target plate behaviour. This study considers the behaviour of the projectile and its possible fragmentation during impact. Hardened steel projectiles were launched at varying velocities in a series of Taylor tests. The impact events were captured using a high-speed camera. Fractography of the fragmented projectiles showed that there are several fracture mechanisms present during the fragmentation process. Tensile tests of the projectile material revealed that the hardened material has considerable variations in yield stress and fracture stress and strain. In the finite element model, the stress-strain behaviour from tensile tests was used to model the projectile material with solid elements and the modified Johnson-Cook constitutive relation. Numerical simulations incorporating the variations in material properties are capable of reproducing the experimental fracture patterns, albeit the predicted fragmentation velocities are too low.

  16. Global Transformation and Fate of Secondary Organic Aerosols: Implications of Low Volatility SOA and Gas-Phase Fragmentation Reactions

    NASA Astrophysics Data System (ADS)

    Shrivastava, M. B.; Easter, R. C.; Liu, X.; Zelenyuk, A.; Singh, B.; Zhang, K.; Ma, P. L.; Chand, D.; Ghan, S. J.; Jimenez, J. L.; Zhang, Q.; Fast, J. D.; Rasch, P. J.; Tiitta, P.

    2014-12-01

    Secondary organic aerosols (SOA) are often represented crudely in global models. We have implemented three new detailed SOA treatments within the Community Atmosphere Model version 5 (CAM5) that allow us to compare the semi-volatile versus non-volatile SOA treatments (based on some of the latest experimental findings) and also investigate the effects of gas-phase fragmentation reactions. For semi-volatile SOA treatments, fragmentation reactions decrease simulated SOA burden from 7.5 Tg to 1.8 Tg. For the non-volatile SOA treatment (with fragmentation), the burden is 3.1 Tg. Larger differences between non-volatile and semi-volatile SOA (upto a factor of 5) correspond to continental outflow over the oceans. Compared to a global dataset of surface Aerosol Mass Spectrometer measurements and the US IMPROVE network measurements, the non-volatile SOA with fragmentation treatment (FragNVSOA) agrees best at rural locations. Urban SOA is under-predicted but this may be due to the coarse model resolution. Our revised treatments show much better agreement with aircraft measurements of organic aerosols (OA) over the N. American Arctic and sub-Arctic in spring and summer, compared to the standard CAM5 formulation. This is due to treating SOA precursor gases from biomass burning, and long-range transport of biomass burning OA at elevated levels (also supported by satellite data), which undergoes less wet removal compared to the surface OA sources in the standard CAM5. Although the total simulated OA from biomass burning agrees better with aircraft measurements, recent field observations typically report lower SOA formation, suggesting that constraining the POA-SOA split from biomass burning should be the focus of future studies. The non-volatile and semi-volatile configurations predict the direct radiative forcing of SOA as -0.5 W m-2 and -0.26 W m-2 respectively, at top of the atmosphere, which are higher than previously estimated by most models, but in reasonable agreement with

  17. A thermodynamic molecular switch in biological systems: ribonuclease S' fragment complementation reactions.

    PubMed Central

    Chun, P W

    2000-01-01

    It is well known that essentially all biological systems function over a very narrow temperature range. Most typical macromolecular interactions show DeltaH degrees (T) positive (unfavorable) and a positive DeltaS degrees (T) (favorable) at low temperature, because of a positive (DeltaCp degrees /T). Because DeltaG degrees (T) for biological systems shows a complicated behavior, wherein DeltaG degrees (T) changes from positive to negative, then reaches a negative value of maximum magnitude (favorable), and finally becomes positive as temperature increases, it is clear that a deeper-lying thermodynamic explanation is required. This communication demonstrates that the critical factor is a temperature-dependent DeltaCp degrees (T) (heat capacity change) of reaction that is positive at low temperature but switches to a negative value at a temperature well below the ambient range. Thus the thermodynamic molecular switch determines the behavior patterns of the Gibbs free energy change and hence a change in the equilibrium constant, K(eq), and/or spontaneity. The subsequent, mathematically predictable changes in DeltaH degrees (T), DeltaS degrees (T), DeltaW degrees (T), and DeltaG degrees (T) give rise to the classically observed behavior patterns in biological reactivity, as may be seen in ribonuclease S' fragment complementation reactions. PMID:10620305

  18. A polymerase chain reaction-restriction fragment length polymorphism method for screening ZNF804A gene polymorphism (rs1344706) in patients with schizophrenia: a significant association.

    PubMed

    Sazci, Ali; Ozel, Mavi Deniz; Ergul, Emel; Yildiz, Mustafa

    2012-03-01

    The original ZNF804A rs1344706 risk variant was identified through genome-wide association studies as a risk factor for schizophrenia. Follow-up studies involving meta-analysis have confirmed that rs1344706 is a risk factor for schizophrenia as well as bipolar disorders. We describe here a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to genotype ZNF804A rs1344706 variant in patients with schizophrenia. We generated a 220 bp fragment through PCR and subsequently cleaved it by the restriction endonuclease BsaBI, creating two fragments of 114 and 106 bp. Upon change in the nucleotide from T to G, the 106 bp fragment is further cleaved by BsaBI, thus creating two fragments of 87 and 19 bp. As a result, when the 220 bp fragment is cleaved by BsaBI restriction endonuclease, the TT genotype yields two fragments of 114 and 106 bp, and TG genotype four fragments of 114, 106, 87, and 19 bp, and the GG genotype three fragments of 114, 87, and 19 bp. Thus, this is a simple, fast, and cost-effective method to genotype the ZNF804A rs1344706 risk variant. Using this method, we were able to replicate an association between ZNF804A rs1344706 variant and schizophrenia in a Turkish population. Stratification analysis of the population according to the gender showed an association that was statistically significant among overall schizophrenia and male schizophrenia and the risk T allele and TT genotype of the ZNF804A gene.

  19. Taxonomic and ecological discrimination of Fagaceae species based on internal transcribed spacer polymerase chain reaction-restriction fragment length polymorphism.

    PubMed

    Coutinho, João Paulo; Carvalho, Ana; Lima-Brito, José

    2014-11-26

    The internal transcribed spacer (ITS) of ribosomal DNA has been used to confirm taxonomic classifications and define phylogenies in several plant species following sequencing or polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques. In this study, co-dominant ITS PCR-RFLP molecular markers were produced in 30 Fagaceae individuals belonging to the Castanea, Fagus and Quercus genera in order to assess the potential of this technique for taxonomic discrimination and determination of phylogenies. The complete ITS region (ITS1-5.8S rRNA-ITS2) was amplified in most of the Fagaceae individuals as a single fragment of ∼700 bp. The ITS amplified products were digested with nine restriction enzymes, but only four (HaeIII, HpaII, TaqI and Sau96I) produced polymorphic/discriminative patterns. The total expected heterozygosity (HE) was 20.31 % and the gene diversity (I), 32.97 %. The ITS polymorphism was higher within the Quercus genus (85.3 %). The ITS PCR-RFLP markers clustered the Fagaceae species according to genus or infrageneric group (in the case of Quercus sp. individuals). Five oaks did not cluster in line with the adopted infrageneric classification, but three of these were grouped according to their actual ecological distributions. The ITS PCR-RFLP markers indicated their potential for phylogenetic studies since all Fagaceae individuals were discriminated according to genus, and most of the oaks were clustered according to infrageneric group or ecological area.

  20. Genetic divergence between Mexican Opuntia accessions inferred by polymerase chain reaction-restriction fragment length polymorphism analysis.

    PubMed

    Samah, S; Valadez-Moctezuma, E; Peláez-Luna, K S; Morales-Manzano, S; Meza-Carrera, P; Cid-Contreras, R C

    2016-06-03

    Molecular methods are powerful tools in characterizing and determining relationships between plants. The aim of this study was to study genetic divergence between 103 accessions of Mexican Opuntia. To accomplish this, polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis of three chloroplast intergenic spacers (atpB-rbcL, trnL-trnF, and psbA-trnH), one chloroplast gene (ycf1), two nuclear genes (ppc and PhyC), and one mitochondrial gene (cox3) was conducted. The amplified products from all the samples had very similar molecular sizes, and there were only very small differences between the undigested PCR amplicons for all regions, with the exception of ppc. We obtained 5850 bp from the seven regions, and 136 fragments were detected with eight enzymes, 37 of which (27.2%) were polymorphic. We found that 40% of the fragments from the chloroplast regions were polymorphic, 9.8% of the bands detected in the nuclear genes were polymorphic, and 20% of the bands in the mitochondrial locus were polymorphic. trnL-trnF and psbA-trnH were the most variable regions. The Nei and Li/Dice distance was very short, and ranged from 0 to 0.12; indeed, 77 of the 103 genotypes had the same genetic profile. All the xoconostle accessions (acidic fruits) were grouped together without being separated from three genotypes of prickly pear (sweet fruits). We assume that the genetic divergence between prickly pears and xoconostles is very low, and question the number of Opuntia species currently considered in Mexico.

  1. Effect of projectile breakup on fission-fragment mass distributions in the Li,76 + 238U reactions

    NASA Astrophysics Data System (ADS)

    Santra, S.; Pal, A.; Rath, P. K.; Nayak, B. K.; Singh, N. L.; Chattopadhyay, D.; Behera, B. R.; Singh, Varinderjit; Jhingan, A.; Sugathan, P.; Golda, K. S.; Sodaye, S.; Appannababu, S.; Prasad, E.; Kailas, S.

    2014-12-01

    Background: Detailed studies on the effect of the breakup of weakly bound projectile on fission are scarce. Distinguishing the events of compound nuclear (CN) fission from the breakup or transfer induced fission to understand the properties of measured fission fragments is difficult but desirable. Purpose: To investigate the effect of projectile breakup and its breakup threshold energy on fission-fragment (FF) mass distributions and folding angle distributions for Li,76 + 238U reactions and find out the differences in the properties of the fission events produced by complete fusion (CF) from the total fusion (TF). Methods: The FF mass and folding angle distributions have been measured at energies around the Coulomb barrier using gas detectors by time-of-flight technique. The results are compared with the ones involving tightly bound projectiles as well as predictions from systematics to bring out the effect of the breakup. Results: A sharp increase in the peak to valley (P:V) ratio of FF mass distribution with the decrease in bombarding energy for Li,76 + 238U reactions is observed when all events are assumed to be CN fission. As the beam energy falls through the fusion barrier, the full width half maximum (FWHM) of the FF folding angle distribution is found to increase at sub-barrier energies, unlike the reactions involving tightly bound projectiles where a linear decrease in FWHM is expected. By selecting pure CN events from the scatter plot of the velocity components of the composite nuclei, the energy dependence of the deduced FWHM is found to be consistent with the ones involving tightly bound projectiles. Similarly, the P:V ratio obtained for the selected CN events is consistent with the theoretical calculations as well as the experimental data for the proton induced reaction forming similar CN. Conclusions: The presence of projectile breakup induced fission and a relatively low breakup threshold for 6Li compared to 7Li explains the observed differences in

  2. Frequent occurrence of T cell–mediated late reactions revealed by atopy patch testing with hypoallergenic rBet v 1 fragments

    PubMed Central

    Campana, Raffaela; Moritz, Katharina; Marth, Katharina; Neubauer, Angela; Huber, Hans; Henning, Rainer; Blatt, Katharina; Hoermann, Gregor; Brodie, Tess M.; Kaider, Alexandra; Valent, Peter; Sallusto, Federica; Wöhrl, Stefan; Valenta, Rudolf

    2015-01-01

    Background Late allergic reactions are common in the course of allergen-specific immunotherapy and even occur with allergy vaccines with reduced IgE reactivity. Objective We sought to study atopy patch test (APT) reactions and T-cell responses to the recombinant birch pollen allergen Bet v 1 and recombinant hypoallergenic T-cell epitope–containing Bet v 1 fragments in patients with birch pollen allergy with and without atopic dermatitis (AD). Methods A clinical study was conducted in 15 patients with birch pollen allergy with AD (group 1), 5 patients with birch pollen allergy without AD (group 2), 5 allergic patients without birch pollen allergy (group 3), and 5 nonallergic subjects (group 4) by performing skin prick tests and APTs with rBet v 1 and hypoallergenic rBet v 1 fragments. T-cell, cutaneous lymphocyte antigen (CLA)+ and CCR4+ T-cell and cytokine responses were studied by thymidine uptake, carboxyfluorescein diacetate succinimidyl ester staining, and Luminex technology, respectively. Results rBet v 1 and hypoallergenic rBet v 1 fragments induced APT reactions in not only most of the patients with birch pollen allergy with AD (11/15) but also in most of those without AD (4/5). Patients with birch pollen allergy with AD had higher Bet v 1–specific proliferation of CLA+ and CCR4+ T cells compared with patients with birch pollen allergy without AD. There were no differences in Bet v 1–specific CLA+ and CCR4+ proliferation and cytokine secretion in patients with and without APT reactions. Conclusion Hypoallergenic rBet v 1 fragments induce T cell–dependent late reactions not only in patients with birch pollen allergy with AD but also in those without AD, which can be determined based on APT results but not based on in vitro parameters. PMID:26518092

  3. An Experimental Study of Launch Vehicle Propellant Tank Fragmentation

    NASA Technical Reports Server (NTRS)

    Richardson, Erin; Jackson, Austin; Hays, Michael; Bangham, Mike; Blackwood, James; Skinner, Troy; Richman, Ben

    2014-01-01

    In order to better understand launch vehicle abort environments, Bangham Engineering Inc. (BEi) built a test assembly that fails sample materials (steel and aluminum plates of various alloys and thicknesses) under quasi-realistic vehicle failure conditions. Samples are exposed to pressures similar to those expected in vehicle failure scenarios and filmed at high speed to increase understanding of complex fracture mechanics. After failure, the fragments of each test sample are collected, catalogued and reconstructed for further study. Post-test analysis shows that aluminum samples consistently produce fewer fragments than steel samples of similar thickness and at similar failure pressures. Video analysis shows that there are several failure 'patterns' that can be observed for all test samples based on configuration. Fragment velocities are also measured from high speed video data. Sample thickness and material are analyzed for trends in failure pressure. Testing is also done with cryogenic and noncryogenic liquid loading on the samples. It is determined that liquid loading and cryogenic temperatures can decrease material fragmentation for sub-flight thicknesses. A method is developed for capture and collection of fragments that is greater than 97 percent effective in recovering sample mass, addressing the generation of tiny fragments. Currently, samples tested do not match actual launch vehicle propellant tank material thicknesses because of size constraints on test assembly, but test findings are used to inform the design and build of another, larger test assembly with the purpose of testing actual vehicle flight materials that include structural components such as iso-grid and friction stir welds.

  4. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Y.T.

    1993-12-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  5. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Yuan T.

    1991-03-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  6. Fission fragment angular distributions in the reactions {sup 16}O+{sup 188}Os and {sup 28}Si+{sup 176}Yb

    SciTech Connect

    Tripathi, R.; Sudarshan, K.; Sharma, S. K.; Reddy, A. V. R.; Pujari, P. K.; Goswami, A.; Ramachandran, K.

    2009-06-15

    Fission fragment angular distributions have been measured in the reactions {sup 16}O+{sup 188}Os and {sup 28}Si+{sup 176}Yb to investigate the contribution from noncompound nucleus fission. Parameters for statistical model calculations were fixed using fission cross section data in the {sup 16}O+{sup 188}Os reaction. Experimental anisotropies were in reasonable agreement with those calculated using the statistical saddle point model for both reactions. The present results are also consistent with those of mass distribution studies in the fission of {sup 202}Po, formed in the reactions with varying entrance channel mass asymmetry. However, the present studies do not show a large fusion hindrance as reported in the pre-actinide region based on the measurement of evaporation residue cross section.

  7. Implications of Low Volatility SOA and Gas-Phase Fragmentation Reactions on SOA Loadings and their Spatial and Temporal Evolution in the Atmosphere

    SciTech Connect

    Shrivastava, ManishKumar B.; Zelenyuk, Alla; Imre, Dan; Easter, Richard C.; Beranek, Josef; Zaveri, Rahul A.; Fast, Jerome D.

    2013-04-27

    Recent laboratory and field measurements by a number of groups show that secondary organic aerosol (SOA) evaporates orders of magnitude slower than traditional models assume. In addition, chemical transport models using volatility basis set (VBS) SOA schemes neglect gas-phase fragmentation reactions, which are known to be extremely important. In this work, we present modeling studies to investigate the implications of non-evaporating SOA and gas-phase fragmentation reactions. Using the 3-D chemical transport model, WRF-Chem, we show that previous parameterizations, which neglect fragmentation during multi-generational gas-phase chemistry of semi-volatile/inter-mediate volatility organics ("aging SIVOC"), significantly over-predict SOA as compared to aircraft measurements downwind of Mexico City. In sharp contrast, the revised models, which include gas-phase fragmentation, show much better agreement with measurements downwind of Mexico City. We also demonstrate complex differences in spatial SOA distributions when we transform SOA to non-volatile secondary organic aerosol (NVSOA) to account for experimental observations. Using a simple box model, we show that for same amount of SOA precursors, earlier models that do not employ multi-generation gas-phase chemistry of precursors ("non-aging SIVOC"), produce orders of magnitude lower SOA than "aging SIVOC" parameterizations both with and without fragmentation. In addition, traditional absorptive partitioning models predict almost complete SOA evaporation at farther downwind locations for both "non-aging SIVOC" and "aging SIVOC" with fragmentation. In contrast, in our revised approach, SOA transformed to NVSOA implies significantly higher background concentrations as it remains in particle phase even under highly dilute conditions. This work has significant implications on understanding the role of multi-generational chemistry and NVSOA formation on SOA evolution in the atmosphere.

  8. Production of Neutron-Unbound States in Intermediate - Fragments from Nitrogen + Silver Reactions at E/a = 35 Mev

    NASA Astrophysics Data System (ADS)

    Heilbronn, Lawrence Harvey

    The populations of neutron-unbound states and of bound states in intermediate-mass fragments have been measured at 15^circ, 31 ^circ, and 64^circ from the ^{14}N + Ag reaction at E/A = 35 MeV. The data are identified in terms of the reaction mechanism producing them, which is either a deep-inelastic mechanism or a quasielastic mechanism. In order to test the assumption that the deep -inelastic data are produced from a thermal source, the unbound-state/bound-state population ratios of deep-inelastic fragments are compared to the predictions of a thermal sequential decay model. Most, but not all, of the deep -inelastic population ratios are fitted with model calculations that assume a source temperature between 2.5 and 3.4 MeV. Three or more populations from the same isotope were measured for ^{13}C, ^ {12}B, and ^{10} Be. The deep-inelastic populations from ^{13}C and ^{10 }Be were fitted with a single temperature, while the deep-inelastic populations from ^ {12}B were not fitted. There is enough of the deep-inelastic data that is not fitted with the predictions of a thermal model that the assumption of a thermal source for the production of deep-inelastic fragments may be incorrect, or there may be other effects present which alter the thermal properties of the data. The dependence of the unbound-state/bound-state population ratio on the fragment kinetic energy shows a difference between the quasielastic and deep-inelastic data. For quasielastic fragments whose mass is near the mass of the beam, the ratio decreases towards zero as the fragment velocity approaches the beam velocity. In contrast, the ratio for half-beam mass quasielastic fragments is constant or only slightly decreasing as the kinetic energy increases. The ratio for deep-inelastic fragments is approximately constant as a function of kinetic energy, independent of fragment mass. The amount of feeding from several neutron-unbound channels into bound states is measured and compared to the sequential

  9. Transitions from functionalization to fragmentation reactions of laboratory secondary organic aerosol (SOA) generated from the OH oxidation of alkane precursors.

    PubMed

    Lambe, Andrew T; Onasch, Timothy B; Croasdale, David R; Wright, Justin P; Martin, Alexander T; Franklin, Jonathan P; Massoli, Paola; Kroll, Jesse H; Canagaratna, Manjula R; Brune, William H; Worsnop, Douglas R; Davidovits, Paul

    2012-05-15

    Functionalization (oxygen addition) and fragmentation (carbon loss) reactions governing secondary organic aerosol (SOA) formation from the OH oxidation of alkane precursors were studied in a flow reactor in the absence of NO(x). SOA precursors were n-decane (n-C10), n-pentadecane (n-C15), n-heptadecane (n-C17), tricyclo[5.2.1.0(2,6)]decane (JP-10), and vapors of diesel fuel and Southern Louisiana crude oil. Aerosol mass spectra were measured with a high-resolution time-of-flight aerosol mass spectrometer, from which normalized SOA yields, hydrogen-to-carbon (H/C) and oxygen-to-carbon (O/C) ratios, and C(x)H(y)+, C(x)H(y)O+, and C(x)H(y)O(2)+ ion abundances were extracted as a function of OH exposure. Normalized SOA yield curves exhibited an increase followed by a decrease as a function of OH exposure, with maximum yields at O/C ratios ranging from 0.29 to 0.74. The decrease in SOA yield correlates with an increase in oxygen content and decrease in carbon content, consistent with transitions from functionalization to fragmentation. For a subset of alkane precursors (n-C10, n-C15, and JP-10), maximum SOA yields were estimated to be 0.39, 0.69, and 1.1. In addition, maximum SOA yields correspond with a maximum in the C(x)H(y)O+ relative abundance. Measured correlations between OH exposure, O/C ratio, and H/C ratio may enable identification of alkane precursor contributions to ambient SOA.

  10. Mechanisms and kinetics of noncatalytic ether reaction in supercritical water. 2. Proton-transferred fragmentation of dimethyl ether to formaldehyde in competition with hydrolysis.

    PubMed

    Nagai, Yasuharu; Matubayasi, Nobuyuki; Nakahara, Masaru

    2005-04-28

    Noncatalytic reaction pathways and rates of dimethyl ether (DME) in supercritical water are determined in a tube reactor made of quartz according to liquid- and gas-phase 1H and 13C NMR observations. The reaction is studied at two concentrations (0.1 and 0.5 M) in supercritical water at 400 degrees C and over a water-density range of 0.1-0.6 g/cm3. The supercritical water reaction is compared with the neat one (in the absence of solvent) at 0.1 M and 400 degrees C. DME is found to decompose through (i) the proton-transferred fragmentation to methane and formaldehyde and (ii) the hydrolysis to methanol. Formaldehyde from reaction (i) is consecutively subjected to four types of redox reactions. Two of them proceed even without solvent: (iii) the unimolecular proton-transferred decarbonylation forming hydrogen and carbon monoxide and (iv) the bimolecular self-disproportionation generating methanol and carbon monoxide. When the solvent water is present, two additional paths are open: (v) the bimolecular self-disproportionation of formaldehyde with reactant water, producing methanol and formic acid, and (vi) the bimolecular cross-disproportionation between formaldehyde and formic acid, yielding methanol and carbonic acid. Methanol is produced through the three types of disproportionations (iv)-(vi) as well as the hydrolysis (ii). The presence of solvent water decelerates the proton-transferred fragmentation of DME; the rate constant is reduced by 40% at 0.5 g/cm3. This is caused by the suppression of low-frequency concerted motion corresponding to the reaction coordinate for the simultaneous C-O bond scission and proton transfer from one methyl carbon to the other. In contrast to the proton-transferred fragmentation, the hydrolysis of DME is markedly accelerated by increasing the water density. The latter becomes more important than the former in supercritical water at densities greater than 0.5 g/cm3.

  11. Theoretical Studies of Reaction Surfaces

    DTIC Science & Technology

    2007-11-02

    31 Aug 97 4. TITLE AND SUBTITLE 5 . FUNDING NUMBERS AASERT93 THEORETICAL STUDIES OF REACTION SURFACES F49620-93-1-0556 3484/XS 6. AUTHOR(S) 61103D DR...DUNCAN AVE ROOM B115 BOLLING AFB DC 20332- 8050 DR MICHAEL R. BERMAN 11. SUPPLEMENTARY NOTES 12a. DISTRIBUTION i AVAILABILITY STATEMENT Approved f or pill...reaction14 , and solvation of electrolytes1 5 . The EFP method described in the previous section has one drawback: the repulsive 3 potential relies on

  12. Luciferase fragment complementation imaging in preclinical cancer studies

    PubMed Central

    Lake, Madryn C.; Aboagye, Eric O.

    2014-01-01

    The luciferase fragment complementation assay (LFCA) enables molecular events to be non-invasively imaged in live cells in vitro and in vivo in a comparatively cheap and safe manner. It is a development of previous enzyme complementation assays in which reporter genes are split into two, individually enzymatically inactive, fragments that are able to complement one another upon interaction. This complementation can be used to externally visualize cellular activities. In recent years, the number of studies which have used LFCAs to probe questions relevant to cancer have increased, and this review summarizes the most significant and interesting of these. In particular, it focuses on work conducted on the epidermal growth factor, nuclear and chemokine receptor families, and intracellular signaling pathways, including IP3, cAMP, Akt, cMyc, NRF2 and Rho GTPases. LFCAs which have been developed to image DNA methylation and detect RNA transcripts are also discussed. PMID:25594026

  13. Wavefront reconstruction with pupil fragmentation: study of a simple case

    NASA Astrophysics Data System (ADS)

    Bonnefond, Sylvain; Tallon, Michel; Le Louarn, Miska; Madec, Pierre-Yves

    2016-07-01

    The use of smaller subapertures on some recent adaptive optics (AO) systems seems to yield difficulties in wavefront reconstruction, known as spider effect or pupil fragmentation: the size of the subapertures is small enough so that some of them are masked by the telescope spider, dividing the pupil into disconnected domains. In particular, this problem will arise on the E-ELT.We have studied pure wavefront reconstruction on a Shack-Hartmann wavefront sensor, for a simplified AO system similar to VLT/SPHERE in size, with and without pupil fragmentation, and compared the performance of various wavefront reconstructors for different signal-to-noise ratios, using priors (minimum variance) or not (least-squares), and with different assumptions for the damaged wavefront measurements. The missing measurements have been either discarded (corresponding subapertures are not active), replaced by zeros, or interpolated by preserving the loop continuity property of the gradients (curl operator). Priors have been introduced using the FrIM (Fractal Iterative Method) algorithm. In our perfect conditions, we show that no method allows the full recovery from the pupil fragmentation, that minimum variance always gives the best performance, especially the one without any interpolation. On the opposite, the performance with least-squares somewhat improves when correcting for the missing measurements. In this latter case, preserving the curl property of the gradient is preferable only for very low measurement noise.

  14. Limits of a rapid identification of common Mediterranean sandflies using polymerase chain reaction-restriction fragment length polymorphism

    PubMed Central

    Bounamous, Azzedine; Lehrter, Véronique; Hadj-Henni, Leila; Delecolle, Jean-Claude; Depaquit, Jérôme

    2014-01-01

    A total of 131 phlebotomine Algerian sandflies have been processed in the present study. They belong to the species Phlebotomus bergeroti, Phlebotomus alexandri, Phlebotomus sergenti, Phlebotomus chabaudi, Phlebotomus riouxi, Phlebotomus perniciosus, Phlebotomus longicuspis, Phlebotomus perfiliewi, Phlebotomus ariasi, Phlebotomus chadlii, Sergentomyia fallax, Sergentomyia minuta, Sergentomyia antennata, Sergentomyia schwetzi, Sergentomyia clydei, Sergentomyia christophersi and Grassomyia dreyfussi. They have been characterised by sequencing of a part of the cytochrome b (cyt b), t RNA serine and NADH1 on the one hand and of the cytochrome C oxidase I of the mitochondrial DNA (mtDNA) on the other hand. Our study highlights two sympatric populations within P. sergenti in the area of its type-locality and new haplotypes of P. perniciosus and P. longicuspis without recording the specimens called lcx previously found in North Africa. We tried to use a polymerase chain reaction-restriction fragment length polymorphism method based on a combined double digestion of each marker. These method is not interesting to identify sandflies all over the Mediterranean Basin. PMID:24936911

  15. Polymerase chain reaction-restriction fragment-length polymorphism method to distinguish Liriomyza huidobrensis from L. Langei (Diptera: Agromyzidae) applied to three recent leafminer invasions.

    PubMed

    Scheffer, S J; Wijesekara, A; Visser, D; Hallett, R H

    2001-10-01

    A molecular method is presented for differentiating the morphologically cryptic leafminers Liriomyza langei Frick and L. huidobrensis (Blanchard). This method requires polymerase chain reaction (PCR) amplification of a 1031-bp region of mitochondrial cytochrome oxidase DNA followed by restriction fragment analysis using the restriction enzymes SpeI and EcoRV. Spel cuts the mitochondrial fragment of L. langei into two fragments, but does not cut the L. huidobrensis fragment. EcoRV cuts the L. huidobrensis fragment into two fragments, but does not cut the L. langei fragment. This PCR-restriction fragment-length polymorphism (RFLP) method is faster and less costly than DNA sequencing,which is currently the only other way to differentiate these two species. We apply the method to samples from recently introduced leafminer populations in Sri Lanka, Canada, and South Africa and find that the invasive leafminer in all three locations is L. huidobrensis.

  16. Spectroscopy of exotic 123,125Ag produced in fragmentation reactions

    NASA Astrophysics Data System (ADS)

    Stefanescu, I.; Walters, W. B.; Hoteling, N.; Tomlin, B.; Mantica, P. F.; Pereira, J.; Becerril, A.; Fleckenstein, T.; Hecht, A. A.; Lorusso, G.; Quinn, M.; Pinter, J. S.; Stoker, J. B.

    2008-04-01

    We extended the experimental knowledge in the mass-region around 132Sn by identifying the decay of high-spin isomers in the exotic odd-mass 123,125Ag. The two isotopes were produced at the NSCL laboratory by projectile fragmentation of a 136Xe beam at 120MeV/u directed onto a thick Be target. The NSCL Beta Counting System, was used identify secondary beam fragments. Prompt and delayed gamma-rays following the deexcitation of the fragments were detected with the SEGA array. Partial level schemes for 123,125Ag are proposed for the first time. The observed states show single-particle characteristics, indicating strong Z=50 and N=82 shell gaps and also support the proposed weakened nucleon-nucleon interaction in this mass-region.

  17. Native-state hydrogen-exchange studies of a fragment complex can provide structural information about the isolated fragments

    PubMed Central

    Chakshusmathi, G.; Ratnaparkhi, Girish S.; Madhu, P. K.; Varadarajan, R.

    1999-01-01

    Ordered protein complexes are often formed from partially ordered fragments that are difficult to structurally characterize by conventional NMR and crystallographic techniques. We show that concentration-dependent hydrogen exchange studies of a fragment complex can provide structural information about the solution structures of the isolated fragments. This general methodology can be applied to any bimolecular or multimeric system. The experimental system used here consists of Ribonuclease S, a complex of two fragments of Ribonuclease A. Ribonuclease S and Ribonuclease A have identical three-dimensional structures but exhibit significant differences in their dynamics and stability. We show that the apparent large dynamic differences between Ribonuclease A and Ribonuclease S are caused by small amounts of free fragments in equilibrium with the folded complex, and that amide exchange rates in Ribonuclease S can be used to determine corresponding rates in the isolated fragments. The studies suggest that folded RNase A and the RNase S complex exhibit very similar dynamic behavior. Thus cleavage of a protein chain at a single site need not be accompanied by a large increase in flexibility of the complex relative to that of the uncleaved protein. PMID:10393919

  18. Interfacial Reaction Studies Using ONIOM

    NASA Technical Reports Server (NTRS)

    Cardelino, Beatriz H.

    2003-01-01

    In this report, we focus on the calculations of the energetics and chemical kinetics of heterogeneous reactions for Organometallic vapor phase epitaxy (OMVPE). The work described in this report builds upon our own previous thermochemical and chemical kinetics studies. The first of these articles refers to the prediction of thermochemical properties, and the latter one deals with the prediction of rate constants for gaseous homolytic dissociation reactions. The calculations of this investigation are at the microscopic level. The systems chosen consisted of a gallium nitride (GaN) substrate, and molecular nitrogen (N2) and ammonia (NH3) as adsorbants. The energetics for the adsorption and the adsorbant dissociation processes were estimated, and reaction rate constants for the dissociation reactions of free and adsorbed molecules were predicted. The energetics for substrate decomposition was also computed. The ONIOM method, implemented in the Gaussian98 program, was used to perform the calculations. This approach has been selected since it allows dividing the system into two layers that can be treated at different levels of accuracy. The atoms of the substrate were modeled using molecular mechanics6 with universal force fields, whereas the adsorbed molecules were approximated using quantum mechanics, based on density functional theory methods with B3LYP functionals and 6-311G(d,p) basis sets. Calculations for the substrate were performed in slabs of several unit cells in each direction. The N2 and NH3 adsorbates were attached to a central location at the Ga-lined surface.

  19. Studies of complex fragment emission in heavy ion reactions

    SciTech Connect

    Charity, R.J.; Sobotka, L.G.

    1991-09-04

    This report discusses the following topics: High energy photon production in a HI collision; the mechanism for the disassembly of excited {sup 16}O projectiles into four alpha particles; the disassembly of excited {sup 28}Si projectiles; large pre-fission multiplicities from temperature; dependent friction and fission barriers; multiplicity correlations; molecular beam induced fusion; dwarf ball and wall; mini wall; and computer and local data acquisition systems.

  20. Measurement and verification of positron emitter nuclei generated at each treatment site by target nuclear fragment reactions in proton therapy

    SciTech Connect

    Miyatake, Aya; Nishio, Teiji; Ogino, Takashi; Saijo, Nagahiro; Esumi, Hiroyasu; Uesaka, Mitsuru

    2010-08-15

    Purpose: The purpose of this study is to verify the characteristics of the positron emitter nuclei generated at each treatment site by proton irradiation. Methods: Proton therapy using a beam on-line PET system mounted on a rotating gantry port (BOLPs-RGp), which the authors developed, is provided at the National Cancer Center Kashiwa, Japan. BOLPs-RGp is a monitoring system that can confirm the activity distribution of the proton irradiated volume by detection of a pair of annihilation gamma rays coincidentally from positron emitter nuclei generated by the target nuclear fragment reactions between irradiated proton nuclei and nuclei in the human body. Activity is measured from a start of proton irradiation to a period of 200 s after the end of the irradiation. The characteristics of the positron emitter nuclei generated in a patient's body were verified by the measurement of the activity distribution at each treatment site using BOLPs-RGp. Results: The decay curves for measured activity were able to be approximated using two or three half-life values regardless of the treatment site. The activity of half-life value of about 2 min was important for a confirmation of the proton irradiated volume. Conclusions: In each proton treatment site, verification of the characteristics of the generated positron emitter nuclei was performed by using BOLPs-RGp. For the monitoring of the proton irradiated volume, the detection of {sup 15}O generated in a human body was important.

  1. Molecular Epidemiology of Leptospirosis in Northern Iran by Nested Polymerase Chain Reaction/Restriction Fragment Length Polymorphism and Sequencing Methods

    PubMed Central

    Zakeri, Sedigheh; Sepahian, Neda; Afsharpad, Mandana; Esfandiari, Behzad; Ziapour, Peyman; Djadid, Navid D.

    2010-01-01

    This study was conducted to investigate the prevalence of Leptospira species in Mazandaran Province of Iran by using nested polymerase chain reaction (PCR)/restriction fragment length polymorphism (RFLP) methods and sequencing analysis. Blood samples (n = 119) were collected from humans suspected of having leptospirosis from different parts of the province in 2007. By using an indirect immunofluorescent antibody test (IFAT), we determined that 35 (29.4%) of 119 suspected cases had leptospiral antibody titers ≥ 1:80, which confirmed the diagnosis of leptospirosis. Nested PCR assay also determined that 60 (50.4%) of 119 samples showed Leptospira infection. Furthermore, 44 (73.3%) of 60 confirmed leptospirosis amplified products were subjected to sequencing analysis. Sequence alignment identified L. interrogans, L. kirschneri, and L. wolffii species. All positive cases diagnosed by IFAT or PCR were in patients who reported contact with animals, high-risk occupational activities, and exposure to contaminated water. Therefore, it is important to increase attention about this disease among physicians and to strengthen laboratory capacity for its diagnosis in infected patients in Iran. PMID:20439973

  2. Polymerase chain reaction-restriction fragment length polymorphism analysis: a simple method for species identification in food.

    PubMed

    Meyer, R; Höfelein, C; Lüthy, J; Candrian, U

    1995-01-01

    The polymerase chain reaction (PCR) technique was applied to meat species identification in marinated and heat-treated or fermented products and to the differentiation of closely related species. DNA was isolated from meat samples by using a DNA-binding resin and was subjected to PCR analysis. Primers used were complementary to conserved areas of the vertebrate mitochondrial cytochrome b (cytb) gene and yielded a 359 base-pair (bp) fragment, including a variable 307 bp region. Restriction endonuclease analysis based on sequence data of those fragments was used for differentiation among species. Restriction fragment length polymorphisms (RFLPs) were detected when pig, cattle, wild boar, buffalo, sheep, goat, horse, chicken, and turkey amplicons were cut with AluI, RsaI, TaqI, and HinfI. Analysis of sausages indicates the applicability of this approach to food products containing meat from 3 different species. The PCR-RFLP analytical method detected pork in heated meat mixtures with beef at levels below 1%, and the method was confirmed with porcine- and bovine-specific PCR assays by amplifying fragments of their growth hormone genes. Inter- and intraspecific differences of more than 22 animal species with nearly unknown cytb DNA sequences, including hoofed mammals (ungulates), and poultry were determined with PCR-RFLP typing by using 20 different endonucleases. This typing method allowed the discrimination of game meats, including stag, roe deer, chamois, moose, reindeer, kangaroo, springbok, and other antelopes in marinated and heat-treated products.

  3. Intraocular Lens Fragmentation Using Femtosecond Laser: An In Vitro Study

    PubMed Central

    Bala, Chandra; Shi, Jeffrey; Meades, Kerrie

    2015-01-01

    Purpose: To transect intraocular lenses (IOLs) using a femtosecond laser in cadaveric human eyes. To determine the optimal in vitro settings, to detect and characterize gasses or particles generated during this process. Methods: A femtosecond laser was used to transect hydrophobic and hydrophilic acrylic lenses. The settings required to enable easy separation of the lens fragment were determined. The gasses and particles generated were analysed using gas chromatography mass spectrometer (GC-MS) and total organic carbon analyzer (TOC), respectively. Results: In vitro the IOL fragments easily separated at the lowest commercially available energy setting of 1 μJ, 8-μm spot, and 2-μm line separation. No particles were detected in the 0.5- to 900-μm range. No significant gasses or other organic breakdown by products were detected at this setting. At much higher energy levels 12 μJ (4 × 6 μm spot and line separation) significant pyrolytic products were detected, which could be harmful to the eye. In cadaveric explanted IOL capsule complex the laser pulses could be applied through the capsule to the IOL and successfully fragment the IOL. Conclusion: IOL transection is feasible with femtosecond lasers. Further in vivo animal studies are required to confirm safety. Translational Relevance: In clinical practice there are a number of large intraocular lenses that can be difficult to explant. This in-vitro study examines the possibility of transecting the lasers quickly using femtosecond lasers. If in-vivo studies are successful, then this innovation could help ophthalmic surgeons in IOL explantation. PMID:26101721

  4. Identification of blood meal sources of Lutzomyia longipalpis using polymerase chain reaction-restriction fragment length polymorphism analysis of the cytochrome B gene.

    PubMed

    Soares, Vítor Yamashiro Rocha; Silva, Jailthon Carlos da; Silva, Kleverton Ribeiro da; Pires e Cruz, Maria do Socorro; Santos, Marcos Pérsio Dantas; Ribolla, Paulo Eduardo Martins; Alonso, Diego Peres; Coelho, Luiz Felipe Leomil; Costa, Dorcas Lamounier; Costa, Carlos Henrique Nery

    2014-06-01

    An analysis of the dietary content of haematophagous insects can provide important information about the transmission networks of certain zoonoses. The present study evaluated the potential of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the mitochondrial cytochrome B (cytb) gene to differentiate between vertebrate species that were identified as possible sources of sandfly meals. The complete cytb gene sequences of 11 vertebrate species available in the National Center for Biotechnology Information database were digested with Aci I, Alu I, Hae III and Rsa I restriction enzymes in silico using Restriction Mapper software. The cytb gene fragment (358 bp) was amplified from tissue samples of vertebrate species and the dietary contents of sandflies and digested with restriction enzymes. Vertebrate species presented a restriction fragment profile that differed from that of other species, with the exception of Canis familiaris and Cerdocyon thous. The 358 bp fragment was identified in 76 sandflies. Of these, 10 were evaluated using the restriction enzymes and the food sources were predicted for four: Homo sapiens (1), Bos taurus (1) and Equus caballus (2). Thus, the PCR-RFLP technique could be a potential method for identifying the food sources of arthropods. However, some points must be clarified regarding the applicability of the method, such as the extent of DNA degradation through intestinal digestion, the potential for multiple sources of blood meals and the need for greater knowledge regarding intraspecific variations in mtDNA.

  5. Identification of blood meal sources of Lutzomyia longipalpis using polymerase chain reaction-restriction fragment length polymorphism analysis of the cytochrome B gene

    PubMed Central

    Soares, Vítor Yamashiro Rocha; da Silva, Jailthon Carlos; da Silva, Kleverton Ribeiro; Cruz, Maria do Socorro Pires e; Santos, Marcos Pérsio Dantas; Ribolla, Paulo Eduardo Martins; Alonso, Diego Peres; Coelho, Luiz Felipe Leomil; Costa, Dorcas Lamounier; Costa, Carlos Henrique Nery

    2014-01-01

    An analysis of the dietary content of haematophagous insects can provide important information about the transmission networks of certain zoonoses. The present study evaluated the potential of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the mitochondrial cytochrome B (cytb) gene to differentiate between vertebrate species that were identified as possible sources of sandfly meals. The complete cytb gene sequences of 11 vertebrate species available in the National Center for Biotechnology Information database were digested with Aci I, Alu I, Hae III and Rsa I restriction enzymes in silico using Restriction Mapper software. The cytb gene fragment (358 bp) was amplified from tissue samples of vertebrate species and the dietary contents of sandflies and digested with restriction enzymes. Vertebrate species presented a restriction fragment profile that differed from that of other species, with the exception of Canis familiaris and Cerdocyon thous. The 358 bp fragment was identified in 76 sandflies. Of these, 10 were evaluated using the restriction enzymes and the food sources were predicted for four: Homo sapiens (1), Bos taurus (1) and Equus caballus (2). Thus, the PCR-RFLP technique could be a potential method for identifying the food sources of arthropods. However, some points must be clarified regarding the applicability of the method, such as the extent of DNA degradation through intestinal digestion, the potential for multiple sources of blood meals and the need for greater knowledge regarding intraspecific variations in mtDNA. PMID:24821056

  6. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    SciTech Connect

    Jones, K. L.; Ahn, S.; Allmond, J. M.; Ayres, A.; Bardayan, D. W.; Baugher, T.; Bazin, D.; Berryman, J. S.; Bey, A.; Bingham, C.; Cartegni, L.; Cerizza, G.; Chae, K. Y.; Cizewski, J. A.; Gade, A.; Galindo-Uribarri, A.; Garcia-Ruiz, R. F.; Grzywacz, R.; Howard, M. E.; Kozub, R. L.; Liang, J. F.; Manning, B.; Matoš, M.; McDaniel, S.; Miller, D.; Nesaraja, C. D.; O'Malley, P. D.; Padgett, S.; Padilla-Rodal, E.; Pain, S. D.; Pittman, S. T.; Radford, D. C.; Ratkiewicz, A.; Schmitt, K. T.; Shore, A.; Smith, M. S.; Stracener, D. W.; Stroberg, S. R.; Tostevin, J.; Varner, R. L.; Weisshaar, D.; Wimmer, K.; Winkler, R.

    2015-01-01

    Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z = 50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, N = 82, and neutron-deficient, N = 50, regions. Here, we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in Sn-131 from across the N = 82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient Sn-106,108Sn. In conclusion, In both cases, measurements of γ rays in coincidence with charged particles proved to be invaluable.

  7. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    DOE PAGES

    Jones, K. L.; Ahn, S.; Allmond, J. M.; ...

    2015-01-01

    Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z = 50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, Nmore » = 82, and neutron-deficient, N = 50, regions. Here, we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in Sn-131 from across the N = 82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient Sn-106,108Sn. In conclusion, In both cases, measurements of γ rays in coincidence with charged particles proved to be invaluable.« less

  8. Experimental studies of N/Z equilibration in peripheral collisions using fragment yield ratios

    SciTech Connect

    Keksis, A. L.; May, L. W.; Kohley, Z.; Soisson, S. N.; Stein, B. C.; Wuenschel, S.; Yennello, S. J.; Souliotis, G. A.; Veselsky, M.; Galanopoulos, S.; Shetty, D. V.; Tripathi, R.; Li, B. A.

    2010-05-15

    Peripheral collisions of {sup 40}Ca and {sup 48}Ca projectiles at 32 MeV/nucleon on {sup 112}Sn and {sup 124}Sn targets were studied in this work. The fragments of the projectile-like source (quasiprojectile) were collected with a charged-particle multidetector array. The average value of the neutron-to-proton ratio N/Z of the quasiprojectiles formed in the reactions was determined with two approaches. The first is a direct reconstruction approach using isotopically resolved fragments and is hindered by undetected neutrons leading to lower N/Z values. The second approach, based on the assumption of early fragment formation, employs yield ratios of fragment isobars and is not hindered by undetected neutrons. Using this approach, the amount of N/Z mixing that occurred in the quasiprojectiles (compared to a fully N/Z equilibrated system) was found to be approximately 53%. The experimental results were compared with model calculations. First, the phenomenological DIT (deep inelastic transfer) model was used, followed by the statistical multifragmentation model (SMM). The results of these calculations are in close agreement with the data and indicate that the mean number of undetected neutrons increases with the N/Z of the composite system, accounting for the difference observed between the two approaches of quasiprojectile N/Z determination. Second, the microscopic transport model IBUU (isospin-dependent Boltzmann-Uehling-Uhlenbeck) was employed, providing preliminary results in reasonable agreement with the data. The determination of the degree of N/Z equilibration employing the present fragment yield ratio approach may provide a valuable probe to study the isospin part of the nuclear equation of state in conjunction with detailed microscopic models of the collisions in the Fermi energy regime.

  9. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for rapid diagnosis of neonatal sepsis

    PubMed Central

    Rohit, Anusha; Maiti, Biswajit; Shenoy, Shalini; Karunasagar, Indrani

    2016-01-01

    Background & objectives: The difficulties in diagnosis of neonatal sepsis are due to varied clinical presentation, low sensitivity of blood culture which is considered the gold standard and empirical antibiotic usage affecting the outcome of results. Though polymerase chain reaction (PCR) based detection of bacterial 16S rRNA gene has been reported earlier, this does not provide identification of the causative agent. In this study, we used restriction fragment length polymorphism (RFLP) of amplified 16S rRNA gene to identify the organisms involved in neonatal sepsis and compared the findings with blood culture. Methods: Blood samples from 97 neonates were evaluated for diagnosis of neonatal sepsis using BacT/Alert (automated blood culture) and PCR-RFLP. Results: Bacterial DNA was detected by 16S rRNA gene PCR in 55 cases, while BacT/Alert culture was positive in 34 cases. Staphylococcus aureus was the most common organism detected with both methods. Klebsiella spp. was isolated from four samples by culture but was detected by PCR-RFLP in five cases while Acinetobacter spp. was isolated from one case but detected in eight cases by PCR-RFLP. The sensitivity of PCR was found to be 82.3 per cent with a negative predictive value of 85.7 per cent. Eighty of the 97 neonates had prior exposure to antibiotics. Interpretation & conclusions: The results of our study demonstrate that PCR-RFLP having a rapid turnaround time may be useful for the early diagnosis of culture negative neonatal sepsis. PMID:26997017

  10. Popping Balloons: A Case Study of Dynamical Fragmentation

    NASA Astrophysics Data System (ADS)

    Moulinet, Sébastien; Adda-Bedia, Mokhtar

    2015-10-01

    Understanding the physics of fragmentation is important in a wide range of industrial and geophysical applications. Fragmentation processes involve large strain rates and short time scales that take place during crack nucleation and propagation. Using rubber membranes, we develop an experimental analysis that enables us to track the fragmentation process in situ in both time and space. We find that bursting a highly stretched membrane yields a treelike fragmentation network that originates at a single seed crack, followed by successive crack tip-splitting events. We show that a dynamic instability drives this branching mechanism. Fragmentation occurs when the crack tip speed attains a critical velocity for which tip splitting becomes the sole available mechanism of releasing the stored elastic energy. Given the general character of the fragmentation processes, this framework should be applicable to other crack networks in brittle materials.

  11. A Planar Rocket Motor Model for Visualization of Violent Reaction Due to Fragment Impact

    DTIC Science & Technology

    1990-05-01

    delayed detonation process ( XDT ) was observed in some tests of this material. Twenty-three frings were conducted. The target configuration for each test...all detonations were classified as XDT reactions. For the test with the 2.0-inch air gap (Figure 18), detonation occurred less than 30 microseconds (one...gap (Test 22) resulted in an XDT reaction. Detonation occurred immediately after the debris bubble impacted the second propellant layer. This result

  12. Studies of Fission Fragment Rocket Engine Propelled Spacecraft

    NASA Technical Reports Server (NTRS)

    Werka, Robert O.; Clark, Rodney; Sheldon, Rob; Percy, Thomas K.

    2014-01-01

    The NASA Office of Chief Technologist has funded from FY11 through FY14 successive studies of the physics, design, and spacecraft integration of a Fission Fragment Rocket Engine (FFRE) that directly converts the momentum of fission fragments continuously into spacecraft momentum at a theoretical specific impulse above one million seconds. While others have promised future propulsion advances if only you have the patience, the FFRE requires no waiting, no advances in physics and no advances in manufacturing processes. Such an engine unequivocally can create a new era of space exploration that can change spacecraft operation. The NIAC (NASA Institute for Advanced Concepts) Program Phase 1 study of FY11 first investigated how the revolutionary FFRE technology could be integrated into an advanced spacecraft. The FFRE combines existent technologies of low density fissioning dust trapped electrostatically and high field strength superconducting magnets for beam management. By organizing the nuclear core material to permit sufficient mean free path for escape of the fission fragments and by collimating the beam, this study showed the FFRE could convert nuclear power to thrust directly and efficiently at a delivered specific impulse of 527,000 seconds. The FY13 study showed that, without increasing the reactor power, adding a neutral gas to the fission fragment beam significantly increased the FFRE thrust through in a manner analogous to a jet engine afterburner. This frictional interaction of gas and beam resulted in an engine that continuously produced 1000 pound force of thrust at a delivered impulse of 32,000 seconds, thereby reducing the currently studied DRM 5 round trip mission to Mars from 3 years to 260 days. By decreasing the gas addition, this same engine can be tailored for much lower thrust at much higher impulse to match missions to more distant destinations. These studies created host spacecraft concepts configured for manned round trip journeys. While the

  13. ANOMALOUS REACTION MEAN FREE PATHS OF NUCLEAR PROJECTILE FRAGMENTS FROM HEAVY ION COLLISIONS AT 2 AGeV

    SciTech Connect

    Friedlander, E.M.; Gimpel, R.W.; Heckman, H.H.; Karant, Y.J.; Judek, B.; Ganssauge, E.

    1982-08-01

    We present in detail the description and the analysis of two independent experiments using Bevalac beams of {sup 16}O and {sup 56}Fe. From their results it is concluded that the reaction mean free paths of relativistic projectile fragments, 3 {<=} Z {<=} 26, are shorter for a few centimeters after emission than at large distances where they are compatible with values predicted from experiments on beam nuclei. The probability that this effect is due to a statistical fluctuation is <10{sup -3}. The effect is enhanced in later generations of fragments, the correlation between successive generations suggesting a kind of "memory" for the anomaly. Various systematic and spurious effects as well as conventional explanations are discussed mainly on the basis of direct experimental observations internal to our data, and found not to explain our results. The data can be interpreted by the relatively rare occurrence of anomalous fragments that interact with an unexpectedly large cross section. The statistical methods used in the analysis of the observations are fully described.

  14. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Y.T.

    1987-03-01

    Purpose of this research project is two-fold: (1) to elucidate detailed dynamics of simple elementary reactions which are theoretically important and to unravel the mechanism of complex chemical reactions or photo chemical processes which play an important role in many macroscopic processes and (2) to determine the energetics of polyatomic free radicals using microscopic experimental methods. Most of the information is derived from measurement of the product fragment translational energy and angular distributions using unique molecular beam apparati designed for these purposes.

  15. Study of Shape Isomeric States in Fission Fragments

    NASA Astrophysics Data System (ADS)

    Pyatkov, Yu. V.; Kamanin, D. V.; Alexandrov, A. A.; Alexandrova, I. A.; Kondtatyev, N. A.; Kuznetsova, , E. A.; Strekalovsky, A. O.; Strekalovsky, O. V.; Zhuchko, V. E.; Mkaza, N.

    2015-06-01

    For the first time the brake-up of the fission fragments crossing metal foil was observed. The effect takes place predominantly in front impacts. To treat the data we suppose the bulk of the fragments from the conventional binary fission to be borne in shape-isomer states which look like di-nuclear systems with magic cores.

  16. Molecular variation analysis of Aspergillus flavus using polymerase chain reaction-restriction fragment length polymorphism of the internal transcribed spacer rDNA region

    PubMed Central

    Zarrin, Majid; Erfaninejad, Maryam

    2016-01-01

    Aspergillus flavus is the second most common disease-causing species of Aspergillus in humans. The fungus is frequently associated with life-threatening infections in immunocompromised hosts. The primary aim of the present study was to analyze the genetic variability among different isolates of A. flavus using polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP). A total of 62 A. flavus isolates were tested in the study. Molecular variability was searched for by analysis of the PCR amplification of the internal transcribed spacer (ITS) regions of ribosomal DNA using restriction enzymes. PCR using primers for ITS1 and ITS4 resulted in a product of ~600 bp. Amplicons were subjected to digestion with restriction endonucleases EcoRI, HaeIII and TaqI. Digestion of the PCR products using these restriction enzymes produced different patterns of fragments among the isolates, with different sizes and numbers of fragments, revealing genetic variability. In conclusion, ITS-RFLP is a useful molecular tool in screening for nucleotide polymorphisms among A. flavus isolates. PMID:27588085

  17. A Semi-Classical Model to Study Nuclear Fragmentation

    NASA Astrophysics Data System (ADS)

    Navarro, Martha; Chernomoretz, Ariel; Dorso, Claudio; Lopez, Jorge

    1999-10-01

    A semi-classical model based on the use of molecular dynamics has been developed for the study of heavy-ion reactions at intermediate energies. The model reproduces nucleon-nucleon cross sections through the use of a two-body potential. The study covers several characteristics of heavy-ion collisions, such as formation of necks, and formation of intermediate residue. Preliminary results on the use of the model to study the caloric curve of nuclear matter and the temperature evolution of the system are also discussed.

  18. Role of angular momentum in the production of complex fragments in fusion and quasifission reactions

    SciTech Connect

    Kalandarov, Sh. A.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.

    2011-05-15

    The influence of angular momentum on the competition between complete fusion followed by the decay of compound nucleus and quasifission channels is treated within the dinuclear system model. The charge distributions of the products in the reactions {sup 28}Si+{sup 96}Zr, {sup 4}He+{sup 130}Te, and {sup 40}Ca+{sup 82}Kr are predicted at bombarding energies above the Coulomb barrier. The results of calculations for the reactions {sup 93}Nb+{sup 9}Be,{sup 12}C,{sup 27}Al; {sup 84}Kr+{sup 27}Al; {sup 86}Kr+{sup 63}Cu; {sup 139}La+{sup 12}C,{sup 27}Al; and {sup 45}Sc+{sup 65}Cu are compared with the available experimental data.

  19. Experimental Study of Serpentinization Reactions

    NASA Technical Reports Server (NTRS)

    Cohen, B. A.; Brearley, A. J.; Ganguly, J.; Liermann, H.-P.; Keil, K.

    2004-01-01

    Current carbonaceous chondrite parent-body thermal models [1-3] produce scenarios that are inconsistent with constraints on aqueous alteration conditions based on meteorite mineralogical evidence, such as phase stability relationships within the meteorite matrix minerals [4] and isotope equilibration arguments [5, 6]. This discrepancy arises principally because of the thermal runaway effect produced by silicate hydration reactions (here loosely called serpentinization, as the principal products are serpentine minerals), which are so exothermic as to produce more than enough heat to melt more ice and provide a self-sustaining chain reaction. One possible way to dissipate the heat of reaction is to use a very small parent body [e.g., 2] or possibly a rubble pile model. Another possibility is to release this heat more slowly, which depends on the alteration reaction path and kinetics.

  20. New Approach for Studying Slow Fragmentation Kinetics in FT-ICR: Surface-Induced Dissociation Combined with Resonant Ejection

    SciTech Connect

    Laskin, Julia; Futrell, Jean H.

    2015-02-01

    We introduce a new approach for studying the kinetics of large ion fragmentation in the gas phase by coupling surface-induced dissociation (SID) in a Fourier transform ion cyclotron resonance mass spectrometer with resonant ejection of selected fragment ions using a relatively short (5 ms) ejection pulse. The approach is demonstrated for singly protonated angiotensin III ions excited by collisions with a self-assembled monolayer of alkylthiol on gold (HSAM). The overall decomposition rate and rate constants of individual reaction channels are controlled by varying the kinetic energy of the precursor ion in a range of 65–95 eV. The kinetics of peptide fragmentation are probed by varying the delay time between resonant ejection and fragment ion detection at a constant total reaction time. RRKM modeling indicates that the shape of the kinetics plots is strongly affected by the shape and position of the energy deposition function (EDF) describing the internal energy distribution of the ion following ion-surface collision. Modeling of the kinetics data provides detailed information on the shape of the EDF and energy and entropy effects of individual reaction channels.

  1. Hydride transfer reactions via ion-neutral complex: fragmentation of protonated N-benzylpiperidines and protonated N-benzylpiperazines in mass spectrometry.

    PubMed

    Chai, Yunfeng; Jiang, Kezhi; Pan, Yuanjiang

    2010-05-01

    An ion-neutral complex (INC)-mediated hydride transfer reaction was observed in the fragmentation of protonated N-benzylpiperidines and protonated N-benzylpiperazines in electrospray ionization mass spectrometry. Upon protonation at the nitrogen atom, these compounds initially dissociated to an INC consisting of [RC(6)H(4)CH(2)](+) (R = substituent) and piperidine or piperazine. Although this INC was unstable, it did exist and was supported by both experiments and density functional theory (DFT) calculations. In the subsequent fragmentation, hydride transfer from the neutral partner to the cation species competed with the direct separation. The distribution of the two corresponding product ions was found to depend on the stabilization energy of this INC, and it was also approved by the study of substituent effects. For monosubstituted N-benzylpiperidines, strong electron-donating substituents favored the formation of [RC(6)H(4)CH(2)](+), whereas strong electron-withdrawing substituents favored the competing hydride transfer reaction leading to a loss of toluene. The logarithmic values of the abundance ratios of the two ions were well correlated with the nature of the substituents, or rather, the stabilization energy of this INC.

  2. Detection and differentiation of filarial parasites by universal primers and polymerase chain reaction-restriction fragment length polymorphism analysis.

    PubMed

    Nuchprayoon, Surang; Junpee, Alisa; Poovorawan, Yong; Scott, Alan L

    2005-11-01

    Filarial nematode parasites are a serious cause of morbidity in humans and animals. Identification of filarial infection using traditional morphologic criteria can be difficult and lead to misdiagnosis. We report on a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)-based method to detect and differentiate a broad range of filarial species in a single PCR. The first internal transcribed spacer 1 (ITS1) along with the flanking 18S and 5.8S ribosomal DNA (rDNA) were isolated and cloned from Wuchereria bancrofti, Brugia malayi, and Brugia pahangi. Sequence analysis identified conserved sites in the 18S and 5.8S rDNA sequence that could be used as universal priming sites to generate ITS1-distinctive PCR products that were useful for distinguishing filariae at the genus level. The addition of a digestion of the ITS1 PCR product with the restriction endonuclease Ase I generated a fragment profile that allowed differentiation down to the species level for W. bancrofti, B. malayi, B. pahangi, Dirofilaria immitis, and D. repens. The PCR-RFLP of ITS1 rDNA will be useful in diagnosing and differentiating filarial parasites in human, animal reservoir hosts, and mosquito vectors in disease-endemic areas.

  3. Mass and charge distributions in iron-induced reactions and excitation energy division between the fragments of the 672-MeV 56Fe + 165Ho reaction

    SciTech Connect

    Madani, Houria

    1993-01-01

    The projectile-like and target-like fragments produced by the 12-MeV/nucleon 56Fe + 165Ho reaction were detected in coincidence. The measured parameters were the mass, charge, kinetic energy scattering angle of the projectile-like fragments, and the scattering angle of the target-like fragments. The mass and charge distributions of the projectile-like fragments were generated as a function of energy loss, and characterized by their centroids, variances, and correlation coefficients. The neutron drift of the measured projectile-like products is mostly due to evaporative processes, while the charge drift is a result of a net transfer of protons from the projectile-like fragment to the target-like fragment. The result is a weak drift of the system towards mass asymmetry. The predictions of two nucleon exchange models are compared to the experimental results of the 672-MeV 56Fe + 165Ho reaction and other Fe-induced reactions. The fairly good agreement between the experimental and theoretical variances verifies the prevalence of a nucleon exchange mechanism in these reactions. The information from the coincidence measurement and two-body kinematics are used to reconstruct the pre-evaporation masses of the projectile-like and target-like fragments of the reaction. Statistical evaporation calculations are used to translate these masses into excitation energies of the primary fragments. The ratio of excitation energy stored in the projectile-Mm fragment decreases with increasing energy loss, in qualitative agreement with previous measurements; however, higher ratios are observed for the 672-MeV 56Fe on 165Ho system.

  4. Mass and charge distributions in iron-induced reactions and excitation energy division between the fragments of the 672-MeV [sup 56]Fe + [sup 165]Ho reaction

    SciTech Connect

    Madani, H.

    1993-01-01

    The projectile-like and target-like fragments produced by the 12-MeV/nucleon [sup 56]Fe + [sup 165]Ho reaction were detected in coincidence. The measured parameters were the mass, charge, kinetic energy scattering angle of the projectile-like fragments, and the scattering angle of the target-like fragments. The mass and charge distributions of the projectile-like fragments were generated as a function of energy loss, and characterized by their centroids, variances, and correlation coefficients. The neutron drift of the measured projectile-like products is mostly due to evaporative processes, while the charge drift is a result of a net transfer of protons from the projectile-like fragment to the target-like fragment. The result is a weak drift of the system towards mass asymmetry. The predictions of two nucleon exchange models are compared to the experimental results of the 672-MeV [sup 56]Fe + [sup 165]Ho reaction and other Fe-induced reactions. The fairly good agreement between the experimental and theoretical variances verifies the prevalence of a nucleon exchange mechanism in these reactions. The information from the coincidence measurement and two-body kinematics are used to reconstruct the pre-evaporation masses of the projectile-like and target-like fragments of the reaction. Statistical evaporation calculations are used to translate these masses into excitation energies of the primary fragments. The ratio of excitation energy stored in the projectile-Mm fragment decreases with increasing energy loss, in qualitative agreement with previous measurements; however, higher ratios are observed for the 672-MeV [sup 56]Fe on [sup 165]Ho system.

  5. Spectroscopic investigation of the reaction mechanism of CopB-B, the catalytic fragment from an archaeal thermophilic ATP-driven heavy metal transporter.

    PubMed

    Völlmecke, Christian; Kötting, Carsten; Gerwert, Klaus; Lübben, Mathias

    2009-11-01

    The mechanism of ATP hydrolysis of a shortened variant of the heavy metal-translocating P-type ATPase CopB of Sulfolobus solfataricus was studied. The catalytic fragment, named CopB-B, comprises the nucleotide binding and phosphorylation domains. We demonstrated stoichiometric high-affinity binding of one nucleotide to the protein (K(diss) 1-20 microm). Mg is not necessary for nucleotide association but is essential for the phosphatase activity. Binding and hydrolysis of ATP released photolytically from the caged precursor nitrophenylethyl-ATP was measured at 30 degrees C by infrared spectroscopy, demonstrating that phosphate groups are not involved in nucleotide binding. The hydrolytic kinetics was biphasic, and provides evidence for at least one reaction intermediate. Modelling of the forward reaction gave rise to three kinetic states connected by two intrinsic rate constants. The lower kinetic constant (k(1) = 4.7 x 10(-3) s(-1) at 30 degrees C) represents the first and rate-limiting reaction, probably reflecting the transition between the open and closed conformations of the domain pair. The subsequent step has a faster rate (k(2) = 17 x 10(-3) s(-1) at 30 degrees C), leading to product formation. Although the latter appears to be a single step, it probably comprises several reactions with presently unresolved intermediates. Based on these data, we suggest a model of the hydrolytic mechanism.

  6. Personality dependent effects of the ACTH 4--10 fragment on test performances and on concomitant autonomic reactions.

    PubMed

    Breier, C; Kain, H; Konzett, H

    1979-11-01

    The effect of the ACTH-fragment 4--10 (30 mg SC) on a mental performance test and on some concomitant cardiovascular changes was investigated in comparison with a placebo in a double blind cross-over study. The subjects were either mainly extraverted or mainly introverted according to Eysenck's 'Maudsley Personality Inventory'. Under the influence of the heptapeptide extraverted subjects achieved a higher total score in the mental task performance with a smaller increase of forearm blood flow and of heart rate than under the influence of the placebo. In contrast, under the influence of the placebo introverted subjects achieved a higher total score in the mental task performance with a smaller increase of forearm blood flow and of heart rate than under the influence of the ACTH-fragment. Personality, therefore, determines to some degree how this centrally acting heptapeptide influences efficiency in the mental task performance and the concomitant cardiovascular changes.

  7. Kinetic studies of elementary chemical reactions

    SciTech Connect

    Durant, J.L. Jr.

    1993-12-01

    This program concerning kinetic studies of elementary chemical reactions is presently focussed on understanding reactions of NH{sub x} species. To reach this goal, the author is pursuing experimental studies of reaction rate coefficients and product branching fractions as well as using electronic structure calculations to calculate transition state properties and reaction rate calculations to relate these properties to predicted kinetic behavior. The synergy existing between the experimental and theoretical studies allow one to gain a deeper insight into more complex elementary reactions.

  8. Effects of forest fragmentation on nocturnal Asian birds: A case study from Xishuangbanna, China

    PubMed Central

    DAYANANDA, Salindra K.; GOODALE, Eben; LEE, Myung-bok; LIU, Jia-Jia; MAMMIDES, Christos; PASION, Bonifacio O.; QUAN, Rui-Chang; SLIK, J. W. Ferry; SREEKAR, Rachakonda; TOMLINSON, Kyle W.; YASUDA, Mika

    2016-01-01

    Owls have the potential to be keystone species for conservation in fragmented landscapes, as the absence of these predators could profoundly change community structure. Yet few studies have examined how whole communities of owls respond to fragmentation, especially in the tropics. When evaluating the effect of factors related to fragmentation, such as fragment area and distance to the edge, on these birds, it is also important in heterogeneous landscapes to ask how ‘location factors’ such as the topography, vegetation and soil of the fragment predict their persistence. In Xishuangbanna, southwest China, we established 43 transects (200 m×60 m) within 20 forest fragments to sample nocturnal birds, both visually and aurally. We used a multimodel inference approach to identify the factors that influence owl species richness, and generalized linear mixed models to predict the occurrence probabilities of each species. We found that fragmentation factors dominated location factors, with larger fragments having more species, and four of eight species were significantly more likely to occur in large fragments. Given the potential importance of these birds on regulating small mammal and other animal populations, and thus indirectly affecting seed dispersal, we suggest further protection of large fragments and programs to increase their connectivity to the remaining smaller fragments. PMID:27265653

  9. Rational Design of High-Number dsDNA Fragments Based on Thermodynamics for the Construction of Full-Length Genes in a Single Reaction.

    PubMed

    Birla, Bhagyashree S; Chou, Hui-Hsien

    2015-01-01

    Gene synthesis is frequently used in modern molecular biology research either to create novel genes or to obtain natural genes when the synthesis approach is more flexible and reliable than cloning. DNA chemical synthesis has limits on both its length and yield, thus full-length genes have to be hierarchically constructed from synthesized DNA fragments. Gibson Assembly and its derivatives are the simplest methods to assemble multiple double-stranded DNA fragments. Currently, up to 12 dsDNA fragments can be assembled at once with Gibson Assembly according to its vendor. In practice, the number of dsDNA fragments that can be assembled in a single reaction are much lower. We have developed a rational design method for gene construction that allows high-number dsDNA fragments to be assembled into full-length genes in a single reaction. Using this new design method and a modified version of the Gibson Assembly protocol, we have assembled 3 different genes from up to 45 dsDNA fragments at once. Our design method uses the thermodynamic analysis software Picky that identifies all unique junctions in a gene where consecutive DNA fragments are specifically made to connect to each other. Our novel method is generally applicable to most gene sequences, and can improve both the efficiency and cost of gene assembly.

  10. Iron meteorite fragment studied by atomic and nuclear analytical methods

    NASA Astrophysics Data System (ADS)

    Cesnek, Martin; Štefánik, Milan; Kmječ, Tomáš; Miglierini, Marcel

    2016-10-01

    Chemical and structural compositions of a fragment of Sikhote-Alin iron meteorite were investigated by X-ray fluorescence analysis (XRF), neutron activation analysis (NAA) and Mössbauer spectroscopy (MS). XRF and NAA revealed the presence of chemical elements which are characteristic for iron meteorites. XRF also showed a significant amount of Si and Al on the surface of the fragment. MS spectra revealed possible presence of α-Fe(Ni, Co) phase with different local Ni concentration. Furthermore, paramagnetic singlet was detected in Mössbauer spectra recorded at room temperature and at 4.2 K.

  11. Improved Polymerase Chain Reaction-restriction Fragment Length Polymorphism Genotyping of Toxic Pufferfish by Liquid Chromatography/Mass Spectrometry

    PubMed Central

    Miyaguchi, Hajime

    2016-01-01

    An improved version of a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method for genotyping toxic pufferfish species by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) is described. DNA extraction is carried out using a silica membrane-based DNA extraction kit. After the PCR amplification using a detergent-free PCR buffer, restriction enzymes are added to the solution without purifying the reaction solution. A reverse-phase silica monolith column and a Fourier transform high resolution mass spectrometer having a modified Kingdon trap analyzer are employed for separation and detection, respectively. The mobile phase, consisting of 400 mM 1,1,1,3,3,3-hexafluoro-2-propanol, 15 mM triethylamine (pH 7.9) and methanol, is delivered at a flow rate of 0.4 ml/min. The cycle time for LC/ESI-MS analysis is 8 min including equilibration of the column. Deconvolution software having an isotope distribution model of the oligonucleotide is used to calculate the corresponding monoisotopic mass from the mass spectrum. For analysis of oligonucleotides (range 26-79 nucleotides), mass accuracy was 0.62 ± 0.74 ppm (n = 280) and excellent accuracy and precision were sustained for 180 hr without use of a lock mass standard. PMID:27684516

  12. Study of Analytic Statistical Model for Decay of Light and Medium Mass Nuclei in Nuclear Fragmentation

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Wilson, John W.

    1996-01-01

    The angular momentum independent statistical decay model is often applied using a Monte-Carlo simulation to describe the decay of prefragment nuclei in heavy ion reactions. This paper presents an analytical approach to the decay problem of nuclei with mass number less than 60, which is important for galactic cosmic ray (GCR) studies. This decay problem of nuclei with mass number less than 60 incorporates well-known levels of the lightest nuclei (A less than 11) to improve convergence and accuracy. A sensitivity study of the model level density function is used to determine the impact on mass and charge distributions in nuclear fragmentation. This angular momentum independent statistical decay model also describes the momentum and energy distribution of emitted particles (n, p, d, t, h, and a) from a prefragment nucleus.

  13. Soft-x-ray fragmentation studies of molecular ions

    NASA Astrophysics Data System (ADS)

    Wolf, Andreas; Pedersen, Henrik B.; Lammich, Lutz; Jordon-Thaden, Brandon; Altevogt, Simon; Domesle, Christian; Hergenhahn, Uwe; Förstel, Marko; Heber, Oded

    2010-10-01

    Imaging of photofragments from molecular ions after irradiation by soft x-ray photons has been realized at the ion beam infrastructure TIFF set up at the FLASH facility. Photodissociation of the two-electron system HeH+ at 38.7 eV revealed the electronic excitations and the charge-state ratios for the products of this process, reflecting the non-adiabatic dissociation dynamics through multiple avoided crossings among the HeH+ Rydberg potential curves. Dissociative ionization of the protonated water molecules H3O+ and H5O+2 at 90 eV revealed the main fragmentation pathways after the production of valence vacancies in these ionic species, which include a strong three-body channel with a neutral fragment (OH + H+ + H+) in H3O+ photolysis and a significant two-body fragmentation channel (H3O++ H2O+) in H5O+2 photolysis. The measurements yield absolute cross sections and fragment angular distributions. Increased precision and sensitivity of the technique were realized in recent developments, creating a tool for exploring x-ray excited molecular states under highly controlled target conditions challenging detailed theoretical understanding.

  14. High-resolution (e, 2e + ion) study of electron-impact ionization and fragmentation of methane

    SciTech Connect

    Ren, Xueguang Pflüger, Thomas; Weyland, Marvin; Baek, Woon Yong; Rabus, Hans; Ullrich, Joachim; Dorn, Alexander

    2015-05-07

    The ionization and fragmentation of methane induced by low-energy (E{sub 0} = 66 eV) electron-impact is investigated using a reaction microscope. The momentum vectors of all three charged final state particles, two outgoing electrons, and one fragment ion, are detected in coincidence. Compared to the earlier study [Xu et al., J. Chem. Phys. 138, 134307 (2013)], considerable improvements to the instrumental mass and energy resolutions have been achieved. The fragment products CH{sub 4}{sup +}, CH{sub 3}{sup +}, CH{sub 2}{sup +}, CH{sup +}, and C{sup +} are clearly resolved. The binding energy resolution of ΔE = 2.0 eV is a factor of three better than in the earlier measurements. The fragmentation channels are investigated by measuring the ion kinetic energy distributions and the binding energy spectra. While being mostly in consistence with existing photoionization studies the results show differences including missing fragmentation channels and previously unseen channels.

  15. Fragmentation of displacement cascades into subcascades: A molecular dynamics study

    SciTech Connect

    Antoshchenkova, E.; Luneville, L.; Simeone, D.; Stoller, R. E.; Hayoun, M.

    2015-01-01

    The fragmentation of displacement cascades into subcascades in copper and iron has been investigated through the molecular dynamics technique. A two-point density correlation function has been used to analyze the cascades as a function of the primary knock-on (PKA) energy. This approach is used as a tool for detecting subcascade formation. The fragmentation can already be identified at the end of the ballistic phase. Its resulting evolution in the peak damage state discriminates between unconnected and connected subcascades. The damage zone at the end of the ballistic phase is the precursor of the extended regions that contain the surviving defects. A fractal analysis of the cascade exhibits a dependence on both the stage of the cascade development and the PKA energy. This type of analysis enables the minimum and maximum displacement spike energies together with the subcascade formation threshold energy to be determined. (C) 2014 Elsevier B.V. All rights reserved.

  16. Single Molecule Study on Incorporation Efficiency of DPO4 and Klenow Fragment to BPDE Adduct

    NASA Astrophysics Data System (ADS)

    Song, Lu; Yeh, Yin; Balhorn, Rod; Cosman, Monique

    2009-03-01

    DNA synthesis involving high fidelity A-family polymerases such as Klenow fragment is blocked by DNA adducts, while Y-family DNA polymerases such as Dpo4 can bypass the DNA adducts to resume DNA synthesis. So understanding the functional relationship between A-family and Y-family DNA polymerases in DNA replication and the mechanism of bypassing DNA adducts is of great help to explain the cause of mutagenesis. We introduce a flow cell on modified surface to study the incorporation efficiency of Dpo4 and Klenow fragments to benzo[a]pyrene-diol-epoxide (BPDE) adduct at single molecule level. Specifically, we anchor the labeled DNA onto the modified surface with adduct site open for nucleotide incorporation and flow the polymerases and labeled nucleotides into flow cell. With Total Internal Reflection Fluorescence Microscopy (TIRFM) we identify the incorporation of the nucleotides onto the anchored DNA template by identifying the co-localization of the template position and that of the labeled nucleotide. We further quantify the signal densities of the images obtained from the two different polymerases, thus examining whether incorporation reactions have been executed and quantifying the incorporation efficiency of the polymerases. We can also identify, on the specific adduct site, which nucleotide, if any, is incorporated by each of the two polymerases.

  17. Kinetics of the competitive reactions of isomerization and peptide bond cleavage at l-α- and d-β-aspartyl residues in an αA-crystallin fragment.

    PubMed

    Aki, Kenzo; Okamura, Emiko

    2017-01-01

    d-β-aspartyl (Asp) residue has been found in a living body such as aged lens crystallin, although l-α-amino acids are constituents in natural proteins. Isomerization from l-α- to d-β-Asp probably modulates structures to affect biochemical reactions. At Asp residue, isomerization and peptide bond cleavage compete with each other. To gain insight into how fast each reaction proceeds, the analysis requires the consideration of both pathways simultaneously and independently. No information has been provided, however, about these competitive processes because each reaction has been studied separately. The contribution of Asp isomers to the respective pathways has still been veiled. In this work, the two competitive reactions, isomerization and spontaneous peptide bond cleavage at Asp residue, were simultaneously observed and compared in an αA-crystallin fragment, S(51) LFRTVLD(58) SG(60) containing l-α- and d-β-Asp58 isomers. The kinetics showed that the formation of l- and d-succinimide (Suc) intermediate, as a first step of isomerization, was comparable at l-α- and d-β-Asp. Although l-Suc was converted to l-β-Asp, d-Suc was liable to return to the original d-β-Asp, the reverse reaction marked enough to consider d-β-Asp as apparently stable. d-β-Asp was also resistant to the peptide bond cleavage. Such apparent less reactivity is probably the reason for gradual and abnormal accumulation of d-β-Asp in a living body under physiological conditions. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

  18. Molecular authentication of 21 Korean artemisia species (Compositae) by polymerase chain reaction-restriction fragment length polymorphism based on trnL-F region of chloroplast DNA.

    PubMed

    Lee, Jeong Hoon; Lee, Jei Wan; Sung, Jung Sook; Bang, Kyong Hwan; Moon, Sung Gi

    2009-11-01

    The present study describes the molecular authentication of 21 Korean Artemisia species using PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) technique based on the trnL-F sequences in chloroplast DNA. Five different banding patterns were generated from 21 Artemisia species using HinfI restriction enzyme. A. apiacea, A. keiskeana and A. sieversiana have specific banding patterns. The remaining 18 species had shared two banding patterns. Phylogenetic analysis based on trnL-F sequence variations showed results similar to PCR-RFLP banding patterns. It suggested that the trnL-F region does not have sufficient variations to identify the 21 Artemisia species. However, the specific banding patterns for A. apiacea, A. keiskeana and A. sieversiana can be utilized as a DNA marker for discriminating them from other Artemisia species. These markers will be also useful for developing A. apiacea, A. keiskeana and A. sieversiana into new medicine and food based on their efficacy.

  19. Polymerase chain reaction-restriction fragment length polymorphism method to distinguish three mealybug groups within the Planococcus citri-P. minor species complex (Hemiptera: Coccoidea: Pseudococcidae).

    PubMed

    Rung, A; Miller, D R; Scheffer, S J

    2009-02-01

    The mealybug species Planococcus citri (Risso) and Planococcus minor (Maskell) (Hemiptera: Coccoidea: Pseudococcidae) have special significance to U.S. quarantine and U.S. agriculture. Commonly intercepted at U.S. ports-of-entry, they are difficult to identify based on morphological characters. This study presents a molecular method for distinguishing P. citri, P. minor, and a genetically distinct group that is morphologically identical to P. citri, from Hawaii. This method uses polymerase chain reaction (PCR) followed by restriction fragment polymorphism analysis (RFLP) using the restriction enzymes BspH1, BsmH1, and HpH1. The resulting band patterns can be visualized in a 2% agarose gel and are sufficient to differentiate between the three entities mentioned above. PCR-RFLP diagnostics can be used for all life stages and is cheaper and faster than DNA sequencing.

  20. Mycobacterium avium restriction fragment length polymorphism-IS IS1245 and the simple double repetitive element polymerase chain reaction typing method to screen genetic diversity in Brazilian strains.

    PubMed

    Sequeira, Patrícia Carvalho de; Fonseca, Leila de Souza; Silva, Marlei Gomes da; Saad, Maria Helena Féres

    2005-11-01

    Simple double repetitive element polymerase chain reaction (MaDRE-PCR) and Pvu II-IS1245 restriction fragment length polymorphism (RFLP) typing methods were used to type 41 Mycobacterium avium isolates obtained from 14 AIDS inpatients and 10 environment and animals specimens identified among 53 mycobacteria isolated from 237 food, chicken, and pig. All environmental and animals strains showed orphan patterns by both methods. By MaDRE-PCR four patients, with multiple isolates, showed different patterns, suggesting polyclonal infection that was confirmed by RFLP in two of them. This first evaluation of MaDRE-PCR on Brazilian M. avium strains demonstrated that the method seems to be useful as simple and less expensive typing method for screening genetic diversity in M. avium strains on selected epidemiological studies, although with limitation on analysis identical patterns except for one band.

  1. Discrimination of seven Anopheles species from San Pedro de Uraba, Antioquia, Colombia, by polymerase chain reaction-restriction fragment length polymorphism analysis of its sequences.

    PubMed

    Zapata, Mario A; Cienfuegos, Astrid V; Quirós, Oscar I; Quiñones, Martha L; Luckhart, Shirley; Correa, Margarita M

    2007-07-01

    Accurate identification of anopheline species is essential for vector incrimination and implementation of appropriate control strategies. Several anopheline species are considered important malaria vectors in Colombia; however, species determination is complicated by cryptic morphology and intra-individual variation. We describe polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of internal transcribed spacer 2 (ITS2) sequences for differentiation of seven Anopheles species collected in a locality in Antioquia, Colombia, with high levels of malaria transmission. Each of these seven species can be identified by unique AluI PCR-RFLP restriction patterns. Comparisons of morphologic identification with molecular identification of voucher specimens confirmed species designation for 886 wild-caught anophelines. This new method can be used as a diagnostic tool for discrimination of anopheline species of medical importance in this region, some of which have overlapping morphologic characters and for conducting complementary studies where rapid and accurate identification of large numbers of specimens is needed.

  2. Determining fragmentation dynamics through a study of neutron multiplicity at the NSCL

    NASA Astrophysics Data System (ADS)

    Stephenson, Sharon; Christ, Peter; Mazza, Maria; MoNA Collaboration

    2017-01-01

    In nuclear fragmentation reactions the number of neutrons and the excitation energy of the final fragment are related to the excitation energies of prefragments, which are produced in the reaction target but not directly observed. The MoNA Collaboration designed and performed an experiment to measure the number of neutrons in coincidence with charged projectile fragments to determine the excitation mechanisms of specific prefragments. All prior MoNA experimental campaigns concentrated on neutrons emitted from discrete levels in near dripline nuclei and treated any evaporation neutrons as an underlying background. This experiment capitalizes on those evaporation neutrons, focusing on sodium, neon and fluorine reaction products. For the experiment a 32Mg secondary beam with energy 86 MeV/u was incident on a Be reaction target. This target is upstream from the Sweeper, a superconducting dipole steering magnet with a bending angle of 43° and a vertical gap that permits forward-focused neutrons to get to the MoNA, the Modular Neutron Array. The rigidity of the Sweeper was varied during this experiment to increase the detection range. Analysis of the neutron-neutron hit distribution in coincidence with each sodium, neon, or fluorine charged fragment will be presented. This work was supported in part by the National Science Foundation Award 1613429 and the Howard Hughes Medical Institute Award 52007540.

  3. Synthetic Studies toward the C14-C29 Fragment of Mirabalin.

    PubMed

    Cornil, Johan; Echeverria, Pierre-Georges; Reymond, Sébastien; Phansavath, Phannarath; Ratovelomanana-Vidal, Virginie; Guérinot, Amandine; Cossy, Janine

    2016-09-16

    A convergent synthesis of one isomer of the C14-C29 fragment of mirabalin is disclosed. The key steps include a Marshall allenylation, a Mukaiyama aldol reaction and a Crimmins aldolization, which allow the control of 10 out of 25 stereogenic centers present in the molecule.

  4. [Microclimate edge effects of evergreen broad-leaved forest fragments in Jinyun Mountain: a preliminary study].

    PubMed

    Yan, Min; Zhong, Zhangchen; Qiao, Xiuhong

    2006-01-01

    This paper studied the microclimate of continuous and fragmental evergreen broad-leaved forests in Jinyun Mountain by determining the horizontal gradient distribution of microclimate elements near forest edges. The results showed that there existed clear edge effects of microclimate in every edge of fragmental forests. The distinctions of maximum and minimum air temperature, photosynthetic active radiation, and minimum relative humidity between edge forest and interior forest were higher or greater, while that of maximum ground surface temperature was lower or smaller in dry season than in rain season. The edge effect was the smallest in the biggest fragmental patch, but the greatest in the smallest fragmental patch in interior forest.

  5. Neutron production in coincidence with fragments from the 4Ca+H reactions at Elab=357 and 565 A MeV

    NASA Astrophysics Data System (ADS)

    Tuvà, C.; Albergo, S.; Boemi, D.; Caccia, Z.; Chen, C.-X.; Costa, S.; Crawford, H. J.; Cronqvist, M.; Engelage, J.; Greiner, L.; Guzik, T. G.; Insolia, A.; Knott, C. N.; Lindstrom, P. J.; Mitchell, J. W.; Potenza, R.; Russo, G. V.; Soutoul, A.; Testard, O.; Tricomi, A.; Tull, C. E.; Waddington, C. J.; Webber, W. R.; Wefel, J. P.

    2000-04-01

    In the frame of the Transport Collaboration neutrons in coincidence with charged fragments produced in the 40Ca+H reaction at Elab=357 and 565 A MeV have been measured at the Heavy Ion Spectrometer System (HISS) facility of the Lawrence Berkeley National Laboratory, using the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range about the beam in the forward direction (0°-3.2°). In this contribution we report absolute neutron production cross sections in coincidence with charged fragments (10⩽Z⩽20). The neutron multiplicities have been estimated from the comparison between the neutron cross sections, in coincidence with the fragments, and the elemental cross sections. We have found evidence for a pre-equilibrium emission of prompt neutrons in superposition to a `slower' deexcitation of the equilibrated remnant by emission of nucleons and fragments, as already seen in the inclusive rapidity distributions.

  6. Neutron Production in Coincidence with Fragments from the {sup 40}Ca + H Reactions at E{sub lab} = 357 and 565 A MeV

    SciTech Connect

    Tuve, C.; Albergo, S.; Boemi, D.; Caccia, Z.; Chen, C.-X.; Costa, S.; Crawford, H.J.; Cronqvist, M.; Engelage, J.; Greiner, L.; Guzik, T.G.; Insolia, A.; Knott, C.N.; Lindstrom, P.J.; Mitchell, J.W.; Potenza, R.; Russo, G.V.; Soutoul, A.; Testard, O.; Tricomi, A.; Tull, C.E.; Waddington, C.J.; Webber, W.R.; Wefel, J.P.

    2000-12-31

    In the frame of the Transport Collaboration neutrons in coincidence with charged fragments produced in the {sup 40}Ca + H reaction at E{sub lab} = 357 and 565 AMeV have been measured at the Heavy Ion Spectrometer System (HISS) facility of the Lawrence Berkeley National Laboratory, using the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range about the beam in the forward direction (0? - 3.2?). In this contribution we report absolute neutron production cross sections in coincidence with charged fragments (10 {<=} Z {<=} 20). The neutron multiplicities have been estimated from the comparison between the neutron cross sections, in coincidence with the fragments, and the elemental cross sections. We have found evidence for a pre-equilibrium emission of prompt neutrons in superposition to a 'slower' deexcitation of the equilibrated remnant by emission of nucleons and fragments, as already seen in the inclusive rapidity distributions.

  7. Polymerase chain reaction-restriction fragment length polymorphism assays to distinguish Liriomyza huidobrensis (Diptera: Agromyzidae) from associated species on lettuce cropping systems in Italy.

    PubMed

    Masetti, Antonio; Luchetti, Andrea; Mantovani, Barbara; Burgio, Giovanni

    2006-08-01

    The pea leafminer, Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae), is a serious insect pest infesting open field lettuce plantings in northern Italy. In these cropping systems, it coexists with several other agromyzid species that have negligible economic importance on open field vegetables. The rapid detection of L. huidobrensis is crucial for effective management strategies, but the identification of agromyzids to species can be very difficult at adult as well at immature stages. In this study, a polymerase chain reaction (PCR)-restriction fragment length polymorphism assay is proposed to separate L. huidobrensis from Liriomyza bryoniae (Kaltenbach), Liriomyza trifolii (Burgess), and Chromatomyia horticola (Goureau), which usually occur in the same lettuce plantings. An approximately 1,031-bp region of the mitochondrial genome encompassing the 3' region of cytochrome oxidase I, the whole leucine tRNA, and all of the cytochrome oxidase II was amplified by PCR and digested using the enzymes PvuII and SnaBI separately. Both endonucleases cut the amplicons of L. huidobrensis in two fragments, whereas the original band was not cleaved in the other analyzed species. The presence of Dacnusa spp. DNA does not bias the assay, because the PCR conditions and the primer set here described do not amplify any tract of this endoparasitic wasp genome.

  8. NORMAL AND PATHOLOGICAL FRAGMENTATION OF RED BLOOD CELLS; THE PHAGOCYTOSIS OF THESE FRAGMENTS BY DESQUAMATED ENDOTHELIAL CELLS OF THE BLOOD STREAM; THE CORRELATION OF THE PEROXIDASE REACTION WITH PHAGOCYTOSIS IN MONONUCLEAR CELLS

    PubMed Central

    Doan, Charles A.; Sabin, Florence R.

    1926-01-01

    1. There is constantly some breaking down of red cells in the circulation by fragmentation. 2. The fragments of red cells, as well as whole red cells, are phagocytized and destroyed by clasmatocytes or endothelial phagocytes. 3. When there is an increase in fragmentation in abnormal or pathological states, desquamated endothelial cells of the blood stream, as well as the clasmatocytes of the tissues, increase proportionately and take in these fragments. These cells are to be distinguished from eosinophilic leucocytes by the nature of their granules, by the type of motility of the cells, and by a negative peroxidase test. 4. The desquamated endothelial cells, clasmatocytes, in the circulating blood are positive to the peroxidase test only when they have taken in positive material. 5. The monocytes show marked variations of the oxidase reaction in different species and to different techniques. With the Sato and Sekiya technique most monocytes of human blood are positive, while most of them in rabbit blood are negative, but both positive and negative reactions are found in both human and rabbit blood. PMID:19869165

  9. Physical organic studies of organometallic reactions

    SciTech Connect

    Bergman, Robert G.

    1981-01-01

    The mechanisms of reactions of organotransition metal complexes have only begun to be understood in detail during the last ten years. The complementary interaction of techniques and concepts developed earlier in studies of organic reaction mechanisms, with those commonly used in inorganic chetnistry, has played a crucial role in helping to elucidate organor.1etall.ic reaction mechanisms. A few systems in which this interaction has proved especially fruitful are discussed in this article.

  10. Distinguishing Heterodera filipjevi and H. avenae using polymerase chain reaction-restriction fragment length polymorphism and cyst morphology.

    PubMed

    Yan, Guiping; Smiley, Richard W

    2010-03-01

    The cereal cyst nematodes Heterodera filipjevi and H. avenae impede wheat production in the Pacific Northwest (PNW). Accurate identification of cyst nematode species and awareness of high population density in affected fields are essential for designing effective control measures. Morphological methods for differentiating these species are laborious. These species were differentiated using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) of internal transcribed spacer (ITS)-ribosomal (r)DNA with up to six restriction endonucleases (TaqI, HinfI, PstI, HaeIII, RsaI, and AluI). The method was validated by inspecting underbridge structures of cyst vulval cones. Grid soil sampling of an Oregon field infested by both species revealed that H. filipjevi was present at most of the infested grid sites but mixtures of H. avenae and H. filipjevi also occurred. These procedures also detected and differentiated H. filipjevi and H. avenae in soil samples from nearby fields in Oregon and H. avenae in samples from Idaho and Washington. Intraspecific polymorphism was not observed within H. filipjevi or PNW H. avenae populations based on the ITS-rDNA. However, intraspecific variation was observed between H. avenae populations occurring in the PNW and France. Methods described here will improve detection and identification efficiencies for cereal cyst nematodes in wheat fields.

  11. Metallographic study of metallic fragment of lunar surface material

    NASA Technical Reports Server (NTRS)

    Mints, R. I.; Petukhova, T. M.; Ivanov, A. V.

    1974-01-01

    A high precision investigation of a metallic fragment from the lunar material returned by the Soviet Luna 16 automatic station revealed three characteristic temperature intervals with different kinetics of solid solution decomposition. The following were found in the structure of the iron-nickel-cobalt alloy: (1) delta-phase and alpha-ferrite of diffusional, displacement origin in the grain boundary and acicular forms; and (2) martensite of isothermal and athermal nature, acicular, lamellar, massive, and dendritic. The diversity of the shapes of structural constituents is associated with the effect on their formation of elastic distortions and various mechanisms of deformation relaxation processes.

  12. Direct Reactions studies at RIBF new facility

    NASA Astrophysics Data System (ADS)

    Motobayashi, Tohru

    2009-10-01

    The RIKEN RI Beam Factory (RIBF) is the firs realization of new-generation facilities with beams of unstable nuclei. It is based on heavy-ion primary beams accelerated to 345 MeV/nucleon for all elements up to uranium. When the goal intensity, 1 pμA, is reached, RIBF allows production of about thousand new isotopes with the yield higher than 1 particle par day. Since the RI beam energy after production by in-flight fission and/or projectile fragmentation is be around 200-300 MeV/nucleon, the direct reaction is one of the useful processes for spectroscopy of uncle very far from the stability. Several experiments were proposed and a few of them have been performed with intense (currently) ^48Ca primary beams. The ZeroDegree Spectrometer, which is already operational, can be used to identify the product of a direct reaction in inverse kinematics coupled with, for example, measurement of γ-rays from excited states in the product. Construction of SAMURAI, a large-acceptance spectrometer, has been started. Decays of unbound states or breakup products from various types of direct reaction will be measured in coincidence. Experimental and theoretical issues to be considered for the specific conditions in this new opportunity will be discussed together with brief overview of near-term research.

  13. Taenia saginata: differential diagnosis of human taeniasis by polymerase chain reaction-restriction fragment length polymorphism assay.

    PubMed

    Nunes, Cáris Maroni; Dias, Ana Karina Kerche; Dias, Francisca Elda Ferreira; Aoki, Sérgio Moraes; de Paula, Henrique Borges; Lima, Luis Gustavo Ferraz; Garcia, José Fernando

    2005-08-01

    Speciation of Taenia in human stool is important because of their different clinical and epidemiological features. DNA analysis has recently become possible which overcomes the problems of differentiating human taeniid cestodes morphologically. In the present study, we evaluated PCR coupled to restriction fragment length polymorphism to differentiate Taenia solium from Taenia saginata eggs present in fecal samples from naturally infected patients. A different DraI-RFLP pattern: a two-band pattern (421 and 100 bp) for T. saginata and a three-band pattern (234, 188, and 99 bp) for T. solium was observed allowing the two species to be separated. The lower detection limit of the PCR-RFLP using a non-infected fecal sample prepared with a given number of T. saginata eggs was 34 eggs in 2 g stool sediment. The 521 bp mtDNA fragment was detected in 8 out of 12 Taenia sp. carriers (66.6%). Of these, three showed a T. solium pattern and five a T. saginata pattern.

  14. Fragmentation of displacement cascades into subcascades: A molecular dynamics study

    DOE PAGES

    Antoshchenkova, E.; Luneville, L.; Simeone, D.; ...

    2015-01-01

    The fragmentation of displacement cascades into subcascades in copper and iron has been investigated through the molecular dynamics technique. A two-point density correlation function has been used to analyze the cascades as a function of the primary knock-on (PKA) energy. This approach is used as a tool for detecting subcascade formation. The fragmentation can already be identified at the end of the ballistic phase. Its resulting evolution in the peak damage state discriminates between unconnected and connected subcascades. The damage zone at the end of the ballistic phase is the precursor of the extended regions that contain the surviving defects.more » A fractal analysis of the cascade exhibits a dependence on both the stage of the cascade development and the PKA energy. This type of analysis enables the minimum and maximum displacement spike energies together with the subcascade formation threshold energy to be determined. (C) 2014 Elsevier B.V. All rights reserved.« less

  15. Improved atmospheric trace gas measurements with an aircraft-based tandem mass spectrometer: Ion identification by mass-selected fragmentation studies

    NASA Astrophysics Data System (ADS)

    Reiner, Thomas; MöHler, Ottmar; Arnold, Frank

    1998-12-01

    We have built and employed an aircraft-borne triple quadrupole mass spectrometer (TQMS) for fragmentation studies of mass-selected ions in the upper troposphere and lower stratosphere. The fragmentation studies included both ambient and artificially produced ions relevant for the measurement of atmospheric trace gases by ion molecule reaction mass spectrometry (IMRMS) and led to an unambiguous identification of the chemical composition of important ions used for IMRMS measurements. Among these are the product ions of ion molecule reactions of CO3-(H2O)n and H3O+(H2O)n ions with HNO3, SO2, acetone, HCN, and methyl cyanide. These reactions have been studied in the laboratory, and ions having the same masses as the expected product ions have been previously observed in atmospheric IMRMS spectra. The present fragmentation studies are the first to actually identify the chemical composition of these ions during aircraft measurements in the upper troposphere and lower stratosphere and demonstrate that these ions can reliably be used for atmospheric trace gas measurements. Furthermore, the fragmentation studies gave indications for the existence and the possible identification of previously unknown ions. Among these the tentative identification of CO3-H2O2 offers the possibility for sensitive measurements of H2O2 by IMRMS. The fragmentation studies were accompanied by IMRMS measurements of atmospheric trace gases using the TQMS. Altitude profiles of HNO3, SO2, and lower limits for H2O2 are shown.

  16. Fragmentation Patterns and Mechanisms of Singly and Doubly Protonated Peptoids Studied by Collision Induced Dissociation

    NASA Astrophysics Data System (ADS)

    Ren, Jianhua; Tian, Yuan; Hossain, Ekram; Connolly, Michael D.

    2016-04-01

    Peptoids are peptide-mimicking oligomers consisting of N-alkylated glycine units. The fragmentation patterns for six singly and doubly protonated model peptoids were studied via collision-induced dissociation tandem mass spectrometry. The experiments were carried out on a triple quadrupole mass spectrometer with an electrospray ionization source. Both singly and doubly protonated peptoids were found to fragment mainly at the backbone amide bonds to produce peptoid B-type N-terminal fragment ions and Y-type C-terminal fragment ions. However, the relative abundances of B- versus Y-ions were significantly different. The singly protonated peptoids fragmented by producing highly abundant Y-ions and lesser abundant B-ions. The Y-ion formation mechanism was studied through calculating the energetics of truncated peptoid fragment ions using density functional theory and by controlled experiments. The results indicated that Y-ions were likely formed by transferring a proton from the C-H bond of the N-terminal fragments to the secondary amine of the C-terminal fragments. This proton transfer is energetically favored, and is in accord with the observation of abundant Y-ions. The calculations also indicated that doubly protonated peptoids would fragment at an amide bond close to the N-terminus to yield a high abundance of low-mass B-ions and high-mass Y-ions. The results of this study provide further understanding of the mechanisms of peptoid fragmentation and, therefore, are a valuable guide for de novo sequencing of peptoid libraries synthesized via combinatorial chemistry.

  17. Study of Electron Ionization and Fragmentation of Non-hydrated and Hydrated Tetrahydrofuran Clusters

    NASA Astrophysics Data System (ADS)

    Neustetter, Michael; Mahmoodi-Darian, Masoomeh; Denifl, Stephan

    2017-03-01

    Mass spectroscopic investigations on tetrahydrofuran (THF, C4H8O), a common model molecule of the DNA-backbone, have been carried out. We irradiated isolated THF and (hydrated) THF clusters with low energy electrons (electron energy 70 eV) in order to study electron ionization and ionic fragmentation. For elucidation of fragmentation pathways, deuterated TDF (C4D8O) was investigated as well. One major observation is that the cluster environment shows overall a protective behavior on THF. However, also new fragmentation channels open in the cluster. In this context, we were able to solve a discrepancy in the literature about the fragment ion peak at mass 55 u in the electron ionization mass spectrum of THF. We ascribe this ion yield to the fragmentation of ionized THF clusters.

  18. Energy release protection for pressurized systems. I - Review of studies into blast and fragmentation

    NASA Astrophysics Data System (ADS)

    Brown, S. J.

    1985-12-01

    Studies of blast and fragmentation hazards associated with a pressure system rupture are presented. Areas of concern related to blast hazards include the system energy (prior to its explosive failure), chemical characteristics of the media contained within a bursting pressure system, secondary explosions, and energy release. Such aspects of blast effect as height of the burst (in an above-the-ground explosion), dimensional effects of the explosive, multiple explosions, burning rate of the explosive, dynamic pressure, reflected pressure, and confinement (for explosions within an enclosed structure) are discussed. Also treated are hazards from fragments or missiles ejected (fragmentation hazards), including initial frament velocity, velocity retardation, range, blast-generated fragments (from adjacent structures), and media and soil ejection. Mathematical treatments and graphs representing the individual aspects of the blast and fragmentation phenomena are included.

  19. Fragmentation, labeling and biodistribution studies of KS1/4, a monoclonal antibody

    SciTech Connect

    Mohd, S.B.

    1987-01-01

    In this study, an IgG2a (KS1/4), a monoclonal antibody (MoAb) specific against a human lung adenocarcinoma (UCLA P-3) was successfully fragmented enzymatically to yield F(ab')/sub 2/ and Fab by using pepsin and papain, respectively. The kinetic of fragmentation of the MoAb was compared to that of human immunoglobulin G (IgG). A similar pattern of fragmentation was observed with both antibodies with a higher percentage yield of the F(ab')/sub 2/ and Fab obtained upon the fragmentation of the IgG by the enzymes. The KS1/4 and the two fragments were labeled with three different radionuclides, namely iodine-131, indium-111 and selenium-75. The radioiodination of the MoAb and the fragments was carried out by using a modified chloramine-T method. Radiometal labeling of the MoAb and the fragments with indium-111 was performed by using DTPA as a bifunctional chelating agent, while intrinsic labeling of the MoAb was done by culturing the hybridoma in the presence of /sup 75/Se-methionine. The biodistribution of the radiolabeled MoAb, F(ab')/sub 2/ and Fab fragments were performed by injecting the preparations intravenously into nude mice bearing human lung adenocarcinoma.

  20. Characterization of fragment emission in {sup 20}Ne(7-10 MeV/nucleon)+{sup 12}C reactions

    SciTech Connect

    Dey, Aparajita; Bhattacharya, C.; Bhattacharya, S.; Kundu, S.; Banerjee, K.; Mukhopadhyay, S.; Gupta, D.; Bhattacharjee, T.; Banerjee, S. R.; Bhattacharyya, S.; Rana, T. K.; Basu, S. K.; Saha, R.; Krishan, K.; Mukherjee, A.; Bandopadhyay, D.; Beck, C.

    2007-09-15

    The inclusive energy distributions of the complex fragments (3{<=}Z{<=}7) emitted from the bombardment of {sup 12}C by {sup 20}Ne beams with incident energies between 145 and 200 MeV have been measured in the angular range 10 deg.{<=}{theta}{sub lab}{<=}50 deg. Damped fragment yields in all the cases have been found to have the characteristic of emission from fully energy equilibrated composites. The binary fragment yields are compared with the standard statistical model predictions. Whereas Li and Be fragments yields are in agreement with statistical-model calculations, enhanced yields of entrance channel fragments (5{<=}Z{<=}7) indicate the survival of orbiting-like process in {sup 20}Ne+{sup 12}C system at these energies.

  1. An Isoratio Method to Study Free Energy and Temperature Effects in Intermediate Mass Fragments Produced in Heavy-Ion Collisions

    NASA Astrophysics Data System (ADS)

    Ma, Chun-Wang; Qiao, Chun-Yuan; Ding, Tian-Tian; Niu, Fei; Song, Yi-Dan; Niu, Yi-Fei

    2016-07-01

    An isoratio method, i.e., the isotopic (isotonic) ratio among three isotopes (isotones), is proposed to study the free energy and temperature effects in the intermediate mass fragments produced in heavy-ion collisions. The parameterizations for the free energy of nucleus at low temperature, which have been proposed in the framework of the density functional theory using the SKM skymre interaction, are adopted to calculate the temperature-dependent free energy of fragment. By analyzing the measured yields of fragments in the 140A MeV 58,64Ni + 9Be reactions, it is verified that the free energy in the isoratio is almost the same for different reactions. A temperature-dependent pairing-energy is introduced into the parameterizations for free energy, which reveals that the weakened pairing energy at the low temperature accounts for the weakened or disappearing odd-even staggering in isoratio. Supported by the Program for Science and Technology Innovation Talents in Universities of Henan Province under Grant No. 13HASTIT046, the Creative Experimental Project of National Undergraduate Students (CEPNU201510476017)

  2. Neutron production in coincidence with fragments from the 40Ca + H reaction at Elab=357A and 565A MeV

    NASA Astrophysics Data System (ADS)

    Tuve, C.; Albergo, S.; Boemi, D.; Caccia, Z.; Chen, C.-X.; Costa, S.; Crawford, H. J.; Cronqvist, M.; Engelage, J.; Greiner, L.; Guzik, T. G.; Knott, C. N.; Insolia, A.; Lindstrom, P. J.; Mitchell, J. W.; Potenza, R.; Russo, G. V.; Soutoul, A.; Testard, O.; Tricomi, A.; Tull, C. E.; Waddington, C. J.; Webber, W. R.; Wefel, J. P.

    1999-01-01

    Neutron production, in coincidence with fragments emitted in the 40Ca+H reaction at Elab=357A and 565A MeV, has been measured using a 3-module version of the multifunctional neutron spectrometer MUFFINS. The mean neutron multiplicities for neutrons detected in the angular range covered by MUFFINS (0°-3.2°) have been estimated from the comparison between the neutron cross sections, in coincidence with the fragments, and the elemental cross sections. We have found evidence for a preequilibrium emission of prompt neutrons in superposition to a ``slower'' deexcitation of the equilibrated remnant by emission of nucleons and fragments, as already seen in inclusive rapidity distributions. The energy dependence of the inclusive neutron production cross sections, measured in a previous work, is here interpreted as due to the stronger neutron focusing in the forward direction at the higher energy. Comparison with a BNV+phase space coalescence model is discussed.

  3. Total Syntheses, Fragmentation Studies, and Antitumor/Antiproliferative Activities of FR901464 and Its Low Picomolar Analog

    PubMed Central

    Albert, Brian J.; Sivaramakrishnan, Ananthapadmanabhan; Naka, Tadaatsu; Czaicki, Nancy L.

    2008-01-01

    FR901464 is a potent anticancer natural product that lowers the mRNA levels of oncogenes and tumor suppressor genes. In this article, we report a convergent enantioselective synthesis of FR901464, which was accomplished in 13 linear steps. Central to the synthetic approach was the diene-ene cross olefin metathesis reaction to generate the C6-C7 olefin without the use of protecting groups as the final step. Additional key reactions include a Zr/Ag-promoted alkynylation to set the C4 stereocenter, a mild and chemoselective Red-Al reduction, a reagent-controlled stereoselective Mislow-Evans-type [2,3]-sigmatropic rearrangement to install the C5 stereocenter, a Carreira asymmetric alkynylation to generate the C4′ stereocenter, and a highly efficient ring-closing metathesis-allylic oxidation sequence to form an unsaturated lactone. The decomposition pathways of FR901464's right fragment were studied under physiologically relevant conditions. Facile epoxide opening by β-elimination gave two enones, one of which could undergo dehydration via its hemiketal to form a furan. To prevent this decomposition pathway, a right fragment was then rationally designed and synthesized. This analog was 12 times more stable than the right fragment of the natural product. Using this more stable right fragment analog, an FR901464 analog, meayamycin, was then prepared in 13 linear steps. The inhibitions of human breast cancer MCF-7 cell proliferation by synthetic FR901464 and meayamycin were studied, and the GI50 values for these compounds were determined to be 1.1 nM and 10 pM, respectively. Thus, meayamycin is among the most potent anticancer small molecules that do not bind to either DNA or microtubule. PMID:17279752

  4. Analysis of the rDNA internal transcribed spacer region of the Fusarium species by polymerase chain reaction-restriction fragment length polymorphism

    PubMed Central

    ZARRIN, MAJID; GANJ, FARZANEH; FARAMARZI, SAMA

    2016-01-01

    The Fusarium species are a widely spread phytopathogen identified in an extensive variety of hosts. The Fusarium genus is one of the most heterogeneous fungi and is difficult to classify. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis is a useful method in detection of DNA polymorphism in objective sequences. The aim of the present study was to identify the phylogenetic associations and usefulness of the internal transcribed spacer (ITS) region as a genetic marker within the most clinically important strain of the Fusarium species. A total of 50 strains of Fusarium spp. were used in the study, including environmental, clinical and reference isolates. The primers ITS1 and ITS4 were used in the study. Two restriction enzymes, HaeIII and SmaI, were assessed for the digestion of PCR products. A PCR product of ~550-base pairs was generated for each Fusarium species. The digested products with HaeIII and SmaI demonstrated that the bands generated for the medically significant Fusarium species, including F. solani, F. oxysporum, F. verticillidea, F. proliferatum and F. fujikuri, have different restriction enzyme patterns. In conclusion, it appears that the PCR-RFLP method used in the present study produces a sufficient restriction profile for differentiation of the most medically significant Fusarium species. PMID:27073635

  5. Giardia duodenalis in Damascus, Syria: Identification of Giardia genotypes in a sample of human fecal isolates using polymerase chain reaction and restriction fragment length polymorphism analyzing method.

    PubMed

    Skhal, Dania; Aboualchamat, Ghalia; Al Nahhas, Samar

    2016-02-01

    Giardia duodenalis is a common gastrointestinal parasite that infects humans and many other mammals. It is most prevalent in many developing and industrialized countries. G. duodenalis is considered to be a complex species. While no morphological distinction among different assemblages exist, it can be genetically differentiated into eight major assemblages: A to H. The aim of this study was to determine the genetic heterogeneity of G. duodenalis in human isolates (a study conducted for the first time in Syria). 40 fecal samples were collected from three different hospitals during the hot summer season of 2014. Extraction of genomic DNA from all Giardia positive samples (based on a microscopic examination) was performed using QIAamp DNA Stool Mini Kit. β-giardin gene was used to differentiate between different Giardia assemblages. The 514 bp fragment was amplified using the Polymerase Chain Reaction method, followed by digestion in HaeIII restriction enzyme. Our result showed that genotype A was more frequent than genotype B, 27/40 (67.5%); 4/40 (10%) respectively. A mixed genotype of A+B was only detected in 9 isolates (22.5%). This is the first molecular study performed on G. duodenalis isolates in Syria in order to discriminate among the different genotypes. Further expanded studies using more genes are needed to detect and identify the Giardia parasite at the level of assemblage and sub-assemblage.

  6. Alpha resonant scattering for astrophysical reaction studies

    SciTech Connect

    Yamaguchi, H.; Kahl, D.; Nakao, T.; Wakabayashi, Y.; Kubano, S.; Hashimoto, T.; Hayakawa, S.; Kawabata, T.; Iwasa, N.; Teranishi, T.; Kwon, Y. K.; Binh, D. N.; Khiem, L. H.; Duy, N. G.

    2014-05-02

    Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of {sup 7}Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the {sup 7}Be(α,γ) reaction, and proposed a new cluster band in {sup 11}C.

  7. Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of {sup 238}U projectiles at 1A GeV

    SciTech Connect

    Alvarez-Pol, H.; Benlliure, J.; Casarejos, E.; Cortina-Gil, D.; Fernandez-Dominguez, B.; Pereira, J.; Audouin, L.; Enqvist, T.; Schmidt, K.-H.; Yordanov, O.; Junghans, A. R.; Jurado, B.; Rejmund, F.

    2010-10-15

    The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of {sup 238}U projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: {sup 205}Pt, {sup 207-210}Au, {sup 211-216}Hg, {sup 214-217}Tl, {sup 215-220}Pb, {sup 219-224}Bi, {sup 223-227}Po, {sup 225-229}At, {sup 230,231}Rn, and {sup 233}Fr. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

  8. An (e, 2e + ion) study of low-energy electron-impact ionization and fragmentation of tetrahydrofuran with high mass and energy resolutions

    SciTech Connect

    Ren, Xueguang Pflüger, Thomas; Weyland, Marvin; Baek, Woon Yoon; Rabus, Hans; Ullrich, Joachim; Dorn, Alexander

    2014-10-07

    We study the low-energy (E{sub 0} = 26 eV) electron-impact induced ionization and fragmentation of tetrahydrofuran using a reaction microscope. All three final-state charged particles, i.e., two outgoing electrons and one fragment ion, are detected in triple coincidence such that the momentum vectors and, consequently, the kinetic energies for charged reaction products are determined. The ionic fragments are clearly identified in the experiment with a mass resolution of 1 amu. The fragmentation pathways of tetrahydrofuran are investigated by measuring the ion kinetic energy spectra and the binding energy spectra where an energy resolution of 1.5 eV has been achieved using the recently developed photoemission electron source. Here, we will discuss the fragmentation reactions for the cations C{sub 4}H{sub 8}O{sup +}, C{sub 4}H{sub 7}O{sup +}, C{sub 2}H{sub 3}O{sup +}, C{sub 3}H{sub 6}{sup +}, C{sub 3}H{sub 5}{sup +}, C{sub 3}H{sub 3}{sup +}, CH{sub 3}O{sup +}, CHO{sup +}, and C{sub 2}H{sub 3}{sup +}.

  9. Precursor Ion Scan Mode-Based Strategy for Fast Screening of Polyether Ionophores by Copper-Induced Gas-Phase Radical Fragmentation Reactions.

    PubMed

    Crevelin, Eduardo J; Possato, Bruna; Lopes, João L C; Lopes, Norberto P; Crotti, Antônio E M

    2017-04-04

    The potential of copper(II) to induce gas-phase fragmentation reactions in macrotetrolides, a class of polyether ionophores produced by Streptomyces species, was investigated by accurate-mass electrospray tandem mass spectrometry (ESI-MS/MS). Copper(II)/copper(I) transition directly induced production of diagnostic acylium ions with m/z 199, 185, 181, and 167 from α-cleavages of [macrotetrolides + Cu](2+). A UPLC-ESI-MS/MS methodology based on the precursor ion scan of these acylium ions was developed and successfully used to identify isodinactin (1), trinactin (2), and tetranactin (3) in a crude extract of Streptomyces sp. AMC 23 in the precursor ion scan mode. In addition, copper(II) was also used to induce radical fragmentation reactions in the carboxylic acid polyether ionophore nigericin. The resulting product ions with m/z 755 and 585 helped to identify nigericin in a crude extract of Streptomyces sp. Eucal-26 by means of precursor ion scan experiments, demonstrating that copper-induced fragmentation reactions can potentially identify different classes of polyether ionophores rapidly and selectively.

  10. Theoretical studies of chemical reaction dynamics

    SciTech Connect

    Schatz, G.C.

    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.

  11. a Study of Proton Induced Nuclear Fragmentation in the Threshold Region: 1 TO 20 GEV

    NASA Astrophysics Data System (ADS)

    Sangster, Thomas Craig

    This thesis contains the details of the experimental set-up and final results of BNL E-778. The experimental objective was to study proton induced nuclear fragmentation using an internal gas jet target facility that was specifically designed for this experiment and installed in the AGS main ring. The fragment telescopes were designed to measure a broad range of fragment charge (2 to 14) and kinetic energy (5 to 100 MeV). Using a mixed gas target (1% or 3% Xe with H(,2)), normalized fragment production cross sections were obtained by separately measuring p-p elastic production from the H(,2) component. Fragment production cross sections are observed to rise dramatically ((TURN) x 10) for incident proton energies between 1 and 10 GeV, while above 10 GeV, fragment production appears to be independent of the incident proton energy. The measured differential cross sections (above 10 GeV) are found to agree (within 20%) with the differential cross sections measured during a previous internal target experiment (E-591) conducted at FNAL, where the lowest available proton energies were 50 GeV. The measured fragment kinetic energy spectra (above 10 GeV) are fit with a functional form motivated by the observation that fragment production in an excited nuclear system is consistent with a critical phenomenon (a liquid -gas phase transition). The failure of this functional form at the lowest available incident energies (below 10 GeV) is interpreted as the observation of an additional fragment production mechanism. Recent theoretical and experimental evidence for an asymmetric fission process (binary decay), is used to modify the original functional form for the two-component spectra. It is concluded that, in the threshold region, two fragment production mechanisms are observed. Although insufficient information is available to uniquely separate the two components, certain features of the asymmetric fission mechanism are identified. The observed p-nucleus systematics are also

  12. A study of the collisional fragmentation problem using the Gamma distribution approximation.

    PubMed

    Kostoglou, M; Karabelas, A J

    2006-11-15

    The nonlinear fragmentation population balance formulation has been elevated in recent years from a prototype for studying nonlinear integro-differential equations to a vehicle for analyzing and understanding several physicochemical processes of technological interest. The so-called pure collisional fragmentation, which is the particular mode of nonlinear fragmentation induced by collisions between particles, is studied here. It is shown that the corresponding population balance equation admits large time asymptotic (self-similarity) solutions for homogeneous fragmentation and collision functions (kernels). The self-similar solutions are given in closed form for some simple kernels. Based on the shape of the self-similar solutions the method of moments with Gamma distribution approximation is employed for transient solution (from initial state to establishment of the asymptotic shape) of the collisional fragmentation equation. These solutions are presented for several sets of parameters and their behavior is discussed rather extensively. The present study is similar to the one has already been performed for the case of the much simpler linear fragmentation equation [G. Madras, B.J. McCoy, AIChE J. 44 (1998) 647].

  13. Electrospray mass spectral fragmentation study of N,N'-disubstituted imidazolium ionic liquids.

    PubMed

    Lesimple, Alain; Mamer, Orval; Miao, Weishi; Chan, Tak Hang

    2006-01-01

    The tandem positive electrospray mass spectrometry (ESMS(n)) fragmentation of ionic liquids incorporating the 1-methyl-imidazolium ring substituted on N(II) with an alkyl chain functionalized with an alcohol, carboxylic acid, or an iodobenzyl or iodobenzoyl ester is presented for the first time. The influence of chain length and function is studied. Esterified structures led to intense CID fragments lacking the imidazolium ring allowing full characterization of the ester moiety. Fragment ion compositions for this interesting and newly important class of compounds are established through accurate mass data and deuterium labeling. The presence of the cationic ring system produces intense even electron molecular cations in electrospray that undergo multiple stages of CID to yield fragments which often are radical cations. Unusual losses of methyl and hydrogen radicals are frequently noted.

  14. Rotational and neutron-hole states in {sup 43}S via the neutron knockout and fragmentation reactions

    SciTech Connect

    Riley, L. A.; Hosier, K. E.; Adrich, P.; Baugher, T. R.; Bazin, D.; Diget, C. A.; Weisshaar, D.; Brown, B. A.; Cook, J. M.; Gade, A.; Garland, D. A.; Glasmacher, T.; Ratkiewicz, A.; Siwek, K. P.; Cottle, P. D.; Kemper, K. W.; Tostevin, J. A.

    2009-09-15

    The recent assertion that shape coexistence occurs in the neutron-rich isotope {sup 43}S implies that a state observed at 940 keV in a previous study is a rotational excitation of the deformed ground state. Here we use results from two intermediate-energy reactions to demonstrate that this state--assigned an energy of 971 keV in the present work--is indeed a rotational state. This result strengthens the case for shape coexistence in {sup 43}S.

  15. Neutrino-nucleus reactions based on recent structure studies

    SciTech Connect

    Suzuki, Toshio

    2015-05-15

    Neutrino-nucleus reactions are studied with the use of new shell model Hamiltonians, which have proper tensor components in the interactions and prove to be successful in the description of Gamow-Teller (GT) strengths in nuclei. The new Hamiltonians are applied to obtain new neutrino-nucleus reaction cross sections in {sup 12}C, {sup 13}C, {sup 56}Fe and {sup 56}Ni induced by solar and supernova neutrinos. The element synthesis by neutrino processes in supernova explosions is discussed with the new cross sections. The enhancement of the production yields of {sup 7}Li, {sup 11}B and {sup 55}Mn is obtained while fragmented GT strength in {sup 56}Ni with two-peak structure is found to result in smaller e-capture rates at stellar environments. The monopole-based universal interaction with tensor force of π+ρ meson exchanges is used to evaluate GT strength in {sup 40}Ar and ν-induced reactions on {sup 40}Ar. It is found to reproduce well the experimental GT strength in {sup 40}Ar.

  16. A simple and rapid nested polymerase chain reaction-restriction fragment length polymorphism technique for differentiation of pathogenic and nonpathogenic Leptospira spp.

    PubMed

    Djadid, Navid Dinparast; Ganji, Zahra Faghanzadeh; Gouya, Mohammad Mehdi; Rezvani, Mahmood; Zakeri, Sedigheh

    2009-03-01

    A rapid and specific nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) has been developed to detect and differentiate pathogenic and nonpathogenic Leptospira spp. Leptospiral genomic DNA was extracted from suspected human sera using an improved method of standard phenol-chloroform, and specific primers have been used to amplify 16S ribosomal RNA from all pathogenic and nonpathogenic Leptospira spp. The PCR products of all nonpathogenic species were digested with ApoI enzyme, but not pathogenic. To evaluate this assay, we analyzed 283 serum samples collected from suspected patients with leptospirosis. Nested PCR assay confirmed that 42 (14.8%) of 283 samples harbored Leptospira infection, and RFLP assay confirmed 38 (90.5%) of 42 and 4 (9.5%) of 42 positive cases had pathogenic and nonpathogenic Leptospira spp., respectively. Based on sequencing results, Leptospira interrogans, Leptospira kirschneri, and Leptospira wolffii and nonpathogenic Leptospira biflexa and Leptospira genomospecies 3 have been detected among analyzed samples. The nested PCR-RFLP assay developed in this study fulfills this requirement in the early stage of infection.

  17. Determination of integron frequency by a polymerase chain reaction-restriction fragment length polymorphism method in multidrug-resistant Escherichia coli, which causes urinary tract infections.

    PubMed

    Fallah, Fatemeh; Karimi, Abdollah; Goudarzi, Mehdi; Shiva, Farideh; Navidinia, Masoumeh; Jahromi, Mana Hadipour; Sajadi Nia, Raheleh Sadat

    2012-12-01

    The purpose of this study was to determine the presence of integrons in Escherichia coli, which cause urinary tract infections, and to define the association between integrons and antimicrobial susceptibility. Susceptibility of 200 isolates from urine samples of patients suffering from urinary tract infections to 13 antibiotics was determined by the Kirby-Bauer disk diffusion method. The existence of class1 and 2 integrons in resistant isolates was assessed by polymerase chain reaction-restriction fragment length polymorphism and sequencing. Antibiotic resistance patterns were observed as follows: amoxicillin 78%, tetracycline 76.1%, co-trimoxazole 67.7%, cephalotin 60%, nalidixic acid 57.4%, chloramphenicol 49%, gentamicin 46.4%, ceftazidim 38.1%, ciprofloxacin 36.2%, nitrofurantoin 33.5%, amikacin 32.1%, norfloxacin 36.1%, and imipenem 27.1%. Of 200 isolates, 155 (77.5%) were multidrug resistant (MDR). The existence of integrons was confirmed in 50.3% of isolates. Three class 1 integron types, aadA2 being the most frequently found, and four class 2 integron types are described. Significant association between resistance to gentamicin, co-trimoxazole, cephalotin, ceftazidim, imipenem, chloramphenicol, and nalidixic acid with the existence of integrons was observed. Multidrug resistance suggests that the strategy for treatment of patients with E.coli infections needs to be revised. Furthermore, it was shown that integrons may be partly responsible for multidrug resistance. Imipenem and norfloxacin were the most effective antibiotics against isolates.

  18. Laser Studies of Gas Phase Radical Reaction.

    DTIC Science & Technology

    1985-11-30

    1nai Irvest-aator Or.G. Hancock gn; FILE CO, Contr3ctor : Oxford University . Physical Chemistry Laboratory. South Parks Road.AD-A 193 689 Oxfor o~d...HIF spectrum and study of reaction of this and the CCI radical with atoms vi) sea;rchtrr; f(r FC) ’ndlict of the 0 *CF, reaction. OXFORD UNIVERSITY -. - SOUTH...0 Awtilability Codes I Avail ’and/or Dis Spcal0 Spoo OXFORD UNIVERSITY Tt SOUTH PARKS ROAD OXFCRD OXFORD � X3Z U.S. Army Contract DAJA45-85-C-0034

  19. Molecular Beam Studies of Low Energy Reactions.

    DTIC Science & Technology

    1983-03-31

    COMPLETING PORN . REPORT NUMBER 1 2. GOVT ACCESSION NO. S. RECIPIENT’S CATALOG NUMBER A D A Oaq J- 4. TITLE (And Subtitle) . TYPE OF REPORT & PERIOD COVERED...Gatlinburg, Tenn . in 1981. 2+ c) Studies were made of the charge transfer reaction Ar + Ar 4 2+ Ar + Ar at relative energies from 2 to 1000 eV. Reasons for

  20. Photocross-Linked Peptide-Protein Complexes Analysis: A Comparative Study of CID and ETD Fragmentation Modes

    NASA Astrophysics Data System (ADS)

    Clavier, Séverine; Bolbach, Gérard; Sachon, Emmanuelle

    2015-06-01

    Protein-protein interactions are among the keys to organizing cellular processes in space and time. One of the only direct ways to identify such interactions in their cellular environment is to covalently bond the interacting partners to fix the interaction. Photocross-linking in living cells is thus a very promising technique. The feasibility of in cellulo photocross-linking reactions has been shown and mass spectrometry is a tool of choice to analyze photocross-linked proteins. However, the interpretation of the MS and MS/MS spectra of photocross-linked peptides remains one of the most important bottlenecks of the method and still limits its potential for large-scale applications (interactomics). Fundamental studies are still necessary to understand and characterize the fragmentation behavior of photocross-linked peptides. Here, we report the successful identification of the interaction sites in a well-characterized model of in vitro interaction between a protein and a peptide. We describe in detail the fragmentation pattern of these photocross-linked species in order to identify trends that could be generalized. In particular, we compare CID and ETD fragmentation modes (and HCD in a lesser extent), demonstrating the complementarity of both methods and the advantage of ETD for the analysis of photocross-linked species. The information should help further development of dedicated software to properly score MS/MS spectra of photocross-linked species.

  1. Laser Studies of Gas Phase Radical Reactions.

    DTIC Science & Technology

    1989-01-01

    Acremonium chrysogenum , was prepared according to the published procedure [6]. This fungal enzyme had a specific activity of 0.023 IUmg1, and was estimated to...Dist-lbitionj Avdielbiity Codes jAvail atidjor Dist 6a A-I . p -1- Laser Studies of Gas Phase Radical Reactions G. Hancock Physical Chemistry...some additional experiments concerning the formation of carbene radicals in liquid phase enzyme cleavage studies are described. Keywords Laser

  2. First isomeric quadrupole moment measured in fragmentation reactions: The case of {sup 61}Fe{sup m}(9/2{sup +})

    SciTech Connect

    Vermeulen, N.; Yordanov, D. T.; Neyens, G.; Chamoli, S. K.; Hass, M.; Goldring, G.; Singh, B. S. Nara; Daugas, J. M.; Delaroche, J. P.; Girod, M.; Goutte, H.; Morel, P.; Perru, O.; Peru, S.; Roig, O.; Oliveira-Santos, F. de; Grevy, S.; Perrot, L.; Stefan, I.

    2007-05-15

    This paper demonstrates the feasibility of quadrupole moment measurements on isomeric levels populated in projectile fragmentation reactions. The neutron-rich {sup 61}Fe(9/2{sup +}) [E*= 861 keV, T{sub 1/2}= 239(5) ns] isomer was produced and spin aligned by the intermediate energy fragmentation of a {sup 64}Ni beam and implanted in a Cd single crystal. Its spectroscopic quadrupole moment |Q{sub s}|=41(6) e fm{sup 2} agrees with mean-field based calculations using the finite-range Gogny force, suggesting a moderately deformed shape characterized by an intrinsic charge quadrupole moment Q{sub 0}=-85 e fm{sup 2} or Q{sub 0}=+115 e fm{sup 2}. The present measurement paves the way for future determinations of isomeric quadrupole moments in more exotic nuclei.

  3. Vibration from freight trains fragments sleep: A polysomnographic study

    PubMed Central

    Smith, Michael G.; Croy, Ilona; Hammar, Oscar; Persson Waye, Kerstin

    2016-01-01

    As the number of freight trains on railway networks increases, so does the potential for vibration exposure in dwellings nearby to freight railway lines. Nocturnal trains in particular are of particular importance since night-time exposure may interfere with sleep. The present work investigates the impact of vibration and noise from night-time freight trains on human sleep. In an experimental polysomnographic laboratory study, 24 young healthy volunteers with normal hearing were exposed to simulated freight pass-bys with vibration amplitudes of 0.7 and 1.4 mm/s either 20 or 36 times during the night. Stronger vibrations were associated with higher probabilities of event-related arousals and awakenings (p < 0.001), and sleep stage changes (p < 0.05). Sleep macrostructure was most affected in high vibration nights with 36 events, with increased wakefulness (p < 0.05), reduced continual slow wave sleep (p < 0.05), earlier awakenings (p < 0.05) and an overall increase in sleep stage changes (p < 0.05). Subjects reported sleep disturbance due to vibration (F(4,92) = 25.9, p < 0.001) and noise (F(4,92) = 25.9, p < 0.001), with the number of trains having an effect only for the 0.7 mm/s condition (p < 0.05). The findings show that combined vibration and noise from railway freight affects the natural rhythm of sleep, but extrapolation of significance for health outcomes should be approached with caution. PMID:27090401

  4. Vibration from freight trains fragments sleep: A polysomnographic study.

    PubMed

    Smith, Michael G; Croy, Ilona; Hammar, Oscar; Persson Waye, Kerstin

    2016-04-19

    As the number of freight trains on railway networks increases, so does the potential for vibration exposure in dwellings nearby to freight railway lines. Nocturnal trains in particular are of particular importance since night-time exposure may interfere with sleep. The present work investigates the impact of vibration and noise from night-time freight trains on human sleep. In an experimental polysomnographic laboratory study, 24 young healthy volunteers with normal hearing were exposed to simulated freight pass-bys with vibration amplitudes of 0.7 and 1.4 mm/s either 20 or 36 times during the night. Stronger vibrations were associated with higher probabilities of event-related arousals and awakenings (p < 0.001), and sleep stage changes (p < 0.05). Sleep macrostructure was most affected in high vibration nights with 36 events, with increased wakefulness (p < 0.05), reduced continual slow wave sleep (p < 0.05), earlier awakenings (p < 0.05) and an overall increase in sleep stage changes (p < 0.05). Subjects reported sleep disturbance due to vibration (F(4,92) = 25.9, p < 0.001) and noise (F(4,92) = 25.9, p < 0.001), with the number of trains having an effect only for the 0.7 mm/s condition (p < 0.05). The findings show that combined vibration and noise from railway freight affects the natural rhythm of sleep, but extrapolation of significance for health outcomes should be approached with caution.

  5. FALP and CRESU studies of ionic reactions

    NASA Astrophysics Data System (ADS)

    Rowe, B. R.; Canosa, A.; Le Page, V.

    1995-11-01

    Results obtained from the study of ionic reactions at the University of Rennes are reviewed. A brief description of the apparatus available in our laboratory is given. The historical evolution of the flowing afterglow device is emphasized as it is directly connected to one of the major puzzling questions in dissociative recombination studies: what is the rate coefficient for the dissociative recombination of H3+ in its ground state? Special attention is given to the dissociative recombination process which until recently was the main topic studied in Rennes. A compilation of our measurements of branching ratios and rate coefficients is presented. Results from other authors are also outlined with particular attention paid to H3+. Electron attachment and ion/molecule reactions studied with the flowing afterglow Langmuir probe mass spectrometer are presented. The first results of ion/molecule reactions at very low temperatures have been recently obtained with the CRESU apparatus available in Rennes. Comparison with measurements carried out in Meudon at lower pressures is made and discussed.

  6. Strong enhancement of dynamical emission of heavy fragments in the neutron-rich {sup 124}Sn+{sup 64}Ni reaction at 35A MeV

    SciTech Connect

    Russotto, P.; Amorini, F.; Cavallaro, S.; Di Toro, M.; Giustolisi, F.; Porto, F.; Rizzo, F.; De Filippo, E.; Pagano, A.; Cardella, G.; Lanzano, G.; Papa, M.; Pirrone, S.; Piasecki, E.; Auditore, L.; Trifiro, A.; Trimarchi, M.

    2010-06-15

    A quantitative comparison is made between the absolute cross sections associated with statistical and dynamical emission of heavy fragments in the {sup 124}Sn+{sup 64}Ni and {sup 112}Sn+{sup 58}Ni collisions experimentally investigated at 35A MeV beam energy using the multidetector CHIMERA. The result shows that the dynamical process is about twice as probable in the neutron-rich {sup 124}Sn+{sup 64}Ni system as in the {sup 112}Sn+{sup 58}Ni neutron-poor one. This unexpected and significant difference indicates that the reaction mechanism is strongly dependent on the entrance-channel isospin (N/Z) content.

  7. Bulk plasma fragmentation in a C4F8 inductively coupled plasma: A hybrid modeling study

    NASA Astrophysics Data System (ADS)

    Zhao, Shu-Xia; Zhang, Yu-Ru; Gao, Fei; Wang, You-Nian; Bogaerts, Annemie

    2015-06-01

    A hybrid model is used to investigate the fragmentation of C4F8 inductive discharges. Indeed, the resulting reactive species are crucial for the optimization of the Si-based etching process, since they determine the mechanisms of fluorination, polymerization, and sputtering. In this paper, we present the dissociation degree, the density ratio of F vs. CxFy (i.e., fluorocarbon (fc) neutrals), the neutral vs. positive ion density ratio, details on the neutral and ion components, and fractions of various fc neutrals (or ions) in the total fc neutral (or ion) density in a C4F8 inductively coupled plasma source, as well as the effect of pressure and power on these results. To analyze the fragmentation behavior, the electron density and temperature and electron energy probability function (EEPF) are investigated. Moreover, the main electron-impact generation sources for all considered neutrals and ions are determined from the complicated C4F8 reaction set used in the model. The C4F8 plasma fragmentation is explained, taking into account many factors, such as the EEPF characteristics, the dominance of primary and secondary processes, and the thresholds of dissociation and ionization. The simulation results are compared with experiments from literature, and reasonable agreement is obtained. Some discrepancies are observed, which can probably be attributed to the simplified polymer surface kinetics assumed in the model.

  8. Theoretical study of the fragmentation pathways of norbornane in its doubly ionized ground state.

    PubMed

    Knippenberg, Stefan; Hajgató, Balazs; François, Jean-Pierre; Deleuze, Michael S

    2007-10-25

    The potential energy surface of norbornane in its dicationic singlet ground state has been investigated in detail using density functional theory along with the nonlocal hybrid and gradient-corrected Becke three-parameter Lee-Yang-Parr functional (B3LYP) and the cc-pVDZ basis set. For the sake of more quantitative insight into the chemical reactions induced by double ionization of norbornane, this study was supplemented by a calculation of basic thermodynamic state functions coupled to a focal point analysis of energy differences obtained using correlation treatments and basis sets of improving quality, enabling an extrapolation of these energy differences at the CCSD(T) level in the limit of an asymptotically complete (cc-pV infinity Z) basis set. Our results demonstrate the likelihood of an ultrafast intramolecular rearrangement of the saturated hydrocarbon cage after a sudden removal of two electrons into a kinetically metastable five-membered cyclic C5H8+-CH+-CH3 intermediate, prior to a Coulomb explosion into C5H7+=CH2 and CH3+ fragments, which might explain a tremendous rise of electron-impact (e, 2e) ionization cross sections at electron binding energies around the double-ionization threshold. The first step is straightforward and strongly exothermic (DeltaH298 = -114.0 kcal mol-1). The second step is also exothermic (DeltaH298 = -10.2 kcal mol-1) but requires an activation enthalpy (DeltaH298) of 39.7 kcal/mol. The various factors governing the structure of this intermediate, such as electrostatic interactions, inductive effects, cyclic strains, and methylenic hyperconjugation interactions, are discussed in detail.

  9. Identification of Pork Contamination in Meatballs of Indonesia Local Market Using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) Analysis

    PubMed Central

    Erwanto, Yuny; Abidin, Mohammad Zainal; Sugiyono, Eko Yasin Prasetyo Muslim; Rohman, Abdul

    2014-01-01

    This research applied and evaluated a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using cytochrome b gene to detect pork contamination in meatballs from local markets in Surabaya and Yogyakarta regions, Indonesia. To confirm the effectiveness and specificity of this fragment, thirty nine DNA samples from different meatball shops were isolated and amplified, and then the PCR amplicon was digested by BseDI restriction enzyme to detect the presence of pork in meatballs. BseDI restriction enzyme was able to cleave porcine cytochrome b gene into two fragments (131 bp and 228 bp). Testing the meatballs from the local market showed that nine of twenty meatball shops in Yogyakarta region were detected to have pork contamination, but there was no pork contamination in meatball shops in Surabaya region. In conclusion, specific PCR amplification of cytochrome b gen and cleaved by BseDI restriction enzymes seems to be a powerful technique for the identification of pork presence in meatball because of its simplicity, specificity and sensitivity. Furthermore, pork contamination intended for commercial products of sausage, nugget, steak and meat burger can be checked. The procedure is also much cheaper than other methods based on PCR, immunodiffusion and other techniques that need expensive equipment. PMID:25178301

  10. Comments on "a study of the collisional fragmentation problem using the gamma distribution approximation".

    PubMed

    Nadarajah, Saralees

    2007-04-15

    M. Kostoglou and A.J. Karabelas [J. Colloid Interface Sci. 303 (2006) 419-429] proposed using a gamma distribution approximation to study a collisional fragmentation problem. This approximation involved two types of integrals and the use of continued fraction expansions for their computation. In this Comment, explicit expressions are derived for computing the integrals.

  11. COSMO-DFTr study of cellulosic fragments: structural features, relative energy, and hydration energies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The study of cellulosic fragments by DFTr is a continuation of our efforts to produce quality structural data that will be valuable to those working in the field of cellulose structure and enzymatic degradation. Using a reduced basis set and density functional DFTr(B3LYP), the time and computer dem...

  12. DNA Flexibility Studied by Covalent Closure of Short Fragments into Circles

    NASA Astrophysics Data System (ADS)

    Shore, David; Langowski, Jorg; Baldwin, Robert L.

    1981-08-01

    The ring closure probability, or j factor, has been measured for DNA restriction fragments of defined sequence bearing EcoRI cohesive ends and ranging in size from 126 to 4361 base pairs (bp). The j factor is defined as the ratio of the equilibrium constants for cyclization and for bimolecular association via the cohesive ends. The end-joining reactions are fast compared to covalent closure of the cohesive ends by T4 DNA ligase. The rate of ligase closure is shown to be proportional to the equilibrium fraction of DNA molecules with joined cohesive ends, both in cyclization and in bimolecular association reactions. The j factor changes by less than 10-fold between 242 and 4361 bp, whereas it decreases by more than 100-fold between 242 and 126 bp as the DNA reaches the size range of the persistence length (150 bp). As regards ring closure, short DNA fragments are surprisingly flexible. These data are in good agreement with predictions by others for the ring closure probability of a wormlike chain.

  13. Fragmentation studies and electrospray ionization mass spectrometry of lapachol: protonated, deprotonated and cationized species.

    PubMed

    Vessecchi, Ricardo; Emery, Flavio S; Galembeck, Sérgio E; Lopes, Norberto P

    2010-07-30

    Electrospray ionization mass spectrometric analysis of lapachol (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone) was accomplished in order to elucidate the gas-phase dissociation reactions of this important biologically active natural product. The occurrence of protonated and cationized species in the positive mode and of deprotonated species in the negative mode was explored by means of collision-induced dissociation (CID) experiments. For the protonated molecule, the H(2)O and C(4)H(8) losses occur by two competitive channels. For the deprotonated molecule, the even-electron rule is not conserved, and the radicalar species are eliminated by formation of distonic anions. The fragmentation mechanism for each ion was suggested on the basis of computational thermochemistry. Atomic charges, relative energies, and frontier orbitals were employed aiming at a better understanding of the gas-phase reactivity of lapachol. Potential energy surfaces for fragmentation reactions were obtained by the B3LYP/6-31+G(d,p) model.

  14. Chameleon fragmentation

    SciTech Connect

    Brax, Philippe

    2014-02-01

    A scalar field dark energy candidate could couple to ordinary matter and photons, enabling its detection in laboratory experiments. Here we study the quantum properties of the chameleon field, one such dark energy candidate, in an ''afterglow'' experiment designed to produce, trap, and detect chameleon particles. In particular, we investigate the possible fragmentation of a beam of chameleon particles into multiple particle states due to the highly non-linear interaction terms in the chameleon Lagrangian. Fragmentation could weaken the constraints of an afterglow experiment by reducing the energy of the regenerated photons, but this energy reduction also provides a unique signature which could be detected by a properly-designed experiment. We show that constraints from the CHASE experiment are essentially unaffected by fragmentation for φ{sup 4} and 1/φ potentials, but are weakened for steeper potentials, and we discuss possible future afterglow experiments.

  15. Soil pretreatment and fast cell lysis for direct polymerase chain reaction from forest soils for terminal restriction fragment length polymorphism analysis of fungal communities.

    PubMed

    Cheng, Fei; Hou, Lin; Woeste, Keith; Shang, Zhengchun; Peng, Xiaobang; Zhao, Peng; Zhang, Shuoxin

    Humic substances in soil DNA samples can influence the assessment of microbial diversity and community composition. Using multiple steps during or after cell lysis adds expenses, is time-consuming, and causes DNA loss. A pretreatment of soil samples and a single step DNA extraction may improve experimental results. In order to optimize a protocol for obtaining high purity DNA from soil microbiota, five prewashing agents were compared in terms of their efficiency and effectiveness in removing soil contaminants. Residual contaminants were precipitated by adding 0.6mL of 0.5M CaCl2. Four cell lysis methods were applied to test their compatibility with the pretreatment (prewashing+Ca(2+) flocculation) and to ultimately identify the optimal cell lysis method for analyzing fungal communities in forest soils. The results showed that pretreatment with TNP+Triton X-100+skim milk (100mM Tris, 100mM Na4P2O7, 1% polyvinylpyrrolidone, 100mM NaCl, 0.05% Triton X-100, 4% skim milk, pH 10.0) removed most soil humic contaminants. When the pretreatment was combined with Ca(2+) flocculation, the purity of all soil DNA samples was further improved. DNA samples obtained by the fast glass bead-beating method (MethodFGB) had the highest purity. The resulting DNA was successfully used, without further purification steps, as a template for polymerase chain reaction targeting fungal internal transcribed spacer regions. The results obtained by terminal restriction fragment length polymorphism analysis indicated that the MethodFGB revealed greater fungal diversity and more distinctive community structure compared with the other methods tested. Our study provides a protocol for fungal cell lysis in soil, which is fast, convenient, and effective for analyzing fungal communities in forest soils.

  16. Multi-fragment site-directed mutagenic overlap extension polymerase chain reaction as a competitive alternative to the enzymatic assembly method.

    PubMed

    Wäneskog, Marcus; Bjerling, Pernilla

    2014-01-01

    Methods for introducing multiple site-directed mutations are important experimental tools in molecular biology. Research areas that use these methods include the investigation of various protein modifications in cellular processes, modifying proteins for efficient recombinant expression, and the stabilization of mRNAs to allow for increased protein expression. Introducing multiple site-directed mutations is also an important tool in the field of synthetic biology. There are two main methods used in the assembling of fragments generated by mutagenic primers: enzymatic assembly and overlap extension polymerase chain reaction (OE-PCR). In this article, we present an improved OE-PCR method that can be used for the generation of large DNA fragments (up to 7.4 kb) where at least 13 changes can be introduced using a genomic template. The improved method is faster (due to fewer reaction steps) and more accurate (due to fewer PCR cycles), meaning that it can effectively compete with the enzymatic assembly method. Data presented here show that the site-directed mutations can be introduced anywhere between 50 and 1800 bp from each other. The method is highly reliable and predicted to be applicable to most DNA engineering when the introduction of multiple changes in a DNA sequence is required.

  17. Computational Hydrocode Study of Target Damage due to Fragment-Blast Impact

    SciTech Connect

    Hatch-Aguilar, T; Najjar, F; Szymanski, E

    2011-03-24

    ), Pressure-Impulse (PI) and Time of Duration (TD). Other peculiarities include the radial decrease in pressure from the source, any fireball size measurement, and subsequent increase in temperature from the passing of the shockwave through the surrounding medium. In light of all of these metrics, the loading any object receives from a blast event becomes intricately connected to the distance between itself and the source. Because of this, a clear distinction is made between close-in effects and those from a source far away from the object of interest. Explosively generated fragments on the other hand are characterized by means of their localized damage potential. Metrics such as whether the fragment penetrates or perforates a given object is quantified as well as other variables including fragment's residual velocity, % kinetic energy decrease, residual fragment mass and other exit criteria. A fragment launched under such violent conditions could easily be traveling at speeds in excess of 2500 ft/s. Given these speeds it is conceivable to imagine how any given fragment could deliver a concentrated load to a target and penetrates through walls, vehicles or even the protection systems of nearby personnel. This study will focus on the individual fragment-target impact event with the hopes of expanding it to eventually include statistical procedures. Since this is a modeling excursion into the combined frag-blast target damage effects the numerical methods used to frame this problem become important in-so-far as the simulations are done in a consistent manner. For this study a Finite-Element based Hydrocode solution called ALE3D (ALE=Arbitrary Lagrangian-Eulerian) was utilized. ALE3D is developed by Lawrence Livermore National Laboratory (Livermore, CA), and as this paper will show, successfully implemented a converged ALE formulation including as many of the different aspects needed to query the synergistic damage on a given target. Further information on the modeling setup is

  18. Differentiation of canine distemper virus isolates in fur animals from various vaccine strains by reverse transcription-polymerase chain reaction-restriction fragment length polymorphism according to phylogenetic relations in china.

    PubMed

    Wang, Fengxue; Yan, Xijun; Chai, Xiuli; Zhang, Hailing; Zhao, Jianjun; Wen, Yongjun; Wu, Wei

    2011-02-27

    In order to effectively identify the vaccine and field strains of Canine distemper virus (CDV), a new differential diagnostic test has been developed based on reverse transcription-polymerase chain reaction (RT-PCR) and restriction fragment length polymorphism (RFLP). We selected an 829 bp fragment of the nucleoprotein (N) gene of CDV. By RFLP analysis using BamHI, field isolates were distinguishable from the vaccine strains. Two fragments were obtained from the vaccine strains by RT-PCR-RFLP analysis while three were observed in the field strains. An 829 nucleotide region of the CDV N gene was analyzed in 19 CDV field strains isolated from minks, raccoon dogs and foxes in China between 2005 and 2007. The results suggest this method is precise, accurate and efficient. It was also determined that three different genotypes exist in CDV field strains in fur animal herds of the north of China, most of which belong to Asian type. Mutated field strains, JSY06-R1, JSY06-R2 and JDH07-F1 also exist in Northern China, but are most closely related to the standard virulent strain A75/17, designated in Arctic and America-2 genetype in the present study, respectively.

  19. Experimental studies of gas-aerosol reactions

    NASA Astrophysics Data System (ADS)

    Gupta, Anand

    1991-05-01

    The aqueous phase oxidation of SO2 by H2O2 is believed to the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective is to quantify the importance of the noncloud liquid phase reactions of SO2 by H2O2 in the atmosphere. Growth rates of submicron droplets exposed to SO2 and H2O2 were measured using the tandem differential mobility analyzer (TDMA) technique (Rader and McMurry, 1986). The technique uses differential mobility analyzers (DMA's) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charter capable of generating singly charged particles up to 1.0 microns was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH4)2SO4 particles with SO2 and H2O2 concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets greater than or equal to 0.3 microns, the fractional diameter growth was independent of particle size and for droplets less than or equal to 0.2 microns, it decreased as particle size decreased. The observed decrease is due to NH3 evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium, and chemical kinetics. The experimental and theoretical results are in reasonable agreement. For dry (NH4)2SO4 particles exposed to SO2, H2O2, NH3, and H2O vapor, surface reaction-controlled growth was observed. Particle growth was very sensitive to particle composition. No growth was observed for Polystyrene latex particles, whereas (NH4)2SO4 particles doped with catalysts (Fe(2+), Fe(3+), Mn(2+) and Cu(2+)) in a molar ratio of 1:500 grew slower than

  20. Experimental Studies of Gas-Aerosol Reactions

    NASA Astrophysics Data System (ADS)

    Gupta, Anand

    1991-02-01

    The aqueous phase oxidation of SO_2 by H_2O_2 is believed to be the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective of this thesis is to quantify the importance of the noncloud liquid phase reactions of SO_2 by H_2O_2 in the atmosphere. In this thesis growth rates of submicron droplets exposed to SO_2 and H_2 O_2 were measured using the tandem differential mobility analyzer (TDMA) technique (Rader and McMurry, 1986). The technique uses differential mobility analyzers (DMAs) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charger capable of generating singly charged particles up to 1.0 μm was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH_4)_2SO _4 particles with SO_2 and H_2O_2 concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets >=0.3 mum, the fractional diameter growth was independent of particle size and for droplets <=0.2 mum, it decreased as particle size decreased. The observed decrease is due to NH_3 evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium and chemical kinetics. The experimental and theoretical results are in reasonable agreement. For dry (NH_4) _2SO_4 particles exposed to SO_2, H_2O _2, NH_3 and H_2O vapor, surface reaction-controlled growth was observed. Particle growth was very sensitive to particle composition. No growth was observed for Polystyrene latex particles, whereas (NH_4) _2SO_4 particles doped with catalysts (Fe^{2+} , Fe^{3+}, Mn ^{2+}, Cu^{2+ }) in a molar ratio of 1:500 grew

  1. Production of cold target-like fragments in the reaction of /sup 48/Ca+/sup 248/Cm

    SciTech Connect

    Gaeggeler, H.; Bruechle, W.; Bruegger, M.; Schaedel, M.; Suemmerer, K.; Wirth, G.; Kratz, J.V.; Lerch, M.; Blaich, T.; Herrmann, G.

    1986-06-01

    Yields for isotopes of Rn through Pu have been measured in the reaction /sup 48/Ca+/sup 248/Cm at an energy of 248--263 MeV (1.04--1.10 times the Coulomb barrier). Despite the low bombarding energy, high and essentially constant integral yields of about 1 to 2 mb for the elements Rn through U were observed. There is evidence that these nuclides are produced with little excitation energy.

  2. Chemical redox reactions in ES-MS: Study of electrode reactions

    SciTech Connect

    Zhou, Feimeng; VAn Berkel, G.J.

    1995-12-31

    The authors previously demonstrated that chemical redox reactions can be used to ionize neutral commpounds for electrospray mass spectrometric (ES-MS) detection. Two different compounds, viz, C{sub 60}F{sub 48} and {beta}-carotene were used to demonstrate the utility of chemical redox reactions with on-line ES-MS for the elucidation of mechanisms of complicated electron transfer reactions and for the kinetic study of electrode reactions in which relatively short-lived intermediates are involved.

  3. Synthetic studies on hemicalide: development of a convergent approach toward the C1-C25 fragment.

    PubMed

    Sorin, Geoffroy; Fleury, Etienne; Tran, Christine; Prost, Elise; Molinier, Nicolas; Sautel, François; Massiot, Georges; Specklin, Simon; Meyer, Christophe; Cossy, Janine; Lannou, Marie-Isabelle; Ardisson, Janick

    2013-09-20

    Synthetic studies on hemicalide, a recently isolated marine natural product displaying highly potent antiproliferative activity and a unique mode of action, have highlighted a reliable Horner-Wadsworth-Emmons olefination to create the C6-C7 alkene and a remarkable efficient Suzuki-Miyaura coupling to form the C15-C16 bond, resulting in the development of a convergent approach toward the C1-C25 fragment.

  4. Dynamical simulation of the fission process and anisotropy of the fission fragment angular distributions of excited nuclei produced in fusion reactions

    NASA Astrophysics Data System (ADS)

    Eslamizadeh, H.

    2016-10-01

    Abstract. A stochastic approach based on four-dimensional Langevin equations was applied to calculate the anisotropy of fission fragment angular distributions, average prescission neutron multiplicity, and the fission probability in a wide range of fissile parameters for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf produced in fusion reactions. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis K were considered in the four-dimensional dynamical model. In the dynamical calculations, nuclear dissipation was generated through the chaos-weighted wall and window friction formula. Furthermore, in the dynamical calculations the dissipation coefficient of K ,γk was considered as a free parameter, and its magnitude inferred by fitting measured data on the anisotropy of fission fragment angular distributions for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf. Comparison of the calculated results for the anisotropy of fission fragment angular distributions with the experimental data showed that the results of the calculations are in good agreement with the experimental data by using values of the dissipation coefficient of K equal to (0.185-0.205), (0.175-0.192), (0.077-0.090), and (0.075-0.085) (MeVzs ) -1 /2 for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf, respectively. It was also shown that the influence of the dissipation coefficient of K on the results of the calculations of the prescission neutron multiplicity and fission probability is small.

  5. Solid-state and unilateral NMR study of deterioration of a Dead Sea Scroll fragment.

    PubMed

    Masic, A; Chierotti, M R; Gobetto, R; Martra, G; Rabin, I; Coluccia, S

    2012-02-01

    Unilateral and solid-state nuclear magnetic resonance (NMR) analyses were performed on a parchment fragment of the Dead Sea Scroll (DSS). The analyzed sample belongs to the collection of non-inscribed and nontreated fragments of known archaeological provenance from the John Rylands University Library in Manchester. Therefore, it can be considered as original DSS material free from any contamination related to the post-discovery period. Considering the paramount significance of the DSS, noninvasive approaches and portable in situ nondestructive methods are of fundamental importance for the determination of composition, structure, and chemical-physical properties of the materials under study. NMR studies reveal low amounts of water content associated with very short proton relaxation times, T(1), indicating a high level of deterioration of collagen molecules within scroll fragments. In addition, (13)C cross-polarization magic-angle-spinning (CPMAS) NMR spectroscopy shows characteristic peaks of lipids whose presence we attribute to the production technology that did not involve liming. Extraction with chloroform led to the reduction of both lipid and protein signals in the (13)C CPMAS spectrum indicating probable involvement of lipids in parchment degradation processes. NMR absorption and relaxation measurements provide nondestructive, discriminative, and sensitive tools for studying the deterioration effects on the organization and properties of water and collagen within ancient manuscripts.

  6. Effect of metal fragments in brain on electrical monitoring: In vitro and in vivo rat studies

    NASA Astrophysics Data System (ADS)

    Ahmed, A.; Bodo, M.; Armonda, R. A.

    2010-04-01

    Preliminary results showed, measurements by rheoencephalography (REG) very promising as a practical, noninvasive continuous monitoring modality of traumatic brain/blast injuries. As the impact of metal fragments on the REG signal is unknown, we report here results of our study .The in vitro study confirmed that impedance pulse amplitude waves do not change in the presence of metal (needles) placed between electrodes. In vivo studies: rats under anesthesia (10 rats, 101 trials) were measured after implantation of EEG and REG electrodes in the brain. Metal fragments were represented by 18 g needles inserted and removed between EEG and REG electrodes. Data were stored in a PC. EEG recording typically showed amplitude decrease; REG showed transitory amplitude increase after placement of a needle into either hemisphere. Removal of needles caused a decrease in REG amplitude after a transitory increase. The change in REG amplitude statistically was non-significant. Cerebral blood flow (CBF) autoregulation(AR) persisted following placement of metal fragments in rat brain.

  7. Excitation energy dependence of fragment-mass distributions from fission of 180,190Hg formed in fusion reactions of 36Ar + 144,154Sm

    DOE PAGES

    Nishio, K.; Andreyev, A. N.; Chapman, R.; ...

    2015-06-30

    Mass distributions of fission fragments from the compound nuclei 180Hg and 190 Hg formed in fusion reactions 36Ar + 144 Smand 36Ar + 154Sm, respectively, were measured at initial excitation energies of E*(180Hg) = 33-66 MeV and E*(190Hg) = 48-71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses more » $$\\overline{A}_L$$/$$\\overline{A}_H$$ = 79/101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+/EC-delayed fission of 180Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of$$\\overline{A}_L$$/$$\\overline{A}_H$$ = 83/107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. In conclusion, this behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.« less

  8. T Oligo-Primed Polymerase Chain Reaction (TOP-PCR): A Robust Method for the Amplification of Minute DNA Fragments in Body Fluids

    PubMed Central

    Nai, Yu-Shin; Chen, Tzu-Han; Huang, Yu-Feng; Midha, Mohit K.; Shiau, Hsin-Chieh; Shen, Chen-Yang; Chen, Chien-Jen; Yu, Alice L.; Chiu, Kuo Ping

    2017-01-01

    Body fluid DNA sequencing is a powerful noninvasive approach for the diagnosis of genetic defects, infectious agents and diseases. The success relies on the quantity and quality of the DNA samples. However, numerous clinical samples are either at low quantity or of poor quality due to various reasons. To overcome these problems, we have developed T oligo-primed polymerase chain reaction (TOP-PCR) for full-length nonselective amplification of minute quantity of DNA fragments. TOP-PCR adopts homogeneous “half adaptor” (HA), generated by annealing P oligo (carrying a phosphate group at the 5′ end) and T oligo (carrying a T-tail at the 3′ end), for efficient ligation to target DNA and subsequent PCR amplification primed by the T oligo alone. Using DNA samples from body fluids, we demonstrate that TOP-PCR recovers minute DNA fragments and maintains the DNA size profile, while enhancing the major molecular populations. Our results also showed that TOP-PCR is a superior method for detecting apoptosis and outperforms the method adopted by Illumina for DNA amplification. PMID:28094343

  9. T Oligo-Primed Polymerase Chain Reaction (TOP-PCR): A Robust Method for the Amplification of Minute DNA Fragments in Body Fluids.

    PubMed

    Nai, Yu-Shin; Chen, Tzu-Han; Huang, Yu-Feng; Midha, Mohit K; Shiau, Hsin-Chieh; Shen, Chen-Yang; Chen, Chien-Jen; Yu, Alice L; Chiu, Kuo Ping

    2017-01-17

    Body fluid DNA sequencing is a powerful noninvasive approach for the diagnosis of genetic defects, infectious agents and diseases. The success relies on the quantity and quality of the DNA samples. However, numerous clinical samples are either at low quantity or of poor quality due to various reasons. To overcome these problems, we have developed T oligo-primed polymerase chain reaction (TOP-PCR) for full-length nonselective amplification of minute quantity of DNA fragments. TOP-PCR adopts homogeneous "half adaptor" (HA), generated by annealing P oligo (carrying a phosphate group at the 5' end) and T oligo (carrying a T-tail at the 3' end), for efficient ligation to target DNA and subsequent PCR amplification primed by the T oligo alone. Using DNA samples from body fluids, we demonstrate that TOP-PCR recovers minute DNA fragments and maintains the DNA size profile, while enhancing the major molecular populations. Our results also showed that TOP-PCR is a superior method for detecting apoptosis and outperforms the method adopted by Illumina for DNA amplification.

  10. True ternary fission, the collinear decay into fragments of similar size in the 252Cf(sf) and 235U(nth, f) reactions

    NASA Astrophysics Data System (ADS)

    von Oertzen, W.; Nasirov, A. K.

    2014-06-01

    The collinear cluster decay in 252Cf(sf, fff), with three cluster fragments of different masses (e.g. 132Sn, 52-48Ca, 68-72Ni), which has been observed by the FOBOS group in JINR, has established a new decay mode of heavy nuclei, the collinear cluster tripartition (CCT). The same type of ternary fission decay has been observed in the reaction 235U(nth, fff). This kind of “true ternary fission” of heavy nuclei has been predicted many times in theoretical works during the last decades. In the present note we discuss true ternary fission (TFFF) into three nuclei of almost equal size (e.g. Z=98→Zi=32, 34, 32) in the same systems. The possible fission channels are predicted from potential-energy (PES) calculations. These PES's show pronounced minima for several ternary fragmentation decays, e.g. for 252Cf(sf) and for 235U(nth, f). They suggest the existence of a variety of collinear ternary fission modes. The TFFF-decays chosen in this letter have very similar dynamical features as the previously observed collinear CCT-decays. The data obtained in the above mentioned experiments allow us to extract the yield for these TFFF-decays in both systems by using specific gates on the measured parameters. These yields are a few 1.0ṡ10-6/(binary fission).

  11. Molecular characterization of Streptococcus suis strains by 16S–23S intergenic spacer polymerase chain reaction and restriction fragment length polymorphism analysis

    PubMed Central

    Le Devendec, Laëtitia; Gottschalk, Marcelo; Kobisch, Marylène

    2006-01-01

    Abstract We developed a new molecular method of typing Streptococcus suis based on polymerase chain reaction (PCR) amplification of a large fragment of rRNA genes, including a part of the 16S and 23S genes and the 16S–23S intergenic spacer region (ISR), followed by restriction fragment length polymorphism (RFLP) analysis with RsaI or MboII endonuclease. The 16S–23S ISRs of 5 S. suis isolates were sequenced and compared. Size and sequence polymorphisms were observed between the S735 reference strain and the 4 wild-type strains. The genetic relationships between 138 independent S. suis strains belonging to various serotypes, isolated from swine or human cases, were determined. The discriminatory power of the method was > 0.95, the threshold value for interpreting typing results with confidence (0.954 with RsaI and 0.984 with RsaI plus MboII). The in vitro reproducibility was 100%. The strains isolated from humans were less genetically diverse than the strains isolated from pigs. For the first time, 2 molecular patterns (R6, M9) were significantly associated with S. suis serotype 2 strains. This genetic tool could be valuable in distinguishing individual isolates of S. suis during epidemiologic investigations. PMID:16639941

  12. Excitation energy dependence of fragment-mass distributions from fission of 180,190Hg formed in fusion reactions of 36Ar + 144,154Sm

    NASA Astrophysics Data System (ADS)

    Nishio, K.; Andreyev, A. N.; Chapman, R.; Derkx, X.; Düllmann, Ch. E.; Ghys, L.; Heßberger, F. P.; Hirose, K.; Ikezoe, H.; Khuyagbaatar, J.; Kindler, B.; Lommel, B.; Makii, H.; Nishinaka, I.; Ohtsuki, T.; Pain, S. D.; Sagaidak, R.; Tsekhanovich, I.; Venhart, M.; Wakabayashi, Y.; Yan, S.

    2015-09-01

    Mass distributions of fission fragments from the compound nuclei 180Hg and 190Hg formed in fusion reactions 36Ar + 144Sm and 36Ar + 154Sm, respectively, were measured at initial excitation energies of E* (180Hg) = 33- 66 MeV and E* (190Hg) = 48- 71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses AbarL /AbarH = 79 / 101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+ / EC -delayed fission of 180Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of AbarL /AbarH = 83 / 107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. This behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.

  13. Asymmetry effects in fragment production

    NASA Astrophysics Data System (ADS)

    Kaur, Manpreet; Kaur, Varinderjit

    2016-05-01

    The production of different fragments has been studied by taking into account the mass asymmetry of the reaction and employing the momentum dependent interactions. Two different set of asymmetric reactions have been analyzed while keeping Atotal fixed using soft momentum dependent equation of state. Our results indicate that the impact of momentum dependent interactions is different in lighter projectile systems as compared to heavier ones. The comparative analysis of IQMD simulations with the experimental data in case of heavier projectile and lighter target system for the reaction of 197Au+27Al (η = 0.7) at E = 600 MeV/nucleon shows that with the inclusion of MDI we are able, upto some extent, to reproduce the experimental universality of rise and fall of intermediate mass fragments (IMFs).

  14. Amplified fragment length polymorphism: an invaluable fingerprinting technique for genomic, transcriptomic, and epigenetic studies.

    PubMed

    Paun, Ovidiu; Schönswetter, Peter

    2012-01-01

    Amplified fragment length polymorphism (AFLP) is a PCR-based technique that uses selective amplification of a subset of digested DNA fragments to generate and compare unique fingerprints for genomes of interest. The power of this method relies mainly in that it does not require prior information regarding the targeted genome, as well as in its high reproducibility and sensitivity for detecting polymorphism at the level of DNA sequence. Widely used for plant and microbial studies, AFLP is employed for a variety of applications, such as to assess genetic diversity within species or among closely related species, to infer population-level phylogenies and biogeographic patterns, to generate genetic maps, and to determine relatedness among cultivars. Variations of standard AFLP methodology have been also developed for targeting additional levels of diversity, such as transcriptomic variation and DNA methylation polymorphism.

  15. Study of the fragmentation of /b quarks into /B mesons at the /Z peak

    NASA Astrophysics Data System (ADS)

    ALEPH Collaboration; Heister, A.; Schael, S.; Barate, R.; De Bonis, I.; Decamp, D.; Goy, C.; Lees, J.-P.; Merle, E.; Minard, M.-N.; Pietrzyk, B.; Bravo, S.; Casado, M. P.; Chmeissani, M.; Crespo, J. M.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, L.; Graugés, E.; Martinez, M.; Merino, G.; Miquel, R.; Mir, L. M.; Pacheco, A.; Ruiz, H.; Colaleo, A.; Creanza, D.; de Palma, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Nuzzo, S.; Ranieri, A.; Raso, G.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Tricomi, A.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Abbaneo, D.; Azzurri, P.; Boix, G.; Buchmüller, O.; Cattaneo, M.; Cerutti, F.; Clerbaux, B.; Dissertori, G.; Drevermann, H.; Forty, R. W.; Frank, M.; Greening, T. C.; Hansen, J. B.; Harvey, J.; Janot, P.; Jost, B.; Kado, M.; Mato, P.; Moutoussi, A.; Ranjard, F.; Rolandi, L.; Schlatter, D.; Schneider, O.; Spagnolo, P.; Tejessy, W.; Teubert, F.; Tournefier, E.; Ward, J.; Ajaltouni, Z.; Badaud, F.; Falvard, A.; Gay, P.; Henrard, P.; Jousset, J.; Michel, B.; Monteil, S.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Nilsson, B. S.; Wäänänen, A.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Bonneaud, G.; Brient, J.-C.; Rougé, A.; Rumpf, M.; Swynghedauw, M.; Verderi, M.; Videau, H.; Ciulli, V.; Focardi, E.; Parrini, G.; Antonelli, A.; Antonelli, M.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Chiarella, V.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Halley, A. W.; Lynch, J. G.; Negus, P.; O'Shea, V.; Raine, C.; Thompson, A. S.; Wasserbaech, S.; Cavanaugh, R.; Dhamotharan, S.; Geweniger, C.; Hanke, P.; Hansper, G.; Hepp, V.; Kluge, E. E.; Putzer, A.; Sommer, J.; Tittel, K.; Werner, S.; Wunsch, M.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Dornan, P. J.; Girone, M.; Marinelli, N.; Sedgbeer, J. K.; Thompson, J. C.; Ghete, V. M.; Girtler, P.; Kneringer, E.; Kuhn, D.; Rudolph, G.; Bouhova-Thacker, E.; Bowdery, C. K.; Finch, A. J.; Foster, F.; Hughes, G.; Jones, R. W. L.; Pearson, M. R.; Robertson, N. A.; Giehl, I.; Jakobs, K.; Kleinknecht, K.; Quast, G.; Renk, B.; Rohne, E.; Sander, H.-G.; Wachsmuth, H.; Zeitnitz, C.; Bonissent, A.; Carr, J.; Coyle, P.; Leroy, O.; Payre, P.; Rousseau, D.; Talby, M.; Aleppo, M.; Ragusa, F.; David, A.; Dietl, H.; Ganis, G.; Hüttmann, K.; Lütjens, G.; Mannert, C.; Männer, W.; Moser, H.-G.; Settles, R.; Stenzel, H.; Wiedenmann, W.; Wolf, G.; Boucrot, J.; Callot, O.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, P.; Jacholkowska, A.; Lefrançois, J.; Veillet, J.-J.; Videau, I.; Yuan, C.; Bagliesi, G.; Boccali, T.; Calderini, G.; Foà, L.; Giammanco, A.; Giassi, A.; Ligabue, F.; Messineo, A.; Palla, F.; Sanguinetti, G.; Sciabà, A.; Sguazzoni, G.; Tenchini, R.; Venturi, A.; Verdini, P. G.; Blair, G. A.; Cowan, G.; Green, M. G.; Medcalf, T.; Misiejuk, A.; Strong, J. A.; Teixeira-Dias, P.; von Wimmersperg-Toeller, J. H.; Clifft, R. W.; Edgecock, T. R.; Norton, P. R.; Tomalin, I. R.; Bloch-Devaux, B.; Colas, P.; Emery, S.; Kozanecki, W.; Lançon, E.; Lemaire, M.-C.; Locci, E.; Perez, P.; Rander, J.; Renardy, J.-F.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Trabelsi, A.; Vallage, B.; Konstantinidis, N.; Litke, A. M.; Taylor, G.; Booth, C. N.; Cartwright, S.; Combley, F.; Lehto, M.; Thompson, L. F.; Affholderbach, K.; Böhrer, A.; Brandt, S.; Grupen, C.; Ngac, A.; Prange, G.; Sieler, U.; Giannini, G.; Rothberg, J.; Armstrong, S. R.; Cranmer, K.; Elmer, P.; Ferguson, D. P. S.; Gao, Y.; González, S.; Hayes, O. J.; Hu, H.; Jin, S.; Kile, J.; McNamara, P. A.; Nielsen, J.; Orejudos, W.; Pan, Y. B.; Saadi, Y.; Scott, I. J.; Walsh, J.; Wu, S. L.; Wu, X.; Zobernig, G.

    2001-07-01

    The fragmentation of /b quarks into /B mesons is studied with four million hadronic /Z decays collected by the ALEPH experiment during the years 1991-1995. A semi-exclusive reconstruction of B-->lνD(*) decays is performed, by combining lepton candidates with fully reconstructed D(*) mesons while the neutrino energy is estimated from the missing energy of the event. The mean value of xBwd, the energy of the weakly-decaying /B meson normalised to the beam energy, is found to be =0.716+/-0.006(stat)+/-0.006(syst), using a model-independent method; the corresponding value for the energy of the leading /B meson is =0.736+/-0.006(stat)+/-0.006(syst). The reconstructed spectra are compared with different fragmentation models.

  16. The N-terminal fragment of the tomato torrado virus RNA1-encoded polyprotein induces a hypersensitive response (HR)-like reaction in Nicotiana benthamiana.

    PubMed

    Wieczorek, Przemysław; Obrępalska-Stęplowska, Aleksandra

    2016-07-01

    The hypersensitive response (HR) is a defence reaction observed during incompatible plant-pathogen interactions in plants infected with a wide range of fungi, bacteria and viruses. Here, we show that an N-terminal polyprotein fragment encoded by tomato torrado virus RNA1, located between the first ATG codon and the protease cofactor (ProCo) motif, induces an HR-like reaction in Nicotiana benthamiana. Agrobacterium tumefaciens-mediated transient expression of the first 105 amino acids (the calculated molecular weight of the fragment was ca. 11.33 kDa, hereafter refered to as the 11K domain) from ToTV RNA1 induced an HR-like phenotype in infiltrated leaves. To investigate whether the 11K domain could influence the virulence and pathogenicity of a recombinant virus, we created a potato virus X (PVX) with the 11K coding sequence inserted under a duplicated coat protein promoter. We found that 11K substantially increased the virulence of the recombinant virus. Disease phenotype induced in N. benthamiana by PVX-11K was characterized by strong local and systemic necrosis. This was not observed when the 11K domain was expressed from PVX in an antisense orientation. Further analyses revealed that the 11K domain could not suppress posttranscriptional gene silencing (PTGS) of green fluorescent protein (GFP) in the N. benthamiana 16c line. In silico analysis of the predicted secondary structure of the 11K domain indicated the presence of two putative helices that are highly conserved in tomato-infecting representatives of the genus Torradovirus.

  17. A recoil ion momentum spectrometer for molecular and atomic fragmentation studies

    NASA Astrophysics Data System (ADS)

    Khan, Arnab; Tribedi, Lokesh C.; Misra, Deepankar

    2015-04-01

    We report the development and performance studies of a newly built recoil ion momentum spectrometer for the study of atomic and molecular fragmentation dynamics in gas phase upon the impact of charged particles and photons. The present design is a two-stage Wiley-McLaren type spectrometer which satisfies both time and velocity focusing conditions and is capable of measuring singly charged ionic fragments up-to 13 eV in all directions. An electrostatic lens has been introduced in order to achieve velocity imaging. Effects of the lens on time-of-flight as well as on the position have been investigated in detail, both, by simulation and in experiment. We have used 120 keV proton beam on molecular nitrogen gas target. Complete momentum distributions and kinetic energy release distributions have been derived from the measured position and time-of-flight spectra. Along with this, the kinetic energy release spectra of fragmentation of doubly ionized nitrogen molecule upon various projectile impacts are presented.

  18. VUV Photo-processing of PAH Cations: Quantitative Study on the Ionization versus Fragmentation Processes

    NASA Astrophysics Data System (ADS)

    Zhen, Junfeng; Rodriguez Castillo, Sarah; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M.

    2016-05-01

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7-20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ˜13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies all species behave similarly; the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ˜18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them; all are in good agreement with theoretical ones, confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.

  19. VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes

    PubMed Central

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M.

    2016-01-01

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7 – 20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models. PMID:27212712

  20. VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes.

    PubMed

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M

    2016-05-10

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7 - 20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.

  1. A fragmentation study of kaempferol using electrospray quadrupole time-of-flight mass spectrometry at high mass resolution

    NASA Astrophysics Data System (ADS)

    March, Raymond E.; Miao, Xiu-Sheng

    2004-02-01

    A mass spectrometric method based on the combined use of electrospray ionization, collision-induced dissociation and tandem mass spectrometry at high mass resolution has been applied to an investigation of the structural characterization of protonated and deprotonated kaempferol (3,5,7,4'-tetrahydroxyflavone). Low-energy product ion mass spectra of [M+H]+ ions showed simple fragmentations of the C ring that permitted characterization of the substituents in the A and B rings. In addition, four rearrangement reactions accompanied by losses of C2H2O, CHO[radical sign], CO, and H2O were observed. Low-energy product ion mass spectra of [M-H]- ions showed only four rearrangement reactions accompanied by losses of OH[radical sign], CO, CH2O, and C2H2O. The use of elevated cone voltages permitted observation of product ion mass spectra of selected primary and secondary fragment ions so that each fragment ion reported was observed as a direct product of its immediate precursor ion. Product ion mass spectra examined at high mass resolution allowed unambiguous determination of the elemental composition of fragment ions and resolution of two pairs of isobars. Fragmentation mechanisms and ion structures have been proposed.

  2. Imidate-Based Cross-Linkers for Structural Proteomics: Increased Charge of Protein and Peptide Ions and CID and ECD Fragmentation Studies

    NASA Astrophysics Data System (ADS)

    Koolen, Hector H. F.; Gomes, Alexandre F.; Schwab, Nicolas V.; Eberlin, Marcos N.; Gozzo, Fabio C.

    2014-07-01

    Chemical cross-linking is an attractive low-resolution technique for structural studies of protein complexes. Distance constraints obtained from cross-linked peptides identified by mass spectrometry (MS) are used to construct and validate protein models. Amidinating cross-linkers such as diethyl suberthioimidate (DEST) have been used successfully in chemical cross-linking experiments. In this work, the application of a commercial diimidate cross-linking reagent, dimethyl suberimidate (DMS), was evaluated with model peptides and proteins. The peptides were designed with acetylated N-termini followed by random sequences containing two Lys residues separated by an Arg residue. After cross-linking reactions, intra- and intermolecular cross-linked species were submitted to CID and ECD dissociations to study their fragmentation features in the gas phase. Fragmentation of intramolecular peptides by collision induced dissociation (CID) demonstrates a unique two-step fragmentation pathway involving formation of a ketimine as intermediate. Electron capture and electron transfer dissociation (ECD and ETD) experiments demonstrated that the cyclic moiety is not dissociated. Intermolecular species demonstrated previously described fragmentation behavior in both CID and ECD experiments. The charge state distributions (CSD) obtained after reaction with DMS were compared with those obtained with disuccinimidyl suberate (DSS). CSDs for peptides and proteins were increased after their reaction with DMS, owing to the higher basicity of DMS modified species. These features were also observed in LC-MS experiments with bovine carbonic anhydrase II (BCA) after cross-linking with DMS and tryptic proteolysis. Cross-linked peptides derived from this protein were identified at high confidence and those species were in agreement with the crystal structure of BCA.

  3. Experimental and numerical study of thin fragments protection for radiographic detectors

    NASA Astrophysics Data System (ADS)

    Bozier, Olivier; Counilh, Denis; Gillot, Fabrice; Adolf, Lise-Marie; Silvin, Pascale; Rambert, Nicolas; Hebert, David; Bertron, Isabelle

    2015-06-01

    To perform a non-intrusive measurement on a pyrotechnic setup, we usually use radiography. But due to blast and fragments, the X-ray generator head and the detectors of the radiographic chain must be protected. Since the detector holds the data we want to collect, he cannot be sacrificed. The constitution of detector shielding is therefore an essential part of a radiographic chain. The choice of shielding should take into account two conflicting needs. On one hand, shielding must be sufficiently resistant to protect the detector from the blast and fragments generated. On the other hand, it should be thin enough in order to attenuate as little as possible the radiographic signal. We carried out an experimental campaign to test the performances of various shieldings. Cylindrical projectiles of various masses (from 20g to 40g) and aspect ratios (length to diameter ratio from 0.1 to 1) that are representative fragments, have been launched with a gas gun with different initial velocities (from 1500m/s up to 2000m/s). Multiple shielding configurations have been tested. They were assemblies of successive steel, aluminum and B4C plates. Combined with a numerical study, we optimize disposition and thicknesses of the plates which fulfils our requirements in terms of detector protection and radiographic measurement.

  4. A statistical study of meteoroid fragmentation and differential ablation using the Resolute Bay Incoherent Scatter Radar

    NASA Astrophysics Data System (ADS)

    Malhotra, Akshay; Mathews, John D.

    2011-04-01

    There has been much interest in the meteor physics community recently regarding the detailed processes by which the meteoroid mass flux arrives in the upper atmosphere. Of particular interest are the relative roles of simple ablation, differential ablation, and fragmentation in interpretation of the meteor events observed by the high-power large-aperture (HPLA) radars. An understanding of the relative roles of these mechanisms is necessary to determine whether the considerable meteor mass flux arriving in the upper atmosphere arrives mostly in nanometer dust/smoke (via fragmentation) or atomic form (via ablation), which in turn has important consequences in understanding not only the aeronomy of the region but also the formation and evolution of various upper atmospheric phenomenon such as Polar Mesospheric Summer Echoes. Using meteor observations from the newly operational Resolute Bay Incoherent Scatter Radar (RISR), we present the first statistical study showing the relative contribution of these mechanisms. We find that RISR head echoes exhibited ˜48% fragmentation, ˜32% simple ablation, and ˜20% differential ablation. We also report existence of compound meteor events exhibiting signatures of more than one mass loss mechanism. These results emphasize that the processes by which the meteoroid mass is deposited into the upper atmosphere are complex and involve all three mechanisms described here. This conclusion is unlike the previously reported results that stress the importance of one or the other of these mechanisms. These results will also contribute in improving current meteoroid disintegration/ablation models.

  5. Fragmentation and conformation study of ephedrine by low- and high-resolution mass selective UV spectroscopy

    NASA Astrophysics Data System (ADS)

    Chervenkov, S.; Wang, P. Q.; Braun, J. E.; Neusser, H. J.

    2004-10-01

    The neurotransmitter molecule, ephedrine, has been studied by mass-selective low- and high-resolution UV resonance enhanced two-photon ionization spectroscopy. Under all experimental conditions we observed an efficient fragmentation upon ionization. The detected vibronic peaks in the spectrum are classified according to the efficiency of the fragmentation, which leads to the conclusion that there exist three different species in the molecular beam: ephedrine-water cluster and two distinct conformers. The two-color two-photon ionization experiment with a decreased energy of the second photon leads to an upper limit of 8.3 eV for the ionization energy of ephedrine. The high-resolution (70 MHz) spectrum of the strongest vibronic peak in the spectrum measured at the fragment (m/z=58) mass channel displays a pronounced and rich rotational structure. Its analysis by the use of a specially designed computer-aided rotational fit process yields accurate rotational constants for the S0 and S1 states and the transition moment ratio, providing information on the respective conformational structure.

  6. Fragmentation of mercury compounds under ultraviolet light irradiation

    NASA Astrophysics Data System (ADS)

    Kokkonen, E.; Löytynoja, T.; Hautala, L.; Jänkälä, K.; Huttula, M.

    2015-08-01

    Ultraviolet light induced photofragmentation of mercury compounds is studied experimentally with electron energy resolved photoelectron-photoion coincidence techniques and theoretically with computational quantum chemical methods. A high resolution photoelectron spectrum using synchrotron radiation is presented. Fragmentation of the molecule is studied subsequent to ionization to the atomic-mercury-like d orbitals. State dependent fragmentation behaviour is presented and specific reactions for dissociation pathways are given. The fragmentation is found to differ distinctly in similar orbitals of different mercury compounds.

  7. Fragmentation of mercury compounds under ultraviolet light irradiation

    SciTech Connect

    Kokkonen, E.; Hautala, L.; Jänkälä, K.; Huttula, M.; Löytynoja, T.

    2015-08-21

    Ultraviolet light induced photofragmentation of mercury compounds is studied experimentally with electron energy resolved photoelectron-photoion coincidence techniques and theoretically with computational quantum chemical methods. A high resolution photoelectron spectrum using synchrotron radiation is presented. Fragmentation of the molecule is studied subsequent to ionization to the atomic-mercury-like d orbitals. State dependent fragmentation behaviour is presented and specific reactions for dissociation pathways are given. The fragmentation is found to differ distinctly in similar orbitals of different mercury compounds.

  8. Construction of a 3D-shaped, natural product like fragment library by fragmentation and diversification of natural products.

    PubMed

    Prescher, Horst; Koch, Guido; Schuhmann, Tim; Ertl, Peter; Bussenault, Alex; Glick, Meir; Dix, Ina; Petersen, Frank; Lizos, Dimitrios E

    2017-02-01

    A fragment library consisting of 3D-shaped, natural product-like fragments was assembled. Library construction was mainly performed by natural product degradation and natural product diversification reactions and was complemented by the identification of 3D-shaped, natural product like fragments available from commercial sources. In addition, during the course of these studies, novel rearrangements were discovered for Massarigenin C and Cytochalasin E. The obtained fragment library has an excellent 3D-shape and natural product likeness, covering a novel, unexplored and underrepresented chemical space in fragment based drug discovery (FBDD).

  9. Study of char gasification in a reaction/adsorption apparatus

    SciTech Connect

    Sotirchos, S.V.; Crowley, J.A.

    1987-09-01

    The reaction of an activated carbon (coconut char) with CO/sub 2/ was studied in a reaction/adsorption apparatus which allows successive reactivity and physical adsorption measurements to be made on the same solid sample. Reaction and surface area evolution data were obtained in the temperature range from 800 to 900/sup 0/C. All reaction rate trajectories obtained in this study showed a maximum in the reaction rate, 2-3 times higher than the initial rate, at about 85% conversion. There was no correlation between these results and the evolution of the internal surface area although the reaction appeared to take place initially in the kinetically controlled regime.

  10. Development of a polymerase chain reaction-restriction fragment length polymorphism method for identification of the Fusarium genus using the transcription elongation factor-1α gene.

    PubMed

    Zarrin, Majid; Ganj, Farzaneh; Faramarzi, Sama

    2016-12-01

    Fusarium species are well-known plant pathogens and food contaminants that have also appeared as one of the most important groups of medically significant fungi. The sequences of the translation elongation factor (TEF)-1α gene have been broadly employed for species detection. A total of 50 strains of Fusarium spp., including environmental, clinical and reference isolates were used for the current study. The primer sets, Fu3f and Fu3r, were used to amplify an ~420-bp DNA fragment of the TEF-1α gene. Double digestion with two restriction enzymes, XhoI and SduI was used for discrimination of the Fusarium species in the TEF-1α gene fragment. Double digestion of the TEF-1α gene fragment from five clinically important Fusarium species were clearly differentiated from each other: The F. solani species complex, F. oxysporum species complex, F. verticillioides, F. proliferatum and F. fujikuroi. This method facilitates detection and enables verification of the Fusarium genus; therefore, it may be applied for disease control.

  11. Development of a polymerase chain reaction-restriction fragment length polymorphism method for identification of the Fusarium genus using the transcription elongation factor-1α gene

    PubMed Central

    Zarrin, Majid; Ganj, Farzaneh; Faramarzi, Sama

    2016-01-01

    Fusarium species are well-known plant pathogens and food contaminants that have also appeared as one of the most important groups of medically significant fungi. The sequences of the translation elongation factor (TEF)-1α gene have been broadly employed for species detection. A total of 50 strains of Fusarium spp., including environmental, clinical and reference isolates were used for the current study. The primer sets, Fu3f and Fu3r, were used to amplify an ~420-bp DNA fragment of the TEF-1α gene. Double digestion with two restriction enzymes, XhoI and SduI was used for discrimination of the Fusarium species in the TEF-1α gene fragment. Double digestion of the TEF-1α gene fragment from five clinically important Fusarium species were clearly differentiated from each other: The F. solani species complex, F. oxysporum species complex, F. verticillioides, F. proliferatum and F. fujikuroi. This method facilitates detection and enables verification of the Fusarium genus; therefore, it may be applied for disease control. PMID:28105337

  12. Experimental verification of proton beam monitoring in a human body by use of activity image of positron-emitting nuclei generated by nuclear fragmentation reaction.

    PubMed

    Nishio, Teiji; Miyatake, Aya; Inoue, Kazumasa; Gomi-Miyagishi, Tomoko; Kohno, Ryosuke; Kameoka, Satoru; Nakagawa, Keiichi; Ogino, Takashi

    2008-01-01

    Proton therapy is a form of radiotherapy that enables concentration of dose on a tumor by use of a scanned or modulated Bragg peak. Therefore, it is very important to evaluate the proton-irradiated volume accurately. The proton-irradiated volume can be confirmed by detection of pair-annihilation gamma rays from positron-emitting nuclei generated by the nuclear fragmentation reaction of the incident protons on target nuclei using a PET apparatus. The activity of the positron-emitting nuclei generated in a patient was measured with a PET-CT apparatus after proton beam irradiation of the patient. Activity measurement was performed in patients with tumors of the brain, head and neck, liver, lungs, and sacrum. The 3-D PET image obtained on the CT image showed the visual correspondence with the irradiation area of the proton beam. Moreover, it was confirmed that there were differences in the strength of activity from the PET-CT images obtained at each irradiation site. The values of activity obtained from both measurement and calculation based on the reaction cross section were compared, and it was confirmed that the intensity and the distribution of the activity changed with the start time of the PET imaging after proton beam irradiation. The clinical use of this information about the positron-emitting nuclei will be important for promoting proton treatment with higher accuracy in the future.

  13. Fragmentation Processes

    NASA Astrophysics Data System (ADS)

    Whelan, Colm T.

    2012-12-01

    Preface; 1. Direct and resonant double-photoionization: from atoms to solids L. Avaldi and G. Stefani; 2. The application of propagation exterior complex scaling to atomic collisions P. L. Bartlett and A. T. Stelbovics; 3. Fragmentation of molecular-ion beams in intense ultra-short laser pulses I. Ben-Itzhak; 4. Atoms with one and two active electrons in strong laser fields I. A. Ivanov and A. S. Kheifets; 5. Experimental aspects of ionization studies by positron and positronium impact G. Laricchia, D. A. Cooke, Á. Kövér and S. J. Brawley; 6. (e,2e) spectroscopy using fragmentation processes J. Lower, M. Yamazaki and M. Takahashi; 7. A coupled pseudostate approach to the calculation of ion-atom fragmentation processes M. McGovern, H. R. J. Walters and C. T. Whelan; 8. Electron Impact Ionization using (e,2e) coincidence techniques from threshold to intermediate energies A. J. Murray; 9. (e,2e) processes on atomic inner shells C. T. Whelan; 10. Spin resolved atomic (e,2e) processes J. Lower and C. T. Whelan; Index.

  14. Density functional study of chemical reaction equilibrium for dimerization reactions in slit and cylindrical nanopores

    NASA Astrophysics Data System (ADS)

    Malijevský, Alexandr; Lísal, Martin

    2009-04-01

    We present a theoretical study of the effects of confinement on chemical reaction equilibrium in slit and cylindrical nanopores. We use a density functional theory (DFT) to investigate the effects of temperature, pore geometry, bulk pressure, transition layering, and capillary condensation on a dimerization reaction that mimics the nitric oxide dimerization reaction, 2NO⇌(NO)2, in carbonlike slit and cylindrical nanopores in equilibrium with a vapor reservoir. In addition to the DFT calculations, we also utilize the reaction ensemble Monte Carlo method to supplement the DFT results for reaction conversion. This work is an extension of the previous DFT study by Tripathi and Chapman [J. Chem. Phys. 118, 7993 (2003)] on the dimerization reactions confined in the planar slits.

  15. Raman spectroscopic study of reaction dynamics

    NASA Astrophysics Data System (ADS)

    MacPhail, R. A.

    1990-12-01

    The Raman spectra of reacting molecules in liquids can yield information about various aspects of the reaction dynamics. The author discusses the analysis of Raman spectra for three prototypical unimolecular reactions, the rotational isomerization of n-butane and 1,2-difluoroethane, and the barrierless exchange of axial and equatorial hydrogens in cyclopentane via pseudorotation. In the first two cases the spectra are sensitive to torsional oscillations of the gauche conformer, and yield estimates of the torsional solvent friction. In the case of cyclopentane, the spectra can be used to discriminate between different stochastic models of the pseudorotation dynamics, and to determine the relevant friction coefficients.

  16. Soot Reaction Properties (Ground-Based Study)

    NASA Technical Reports Server (NTRS)

    Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2000-01-01

    Three major soot reaction processes are needed to predict soot properties in flame environments: soot growth, or the formation of soot on soot nuclei and soot particles; soot oxidation, or the reaction of soot with oxidizing species to yield the combustion products of soot oxidation; and soot nucleation, or the formation of soot nuclei from soot precursors having large molecular weights (generally thought to be large and particularly stable PAH molecules in flame environments, called stabilomers). These processes are addressed in the following, considering soot growth, oxidation and nucleation, in turn, by exploiting the soot and flame structure results for premixed and diffusion flames already discussed in Section 2.

  17. Laser studies of chemical reaction and collision processes

    SciTech Connect

    Flynn, G.

    1993-12-01

    This work has concentrated on several interrelated projects in the area of laser photochemistry and photophysics which impinge on a variety of questions in combustion chemistry and general chemical kinetics. Infrared diode laser probes of the quenching of molecules with {open_quotes}chemically significant{close_quotes} amounts of energy in which the energy transferred to the quencher has, for the first time, been separated into its vibrational, rotational, and translational components. Probes of quantum state distributions and velocity profiles for atomic fragments produced in photodissociation reactions have been explored for iodine chloride.

  18. Physical and dynamical studies of meteors. Meteor-fragmentation and stream-distribution studies

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.; Southworth, R. B.

    1975-01-01

    Population parameters of 275 streams including 20 additional streams in the synoptic-year sample were found by a computer technique. Some 16 percent of the sample is in these streams. Four meteor streams that have close orbital resemblance to Adonis cannot be positively identified as meteors ejected by Adonis within the last 12000 years. Ceplecha's discrete levels of meteor height are not evident in radar meteors. The spread of meteoroid fragments along their common trajectory was computed for most of the observed radar meteors. There is an unexpected relationship between spread and velocity that perhaps conceals relationships between fragmentation and orbits; a theoretical treatment will be necessary to resolve these relationships. Revised unbiased statistics of synoptic-year orbits are presented, together with parallel statistics for the 1961 to 1965 radar meteor orbits.

  19. Kinetic Study of the Heck Reaction: An Interdisciplinary Experiment

    ERIC Educational Resources Information Center

    Gozzi, Christel; Bouzidi, Naoual

    2008-01-01

    The aim of this experiment is to study and calculate the kinetic constant of a Heck reaction: the arylation of but-3-en-2-ol by iodobenzene catalyzed by palladium acetate in presence of triethylamine in DMF. The reaction leads to a mixture of two ketones. Students use GC analysis to quantify reagents and products of reaction. They control the…

  20. Study of Reaction Mechanism in Tracer Munitions

    DTIC Science & Technology

    1974-12-01

    Regression Rates (Furnished by Frankford Arsenal) 35 13 Calculated Heat Fluxes and Energy Partitions 43 4 I NOMENCLATURE B = preexponential factor... anhydride disproportionates in a fast step: N2 0 3 - 2 + NO (4) so that the resulting dioxide can react with more nitrite in another fast reaction: Sr

  1. Antibody fragment recognition layers for surface plasmon resonance biosensing: a parametric study

    NASA Astrophysics Data System (ADS)

    Magalhães, André; Bordeira, Sandro; Almeida, Ana Cristina; Fontes, Vanessa; Costa, Maria João L.; Fonseca, Luís P.; da Fonseca, João Garcia

    2009-02-01

    A comparative study is reported regarding the use of two different surface plasmon resonance (SPR) biosensors, a homemade SPR grating biosensor and a reference prism coupled biosensor, to perform quantification of C-reactive protein (CRP) in human blood serum. Surface functionalization was conducted using anti-CRP fragments immobilized directly on gold. Adsorption time optimization for the antibody fragments monolayer, non-specific binding (NSB) resistance evaluation and CRP detection were conducted, with better results achieved by the grating biosensor on all topics, namely less functionalization time, higher resistance to NSB and wider CRP dynamic concentration range. A study regarding comparison between continuous flow and surface coating immobilization is also reported in this work. We have shown that surface coating immobilization achieves similar NSB resistance and CRP detection results, allowing a 75% assay cost reduction by lower solution volume requirement. Results suggest that the coating immobilization technique is the best suited to be used in further studies in order to obtain a viable immunosensor for CRP and other biomarkers detection in complex biological fluids.

  2. Development of a Multiplexed Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) Assay to Identify Common Members of the Subgenera Culex (Culex) and Culex (Phenacomyia) in Guatemala

    PubMed Central

    Kent, Rebekah J.; Deus, Stephen; Williams, Martin; Savage, Harry M.

    2010-01-01

    Morphological differentiation of mosquitoes in the subgenera Culex (Culex) and Culex (Phenacomyia) in Guatemala is difficult, with reliable identification ensured only through examination of larval skins from individually reared specimens and associated male genitalia. We developed a multiplexed polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay to identify common Cx. (Cux.) and Cx. (Phc.). Culex (Cux.) chidesteri, Cx. (Cux.) coronator, Cx. (Cux.) interrogator, Cx. (Cux.) quinquefasciatus, Cx. (Cux.) nigripalpus/Cx. (Cux.) thriambus, and Cx. (Phc.) lactator were identified directly with a multiplexed primer cocktail comprising a conserved forward primer and specific reverse primers targeting ribosomal DNA (rDNA). Culex nigripalpus and Cx. thriambus were differentiated by restriction digest of homologous amplicons. The assay was developed and optimized using well-characterized specimens from Guatemala and the United States and field tested with unknown material from Guatemala. This assay will be a valuable tool for mosquito identification in entomological and arbovirus ecology studies in Guatemala. PMID:20682869

  3. Isolation of Coxiella burnetii by a centrifugation shell-vial assay from ticks collected in Cyprus: detection by nested polymerase chain reaction (PCR) and by PCR-restriction fragment length polymorphism analyses.

    PubMed

    Spyridaki, Ioanna; Psaroulaki, Anna; Loukaides, Fidias; Antoniou, Maria; Hadjichristodolou, Christos; Tselentis, Yannis

    2002-01-01

    Ticks are the principal vectors and reservoirs of Coxiella burnetii. The identification of isolates is necessary for understanding the clinical diversity of Q fever in different geographic areas. This is the first report of isolation of C. burnetii from ticks by the shell-vial assay and by nested polymerase chain reaction (PCR) assay for the detection of this pathogen in ticks. Of 141 ticks collected in Cyprus (Rhipicephalus sanguineus and Hyalloma spp.), 10% were found to be infected with C. burnetii. Three ticks were positive by hemolymph test, and 11 triturated ticks were positive by nested PCR. Three isolates were obtained by the centrifugation shell-vial technique. Analysis by PCR, then restriction fragment length polymorphism showed that the 3 Cyprus isolates had identical restriction profiles to reference strains Nine Mile and Q212. The methods described are useful in studying the epidemiology and ecology of C. burnetii.

  4. Identification of brucella species and biotypes using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

    PubMed

    Al Dahouk, Sascha; Tomaso, Herbert; Prenger-Berninghoff, Ellen; Splettstoesser, Wolf D; Scholz, Holger C; Neubauer, Heinrich

    2005-01-01

    Brucellosis is a worldwide zoonosis causing reproductive failures in livestock and a severe multi-organ disease in humans. The genus Brucella is divided into seven species and various biotypes differing in pathogenicity and host specificity. Although Brucella spp. represent a highly homogenous group of bacteria, RFLPs of selected genes display sufficient polymorphism to distinguish Brucella species and biovars. PCR-RFLP analysis shows excellent typeability, reproducibility, stability, and epidemiological concordance. Consequently, PCR-RFLP assays of specific gene loci can serve as tools for diagnostic, epidemiological, taxonomic, and evolutionary studies. Various PCR-RFLPs used for the identification of Brucella species and biotypes are reviewed.

  5. Energetics and Dynamics of Fragmentation of Protonated Leucine Enkephalin from Time- and Energy-Resolved Surface-Induced Dissociation Studies

    SciTech Connect

    Laskin, Julia

    2006-07-01

    Dissociation of singly protonated leucine enkephalin (YGGFL) was studied using surface-induced dissociation in a Fourier transform ion cyclotron resonance mass spectrometer specially configured for studying ion activation by collisions with surfaces. The energetics and dynamics of seven primary dissociation channels were deduced from modeling the time- and energy-resolved fragmentation efficiency curves for different fragment ions using an RRKM-based approach developed at the Environmental Molecular Sciences Laboratory (EMSL).

  6. The diazo route to diazonamide A. Studies on the indole bis-oxazole fragment.

    PubMed

    Davies, James R; Kane, Peter D; Moody, Christopher J

    2005-09-02

    [structure: see text] Various approaches to the indole bis-oxazole fragment of the marine secondary metabolite diazonamide A are described, all of which feature dirhodium(II)-catalyzed reactions of diazocarbonyl compounds in key steps. Thus, 3-bromophenylacetaldehyde is converted into an alpha-diazo-beta-ketoester, dirhodium(II)-catalyzed reaction of which with N-Boc-valinamide resulted in N-H insertion of the intermediate rhodium carbene to give a ketoamide that readily underwent cyclodehydration to give (S)-2-(1-tert-butoxycarbonylamino)-2-methylpropyl]-5-(3-bromobenzyl)oxazole-4-carboxamide, after ammonolysis of the initially formed ester. This aryl bromide was then coupled to a 3-formyl-indole-4-boronate under Pd catalysis to give the expected biaryl. Subsequent conversion of the aldehyde group into a second alpha-diazo-beta-ketoester gave a substrate for an intramolecular carbene N-H insertion, although attempts to effect this cyclization were unsuccessful. A second approach to an indole bis-oxazole involved an intermolecular rhodium carbene N-H insertion, followed by oxazole formation to give (S)-2-[1-tert-(butoxycarbonylamino)-2-methylpropyl]-5-methyloxazole-4-carboxamide. A further N-H insertion of this carboxmide with the rhodium carbene derived from ethyl 2-diazo-3-[1-(2-nitrobenzenesulfonyl)indol-3-yl]-3-oxopropanoate gave a ketoamide, cyclodehydration of which gave the desired indole bis-oxazole. Finally, the boronate formed from 4-bromotryptamine was coupled to another diazocarbonyl-derived oxazole to give the corresponding biaryl, deprotection and cyclization of which produced a macrocyclic indole-oxazole derivative. Subsequent oxidation and cyclodehydration incorporated the second oxazole and gave the macrocyclic indole bis-oxazole.

  7. [Was Beethoven's deafness caused by Paget's disease? Report of findings and study of skull fragments of Ludwig van Beethoven].

    PubMed

    Jesserer, H; Bankl, H

    1986-10-01

    Paget's disease of bone (osteitis deformans) has been repeatedly named as a possible cause for Ludwig van Beethoven's deafness. In 1985 a descendent of Franz Romeo Seligmann (a Viennese medical historian who in 1863 had studied Beethoven's mortal remains on the occasion of their relocation) presented to us three bone fragments allegedly from Beethoven's cranium. They represented fragments of the left parietal bone and the occiputum. It was possible to prove nearly with certainty that these bone fragments actually are Beethoven's. They did not show signs of Paget's disease of bone. It must therefore be concluded that Beethoven's deafness was not caused by Paget's osteitis deformans.

  8. Experimental Study of Stellar Reactions at CNS

    SciTech Connect

    Kubono, S.; Yamaguchi, H.; Wakabayashi, Y.; Amadio, G.; Hayakawa, S.; He, J. J.; Saito, A.; Teranishi, T.; Nishimura, S.; Fukunishi, N.; Iwasa, N.; Inafuku, K.; Kato, S.; Tanaka, M. H.; Fuchi, Y.; Moon, J. Y.; Kwon, K.; Lee, C. S.; Khiem, Le Hong; Chen, A.

    2006-11-02

    After a brief review on low-energy RI beam production technology, nuclear astrophysics programs at CNS are presented including a scope of the field in the Wako campus. The CRIB project involves a total development of the whole facility to maximize the low-energy RI beam intensities, including the ion source, the AVF cyclotron and the low-energy RI beam separator CRIB, Some recent nuclear astrophysics experiments performed with the RI beams were discussed, including the measurement of the 14O({alpha},p)17F reaction, the key stellar reaction for the onset of the high-temperature rp-process. The first experiment performed with a newly installed high-resolution magnetic spectrograph PA of CNS was also presented. Collaboration possibilities for nuclear astrophysics in the RIKEN campus are also touched.

  9. Theoretical study of chemical reactions in solution

    SciTech Connect

    Yokogawa, D.

    2015-12-31

    Quantum chemical calculations in solution are becoming more and more important in chemistry. Reference interaction site model self-consistent field (RISM-SCF) is one of the powerful approaches to perform quantum chemical calculations in solution. In this work, we developed a new generation of RISM-SCF, where a robust fitting method was newly introduced. We applied the new method to tautomerization reaction of cytosine in aqueous phase. Our calculation reproduced experimentally obtained relative stabilities and relative free energies correctly.

  10. Integrating edge effects into studies of habitat fragmentation: a test using meiofauna in seagrass.

    PubMed

    Warry, F Y; Hindell, J S; Macreadie, P I; Jenkins, G P; Connolly, R M

    2009-04-01

    Habitat fragmentation is thought to be an important process structuring landscapes in marine and estuarine environments, but effects on fauna are poorly understood, in part because of a focus on patchiness rather than fragmentation. Furthermore, despite concomitant increases in perimeter:area ratios with fragmentation, we have little understanding of how fauna change from patch edges to interiors during fragmentation. Densities of meiofauna were measured at different distances across the edges of four artificial seagrass treatments [continuous, fragmented, procedural control (to control for disturbance by fragmenting then restoring experimental plots), and patchy] 1 day, 1 week and 1 month after fragmentation. Experimental plots were established 1 week prior to fragmentation/disturbance. Samples were numerically dominated by harpacticoid copepods, densities of which were greater at the edge than 0.5 m into patches for continuous, procedural control and patchy treatments; densities were similar between the edge and 0.5 m in fragmented patches. For taxa that demonstrated edge effects, densities exhibited log-linear declines to 0.5 m into a patch with no differences observed between 0.5 m and 1 m into continuous treatments. In patchy treatments densities were similar at the internal and external edges for many taxa. The strong positive edge effect (higher densities at edge than interior) for taxa such as harpacticoid copepods implies some benefit of patchy landscapes. But the lack of edge effects during patch fragmentation itself demonstrates the importance of the mechanisms by which habitats become patchy.

  11. Identification of phytophthora isolates to species level using restriction fragment length polymorphism analysis of a polymerase chain reaction-amplified region of mitochondrial DNA.

    PubMed

    Martin, Frank N; Tooley, Paul W

    2004-09-01

    ABSTRACT Polymerase chain reaction primers spanning the mitochondrially encoded coxI and II genes have been identified that were capable of amplifying target DNA from all 152 isolates of 31 species in the genus Phytophthora that were tested. Digestion of the amplicons with restriction enzymes generated species-specific restriction fragment length polymorphism banding profiles that were effective for isolate classification to a species level. Of the 24 species in which multiple isolates were examined, intraspecific polymorphisms were not observed for 16 species, while 5 species exhibited limited intraspecific polymorphism that could be explained by the addition/loss of a single restriction site. Intraspecific polymorphisms were observed for P. megakarya, P. megasperma, and P. syringae; however, these differences may be a reflection of the variation that exists in these species as reported in the literature. Although digestion with AluI alone could differentiate most species tested, single digests with a total of four restriction enzymes were used in this investigation to enhance the accuracy of the technique and minimize the effect of intraspecific variability on correct isolate identification. The use of the computer program BioNumerics simplified data analysis and identification of isolates. Successful template amplification was obtained with DNA recovered from hyphae using a boiling miniprep procedure, thereby reducing the time and materials needed for conducting this analysis.

  12. Polymerase chain reaction-restriction fragment length polymorphism of the rpoB gene for identification of Mycobacterium avium subsp. paratuberculosis and differentiation of Mycobacterium avium subspecies.

    PubMed

    Whang, Jake; Lee, Byung Soo; Choi, Go-Eun; Cho, Sang-Nae; Kil, Park Young; Collins, Michael T; Shin, Sung Jae

    2011-05-01

    Mycobacterial speciation by polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis (PRA) of the rpoB gene was evaluated for identification of Mycobacterium avium subsp. paratuberculosis (MAP) and other Mycobacterium avium complex (MAC) members to the species or subspecies level by comparison with conventional methods including hsp65 sequencing, high-performance liquid chromatography, and PCR for accepted species- or subspecies-specific genomic targets. A total of 185 type and clinical mycobacterial strains from humans, animals, and environments were tested. A 360-bp PCR product was subsequently digested with MspI, HaeIII, and SmaI restriction enzymes. The PRA using SmaI restriction showed a unique digestion pattern for MAP distinguishing it from other MAC members and other Mycobacterium spp. Moreover, HaeIII and MspI restriction of the rpoB gene enabled MAC-species and -subspecies discrimination. The rpoB-PRA using SmaI or MspI and HaeIII restriction of the rpoB gene is a simple, convenient, and reliable confirmatory assay for simultaneous identification of MAP and other MAC members.

  13. Molecular identification of nine commercial flaffish species by polymerase chain reaction-restriction fragment length polymorphism analysis of a segment of the cytochrome b region.

    PubMed

    Sanjuan, Andrés; Comesaña, Angel S

    2002-06-01

    Commercial refrigerated or frozen flatfish fillets are sometimes mislabeled, and identification of these mislabeled products is necessary to prevent fraudulent substitution. Identification of nine commercial flatfish species (order Pleuronectiformes), Hippoglossus hippoglossus (halibut), Lepidorhombus boscii (four-spotted scaldfish), Lepidorhombus whiffiagonis (megrin), Platichthys flesus (flounder), Pleuronectes platessa (European plaice), Reinhardtius hippoglossoides (Greenland halibut), Scophthalmus maximus (turbot), Scophthalmus rhombus (brill), and Solea vulgaris (=Solea solea) (sole), was carried out on the basis of the amplification of a 486-bp segment of the mitochondrial genome (tRNA(Glu)/cytochrome b) by using the polymerase chain reaction (PCR) and universal primers. Sequences of PCR-amplified DNA from the flatfish species were used to select eight restriction enzymes (REs). The PCR products were cut with each RE, resulting in species-specific restriction fragment length polymorphism. Seven species groups could be identified by application of the single RE DdeI and six species groups by using HaeIII, HinfI, MaeI, or MboI. Different combinations of only a couple of these REs could unambiguously identify the nine flatfish species. Genetic polymorphisms of the target sequence were examined by comparison with previously published DNA sequences, and the results of this comparison confirmed the usefulness of this technique in distinguishing and genetically characterizing refrigerated or frozen pieces of these nine flatfish species.

  14. A Holistic Multi Evidence Approach to Study the Fragmentation Behaviour of Crystalline Mannitol

    NASA Astrophysics Data System (ADS)

    Koner, Jasdip S.; Rajabi-Siahboomi, Ali; Bowen, James; Perrie, Yvonne; Kirby, Daniel; Mohammed, Afzal R.

    2015-11-01

    Mannitol is an essential excipient employed in orally disintegrating tablets due to its high palatability. However its fundamental disadvantage is its fragmentation during direct compression, producing mechanically weak tablets. The primary aim of this study was to assess the fracture behaviour of crystalline mannitol in relation to the energy input during direct compression, utilising ball milling as the method of energy input, whilst assessing tablet characteristics of post-milled powders. Results indicated that crystalline mannitol fractured at the hydrophilic (011) plane, as observed through SEM, alongside a reduction in dispersive surface energy. Disintegration times of post-milled tablets were reduced due to the exposure of the hydrophilic plane, whilst more robust tablets were produced. This was shown through higher tablet hardness and increased plastic deformation profiles of the post-milled powders, as observed with a lower yield pressure through an out-of-die Heckel analysis. Evaluation of crystal state using x-ray diffraction/differential scanning calorimetry showed that mannitol predominantly retained the β-polymorph however x-ray diffraction provided a novel method to calculate energy input into the powders during ball milling. It can be concluded that particle size reduction is a pragmatic strategy to overcome the current limitation of mannitol fragmentation and provide improvements in tablet properties.

  15. A Holistic Multi Evidence Approach to Study the Fragmentation Behaviour of Crystalline Mannitol

    PubMed Central

    Koner, Jasdip S.; Rajabi-Siahboomi, Ali; Bowen, James; Perrie, Yvonne; Kirby, Daniel; Mohammed, Afzal R.

    2015-01-01

    Mannitol is an essential excipient employed in orally disintegrating tablets due to its high palatability. However its fundamental disadvantage is its fragmentation during direct compression, producing mechanically weak tablets. The primary aim of this study was to assess the fracture behaviour of crystalline mannitol in relation to the energy input during direct compression, utilising ball milling as the method of energy input, whilst assessing tablet characteristics of post-milled powders. Results indicated that crystalline mannitol fractured at the hydrophilic (011) plane, as observed through SEM, alongside a reduction in dispersive surface energy. Disintegration times of post-milled tablets were reduced due to the exposure of the hydrophilic plane, whilst more robust tablets were produced. This was shown through higher tablet hardness and increased plastic deformation profiles of the post-milled powders, as observed with a lower yield pressure through an out-of-die Heckel analysis. Evaluation of crystal state using x-ray diffraction/differential scanning calorimetry showed that mannitol predominantly retained the β-polymorph; however x-ray diffraction provided a novel method to calculate energy input into the powders during ball milling. It can be concluded that particle size reduction is a pragmatic strategy to overcome the current limitation of mannitol fragmentation and provide improvements in tablet properties. PMID:26553127

  16. Fragmented Adipose Tissue Graft for Bone Healing: Histological and Histometric Study in Rabbits’ Calvaria

    PubMed Central

    Oliveira, Lidiane C.; Giovanini, Allan F.; Abuabara, Allan; Klug, Luiz G.; Gonzaga, Carla C.; Zielak, João C.; Urban, Cícero A.

    2013-01-01

    Objective The adipose tissue represents an important reservoir of stem cells. There are few studies in the literature with which to histologically evaluate whether or not the adipose tissue graft is really a safe option to achieve bone repair. This study histologically analyzed the effect of fragmented autogenous adipose tissue grafts on bone healing in surgically created, critical-size defects (CSD) in a rabbit’s calvaria. Study design Forty-two New Zealand rabbits were used in this study. CSD that were 15 mm in diameter were created in the calvarium of each animal. The defects were randomly divided into two groups: in Group C (control), the defect was filled only by a blood clot and, in Group FAT (i.e., fragmented adipose tissue), the defect was filled with fragmented autogenous adipose tissue grafts. The groups were divided into subgroups (n = 7) for euthanasia at 7, 15, and 40 days after the procedure had been conducted. Histologic and histometric analyses were performed. Data were statistically analysed with ANOVA and Tukey’s tests (p < 0.05). Results The amount of bone formation did not show statistically significant differences seven days after the operation, which indicates that the groups had similar amounts of mineral deposition in the earlier period of the repair. Conversely, a significant of amount of bone matrix deposition was identified in the FAT group at 15 and 40 days following the operation, both on the border and in the body of the defect. Such an outcome was not found in the control group. Conclusion In this study, an autologous adipose tissue graft may be considered as likely biomaterial for bone regeneration, since it positively affected the amount of bone formation in surgically created CSD in the rabbits’ calvaria 40 days after the procedure had been performed. Further investigations with a longer time evaluation are warranted to determine the effectiveness of autologous adipose tissue graft in the bone healing. Key words

  17. Studies on Pyridazine Azide Cyclisation Reactions

    SciTech Connect

    Allan, R.D.; Greenwood, J.; Hambley, T.; Hanrahan, J.R.; Hibbs, D.E.; Itani, S.; Tran, H.; Turner, P.

    2010-11-16

    Reaction of sodium azide with 4-methyl-3,5,6-tribromopyridazine results in the formation of 3,5,6-triazide intermediate which could cyclise to give two possible bicyclic products while ab initio calculations show that the formation of a tricyclic compound is extremely energetically unfavourable. However, experimentally, only one major product is isolated. The structure of this unstable product has been conclusively established by X-ray crystallography as 3,5-diazido-4-methyl[1,5-b]tetrazolopyridazine confirming theoretical predictions.

  18. Development of Diagnostic Fragment Ion Library for Glycated Peptides of Human Serum Albumin: Targeted Quantification in Prediabetic, Diabetic, and Microalbuminuria Plasma by Parallel Reaction Monitoring, SWATH, and MSE*

    PubMed Central

    Korwar, Arvind M.; Vannuruswamy, Garikapati; Jagadeeshaprasad, Mashanipalya G.; Jayaramaiah, Ramesha H.; Bhat, Shweta; Regin, Bhaskaran S.; Ramaswamy, Sureshkumar; Giri, Ashok P.; Mohan, Viswanathan; Balasubramanyam, Muthuswamy; Kulkarni, Mahesh J.

    2015-01-01

    Human serum albumin is one of the most abundant plasma proteins that readily undergoes glycation, thus glycated albumin has been suggested as an additional marker for monitoring glycemic status. Hitherto, only Amadori-modified peptides of albumin were quantified. In this study, we report the construction of fragment ion library for Amadori-modified lysine (AML), N(ε)-(carboxymethyl)lysine (CML)-, and N(ε)-(carboxyethyl)lysine (CEL)-modified peptides of the corresponding synthetically modified albumin using high resolution accurate mass spectrometry (HR/AM). The glycated peptides were manually inspected and validated for their modification. Further, the fragment ion library was used for quantification of glycated peptides of albumin in the context of diabetes. Targeted Sequential Window Acquisition of all THeoretical Mass Spectra (SWATH) analysis in pooled plasma samples of control, prediabetes, diabetes, and microalbuminuria, has led to identification and quantification of 13 glycated peptides comprised of four AML, seven CML, and two CEL modifications, representing nine lysine sites of albumin. Five lysine sites namely K549, K438, K490, K88, and K375, were observed to be highly sensitive for glycation modification as their respective m/z showed maximum fold change and had both AML and CML modifications. Thus, peptides involving these lysine sites could be potential novel markers to assess the degree of glycation in diabetes. PMID:26023067

  19. COLLISIONS OF POROUS CLUSTERS: A GRANULAR-MECHANICS STUDY OF COMPACTION AND FRAGMENTATION

    SciTech Connect

    Ringl, Christian; Urbassek, Herbert M.; Bringa, Eduardo M.; Bertoldi, Dalia S.

    2012-06-20

    The collision of granular clusters can result in a number of complex outcomes from sticking to partial or full destruction of the clusters. These outcomes will contribute to the size distribution of dust aggregates, changing their optical properties and their capability to contribute to solid-state astrochemistry. We study the collision of two clusters of equal size, formed by approximately 7000 sub-{mu}m grains each, with a mass and velocity range that is difficult to sample in experiments. We obtain the outcome of the collision: compaction, fragmentation, and size distribution of ejecta, and type of outcome, as a function of velocity and impact parameter. We compare our results to other models and simulations, at both atomistic and continuum scales, and find some agreement together with some discrepancies. We also study collision-induced compaction as a function of cluster size, up to sizes of N = 250, 000, and find that for large clusters considerably higher compactions result at higher velocities.

  20. Neutron-induced reaction studies using stored ions

    NASA Astrophysics Data System (ADS)

    Glorius, Jan; Litvinov, Yuri A.; Reifarth, René

    2015-11-01

    Storage rings provide unique possibilities for investigations of nuclear reactions. Radioactive ions can be stored if the ring is connected to an appropriate facility and reaction studies are feasible at low beam intensities because of the recycling of beam particles. Using gas jet or droplet targets, charged particle-induced reactions on short-lived isotopes can be studied in inverse kinematics. In such a system a high-flux reactor could serve as a neutron target extending the experimental spectrum to neutron-induced reactions. Those could be studied over a wide energy range covering the research fields of nuclear astrophysics and reactor safety, transmutation of nuclear waste and fusion.

  1. C-H bond activation of methane in aqueous solution: a hybrid quantum mechanical/effective fragment potential study.

    PubMed

    Da Silva, Júlio C S; Rocha, Willian R

    2011-12-01

    In this study, we investigated the C-H bond activation of methane catalyzed by the complex [PtCl(4)](2-), using the hybrid quantum mechanical/effective fragment potential (EFP) approach. We analyzed the structures, energetic properties, and reaction mechanism involved in the elementary steps that compose the catalytic cycle of the Shilov reaction. Our B3LYP/SBKJC/cc-pVDZ/EFP results show that the methane activation may proceed through two pathways: (i) electrophilic addition or (ii) direct oxidative addition of the C-H bond of the alkane. The electrophilic addition pathway proceeds in two steps with formation of a σ-methane complex, with a Gibbs free energy barrier of 24.6 kcal mol(-1), followed by the cleavage of the C-H bond, with an energy barrier of 4.3 kcal mol(-1) . The activation Gibbs free energy, calculated for the methane uptake step was 24.6 kcal mol(-1), which is in good agreement with experimental value of 23.1 kcal mol(-1) obtained for a related system. The results shows that the activation of the C-H bond promoted by the [PtCl(4)](2-) catalyst in aqueous solution occurs through a direct oxidative addition of the C-H bond, in a single step, with an activation free energy of 25.2 kcal mol(-1), as the electrophilic addition pathway leads to the formation of a σ-methane intermediate that rapidly undergoes decomposition. The inclusion of long-range solvent effects with polarizable continuum model does not change the activation energies computed at the B3LYP/SBKJC/cc-pVDZ/EFP level of theory significantly, indicating that the large EFP water cluster used, obtained from Monte Carlo simulations and analysis of the center-of-mass radial pair distribution function, captures the most important solvent effects.

  2. Experimental and numerical study of thin fragments protection for radiographic detectors

    NASA Astrophysics Data System (ADS)

    Counilh, D.; Gillot, F.; Adolf, L.-M.; Silvin, P.; Rambert, N.; Hebert, D.; Bertron, I.; Bozier, O.

    2017-01-01

    To perform a non-intrusive measurement on a pyrotechnic setup, we usually use radiography. But, the X-ray generator and the detectors of the radiographic chain must be protected against the blast and. We carried out an experimental campaign to test the performances of various shielding. Representative cylindrical projectiles with various masses (from 20g to 40g) and aspect ratios (length to diameter ratio from 0.1 to 1) were launched with a gas gun at different initial velocities (from 1500m/s up to 2000m/s). Multiple shield configurations, based on assemblies of steel, aluminum and B4C plates were tested. The experimental results were combined with numerical studies to demonstrate the capabilities of the shield to stop fragments.

  3. Fragmentation dynamics of ionized neon trimer inside helium nanodroplets: a theoretical study.

    PubMed

    Bonhommeau, David; Viel, Alexandra; Halberstadt, Nadine

    2004-06-22

    We report a theoretical study of the fragmentation dynamics of Ne(3) (+) inside helium nanodroplets, following vertical ionization of the neutral neon trimer. The motion of the neon atoms is treated classically, while transitions between the electronic states of the ionic cluster are treated quantum mechanically. A diatomics-in-molecules description of the potential energy surfaces is used, in a minimal basis set consisting of three effective p orbitals on each neon atom for the missing electron. The helium environment is modeled by a friction force acting on the neon atoms when their speed exceeds the Landau velocity. A reasonable range of values for the corresponding friction coefficient is obtained by comparison with existing experimental measurements.

  4. NASTRAN buckling study of a linear induction motor reaction rail

    NASA Technical Reports Server (NTRS)

    Williams, J. G.

    1973-01-01

    NASTRAN was used to study problems associated with the installation of a linear induction motor reaction rail test track. Specific problems studied include determination of the critical axial compressive buckling stress and establishment of the lateral stiffness of the reaction rail under combined loads. NASTRAN results were compared with experimentally obtained values and satisfactory agreement was obtained. The reaction rail was found to buckle at an axial compressive stress of 11,400 pounds per square inch. The results of this investigation were used to select procedures for installation of the reaction rail.

  5. Theoretical Studies of Homogeneous and Heterogeneous Reactions in Silicon Systems

    DTIC Science & Technology

    1991-11-19

    and Si4 , and polymerization reactions leading to the higher silanes and silenes . Heterogeneous processes studied include sticking probabilities...to the higher silanes and silenes . Heterogeneous processes under study include sticking probabilities, scattering, and chemical reactions of H2 and...results for Si 2 in a silane CVD reactor have received qualitative experimental confirmation 24 . Consequently, our research group has devoted considerable

  6. Multichannel study on the fragmentation of the 1g9/2 isobaric analog resonance in 53Mn

    NASA Astrophysics Data System (ADS)

    Sziklai, J.; Cameron, J. A.; Szöghy, I. M.; Vass, T.

    1994-02-01

    Fragments of the 1g9/2 isobaric analog resonance in 53Mn corresponding to the 3.715 MeV state (Sn=0.57) in 53Cr were located using the 52Cr(p,p0), 52Cr(p,p1), 52Cr(p,p1γ), 52Cr(p,p2γ), and 52Cr(p,γ)53Mn reactions. Differential cross sections were measured in the 4.06-4.28 MeV, and the γ-excitation curves in the 4.04-4.35 MeV proton energy region. Spins, parities, and partial widths were determined with the aid of R-matrix analysis for all resonances observed in the region. The spins of the 1g9/2 resonance fragments were found independently from (p,p1γ), (p,p2γ), and (p,γ) angular distribution measurements and their analyses. Nineteen fragments were identified and their γ-branching ratios to low lying levels of 53Mn were also deduced. Partial widths for each fragment in all four channels were derived. Channel-channel correlations were calculated. Fine structure analyses were carried out in all open channels. Inelastic spectroscopic factors and Coulomb displacement energy for the 1g9/2 state were also derived.

  7. A lower fragmentation mass scale for clumps in high redshift galaxies: a systematic numerical study

    NASA Astrophysics Data System (ADS)

    Tamburello, Valentina; Mayer, Lucio; Shen, Sijing; Wadsley, James

    2015-08-01

    We perform a systematic study of the effect of sub-grid physics, resolution and structural parameters on the fragmentation of gas-rich galaxy discs into massive star forming clumps due to gravitational instability. We use the state-of-the-art zoom-in cosmological hydrodynamical simulation ARGO (Fiacconi et al. 2015) to set up the initial conditions of our models, and then carry out 26 high resolution controlled simulations of high-z galaxies using the GASOLINE2 code, which includes a modern, numerically robust SPH implementation.We find that when blast-wave feedback is included, the formation of long-lived, gravitationally bound clumps requires disc gas fractions of at least 50% and massive discs, which should have Vmax > 200 km/s at z ˜ 2, more massive than the typical galaxies expected at those redshifts.Less than 50 Myr after formation, clumps have stellar masses in the range 4 × 106 - 5 × 107 M⊙.Formation of clumps with mass exceeding ˜108 M⊙ is a rare occurrence, since it requires mergers between multiple massive clumps, as we verified by tracing back in time the particles belonging to such clumps. Such mergers happen after a few orbital times (˜200-300 Myr), but normally clumps migrate inward and are tidally disrupted on shorter timescales.Clump sizes are in the range 100-500 pc. We argue that giant clumps identified in observations (˜109 M⊙ and 1 kpc in size) might either have a different origin, such as minor mergers and clumpy gas accretion, or their sizes and masses may be overestimated due to resolution issues.Using an analytical model, already developed to explain the fragmentation scale in gravitationally unstable 3D protoplanetary discs, we can predict fairly accurately the characteristic gaseous masses of clumps soon after fragmentation, when standard Toome analysis becomes invalid.Due to their modest size, clumps have little effect on bulge growth as they migrate to the center. In our unstable discs a small bulge can form irrespective of

  8. Multitemporal analysis of forest fragmentation in Hindu Kush Himalaya-a case study from Khangchendzonga Biosphere Reserve, Sikkim, India.

    PubMed

    Sharma, Mohit; Areendran, G; Raj, Krishna; Sharma, Ankita; Joshi, P K

    2016-10-01

    Forests in the mountains are a treasure trove; harbour a large biodiversity; and provide fodder, firewood, timber and non-timber forest products; all of these are essential for human survival in the highest mountains on earth. The present paper attempts a spatiotemporal assessment of forest fragmentation and changes in land use land cover (LULC) pattern using multitemporal satellite data over a time span of around a decade (2000-2009), within the third highest protected area (PA) in the world. The fragmentation analysis using Landscape Fragmentation Tool (LFT) depicts a decrease in large core, edge and patches areas by 5.93, 3.64 and 0.66 %, respectively, while an increase in non-forest and perforated areas by 6.59 and 4.01 %, respectively. The land cover dynamics shows a decrease in open forest, alpine scrub, alpine meadows, snow and hill shadow areas by 2.81, 0.39, 8.18, 3.46 and 0.60 %, respectively, and there is an increase in dense forest and glacier area by 4.79 and 10.65 %, respectively. The change analysis shows a major transformation in areas from open forest to dense forest and from alpine meadows to alpine scrub. In order to quantify changes induced by forest fragmentation and to characterize composition and configuration of LULC mosaics, fragmentation indices were computed using Fragstats at class level, showing the signs of accelerated fragmentation. The outcome of the analysis revealed the effectiveness of geospatial tools coupled with landscape ecology in characterization and quantification of forest fragmentation and land cover changes. The present study provides a baseline database for sustainable conservation planning that will benefit the subsistence livelihoods in the region. Recommendations made based on the present analysis will help to recover forest and halt the pessimistic effects of fragmentation and land cover changes on biodiversity and ecosystem services in the region.

  9. The study on the reaction of rutile in Bayer liquor

    SciTech Connect

    Bi Shiwen; Li Dianfeng; Yang Yihong; Fu Gaofeng; Zhang Xin; Li Yan

    1996-10-01

    TiO{sub 2} is a harmful impurity in the digestion of producing alumina. TiO{sub 2} in bauxite usually exists in the forms of rutile, anatase and brookite. In this paper, the authors studied the reaction of rutile in sodium aluminate liquor, examined the effects of OH{sup {minus}} ion concentration, adding amount of CaO and temperature on the reaction, achieved the kinetics equation and calculated the activation energy of the reaction.

  10. Plans for Studies of (alpha,n) Reactions Relevant to Astrophysics via Inverse Reactions

    NASA Astrophysics Data System (ADS)

    Shima, T.; Nagai, Y.; Kii, T.; Kikuchi, T.; Baba, T.; Kobayashi, T.; Okazaki, F.

    1996-08-01

    (alpha,n) reactions in the keV energy region play important roles in astrophysical nucleosynthesis. In the primordial nucleosynthesis, it has been pointed out that a fluctuation of the baryon density distribution could be formed if the QCD phase transition from quark-gluon plasma to hadron gas occurred by first order. In that case the space was separated into the high density proton-rich zones and the low density neutron-rich ones, and in the neutron-rich zones nucleosynthesis could proceed beyond the mass gap at A = 8 via the reaction chains such as H-1(n,gamma)H-2(n,gamma)H-3(d,n)He-4(t,gamma)Li-7(n,gamma)Li-8(alpha,n)B- 11(n,ga mma)B-12(e(sup-)nu)C-12(n,gamma)C-13(n,gamma)C-14(n,gamma)C-15 ......, and so on. In the above nuclear reactions, the Li-8(alpha,n)B reaction plays quite a crucial role, because it can break through the mass gap at A = 8. (alpha,n) reactions of some light nuclei are also important as neutron sources for slow neutron capture process (s-process) of nucleosynthesis in stars. In low-mass and intermediate-mass (M < 10 Solar Mass) stars, neutrons are supposed to be supplied mainly by the C-13(alpha,n)O-16 reaction. On the other hand, the Ne-22(alpha,n)Mg-25 reaction is a candidate of the neutron source in massive stars with M > or = 10 Solar Mass. The contribution of the O-18(alpha,n)Ne-21 reaction to s-process in massive stars is still unknown. Since the temperatures of the above astrophysical sites correspond to the energy range of between a few ten and a few hundred keV, accurate data of the (alpha,n) reaction cross sections in the energy range are required for investigating nucleosynthesis. In order to measure these cross sections, not only direct (alpha,n) reactions but also inverse (n,alpha) reactions can be studied. In the following we would like to show experimental designs for studying several (alpha,n) reactions of astrophysical importance.

  11. Matrix isolation as a tool for studying interstellar chemical reactions

    NASA Technical Reports Server (NTRS)

    Ball, David W.; Ortman, Bryan J.; Hauge, Robert H.; Margrave, John L.

    1989-01-01

    Since the identification of the OH radical as an interstellar species, over 50 molecular species were identified as interstellar denizens. While identification of new species appears straightforward, an explanation for their mechanisms of formation is not. Most astronomers concede that large bodies like interstellar dust grains are necessary for adsorption of molecules and their energies of reactions, but many of the mechanistic steps are unknown and speculative. It is proposed that data from matrix isolation experiments involving the reactions of refractory materials (especially C, Si, and Fe atoms and clusters) with small molecules (mainly H2, H2O, CO, CO2) are particularly applicable to explaining mechanistic details of likely interstellar chemical reactions. In many cases, matrix isolation techniques are the sole method of studying such reactions; also in many cases, complexations and bond rearrangements yield molecules never before observed. The study of these reactions thus provides a logical basis for the mechanisms of interstellar reactions. A list of reactions is presented that would simulate interstellar chemical reactions. These reactions were studied using FTIR-matrix isolation techniques.

  12. Fusion and quasifission studies in reactions forming Rn via evaporation residue measurements

    NASA Astrophysics Data System (ADS)

    Shamlath, A.; Prasad, E.; Madhavan, N.; Laveen, P. V.; Gehlot, J.; Nasirov, A. K.; Giardina, G.; Mandaglio, G.; Nath, S.; Banerjee, Tathagata; Vinodkumar, A. M.; Shareef, M.; Jhingan, A.; Varughese, T.; Kumar, Dvgrks; Devi, P. Sandya; Khushboo, Jisha, P.; Kumar, Neeraj; Hosamani, M. M.; Kailas, S.

    2017-03-01

    Background: Formation of the compound nucleus (CN) is highly suppressed by quasifission in heavy-ion collisions involving massive nuclei. Though considerable progress has been made in the understanding of fusion-fission and quasifission, the exact dependence of fusion probability on various entrance channel variables is not completely clear, which is very important for the synthesis of new heavy and superheavy elements. Purpose: To study the interplay between fusion and quasifission in reactions forming CN in the boundary region where the fusion probability starts to deviate from unity. Methods: Fusion evaporation residue cross sections were measured for the Si,3028+180Hf reactions using the Hybrid Recoil Mass Analyser at IUAC, New Delhi. Experimental data were compared with data from other reactions forming the same CN or isotopes of the CN. Theoretical calculations were performed using the dinuclear system and statistical models. Results: Reduced evaporation residue cross sections were observed for the reactions studied compared with the asymmetric reaction forming the same CN, indicating fusion suppression in more symmetric systems. The observations are consistent with fission fragment measurements performed in the same or similar systems. Larger ER cross sections are observed with increase in mass in the isotopic chain of the CN. Conclusions: Fusion probability varies significantly with the entrance channels in reactions forming the same CN. While complete fusion occurs for the 16O+194Pt reaction, the fusion probability drops to approximately 60 -70 % for the 30Si+180Hf and less than 20 % for the 50Ti+160Gd reactions, respectively, forming the same CN at similar excitation energies.

  13. Fundamental studies of retrograde reactions in direct liquefaction

    SciTech Connect

    Serio, M.A.; Solomon, P.R.; Bassilakis, R.; Kroo, E.

    1989-01-01

    Most of the proposed processing schemes for improving liquefaction yields involve favoring bond-breaking and radical stabilization reactions over the retrograde reactions. The retrograde reactions are often encountered before liquefaction temperatures are reached. The objective of this program is to elucidate and model the retrograde reaction chemistry in direct coal liquefaction through the application of experimental techniques and theoretical models which have been successfully employed at Advanced Fuel Research (AFR) and SRI International (a subcontractor) to understand and predict coal reaction behavior. The study of retrograde reactions is being done using an integrated approach using extensive characterization of the liquefaction chemistry of three kinds of systems: (1) model polymers; (2) coal; and (3) modified coals.

  14. Transverse flow reactor studies of the dynamics of radical reactions

    SciTech Connect

    Macdonald, R.G.

    1993-12-01

    Radical reactions are in important in combustion chemistry; however, little state-specific information is available for these reactions. A new apparatus has been constructed to measure the dynamics of radical reactions. The unique feature of this apparatus is a transverse flow reactor in which an atom or radical of known concentration will be produced by pulsed laser photolysis of an appropriate precursor molecule. The time dependence of individual quantum states or products and/or reactants will be followed by rapid infrared laser absorption spectroscopy. The reaction H + O{sub 2} {yields} OH + O will be studied.

  15. Variational Flooding Study of a SN2 Reaction.

    PubMed

    Piccini, GiovanniMaria; McCarty, James J; Valsson, Omar; Parrinello, Michele

    2017-02-02

    We have studied the reaction dynamics of a prototypical organic reaction using a variationally optimized truncated bias to accelerate transitions between educt and product reactant states. The asymmetric SN2 nucleophilic substitution reaction of fluoromethane and chloromethane CH3F + Cl(-) ⇌ CH3Cl + F(-) is considered, and many independent biased molecular dynamics simulations have been performed at 600, 900, and 1200 K, collecting several hundred transitions at each temperature. The transition times and relative rate constants have been obtained for both reaction directions. The activation energies extracted from an Arrhenius plot compare well with standard static calculations.

  16. Electromagnetic studies of nuclear structure and reactions

    SciTech Connect

    Hersman, F.W.; Dawson, J.F.; Heisenberg, J.H.; Calarco, J.R.

    1990-06-01

    This report contains papers on the following topics: giant resonance studies; deep inelastic scattering studies; high resolution nuclear structure work; and relativistic RPA; and field theory in the Schroedinger Representation.

  17. Universality of fragment shapes

    PubMed Central

    Domokos, Gábor; Kun, Ferenc; Sipos, András Árpád; Szabó, Tímea

    2015-01-01

    The shape of fragments generated by the breakup of solids is central to a wide variety of problems ranging from the geomorphic evolution of boulders to the accumulation of space debris orbiting Earth. Although the statistics of the mass of fragments has been found to show a universal scaling behavior, the comprehensive characterization of fragment shapes still remained a fundamental challenge. We performed a thorough experimental study of the problem fragmenting various types of materials by slowly proceeding weathering and by rapid breakup due to explosion and hammering. We demonstrate that the shape of fragments obeys an astonishing universality having the same generic evolution with the fragment size irrespective of materials details and loading conditions. There exists a cutoff size below which fragments have an isotropic shape, however, as the size increases an exponential convergence is obtained to a unique elongated form. We show that a discrete stochastic model of fragmentation reproduces both the size and shape of fragments tuning only a single parameter which strengthens the general validity of the scaling laws. The dependence of the probability of the crack plan orientation on the linear extension of fragments proved to be essential for the shape selection mechanism. PMID:25772300

  18. Universality of fragment shapes

    NASA Astrophysics Data System (ADS)

    Domokos, Gábor; Kun, Ferenc; Sipos, András Árpád; Szabó, Tímea

    2015-03-01

    The shape of fragments generated by the breakup of solids is central to a wide variety of problems ranging from the geomorphic evolution of boulders to the accumulation of space debris orbiting Earth. Although the statistics of the mass of fragments has been found to show a universal scaling behavior, the comprehensive characterization of fragment shapes still remained a fundamental challenge. We performed a thorough experimental study of the problem fragmenting various types of materials by slowly proceeding weathering and by rapid breakup due to explosion and hammering. We demonstrate that the shape of fragments obeys an astonishing universality having the same generic evolution with the fragment size irrespective of materials details and loading conditions. There exists a cutoff size below which fragments have an isotropic shape, however, as the size increases an exponential convergence is obtained to a unique elongated form. We show that a discrete stochastic model of fragmentation reproduces both the size and shape of fragments tuning only a single parameter which strengthens the general validity of the scaling laws. The dependence of the probability of the crack plan orientation on the linear extension of fragments proved to be essential for the shape selection mechanism.

  19. Design study for a magnetically supported reaction wheel

    NASA Technical Reports Server (NTRS)

    Stocking, G.; Dendy, J.; Sabnis, A.

    1974-01-01

    Results are described of a study program in which the characteristics of a magnetically supported reaction wheel are defined. Tradeoff analyses are presented for the principal components, which are then combined in several reaction wheel design concepts. A preliminary layout of the preferred configuration is presented along with calculated design and performance parameters. Recommendations are made for a prototype development program.

  20. Limiting Fragmentation Behavior of Projectile Helium (Z = 2) Fragments in Nucleus--Nucleus Interactions at 14.6 A GeV

    NASA Astrophysics Data System (ADS)

    Kumar, Ashwini; Singh, Gurmukh; Singh, Bhartendu K.

    2012-12-01

    An analysis of projectile helium (Z = 2) fragments based on 855 minimum-bias inelastic events induced by 14.6 A GeV 28Si beam in a nuclear emulsion is presented in order to test the hypothesis of limiting fragmentation. The projected angular distributions of projectile helium fragments have been fitted with Gaussian curves in individual helium reaction channels and also in different emulsion target events. Furthermore, average emission angle of projectile helium fragments has been studied in individual helium reaction channels with different emulsion target groups. On the basis of pseudo-rapidity distribution, an energy independent limiting fragmentation behavior of projectile helium fragments is also investigated in the fragmentation region.

  1. Performance study of the anisotropic flow and reaction plane reconstruction in the CBM experiment

    NASA Astrophysics Data System (ADS)

    Mikhaylov, V.; Kugler, A.; Kushpil, V.; Selyuzhenkov, I.; Tlustý, P.

    2016-08-01

    The Projectile Spectator Detector (PSD) is a subsystem of the CBM experiment at the future FAIR facility designed to determine centrality and reaction plane orientation in the heavy-ion collisions. It will be done by measurement of the energy distribution of the heavy nucleons and nuclei fragments emitted close to the beam rapidity in forward direction. For the anticipated beam energies of FAIR SIS100 and SIS300 accelerators, different event generators (iQMD, UrQMD, DCM-QGSM, LA-QGSM and HSD) were used for the study of directed and elliptic proton flow in Au+Au collisions. Produced particles were transported with the GEANT4 Monte-Carlo using the CBM detector geometry. Performance of the reaction plane determination is shown for different PSD setups to demonstrate effects of the detector granularity and magnetic field. Simulation results are compared with the FOPI, AGS E877, E895 and STAR experimental data.

  2. Fragmentation properties of metals

    SciTech Connect

    Grady, D.E.; Kipp, M.E.

    1996-06-01

    In the present study we are developing an experimental fracture material property test method specific to dynamic fragmentation. Spherical test samples of the metals of interest are subjected to controlled impulsive stress loads by acceleration to high velocities with a light-gas launcher facility and subsequent normal impact on thin plates. Motion, deformation and fragmentation of the test samples are diagnosed with multiple flash radiography methods. The impact plate materials are selected to be transparent to the x-ray method so that only test metal material is imaged. Through a systematic series of such tests, both strain-to-failure and fragmentation resistance properties are determined through this experimental method. Fragmentation property data for several steels, copper, aluminum, tantalum and titanium have been obtained to date. Aspects of the dynamic data have been analyzed with computational methods to achieve a better understanding of the processes leading to failure and fragmentation, and to test an existing computational fragmentation model.

  3. Isotope labelling to study molecular fragmentation during the dielectric barrier discharge wet reforming of methane

    NASA Astrophysics Data System (ADS)

    Montoro-Damas, Antonio M.; Gómez-Ramírez, Ana; Gonzalez-Elipe, Agustín R.; Cotrino, José

    2016-09-01

    Isotope labelling is used to study the wet plasma reforming of methane in a dielectric barrier discharge reactor using D2O and CH4 as reactants. Besides the formation of CO and hydrogen as main products, different partitions of H and D atoms are found in the hydrogen (i.e., H2, HD, D2), methane (i.e., CH4, CH3D and CH2D2) and water (D2O, DHO) molecules detected by mass spectrometry as outlet gases of the plasma process. The effect of operating parameters such as applied current, residence time and the addition of oxygen to the reaction mixture is correlated with the H/D distribution in these molecules, the overall reaction yield and the energetic efficiency of the process. The results prove the plasma formation of intermediate excited species that rendering water and methane instead of CO and hydrogen greatly contribute to decrease the overall energy efficiency of the reforming process.

  4. Fundamental studies of retrograde reactions in direct liquefaction

    SciTech Connect

    Serio, M.A.; Solomon, P.R.; Kroo, E.; Charpenay, S.; Bassilakis, R.

    1991-12-17

    The overall objective of the program was to improve the understanding of retrograde reactions and their dependencies on coal rank and structure, and/or coal modifications and reaction conditions. Because retrograde reactions are competitive with bond breaking reactions, an understanding of both is required to shift the competition in favor of the latter. Related objectives were to clarify the conflicting observations reported in literature on such major topics as the role of oxygen groups in retrograde reactions and to provide a bridge from very fundamental studies on pure compounds to phenomenological studies on actual coal. This information was integrated into the FG-DVC model, which was improved and extended to the liquefaction context.

  5. Orientation and alignment effects in ion-induced fragmentation of water: A triple coincidence study

    SciTech Connect

    Rajput, Jyoti; Safvan, C. P.

    2014-10-28

    The technique of recoil ion momentum spectroscopy is employed to determine the complete momentum vectors for three fragment dissociation channels, [D{sub 2}O]{sup (q+2)} → (D{sup +} + D{sup +} + O{sup q+}) with q = 1, 2, or 3 formed in collisions of isolated water molecules with 450 keV Xe{sup 9+} ions. The kinetic energy released in each of these dissociation channels is measured and angular correlations between the fragment momenta are determined. From the angular correlations of the three fragment ions with the direction of the incoming beam, a strong anisotropy in the emission of recoil fragments is reported. It is inferred that the molecular plane prefers to lie orthogonal to the incoming beam direction with certain orientations being more preferred than others and a clear signature of non-coplanar dissociation is also observed.

  6. Evaluation of patients undergoing removal of glass fragments from injured hands: a retrospective study.

    PubMed

    Tuncer, Serdar; Ozcelik, Ismail Bulent; Mersa, Berkan; Kabakas, Fatih; Ozkan, Turker

    2011-08-01

    The hand is the body part most frequently injured by broken glass. Glass fragments lodged in soft tissues may result in numerous complications, such as infection, delayed healing, persistent pain, and late injury as a result of migration. Between 2005 and 2010, we removed 46 glass particles from the hands of 26 patients. The injuries were caused by the following: car windows broken during motor vehicle accidents in 11 patients (42%); fragments from broken glasses, dishes, or bottles in 9 (35%); the hand passing through glass in 5 (19%); and a fragment from a broken fluorescent lamp in 1 (4%) patient. Despite the efficacy of plain radiographs in detecting glass fragments, these are sometimes not obtained. Given the relatively low cost, accessibility, and efficacy of radiographs, and the adverse consequences of retained foreign bodies, the objections to obtaining radiographs should be few in diagnosing glass-related injuries of the hand.

  7. Avian pancreatic polypeptide fragments refold to native aPP conformation when combined in solution: a CD and VCD study.

    PubMed

    Copps, Jeffrey; Murphy, Richard F; Lovas, Sándor

    2006-09-01

    An equimolar mixture of avian pancreatic polypeptide (aPP) fragments aPP(1-11)-NH2 and Ac-aPP(12-36) had an electronic circular dichroism (ECD) spectrum that was similar to that of whole aPP in H2O and even more so in 30% (v/v) trifluoroethanol (TFE) in 15 mM Na2HPO4, but was different from the sum of the spectra of the individual fragments. The vibrational circular dichroism (VCD) spectrum of the combined fragments in 30% (v/v) TFE in 15 mM Na2HPO4 in D2O was also similar to that of the intact aPP and unlike the sum of the VCD spectra of the fragments. The interaction of these fragments is thus sufficient to support the conformation of whole aPP. This study demonstrates that VCD, in combination with ECD, is useful for the study of protein-protein interactions.

  8. Studies of heavy ion reactions and transuranic nuclei. Progress report, August 1, 1979-July 31, 1980. [Univ. of Rochester, New York, 8/1/79-7/31/80

    SciTech Connect

    Huizenga, J.R.

    1980-07-01

    The study of heavy-ion reaction mechanisms at the SuperHILAC and LAMPF is reported. Preprints of five articles and manuscripts of four recent conference papers are given, along with complete citations of publications and a list of personnel. Significant work was performed in the following areas: the bombarding energy dependence of the /sup 209/Bi + /sup 136/Xe reaction; the fragment yields for specific Z and A for projectile-like fragments produced in the reaction of 8.3-MeV/u /sup 56/Fe ions with targets of /sup 56/Fe, /sup 165/Ho, /sup 209/Bi, and /sup 238/U; and time distributions of fragments from delayed fission after muon capture for muonic /sup 235/U, /sup 238/U, /sup 237/Np, /sup 239/Pu, and /sup 242/Pu. (RWR)

  9. Surface plasmon field-enhanced fluorescence spectroscopy studies of primer extension reactions.

    PubMed

    Stengel, Gudrun; Knoll, Wolfgang

    2005-04-22

    Surface plasmon field-enhanced fluorescence spectroscopy (SPFS) utilizes the evanescent electromagnetic field of a surface plasmon to excite chromophors in close proximity to the surface. While conventional surface plasmon resonance spectroscopy allows the observation of surface reactions by means of refractive index changes, SPFS additionally provides a channel for the read-out of fluorescence changes. Thus, the detection limit for low mass compounds, whose adsorption is only accompanied by small refractive index changes, can be substantially improved by fluorescent labeling. In this study, we present the first example that utilizes SPFS to follow the dynamics of an enzymatic reaction. The elongation of surface-tethered DNA has been observed by the incorporation of Cy5-labeled nucleotides into the nascent strand by the action of DNA polymerase I (Klenow fragment). The technique offers a rapid way to determine the binding constant and the catalytic activity of a DNA processing enzyme, here exemplified by the Klenow fragment. Furthermore, the effect of mispaired bases in the primer/template duplex and the influence of different label densities have been studied. The resulting sensitivity for nucleotide incorporation, being in the femtomolar regime, combined with the specificity of the enzyme for fully complementary DNA duplexes suggest the application of this assay as a powerful tool for DNA detection.

  10. Measurement and management of human-induced patterns of forest fragmentation: a case study.

    PubMed

    Tole, Lise

    2006-06-01

    In many tropical developing countries, the twin pressures of population and poverty are resulting in substantial fragmentation of forests, increasing the probability of extinction for many species, Forest fragmentation occurs when large contiguous forests are perforated by small holes or broken up into edges and smaller patches to form a nonforested matrix of open spaces. Thus, forest fragmentation refers not only to the area of forest cleared, but also to the pattern of this clearance, the resulting forest's spatial properties. Both characteristics are important for species survivability. Apart from opening up forests to many abiotic and biotic influences, fragmentation can affect species dispersal and migration through its effects on forest connectivity. Landscape ecology conceptualizes connectivity as a gradient of critical thresholds, ranging from the large intact forest to the small unconnected forest patch. This article reports results from a multiple-scale analysis of forest fragmentation in Jamaica's Cockpit Country, an area of once contiguous forest now under threat from human encroachment. Spatial forest data derived from classification of ETM+ satellite imagery are used to measure fragmentation patterns representing various degrees of forest connectivity and density. The results suggest that, overall, 81% of the region is in forest. However, fragmentation patterns also suggest that this forest is riven with extensive perforations indicative of an early stage in the decline of contiguity. The results provided by the spatial fragmentation model are a first step in the design of effective conservation and rehabilitation plans for the area. The article concludes with a discussion of possible multiscale management options for the region.

  11. Cartesian positioning system for localization of blast and ballistic fragments: a phantom-based pilot study.

    PubMed

    Folio, Les; Fischer, Tatjana; Shogan, Paul J; Frew, Michael; Bunger, Rolf; Provenzale, James M

    2011-11-01

    Our purpose was to demonstrate the consistency of radiologists' three-dimensional measurements of simulated blast fragment locations in vitro in an effort to objectively localize retained fragments and wound paths. We designed a phantom consisting of 10 nail heads (simulating blast fragments) glued to wooden pegs that were randomly situated at distances from a reference point within a plastic tub. The x, y, and z coordinates of simulated fragments were recorded in Cartesian 3-space relative to the reference point. Computed tomography images of the phantom were acquired. Differences in x, y, and z positions as determined by three observers were summed for each fragment. Agreement between recordings of coordinates across readers was assessed using the intraclass correlation coefficient. Summed differences in coordinate positions as determined by readers ranged between 0.00 and 1.204 cm (mean: 0.732 cm). Across readers, the intraclass correlation coefficient for each dimension was >0.99. We found excellent agreement among readers with minimal discrepancy of measured locations of simulated fragments. Our results provide a foundation for trajectory analysis necessary to lead to automated organ damage reporting for immediate assessment in the emergency department and for forensic investigation and long-term epidemiological analysis.

  12. Direct studies of (α,p) reactions with HELIOS

    NASA Astrophysics Data System (ADS)

    Lai, Jianping; Blackmon, J. C.; Deibel, C. M.; Dimarco, D.; Gardiner, H.; Lauer, A.; Santiago-Gonzalez, D.; Williams, C.; Digiovine, B.; Greene, J.; Rohrer, J.; Helios Group At Argonne National Lab Collaboration

    2014-09-01

    In a variety of astrophysical processes, (α,p) type reactions have significant effects on final energy output and elemental abundances. However, only a handful of reactions have been measured due to technical limitations. Innovative new equipment and techniques, therefore, are necessary to extend measurement limits of these reactions rates. The HELIcal Orbit Spectrometer(HELIOS), serves as an important tool in studying reactions using radioactive ion beams at the Argonne Tandem Linac Accelerator System facility. With a specially designed gas target, we are able to study (α,p) reaction directly. HELIOS can separate protons from reactions with different energy states and the heavy recoils can be detected in coincidence by a high efficiency gas ionization detector. This combination has been successful in our pilot experiments. A series of (α,p) experiments using this setup in HELIOS are planned. We will start with 20Ne(α,p), which is crucial in Type Ia supernovae. A direct measurement of 30S(α,p), a key reaction in X ray burst, is also included in the near future plans and the beam development of 30S is in progress. Preliminary results will be presented. In a variety of astrophysical processes, (α,p) type reactions have significant effects on final energy output and elemental abundances. However, only a handful of reactions have been measured due to technical limitations. Innovative new equipment and techniques, therefore, are necessary to extend measurement limits of these reactions rates. The HELIcal Orbit Spectrometer(HELIOS), serves as an important tool in studying reactions using radioactive ion beams at the Argonne Tandem Linac Accelerator System facility. With a specially designed gas target, we are able to study (α,p) reaction directly. HELIOS can separate protons from reactions with different energy states and the heavy recoils can be detected in coincidence by a high efficiency gas ionization detector. This combination has been successful in our pilot

  13. Observation of anomalous reaction mean free paths of nuclear-projectile fragments in research emulsion from 2 A GeV heavy-ion collisions

    SciTech Connect

    Karant, Y.J.

    1981-07-01

    From an analysis of 1460 projectile fragment collisions in nuclear research emulsion exposed to 2.1 A GeV /sup 16/O and 1.9 A GeV /sup 56/Fe at the Bevalac, evidence is presented for the existence of an anomalously short interaction mean free path of projectile fragments for the first several cm after emission. The result is significant to beyond the 3 standard deviation confidence level.

  14. Jet-A reaction mechanism study for combustion application

    NASA Technical Reports Server (NTRS)

    Lee, Chi-Ming; Kundu, Krishna; Acosta, Waldo

    1991-01-01

    Simplified chemical kinetic reaction mechanisms for the combustion of Jet A fuel was studied. Initially, 40 reacting species and 118 elementary chemical reactions were chosen based on a literature review. Through a sensitivity analysis with the use of LSENS General Kinetics and Sensitivity Analysis Code, 16 species and 21 elementary chemical reactions were determined from this study. This mechanism is first justified by comparison of calculated ignition delay time with the available shock tube data, then it is validated by comparison of calculated emissions from the plug flow reactor code with in-house flame tube data.

  15. Jet-A reaction mechanism study for combustion application

    NASA Technical Reports Server (NTRS)

    Lee, Chi-Ming; Kundu, Krishna; Acosta, Waldo

    1991-01-01

    Simplified chemical kinetic reaction mechanisms for the combustion of Jet A fuel are studied. Initially 40 reacting species and 118 elementary chemical reactions were chosen based on the literature review of previous works. Through a sensitivity analysis with the use of LSENS General Kinetics and Sensitivity Analysis Code, 16 species and 21 elementary chemical reactions were determined from this study. This mechanism is first justified by comparison of calculated ignition delay time with available shock tube data, then it is validated by comparison of calculated emissions from plug flow reactor code with in-house flame tube data.

  16. Theoretical Studies of Elementary Hydrocarbon Species and Their Reactions

    SciTech Connect

    Allen, Wesley D.; Schaefer, III, Henry F.

    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. Theoretical Study of Sodium-Water Surface Reaction Mechanism

    NASA Astrophysics Data System (ADS)

    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).

  18. Severe Cutaneous Adverse Drug Reactions: A Clinicoepidemiological Study

    PubMed Central

    Sasidharanpillai, Sarita; Riyaz, Najeeba; Khader, Anza; Rajan, Uma; Binitha, Manikoth P; Sureshan, Deepthi N

    2015-01-01

    Background: Drug eruptions range from transient erythema to the life threatening severe cutaneous adverse reactions (SCAR) that encompass Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), acute generalized exanthematous pustulosis (AGEP) and drug reaction with eosinophilia and systemic symptoms complex (DRESS). Aims and Objectives: To study the clinical and epidemiological aspects of cutaneous adverse drug reactions (CADR). Materials and Methods: Ethical clearance was obtained from the institutional ethics committee. All patients admitted in the Dermatology ward of our tertiary care hospital with CADR (those who fit in the category of probable or possible drug reaction as per WHO casuality assessment) from first September 2011 to 31st August 2012 were included in this cross sectional study after obtaining written informed consent. The drug reaction patterns observed in the study population were determined and the common offending drugs were identified. Results: In the study, population of males outnumbered females and the majority were between 46 and 60 years of age. The commonest reaction pattern observed was SJS- TEN spectrum of illness and aromatic anticonvulsants were the common offending drugs. Prompt withdrawal of the culprit drug and administration of systemic steroids with or without I/V Ig reverted the adverse reaction in all except one. Conclusion: Severe drug reactions predominated as the study population was comprised of inpatients of a tertiary referral centre. Though; previous authors had reported a mortality rate of up to 20% in DRESS, all our patients with this reaction pattern, responded well to treatment. The mortality rate among TEN cases was much lower than the previous reports. Early diagnosis, prompt withdrawal of the suspected drug, careful monitoring for development of complications and immediate intervention can improve the prognosis of CADR. PMID:25657416

  19. The combined fragmentation and systematic molecular fragmentation methods.

    PubMed

    Collins, Michael A; Cvitkovic, Milan W; Bettens, Ryan P A

    2014-09-16

    Conspectus Chemistry, particularly organic chemistry, is mostly concerned with functional groups: amines, amides, alcohols, ketones, and so forth. This is because the reactivity of molecules can be categorized in terms of the reactions of these functional groups, and by the influence of other adjacent groups in the molecule. These simple truths ought to be reflected in the electronic structure and electronic energy of molecules, as reactivity is determined by electronic structure. However, sophisticated ab initio quantum calculations of the molecular electronic energy usually do not make these truths apparent. In recent years, several computational chemistry groups have discovered methods for estimating the electronic energy as a sum of the energies of small molecular fragments, or small sets of groups. By decomposing molecules into such fragments of adjacent functional groups, researchers can estimate the electronic energy to chemical accuracy; not just qualitative trends, but accurate enough to understand reactivity. In addition, this has the benefit of cutting down on both computational time and cost, as the necessary calculation time increases rapidly with an increasing number of electrons. Even with steady advances in computer technology, progress in the study of large molecules is slow. In this Account, we describe two related "fragmentation" methods for treating molecules, the combined fragmentation method (CFM) and systematic molecular fragmentation (SMF). In addition, we show how we can use the SMF approach to estimate the energy and properties of nonconducting crystals, by fragmenting the periodic crystal structure into relatively small pieces. A large part of this Account is devoted to simple overviews of how the methods work. We also discuss the application of these approaches to calculating reactivity and other useful properties, such as the NMR and vibrational spectra of molecules and crystals. These applications rely on the ability of these

  20. Quantum mechanical/effective fragment potential (QM/EFP) study of phosphate monoester aminolysis in aqueous solution.

    PubMed

    Ferreira, Dalva E C; Florentino, Bruno P D; Rocha, Willian R; Nome, Faruk

    2009-11-05

    In this work, we investigated the P-O bond cleavage of dianionic p-nitrophenyl phosphate monoester (p-NPP), with attack of aqueous methylamine on phosphorus, by using the hybrid quantum mechanical/effective fragment potential (QM/EFP) approach. We explored the structures, energetic properties, reaction mechanism, and charge distribution along the entire reaction coordinate. Our B3LYP/6-31++G(d,p)/EFP results show that the cleavage of the P-O bond of p-NPP proceeds through a concerted mechanism with an activation energy of about 26 kcal/mol and an activation free energy at 39 degrees C of 23.6 kcal/mol, in good agreement with the experimental value of 27 kcal/mol. The reaction involves a trigonal bipyramidal (TBP) transition state with less initial bonding to the nucleophile than to the leaving group. The extent of the P-O(nitrophenolate) bond dissociation at the transition state, with methylamine as the nucleophile, is less than that with OH(-). The computed charge distribution along the reaction coordinate is consistent with a progressive charge transfer from the nitrogen atom of methylamine to the phosphate unit along the reaction coordinate. A new strategy to build the initial EFP cluster, by running a classical Monte Carlo simulation and analyzing the center-of-mass radial pair distribution function, was also used.

  1. Studies of alpha-induced astrophysical reactions at CRIB

    SciTech Connect

    Yamaguchi, H.; Hashimoto, T.; Hayakawa, S.; Binh, D. N.; Kahl, D.; Kubono, S.

    2010-08-12

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo. Using the RI beams at CRIB, many measurements on proton alpha resonance scatterings, ({alpha},p) reactions, and others were performed in recent years mainly for studying astrophysical reactions and exotic nuclear structure. Among them, the results on the {sup 7}Li+{alpha} resonance scatterings are presented.

  2. Crossed molecular beam studies of atmospheric chemical reaction dynamics

    SciTech Connect

    Zhang, Jingsong

    1993-04-01

    The dynamics of several elementary chemical reactions that are important in atmospheric chemistry are investigated. The reactive scattering of ground state chlorine or bromine atoms with ozone molecules and ground state chlorine atoms with nitrogen dioxide molecules is studied using a crossed molecular beams apparatus with a rotatable mass spectrometer detector. The Cl + O3 → ClO + O2 reaction has been studied at four collision energies ranging from 6 kcal/mole to 32 kcal/mole. The derived product center-of-mass angular and translational energy distributions show that the reaction has a direct reaction mechanism and that there is a strong repulsion on the exit channel. The ClO product is sideways and forward scattered with respect to the Cl atom, and the translational energy release is large. The Cl atom is most likely to attack the terminal oxygen atom of the ozone molecule. The Br + O3 → ClO + O2 reaction has been studied at five collision energies ranging from 5 kcal/mole to 26 kcal/mole. The derived product center-of-mass angular and translational energy distributions are quite similar to those in the Cl + O3 reaction. The Br + O3 reaction has a direct reaction mechanism similar to that of the Cl + O3 reaction. The electronic structure of the ozone molecule seems to play the central role in determining the reaction mechanism in atomic radical reactions with the ozone molecule. The Cl + NO2 → ClO + NO reaction has been studied at three collision energies ranging from 10.6 kcal/mole to 22.4 kcal/mole. The center-of-mass angular distribution has some forward-backward symmetry, and the product translational energy release is quite large. The reaction proceeds through a short-lived complex whose lifetime is less than one rotational period. The experimental results seem to show that the Cl atom mainly attacks the oxygen atom instead of the nitrogen atom of the NO2

  3. Atmospheric chemistry: Laboratory studies of kinetics of important reactions

    NASA Astrophysics Data System (ADS)

    Smith, S. J.

    Experiments to measure the rate constants for some reactions of the atmospherically important nitrate radical (NO3) are described using the discharge-flow technique. The nitrate radical was monitored by optical absorption at lambda = 662 nm. The reactions of NO3 with some stable organic and inorganic substrates are reported. The temperature dependences of some of the rate constants were also determined (298 less than T less than 523 K). In most cases, computer simulation was used to extract the rate constant for the primary process because the time-dependent behavior of (NO3) was affected by secondary reactions of NO3 with products of the primary interaction. The Arrhenius parameter for the reactions of NO3 with CH3CH3, CH2CH2, CH3OH, CHCl3, and HCl were determined. The activation energies for the reactions studied between NO3 and some alkynes are presented along with the corresponding pre-exponential factors. Some reactions were studied at room temperature (298 plus or minus 2 K) only and the rate constants found (in units of cubic cm/molecule sec) are: buta-1,3-diene (1.8 x 10 (exp -13), isobutene (2.8 x 10 (exp -13), HBr (1.3 x 10 (exp -15) and hex-2-yne (3.0 x 10 (exp -14). Non-Arrhenius behavior was found in the reactions of NO3 with n-butane, isobutane and propene. The empirical variation of these rate constants with temperature is presented. The curvature of the Arrhenius plots is discussed in terms of (1) a temperature-dependent pre-exponential factor, and (2) the possibility that two competing channels, possessing differing activation energies, exist for each reaction. The atmospheric implications of these reactions are discussed with reference to the nighttime production of nitric acid and the importance of the these reactions as loss processes for NO3.

  4. Genotypic characterization of Indian isolates of infectious bursal disease virus strains by reverse transcription-polymerase chain reaction combined with restriction fragment length polymorphism analysis.

    PubMed

    Priyadharsini, C V; Senthilkumar, T M A; Raja, P; Kumanan, K

    2016-03-01

    The reverse transcription PCR (RT-PCR) combined with restriction fragment length polymorphism (RFLP) is used for the differentiation of classical virulent (cv), virulent (v) and very virulent (vv) strains of infectious bursal disease virus (IBDV) isolates from chicken bursal tissues in southern states of India. In the present study, six different isolates (MB11, HY12, PY12, BGE14, VCN14 and NKL14) of IBDV strains were subjected for genotyping along with vaccine virus (Georgia, intermediate strain) using RT-PCR for amplification of a 743 bp sequence in the hypervariable region of VP2 gene followed by restriction enzyme digestion with 5 different restriction enzymes (BspMI, SacI, HhaI, StuI and SspI). The RT-PCR products obtained from vvIBDV strains were digested by SspI enzyme except PY12, BGE14 and MB11 isolates. The SacI digested the isolate MB11, PY12 and the vaccine strain, but it did not cleave the very virulent isolates of IBDV. HhaI cleaved all the isolates with different restriction profile patterns. StuI digested all the vvIBDV isolates and BspMI was not able to differentiate field isolates from vaccine strain. Though RT-PCR combined with RFLP is a genotypic method, further confirmation of serotypes to distinguish the vvIBDV from cvIBDV has to be carried out using pathogenicity studies.

  5. The Role of Pebble Fragmentation in Planetesimal Formation. I. Experimental Study

    NASA Astrophysics Data System (ADS)

    Bukhari Syed, M.; Blum, J.; Wahlberg Jansson, K.; Johansen, A.

    2017-01-01

    Previous work on protoplanetary dust growth shows a halt at centimeter sizes owing to the occurrence of bouncing at velocities of ≳0.1 m s‑1 and fragmentation at velocities ≳1 m s‑1. To overcome these barriers, spatial concentration of centimeter-sized dust pebbles and subsequent gravitational collapse have been proposed. However, numerical investigations have shown that dust aggregates may undergo fragmentation during the gravitational collapse phase. This fragmentation in turn changes the size distribution of the solids and thus must be taken into account in order to understand the properties of the planetesimals that form. To explore the fate of dust pebbles undergoing fragmenting collisions, we conducted laboratory experiments on dust-aggregate collisions with a focus on establishing a collision model for this stage of planetesimal formation. In our experiments, we analyzed collisions of dust aggregates with masses between 0.7 and 91 g mass ratios between target and projectile from 1 to 126 at a fixed porosity of 65%, within the velocity range of 1.5–8.7 m s‑1, at low atmospheric pressure of ∼10‑3 mbar, and in free-fall conditions. We derived the mass of the largest fragment, the fragment size/mass distribution, and the efficiency of mass transfer as a function of collision velocity and projectile/target aggregate size. Moreover, we give recipes for an easy-to-use fragmentation and mass-transfer model for further use in modeling work. In a companion paper, we use the experimental findings and the derived dust-aggregate collision model to investigate the fate of dust pebbles during gravitational collapse.

  6. Studies of the Inheritance of Human Ribosomal DNA Variants Detected in Two-Dimensional Separations of Genomic Restriction Fragments

    PubMed Central

    Kuick, R.; Asakawa, J. I.; Neel, J. V.; Kodaira, M.; Satoh, C.; Thoraval, D.; Gonzalez, I. L.; Hanash, S. M.

    1996-01-01

    We have investigated the variation in human ribosomal DNA repeat units as revealed in two-dimensional electrophoretic separations of genomic restriction fragments that were end-labeled at NotI cleavage sites. The transcribed portion of the ribosomal DNA results in ~20 labeled fragments visible on each gel as multicopy spots. We have mapped these spots to the sequences responsible for their appearance on the gels, based on their migration positions and direct sequencing of spots, and describe several previously unreported sources of variation. By studying mother/father/child families we gained information on how much of the between-repeats variation is due to differences between and within repeat arrays on homologous chromosomes. Two instances in which a child exhibited more copies of a particular fragment than were present in the parents are described and hypothesized to be due to events such as multiple unequal sister-chromatid exchanges or gene conversions. PMID:8878694

  7. Bacterial expression and preliminary crystallographic studies of a 149-residue fragment of human Caprin-1

    PubMed Central

    Wu, Yuhong; Zhu, Jiang; Huang, Xiaolan; Du, Zhihua

    2015-01-01

    Caprin-1 is an RNA-binding protein which plays critical roles in several important biological processes, including cellular proliferation, the interferon-mediated antiviral innate immune response, the maintenance of synaptic plasticity and the formation of RNA stress granules. Caprin-1 has been implicated in the pathogenesis of several human diseases, including osteo­sarcoma, breast cancer, viral infections, hearing loss and neurodegenerative disorders. Despite the emerging biological and physiopathological significance of Caprin-1, no structural information is available for this protein. Moreover, Caprin-1 does not have sequence similarity to any other protein with a known structure. It is therefore expected that structural studies will play a particularly crucial role in revealing the functional mechanisms of Caprin-1. Here, a protein fragment of human Caprin-1 consisting of residues 112–260 was expressed, purified and crystallized. Native and Se-SAD data sets were collected to resolutions to 2.05 and 2.65 Å, respectively, in different space groups. PMID:25760709

  8. Study of Binding Interaction between Pif80 Protein Fragment and Aragonite

    PubMed Central

    Du, Yuan-Peng; Chang, Hsun-Hui; Yang, Sheng-Yu; Huang, Shing-Jong; Tsai, Yu-Ju; Huang, Joseph Jen-Tse; Chan, Jerry Chun Chung

    2016-01-01

    Pif is a crucial protein for the formation of the nacreous layer in Pinctada fucata. Three non-acidic peptide fragments of the aragonite-binding domain (Pif80) are selected, which contain multiple copies of the repeat sequence DDRK, to study the interaction between non-acidic peptides and aragonite. The polypeptides DDRKDDRKGGK (Pif80-11) and DDRKDDRKGGKDDRKDDRKGGK (Pif80-22) have similar binding affinity to aragonite. Solid-state NMR data indicate that the backbones of Pif80-11 and Pif80-22 peptides bound on aragonite adopt a random-coil conformation. Pif80-11 is a lot more effective than Pif80-22 in promoting the nucleation of aragonite on the substrate of β-chitin. Our results suggest that the structural arrangement at a protein-mineral interface depends on the surface structure of the mineral substrate and the protein sequence. The side chains of the basic residues, which function as anchors to the aragonite surface, have uniform structures. The role of basic residues as anchors in protein-mineral interaction may play an important role in biomineralization. PMID:27484975

  9. Study of Binding Interaction between Pif80 Protein Fragment and Aragonite

    NASA Astrophysics Data System (ADS)

    Du, Yuan-Peng; Chang, Hsun-Hui; Yang, Sheng-Yu; Huang, Shing-Jong; Tsai, Yu-Ju; Huang, Joseph Jen-Tse; Chan, Jerry Chun Chung

    2016-08-01

    Pif is a crucial protein for the formation of the nacreous layer in Pinctada fucata. Three non-acidic peptide fragments of the aragonite-binding domain (Pif80) are selected, which contain multiple copies of the repeat sequence DDRK, to study the interaction between non-acidic peptides and aragonite. The polypeptides DDRKDDRKGGK (Pif80-11) and DDRKDDRKGGKDDRKDDRKGGK (Pif80-22) have similar binding affinity to aragonite. Solid-state NMR data indicate that the backbones of Pif80-11 and Pif80-22 peptides bound on aragonite adopt a random-coil conformation. Pif80-11 is a lot more effective than Pif80-22 in promoting the nucleation of aragonite on the substrate of β-chitin. Our results suggest that the structural arrangement at a protein-mineral interface depends on the surface structure of the mineral substrate and the protein sequence. The side chains of the basic residues, which function as anchors to the aragonite surface, have uniform structures. The role of basic residues as anchors in protein-mineral interaction may play an important role in biomineralization.

  10. Quantification of contributions of molecular fragments for eye irritation of organic chemicals using QSAR study.

    PubMed

    Kar, Supratik; Roy, Kunal

    2014-05-01

    The eye irritation potential of chemicals has largely been evaluated using the Draize rabbit-eye test for a very long time. The Draize eye-irritation data on 38 compounds established by the European Center for Ecotoxicology and Toxicology of Chemicals (ECETOC) has been used in the present quantitative structure-activity relationship (QSAR) analysis in order to predict molar-adjusted eye scores (MES) and determine possible structural requisites and attributes that are primarily responsible for the eye irritation caused by the studied solutes. The developed model was rigorously validated internally as well as externally by applying principles of the Organization for Economic Cooperation and Development (OECD). The test for applicability domain was also carried out in order to check the reliability of the predictions. Important fragments contributing to higher MES values of the solutes were identified through critical analysis and interpretation of the developed model. Considering all the identified structural attributes, one can choose or design safe solutes with low eye irritant properties. The presented approach suggests a model for use in the context of virtual screening of relevant solute libraries. The developed QSAR model can be used to predict existing as well as future chemicals falling within the applicability domain of the model in order to reduce the use of animals.

  11. Bulk plasma fragmentation in a C{sub 4}F{sub 8} inductively coupled plasma: A hybrid modeling study

    SciTech Connect

    Zhao, Shu-Xia; Zhang, Yu-Ru; Gao, Fei; Wang, You-Nian; Bogaerts, Annemie

    2015-06-28

    A hybrid model is used to investigate the fragmentation of C{sub 4}F{sub 8} inductive discharges. Indeed, the resulting reactive species are crucial for the optimization of the Si-based etching process, since they determine the mechanisms of fluorination, polymerization, and sputtering. In this paper, we present the dissociation degree, the density ratio of F vs. C{sub x}F{sub y} (i.e., fluorocarbon (fc) neutrals), the neutral vs. positive ion density ratio, details on the neutral and ion components, and fractions of various fc neutrals (or ions) in the total fc neutral (or ion) density in a C{sub 4}F{sub 8} inductively coupled plasma source, as well as the effect of pressure and power on these results. To analyze the fragmentation behavior, the electron density and temperature and electron energy probability function (EEPF) are investigated. Moreover, the main electron-impact generation sources for all considered neutrals and ions are determined from the complicated C{sub 4}F{sub 8} reaction set used in the model. The C{sub 4}F{sub 8} plasma fragmentation is explained, taking into account many factors, such as the EEPF characteristics, the dominance of primary and secondary processes, and the thresholds of dissociation and ionization. The simulation results are compared with experiments from literature, and reasonable agreement is obtained. Some discrepancies are observed, which can probably be attributed to the simplified polymer surface kinetics assumed in the model.

  12. An experimental study of hydromagmatic fragmentation through energetic, non-explosive magma-water mixing

    USGS Publications Warehouse

    Mastin, L.G.; Spieler, O.; Downey, W.S.

    2009-01-01

    In this paper we report the first experimental investigation of non-explosive hydromagmatic fragmentation during energetic mixing with water. We mix magma and water by two methods: (1) pouring a basaltic melt between two converging water sprays; and (2) jetting basaltic melt at high pressure (3??MPa) through a nozzle into a tank of stagnant water. These experiments involved shear at relative velocities of ~ 5-16??m/s and vigorous mixing for less than a second, providing sufficient time for glassy rinds to grow but insufficient time for clot interiors to cool. In resulting fragments, we examined the gross morphology, which reflects fluid deformation during mixing, and surface textures, which reflect the growth and disruption of glassy rinds. We find major differences in both fragment morphology and surface texture between experiments. Water-spray experiments produced Pele's hair, thin bubble shards, melt droplets, and angular, fracture-bound droplet pieces. Melt-jet experiments produced mostly coarse (> 1??mm diameter), wavy fluidal fragments with broken ends. Fluidal surfaces of fragments produced by water-spray experiments were generally shiny under reflected light and, in microscopic examination, smooth down to micron scale, implying no disruption of glassy rinds, except for (a) rare flaking on Pele's hair that was bent prior to solidification; or (b) cracking and alligator-skin textures on segments of melt balls that had expanded before complete cooling. In contrast, textures of fluidal surfaces on fragments produced by melt-jet experiments are dull in reflected light and, in scanning electron images, exhibit ubiquitous discontinuous skins ("rinds") that are flaked, peeled, or smeared away in stripes. Adhering to these surfaces are flakes, blocks, and blobs of detached material microns to tens of microns in diameter. In the water-spray fragments, we interpret the scarcity of disrupted surface rinds to result from lack of bending after surfaces formed. In the

  13. An experimental study of hydromagmatic fragmentation through energetic, non-explosive magma-water mixing

    NASA Astrophysics Data System (ADS)

    Mastin, L. G.; Spieler, O.; Downey, W. S.

    2009-03-01

    In this paper we report the first experimental investigation of non-explosive hydromagmatic fragmentation during energetic mixing with water. We mix magma and water by two methods: (1) pouring a basaltic melt between two converging water sprays; and (2) jetting basaltic melt at high pressure (3 MPa) through a nozzle into a tank of stagnant water. These experiments involved shear at relative velocities of ~ 5-16 m/s and vigorous mixing for less than a second, providing sufficient time for glassy rinds to grow but insufficient time for clot interiors to cool. In resulting fragments, we examined the gross morphology, which reflects fluid deformation during mixing, and surface textures, which reflect the growth and disruption of glassy rinds. We find major differences in both fragment morphology and surface texture between experiments. Water-spray experiments produced Pele's hair, thin bubble shards, melt droplets, and angular, fracture-bound droplet pieces. Melt-jet experiments produced mostly coarse (> 1 mm diameter), wavy fluidal fragments with broken ends. Fluidal surfaces of fragments produced by water-spray experiments were generally shiny under reflected light and, in microscopic examination, smooth down to micron scale, implying no disruption of glassy rinds, except for (a) rare flaking on Pele's hair that was bent prior to solidification; or (b) cracking and alligator-skin textures on segments of melt balls that had expanded before complete cooling. In contrast, textures of fluidal surfaces on fragments produced by melt-jet experiments are dull in reflected light and, in scanning electron images, exhibit ubiquitous discontinuous skins ("rinds") that are flaked, peeled, or smeared away in stripes. Adhering to these surfaces are flakes, blocks, and blobs of detached material microns to tens of microns in diameter. In the water-spray fragments, we interpret the scarcity of disrupted surface rinds to result from lack of bending after surfaces formed. In the melt

  14. Exclusive studies of angular distributions in GeV hadron-induced reactions with {sup 197}Au

    SciTech Connect

    Hsi, W.; Kwiatkowski, K.; Wang, G.; Bracken, D.S.; Cornell, E.; Ginger, D.S.; Viola, V.E.; Korteling, R.G.; Morley, K.B.; Huang, R.; Lynch, W.G.; Tsang, M.B.; Xi, H.; Gimeno-Nogues, F.; Ramakrishnan, E.; Rowland, D.; Yennello, S.J.; Breuer, H.; Gushue, S.; Remsberg, L.P.; Botvina, A.; Friedman, W.A.

    1999-09-01

    Exclusive studies of angular distributions for intermediate-mass fragments (IMFs) produced in GeV hadron-induced reactions have been performed with the Indiana Silicon Sphere (ISiS) 4{pi} detector array. Special emphasis has been given to understanding the origin of sideways peaking, which becomes prominent in the angular distributions for beam momenta above about 10 GeV/c. Both the magnitude of the effect and the peak angle increase as a function of fragment multiplicity and charge. When gated on IMF kinetic energy, the angular distributions evolve from forward-peaked to near isotropy as the fragment kinetic energy decreases. Fragment-fragment angular-correlation analyses show no obvious evidence for a dynamic mechanism that might signal shock wave effects or the breakup of exotic geometric shapes such as bubbles or toroids. Moving-source and intranuclear cascade simulations suggest that the observed sideways peaking is of kinematic origin, arising from significant transverse momentum imparted to the heavy recoil nucleus during the fast cascade stage of the collision. A two-step cascade and statistical multifragmentation calculation is consistent with this assumption. {copyright} {ital 1999} {ital The American Physical Society}

  15. Exclusive studies of angular distributions in GeV hadron-induced reactions with [sup 197]Au

    SciTech Connect

    Hsi, W.; Kwiatkowski, K.; Wang, G.; Bracken, D.S.; Cornell, E.; Ginger, D.S.; Viola, V.E. ); Korteling, R.G. V5A I56); Morley, K.B. ); Huang, R.; Lynch, W.G.; Tsang, M.B.; Xi, H. ); Gimeno-Nogues, F.; Ramakrishnan, E.; Rowland, D.; Yennello, S.J. ); Breuer, H. ); Gushue, S.; Remsberg, L.P. ); Botvin

    1999-09-01

    Exclusive studies of angular distributions for intermediate-mass fragments (IMFs) produced in GeV hadron-induced reactions have been performed with the Indiana Silicon Sphere (ISiS) 4[pi] detector array. Special emphasis has been given to understanding the origin of sideways peaking, which becomes prominent in the angular distributions for beam momenta above about 10 GeV/c. Both the magnitude of the effect and the peak angle increase as a function of fragment multiplicity and charge. When gated on IMF kinetic energy, the angular distributions evolve from forward-peaked to near isotropy as the fragment kinetic energy decreases. Fragment-fragment angular-correlation analyses show no obvious evidence for a dynamic mechanism that might signal shock wave effects or the breakup of exotic geometric shapes such as bubbles or toroids. Moving-source and intranuclear cascade simulations suggest that the observed sideways peaking is of kinematic origin, arising from significant transverse momentum imparted to the heavy recoil nucleus during the fast cascade stage of the collision. A two-step cascade and statistical multifragmentation calculation is consistent with this assumption. [copyright] [ital 1999] [ital The American Physical Society

  16. A Monte Carlo study of the radiation quality dependence of DNA fragmentation spectra.

    PubMed

    Alloni, D; Campa, A; Belli, M; Esposito, G; Facoetti, A; Friedland, W; Liotta, M; Mariotti, L; Paretzke, H G; Ottolenghi, A

    2010-03-01

    We simulated the irradiation of human fibroblasts with gamma rays, protons and helium, carbon and iron ions at a fixed dose of 5 Gy. The simulations were performed with the biophysical Monte Carlo code PARTRAC. From the output of the code, containing in particular the genomic positions of the radiation-induced DNA double-strand breaks (DSBs), we obtained the DNA fragmentation spectra. Very small fragments, in particular those related to "complex lesions" (few tens of base pairs), are probably very important for the late cellular consequences, but their detection is not possible with the common experimental techniques. We paid special attention to the differences among the various ions in the production of these very small fragments; in particular, we compared the fragmentation spectra for ions of the same specific energy and for ions of the same LET (linear energy transfer). As found previously for iron ions, we found that the RBE (relative biological effectiveness) for DSB production was considerably higher than 1 for all high-LET radiations considered. This is at variance with the results obtainable from experimental data, and it is due to the ability to count the contribution of small fragments. It should be noted that for a given LET this RBE decreases with increasing ion charge, due mainly to the increasing mean energy of secondary electrons. A precise quantification of the DNA initial damage can be of great importance for both radiation protection, particularly in open-space long-term manned missions, and hadrontherapy.

  17. Experimental studies of reactions relevant for γ-process nucleosynthesis

    SciTech Connect

    Scholz, P.; Endres, J.; Hennig, A.; Mayer, J.; Netterdon, L.; Zilges, A.; Sauerwein, A.

    2014-05-09

    We report on our recent experimental studies of reactions relevant for the γ process nucleosynthesis. Applying the activation method using the Cologne Clover Counting Setup total cross sections of the reactions {sup 168}Yb(α,γ), {sup 168}Yb(α,n), and {sup 187}Re(α,n) could be obtained. Furthermore, the reaction {sup 89}Y(p,γ) was investigated via the in-beam technique with HPGe detectors at the high-efficiency g-ray spectrometer HORUS in Cologne in order to determine partial and total cross sections.

  18. DFT studies of the conformation and relative energies of alpha-maltotetraose (DP-4): An amylose fragment at atomic resolution

    Technology Transfer Automated Retrieval System (TEKTRAN)

    DFT optimization studies of more than one hundred conformations of a-maltotetraose have been carried out at the B3LYP/6-311++G** level of theory. The DP-4 fragments of predominately 4C1 chair residues include tightly bent forms, helix, band-flips, kinks, boat, and some 1C4 conformers. The three do...

  19. Fragmentation pathways and mechanisms of aromatic compounds in atmospheric pressure studied by GC-DMS and DMS-MS

    NASA Astrophysics Data System (ADS)

    Kendler, Shai; Lambertus, Gordon R.; Dunietz, Barry D.; Coy, Stephen L.; Nazarov, Erkinjon G.; Miller, Raanan A.; Sacks, Richard D.

    2007-06-01

    Differential mobility spectrometry (DMS) is a highly sensitive sensing technology capable of selecting and detecting ions based on the difference between ion mobility at high and low electric field. The combination of a micro-fabricated DMS with gas chromatography (GC) has allowed extensive investigation of the ion chemistry and collisionally induced dissociation (CID) of diaryl molecules on a millisecond timescale at temperatures up to 130 °C. DMS-pre-filtered time-of-flight mass spectrometry (DMS-MS) has been used to verify the chemical composition of the ion species resolved by GC-DMS. This work focuses on the fragmentation of diaryl compounds, including diphenyl methane (DPM) and bibenzyl (BB), using information from the DMS and DMS-MS spectra of a series of aromatic compounds. Density functional theory calculations have been used to investigate the geometry and the energy along the reaction coordinate for the loss of benzene from DPM·H+ and BB·H+ for comparison with GC-DMS and DMS-MS experimental results and with previously reported chemical ionization MS. DPM-H+ is observed to undergo field-induced fragmentation in the DMS to produce C7H7+(Bz+) and unobserved neutral benzene with a low energy barrier. In contrast, BB·H+ fragments to C8H9+ and benzene with a higher energy barrier. Calculated barriers and experimental results are in qualitative agreement. Depletion of the ionized fragments in favor of ion-neutral clusters was also observed at higher concentrations. It is suggested that CID in DMS can further enhance DMS analytical performance.

  20. A Study of Quark Fragmentation Using Kaons Produced in Association with Prompt $D_s^±/D^±$ Mesons

    SciTech Connect

    Singh, Niharika Ranjan

    2012-01-01

    Quarks are considered to be the fundamental constituents of hadronic matter, but they have never been observed as free particles. When quarks are produced at high energy colliders, they quickly form bound colorless states, which then decay to produce the particles observed in experiments. The process by which an initially free quark combines with other quarks to form a hadronic particle is called quark fragmentation and has been described using phenomenological models since quarks were first proposed. Since then, several models have been developed to describe the quark fragmentation phenomenon, and these have been tuned to reproduce many average properties of hadrons produced in high energy collisions. In this dissertation, we describe an analysis that probes the properties of particles produced in association with a hadron containing a charm quark that provides a way, for the first time, to study what is thought of as the second particle produced in the process of heavy quar k fragmentation. Data from proton anti-proton collisions was used to carry out this research, which were collected with the CDF II detector at the Fermilab Tevatron and corresponds to 360/pb-1 of integrated luminosity. We reconstruct $D_s^±$ and $D^±$ mesons, which contain charm quarks, and identify the kaons produced in association with them. The kinematic properties of these kaons are compared with predictions of the fragmentation models implemented in the PYTHIA and HERWIG event generators. We find that kaon production in association with $D_s^±$ mesons is enhanced at levels that are in agreement with the fragmentation models but observe differences in production rates of kaons that are produced later in the fragmentation process.

  1. Electronic coupling calculation and pathway analysis of electron transfer reaction using ab initio fragment-based method. I. FMO-LCMO approach

    NASA Astrophysics Data System (ADS)

    Nishioka, Hirotaka; Ando, Koji

    2011-05-01

    By making use of an ab initio fragment-based electronic structure method, fragment molecular orbital-linear combination of MOs of the fragments (FMO-LCMO), developed by Tsuneyuki et al. [Chem. Phys. Lett. 476, 104 (2009)], 10.1016/j.cplett.2009.05.069, we propose a novel approach to describe long-distance electron transfer (ET) in large system. The FMO-LCMO method produces one-electron Hamiltonian of whole system using the output of the FMO calculation with computational cost much lower than conventional all-electron calculations. Diagonalizing the FMO-LCMO Hamiltonian matrix, the molecular orbitals (MOs) of the whole system can be described by the LCMOs. In our approach, electronic coupling TDA of ET is calculated from the energy splitting of the frontier MOs of whole system or perturbation method in terms of the FMO-LCMO Hamiltonian matrix. Moreover, taking into account only the valence MOs of the fragments, we can considerably reduce computational cost to evaluate TDA. Our approach was tested on four different kinds of model ET systems with non-covalent stacks of methane, non-covalent stacks of benzene, trans-alkanes, and alanine polypeptides as their bridge molecules, respectively. As a result, it reproduced reasonable TDA for all cases compared to the reference all-electron calculations. Furthermore, the tunneling pathway at fragment-based resolution was obtained from the tunneling current method with the FMO-LCMO Hamiltonian matrix.

  2. Electronic coupling calculation and pathway analysis of electron transfer reaction using ab initio fragment-based method. I. FMO-LCMO approach.

    PubMed

    Nishioka, Hirotaka; Ando, Koji

    2011-05-28

    By making use of an ab initio fragment-based electronic structure method, fragment molecular orbital-linear combination of MOs of the fragments (FMO-LCMO), developed by Tsuneyuki et al. [Chem. Phys. Lett. 476, 104 (2009)], we propose a novel approach to describe long-distance electron transfer (ET) in large system. The FMO-LCMO method produces one-electron Hamiltonian of whole system using the output of the FMO calculation with computational cost much lower than conventional all-electron calculations. Diagonalizing the FMO-LCMO Hamiltonian matrix, the molecular orbitals (MOs) of the whole system can be described by the LCMOs. In our approach, electronic coupling T(DA) of ET is calculated from the energy splitting of the frontier MOs of whole system or perturbation method in terms of the FMO-LCMO Hamiltonian matrix. Moreover, taking into account only the valence MOs of the fragments, we can considerably reduce computational cost to evaluate T(DA). Our approach was tested on four different kinds of model ET systems with non-covalent stacks of methane, non-covalent stacks of benzene, trans-alkanes, and alanine polypeptides as their bridge molecules, respectively. As a result, it reproduced reasonable T(DA) for all cases compared to the reference all-electron calculations. Furthermore, the tunneling pathway at fragment-based resolution was obtained from the tunneling current method with the FMO-LCMO Hamiltonian matrix.

  3. Studies of heavy-ion reactions and transuranic nuclei. Progress report, September 1, 1992--August 31, 1993

    SciTech Connect

    Schroeder, W.U.

    1993-08-01

    This report contain papers on the following topics: The Cold-Fusion Saga; Decay Patterns of Dysprosium Nuclei Produced in {sup 32}S + {sup 118,124}Sn Fusion Reactions; Unexpected Features of Reactions Between Very Heavy Ions at Intermediate Bombarding Energies; Correlations Between Neutrons and Charged Products from the Dissipative Reaction {sup 197}Au+{sup 208}Pb at E/A = 29 MeV; Dissipative Dynamics of Projectile-Like Fragment Production in the Reaction {sup 209}Bi+{sup 136}Xe at E/A = 28.2 MeV; Dynamical Production of Intermediate-Mass Fragments in Peripheral {sup 209}Bi+{sup 136}Xe Collisions at E{sub lab}/A = 28.2 MeV; The Rochester 960-Liter Neutron Multiplicity Meter; A Simple Pulse Processing Concept for a Low-Cost Pulse-Shape-Based Particle Identification; A One-Transistor Preamplifier for PMT Anode Signals; A Five-Channel Multistop TDC/Event Handler for the SuperBall Neutron Multiplicity Meter; Construction of the SuperBall -- a 16,000-Liter Neutron Detector for Calorimetric Studies of Intermediate-Energy Heavy-Ion Reactions; A Computer Code for Light Detection Efficiency Calculations for Photo-multipliers of a Neutron Detector; Evaluation of Gd-Loaded Liquid Scintillators for the SuperBall Neutron Calorimeter; and Measurement of the Interaction of Cosmic-Ray {mu}{sup {minus}} with a Muon Telescope.

  4. Micro-Raman spectroscopic study of fine-grained, shock-metamorphosed rock fragments from the Australasian microtektite layer

    NASA Astrophysics Data System (ADS)

    Glass, B. P.; Fries, M.

    2008-11-01

    Shock-metamorphosed rock fragments have been found in the Australasian microtektite layer from the South China Sea. Previous X-ray diffraction (XRD) studies indicate that the most abundant crystalline phases in the rock fragments are coesite, quartz, and a 10 Å phase (mica/clay?). In addition, the presence of numerous other phases was suggested by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. In the present research, ten of the rock fragments, which had previously been studied using SEM/EDX, were studied by micro-Raman spectroscopy. The presence of K-feldspar, plagioclase, rutile, ilmenite, titanite, magnetite, calcite, and dolomite were confirmed. In addition, the high-pressure TiO2 polymorph with an α-PbO2 structure (i.e., TiO2II) was found in several rock fragments. Two grains previously thought to have been zircon, based on their compositions, were found to have Raman spectra that do not match the Raman spectra of zircon, reidite, or any of the possible decomposition products of zircon or their high-pressure polymorphs. We speculate that the ZrSiO4 phase might be a previously unknown high-pressure polymorph of zircon or one of its decomposition products (i.e., ZrO2 or SiO2). The presence of coesite and TiO2 II, and partial melting and vesiculation suggest that the rock fragments containing the unknown ZrSiO4 phase must have experienced shock pressures between 45 and 60 GPa. We conclude that micro-Raman spectroscopy, in combination with XRD and SEM/EDX, is a powerful tool for the study of small, fine-grained impact ejecta.

  5. Transdermal Rotigotine Improves Sleep Fragmentation in Parkinson's Disease: Results of the Multicenter, Prospective SLEEP-FRAM Study.

    PubMed

    Pagonabarraga, Javier; Piñol, Gerard; Cardozo, Adriana; Sanz, Pilar; Puente, Víctor; Otermín, Pilar; Legarda, Inés; Delgado, Tania; Serrano, Carmen; Balaguer, Ernest; Aguirregomozcorta, María; Álvarez, Ramiro; Kulisevsky, Jaime J

    2015-01-01

    Sleep disturbances occur frequently in patients with Parkinson's disease (PD). The aim of this study was to investigate the effects of rotigotine on sleep fluctuations in a sample of PD patients with self-reported complaints of nocturnal awakenings. This prospective, open-label, observational, and multicenter study enrolled consecutive outpatients with PD and administered rotigotine (mean dose 8.9 mg/day) for 3 months. The primary endpoint was the change from baseline in sleep fragmentation, assessed using the sleep maintenance subscale score of the Parkinson's Disease Sleep Scale (PDSS). The newly designed Parkinson's Disease Sleep Fragmentation Questionnaire (PD-SFQ) was used to measure other sleep parameters. A total of 62 patients were enrolled (mean age 70.2 years; 66% male). At 3 months, rotigotine significantly improved sleep fragmentation from baseline on the PDSS-2 sleep maintenance subscale (from 3.4 ± 0.9 to 1.9 ± 1.4; P < 0.0001). Rotigotine also significantly improved nocturnal motor symptoms (P < 0.0001), restless legs-like symptoms (P < 0.005), and nocturia (P = 0.004). Rotigotine significantly improved self-reported complaints of sleep fragmentation in PD patients and could be a useful treatment to improve this specific sleep problem in PD. However, these results are based on a small and clinically heterogeneous sample so they must be taken cautiously.

  6. Transdermal Rotigotine Improves Sleep Fragmentation in Parkinson's Disease: Results of the Multicenter, Prospective SLEEP-FRAM Study

    PubMed Central

    Pagonabarraga, Javier; Piñol, Gerard; Cardozo, Adriana; Sanz, Pilar; Puente, Víctor; Otermín, Pilar; Legarda, Inés; Delgado, Tania; Serrano, Carmen; Balaguer, Ernest; Aguirregomozcorta, María; Álvarez, Ramiro; Kulisevsky, Jaime J.

    2015-01-01

    Sleep disturbances occur frequently in patients with Parkinson's disease (PD). The aim of this study was to investigate the effects of rotigotine on sleep fluctuations in a sample of PD patients with self-reported complaints of nocturnal awakenings. This prospective, open-label, observational, and multicenter study enrolled consecutive outpatients with PD and administered rotigotine (mean dose 8.9 mg/day) for 3 months. The primary endpoint was the change from baseline in sleep fragmentation, assessed using the sleep maintenance subscale score of the Parkinson's Disease Sleep Scale (PDSS). The newly designed Parkinson's Disease Sleep Fragmentation Questionnaire (PD-SFQ) was used to measure other sleep parameters. A total of 62 patients were enrolled (mean age 70.2 years; 66% male). At 3 months, rotigotine significantly improved sleep fragmentation from baseline on the PDSS-2 sleep maintenance subscale (from 3.4 ± 0.9 to 1.9 ± 1.4; P < 0.0001). Rotigotine also significantly improved nocturnal motor symptoms (P < 0.0001), restless legs-like symptoms (P < 0.005), and nocturia (P = 0.004). Rotigotine significantly improved self-reported complaints of sleep fragmentation in PD patients and could be a useful treatment to improve this specific sleep problem in PD. However, these results are based on a small and clinically heterogeneous sample so they must be taken cautiously. PMID:25793143

  7. Wiring Techniques for the Fixation of Trochanteric Fragments during Bipolar Hemiarthroplasty for Femoral Intertrochanteric Fracture: Clinical Study and Technical Note

    PubMed Central

    Cho, Yongsuk; Kim, Junhyun; Kim, Dong-Won

    2017-01-01

    Purpose Femoral intertrochanteric fractures are common in the elderly. Appropriate surgical fixation of trochanteric fracture fragments can restore normal anatomical structure and ambulation, and can aid in the recovery of biomechanical function of the hip. We evaluated clinical outcomes of bipolar hemiarthroplasty using a wiring technique for trochanteric fracture fragment fixation. Materials and Methods From September 2006 to February 2015, a total of 260 cases underwent simultaneous bipolar hemiarthroplasty and wire fixation. A total of 65 patients (69 hips) with an average age of 78 years and more than one year of follow-up was included in the study. Using pre-, postoperative and follow-up radiograms, we evaluated wire fixation failure and also assessed changes in walking ability. Results Loosening or osteolysis around the stem was not observed; however, we did observe bone growth around the stem (54 cases), cortical hypertrophy (6 cases), a wide range of sclerotic lines but no stem subsidence (1 case), wire breakage (9 cases), and fracture fragment migration with no significant functional deficiency (2 cases). Conclusion Our study showed that additional wiring for trochanteric fracture fragment fixation following bipolar hemiarthroplasty can help restore normal anatomy. The added stability results in faster rehabilitation, and good clinical and radiographic outcomes. We recommend this procedure in this type of fracture. PMID:28316962

  8. Revealing Stepwise Mechanisms in Dipolar Cycloaddition Reactions: Computational Study of the Reaction between Nitrones and Isocyanates.

    PubMed

    Darù, Andrea; Roca-López, David; Tejero, Tomás; Merino, Pedro

    2016-01-15

    The mechanism of cycloaddition reactions of nitrones with isocyanates has been studied using density functional theory (DFT) methods at the M06-2X/cc-pVTZ level of theory. The exploration of the potential energy surfaces associated with two reactive channels leading to 1,2,4-oxadiazolidin-5-ones and 1,4,2-dioxazolidines revealed that the cycloaddition reaction takes place through a concerted mechanism in gas phase and in apolar solvents but a stepwise mechanism in polar solvents. In stepwise mechanisms, the first step of the reaction is a rare case in which the nitrone oxygen acts as a nucleophile by attacking the central carbon atom of the isocyanate (interacting with the π-system of the C═O bond) to give an intermediate. The corresponding transition structure is stabilized by an attractive electrostatic interaction favored in a polar medium. The second step of the reaction is the rate-limiting one in which the formation of 1,2,4-oxadiazolidin-5-ones or 1,4,2-dioxazolidines is decided. Calculations indicate that formation of 1,2,4-oxadiazolidin-5-ones is favored both kinetically and thermodynamically independently of the solvent, in agreement with experimental observations. Noncovalent interactions (NCI) and topological analysis of the gradient field of electron localization function (ELF) bonding confirmed the observed interactions.

  9. Karlotoxin synthetic studies: concise synthesis of a C(42–63) B-ring tetrahydropyran fragment

    PubMed Central

    Tomioka, Takashi; Takahashi, Yusuke; Maejima, Toshihide; Yabe, Yuki; Iwata, Hiroki; Hamann, Mark T.

    2013-01-01

    Starting from natural D-mannose, a C(42–63) B-ring tetrahydropyran fragment in karlotoxin 2 has been prepared via a common THP intermediate in a concise manner. E-selective Julia–Kocienski olefination efficiently assembled a C(51–63) chlorodiene subunit and a C(42–50) tetrahydropyran segment. PMID:24376284

  10. The Impact of Landscape Fragmentation on Atmospheric Flow: A Wind-Tunnel Study

    NASA Astrophysics Data System (ADS)

    Poëtte, Christopher; Gardiner, Barry; Dupont, Sylvain; Harman, Ian; Böhm, Margi; Finnigan, John; Hughes, Dale; Brunet, Yves

    2017-02-01

    Landscape discontinuities such as forest edges play an important role in determining the characteristics of the atmospheric flow by generating increased turbulence and triggering the formation of coherent tree-scale structures. In a fragmented landscape, consisting of surfaces of different heights and roughness, the multiplicity of edges may lead to complex patterns of flow and turbulence that are potentially difficult to predict. Here, we investigate the effects of different levels of forest fragmentation on the airflow. Five gap spacings (of length approximately 5h, 10h, 15h, 20h, 30h, where h is the canopy height) between forest blocks of length 8.7h, as well as a reference case consisting of a continuous forest after a single edge, were investigated in a wind tunnel. The results reveal a consistent pattern downstream from the first edge of each simulated case, with the streamwise velocity component at tree top increasing and turbulent kinetic energy decreasing as gap size increases, but with overshoots in shear stress and turbulent kinetic energy observed at the forest edges. As the gap spacing increases, the flow appears to change monotonically from a flow over a single edge to a flow over isolated forest blocks. The apparent roughness of the different fragmented configurations also decreases with increasing gap size. No overall enhancement of turbulence is observed at any particular level of fragmentation.

  11. The identification and differentiation of the Candida parapsilosis complex species by polymerase chain reaction-restriction fragment length polymorphism of the internal transcribed spacer region of the rDNA

    PubMed Central

    Barbedo, Leonardo Silva; Figueiredo-Carvalho, Maria Helena Galdino; Muniz, Mauro de Medeiros; Zancopé-Oliveira, Rosely Maria

    2016-01-01

    Currently, it is accepted that there are three species that were formerly grouped under Candida parapsilosis: C. para- psilosis sensu stricto, Candida orthopsilosis, andCandida metapsilosis. In fact, the antifungal susceptibility profiles and distinct virulence attributes demonstrate the differences in these nosocomial pathogens. An accurate, fast, and economical identification of fungal species has been the main goal in mycology. In the present study, we searched sequences that were available in the GenBank database in order to identify the complete sequence for the internal transcribed spacer (ITS)1-5.8S-ITS2 region, which is comprised of the forward and reverse primers ITS1 and ITS4. Subsequently, an in silico polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to differentiate the C. parapsilosis complex species. Ninety-eight clinical isolates from patients with fungaemia were submitted for analysis, where 59 isolates were identified as C. parapsilosis sensu stricto, 37 were identified as C. orthopsilosis, and two were identified as C. metapsilosis. PCR-RFLP quickly and accurately identified C. parapsilosis complex species, making this method an alternative and routine identification system for use in clinical mycology laboratories. PMID:27074256

  12. Correlation between landscape fragmentation and sandy desertification: a case study in Horqin Sandy Land, China.

    PubMed

    Ge, Xiaodong; Dong, Kaikai; Luloff, A E; Wang, Luyao; Xiao, Jun; Wang, Shiying; Wang, Qian

    2016-01-01

    The exact roles of landscape fragmentation on sandy desertification are still not fully understood, especially with the impact of different land use types in spatial dimension. Taking patch size and shape into consideration, this paper selected the Ratio of Patch Size and the Fractal Dimension Index to establish a model that reveals the association between the area of bare sand land and the fragmentation of different land use types adjacent to bare sand land. Results indicated that (1) grass land and arable land contributed the most to landscape fragmentation processes in the regions adjacent to bare sand land during the period 1980 to 2010. Grass land occupied 54 % of the region adjacent to bare sand land in 1980. The Ratio of Patch Size of grass land decreased from 1980 to 2000 and increased after 2000. The Fractal Dimension Index of grass increased during the period 1980 to 1990 and decreased after 1990. Arable land expanded significantly during this period. The Ratio of Patch Size of arable land increased from 1980 to 1990 and decreased since 1990. The Fractal Dimension Index of arable land increased from 1990 to 2000 and decreased after 2000. (2) The Ratio of Patch Size and the Fractal Dimension Index were significantly related to the area of bare sand land. The role of landscape fragmentation was not linear to sandy desertification. There were both positive and negative effects of landscape fragmentation on sandy desertification. In 1980, the Ratio of Patch Size and the Fractal Dimension Index were negatively related to the area of bare sand land, showing that the landscape fragmentation and regularity of patches contributed to the expansion of sandy desertification. In 1990, 2000, and 2010, the Ratio of Patch Size and the Fractal Dimension Index were mostly positively related to the area of bare sand land, showing the landscape fragmentation and regularity of patches contributed to the reversion of sandy desertification in this phase. The absolute values of

  13. Mixed quantum-classical studies of energy partitioning in unimolecular chemical reactions

    NASA Astrophysics Data System (ADS)

    Bladow, Landon Lowell

    A mixed quantum-classical reaction path Hamiltonian method is utilized to study the dynamics of unimolecular reactions. The method treats motion along the reaction path classically and treats the transverse vibrations quantum mechanically. The theory leads to equations that predict the disposai of the exit-channel potential energy to product translation and vibration. In addition, vibrational state distributions are obtained for the product normal modes. Vibrational excitation results from the curvature of the minimum energy reaction path. The method is applied to six unimolecular reactions: HF elimination from fluoroethane, 1,1-difluoroethane, 1,1-difluoroethene, and trifluoromethane; and HCl elimination from chloroethane and acetyl chloride. The minimum energy paths were calculated at either the MP2 or B3LYP level of theory. In all cases, the majority of the vibrational excitation of the products occurs in the HX fragment. The results are compared to experimental data and other theoretical results, where available. The best agreement between the experimental and calculated HX vibrational distributions is found for the halogenated ethanes, and the experimental deduction that the majority of the HX vibrational excitation arises from the potential energy release is supported. It is believed that the excess energy provided in experiments contributes to the poorer agreement between experiment and theory observed for HF elimination from 1,1-difluoroethene and trifluoromethane. An attempt is described to incorporate a treatment of the excess energy into the present method. However, the sign of the curvature coupling elements is then found to affect the dynamics. Overall, the method appears to be an efficient dynamical tool for modeling the disposal of the exit-channel potential energy in unimolecular reactions.

  14. Are microsatellite fragment lengths useful for population-level studies? The case of Polygala lewtonii (Polygalaceae)1

    PubMed Central

    Germain-Aubrey, Charlotte C.; Nelson, Cory; Soltis, Douglas E.; Soltis, Pamela S.; Gitzendanner, Matthew A.

    2016-01-01

    Premise of the study: Microsatellites, despite being commonly used population-level markers, contain biases because scoring relies solely on fragment length. Their complexity can lead to homoplasy, the effects of which are poorly understood. We investigated the impact of using fragment lengths, repeats, or flanking region sequences on common population-level analyses. Methods: Five polymorphic microsatellite markers amplified across the central Florida scrub endemic Polygala lewtonii (Polygalaceae) and its close, widespread congener P. polygama. We genotyped 147 individuals of P. lewtonii and 156 of P. polygama, and sequenced the amplicons of four markers across all individuals. We ran basic statistics, spatial clustering analysis, historical demographics, and migration tests. Results: One population of intermediate morphology was genetically clearly identified as P. polygama, making it the southernmost population of this species. Statistics were comparable between the fragment length and repeat numbers, with some notable differences. Flanking regions exhibited surprisingly high polymorphism between species, and between geographically distant conspecific populations. Discussion: The increasing use of markers developed in one species and amplified in another is only a good practice if precautions are taken, notably the sequencing of the fragments between species and populations. Flanking region sequences are a useful marker at the interspecific level. PMID:26949579

  15. Flexible bent rod model with a saturating induced dipole moment to study the electric linear dichroism of DNA fragments

    NASA Astrophysics Data System (ADS)

    Bertolotto, Jorge A.; Umazano, Juan P.

    2016-06-01

    In the present work we make a theoretical study of the steady state electric linear dichroism of DNA fragments in aqueous solution. The here developed theoretical approach considers a flexible bent rod model with a saturating induced dipole moment. The electric polarizability tensor of bent DNA fragments is calculated considering a phenomenological model which theoretical and experimental backgroung is presented here. The model has into account the electric polarizability longitudinal and transversal to the macroion. Molecular flexibility is described using an elastic potential. We consider DNA fragments originally bent with bending fluctuations around an average bending angle. The induced dipole moment is supposed constant once the electric field strength grows up at critical value. To calculate the reduced electric linear dichroism we determine the optical factor considering the basis of the bent DNA perpendicular to the molecular axis. The orientational distribution function has into account the anisotropic electric properties and the molecule flexibility. We applied the present theoretical background to fit electric dichroism experimental data of DNA fragments reported in the bibliography in a wide range of molecular weight and electric field. From these fits, values of DNA physical properties are estimated. We compare and discuss the results here obtained with the theoretical and experimental data presented by other authors. The original contributions of this work are: the inclusion of the transversal electric polarizability saturating with the electric field, the description of the electric properties with an electric polarizability tensor dependant on the bending angle and the use of an arc model originally bent.

  16. Theoretical QM/MM studies of enzymatic pericyclic reactions.

    PubMed

    Martí, S; Andrés, J; Moliner, V; Silla, E; Tuñón, I; Bertrán, J

    2010-03-01

    The chorismate to prephenate enzyme catalyzed reaction has been used in this review as the conduit to show different theoretical approaches that have been used over the years in our laboratory to explain its molecular mechanism. This pericyclic reaction has the advantage that other protein scaffolds such as catalytic antibodies or some promiscuous enzymes present certain chorismate mutase activity. The obtained results on all these protein environments, by comparison with the uncatalyzed reaction in solution, have been used to propose, as a general conclusion, that the origin of enzyme catalysis is in the relative electrostatic stabilization of the transition state with respect to the Michaelis complex. This feature implies that reactants of catalyzed reaction were closer to the transition state than those of the non-catalyzed reaction. From this hypothesis, and considering the features of the wild type chorismate mutases as the optimal catalyst for the reaction, some mutations on both kinds of alternative proteins have been proposed which would presumably enhance the rate constant of the chemical step.The studies presented in this paper demonstrate that the improvements and developments of the methods and techniques of theoretical and computational chemistry are now mature enough to model physic-chemical properties of biological systems with good accuracy. The combination of a potent computational protocol with molecular engineering techniques can be a promising methodology to develop novel enzymes with new or more efficient catalytic functions.

  17. Reaction dynamics studies for the system 7Be+58Ni

    NASA Astrophysics Data System (ADS)

    Torresi, D.; Mazzocco, M.; Acosta, L.; Boiano, A.; Boiano, C.; Diaz-Torres, A.; Fierro, N.; Glodariu, T.; Grilj, L.; Guglielmetti, A.; Keeley, N.; La Commara, M.; Martel, I.; Mazzocchi, C.; Molini, P.; Pakou, A.; Parascandolo, C.; Parkar, V. V.; Patronis, N.; Pierroutsakou, D.; Romoli, M.; Rusek, K.; Sanchez-Benitez, A. M.; Sandoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Stiliaris, E.; Strano, E.; Stroe, L.; Zerva, K.

    2015-04-01

    The study of reactions induced by exotic weakly bound nuclei at energies around the Coulomb barrier had attracted a large interest in the last decade, since the features of these nuclei can deeply affect the reaction dynamics. The discrimination between different reaction mechanisms is, in general, a rather difficult task. It can be achieved by using detector arrays covering high solid angle and with high granularity that allow to measure the reaction products and, possibly, coincidences between them, as, for example, recently done for stable weakly bound nuclei [1, 2]. We investigated the collision of the weakly bound nucleus 7Be on a 58Ni target at the beam energy of 1.1 times the Coulomb barrier, measuring the elastic scattering angular distribution and the energy and angular distributions of 3He and 4He. The 7Be radioactive ion beam was produced by the facility EXOTIC at INFN-LNL with an energy of 22 MeV and an intensity of ~3×105 pps. Results showed that the 4He yeld is about 4 times larger than 3He yield, suggesting that reaction mechanisms other than the break-up mostly produce the He isotopes. Theoretical calculations for transfer channels and compound nucleus reactions suggest that complete fusion accounts for (41±5%) of the total reaction cross section extracted from optical model analysis of the elastic scattering data, and that 3He and 4He stripping are the most populated reaction channels among direct processes. Eventually estimation of incomplete fusion contributions to the 3,4He production cross sections was performed through semi-classical calculations with the code PLATYPUS [3].

  18. Gas-Phase Fragmentation Analysis of Nitro-Fatty Acids

    PubMed Central

    Bonacci, Gustavo; Asciutto, Eliana K.; Woodcock, Steven R.; Salvatore, Sonia R.; Freeman, Bruce A.; Schopfer, Francisco J.

    2012-01-01

    Nitro-fatty acids are electrophilic signaling mediators formed in increased amounts during inflammation by nitric oxide and nitrite-dependent redox reactions. A more rigorous characterization of endogenously-generated species requires additional understanding of their gas-phase induced fragmentation. Thus, collision induced dissociation (CID) of nitroalkane and nitroalkene groups in fatty acids were studied in the negative ion mode to provide mass spectrometric tools for their structural characterization. Fragmentation of nitroalkanes occurred mainly through loss of the NO2− anion or neutral loss of HNO2. The CID of nitroalkenes proceeds via a more complex cyclization, followed by fragmentation to nitrile and aldehyde products. Gas-phase fragmentation of nitroalkene functional groups with additional γ or δ unsaturation occurred through a multiple step cyclization reaction process, leading to 5 and 6 member ring heterocyclic products and carbon chain fragmentation. Cyclization products were not obtained during nitroalkane fragmentation, highlighting the role of double bond π electrons during NO2− rearrangements, stabilization and heterocycle formation. The proposed structures, mechanisms and products of fragmentation are supported by analysis of 13C and 15N labeled parent molecules, 6 different nitroalkene positional isomers, 6 nitroalkane positional isomers, accurate mass determinations at high resolution and quantum mechanics calculations. Multiple key diagnostic ion fragments were obtained through this analysis, allowing for the precise placement of double bonds and sites of fatty acid nitration, thus supporting an ability to predict nitro positions in biological samples. PMID:21953257

  19. Theoretical study of reaction mechanism for NCO + HCNO

    NASA Astrophysics Data System (ADS)

    Zhang, Weichao; Du, Benni; Feng, Changjun

    2007-07-01

    A detailed quantum chemical study is performed on the mechanism of the NCO + HCNO reaction, which has never been studied by theory. The potential energy surface for this reaction is characterized at the B3LYP/6-311++G(d,p) level of theory, combined with high-level CBS-QB3 single point energy calculation. Four possible product channels have been investigated. From the calculations it can be seen that the formation of HCN + NO + CO is the dominant product channel, while the pathway to products of HCNN + CO 2 is expected to be minor one, and these conclusions are in good agreement with the experimental results.

  20. Computer-aided study of the mechanical behavior of the jaw bone fragments under uniaxial compression

    NASA Astrophysics Data System (ADS)

    Kolmakova, Tatyana V.

    2016-08-01

    The article presents the calculated results of the mechanical behavior of simulative bone mesovolumes under uniaxial compression with their architectonics corresponding to the human jaw bone fragments. The results of the calculation show that changes in the structure and mineral content of the bone fragments can lead to the change of their prevailing deformation response. New effective parameters were introduced to reflect the character of the distribution of stresses and strains in the bone mesovolumes. Implants are to be created and selected to correspond to the offered parameters and longitudinal modulus of elasticity of bone mesovolumes in order to maintain the stress and strain state existing in bone macrovolume during the implantation and in order to avoid bone restructuring through its borderline resorption.

  1. Feasibility study on a short-pulsed IR wavelength for effective calculus fragmentation

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook

    2015-05-01

    Laser-induced lithotripsy has been used for a minimally-invasive surgery to treat kidney-stone disease associated with urinary obstruction. A short-pulsed Tm:YAG laser (λ = 2.01 µm) was developed to improve fragmentation efficiency and was evaluated with a Ho:YAG laser (λ = 2.12 μm) as to its ablation feature and mass removal rate. Application of a train of sub-microsecond pulses with a lower energy at a frequency of 500 Hz created multiple events of cavitation that accompanied strong acoustic transients. During Tm:YAG irradiation, both high light absorption and secondary photomechanical impacts readily fragmented the calculus into small pieces (< 3 mm) and removed them 130 times faster than photothermal Ho:YAG lithotripsy. The proposed short-pulsed Tm:YAG approach may be an effective lithotripter for treating calculus disease.

  2. Target fragmentation in radiobiology

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Cucinotta, Francis A.; Shinn, Judy L.; Townsend, Lawrence W.

    1993-01-01

    Nuclear reactions in biological systems produce low-energy fragments of the target nuclei seen as local high events of linear energy transfer (LET). A nuclear-reaction formalism is used to evaluate the nuclear-induced fields within biosystems and their effects within several biological models. On the basis of direct ionization interaction, one anticipates high-energy protons to have a quality factor and relative biological effectiveness (RBE) of unity. Target fragmentation contributions raise the effective quality factor of 10 GeV protons to 3.3 in reasonable agreement with RBE values for induced micronuclei in bean sprouts. Application of the Katz model indicates that the relative increase in RBE with decreasing exposure observed in cell survival experiments with 160 MeV protons is related solely to target fragmentation events. Target fragment contributions to lens opacity given an RBE of 1.4 for 2 GeV protons in agreement with the work of Lett and Cox. Predictions are made for the effective RBE for Harderian gland tumors induced by high-energy protons. An exposure model for lifetime cancer risk is derived from NCRP 98 risk tables, and protraction effects are examined for proton and helium ion exposures. The implications of dose rate enhancement effects on space radiation protection are considered.

  3. Dynamic fragmentation of an alumina ceramic subjected to shockless spalling: An experimental and numerical study

    NASA Astrophysics Data System (ADS)

    Zinszner, J. L.; Erzar, B.; Forquin, P.; Buzaud, E.

    2015-12-01

    Ceramic materials are commonly used as protective materials for infantry soldiers and military vehicles. However, during impact, intense fragmentation of the ceramic material is observed. This fragmentation process has to be correctly numerically simulated if one wants to accurately model the dynamic behaviour of the ceramic material during impact. In this work, shockless spalling tests were performed on an alumina ceramic using the high-pulsed power generator (GEPI) equipment. These spalling tests allowed us to master the experimental strain-rate magnitude of the tensile loading applied to the specimen. The spall strength is observed to be rate dependant and the experimental configuration allowed for recovering damaged but unbroken specimen which gives further insights about the fragmentation process initiated in this ceramic material. The collected experimental data has been compared with corresponding numerical simulations conducted with the DFH (Denoual-Forquin-Hild) anisotropic damage model. This modelling approach relies on the description of the main basic micromechanisms activated at high loading rates using physical parameters related to the population of defects that produces multiple cracking in the ceramic material at high strain-rates. Very good agreement was observed between numerical simulations and experimental data in terms of free-surface velocity, size and location of the damaged zones along with crack density in these damaged zones.

  4. Study of the fragmentation of a displacement cascade in subcascades within the Binary Collision Approximation framework

    SciTech Connect

    Luneville, Laurence; Simone, David; Weber, William J

    2011-01-01

    When a material is subjected to irradiation, many primary defects are cre- ated at the atomic level by sequences of ballistic collision events to form highly disordered regions defined as displacement cascades. The long term evolution of materials under irradiation is dictated by the number and the spatial distribution of the surviving defects in the displacement cascade. The peculiar power law shape of collision cross sections is responsible for the frag- mentation of a displacement cascade into smaller subcascades. However, it remains difficult to define a subcascade. Within the fractal geometry frame- work, we demonstrate in this work that the set of atomic trajectories in a displacement cascade exhibit a fractal behavior. From this analysis, we present a new criterion to describe the fragmentation of a displacement cas- cade and to calculate the distribution and the number of defects from this fragmentation. Such an analysis provides the natural framework to estimate the number of defects created in a displacement cascade to integrate with results of MD simulations. From this defiintion of the fragmentation of a displacement cascade, this work gives some new insights to describe both the primary defects produced in a material under irradiation and then to compare different irradiations performed with different particles.

  5. Unified studies of structure and reactions in light unstable nuclei

    NASA Astrophysics Data System (ADS)

    Ito, Makoto

    2016-06-01

    The generalized two-center cluster model (GTCM), which can treat covalent, ionic and atomic configurations in general systems with two inert cores plus valence nucleons, is formulated in the basis of the microscopic cluster model. In this model, the covalent configurations constructed by the molecular orbital (MO) method and the atomic (or ionic) configuration obtained by the valence bonding (VB) method can be described in a consistent manner. GTCM is applied to the light neutron-rich system, 10,12Be = α + α + XN (X = 2,4), and the unified studies of the structural changes and the reaction problem are performed. In the structure study, the calculated energy levels are characterized in terms of the chemical bonding like structures, such as the covalent MO or ionic VB structures. The chemical bonding structures changes from level to level within a small energy interval. In the unbound region, the structure problem with the total system of α + α + XN and the reaction problem, induced by the collision of an asymptotic VB state of α+6,8He, are combined by GTCM. The properties of unbound resonant states are discussed in a close connection to the reaction mechanism, and some enhancement factors originated from the properties of the intrinsic states are predicted in the reaction observables. The unified calculation of the structures and the reactions is applied to the Coulomb shift problem in the mirror system, such the 10Be and 10C nuclei. The Coulomb displacement energy of the mirror systems are discussed.

  6. Singlet Oxygen Reactions with Flavonoids. A Theoretical – Experimental Study

    PubMed Central

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

    2012-01-01

    Detection of singlet oxygen emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, kT, and the reactive reaction rate constant, kr, for the reaction between singlet oxygen and several flavonoids. Values of kT determined in deuterated water, ranging from 2.4×107 M−1s−1 to 13.4×107 M−1s−1, for rutin and morin, respectively, and the values measured for kr, ranging from 2.8×105 M−1s−1 to 65.7×105 M−1s−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. PMID:22802966

  7. Computational Studies on Cinchona Alkaloid-Catalyzed Asymmetric Organic Reactions.

    PubMed

    Tanriver, Gamze; Dedeoglu, Burcu; Catak, Saron; Aviyente, Viktorya

    2016-06-21

    Remarkable progress in the area of asymmetric organocatalysis has been achieved in the last decades. Cinchona alkaloids and their derivatives have emerged as powerful organocatalysts owing to their reactivities leading to high enantioselectivities. The widespread usage of cinchona alkaloids has been attributed to their nontoxicity, ease of use, stability, cost effectiveness, recyclability, and practical utilization in industry. The presence of tunable functional groups enables cinchona alkaloids to catalyze a broad range of reactions. Excellent experimental studies have extensively contributed to this field, and highly selective reactions were catalyzed by cinchona alkaloids and their derivatives. Computational modeling has helped elucidate the mechanistic aspects of cinchona alkaloid catalyzed reactions as well as the origins of the selectivity they induce. These studies have complemented experimental work for the design of more efficient catalysts. This Account presents recent computational studies on cinchona alkaloid catalyzed organic reactions and the theoretical rationalizations behind their effectiveness and ability to induce selectivity. Valuable efforts to investigate the mechanisms of reactions catalyzed by cinchona alkaloids and the key aspects of the catalytic activity of cinchona alkaloids in reactions ranging from pharmaceutical to industrial applications are summarized. Quantum mechanics, particularly density functional theory (DFT), and molecular mechanics, including ONIOM, were used to rationalize experimental findings by providing mechanistic insights into reaction mechanisms. B3LYP with modest basis sets has been used in most of the studies; nonetheless, the energetics have been corrected with higher basis sets as well as functionals parametrized to include dispersion M05-2X, M06-2X, and M06-L and functionals with dispersion corrections. Since cinchona alkaloids catalyze reactions by forming complexes with substrates via hydrogen bonds and long

  8. Reaction dynamics and mechanism of the Cl + HD(v = 1) reaction: a quantum mechanical study.

    PubMed

    González-Sánchez, L; Aldegunde, J; Jambrina, P G; Aoiz, F J

    2013-08-15

    Time-independent quantum mechanical calculations have been performed in order to characterize the dynamics and stereodynamics of Cl + HD reactive collisions. Calculations have been carried out at two different total energy values and for various initial states using the adiabatic potential energy surface by Bian and Werner [J. Chem. Phys. 2000, 112, 220]. Special attention has been paid to the reaction with HD(v = 1) for which integral and differential cross-sections have been calculated and the effect of vibrational vs translational energy on the reactivity has been examined. In addition, the reactant polarization parameters and polarization-dependent differential cross-sections have been determined. From these results, the spatial preferences of the reaction and the extent of the control of the cross sections achievable through a suitable preparation of the reactants have been also studied. The directional requirements are tighter for the HCl channel than for the DCl one. Formation of the products takes place preferentially when the rotational angular momentum of the HD molecule is perpendicular to the reactants approach direction. Cross-sections and polarization moments computed from the scattering calculations have been compared with experimental results by Kandel et al. [J. Chem. Phys. 2000, 112, 670] for the reaction with HD(v = 1) produced by stimulated Raman pumping. The agreement so obtained is good, and it improves the accordance found in previous calculations with other methodologies and potential energy surfaces.

  9. Study of 10 Be and 16 C cluster structure by means of breakup reactions

    NASA Astrophysics Data System (ADS)

    Dell'Aquila, D.

    2016-03-01

    The study of cluster structures in nuclei far from stability represents a valid tool to explore the nuclear force in few-body systems. In this paper we discuss a new experimental investigation of the structure of 10Be and 16C nuclei by means of projectile sequential break-up reactions induced on CH2 target at intermediate-energies. Their spectroscopy is obtained via a relative energy analysis of break-up fragments with the CHIMERA multi-detector. From 4He+6He correlations we suggest the presence of a new state at about 13.5MeV in 10Be. The inspection of 6He+10Be break-up channel reveals the existence of a possible high-lying excited state at 20.6MeV in 16C. Finally, new perspectives concerning the improvement of the present results are discussed.

  10. Theoretical studies of the dynamics of chemical reactions

    SciTech Connect

    Wagner, A.F.

    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.

  11. Emotional Reactions of Students in Field Education: An Exploratory Study

    ERIC Educational Resources Information Center

    Litvack, Andrea; Mishna, Faye; Bogo, Marion

    2010-01-01

    An exploratory study using qualitative methodology was undertaken with recent MSW graduates (N=12) from 2 graduate social work programs to identify and describe the students' emotional reactions to experiences in field education. Significant and interrelated themes emerged including the subjective and unique definitions of emotionally charged…

  12. Study of Daedalus Interstellar Spacecraft Reaction Chamber and Thrust Structure

    NASA Astrophysics Data System (ADS)

    Reddy, S. K.; Benaroya, H.

    Project Daedalus was the 1978 trade study that proved the feasibility of space travel utilizing fusion-based propulsion (Inertial Confinement Fusion). This paper analyzes some of the key structural aspects of the Daedalus spacecraft, in particular, the reaction chamber and thrust structure that is integral to the Daedalus spacecraft, which supports the loads resulting from the fusion reactions. First, the reaction chamber is studied computationally in terms of static loading and vibrational characteristics utilizing the finite element method. Next, a proposed bracing system is integrated into the reaction chamber and the effects are studied. Lastly, the field coils with their supporting truss structure are added to the assembly. Concepts are introduced for actuators and course-correction mechanisms that ensure the spacecraft maintains the required trajectory to rendezvous with the target system. Present-day materials and manufacturing considerations are explored based on the assumptions made in the Daedalus study. Testing, qualification, and assembly of the spacecraft are also discussed. This paper is a summary of the first author's Master's Thesis at Rutgers University.

  13. [The contamination under polymerase chain reaction studies: problems and solutions].

    PubMed

    Titov, V N; Ameliushkina, V A; Rozhkova, T A

    2015-01-01

    The study was carried out to determine risk factors of false positive and false negative results under polymerase chain reaction-analysis of clinical material. The samples with high viral load can be the source of false positive results. The contamination with nucleic acids can occur at any section of polymerase chain reaction analysis. The study data permitted to establish that the most sensitive stage is isolation and purification of nucleic acids especially under manual mode of operation. The detection of positive signal in most samples of one setting indicates total contamination. The cases when only several samples are polluted are special challenge. The presence of sample with high concentration of viral nucleic acid and several samples with low concentration in one setting means necessity of repeated analysis beginning with stage of isolation of nucleic acid. The analysis of curves of accumulation of products of amplification, their forms and positioning on chart is the obligatory stage of polymerase chain reaction study in real time regimen. These actions permit to exclude the readouts of false negative testing results to departments. The study conclusions are equipotent for polymerase chain reaction testing of any nucleic acid targets.

  14. Toluene pyrolysis studies and high temperature reactions of propargyl chloride

    SciTech Connect

    Kern, R.D.; Chen, H.; Qin, Z.

    1993-12-01

    The main focus of this program is to investigate the thermal decompositions of fuels that play an important role in the pre-particle soot formation process. It has been demonstrated that the condition of maximum soot yield is established when the reaction conditions of temperature and pressure are sufficient to establish a radical pool to support the production of polyaromatic hydrocarbon species and the subsequent formation of soot particles. However, elevated temperatures result in lower soot yields which are attributed to thermolyses of aromatic ring structures and result in the bell-shaped dependence of soot yield on temperature. The authors have selected several acyclic hydrocarbons to evaluate the chemical thermodynamic and kinetic effects attendant to benzene formation. To assess the thermal stability of the aromatic ring, the authors have studied the pyrolyses of benzene, toluene, ethylbenzene, chlorobenzene and pyridine. Time-of-flight mass spectrometry (TOF) is employed to analyze the reaction zone behind reflected shock waves. Reaction time histories of the reactants, products, and intermediates are constructed and mechanisms are formulated to model the experimental data. The TOF work is often performed with use of laser schlieren densitometry (LS) to measure density gradients resulting from the heats of various reactions involved in a particular pyrolytic system. The two techniques, TOF and LS, provide independent and complementary information about ring formation and ring rupture reactions.

  15. A model study of sequential enzyme reactions and electrostatic channeling.

    PubMed

    Eun, Changsun; Kekenes-Huskey, Peter M; Metzger, Vincent T; McCammon, J Andrew

    2014-03-14

    We study models of two sequential enzyme-catalyzed reactions as a basic functional building block for coupled biochemical networks. We investigate the influence of enzyme distributions and long-range molecular interactions on reaction kinetics, which have been exploited in biological systems to maximize metabolic efficiency and signaling effects. Specifically, we examine how the maximal rate of product generation in a series of sequential reactions is dependent on the enzyme distribution and the electrostatic composition of its participant enzymes and substrates. We find that close proximity between enzymes does not guarantee optimal reaction rates, as the benefit of decreasing enzyme separation is countered by the volume excluded by adjacent enzymes. We further quantify the extent to which the electrostatic potential increases the efficiency of transferring substrate between enzymes, which supports the existence of electrostatic channeling in nature. Here, a major finding is that the role of attractive electrostatic interactions in confining intermediate substrates in the vicinity of the enzymes can contribute more to net reactive throughput than the directional properties of the electrostatic fields. These findings shed light on the interplay of long-range interactions and enzyme distributions in coupled enzyme-catalyzed reactions, and their influence on signaling in biological systems.

  16. Theoretical studies of atmospheric reaction mechanisms in the troposphere.

    PubMed

    Vereecken, Luc; Francisco, Joseph S

    2012-10-07

    The chemistry of the atmosphere encompasses a vast number of reactions acting on a plethora of intermediates. These reactions, occurring sequentially and in parallel, give rise to intertwined and irreducible mechanisms describing the complex chemical transformations of organic and inorganic compounds in the atmosphere. The complexity of this system is that it requires combined experimental, theoretical, and modeling approaches to elucidate the characteristics of the individual reactions, and their mutual interaction. In this review, we describe recent results from quantum chemical and theoretical kinetic studies of relevance to atmospheric chemistry. The review first summarizes the most commonly used theoretical methodologies. It then examines the VOC oxidation initiation channels by OH, O(3), NO(3) and Cl, followed by the reactions of the alkyl, alkoxy, alkylperoxy and Criegee intermediates active in the subsequent oxidation steps. Specific systems such as the oxidation of aromatics and the current state of knowledge on OH-regeneration in VOC oxidation are also discussed, as well as some inorganic reactions.

  17. Sum Frequency Generation Studies of Hydrogenation Reactions on Platinum Nanoparticles

    SciTech Connect

    Krier, James M.

    2013-08-31

    Sum Frequency Generation (SFG) vibrational spectroscopy is used to characterize intermediate species of hydrogenation reactions on the surface of platinum nanoparticle catalysts. In contrast to other spectroscopy techniques which operate in ultra-high vacuum or probe surface species after reaction, SFG collects information under normal conditions as the reaction is taking place. Several systems have been studied previously using SFG on single crystals, notably alkene hydrogenation on Pt(111). In this thesis, many aspects of SFG experiments on colloidal nanoparticles are explored for the first time. To address spectral interference by the capping agent (PVP), three procedures are proposed: UV cleaning, H2 induced disordering and calcination (core-shell nanoparticles). UV cleaning and calcination physically destroy organic capping while disordering reduces SFG signal through a reversible structural change by PVP.

  18. Studying the triple - α reaction in hyperspherical harmonic approach

    NASA Astrophysics Data System (ADS)

    Nguyen, Ngoc; Nunes, Filomena

    2010-11-01

    The triple-α reaction is studied by using hyperspherical harmonic (HH) method [1]. Starting from three body model, we determine the 2^+ state and the 0^+ resonance as well as the quadrupole strength function B(E2). The triple-α reaction rate are calculated. We also carefully consider the contributions of the nonresonant continuum states to the reaction rate at low temperature (T <=10^8 K). The results are compared with [2,3].[4pt] [1] I. J. Thompson, F. M. Nunes, B. V. Danilin, Comput.Phys.Comm. 161, 87-107 (2004).[0pt] [2] K.Ogata, M.Kan, M.Kamimura, Prog. Theor. Phys. 122, 1055 (2009).[0pt] [3] R. de Diego, E. Garrido, D.V. Fedorov, A.S. Jensen, arXiv:1005.5647v1.

  19. Energetics and dynamics of fragmentation of protonated leucine enkephalin from time- and energy-resolved surface-induced dissociation studies.

    PubMed

    Laskin, Julia

    2006-07-13

    Dissociation of singly protonated leucine enkephalin (YGGFL) was studied using surface-induced dissociation (SID) in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) specially configured for studying ion activation by collisions with surfaces. The energetics and dynamics of seven primary dissociation channels were deduced from modeling the time- and energy-resolved fragmentation efficiency curves for different fragment ions using an RRKM-based approach developed in our laboratory. The following threshold energies and activation entropies were determined in this study: E(0) = 1.20 eV and DeltaS++ = -20 eu(1) (MH(+)-->b(5)); E(0) = 1.14 eV and DeltaS++ = -14.7 eu (MH(+)-->b(4)); E(0) = 1.42 eV and DeltaS++ = -2.5 eu (MH(+)-->b(3)); E(0) = 1.30 eV and DeltaS++ = -4.1 eu (MH(+)-->a(4)); E(0) = 1.37 eV and DeltaS++ = -5.2 eu (MH(+)-->y ions); E(0) = 1.50 eV and DeltaS++ = 1.6 eu (MH(+)-->internal fragments); E(0) = 1.62 eV and DeltaS++ = 5.2 eu (MH(+)-->F). Comparison with Arrhenius activation energies reported in the literature demonstrated for the first time the reversal of the order of activation energies as compared to threshold energies for dissociation.

  20. A tandem mass spectrometric study of bile acids: interpretation of fragmentation pathways and differentiation of steroid isomers.

    PubMed

    Qiao, Xue; Ye, Min; Liu, Chun-fang; Yang, Wen-zhi; Miao, Wen-juan; Dong, Jing; Guo, De-an

    2012-02-01

    Bile acids are steroids with a pentanoic acid substituent at C-17. They are the terminal products of cholesterol excretion, and play critical physiological roles in human and animals. Bile acids are easy to detect but difficult to identify by using mass spectrometry due to their poly-ring structure and various hydroxylation patterns. In this study, fragmentation pathways of 18 free and conjugated bile acids were interpreted by using tandem mass spectrometry. The analyses were conducted on ion trap and triple quadrupole mass spectrometers. Upon collision-induced dissociation, the conjugated bile acids could cleave into glycine or taurine related fragments, together with the steroid skeleton. Fragmentations of free bile acids were further elucidated, especially by atmospheric pressure chemical ionization mass spectrometry in positive ion mode. Aside from universally observed neutral losses, eliminations occurred on bile acid carbon rings were proposed for the first time. Moreover, four isomeric 5β-cholanic acid hydroxyl derivatives (3α,6α-, 3α,7β-, 3α,7α-, and 3α,12α-) were differentiated using electrospray ionization in negative ion mode: 3α,7β-OH substituent inclined to eliminate H(2)O and CH(2)O(2) groups; 3α,6α-OH substituent preferred neutral loss of two H(2)O molecules; 3α,12α-OH substituent apt to lose the carboxyl in the form of CO(2) molecule; and 3α,7α-OH substituent exhibited no further fragmentation after dehydration. This study provided specific interpretation for mass spectra of bile acids. The results could contribute to bile acid analyses, especially in clinical assays and metabonomic studies.

  1. The cause and consequences of a satellite fragmentation: a case study

    NASA Astrophysics Data System (ADS)

    Johnson, N. L.

    1999-01-01

    The fragmentation of a Pegasus Hydrazine Auxiliary Propulsion System upper stage on 3 June 1996 stands as the worst satellite breakup on record in terms of cataloged orbital debris. In addition to the more than 700 debris large enough to be tracked (approximately 10 cm in diameter or greater) in the 200 km by 2,000 km orbital regime by the U.S. Space Surveillance Network, a debris population of up to 300,000 objects larger than 4 mm appears to have been generated, based upon special radar observations. The debris cloud presented an immediate threat to many resident space objects, such as the Hubble Space Telescope, which resided in an orbit just 25 km below the breakup altitude. Special analyses were required to ensure the safety of the STS-82 Hubble Space Telescope servicing mission in February 1997. This paper describes the activities undertaken at the National Aeronautics and Space Administration Lyndon B. Johnson Space Center to characterize the near-term and far-term hazard of the debris cloud to manned and robotic spacecraft and to investigate the probable cause of the accident. The role of composite materials in the vehicle may have led to the creation of a much larger number of debris than would have been expected from a more conventional upper stage. To avoid a repetition of the incident, the Hydrazine Auxiliary Propulsion System upper stage was modified before its next launch, and additional passivation measures were adopted. This fragmentation event represents a textbook case for the hazards posed by satellite breakups and how fragmentation potential can be reduced without significantly affecting the capability of the vehicle.

  2. Aminoindazole PDK1 Inhibitors: A Case Study in Fragment-Based Drug Discovery

    SciTech Connect

    Medina, Jesus R.; Blackledge, Charles W.; Heerding, Dirk A.; Campobasso, Nino; Ward, Paris; Briand, Jacques; Wright, Lois; Axten, Jeffrey M.

    2012-05-29

    Fragment screening of phosphoinositide-dependent kinase-1 (PDK1) in a biochemical kinase assay afforded hits that were characterized and prioritized based on ligand efficiency and binding interactions with PDK1 as determined by NMR. Subsequent crystallography and follow-up screening led to the discovery of aminoindazole 19, a potent leadlike PDK1 inhibitor with high ligand efficiency. Well-defined structure-activity relationships and protein crystallography provide a basis for further elaboration and optimization of 19 as a PDK1 inhibitor.

  3. Comparative study of analgesic potency of ACTH4-10 fragment and its analog semax.

    PubMed

    Ivanova, D M; Levitskaya, N G; Andreeva, L A; Kamenskii, A A; Myasoedov, N F

    2007-01-01

    The effects of ACTH4-10 fragment and its analog semax on nociception were examined on various animal models. ACTH4-10 in a dose of 0.5 mg/kg decreased nociception in rats during hindpaw compression test and in mice subjected to acetic acid writhing test. Lower doses of ACTH4-10 produced no analgesic effect. Semax (0.015-0.500 mg/kg) decreased pain sensitivity in all experimental models. Hence, the substitution of three C-terminal amino acid residues in ACTH4-10 for Pro-Gly-Pro sequence augmented the analgesic potency of the peptide after its peripheral injection.

  4. The cage fragmentation of doubly ionized norbornane: A Born-Oppenheimer molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Knippenberg, S.; Hajgató, B.

    2013-10-01

    Results are reported of Born-Oppenheimer molecular dynamics calculations performed on the singlet dication of norbornane, starting from the neutral ground state geometry. Intramolecular rearrangements and charge dissociation processes, which probably take place in the innermost valence ionization spectrum, are discussed and an analysis by means of natural bond orders and Wiberg bond indices has been performed. The outcome of these simulations and the observed cage fragmentation might explain a tremendous rise of electron-impact (e, 2e) ionization cross sections of norbornane at electron binding energies around the double-ionization threshold.

  5. [Electromagnetic studies of nuclear structure and reactions]. Progress summary

    SciTech Connect

    Not Available

    1992-12-31

    The experimental goals are focused on developing an understanding of strong interactions and the structure of hadronic systems by determination of the electromagnetic response; these goals will be accomplished through coincidence detection of final states. Nuclear modeling objectives are to organize and interpret the data through a consistent description of a broad spectrum of reaction observables; calculations are performed in a nonrelativistic diagrammatic framework as well as a relativistic QHD approach. Work is described according to the following arrangement: direct knockout reactions (completion of {sup 16}O(e,e{prime}p), {sup 12}C(e,e{prime}pp) progress, large acceptance detector physics simulations), giant resonance studies (intermediate-energy experiments with solid-state detectors, the third response function in {sup 12}C(e,e{prime}p{sub 0}) and {sup 16}O(e,e{prime}p{sub 0}), comparison of the {sup 12}C(e, e{prime}p{sub 0}) and {sup 16}O(e,e{prime}p{sub 3}) reactions, quadrupole strength in the {sup 16}O(e,e{prime}{alpha}{sub 0}) reaction, quadrupole strength in the {sup 12}C(e,e{prime}{alpha}) reaction, analysis of the {sup 12}C(e,e{prime}p{sub 1}) and {sup 16}O(e,e{prime}p{sub 3}) angular distributions, analysis of the {sup 40}Ca(e,e{prime}x) reaction at low q, analysis of the higher-q {sup 12}C(e,e{prime}x) data from Bates), models of nuclear structure (experimental work, Hartree-Fock calculations, phonon excitations in spherical nuclei, shell model calculations, variational methods for relativistic fields), and instrumentation development efforts (developments at CEBAF, CLAS contracts, BLAST developments).

  6. Reaction mechanism studies of unsaturated molecules using photofragment translational spectroscopy

    SciTech Connect

    Longfellow, C.A. |

    1996-05-01

    A number of molecules have been studied using the technique of photofragment translational spectroscopy. In Chapter One a brief introduction to the experimental technique is given. In Chapter Two the infrared multiphoton dissociation (IRMPD) of acetic acid is discussed. Carbon dioxide and methane were observed for the first time as products from dissociation under collisionless conditions. Chapter Three relates an IRMPD experiment of hexafluoropropene. The predominant channel produces CFCF{sub 3} or C{sub 2}F{sub 4} and CF{sub 2}, with the heavier species undergoing further dissociation to two CF{sub 2} fragments. In Chapter Four the ultraviolet (UV) dissociation of hexafluoropropene is investigated. Chapter Five explores the IRMPD of octafluoro-1-butene and octafluoro-2-butene.

  7. Mechanisms of fragmentation of cationic peptide ions

    NASA Astrophysics Data System (ADS)

    Zhao, Hong; Adams, Jeanette

    1993-06-01

    Fragmentation mechanisms for formation of several commonly occurring product ions in high-energy collision-induced induced decomposition spectra of either (M + Cat2+ - H)+ ions of peptides cationized with alkaline earth metal ions, (M + Ca+)+ ions cationized with alkali metal ions, or (M + H)+ ions are evaluated by using deuterium-labelled peptides. The different sources of hydrogen transferred in the reactions are identified. Our study supports some previously proposed mechanisms but also provides evidence for others.

  8. A dynamical study of the Si(+) + H(2)O reaction.

    PubMed

    Flores, Jesús R

    2007-11-01

    A dynamical study of the Si(+) + H(2)O reaction has been carried out by means of a quasiclassical trajectory method that decomposes the reaction into a capture step, for which an accurate analytical potential is employed, and an unimolecular step, in which the evolution of the collision complex is studied through a direct dynamics BHandHLYP/6-31G(d,p) method. The capture rate coefficient has been computed for thermal conditions corresponding to temperatures ranging from 50 to 1000 K. It is concluded that the main reason why the reaction rate is about 10 times smaller than the capture rate (at T = 298 K) is the topology of the potential energy surface of the ground state. It is also concluded that the ratio between the rates of product and reactant generation from the collision complex decreases quite steeply with increasing temperature, and therefore, the reaction rate decreases even more sharply. Exciting the stretching normal modes of water substantially increases that ratio, and moderate rotational excitation does not appear to have a relevant effect. The collision complex is always initially SiOH(2)(+), but in some trajectories, it becomes HSiOH(+), which generates the products, although the former species is the main intermediate.

  9. Ionization and fragmentation of complex molecules studied with a density functional theory based approach

    NASA Astrophysics Data System (ADS)

    Kirchner, Tom

    2013-05-01

    Ion-impact induced ionization and fragmentation of complex molecules have important applications in many branches of science. If the molecule is H2O an obvious topic to address is the radiobiological relevance of these processes, e.g. in the context of hadron therapy, to name just one example. From a more fundamental physics viewpoint ion-molecule collision systems constitute interesting many-body systems, whose analysis poses challenges to both experimentalists and theorists. This talk will describe a theoretical approach to ion-molecule collisions, which is based on density functional theory to describe the nonperturbative electron dynamics. The basis generator method applied in the past successfully to ion-atom collisions is adapted to deal with the multi-center problem one faces when one considers molecular targets. Cross sections for single- and multiple-electron processes (capture and transfer to the continuum) are obtained directly from solving time-dependent Kohn-Sham-type orbital equations and using a Slater determinant based analysis. Fragmentation yields are predicted on the basis of a semi-phenomenological model which uses the calculated cross sections as input. Results will be presented for various ions impacting on water molecules in the energy range of 10-5000 keV/amu and compared with experimental data and previous theoretical calculations where available. First applications of the model to collisions involving CH4 molecules will also be discussed. This work has been supported by SHARCNET and NSERC Canada.

  10. Hydration of ligands of influenza virus neuraminidase studied by the fragment molecular orbital method.

    PubMed

    Tokuda, Kana; Watanabe, Chiduru; Okiyama, Yoshio; Mochizuki, Yuji; Fukuzawa, Kaori; Komeiji, Yuto

    2016-09-01

    The fragment molecular orbital (FMO) method was applied to quantum chemical calculations of neuramic acid, the natural substrate of the influenza virus neuraminidase, and two of its competitive inhibitors, Oseltamivir (Tamiful(®)) and Zanamivir (Relenza(®)), to investigate their hydrated structures and energetics. Each of the three ligands was immersed in an explicit water solvent, geometry-optimized by classical MM and QM/MM methods, and subjected to FMO calculations with 2-, 3-, and 4-body corrections under several fragmentation options. The important findings were that QM/MM optimization was preferable to obtain reliable hydrated structures of the ligands, that the 3-body correction was important for quantitative evaluation of the solvation energy, and that the dehydration effect was most remarkable near the hydrophobic sections of the ligands. In addition, the hydration energy calculated by the explicit solvent was compared with the hydration free energy calculated by the implicit solvent via the Poisson-Boltzmann equation, and the two showed a fairly good correlation. These findings will serve as useful information for rapid drug design.

  11. Lamellar spacing of photosystem II membrane fragments upon dehydration studied by neutron membrane diffraction

    NASA Astrophysics Data System (ADS)

    Pieper, Jörg; Rusevich, Leonid; Hauß, Thomas; Renger, Gernot

    2016-02-01

    The effect of dehydration on the lamellar spacing of photosystem II (PS II) membrane fragments from spinach has been investigated using neutron membrane diffraction at room temperature. The diffraction data reveal a major peak at a scattering vector Q of 0.049 Å-1 at a relative humidity (r.h.) of 90% corresponding to a repeat distance D of about 129 Å. Upon dehydration to 44% r.h., this peak shifts to about 0.060 Å-1 corresponding to a distance of 104.7±2.5 Å. Within experimental error, the latter repeat distance remains almost the same at hydration levels below 44% r.h. indicating that most of the hydration water is removed. This result is consistent with the earlier finding that hydration-induced conformational protein motions in PS II membrane fragments are observed above 44% r.h. and correlated with the onset electron transfer in PS II (Pieper et al. 2008, Eur. Biophys. J. 37: 657-663).

  12. Lamellar spacing of photosystem II membrane fragments upon dehydration studied by neutron membrane diffraction

    NASA Astrophysics Data System (ADS)

    Pieper, Jörg; Rusevich, Leonid; Hauß, Thomas; Renger, Gernot

    2015-12-01

    The effect of dehydration on the lamellar spacing of photosystem II (PS II) membrane fragments from spinach has been investigated using neutron membrane diffraction at room temperature. The diffraction data reveal a major peak at a scattering vector Q of 0.049 Å-1 at a relative humidity (r.h.) of 90% corresponding to a repeat distance D of about 129 Å. Upon dehydration to 44% r.h., this peak shifts to about 0.060 Å-1 corresponding to a distance of 104.7±2.5 Å. Within experimental error, the latter repeat distance remains almost the same at hydration levels below 44% r.h. indicating that most of the hydration water is removed. This result is consistent with the earlier finding that hydration-induced conformational protein motions in PS II membrane fragments are observed above 44% r.h. and correlated with the onset electron transfer in PS II (Pieper et al. 2008, Eur. Biophys. J. 37: 657-663).

  13. An “Aprotic” Tamao Oxidation/syn-Selective Tautomerization Reaction for the Efficient Synthesis of the C(1)–C(9) Fragment of Fludelone

    PubMed Central

    Harrison, Tyler J.; Rabbat, Philippe M. A.; Leighton, James L.

    2012-01-01

    An efficient synthesis of the C(1)–C(9) fragment of fludelone has been developed. The key step is a tandem silylformylation-crotylsilylation/Tamao oxidation sequence that establishes the C(5) ketone, the C(6), C(7), and C(8) stereocenters, and the C(9) alkene in a single operation from a readily accessed starting material. The stereochemical outcome at C(6) depends critically on the development of an “aprotic” Tamao oxidation, which leads to a reversal in the intrinsic diastereoselectivity observed using “standard” Tamao oxidation conditions. PMID:22950417

  14. Fragment molecular orbital study of the cAMP-dependent protein kinase catalyzed phosphoryl transfer: a comparison with the differential transition state stabilization method.

    PubMed

    Öberg, H; Brinck, T

    2016-06-01

    The importance of key residues to the activity of the cAMP-dependent protein kinase catalyzed phosphoryl transfer and to the stabilization of the transition state of the reaction has been investigated by means of the fragment molecular orbital (FMO) method. To evaluate the accuracy of the method and its capability of fragmenting covalent bonds, we have compared stabilization energies due to the interactions between individual residues and the reaction center to results obtained with the differential transition state stabilization method (Szarek, et al., J. Phys. Chem. B, 2008, 112, 11819-11826) and observe, despite a size difference in the fragment describing the reaction center, near-quantitative agreement. We have also computed deletion energies to investigate the effect of virtual deletion of key residues on the activation energy. These results are consistent with the stabilization energies and yield additional information as they clearly capture the effect of secondary interactions, i.e. interactions in the second coordination layer of the reaction center. We find that using FMO to calculate deletion energies is a powerful and time efficient approach to analyze the importance of key residues to the activity of an enzyme catalyzed reaction.

  15. Molecular beams studies of the energetics and dynamics of elementary chemical reactions

    SciTech Connect

    Hayden, C.C.

    1982-05-01

    Quantum mechanical effects on the angular distribution of HF products from the F + H/sub 2/ reaction were studied using crossed atomic and molecular beams with a rotatable mass spectrometer detector and time-of-flight velocity analysis. Measurement of the singlet-triplet splitting of CH/sub 2/ from the recoil velocities of fragments from ketene photodissociation in a molecular beam is also reported. Partial center-of-mass angular distributions, and velocity flux contour maps have been derived for individual vibrational states of the HF product from the F + H/sub 2/ reaction at collision energies of 2 and 3 kcal/mole. The center-of-mass distributions were obtained by analysis of laboratory angular and time-of-flight measurements of the reactive scattering. The results are consistent with recent three dimensional quantum mechanical scattering calculations, which predict that resonance effects should appear in the product angular distributions in this energy range. The photofragmentation of ketene in a molecular beam was used to measure the singlet-triplet splitting in CH/sub 2/. A rare gas halide excimer laser operating at 351 nm (XeF) and 308 nm (XeCl) dissociated the ketene. Time-of-flight measurements of the fragment velocities allowed determination of the energetics of the dissociation. The /sup 1/A/sub 1/ - /sup 3/B/sub 1/ splitting in CH/sub 2/ was found to be 8.5 +- 0.8 kcal/mole. This agrees with many experimental results, but not with the value of 19.5 kcal/mole derived from recent photodetachment experiments on CH/sub 2//sup -/.

  16. A comparative study on genetic effects of artificial and natural habitat fragmentation on Loropetalum chinense (Hamamelidaceae) in Southeast China

    PubMed Central

    Yuan, N; Comes, H P; Cao, Y N; Guo, R; Zhang, Y H; Qiu, Y X

    2015-01-01

    Elucidating the demographic and landscape features that determine the genetic effects of habitat fragmentation has become fundamental to research in conservation and evolutionary biology. Land-bridge islands provide ideal study areas for investigating the genetic effects of habitat fragmentation at different temporal and spatial scales. In this context, we compared patterns of nuclear microsatellite variation between insular populations of a shrub of evergreen broad-leaved forest, Loropetalum chinense, from the artificially created Thousand-Island Lake (TIL) and the Holocene-dated Zhoushan Archipelago of Southeast China. Populations from the TIL region harboured higher levels of genetic diversity than those from the Zhoushan Archipelago, but these differences were not significant. There was no correlation between genetic diversity and most island features, excepting a negative effect of mainland–island distance on allelic richness and expected heterozygosity in the Zhoushan Archipelago. In general, levels of gene flow among island populations were moderate to high, and tests of alternative models of population history strongly favoured a gene flow-drift model over a pure drift model in each region. In sum, our results showed no obvious genetic effects of habitat fragmentation due to recent (artificial) or past (natural) island formation. Rather, they highlight the importance of gene flow (most likely via seed) in maintaining genetic variation and preventing inter-population differentiation in the face of habitat ‘insularization' at different temporal and spatial scales. PMID:25515015

  17. A comparative study on genetic effects of artificial and natural habitat fragmentation on Loropetalum chinense (Hamamelidaceae) in Southeast China.

    PubMed

    Yuan, N; Comes, H P; Cao, Y N; Guo, R; Zhang, Y H; Qiu, Y X

    2015-06-01

    Elucidating the demographic and landscape features that determine the genetic effects of habitat fragmentation has become fundamental to research in conservation and evolutionary biology. Land-bridge islands provide ideal study areas for investigating the genetic effects of habitat fragmentation at different temporal and spatial scales. In this context, we compared patterns of nuclear microsatellite variation between insular populations of a shrub of evergreen broad-leaved forest, Loropetalum chinense, from the artificially created Thousand-Island Lake (TIL) and the Holocene-dated Zhoushan Archipelago of Southeast China. Populations from the TIL region harboured higher levels of genetic diversity than those from the Zhoushan Archipelago, but these differences were not significant. There was no correlation between genetic diversity and most island features, excepting a negative effect of mainland-island distance on allelic richness and expected heterozygosity in the Zhoushan Archipelago. In general, levels of gene flow among island populations were moderate to high, and tests of alternative models of population history strongly favoured a gene flow-drift model over a pure drift model in each region. In sum, our results showed no obvious genetic effects of habitat fragmentation due to recent (artificial) or past (natural) island formation. Rather, they highlight the importance of gene flow (most likely via seed) in maintaining genetic variation and preventing inter-population differentiation in the face of habitat 'insularization' at different temporal and spatial scales.

  18. Distributions of {beta}{sup +} decayed nuclei generated in the CH{sub 2} and H{sub 2}O targets by the target nuclear fragment reaction using therapeutic MONO and SOBP proton beam

    SciTech Connect

    Nishio, Teiji; Sato, Takashi; Kitamura, Hideaki; Murakami, Koji; Ogino, Takashi

    2005-04-01

    In proton radiotherapy, the irradiation dose can be concentrated on a tumor. To use this radiotherapy efficiently in the clinical field, it is necessary to evaluate the proton-irradiated area and condition. The proton-irradiated area can be confirmed by coincidence detection of pair annihilation gamma rays from {beta}{sup +} decayed nuclei generated by target nuclear fragment reaction of irradiated proton nuclei and nuclei in the irradiation target. In this study, we performed experiments of proton irradiation to a polyethylene (PE:CH{sub 2}) target containing {sup 12}C nuclei, which is a major component of the human body, and a gelatinous water (H{sub 2}O) target containing {sup 16}O nuclei at different proton irradiation energy levels under different beam conditions of mono-energetic Bragg peak and spread-out Bragg peak. The distribution of the activity in the target after proton irradiation was measured by a positron emission tomography (PET) apparatus, and compared with the calculated distribution. The temporal dependence of the activity distribution during the period between the completion of proton irradiation and the start of measurement by the PET apparatus was examined. The activity by clinical proton irradiation was 3 kB/cc in the PE target and 13 kB/cc in the water target, indicating that the intensity was sufficient for the evaluation of the distribution. The range of the activity distribution against the physical range was short (several millimeter water equivalent length), indicating the presence of target dependence. The range difference in the water target was slightly large with time dependence until the start of measurement. The difference of the lateral widths with full width half at maximum in the distributions of the measured irradiated dose and activity was within 1 mm.

  19. Fragmentation of Allylmethylsulfide by Chemical Ionization: Dependence on Humidity and Inhibiting Role of Water

    PubMed Central

    2013-01-01

    We report on a previously unknown reaction mechanism involving water in the fragmentation reaction following chemical ionization. This result stems from a study presented here on the humidity-dependent and energy-dependent endoergic fragmentation of allyl methyl sulfide (AMS) upon protonation in a proton transfer reaction-mass spectrometer (PTR-MS). The fragmentation pathways were studied with experimental (PTR-MS) and quantum chemical methods (polarizable continuum model (PCM), microhydration, studied at the MP2/6-311+G(3df,2p)//MP2/6-31G(d,p) level of theory). We report in detail on the energy profiles, reaction mechanisms, and proton affinities (G4MP2 calculations). In the discovered reaction mechanism, water reduces the fragmentation of protonated species in chemical ionization. It does so by direct interaction with the protonated species via covalent binding (C3H5+) or via association (AMS·H+). This stabilizes intermediate complexes and thus overall increases the activation energy for fragmentation. Water thereby acts as a reusable inhibitor (anticatalyst) in chemical ionization. Moreover, according to the quantum chemical (QC) results, when water is present in abundance it has the opposite effect and enhances fragmentation. The underlying reason is a concentration-dependent change in the reaction principle from active inhibition of fragmentation to solvation, which then enhances fragmentation. This amphoteric behavior of water is found for the fragmentation of C3H5+ to C3H3+, and similarly for the fragmentation of AMS·H+ to C3H5+. The results support humidity-dependent quantification efforts for PTR-MS and chemical ionization mass spectrometry (CIMS). Moreover, the results should allow for a better understanding of ion-chemistry in the presence of water. PMID:23682687

  20. Choline acetyltransferase: further studies on the reverse reaction

    SciTech Connect

    Hsu, L.L.; Chao, L.P.

    1982-01-01

    In order to further characterize the reaction mechanism of brain ChAc in its purified form, we have investigated the reverse reaction of ChAc in terms of pH optimum, salt effects, and substrate kinetics using a radiochemical assay. We directly measured the reaction product acetylcoenzyme A which was separated from the substrate ACh by a cation exchange column. Dowex 50W-X8 (Na+ form). The reverse reaction of ChAc was linear with incubation time up to 40 minutes, and with enzyme protein concentration up to 5 micrograms. It had a pH optimum at 7.0. At 0.22 M the monovalent chloride and bromide salts activated the reverse ChAc activity by 23-47% but the fluoride and iodide salts inhibited the reverse enzyme activity by 10-30%. Kinetic studies in the absence of salt showed that KACh was 0.62 +/- 0.06 mM, KCoA . SH was 12.68 +/- 1.21 microM, and Vmax was 11.6 +/- 1.0 nmol AcCoA/mg protein/min. These data are in disagreement with the values reported on partially purified ChAc from bovine brain by Glover and Potter (1971) and Hersh (1980). This indicates that further investigations are necessary to clarify or resolve these differences.

  1. Raman spectroscopic studies of gas/aerosol chemical reactions

    SciTech Connect

    Aardahl, C.L.; Davis, E.J.

    1995-12-31

    Reactions between sorbent particles and SO{sub 2} can be used to reduce atmospheric pollution either by {open_quotes}dry scrubbing{close_quotes} or {open_quotes}wet scrubbing{close_quotes} processes. This paper reports Raman spectroscopy results for single electrodynamically levitated droplets of NaOH reacting with SO{sub 2} and studies of the dehydration reactions of some hygroscopic salt species. The NaOH/SO{sub 2} reaction products and the liquid or solid state of the products are shown to depend on the gas phase SO{sub 2} concentration. Deliquesced particles of NaOH exhibit enhanced light scattering intensities associated with morphological resonances of the incident laser light, but crystalline materials show no such resonances. Raman-active hygroscopic salts exhibit bond frequencies characteristic of the stretching vibrations of the anionic group, but these frequencies are different in the presence of water because hydrogen bonding changes the bond force. This allows efficient tracking of the dehydration reactions in hygroscopic aerosols by Raman spectroscopy as the intensities of the two different modes are related to the degree of dehydration in the particle.

  2. Iron oxide mineral-water interface reactions studied by AFM

    SciTech Connect

    Hawley, M.E.; Rogers, P.S.Z.

    1994-07-01

    Natural iron mineral surfaces have been examined in air by atomic force (AFM) and scanning tunneling (STM) microscopies. A number of different surface features were found to be characteristic of the native surface. Even surfaces freshly exposed by crushing larger crystals were found to have a pebbly surface texture caused by the presence of thin coatings of what might be surface precipitates. This finding is interpreted as evidence for previous exposure to water, probably through an extensive network of microfractures. Surface reactions on the goethite crystals were studied by AFM at size resolutions ranging from microns to atomic resolution before, during, and after reaction with distilled water and 0.lN HCl. Immediate and extensive surface reconfiguration occurred on contact with water. In one case, after equilibration with water for 3 days, surface reprecipitation, etching and pitting were observed. Atomic resolution images taken under water were found to be disordered. The result of surface reaction was generally to increase the surface area substantially through the extension of surface platelet arrays, present prior to reaction. This work is being done in support of the site characterization project at Yucca Mountain.

  3. Molecular-dynamics study of detonation. II. The reaction mechanism

    NASA Astrophysics Data System (ADS)

    Rice, Betsy M.; Mattson, William; Grosh, John; Trevino, S. F.

    1996-01-01

    In this work, we investigate mechanisms of chemical reactions that sustain an unsupported detonation. The chemical model of an energetic crystal used in this study consists of heteronuclear diatomic molecules that, at ambient pressure, dissociate endothermically. Subsequent association of the products to form homonuclear diatomic molecules provides the energy release that sustains the detonation. A many-body interaction is used to simulate changes in the electronic bonding as a function of local atomic environment. The consequence of the many-body interaction in this model is that the intramolecular bond is weakened with increasing density. The mechanism of the reaction for this model was extracted by investigating the details of the molecular properties in the reaction zone with two-dimensional molecular dynamics. The mechanism for the initiation of the reaction in this model is pressure-induced atomization. There was no evidence of excitation of vibrational modes to dissociative states. This particular result is directly attributable to the functional form and choice of parameters for this model, but might also have more general applicability.

  4. Inertial confinement fusion reaction chamber and power conversion system study

    SciTech Connect

    Maya, I.; Schultz, K.R.; Battaglia, J.M.; Buksa, J.J.; Creedson, R.L.; Erlandson, O.D.; Levine, H.E.; Roelant, D.F.; Sanchez, H.W.; Schrader, S.A.

    1984-09-01

    GA Technologies has developed a conceptual ICF reactor system based on the Cascade rotating-bed reaction chamber concept. Unique features of the system design include the use of low activation SiC in a reaction chamber constructed of box-shaped tiles held together in compression by prestressing tendons to the vacuum chamber. Circulating Li/sub 2/O granules serve as the tritium breeding and energy transport material, cascading down the sides of the reaction chamber to the power conversion system. The total tritium inventory of the system is 6 kg; tritium recovery is accomplished directly from the granules via the vacuum system. A system for centrifugal throw transport of the hot Li/sub 2/O granules from the reaction chamber to the power conversion system has been developed. A number of issues were evaluated during the course of this study. These include the response of first-layer granules to the intense microexplosion surface heat flux, cost effective fabrication of Li/sub 2/O granules, tritium inventory and recovery issues, the thermodynamics of solids-flow options, vacuum versus helium-medium heat transfer, and the tradeoffs of capital cost versus efficiency for alternate heat exchange and power conversion system option. The resultant design options appear to be economically competitive, safe, and environmentally attractive.

  5. A Study of Charge Transport: Correlated Energetic Disorder in Organic Semiconductors, and the Fragment Hamiltonian

    NASA Astrophysics Data System (ADS)

    Allen, Jonathan Robert

    This dissertation details work done on two different descriptions of charge transport. The first topic is energetic disorder in organic semiconductors, and its effect on charge transport. This is motivated primarily by solar cells, which can be broadly classified as either inorganic or organic. The inorganic class of solar cells is older, and more well-developed, with the most common type being constructed from crystalline silicon. The large silicon crystals required for these cells are expensive to manufacture, which gave rise to interest in photovoltaic cells made from much less costly organic polymers. These organic materials are also less efficient than their silicon counterparts, due to a large degree of spatial and energetic disorder. In this document, the sources and structure of energetic disorder in organic semiconductors are explored, with an emphasis on spatial correlations in energetic disorder. In order for an organic photovoltaic device to function, there must be photogeneration of an exciton (a bound electron-hole pair), exciton transport, exciton dissociation, and transport of the individual charges to their respective terminals. In the case of this thesis, the main focus is exciton dissociation. The effects of correlation on exciton dissociation are examined through computer simulation, and compared to the theory and simulations of previous researchers. We conclude that energetic disorder in organic semiconductors is spatially correlated, and that this correlation improves the ability of excitons to dissociate. The second topic of this dissertation is the Fragment Hamiltonian model. This is a model currently in development as a means of describing charge transport across a range of systems. Currently there are many different systems which exhibit various charge transport behaviors, which are described by several different models. The overarching goal of the Fragment Hamiltonian model is to construct a description of charge transport which

  6. Study on astrophysical reactions using low-energy RI beams

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hidetoshi

    2009-10-01

    In recent years, low-energy RI beams can be produced in a good intensity and they have been used for studying many astrophysical reactions. One of the facilities producing low-energy RI beams is CRIB (CNS Radio-Isotope Beam separator) [1,2], an RI-beam separator of Center for Nuclear Study, University of Tokyo. Taking CRIB as an example, recent improvements on the RI-beam production and experimental results on astrophysical studies are presented. Several experimental approaches have been taken for the studies on astrophysical reactions.The feature of each method are discussed based on real measurements performed at CRIB. One is the direct method, applied for measurements of reactions such as (α,p) [3]. Another is the measurement of proton/alpha resonance scattering using the thick target method in inverse kinematics, by which we can obtain information on the resonances relevant in astrophysical reactions [4,5]. A recent fruitful result was from a measurement of proton resonance scattering using a ^7Be beam [5]. The energy level structure of ^8B, revealed by the experiment, is especially of interest as it is related with the ^7Be(p,γ) ^8B reaction, responsible for the production of ^8B neutrinos in the sun. We successfully determined parameters of resonances in ^8B below 6.7 MeV, which may affect the ^7Be(p,γ)^8B reaction rate at the solar temparature. Indirect methods, such as ANC and the Trojan Horse Method, were also used in some of the measurements.[4pt] [1] S. Kubono et al., Eur. Phys. J. A13 (2002) 217.[0pt] [2] Y. Yanagisawa et al., Nucl. Instrum. Meth. Phys. Res., Sect. A 539 (2005) 74.[0pt] [3] M. Notani et al., Nucl. Phys. A 764 (2004) 113c.[0pt] [4] T. Teranishi et al., Phys. Lett. B 650 (2007) 129.[0pt] [5] H. Yamaguchi et al., Phys. Lett. B 672 (2009) 230.

  7. Electrochemical and spectroscopic studies of fuel cell reactions

    NASA Astrophysics Data System (ADS)

    Shao, Minhua

    Fuel cells, especially proton exchange membrane fuel cells (PEMFCs) are expected soon to become a major source of clean energy. However, the sluggish kinetics of the fuel cell reactions, i.e., the fuel oxidation and oxygen reduction, hinders the wide-spread application of PEMFCs. These problems prompted our studies to focus on elucidating the nature of the reaction intermediates during the oxidation of fuels and the reduction of oxygen on electrocatalysts, and understanding the mechanisms of these reactions. The results from these studies will provide basic information for designing new electrocatalysts. In this dissertation, the oxidation reactions of ethanol and dimethyl ether (DME) on Pt were investigated by the surface enhanced infrared absorption spectroscopy with an attenuated total reflection configuration (ATR-SEIRAS). Various reaction intermediates were detected and their electrochemical behaviors were studied. We also benefited from advantages of the ATR-SEIRAS technique and observed superoxide anion (O2-) and hydrogen peroxide anion (H2-) as the intermediates in the oxygen reduction reaction (ORR) on Pt and Au electrodes for the first time. The other main goal of this study is design of new electrocatalysts for ORR with low cost and high activity. Two novel electrocatalysts were developed. One is Pt monolayer electrocatalysts consisting of a Pt monolayer formed by a red-ox replacement of the Cu monolayer by Pt atoms on non-noble metal-noble metal core-shell nanoparticles. In such catalyst, the total noble mass activity of the catalyst was 2--6 times larger that of commercial Pt catalyst. Another way of lowering the cost of catalysts and enhancing the ORR activity involves alloying less expensive noble metals with other non-noble elements. In this dissertation, the nano-structured Pd based alloy electrocatalysts have been explored. The results showed that their ORR activities surpass that of commercial Pt. The density functional theory (DFT) calculations

  8. Crossed-beam studies of the dynamics of radical reactions

    SciTech Connect

    Liu, K.

    1993-12-01

    The objective of this program is to characterize the detailed dynamics of elementary radical reactions and to provide a better understanding of radical reactivity in general. The radical beam is typically generated by a laser photolysis method. After colliding with the reacting molecule in a crossed-beam apparatus, the reaction product state distribution is interrogated by laser spectroscopic techniques. Several radicals of combustion significance, such as O, CH, OH, CN and NCO have been successfully generated and their collisional behavior at the state-to-state integral cross section level of detail has been studied in this manner. During the past year, the detection system has been converted from LIF to REMPI schemes, and the emphasis of this program shifted to investigate the product angular distributions. Both inelastic and reactive processes have been studied.

  9. A Nuclear Reaction Analysis study of fluorine uptake in flint

    SciTech Connect

    Jin, Jian-Yue; Weathers, D. L.; Picton, F.; Hughes, B. F.; Duggan, J. L.; McDaniel, F. D.; Matteson, S.

    1999-06-10

    Nuclear Reaction Analysis (NRA) using the {sup 19}F(p,{alpha}{gamma}){sup 16}O resonance reaction is a powerful method of fluorine depth profiling. We have used this method to study the fluorine uptake phenomenon in mineral flint, which could potentially develop into a method of dating archeological flint artifacts. Flint samples cut with a rock saw were immersed in aqueous fluoride solutions for different times for the uptake study. The results suggest that fluorine uptake is not a simple phenomenon, but rather a combination of several simultaneous processes. Fluorine surface adsorption appears to play an important role in developing the fluorine profiles. The surface adsorption was affected by several parameters such as pH value and fluorine concentration in the solution, among others. The problem of surface charging for the insulator materials during ion bombardment is also reported.

  10. Proton Transfer Reactions Studied Using the VANDLE Neutron Detector Array

    NASA Astrophysics Data System (ADS)

    Thornsberry, C. R.; Burcher, S.; Gryzwacz, R.; Jones, K. L.; Paulauskas, S. V.; Smith, K.; Vostinar, M.; Allen, J.; Bardayan, D. W.; Blankstein, D.; Deboer, J.; Hall, M.; O'Malley, P. D.; Reingold, C.; Tan, W.; Cizewski, J. A.; Lepailleur, A.; Walter, D.; Febbraro, M.; Pain, S. D.; Marley, S. T.

    2016-09-01

    Proton transfer reactions, such as (d,n), are powerful tools for the study of single particle proton states of exotic nuclei. Measuring the outgoing neutron allows for the extraction of spectroscopic information from the recoil nucleus. With the development of new radioactive ion beam facilities, such as FRIB in the U.S., comes the need for new tools for the study of reactions involving radioactive nuclei. Neutron detectors, such as VANDLE, are sensitive to gamma rays in addition to neutrons. This results in high background rates for measurements with high external trigger rates. The use of discriminating recoil particle detectors, such as phoswich detectors, allow for the selection of a clean recoil tag by separating the recoil nucleus of interest from unreacted RIB components. Developments of low energy proton transfer measurements in inverse kinematics and recent (d,n) results will be presented. This work supported in part by the U.S. Department of Energy and the National Science Foundation.

  11. Atmospheric Chemistry: Laboratory Studies of Kinetics of Important Reactions.

    NASA Astrophysics Data System (ADS)

    Smith, S. J.

    Available from UMI in association with The British Library. Requires signed TDF. This thesis describes the experiments to measure the rate constants for some reactions of the atmospherically important nitrate radical (NO_3) using the discharge-flow technique. The nitrate radical was monitored by optical absorption at lambda = 662 nm. The reactions of NO_3 with some stable organic and inorganic substrates are reported. The temperature dependences of some of the rate constants have also been determined (298 < T < 523 K). In most cases, computer simulation was used to extract the rate constant for the primary process because the time-dependent behaviour of (NO_3) was affected by secondary reactions of NO_3 with products of the primary interaction. The Arrhenius parameter in parentheses (E _{rm a}/kJ mol^ {-1}, A/cm^3 molecule ^{-1}s^ {-1} respectively) for the following reactions have been determined: ethane (37, 6.7 times 10^{-12}), ethylene (25.8, 6.3 times 10^ {-12}), CH_3OH (21.3, 1.2 times 10^ {-12}), CHCiota_3 (23.4, 8.6 times 10 ^{-13}) and HCl (27.7, 4 times 10^{-12}). The activation energies for the reactions studied between NO_3 and some alkynes are represented well by the value 25 +/- 3 kJ mol^{-1} and the corresponding pre-exponential factors (expressed as ln(10 ^{13}A/cm^3 molecule^{-1}s ^{-1}) are as follows: C_2H_2 (1.6 +/- 1.4), C_3H _4 (5.0 +/- 1.4), 1-C_4H_6 (5.8 +/- 1.0), 1-C_5 H_8 (5.7 +/- 0.6) and 1-C_6H _{10} (4.5 +/- 0.4). Some reactions were studied at room temperature _3(298 +/- 2 K) only and the rate constants found (in units of cm ^3 molecule^{ -1}s^{-1}) are: buta-1,3-diene (1.8 times 10 ^{-13}), isobutene (2.8 times 10^{-13 }), HBr (1.3 times 10 ^{-15}) and hex-2-yne (3.0 times 10^{-14 }). Non-Arrhenius behaviour was found in the reactions of NO_3 with n-butane, isobutane and propene. The empirical variation of these rate constants with temperature is well represented by the three parameter expressions:. k(T) = 1.2 times 10 ^{-46}T^{11

  12. Membrane effects of N-terminal fragment of apolipoprotein A-I: a fluorescent probe study.

    PubMed

    Trusova, Valeriya; Gorbenko, Galyna; Girych, Mykhailo; Adachi, Emi; Mizuguchi, Chiharu; Sood, Rohit; Kinnunen, Paavo; Saito, Hiroyuki

    2015-03-01

    The binding of monomeric and aggregated variants of 1-83 N-terminal fragment of apolipoprotein A-I with substitution mutations G26R, G26R/W@8, G26R/W@50 and G26R/W@72 to the model lipid membranes composed of phosphatidylcholine and its mixture with cholesterol has been investigated using fluorescent probes pyrene and Laurdan. Examination of pyrene spectral behavior did not reveal any marked influence of apoA-I mutants on the hydrocarbon region of lipid bilayer. In contrast, probing the membrane effects by Laurdan revealed decrease in the probe generalized polarization in the presence of aggregated proteins. suggesting that oligomeric and fibrillar apoA-I species induce increase in hydration degree and reduction of lipid packing density in the membrane interfacial region. These findings may shed light on molecular details of amyloid cytotoxicity.

  13. Quantum mechanical/molecular mechanical study on the mechanism of the enzymatic Baeyer-Villiger reaction.

    PubMed

    Polyak, Iakov; Reetz, Manfred T; Thiel, Walter

    2012-02-08

    We report a combined quantum mechanical/molecular mechanical (QM/MM) study on the mechanism of the enzymatic Baeyer-Villiger reaction catalyzed by cyclohexanone monooxygenase (CHMO). In QM/MM geometry optimizations and reaction path calculations, density functional theory (B3LYP/TZVP) is used to describe the QM region consisting of the substrate (cyclohexanone), the isoalloxazine ring of C4a-peroxyflavin, the side chain of Arg-329, and the nicotinamide ring and the adjacent ribose of NADP(+), while the remainder of the enzyme is represented by the CHARMM force field. QM/MM molecular dynamics simulations and free energy calculations at the semiempirical OM3/CHARMM level employ the same QM/MM partitioning. According to the QM/MM calculations, the enzyme-reactant complex contains an anionic deprotonated C4a-peroxyflavin that is stabilized by strong hydrogen bonds with the Arg-329 residue and the NADP(+) cofactor. The CHMO-catalyzed reaction proceeds via a Criegee intermediate having pronounced anionic character. The initial addition reaction has to overcome an energy barrier of about 9 kcal/mol. The formed Criegee intermediate occupies a shallow minimum on the QM/MM potential energy surface and can undergo fragmentation to the lactone product by surmounting a second energy barrier of about 7 kcal/mol. The transition state for the latter migration step is the highest point on the QM/MM energy profile. Gas-phase reoptimizations of the QM region lead to higher barriers and confirm the crucial role of the Arg-329 residue and the NADP(+) cofactor for the catalytic efficiency of CHMO. QM/MM calculations for the CHMO-catalyzed oxidation of 4-methylcyclohexanone reproduce and rationalize the experimentally observed (S)-enantioselectivity for this substrate, which is governed by the conformational preferences of the corresponding Criegee intermediate and the subsequent transition state for the migration step.

  14. Theoretical study of phosphodiester hydrolysis in nucleotide pyrophosphatase/phosphodiesterase. Environmental effects on the reaction mechanism.

    PubMed

    López-Canut, Violeta; Roca, Maite; Bertrán, Juan; Moliner, Vicent; Tuñón, Iñaki

    2010-05-26

    We here present a theoretical study of the alkaline hydrolysis of methyl p-nitrophenyl phosphate (MpNPP(-)) in aqueous solution and in the active site of nucleotide pyrophosphatase/phosphodiesterase (NPP). The analysis of our simulations, carried out by means of hybrid quantum mechanics/molecular mechanics (QM/MM) methods, shows that the reaction takes place through different reaction mechanisms depending on the environment. Thus, while in aqueous solution the reaction occurs by means of an A(N)D(N) mechanism, the enzymatic process takes place through a D(N)A(N) mechanism. In the first case, we found associative transition-state (TS) structures, while in the enzyme TS structures have dissociative character. The reason for this change is rationalized in terms of the very different nature of the electrostatic interactions established in each of the environments: while the aqueous solution reduces the repulsion between the negatively charged reacting fragments, assisting their approach, the NPP active site stabilizes the charge distribution of dissociative TS structures, allowing the reaction to proceed with a significantly reduced free energy cost. Interestingly, the NPP active site is able to accommodate different substrates, and it seems that the nature of the TSs depends on their electronic characteristics. So, in the case of the MpNPP(-) substrate, the nitro group establishes hydrogen-bond interactions with water molecules and residues found in the outer part of the catalytic site, while the leaving group oxygen atom does not coordinate directly with any of the zinc atoms of the active site. If methyl phenyl phosphate is used as substrate, then the charge on the leaving group is supported to larger extent by the oxygen atom and the phenolate anion can be then coordinated to one of the two zinc atoms present in the active site.

  15. Insight into the kinetics and thermodynamics of the hydride transfer reactions between quinones and lumiflavin: a density functional theory study.

    PubMed

    Reinhardt, Clorice R; Jaglinski, Tanner C; Kastenschmidt, Ashly M; Song, Eun H; Gross, Adam K; Krause, Alyssa J; Gollmar, Jonathan M; Meise, Kristin J; Stenerson, Zachary S; Weibel, Tyler J; Dison, Andrew; Finnegan, Mackenzie R; Griesi, Daniel S; Heltne, Michael D; Hughes, Tom G; Hunt, Connor D; Jansen, Kayla A; Xiong, Adam H; Hati, Sanchita; Bhattacharyya, Sudeep

    2016-09-01

    The kinetics and equilibrium of the hydride transfer reaction between lumiflavin and a number of substituted quinones was studied using density functional theory. The impact of electron withdrawing/donating substituents on the redox potentials of quinones was studied. In addition, the role of these substituents on the kinetics of the hydride transfer reaction with lumiflavin was investigated in detail under the transition state (TS) theory assumption. The hydride transfer reactions were found to be more favorable for an electron-withdrawing substituent. The activation barrier exhibited a quadratic relationship with the driving force of these reactions as derived under the formalism of modified Marcus theory. The present study found a significant extent of electron delocalization in the TS that is stabilized by enhanced electrostatic, polarization, and exchange interactions. Analysis of geometry, bond-orders, and energetics revealed a predominant parallel (Leffler-Hammond) effect on the TS. Closer scrutiny reveals that electron-withdrawing substituents, although located on the acceptor ring, reduce the N-H bond order of the donor fragment in the precursor complex. Carried out in the gas-phase, this is the first ever report of a theoretical study of flavin's hydride transfer reactions with quinones, providing an unfiltered view of the electronic effect on the nuclear reorganization of donor-acceptor complexes.

  16. Reaction of protein chloramines with DNA and nucleosides: evidence for the formation of radicals, protein-DNA cross-links and DNA fragmentation.

    PubMed

    Hawkins, Clare L; Pattison, David I; Davies, Michael J

    2002-08-01

    Stimulated phagocyte cells produce the oxidant HOCl, via the release of the enzyme myeloperoxidase and hydrogen peroxide. HOCl is important in bacterial cell killing, but excessive or misplaced generation can damage the host tissue and may lead to the development of certain diseases such as cancer. The role of HOCl in the oxidation of isolated proteins, DNA and their components has been investigated extensively, but little work has been performed on the protein-DNA (nucleosome) complexes present in eukaryotic cell nuclei. Neither the selectivity of damage in such complexes nor the possibility of transfer of damage from the protein to DNA or vice versa, has been studied. In the present study, kinetic modelling has been employed to predict that reaction occurs predominantly with the protein and not with the DNA in the nucleosome, using molar HOCl excesses of up to 200-fold. With 50-200-fold excesses, 50-80% of the HOCl is predicted to react with histone lysine and histidine residues to yield chloramines. The yield and stability of such chloramines predicted by these modelling studies agrees well with experimental data. Decomposition of these species gives protein-derived, nitrogen-centred radicals, probably on the lysine side chains, as characterized by the EPR and spin-trapping experiments. It is shown that isolated lysine, histidine, peptide and protein chloramines can react with plasmid DNA to cause strand breaks. The protection against such damage afforded by the radical scavengers Trolox (a water-soluble alpha-tocopherol derivative) and 5,5-dimethyl-1-pyrroline-N-oxide suggests a radical-mediated process. The EPR experiments and product analyses have also provided evidence for the rapid addition of protein radicals, formed on chloramine decomposition, to pyrimidine nucleosides to give nucleobase radicals. Further evidence for the formation of such covalent cross-links has been obtained from experiments performed using (3)H-lysine and (14)C-histidine chloramines

  17. University Students' Situational Reaction Tendencies: Reflections on General Study Orientations, Learning Strategies, and Study Success

    ERIC Educational Resources Information Center

    Makinen, Jarkko; Olkinuora, Erkki

    2004-01-01

    The purpose of the study was to bridge the gap between situational and more general measures in investigating university students' studying. More precisely, the aim was to establish a connection between students' situational reaction tendencies and their general study orientations. Furthermore, situational reaction tendencies were related to the…

  18. Study of the ( μ-, e +) reaction mediated by Majorana neutrinos

    NASA Astrophysics Data System (ADS)

    Vergados, J. D.; Ericson, M.

    1982-02-01

    The exotic lepton violating ( μ-, e +) reaction has been studied in a gauge theory model which assumes the existence of a Majorana neutral lepton. In addition to the usual mechanism involving only two nucleons, the reaction mechanisms which consider a virtual Δ++ present in the nucleus or pions in flight between the interacting nucleons have also been included. The total ( μ-, e +) branching ratio was computed as a function of the various parameters of the theory. It was found to be very sensitively dependent on the mass mσ of the Majorana particle and it becomes very small for mσ > 10 GeV/ c2. The dependence of the branching ratio on the other parameters of the theory is also discussed.

  19. Direct reaction experimental studies with beams of radioactive tin ions

    SciTech Connect

    Jones, K. L. Ayres, A.; Bey, A.; Burcher, S.; Cartegni, L.; Cerizza, G.; Ahn, S.; Allmond, J. M.; Beene, J. R.; Galindo-Uribarri, A.; Liang, J. F.; Nesaraja, C. D.; Pain, S. D.; Radford, D. C.; Schmitt, K. T.; Smith, M. S.; Stracener, D. W.; Varner, R. L.; Bardayan, D. W.; Baugher, T.; and others

    2015-10-15

    The tin chain of isotopes provides a unique region in which to investigate the evolution of single-particle structure, spreading from N = 50 at {sup 100}Sn, through 10 stable isotopes and the N = 82 shell closure at {sup 132}Sn out into the r-process path. Direct reactions performed on radioactive ion beams are sensitive spectroscopic tools for studying exotic nuclei. Here we present one experiment knocking out neutrons from tin isotopes that are already neutron deficient and two reactions that add a neutron to neutron-rich {sup 130}Sn. Both techniques rely on selective particle identification and the measurement of γ rays in coincidence with charged ions. We present the goals of the two experiments and the particle identification for the channels of interest. The final results will be presented in future publications.

  20. Direct Reaction Experimental Studies with Beams of Radioactive Tin Ions

    SciTech Connect

    Jones, K. L.; Ahn, S.H.; Allmond, James M; Ayres, A.; Bardayan, Daniel W; Baugher, T.; Bazin, D.; Beene, James R; Berryman, J. S.; Bey, A.; Bingham, C. R.; Cartegni, L.; Chae, K. Y.; Gade, A.; Galindo-Uribarri, Alfredo {nmn}; Garcia-Ruiz, R.F.; Grzywacz, Robert Kazimierz; Howard, Meredith E; Kozub, R. L.; Liang, J Felix; Manning, Brett M; Matos, M.; McDaniel, S.; Miller, D.; Nesaraja, Caroline D; O'Malley, Patrick; Padgett, S; Padilla-Rodal, Elizabeth; Pain, Steven D; Pittman, S. T.; Radford, David C; Ratkiewicz, Andrew J; Schmitt, Kyle; Smith, Michael Scott; Stracener, Daniel W; Stroberg, S.; Tostevin, Jeffrey A; Varner Jr, Robert L; Weisshaar, D.; Wimmer, K.

    2015-01-01

    The tin chain of isotopes provides a unique region in which to investigate the evolution of single-particle structure, spreading from N = 50 at Sn-100, through 10 stable isotopes and the N = 82 shell closure at Sn-132 out into the r-process path. Direct reactions performed on radioactive ion beams are sensitive spectroscopic tools for studying exotic nuclei. Here we present one experiment knocking out neutrons from tin isotopes that are already neutron deficient and two reactions that add a neutron to neutron-rich Sn-130. Both techniques rely on selective particle identification and the measurement of gamma rays in coincidence with charged ions. We present the goals of the two experiments and the particle identification for the channels of interest. The final results will be presented in future publications.

  1. Density Functional Theory and Reaction Kinetics Studies of the Water–Gas Shift Reaction on Pt–Re Catalysts

    SciTech Connect

    Carrasquillo-Flores, Ronald; Gallo, Jean Marcel R.; Hahn, Konstanze; Dumesic, James A.; Mavrikakis, Manos

    2013-11-05

    Periodic, self-consistent density functional theory calculations (DFT-GGA-PW91) on Pt(111) and Pt3Re(111) surfaces, reaction kinetics measurements, and microkinetic modeling are employed to study the mechanism of the water–gas shift (WGS) reaction over Pt and Pt–Re catalysts. The values of the reaction rates and reaction orders predicted by the model are in agreement with the ones experimentally determined; the calculated apparent activation energies are matched to within 6% of the experimental values. The primary reaction pathway is predicted to take place through adsorbed carboxyl (COOH) species, whereas formate (HCOO) is predicted to be a spectator species. We conclude that the clean Pt(111) is a good representation of the active site for the WGS reaction on Pt catalysts, whereas the active sites on the Pt–Re alloy catalyst likely contain partially oxidized metal ensembles.

  2. Oxaliplatin complexes with carnosine and its derivatives: in vitro cytotoxicity, mass spectrometric and computational studies with a focus on complex fragmentation.

    PubMed

    Moustafa, Eslam M; Camp, Claire L; Youssef, Ahmed S; Amleh, Asma; Reid, Helen J; Sharp, Barry L; Shoeib, Tamer

    2013-11-01

    The complexation of the Pt-based anti-cancer drug oxaliplatin (OxPt) with biological ligands other than DNA is believed to be a major cellular sink for the drug reducing its therapeutic potential and acting as a potential cause of toxicity. In this paper, the very first hypothesis driven investigation of the role of the naturally abundant cytoplasmic dipeptide ligand β-alanyl-l-histidine dipeptide (carnosine) in OxPt detoxification is presented. In vitro studies on hepatocellular carcinoma HepG2 cells suggest that carnosine may inhibit the cytotoxic action of OxPt most likely through the formation of complexes that are less cytotoxic than OxPt alone. Evidence is provided to suggest that pre-exposure of HepG2 cells to elevated levels of carnosine appears to have a lasting effect on reducing the cytotoxicity of OxPt even after the removal of the externally added carnosine. This effect, however, is likely under kinetic control as its magnitude was shown not to vary significantly with the level of carnosine exposure within the concentration range used in this study. Various mass spectrometry techniques employing electrospray ionization and chip nanospray were employed to study the interaction of oxaliplatin with carnosine as well as two of its derivatives β-alanyl-N-methylhistidine (anserine) and N-acetylcarnosine (NAC). Evidence of complexation between OxPt and each of the three ligands examined is presented. Most species observed were unambiguously assigned and compared to their theoretical isotopic patterns. Common fragmentation products due to the collisionally-activated protonated complexes of each of the ligands examined with OxPt, [M + OxPt + H](+), where M = carnosine, anserine or NAC, were reported. Density functional calculations at the B3LYP/LANL2DZ level were used to obtain structural information and relative free energies of different isomers of the observed precursor [Carnosine + OxPt + H](+) both in the gas phase and in solution as well as to probe its

  3. A Case Study in Chemical Kinetics: The OH + CO Reaction.

    ERIC Educational Resources Information Center

    Weston, Ralph E., Jr.

    1988-01-01

    Reviews some important properties of the bimolecular reaction between the hydroxyl radical and carbon monoxide. Investigates the kinetics of the reaction, the temperature and pressure dependence of the rate constant, the state-to-state dynamics of the reaction, and the reverse reaction. (MVL)

  4. Temperature-dependent, relative-rate study of the reactions of 1- and 2-butoxyl radicals

    NASA Astrophysics Data System (ADS)

    Johnson, D.; Cassanelli, P.; Cox, R. A.

    2003-04-01

    Alkoxyl radicals (RO\\cdot) are important intermediates in the chains of free radical reactions that constitute the gas-phase oxidation of volatile organic compounds (VOCs). Generally there are a number of different reaction pathways available to alkoxyl radicals and, depending on conditions of temperature and the structure of RO\\cdot, these may be in competition. The major reactions of RO\\cdot are (1) reaction with O_2 to yield a carbonyl product and a hydroperoxy, HO_2, radical, (2) decomposition to yield a carbonyl product and a radical fragment, and (3) isomerisation via a six-membered transition state to yield a d-hydroxylated radical species. Thus the chemistry of alkoxyl radicals determines the atmospheric impact of the oxidation of a given VOC, in terms of the immediate effects of closed-shell products, and as a result of the further chemistry of free radical products. HO_2 can react with NO to yield photolabile NO_2 (and hence contribute to photochemical ozone formation), and organic radical fragments act to propagate the oxidation chain of reactions. As ozone has been identified to be an important greenhouse gas in the upper troposphere/lower stratosphere (UTLS) region it is important to understand how temperature affects the relative rates of reactions (1) to (3), and thus how the presence of VOCs in the UTLS region affects the coupled chemistries of HO_x and O_3. In the present study, we have looked at the reactions of 1- and 2-butoxyl radicals (formed in the reaction of OH with butane) in terms of the relative rates of their bimolecular reactions with O_2 (1) and unimolecular processes (2,3). The two butoxyl radicals were studied separately and were formed directly from the photolysis of 1- or 2-butylnitrite. Experiments were carried out using a metre-long photochemical flow cell made of quartz. The temperature of the cell could be controlled and for the experiments carried out in the present study was operated between about 250 and 340 K. Reactant

  5. Phylogeography of four frog species in forest fragments of northeastern Brazil--a preliminary study.

    PubMed

    Carnaval, Ana Carolina O Q

    2002-11-01

    I contrast mitochondrial DNA genealogies based on 612 bp of the cytochrome b gene across four co-distributed species of frogs in Northeastern Brazil. They are Hyla albomarginata, Hyla branneri, Proceratophrys boiei, and Scinax nebulosus. Samples were collected from the core or edge of six rainforest remnants in the states of Pernambuco and Alagoas. Three fragments are located within the humid Atlantic Forest morphoclimatic domain (municipalities of Cabo de Santo Agostinho, Ibateguara, and Jaqueira), two are located in the transition zone between the Atlantic Forest domain and the semi-arid Caatinga (Caruaru and Timbaúba), and one is found within the Caatinga (Brejo da Madre de Deus). Results show that local patterns and levels of genetic diversity are influenced by taxon-specific habitat requirements. Populations of the montane, closed-canopy species P. boiei show strong geographical structure, reflecting barriers to gene flow that predate human-driven habitat destruction. Species occurring along forest edges, such as H. albomarginata and S. nebulosus, show genetic patterns similar to those of P. boiei, but lower levels of genetic divergence. The more generalist Hyla branneri shows no geographic pattern. The data are in agreement with distribution and fossil data gathered for other groups of organisms, suggesting that mesic forests occupied the currently arid Caatinga in the recent past.

  6. Structural study of human growth hormone-releasing factor fragment (1?29) by vibrational spectroscopy

    NASA Astrophysics Data System (ADS)

    Carmona, P.; Molina, M.; Lasagabaster, A.

    1995-05-01

    The conformational structure of fragment 1-29 of human growth hormone releasing factor, hGHRF (1-29), in aqueous solution and in the solid state is investigated by infrared and Raman spectroscopy. The polypeptide backbone is found to be unordered in the solid state. However, the spectra of the peptide prepared as 5% (w/w) aqueous solutions show that approximately 28% of the peptide is involved in intermolecular β-sheet aggregation. The remainder of the peptide exists largely as disordered and β-sheet conformations with a small portion of α-helices. Tyrosine residues are found to be exposed to the solvent. The secondary structures are quantitatively examined through infrared spectroscopy, the conformational percentages being near those obtained by HONDAet al. [ Biopolymers31, 869 (1991)] using circular dichroism. The fast hydrogen/deuterium exchange in peptide groups and the absence of any NMR sign indicative of ordered structure [ G. M. CLOREet al., J. Molec. Biol.191, 553 (1986)] support that the solution conformations of the non-aggregated peptide interconvert in dynamic equilibrium. Some physiological advantages that may derive from this conformational flexibility are also discussed

  7. Preliminary X-ray crystallographic studies of mouse UPR responsive protein P58(IPK) TPR fragment

    PubMed Central

    Tao, Jiahui; Wu, Yunkun; Ron, David; Sha, Bingdong

    2008-01-01

    Endoplasmic reticulum (ER) stress induces the unfolded protein response (UPR), which can promote protein folding and misfolded protein degradation and attenuate protein translation and protein translocation into the ER. P58(IPK) has been proposed to function as a molecular chaperone to maintain protein-folding homeostasis in the ER under normal and stressed conditions. P58(IPK) contains nine TPR motifs and a C-terminal J-domain within its primary sequence. To investigate the mechanism by which P58(IPK) functions to promote protein folding within the ER, a P58(IPK) TPR fragment without the C-terminal J-domain was crystallized. The crystals diffract to 2.5 Å resolution using a synchrotron X-ray source. The crystals belong to space group P21, with unit-cell parameters a = 83.53, b = 92.75, c = 84.32 Å, α = 90.00, β = 119.36, γ = 90.00°. There are two P58(IPK) molecules in the asymmetric unit, which corresponds to a solvent content of approximately 60%. Structure determination by MAD methods is under way. PMID:18259061

  8. Direct pathway from early/recycling endosomes to the Golgi apparatus revealed through the study of shiga toxin B-fragment transport.

    PubMed

    Mallard, F; Antony, C; Tenza, D; Salamero, J; Goud, B; Johannes, L

    1998-11-16

    Shiga toxin and other toxins of this family can escape the endocytic pathway and reach the Golgi apparatus. To synchronize endosome to Golgi transport, Shiga toxin B-fragment was internalized into HeLa cells at low temperatures. Under these conditions, the protein partitioned away from markers destined for the late endocytic pathway and colocalized extensively with cointernalized transferrin. Upon subsequent incubation at 37 degreesC, ultrastructural studies on cryosections failed to detect B-fragment-specific label in multivesicular or multilamellar late endosomes, suggesting that the protein bypassed the late endocytic pathway on its way to the Golgi apparatus. This hypothesis was further supported by the rapid kinetics of B-fragment transport, as determined by quantitative confocal microscopy on living cells and by B-fragment sulfation analysis, and by the observation that actin- depolymerizing and pH-neutralizing drugs that modulate vesicular transport in the late endocytic pathway had no effect on B-fragment accumulation in the Golgi apparatus. B-fragment sorting at the level of early/recycling endosomes seemed to involve vesicular coats, since brefeldin A treatment led to B-fragment accumulation in transferrin receptor-containing membrane tubules, and since B-fragment colocalized with adaptor protein type 1 clathrin coat components on early/recycling endosomes. Thus, we hypothesize that Shiga toxin B-fragment is transported directly from early/recycling endosomes to the Golgi apparatus. This pathway may also be used by cellular proteins, as deduced from our finding that TGN38 colocalized with the B-fragment on its transport from the plasma membrane to the TGN.

  9. Characterizing fragmentation of the collective forests in southern China from multitemporal Landsat imagery: A case study from Kecheng district of Zhejiang province

    USGS Publications Warehouse

    Li, M.; Zhu, Z.; Vogelmann, J.E.; Xu, D.; Wen, W.; Liu, A.

    2011-01-01

    Tropical and subtropical forests provide important ecosystem goods and services including carbon sequestration and biodiversity conservation. These forests are facing increasing socioeconomic pressures and are rapidly being degraded and fragmented. This analysis focuses on the rate of change and patterns of fragmentation in a collective forest area in Zhejiang province, China, during the time period 1988–2005. The research consisted of two parts. The first was the development of general land cover maps and the identification of land cover changes by interpreting Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) time series imagery. The second part involved the computation and analysis of forest fragmentation metrics. For this portion of the study, fragmentation statistics were analyzed, and images were developed to depict forest fragmentation patterns and trends. Results revealed that there was a net loss of 7.8% in forest coverage, dropping from 66.8% in 1988 to 59.0% in 2005, primarily caused by agricultural expansion and poor forest management practices. An acceleration of forest fragmentation was also witnessed during the time intervals, which was evidenced by a decreasing trend in interior forest (57.2% in 1988, 55.0% in 1996 and 54.8% in 2005 respectively) coupled with the scales of the selected geospatial metrics. Continued forest loss and fragmentation are closely correlated with the existing political, educational, institutional and economic processes of contemporary China. To unlock the developmental potentials of the collective forests and to effectively mitigate the rate of forest loss and fragmentation, reforms of forest tenure and ecological immigration practices are recognized as a prospective alternative. The produced fragmentation maps further illustrates the importance of assessing landscape change history, especially the spatiotemporal patterns of forest fragments, when developing landscape level plans for biodiversity

  10. Femtosecond photodichroism studies of isolated photosystem II reaction centers.

    PubMed

    Wiederrecht, G P; Seibert, M; Govindjee; Wasielewski, M R

    1994-09-13

    Photosynthetic conversion of light energy into chemical potential begins in reaction center protein complexes, where rapid charge separation occurs with nearly unit quantum efficiency. Primary charge separation was studied in isolated photosystem II reaction centers from spinach containing 6 chlorophyll a, 2 pheophytin a (Pheo), 1 cytochrome b559, and 2 beta-carotene molecules. Time-resolved pump-probe kinetic spectroscopy was carried out with 105-fs time resolution and with the pump laser polarized parallel, perpendicular, and at the magic angle (54.7 degrees) relative to the polarized probe beam. The time evolution of the transient absorption changes due to the formation of the oxidized primary electron donor P680+ and the reduced primary electron acceptor Pheo- were measured at 820 nm and 545 nm, respectively. In addition, kinetics were obtained at 680 nm, the wavelength ascribed to the Qy transition of the primary electron donor P680 in the reaction center. At each measured probe wavelength the kinetics of the transient absorption changes can be fit to two major kinetic components. The relative amplitudes of these components are strongly dependent on the polarization of the pump beam relative to that of the probe. At the magic angle, where no photoselection occurs, the amplitude of the 3-ps component, which is indicative of the charge separation, dominates. When the primary electron acceptor Pheo is reduced prior to P680 excitation, the 3-ps component is eliminated.

  11. Femtosecond photodischroism studies of isolated photosystem II reaction centers

    SciTech Connect

    Wiederrecht, G.P.; Wasielewski, M.R.; Siebert, M.; Govindjee

    1994-09-13

    Photosynthetic conversion of light energy into chemical potential begins in reaction center protein complexes, where rapid charge separation occurs with nearly unit quantum efficiency. Primary charge separation was studied in isolated photosystem II reaction centers from spinach containing 6 chlorophyll a, 2 pheophytin a (Pheo), 1 cytochrome b{sub 559}, and 2 {beta}-carotene molecules. Time-resolved pump-probe kinetic spectroscopy was carried out with 105-fs time resolution and with the pump laser polarized parallel, perpendicular, and at the magic angle (54.7{degrees}) relative to the polarized probe beam. The time evolution of the oxidized primary electron donor P680{sup +} and the reduced primary electron acceptor Pheo{sup {minus}} were measured at 820 nm and 545 nm, respectively. In addition, kinetics were obtained at 680 nm, the wavelength ascribed to the Q{sub y} transition of the primary electron donor P680 in the reaction center. At each measured probe wavelength the kinetics of the transient absorption changes can be fit to two major kinetic components. The relative amplitudes of these components are strongly dependent on the polarization of the pump beam relative to that of the probe. At the magic angle, where no photoselection occurs, the amplitude of the 3-ps component, which is indicative of the charge separation, dominates. When the primary electron acceptor Pheo is reduced prior to P680 excitation, the 3-ps component is eliminated. 48 refs., 6 figs., 1 tab.

  12. Nonequilibrium phenomena in N{sub 2}-cluster-surface collisions: A molecular-dynamics study of fragmentation, lateral jetting, and nonequilibrium energy distributions

    SciTech Connect

    Zimmermann, Steffen; Urbassek, Herbert M.

    2006-12-15

    Using molecular-dynamics simulation, we study the impact of (N{sub 2}){sub 2869} clusters on a flat rigid wall. We study the cluster fragmentation process, the formation of lateral jets, the energy redistribution among the resulting fragments, and the ratio of internal and translational energy of the emerging free molecules as a function of cluster impact energy in the range of 0.076-1520 meV/molecule. We find the fragmentation threshold energy to be in agreement with that found previously for (N{sub 2}){sub 13} clusters; the (scaled) number of fragments, however, increases more slowly with impact energy. Also the energy redistribution of the cluster impact energy among the internal and translational energy of the fragments is similar to that found for the small cluster. This means in particular that free molecules show a strong nonequilibrium energy partitioning in which the internal degrees of freedom are considerably less excited than the translational degrees of freedom. We also find that at impact energies above the fragmentation threshold the angular distribution of fragments is peaked parallel to the surface--i.e., the formation of lateral surface jets.

  13. An Ion Microprobe Study of a Unique Oldhamite-Pyroxenite Fragment from the Bustee Aubrite

    NASA Astrophysics Data System (ADS)

    Kurat, G.; Zinner, E.; Brandstatter, F.

    1992-07-01

    While it is widely believed that the minerals in aubrite breccias are of igneous origin (e.g., 1) bulk trace element abundances (e.g., 2) and the distribution of trace elements between phases (e.g., 3-5) are incompatible with an igneous genesis and strongly suggest a nebular origin (e.g., 6). Here we report trace element data on mineral phases in a unique rock fragment from the Bustee meteorite as well as with the N and Ti isotope compositions in osbornite. In the first characterization of Bustee, Story-Maskelyne (7) described a rock fragment consisting of oldhamite, enstatite, augite, and plagioclase in which he also first dicovered osbornite. The rock consists of large (2-3 mm) rounded oldhamite embedded in granular pyroxene (pictures given by 7 and 8). Osbornite is commonly included in oldhamite. Some metal (Si- and Cr-bearing) and a few grains of heideite and other rare sulfides are present. The REE abundances in selected minerals are shown in the figure. Surprisingly, all patterns are nearly flat. The oldhamite is strongly enriched in REE (see also 3-5) and has a positive Eu anomaly. Osbornite shows a slightly fractionated pattern with La>Lu and REE abundances of 0.5-9 x CI. Pyroxenes have the lowest REE contents at 0.2-0.3 x CI (pigeonite) and 0.03-0.08 x CI (enstatite). Isotopic compositions of Ti and N in osbornite and of Ca in oldhamite are indistinguishable from terrestrial. The distribution of REE beween mineral phases does not correspond to experimentally determined distribution coefficients (9). This and the primitive (not crystal-chemically controlled) REE abundances in all phases make it very likely that the minerals of the oldhamite-pyroxenite from Bustee were formed by condensation. The condensation sequence must have been osbornite-oldhamite- pigeonite-enstatite. As the first major phase to condense, oldhamite apparently scavenged most of the REE present in the gas. It must have been formed well below 1380 K (10) and from a slightly fractionated

  14. Study of all Reaction Channels in Deuteron-Deuteron Scattering

    NASA Astrophysics Data System (ADS)

    Ramazani-Moghaddam-Arani, A.; Amir-Ahmadi, H. R.; Bacher, A. D.; Bailey, C. D.; Biegun, A.; Eslami-Kalantari, M.; Gašparić, I.; Joulaeizadeh, L.; Kalantar-Nayestanaki, N.; Kistryn, St.; Kozela, A.; Mardanpour, H.; Messchendorp, J. G.; Micherdzinska, A. M.; Moeini, H.; Shende, S. V.; Stephan, E.; Stephenson, E. J.; Sworst, R.

    Few-nucleon systems can be used as fundamental laboratories for studying details of the nuclear force effects. We performed a series of deuteron-deuteron scattering experiments at intermediate energies. The experiments exploited BINA and BBS experimental setups and polarized deuteron beams with kinetic energies of 65 and 90 MeV/nucleon. These experiments aim to measure differential cross sections, vector and tensor analyzing powers of all available reaction channels in deuteron-deuteron scattering. With these data we will provide a systematic database, which will be used to test present theoretical approximations and upcoming ab-initio calculations in four-nucleon system.

  15. Quantum chemical study of penicillin: Reactions after acylation

    NASA Astrophysics Data System (ADS)

    Li, Rui; Feng, Dacheng; Zhu, Feng

    The density functional theory methods were used on the model molecules of penicillin to determine the possible reactions after their acylation on ?-lactamase, and the results were compared with sulbactam we have studied. The results show that, the acylated-enzyme tetrahedral intermediate can evolves with opening of ?-lactam ring as well as the thiazole ring; the thiazole ring-open products may be formed via ?-lactam ring-open product or from tetrahedral intermediate directly. Those products, in imine or enamine form, can tautomerize via hydrogen migration. In virtue of the water-assisted, their energy barriers are obviously reduced.

  16. Physicochemical studies on the reaction between formaldehyde and DNA.

    PubMed

    FREIFELDER, D; DAVISON, P F

    1963-01-01

    The reaction between formaldehyde and phage T7 DNA has been studied by optical absorbance and sedimentation measurements. Through the course of denaturation, OD(200) and s(20, w) rise; after the attainment of full hyperchromicity the s(20, w) falls sharply, suggesting a decrease in molecular weight. Conditions in which formaldehyde causes cross-linking are defined. Some experimental applications of the denaturation technique are given. Evidence which suggests that preformed single-strand interruptions may exist in phage DNA is briefly discussed.

  17. Physicochemical Studies on the Reaction between Formaldehyde and DNA

    PubMed Central

    Freifelder, David; Davison, Peter F.

    1963-01-01

    The reaction between formaldehyde and phage T7 DNA has been studied by optical absorbance and sedimentation measurements. Through the course of denaturation, OD200 and s20, w rise; after the attainment of full hyperchromicity the s20, w falls sharply, suggesting a decrease in molecular weight. Conditions in which formaldehyde causes cross-linking are defined. Some experimental applications of the denaturation technique are given. Evidence which suggests that preformed single-strand interruptions may exist in phage DNA is briefly discussed. PMID:13959526

  18. Heck-type reactions of imine derivatives: a DFT study.

    PubMed

    Li, Zhe; Fu, Yao; Zhang, Song-Lin; Guo, Qing-Xiang; Liu, Lei

    2010-06-01

    The mechanism of a recently discovered intramolecular Heck-type coupling of oximes with aryl halides (Angew. Chem. Int. Ed. 2007, 46, 6325) was systematically studied by using density functional methods enhanced with a polarized continuum solvation model. The overall catalytic cycle of the reaction was found to consist of four steps: oxidative addition, migratory insertion, beta-H elimination, and catalyst regeneration, whereas an alternative base-promoted C-H activation pathway was determined to be less favorable. Migratory insertion was found to be the rate determining step in the catalytic cycle. The apparent activation barrier of migratory insertion of the (E)-oxime was +20.5 kcal mol(-1), whereas the barrier of (Z)-oxime was as high as +32.7 kcal mol(-1). However, (Z)-oxime could isomerize to form the more active (E)-oxime with the assistance of K(2)CO(3), so that both the (E)- and (Z)-oxime substrates could be transformed to the desired product. Our calculations also indicated that the Z product was predominant in the equilibrium of the isomerization of the imine double bond, which constituted the reason for the good Z-selectivity observed for the reaction. Furthermore, we examined the difference between the intermolecular Heck-type reactions of imines and of olefins. It was found that in the intermolecular Heck-type coupling of imines, the apparent activation barrier of migratory insertion was as high as +35 kcal mol(-1), which should be the main obstacle of the reaction. The analysis also revealed the main problem for the intermolecular Heck-type reactions of imines, which was that the breaking of a C=N pi bond was much more difficult than the breaking of a C=C pi bond. After systematic examination of a series of substituted imines, (Z)-N-amino imine and N-acetyl imine were found to have relatively low barriers of migratory insertion, so that they might be possible substrates for intermolecular Heck-type coupling.

  19. Odd-even staggering in yields of neutron-deficient nuclei produced by projectile fragmentation

    NASA Astrophysics Data System (ADS)

    Mei, B.; Xu, H. S.; Zhang, Y. H.; Wang, M.; Tu, X. L.; Schmidt, K.-H.; Litvinov, Yu. A.; Sun, Z. Y.; Zhou, X. H.; Yuan, Y. J.; Blaum, K.; Ricciardi, M. V.; Kelić-Heil, A.; Mao, R. S.; Hu, Z. G.; Shuai, P.; Zang, Y. D.; Ma, X. W.; Zhang, X. Y.; Xia, J. W.; Xiao, G. Q.; Guo, Z. Y.; Yang, J. C.; Zhang, X. H.; Xu, X.; Yan, X. L.; Zhang, W.; Zhan, W. L.

    2016-10-01

    Background: Fragment yields exhibit a strong odd-even staggering (OES). This OES has been experimentally observed in different fragmentation reactions with different projectile-target combinations. However, the experimental data are still scarce for fragments close to drip lines and the origin of this OES is not well understood. Purpose: More experimental data are needed to explore the origin of this OES in fragment yields and to validate fragmentation reaction models, especially for nuclei close to the drip lines. To study the pronounced OES near the proton drip line, we measured the yields of Tz=-1 and Tz=-3 /2 nuclei over a wide range of mass number. Methods: The combination of a fragment separator and a storage ring at the Heavy Ion Research Facility in Lanzhou has been used to measure the yields of Tz=-1 and Tz=-3 /2 fragments, produced by 58Ni projectiles impinging on a beryllium target at an energy of about 463 MeV/nucleon. Results: A very strong OES is observed in the measured yields of both Tz=-1 and Tz=-3 /2 fragments. Our experimental data demonstrate that the shell structure has a significant impact on the magnitude of this OES. A comparison of different fragmentation reaction data indicates that this OES is almost independent of the projectile-target combinations and the fragmentation energy between 140 and 650 MeV/nucleon. Conclusions: Our study reveals that the OES of fragment yields originates mainly from the OES of particle-emission threshold energies, which is very close to the OES of fragment yields when the Coulomb barrier is considered in particle-emission threshold energies.

  20. The reaction of the bis(6,6-dimethylcyclohexadienyl)zirconium fragment with PhC 2SiMe 3 - A 5 + 2 + 2 ring construction

    NASA Astrophysics Data System (ADS)

    Harvey, Benjamin G.; Arif, Atta M.; Ernst, Richard D.

    2008-11-01

    The reaction of the edge-bridged open zirconocene, Zr(6,6-dmch) 2(PMe 3) 2 (dmch = dimethylcyclohexadienyl) with two equivalents of PhC 2SiMe 3 leads to a 5 + 2 + 2 ring construction, resulting in a 4.3.1 bicyclodecadienyl skeleton. The resulting complex, with η3-allyl, η4-diene, and η5-dienyl coordination, has a formal 16 electron configuration, and contains close contacts between the metal center and two lengthened C-C bonds, indicative of weak agostic interactions.

  1. Photosynthetic reaction center of green sulfur bacteria studied by EPR

    SciTech Connect

    Nitschke, W.; Rutherford, A.W. ); Fieler, U. )

    1990-04-24

    Membrane preparations of two species of the green sulfur bacteria Chlorobium have been studied be EPR. Three signals were detected which were attributed to iron-sulfur centers acting as electron acceptors in the photosynthetic reaction center. (1) A signal from a center designated F{sub B}, was photoinduced at 4K. (2) A similar signal, F{sub A}, was photoinduced in addition to the F{sub B} signal upon a short period of illumination at 200 K. (3) Further illumination at 200 K resulted in the appearance of a broad feature at g=1.78. This is attributed to the g{sub x} component of an iron-sulfur center designated F{sub X}. The designations of these signals as F{sub B}, F{sub A}, and F{sub X} are based on their spectroscopic similarities to signals in photosystem I (PS I). The orientation dependence of these EPR signals in ordered Chlorobium membrane multilayers is remarkably similar to that of their PS I homologues. A magnetic interaction between the reduced forms of F{sub B} and F{sub A} occurs, which is also very similar to that seen in PS I. The triplet state of P{sub 840}, the primary electron donor, could be photoinduced at 4 K in samples which had been preincubated with sodium dithionite and methyl viologen and then preilluminated at 200 K. The preillumination reduces the iron-sulfur centers while the preincubation is thought to result in the inactivation of an earlier electron acceptor. Orientation studies of the triplet signal in ordered multilayers indicate that the bacteriochlorophylls which act as the primary electron donor in Chlorobium are arranged with a structural geometry almost identical with that of the special pair in purple bacteria. The Chlorobium reaction center appears to be similar in some respects to both PS I and to the purple bacterial reaction center. This is discussed with regard to the evolution of the different types of reaction centers from a common ancestor.

  2. Equilibrium and non-equilibrium emission of complex fragments

    SciTech Connect

    Bowman, D.R.

    1989-08-01

    Complex fragment emission (Z{gt}2) has been studied in the reactions of 50, 80, and 100 MeV/u {sup 139}La + {sup 12}C, and 80 MeV/u {sup 139}La + {sup 27}Al, {sup nat}Cu, and {sup 197}Au. Charge, angle, and energy distributions were measured inclusively and in coincidence with other complex fragments, and were used to extract the source rapidities, velocity distributions, and cross sections. The experimental emission velocity distributions, charge loss distributions, and cross sections have been compared with calculations based on statistical compound nucleus decay. The binary signature of the coincidence events and the sharpness of the velocity distributions illustrate the primarily 2-body nature of the {sup 139}La + {sup 12}C reaction mechanism between 50 and 100 MeV/u. The emission velocities, angular distributions, and absolute cross sections of fragments of 20{le}Z{le}35 at 50 MeV/u, 19{le}Z{le}28 at 80 MeV/u, and 17{le}Z{le}21 at 100 MeV/u indicate that these fragments arise solely from the binary decay of compound nuclei formed in incomplete fusion reactions in which the {sup 139}La projectile picks up about one-half of the {sup 12}C target. In the 80 MeV/u {sup 139}La + {sup 27}Al, {sup nat}Cu, and {sup 197}Au reactions, the disappearance of the binary signature in the total charge and velocity distributions suggests and increase in the complex fragment and light charged particle multiplicity with increasing target mass. As in the 80 and 100 MeV/u {sup 139}La + {sup 12}C reactions, the lighter complex fragments exhibit anisotropic angular distributions and cross sections that are too large to be explained exclusively by statistical emission. 143 refs., 67 figs.

  3. Direct Pathway from Early/Recycling Endosomes to the Golgi Apparatus Revealed through the Study of Shiga Toxin B-fragment Transport

    PubMed Central

    Mallard, Frédéric; Antony, Claude; Tenza, Danièle; Salamero, Jean; Goud, Bruno; Johannes, Ludger

    1998-01-01

    Shiga toxin and other toxins of this family can escape the endocytic pathway and reach the Golgi apparatus. To synchronize endosome to Golgi transport, Shiga toxin B-fragment was internalized into HeLa cells at low temperatures. Under these conditions, the protein partitioned away from markers destined for the late endocytic pathway and colocalized extensively with cointernalized transferrin. Upon subsequent incubation at 37°C, ultrastructural studies on cryosections failed to detect B-fragment–specific label in multivesicular or multilamellar late endosomes, suggesting that the protein bypassed the late endocytic pathway on its way to the Golgi apparatus. This hypothesis was further supported by the rapid kinetics of B-fragment transport, as determined by quantitative confocal microscopy on living cells and by B-fragment sulfation analysis, and by the observation that actin- depolymerizing and pH-neutralizing drugs that modulate vesicular transport in the late endocytic pathway had no effect on B-fragment accumulation in the Golgi apparatus. B-fragment sorting at the level of early/recycling endosomes seemed to involve vesicular coats, since brefeldin A treatment led to B-fragment accumulation in transferrin receptor–containing membrane tubules, and since B-fragment colocalized with adaptor protein type 1 clathrin coat components on early/recycling endosomes. Thus, we hypothesize that Shiga toxin B-fragment is transported directly from early/recycling endosomes to the Golgi apparatus. This pathway may also be used by cellular proteins, as deduced from our finding that TGN38 colocalized with the B-fragment on its transport from the plasma membrane to the TGN. PMID:9817755

  4. First principle kinetic studies of zeolite-catalyzed methylation reactions.

    PubMed

    Van Speybroeck, Veronique; Van der Mynsbrugge, Jeroen; Vandichel, Matthias; Hemelsoet, Karen; Lesthaeghe, David; Ghysels, An; Marin, Guy B; Waroquier, Michel

    2011-02-02

    Methylations of ethene, propene, and butene by methanol over the acidic microporous H-ZSM-5 catalyst are studied by means of state of the art computational techniques, to derive Arrhenius plots and rate constants from first principles that can directly be compared with the experimental data. For these key elementary reactions in the methanol to hydrocarbons (MTH) process, direct kinetic data became available only recently [J. Catal.2005, 224, 115-123; J. Catal.2005, 234, 385-400]. At 350 °C, apparent activation energies of 103, 69, and 45 kJ/mol and rate constants of 2.6 × 10(-4), 4.5 × 10(-3), and 1.3 × 10(-2) mol/(g h mbar) for ethene, propene, and butene were derived, giving following relative ratios for methylation k(ethene)/k(propene)/k(butene) = 1:17:50. In this work, rate constants including pre-exponential factors are calculated which give very good agreement with the experimental data: apparent activation energies of 94, 62, and 37 kJ/mol for ethene, propene, and butene are found, and relative ratios of methylation k(ethene)/k(propene)/k(butene) = 1:23:763. The entropies of gas phase alkenes are underestimated in the harmonic oscillator approximation due to the occurrence of internal rotations. These low vibrational modes were substituted by manually constructed partition functions. Overall, the absolute reaction rates can be calculated with near chemical accuracy, and qualitative trends are very well reproduced. In addition, the proposed scheme is computationally very efficient and constitutes significant progress in kinetic modeling of reactions in heterogeneous catalysis.

  5. Computer modelling of the microstructure of the trabecular bone fragments for the study of stress-strain state

    NASA Astrophysics Data System (ADS)

    Lastovkina, Y. N.; Kolmakova, T. V.

    2016-11-01

    The paper presents the computer models of the structure of the trabecular bone tissue. The approach to the construction of computer models of fragments of cancellous bone tissues was offered. The model fragment of the trabecular bone tissue was built based on the data of structure of the real bone fragments, taking into account the orientation of the trabeculae of bones, their length and thickness.

  6. Surface studies of lithium-oxygen redox reactions over HOPG

    NASA Astrophysics Data System (ADS)

    Marchini, Florencia; Herrera, Santiago E.; Calvo, Ernesto J.; Williams, Federico J.

    2016-04-01

    The O2/Li2O2 electrode reaction has been studied on low surface area HOPG electrodes in 0.1 M LiPF6 in dimethyl sulfoxide (DMSO) electrolyte. Studies were performed using electrochemical cells coupled to a XPS spectrometer and to an AFM microscope. AFM images after electrochemical treatment at cathodic potentials exhibited 20 to 100 nm in height features, whereas anodic treatment showed a thin film of about 1 nm thickness deposited over the HOPG electrode. XPS spectra after electrochemical treatment showed surface species due to DMSO and LiPF6 decomposition. These findings indicate the high reactivity of oxygen reduction products towards the electrolyte and the solvent. The unwanted deposits formed under electrochemical operation cannot be completely eliminated from the surface even after applying high anodic potentials. This highlights the known loss of capacity of Li-air batteries, issue that must be overcome for successful applications.

  7. A kinetic study of the CH2OO Criegee intermediate self-reaction, reaction with SO2 and unimolecular reaction using cavity ring-down spectroscopy.

    PubMed

    Chhantyal-Pun, Rabi; Davey, Anthony; Shallcross, Dudley E; Percival, Carl J; Orr-Ewing, Andrew J

    2015-02-07

    Criegee intermediates are important species formed during the ozonolysis of alkenes. Reaction of stabilized Criegee intermediates with various species like SO2 and NO2 may contribute significantly to tropospheric chemistry. In the laboratory, self-reaction can be an important loss pathway for Criegee intermediates and thus needs to be characterized to obtain accurate bimolecular reaction rate coefficients. Cavity ring-down spectroscopy was used to perform kinetic measurements for various reactions of CH2OO at 293 K and under low pressure (7 to 30 Torr) conditions. For the reaction CH2OO + CH2OO (8), a rate coefficient k8 = (7.35 ± 0.63) × 10(-11) cm(3) molecule(-1) s(-1) was derived from the measured CH2OO decay rates, using an absorption cross section value reported previously. A rate coefficient of k4 = (3.80 ± 0.04) × 10(-11) cm(3) molecule(-1) s(-1) was obtained for the CH2OO + SO2 (4) reaction. An upper limit for the unimolecular CH2OO loss rate coefficient of 11.6 ± 8.0 s(-1) was deduced from studies of reaction (4). SO2 catalysed CH2OO isomerization or intersystem crossing is proposed to occur with a rate coefficient of (3.53 ± 0.32) × 10(-11) cm(3) molecule(-1) s(-1).

  8. A thermodynamic theory of dynamic fragmentation

    SciTech Connect

    Yew, Ching H.; Taylor, P.A.

    1993-08-01

    We present a theory of dynamic fragmentation of brittle materials based on thermodynamic arguments. We recover the expressions for average fragment size and number as originally derived by Grady. We extend the previous work by obtaining descriptions of fragment size distribution and compressibility change due to the fragmentation process. The size distribution is assumed to be proportional to the spectral power of the strain history and a sample distribution is presented for a fragmentation process corresponding to a constant rate strain history. The description of compressibility change should be useful in computational studies of fragmentation. These results should provide insight into the process of fragmentation of brittle materials from hypervelocity impact.

  9. Theoretical and computational studies of organometallic reactions: successful or not?

    PubMed

    Sakaki, Shigeyoshi; Ohnishi, Yu-Ya; Sato, Hirofumi

    2010-03-01

    Theoretical and computational methods are powerful in studying transition metal complexes. Our theoretical studies of C-H sigma-bond activation of benzene by Pd(II)-formate complex and that of methane by Ti(IV)-imido complex successfully disclosed that these reactions are understood to undergo heterolytic sigma-bond activation and the driving force is the formation of strong O-H and N-H bonds in the former and the latter, respectively. Orbital interactions are considerably different from those of sigma-bond activation by oxidative addition. The transmetallation, which is a key process in the cross-coupling reaction, is understood to be heterolytic sigma-bond activation. Our theoretical study clarified how to accelerate this transmetallation. Also, we wish to discuss weak points in theoretical and computational studies of large systems including transition metal elements, such as the necessity to incorporate solvation effect and to present quantitatively correct numerical results. The importance of solvation effects is discussed in the oxidative addition of methyliodide to Pt(II) complex which occurs in a way similar to an S(N)2 substitution. To apply the CCSD(T) (coupled cluster singles and doubles with perturbative triples correction) method, which is the gold standard of electronic structure theory, to large system, we need to reduce the size of the system by employing a small model. But, such modeling induces neglects of electronic and steric effects of substituents which are replaced in the small model. Frontier-orbital-consistent quantum-capping potential (FOC-QCP) was recently proposed by our group to incorporate the electronic effects of the substituents neglected in the modeling. The CCSD(T) calculation with the FOC-QCP was successfully applied to large systems including transition metal elements.

  10. Characteristics study of projectile's lightest fragment for 84Kr36-emulsion interaction at around 1 A GeV

    NASA Astrophysics Data System (ADS)

    Marimuthu, N.; Singh, V.; Inbanathan, S. S. R.

    2017-04-01

    In this article, we present the results of our investigations on the projectile's lightest fragment (proton) multiplicity and probability distributions with 84Kr36 emulsion collision at around 1 A GeV. The multiplicity and normalized multiplicity of projectile's lightest fragment (proton) are correlated with the compound particles, shower particles, black particles, grey particles; alpha (helium nucleus) fragments and heavily ionizing charged particles. It is found that projectile's lightest fragment (proton) is strongly correlated with compound particles and shower particles rather than other particles and the average multiplicity of projectile's lightest fragment (proton) increases with increasing compound, shower and heavily ionizing charge particles. Normalized projectile's lightest fragment (proton) is strongly correlated with compound particles, shower particles and heavily ionizing charge particles. The multiplicity distribution of the projectile's lightest fragment (proton) emitted in the 84Kr36 + emulsion interaction at around 1 A GeV with different target has been well explained by KNO scaling. The mean multiplicity of projectile's lightest fragments (proton) depends on the mass number of the projectile and does not significantly dependent of the projectile energy. The mean multiplicity of projectile's lightest fragment (proton) increases with increasing the target mass number.

  11. Characteristics study of projectile's lightest fragment for 84Kr36-emulsion interaction at around 1 A GeV

    NASA Astrophysics Data System (ADS)

    Marimuthu, N.; Singh, V.; Inbanathan, S. S. R.

    2016-12-01

    In this article, we present the results of our investigations on the projectile's lightest fragment (proton) multiplicity and probability distributions with 84Kr36 emulsion collision at around 1 A GeV. The multiplicity and normalized multiplicity of projectile's lightest fragment (proton) are correlated with the compound particles, shower particles, black particles, grey particles; alpha (helium nucleus) fragments and heavily ionizing charged particles. It is found that projectile's lightest fragment (proton) is strongly correlated with compound particles and shower particles rather than other particles and the average multiplicity of projectile's lightest fragment (proton) increases with increasing compound, shower and heavily ionizing charge particles. Normalized projectile's lightest fragment (proton) is strongly correlated with compound particles, shower particles and heavily ionizing charge particles. The multiplicity distribution of the projectile's lightest fragment (proton) emitted in the 84Kr36 + emulsion interaction at around 1 A GeV with different target has been well explained by KNO scaling. The mean multiplicity of projectile's lightest fragments (proton) depends on the mass number of the projectile and does not significantly dependent of the projectile energy. The mean multiplicity of projectile's lightest fragment (proton) increases with increasing the target mass number.

  12. A Discrete Model to Study Reaction-Diffusion-Mechanics Systems

    PubMed Central

    Weise, Louis D.; Nash, Martyn P.; Panfilov, Alexander V.

    2011-01-01

    This article introduces a discrete reaction-diffusion-mechanics (dRDM) model to study the effects of deformation on reaction-diffusion (RD) processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material). Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects. PMID:21804911

  13. The human sunburn reaction: histologic and biochemical studies

    SciTech Connect

    Gilchrest, B.A.; Soter, N.A.; Stoff, J.S.; Mihm, M.C. Jr.

    1981-01-01

    The ultraviolet-induced erythema reaction was investigated histologically and biochemically in four subjects, utilizing suction blister aspirates, analyzed for histamine and prostaglandin E2 (PGE2), and Epon-embedded 1-mu skin biopsy sections from control skin and from irradiated skin at intervals for 72 hours after exposure to a Hanovia lamp. Major histologic alterations in the epidermis included dyskeratotic and vacuolated keratinocytes (sunburn cells), and disappearance of Langerhans cells. In the dermis the major changes were vascular, involving both the superficial and deep venular plexuses. Endothelial cell enlargement was first apparent within 30 minutes of irradiation, peaked at 24 hours, and persisted throughout the 72-hour study period. Mast cell degranulation and associated perivenular edema were first apparent at 1 hour and striking at the onset of erythema, 3 to 4 hours postirradiation; edema was absent and mast cells were again normal in number and granule content at 24 hours. Histamine levels rose approximately fourfold above control values immediately after the onset of erythema and returned to baseline within 24 hours. PGE2 levels were statistically elevated even before the onset of erythema and reached approximately 150% of the control value at 24 hours. These data provide the first evidence that histamine may mediate the early phase of the human sunburn reaction and increase our understanding of its complex histologic and biochemical sequelae.

  14. A discrete model to study reaction-diffusion-mechanics systems.

    PubMed

    Weise, Louis D; Nash, Martyn P; Panfilov, Alexander V

    2011-01-01

    This article introduces a discrete reaction-diffusion-mechanics (dRDM) model to study the effects of deformation on reaction-diffusion (RD) processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material). Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects.

  15. Space shuttle orbiter reaction control system jet interaction study

    NASA Technical Reports Server (NTRS)

    Rausch, J. R.

    1975-01-01

    The space shuttle orbiter has forward mounted and rear mounted Reaction Control Systems (RCS) which are used for orbital maneuvering and also provide control during entry and abort maneuvers in the atmosphere. The effects of interaction between the RCS jets and the flow over the vehicle in the atmosphere are studied. Test data obtained in the NASA Langley Research Center 31 inch continuous flow hypersonic tunnel at a nominal Mach number of 10.3 is analyzed. The data were obtained with a 0.01 scale force model with aft mounted RCS nozzles mounted on the sting off of the force model balance. The plume simulations were accomplished primarily using air in a cold gas simulation through scaled nozzles, however, various cold gas mixtures of Helium and Argon were also tested. The effect of number of nozzles was tested as were limited tests of combined controls. The data show that RCS nozzle exit momentum ratio is the primary correlating parameter for effects where the plume impinges on an adjacent surface and mass flow ratio is the parameter where the plume interaction is primarily with the external stream. An analytic model of aft mounted RCS units was developed in which the total reaction control moments are the sum of thrust, impingement, interaction, and cross-coupling terms.

  16. A study of the Sabatier-methanation reaction kinetics

    NASA Technical Reports Server (NTRS)

    Verostko, C. E.; Forsythe, R. K.

    1974-01-01

    The kinetics of the Sabatier methanation reaction, the reduction of carbon dioxide with hydrogen to methane and water, was investigated for 58 percent nickel on kieselguhr catalyst and 20 percent ruthenium on alumina catalyst. Differential rate data from an experimental program were correlated with a power function rate equation both for forward and reverse reactions. The kinetic parameters of activation energy, frequency rate constant and reaction order were determined for the rate equation. The values of these parameters were obtained from an Arrhenius plot of the experimental differential rate data. Also the carbon monoxide side reaction effect was measured and included in the correlation of parameters. The reaction was found to fit the rate equation experimentally within the temperature range 421 K, where the reaction effectively begins, the 800 K where the reaction rate drops and departs from the rate equation form.

  17. [Reaction mechanism studies of heavy ion induced nuclear reactions]. [Dept. of Chemistry and Biochemistry, Univ. of Maryland, College Park, Maryland

    SciTech Connect

    Mignerey, A.C.

    1993-02-01

    Completed work is summarized on the topics of excitation energy division in deep-inelastic reactions and the onset of multifragmentation in La-induced reactions at E/A = 45 MeV. Magnetic fields are being calculated for the PHOBOS detector system, a two-arm multiparticle spectrometer for studying low-transverse-momentum particles produced at the Relativistic Heavy Ion Collider. The Maryland Forward Array is being developed for detection of the reaction products from very peripheral collisions; it consists of two individual units of detectors: the annular silicon detector in front and the plastic phoswich detector at back.

  18. Fission fragment driven neutron source

    DOEpatents

    Miller, Lowell G.; Young, Robert C.; Brugger, Robert M.

    1976-01-01

    Fissionable uranium formed into a foil is bombarded with thermal neutrons in the presence of deuterium-tritium gas. The resulting fission fragments impart energy to accelerate deuterium and tritium particles which in turn provide approximately 14 MeV neutrons by the reactions t(d,n).sup.4 He and d(t,n).sup.4 He.

  19. A Study of Primary Collision Dynamics in Inverse-Kinematics Reaction of 78Kr on 40Ca at a Bombarding Energy of 10 MeV per Nucleon

    NASA Astrophysics Data System (ADS)

    Henry, Eric M.

    The CHIMERA multi-detector array at LNS Catania has been used to study the inverse-kinematics reaction of 78Kr + 40Ca at a bombarding energy of 10 A MeV. The multi-detector is capable of detecting individual products of the collision essential for the reconstruction of the collision dynamics. This is the first time CHIMERA has been used at low-energy, which offered a unique challenge for the calibration and interpretation of experimental data. Initial interrogation of the calibrated data revealed a class of selected events characterized by two coincident heavy fragments (atomic number Z>3) that together account for the majority of the total mass of the colliding system. These events are consistent with the complete fusion and subsequent binary split (fission) of a composite nucleus. The observed fission fragments are characterized by a broad A, Z distribution and are centered about symmetric fission while exhibiting relative velocities significantly higher than given by Viola systematics. Additional analysis of the kinematic relationship between the fission fragments was performed. Of note, is that the center-of-mass angular distribution (dsigma/dtheta) of the fission fragments exhibits an unexpected anisotropy inconsistent with a compound-nucleus reaction. This anisotropy is indicative of a dynamic fusion/fission-like process. The observed angular distribution features a forward-backward anisotropy most prevalent for mass-asymmetric events. Furthermore, the more massive fragment of mass-asymmetric events appears to emerge preferentially in the forward direction, along the beam axis. Analysis of the angular distribution of alpha particles emitted from these fission fragments suggests the events are associated mostly with central collisions. The observations associated with this subset of events are similar to those reported for dynamic fragmentation of projectile-like fragments, but have not before been observed for a fusion/fission-like process. Comparisons to

  20. Motorcyclists' reactions to safety helmet law: a qualitative study

    PubMed Central

    Zamani-Alavijeh, Fereshteh; Niknami, Shamsaddin; Mohammadi, Eesa; Montazeri, Ali; Ghofranipour, Fazlollah; Ahmadi, Fazlollah; Bazargan, Shahrzad Hejazi

    2009-01-01

    Background Extensive body of the literature reveals that proper use of helmets is an effective way to reduce the severity of injuries and fatalities among motorcyclists. However, many motorcyclists do not use safety helmet properly. This study aimed to empirically explore reactions of motorcyclists to the safety helmet laws, in Iran. Methods Qualitative data were collected via four focus groups and 11 in-depth interviews. Participants were 28 male motorcyclists who never used a safety helmet during rides, and 4 male police officers. All transcripts, codes and categories were read for several times to exhaust identifiable major themes. During this process data were reduced from text to codes and themes. Results Five major themes emerged from the data analyses, including themes related to the following: (1) circumventing or dodging police officers; (2) simulating a helmet wearing behavior; (3) accepting the probability of receiving a ticket; (4) taking advantage of the police neglect and carelessness; and (5) using a cheap or convenient helmet. Conclusion Our findings suggest certain levels of reckless driving among the participating motorcyclists in this study. They also point to a system of law enforcement that operates haphazardly and fails to consistently penalize those who deviate from it. Further studies are needed to investigate how "risks" are perceived and relate to "reactions", and how a 'culture of masculinity' may encourage risk tolerance and a disposition toward lawlessness and carelessness among male motorcyclists. Also, there is a need for the development and implementation of multidimensional interventions that would offer socio-culturally sensitive educational and motivational messages to the motorcyclists and the in-service traffic-enforcement officers in Iran. PMID:19843325

  1. Fine fragmentation distribution from structural reactive material casings under explosive loading

    NASA Astrophysics Data System (ADS)

    Wilson, William; Zhang, Fan; Kim, Kibong

    2015-06-01

    Structural reactive material (SRM) can be used for explosive casings to provide additional blast energy. SRM fragments can react either promptly or after impact with nearby structure. Better understanding of fine fragment distributions from SRM casings is important for optimization of initiation and reaction of the SRM fragments. Key to this is knowledge of the initial fragmentation character before it has been altered by early reaction or by subsequent impact with surrounding structure. The study must be conducted beyond critical charge diameter to minimize effects of the expansion wave on fragment sizes. The collection and analysis of fragment distribution down to 40 micron size from thick SRM casings are therefore investigated in a 1.18 m diameter, 2.1 m3 closed cylindrical chamber filled with artificially-made pure snow packed to density 0.35 g/cm3. The snow quenches early reaction of SRM fragments and soft-catches the fragments before impact with the chamber walls. A 100 g cylindrical C-4 explosive charge is used, packed in a 3.3 cm inner diameter SRM casing, with length-to-diameter ratio of L/d = 2, and casing-to-explosive mass ratio of M/C = 1.75. Three types of SRM are investigated, including a baseline of Aluminum 6061 for comparison. The cased charge is suspended in an argon filled cavity, 20 cm in diameter and 40 cm long, within the snow filed chamber.

  2. Reaction studies of hot silicon and germanium radicals. Progress report, September 1, 1979-August 31, 1980

    SciTech Connect

    Gaspar, P.P.

    1980-08-31

    The experimental approach to attaining the goals of this research program is briefly outlined and the progress made in the last year is reviewed in sections entitled: (a) primary steps in the reaction of recoiling silicon and germanium atoms and the identification of reactive intermediates in the recoil reactions; (b) thermally induced silylene and germylene reactions; (c) ion-molecule reaction studies.

  3. Computational Chemistry in the Undergraduate Laboratory: A Mechanistic Study of the Wittig Reaction

    ERIC Educational Resources Information Center

    Albrecht, Birgit

    2014-01-01

    The Wittig reaction is one of the most useful reactions in organic chemistry. Despite its prominence early in the organic chemistry curriculum, the exact mechanism of this reaction is still under debate, and this controversy is often neglected in the classroom. Introducing a simple computational study of the Wittig reaction illustrates the…

  4. Kinetic study of the reactions between chloramine disinfectants and hydrogen peroxide: temperature dependence and reaction mechanism.

    PubMed

    McKay, Garrett; Sjelin, Brittney; Chagnon, Matthew; Ishida, Kenneth P; Mezyk, Stephen P

    2013-09-01

    The temperature-dependent kinetics for the reaction between hydrogen peroxide and chloramine water disinfectants (NH2Cl, NHCl2, and NCl3) have been determined using stopped flow-UV/Vis spectrophotometry. Rate constants for the mono- and dichloramine-peroxide reaction were on the order of 10(-2)M(-1)s(-1) and 10(-5)M(-1)s(-1), respectively. The reaction of trichloramine with peroxide was negligibly slow compared to its thermal and photolytically-induced decomposition. Arrhenius expressions of ln(kH2O2-NH2Cl)=(17.3±1.5)-(51500±3700)/RT and ln(kH2O2-NHCl2)=(18.2±1.9)-(75800±5100)/RT were obtained for the mono- and dichloramine peroxide reaction over the temperature ranges 11.4-37.9 and 35.0-55.0°C, respectively. Both monochloramine and hydrogen peroxide were first-order in the rate-limiting kinetic step and concomitant measurements made using a chloride ion selective electrode showed that the chloride was produced quantitatively. These data will aid water utilities in predicting chloramine concentrations (and thus disinfection potential) throughout the water distribution system.

  5. Reaction between Chromium(III) and EDTA Ions: an Overlooked Mechanism of Case Study Reaction of Chemical Kinetics.

    PubMed

    Cerar, Janez

    2015-01-01

    Widely cited and accepted explanation of reaction mechanism of the case study reaction of chemical kinetics between Cr(III) ions and ethylenediaminetetraacetic acid (EDTA) contradicts modern chromium(III) coordination chemistry data. Absorption UV and visible light spectra were recorded during the reaction between aqueous solution of Cr(NO(3))(3) and EDTA in order to obtain new information about this reaction. Analysis of the spectra showed that only very small fraction of intermediates may be present in solution during the course of the reaction. The reaction scheme was established and according to it calculations based on a simplified model were carried out. Literature data for constants were used if known, otherwise, adjusted values of their sound estimates were applied. Reasonable agreement of the model calculations with the experimental data was obtained for pH values 3.8 and 4.5 but the model failed to reproduce measured rate of reaction at pH 5.5, probably due to the use of the oversimplified model.

  6. Interaction of an anticancer peptide fragment of azurin with p53 and its isolated domains studied by atomic force spectroscopy.

    PubMed

    Bizzarri, Anna Rita; Santini, Simona; Coppari, Emilia; Bucciantini, Monica; Di Agostino, Silvia; Yamada, Tohru; Beattie, Craig W; Cannistraro, Salvatore

    2011-01-01

    p28 is a 28-amino acid peptide fragment of the cupredoxin azurin derived from Pseudomonas aeruginosa that preferentially penetrates cancerous cells and arrests their proliferation in vitro and in vivo. Its antitumor activity reportedly arises from post-translational stabilization of the tumor suppressor p53 normally downregulated by the binding of several ubiquitin ligases. This would require p28 to specifically bind to p53 to inhibit specific ligases from initiating proteosome-mediated degradation. In this study, atomic force spectroscopy, a nanotechnological approach, was used to investigate the interaction of p28 with full-length p53 and its isolated domains at the single molecule level. Analysis of the unbinding forces and the dissociation rate constant suggest that p28 forms a stable complex with the DNA-binding domain of p53, inhibiting the binding of ubiquitin ligases other than Mdm2 to reduce proteasomal degradation of p53.

  7. MCNP6 Simulation of Light and Medium Nuclei Fragmentation at Intermediate Energies

    SciTech Connect

    Mashnik, Stepan Georgievich; Kerby, Leslie Marie

    2015-08-24

    Fragmentation reactions induced on light and medium nuclei by protons and light nuclei of energies around 1 GeV/nucleon and below are studied with the Los Alamos transport code MCNP6 and with its CEM03.03 and LAQGSM03.03 event generators. CEM and LAQGSM assume that intermediate-energy fragmentation reactions on light nuclei occur generally in two stages. The first stage is the intranuclear cascade (INC), followed by the second, Fermi breakup disintegration of light excited residual nuclei produced after the INC. CEM and LAQGSM account also for coalescence of light fragments (complex particles) up to sup>4He from energetic nucleons emitted during INC. We investigate the validity and performance of MCNP6, CEM, and LAQGSM in simulating fragmentation reactions at intermediate energies and discuss possible ways of further improving these codes.

  8. Ortho-hydroxyl effect and proton transfer via ion-neutral complex: the fragmentation study of protonated imine resveratrol analogues in mass spectrometry.

    PubMed

    Yue, Lei; Li, Jing; Xie, Xiaodong; Guo, Cheng; Yin, Xinchi; Yin, Qi; Chen, Yinjuan; Pan, Yuanjiang; Ding, Chuanfan

    2016-07-01

    The fragmentation pathways of protonated imine resveratrol analogues in the gas-phase were investigated by electrospray ionization-tandem mass spectrometry. Benzyl cations were formed in the imine resveratrol analogues that had an ortho-hydroxyl group on the benzene ring A. The specific elimination of the quinomethane neutral, CH2  = C6 H4  = O, from the two isomeric ions [M1 + H](+) and [M3 + H](+) via the corresponding ion-neutral complexes was observed. The fragmentation pathway for the related meta-isomer, ion [M2 + H](+) and the other congeners was not observed. Accurate mass measurements and additional experiments carried out with a chlorinated analogue and the trideuterated isotopolog of M1 supported the overall interpretation of the fragmentation phenomena observed. It is very helpful for understanding the intriguing roles of ortho-hydroxyl effect and ion-neutral complexes in fragmentation reactions and enriching the knowledge of the gas-phase chemistry of the benzyl cation. Copyright © 2016 John Wiley & Sons, Ltd.

  9. Specific Conjugation of the Hinge Region for Homogeneous Preparation of Antibody Fragment-Drug Conjugate: A Case Study for Doxorubicin-PEG-anti-CD20 Fab' Synthesis.

    PubMed

    Zhou, Zhan; Zhang, Jing; Zhang, Yan; Ma, Guanghui; Su, Zhiguo

    2016-01-20

    Conventional preparation strategies for antibody-drug conjugates (ADCs) result in heterogeneous products with various molecular sizes and species. In this study, we developed a homogeneous preparation strategy by site-specific conjugation of the anticancer drug with an antibody fragment. The model drug doxorubicin (DOX) was coupled to the Fab' fragment of anti-CD20 IgG at its permissive sites through a heterotelechelic PEG linker, generating an antibody fragment-drug conjugate (AFDC). Anti-CD20 IgG was digested and reduced specifically with β-mercaptoethylamine to generate the Fab' fragment with two free mercapto groups in its hinge region. Meanwhile, DOX was conjugated with α-succinimidylsuccinate ω-maleimide polyethylene glycol (NHS-PEG-MAL) to form MAL-PEG-DOX, which was subsequently linked to the free mercapto containing Fab' fragment to form a Fab'-PEG-DOX conjugate. The dual site-specific bioconjugation was achieved through the combination of highly selective reduction of IgG and introduction of heterotelechelic PEG linker. The resulting AFDC provides an utterly homogeneous product, with a definite ratio of one fragment to two drugs. Laser confocal microscopy and cell ELISA revealed that the AFDC could accumulate in the antigen-positive Daudi tumor cell. In addition, the Fab'-PEG-DOX retained appreciable targeting ability and improved antitumor activity, demonstrating an excellent therapeutic effect on the lymphoma mice model for better cure rate and significantly reduced side effects.

  10. Direct Reactions for Nuclear Structure and Nuclear Astrophysics

    SciTech Connect

    Jones, Katherine Louise

    2014-12-18

    Direct reactions are powerful probes for studying the atomic nucleus. Modern direct reaction studies are illuminating both the fundamental nature of the nucleus and its role in nucleosynthetic processes occurring in the cosmos. This report covers experiments using knockout reactions on neutron-deficient fragmentation beams, transfer reactions on fission fragment beams, and theoretical sensitivity studies relating to the astrophysical r-process. Results from experiments on 108,106Sn at the NSCL, and on 131Sn at HRIBF are presented as well as the results from the nucleosynthesis study.

  11. Study of cluster structures in 10Be and 16C neutron-rich nuclei via break-up reactions

    NASA Astrophysics Data System (ADS)

    Dell'Aquila, D.; Acosta, L.; Amorini, F.; Andolina, R.; Auditore, L.; Berceanu, I.; Cardella, G.; Chatterjiee, M. B.; De Filippo, E.; Francalanza, L.; Gnoffo, B.; Grzeszczuk, A.; Lanzalone, G.; Lombardo, I.; Martorana, N.; Minniti, T.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Pop, A.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2016-05-01

    Projectile break-up reactions induced on polyethylene (CH2) target are used in order to study the spectroscopy of 10Be and 16C nuclei. For the present experiment we used 10Be and 16C beams delivered by the FRIBs facility at INFN-LNS, and the CHIMERA 4π multi-detector. 10Be and 16C structures are studied via a relative energy analysis of break-up fragments. The 4He+6He break-up channel allowed us to study the spectroscopy of 10Be; in particular we find evidence of a new state in 10Be at 13.5 MeV excitation energy. The 16C nucleus is studied via 6He-10Be correlation; we find the fingerprint of a possible state at about 20.6 MeV

  12. Coke forming reaction kinetic study on petroleum based feeds

    SciTech Connect

    Shigley, J.K.; Fu, Ta-Wei

    1988-08-01

    The carbonization of hydrocarbons is a very complex process. The pyrolysis reactions are predominantly free radical in nature and can be summarized as a polymerization process. The phase transitions from a 199% isotropic phase to an anisotropic mesophase during the carbonization of many feeds is an important and much studied phenomena. This phenomena is capitalized on in industry to produce needle or graphite coke. The kinetics of pitch polymerization and coke formation have historically been studied by measuring the solubility of the heat treated material in various solvents. The concentration of free radicals in the carbonized samples have also been used to investigate the mechanistic and kinetic aspects of the process. A very extensive study was conducted by Greinke using GPC techniques to measure the changes in narrow molecular weight ranges and the overall molecular weight distribution of a pitch during carbonization. This study focuses on the use of product volatile matter as the measure of extent of carbonization of two different feedstocks. It is ideally suited for use in commercial coking operations as a control or quality parameter of green coke.

  13. The Argonne fragment mass analyzer

    SciTech Connect

    Davids, C.N.; Larson, J.D.

    1988-01-01

    The Fragment Mass Analyzer (FMA) is currently under construction at the ATLAS facility. The FMA is an eight-meter long recoil mass spectrometer which will be used to separate nuclear reaction products from the primary heavy-ion beam and disperse them by A/q (mass/charge) at the focal plane. The FMA will be used in many different types of experiments. Gamma rays originating from very weak fusion-evaporation channels can be observed in coincidence with the recoil nucleus identified at the FMA focal plane. Production and decay of nuclei far from stability will be studied at the focal plane by implanting exotic recoils directly into detectors or by using a fast tape transport system. The FMA will also be used for reaction mechanism studies. A radioactive beam facility behind the focal plane is planned, which will allow beta-NMR and nuclear moment measurements to be made. The FMA will utilize the wide range of beam and intensities to be provided by the new ECR-positive ion injector also under construction at ATLAS. 8 refs., 4 figs., 1 tab.

  14. Theoretical study on the reaction mechanisms of CH 2SH + NO reaction

    NASA Astrophysics Data System (ADS)

    Zhan, Peiying; Pan, Yaru; Tang, Yizhen

    2009-06-01

    The mechanisms for the CH2SH + NO reaction were investigated on both of the singlet and triplet PES at the BMC-CCSD//B3LYP/6-311+G(d,p) level. The results indicate that the singlet PES is much lower than the triplet PES energetically; therefore, the reaction occurs on the singlet PES dominantly. The most favorable channel on the singlet PES takes place by a barrierless addition of N atom to CH2SH radical to form HSCH2NO. Subsequently, the rearrangement of the initial adduct HSCH2NO (IM1) to form another intermediate IM3 via a four-center transition state, followed by the C-O bond fission in IM3 leading to the major product CH2S + HNO. Due to high barriers, other product including HC(N)SH + HO, HON + CH2S, and HNO + CHSH could be negligible. The direct abstraction channel was also determined to yield CH2S + HON. With high barrier (33.3 kcal/mol), it is not competitive with the addition channel, in which all stationary points are lower than reactant energetically. While on the triplet PES, with the lowest barrier height (18.8 kcal/mol), the direct N-abstracted channel to form CH2S + HNO is dominant. However, it is not competitive with the channels on the singlet PES. Our results are in good accordance with experimental conclusions that the reaction proceeds via addition mechanism.

  15. Hypersensitive radical probe studies of chloroperoxidase-catalyzed hydroxylation reactions.

    PubMed

    Toy, P H; Newcomb, M; Hager, L P

    1998-07-01

    The oxidation of hypersensitive radical probes by chloroperoxidase from Caldariomyces fumago (CPO) was studied in an attempt to "time" a putative radical intermediate. Oxidation of (trans-2-phenylcyclopropyl)methane, previously studied by Zaks and Dodds [Zaks, A., and Dodds, D. R. (1995) J. Am. Chem. Soc. 115, 10419-10424] was reinvestigated. Unrearranged oxidation products were found as previously reported, and control experiments demonstrated that the cyclic alcohol from oxidation at the cyclopropylcarbinyl position, while subject to further oxidation, survives CPO oxidation as detectable species. However, in contrast to the report by Zaks and Dodds, the rearranged alcohol product expected from ring opening of a cyclopropylcarbinyl radical intermediate was shown to be unstable toward the enzyme oxidation reaction. Because of this instability, two new hypersensitive radical probes, (trans-2-phenylcyclopropyl)ethane and 2-(trans-2-phenylcyclopropyl)propane, and their potential cyclic and acyclic products from oxidation at the cyclopropylcarbinyl position were synthesized and tested. Oxidation of both of these probes at the cyclopropylcarbinyl position by CPO gave unrearranged alcohol products only, but control experiments again demonstrated that the rearranged alcohol products were unstable toward CPO oxidation conditions. From the combination of the probe and control studies, the lifetime of a putative radical intermediate must be less than 3 ps. Whereas the results are consistent with an insertion mechanism for production of alcohol product, they do not exclude a very short-lived intermediate.

  16. Thermal degradation reaction mechanism of xylose: A DFT study

    NASA Astrophysics Data System (ADS)

    Huang, Jinbao; He, Chao; Wu, Longqin; Tong, Hong

    2016-08-01

    The thermal degradation reaction mechanism of xylose as hemicellulose model compound was investigated by using density functional theory methods M062X with the 6-31++G(d,p) basis set. Eight possible pyrolytic reaction pathways were proposed and the standard kinetic and thermodynamic parameters in all reaction pathways were calculated at different temperatures. In reaction pathway (1), xylose is first transformed into acyclic containing-carbonyl isomer, and then the isomer further decomposes through four possible pyrolysis pathways (1-1)-(1-4). Pathways (2) and (3) depict an immediate ring-opening process through the simultaneous breaking of C-O and C-C bonds. Pathways (4)-(7) describe the pyrolysis processes of various anhydro-xyloses through a direct ring-opening process. Pathway (8) gives the evolutionary process of pyranones. The calculation results show that reaction pathways (1), (2) and (5) are the major reaction channels and reaction pathways (3), (4), and (6)-(8) are the competitive reaction channels in pyrolysis of xylose. The major products of xylose pyrolysis are low molecular products such as 2-furaldehyde, glycolaldehyde, acetaldehyde, methylglyoxal and acetone, and the main competitive products are formaldehyde, formic acid, acetic acid, CO2, CH4, acetol, pyranone, and so on.

  17. Ion-Molecule Reaction Studies at Low Energies

    NASA Astrophysics Data System (ADS)

    Dheandhanoo, Seksan

    A variable temperature drift tube-mass spectrometer apparatus has been used to determine the forward rate coefficients for the association reactions of NO('+) ions with N(,2) and CO(,2), O(,2)('+) with N(,2), N('+) and N(,2)('+) with N(,2), and CH(,5)('+) and C(,2)H(,5)('+) with CH(,4) as a function of gas temperature. The measured rate coefficients were fitted to power laws of the form k(,+) = C(T/300)(' -x), where the exponents ranged from 2.0 to 4.3, i.e. a strong temperature dependence was observed in most of these three-body (clustering) reactions. The equilibrium constants K = k(,+)/k(,-) for the association reactions of CH(,5)('+) and C(,2)H(,5)('+) with CH(,4) were also measured as a function of gas temperature, allowing the reverse rate coefficients k(,-) for these two reactions to be determined. In a second set of measurements, rate coefficients for several two-body ion-molecule reactions involving hydrocarbons have been determined at thermal energies and above using a selected ion drift tube-mass spectrometer apparatus. The results indicate that the product yields of several of the fast ion-molecule reactions depend on ion energy (temperature), even though the total rate coefficients are independent of energy. The oxidation reaction of the metal ion Zr('+) has been found to be a fast reaction and the rate coefficient has been found to be independent of ion energy.

  18. Modeling study on the cleavage step of the self-splicing reaction in group I introns

    NASA Technical Reports Server (NTRS)

    Setlik, R. F.; Garduno-Juarez, R.; Manchester, J. I.; Shibata, M.; Ornstein, R. L.; Rein, R.

    1993-01-01

    A three-dimensional model of the Tetrahymena thermophila group I intron is used to further explore the catalytic mechanism of the transphosphorylation reaction of the cleavage step. Based on the coordinates of the catalytic core model proposed by Michel and Westhof (Michel, F., Westhof, E. J. Mol. Biol. 216, 585-610 (1990)), we first converted their ligation step model into a model of the cleavage step by the substitution of several bases and the removal of helix P9. Next, an attempt to place a trigonal bipyramidal transition state model in the active site revealed that this modified model for the cleavage step could not accommodate the transition state due to insufficient space. A lowering of P1 helix relative to surrounding helices provided the additional space required. Simultaneously, it provided a better starting geometry to model the molecular contacts proposed by Pyle et al. (Pyle, A. M., Murphy, F. L., Cech, T. R. Nature 358, 123-128. (1992)), based on mutational studies involving the J8/7 segment. Two hydrated Mg2+ complexes were placed in the active site of the ribozyme model, using the crystal structure of the functionally similar Klenow fragment (Beese, L.S., Steitz, T.A. EMBO J. 10, 25-33 (1991)) as a guide. The presence of two metal ions in the active site of the intron differs from previous models, which incorporate one metal ion in the catalytic site to fulfill the postulated roles of Mg2+ in catalysis. The reaction profile is simulated based on a trigonal bipyramidal transition state, and the role of the hydrated Mg2+ complexes in catalysis is further explored using molecular orbital calculations.

  19. Effects of Fenton Reaction on Human Serum Albumin: An In Vitro Study

    PubMed Central

    Khosravifarsani, Meysam; Monfared, Ali Shabestani; Pouramir, Mahdi; Zabihi, Ebrahim

    2016-01-01

    Introduction Human serum albumin (HSA) is a critical protein in human blood plasma, which can be highly damaged by oxidative stress. The aim of this study was to analyze modifications of this protein after oxidation using a Fenton system. Methods In this 2015 experiment, different ratios of Fenton reagent (Fe2+/H2O2) was incubated with one concentration of human serum albumin (1mg/ml). Hence, HSA was incubated 30 min with various combinations of a Fenton system and quantified oxidation products such as carbonyl groups, fragmentations, degradations, and oxidized free thiol group using reliable techniques. Image and data analysis were carried out using ImageJ software and Excel (version 2007), respectively. Results An SDS-PAGE profile showed no cross link and aggregation. However, protein band intensity has decreased to 50% in the highest ratio of H2O2/Fe. Carbonylation assay indicated carbonyl/protein (molc/molp) ratio increased linearly in lower ratios and the values plateau at higher levels of H2O2/Fe 2+. The only free sulfhydryl group on HSA was oxidized in all ratios of the Fenton system. Conclusion To sum, the structure of HSA has been changed following treatment with Hydroxyl Radical as the main product of Fenton reaction. These data confirm the antioxidant activity of HSA. PMID:27790352

  20. Excitation energy dependence of fragment-mass distributions from fission of 180,190Hg formed in fusion reactions of 36Ar + 144,154Sm

    SciTech Connect

    Nishio, K.; Andreyev, A. N.; Chapman, R.; Derkx, X.; Düllmann, Ch. E.; Ghys, L.; Heßberger, F. P.; Hirose, K.; Ikezoe, H.; Khuyagbaatar, J.; Kindler, B.; Lommel, B.; Makii, H.; Nishinaka, I.; Ohtsuki, T.; Pain, S. D.; Sagaidak, R.; Tsekhanovich, I.; Venhart, M.; Wakabayashi, Y.; Yan, S.

    2015-06-30

    Mass distributions of fission fragments from the compound nuclei 180Hg and 190 Hg formed in fusion reactions 36Ar + 144 Smand 36Ar + 154Sm, respectively, were measured at initial excitation energies of E*(180Hg) = 33-66 MeV and E*(190Hg) = 48-71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses $\\overline{A}_L$/$\\overline{A}_H$ = 79/101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+/EC-delayed fission of 180Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of$\\overline{A}_L$/$\\overline{A}_H$ = 83/107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. In conclusion, this behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.

  1. Fragment screening and HIV therapeutics.

    PubMed

    Bauman, Joseph D; Patel, Disha; Arnold, Eddy

    2012-01-01

    Fragment screening has proven to be a powerful alternative to traditional methods for drug discovery. Biophysical methods, such as X-ray crystallography, NMR spectroscopy, and surface plasmon resonance, are used to screen a diverse library of small molecule compounds. Although compounds identified via this approach have relatively weak affinity, they provide a good platform for lead development and are highly efficient binders with respect to their size. Fragment screening has been utilized for a wide range of targets, including HIV-1 proteins. Here, we review the fragment screening studies targeting HIV-1 proteins using X-ray crystallography or surface plasmon resonance. These studies have successfully detected binding of novel fragments to either previously established or new sites on HIV-1 protease and reverse transcriptase. In addition, fragment screening against HIV-1 reverse transcriptase has been used as a tool to better understand the complex nature of ligand binding to a flexible target.

  2. Nuclear structure and reaction studies at medium energies

    SciTech Connect

    Hoffmann, G.W.; Ray, R.L.

    1990-10-01

    This document constitutes the (1988--1991) technical progress report for the ongoing medium energy physics research program supported by the US Department of Energy through special Research Grant FG05-88ER40444. The experiments discussed are conducted at the Los Alamos National Laboratory's (LANL) Clinton P. Anderson Meson Physics Facility (LAMPF), the Alternating Gradient Synchrotron (AGS) facility of the Brookhaven National Laboratory (BNL), and at the Fermi National Accelerator Laboratory (FNAL). The overall motivation for the work discussed in this document is driven by three main objectives: (1) provide hadron-nucleon and hadron-nucleus scattering data which serve to facilitate the study of effective two-body interactions, test (and possibly determine) nuclear structure, and help study reaction mechanisms and dynamics;(2) provide unique, first-of-a-kind exploratory'' hadron-nucleus scattering data in the hope that such data will lead to discovery of new phenomena and new physics; and (3) perform precision tests of fundamental interactions, such as rare decay searches, whose observation would imply fundamental new physics.

  3. Studies on the runaway reaction of ABS polymerization process.

    PubMed

    Hu, Kwan-Hua; Kao, Chen-Shan; Duh, Yih-Shing

    2008-11-15

    Taiwan has the largest acrylonitrile-butadiene-styrene (ABS) copolymer production in the world. Preventing on unexpected exothermic reactions and related emergency relief hazard is essential in the safety control of ABS emulsion polymerization. A VSP2 (Vent Sizing Package 2) apparatus is capable of studying both normal and abnormal conditions (e.g., cooling failure, mischarge, etc.) of industrial process. In this study, the scenarios were verified from the following abnormal conditions: loss of cooling, double charge of initiator, overcharge of monomer, without charge of solvent, and external fire. An external fire with constant heating will promote higher self-heat rate and this is recommended as the worst case scenario of emulsion polymerization on butadiene. Cooling failure coupled with bulk system of reactant was determined to be the credible worst case in ABS emulsion polymerization. Finally, the emergency vent sizing based on thermokinetics from VSP associated with DIERS methodology were used for evaluating the vent sizing and compared to that of the industrial plants.

  4. A dynamic study of fragmentation and energy loss during high velocity impact

    NASA Technical Reports Server (NTRS)

    Zee, Ralph H.

    1992-01-01

    Research conducted under this contract can be divided into two main areas: hypervelocity (in the range up to 7 km/s) and high velocity (less than 1 km/s). Work in the former was performed at NASA-MSFC using the Light Gas Gun Facility. The lower velocity studies were conducted at Auburn University using the ballistic gun. The emphasis of the project was on the hypervelocity phenomenon especially in the characterization of the debris cloud formed by the primary impact events. Special devices were made to determine the angular distributions of momentum and energy of the debris cloud as a function of impact conditions. After several iteration processes, it was decided to concentrate on the momentum effort. Prototype devices were designed, fabricated, and tested. These devices were based on the conservation of momentum. Distributions of the debris cloud formed were measured by determining the amount of momentum transferred from the debris cloud to strategically placed pendulum measurement devices. The motion of the pendula was monitored using itegrated opto-interrupters. The distribution of momentum in the debris cloud was found to be a strong function of the impact condition. Small projectiles at high velocities were observed to produce finely dispersed debris whereas large projectiles generated discrete particles in the debris. Results also show that the momentum in the forward direction was enhanced due to the impact. This phenomenon of momentum multiplication was also observed in other studies and in computer simulations. It was initially planned to determine the energy distribution using deformation energy in a rod with strain gauges. Results from preliminary studies show that this technique is acceptable but too tedious. A new technique was explored based on measuring the heating effect of the debris cloud using an IR camera. The feasibility and sensitivity was established at Auburn University. This type of energy distribution measurement method can easily be

  5. Reaction mechanism and rate constants of the CH+CH4 reaction: a theoretical study

    NASA Astrophysics Data System (ADS)

    Ribeiro, Joao Marcelo; Mebel, Alexander M.

    2015-07-01

    Ab initio and density functional calculations have been performed to elucidate the mechanism of CH radical insertion into methane. The results show that the reaction can be viewed to occur via two stages. On the first stage, the CH radical approaches methane without large structural changes to acquire proper positioning for the subsequent stage, where H-migration occurs from CH4 to CH, along with a C-C bond formation. Where the first stage ends and the second begins, a tight transition state was located using the B3LYP/6-311G(d,p) and MP4(SDQ)/6-311++G(d,p) methods. Using a rigid rotor - harmonic oscillator approach within transition state theory, we show that at the MP5/6-311++G(d,p)//MP4(SDQ)/6-311++G(d,p) level the calculated rate constants are in a reasonably good agreement with experiment in a broad temperature range of 145-581 K. Even at low temperatures, the insertion reaction bottleneck is found about the location of the tight transition state, rather than at long separations between the CH and CH4 reactants. In addition, high level CCSD(T)-F12/CBS calculations of the remainder of the C2H5 potential energy surface predict the CH+CH4 reaction to proceed via the initial insertion step to the ethyl radical which then can emit a hydrogen atom to form highly exothermic C2H4+H products.

  6. Comparative study of carbonaceous meteoritic fragments by micro-Raman spectroscopy and SEM/EDS.

    NASA Astrophysics Data System (ADS)

    Dall'Asén, AnalíA.; Mittelstaedt, Jacob; Kim, Jin-Sun; Baer, Brandon; Paul, Raka; Gerton, Jordan; Bromley, Benjamin; Kenyon, Scott

    2017-01-01

    Meteorites provide precious clues about the formation of planets in the solar system. In particular, carbonaceous chondritic meteorites, considered the most primitive surviving materials from the early Solar System, can contribute to understand how planetisimals (the precursors to planets, of 1-100 km in radius) formed from dust (micron-size grains). These relics are mainly composed of chondrules (micro/millimeter-sized inclusions) surrounded by a matrix of microparticles. Here we present a comparative study of the structure and composition of the chondrules and surrounding matrix of different carbonaceous chondritic meteorites using low- and high-resolution micro-Raman spectroscopy and SEM/EDS (Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy). We examine how these properties vary in different regions of the chondrules and matrix, capturing details from micrometer to millimeter scales. We compare the structure and composition between different samples, looking for signatures of the physical processes that drove their formation.

  7. Copper(II) complexes of prion protein PEG11-tetraoctarepeat fragment: spectroscopic and voltammetric studies.

    PubMed

    Bonomo, Raffaele P; Di Natale, Giuseppe; Rizzarelli, Enrico; Tabbì, Giovanni; Vagliasindi, Laura I

    2009-04-14

    Spectroscopic (UV-Vis and EPR) and voltammetric studies have been carried out on the copper(II) complexes with the Ac-PEG11-(PHGGGWGQ)4-NH2 (L) polypeptide. In the ratios Cu : L 3 : 1 and 4 : 1, the two [Cu3(L)H(-6)] and [Cu4(L)H(-8)] complex species have been characterized at neutral pH values. All the copper atoms occupy similar coordination sites formed by imidazole, peptidic nitrogen atoms and carbonyl oxygen atoms in a square base pyramidal geometry. Voltammetric measurements on these systems point out the cooperativity in the electron transfer processes among the copper(II) sites during their reduction. NO interaction with these polynuclear copper species is characterized by the reduction of the copper sites through the formation of two different intermediate complex species. When an excess of the Ac-PEG11-(PHGGGWGQ)4-NH2 ligand is considered, frozen solution EPR parameters and UV-Vis spectroscopic data identify the [Cu(N(im))4]2+ chromophore, which does not interact with NO.

  8. [Spectroscopic study on the combustion reaction characteristics of methylcyclohexane].

    PubMed

    Li, Cong-Shan; Li, Ping; Zhang, Chang-Hua; Nie, Xiao-Fei; Li, Xiang-Yuan

    2011-09-01

    Using a measurement system consisting of monochromators, photomultiplier tubes, piezoelectric pressure sensors and a digital oscilloscope, characteristic emissions of intermediate products OH, CH and C2 produced in the combustion reaction of methylcyclohexane were measured behind reflected shock waves in a shock tube, and ignition delay times of methylcyclohexane/ oxygen/argon were acquired. Experimental conditions cover temperatures from 1 164 to 1 566 K, pressures from 1.03 to 1.99 atm, a fuel concentration of 1.0%, and an equivalence ratio of 1.0. Combustion reaction characteristics of methylcyclohexane were obtained qualitatively by analyzing emissions from intermediate products OH, CH and C2. The measured ignition delay times agree with available experimental data and the prediction of a combustion reaction mechanism. Current work provides experimental data for constructing and validating the combustion reaction mechanism of methylcyclohexane.

  9. Fragment-guided approach to incorporating structural information into a CoMFA study: BACE-1 as an example

    NASA Astrophysics Data System (ADS)

    Salum, Lívia Barros; Valadares, Napoleão Fonseca

    2010-10-01

    Alzheimer's disease is an ultimately fatal neurodegenerative disease, and BACE-1 has become an attractive validated target for its therapy, with more than a hundred crystal structures deposited in the PDB. In the present study, we present a new methodology that integrates ligand-based methods with structural information derived from the receptor. 128 BACE-1 inhibitors recently disclosed by GlaxoSmithKline R&D were selected specifically because the crystal structures of 9 of these compounds complexed to BACE-1, as well as five closely related analogs, have been made available. A new fragment-guided approach was designed to incorporate this wealth of structural information into a CoMFA study, and the methodology was systematically compared to other popular approaches, such as docking, for generating a molecular alignment. The influence of the partial charges calculation method was also analyzed. Several consistent and predictive models are reported, including one with r 2 = 0.88, q 2 = 0.69 and r pred 2 = 0.72. The models obtained with the new methodology performed consistently better than those obtained by other methodologies, particularly in terms of external predictive power. The visual analyses of the contour maps in the context of the enzyme drew attention to a number of possible opportunities for the development of analogs with improved potency. These results suggest that 3D-QSAR studies may benefit from the additional structural information added by the presented methodology.

  10. Studies of exotic nuclear reactions at the RESOLUT facility

    NASA Astrophysics Data System (ADS)

    Wiedenhoever, Ingo

    2016-09-01

    The RESOLUT facility at Florida State University's accelerator laboratory produces beams of short-lived nuclei using the in-flight method. Beams such as 6He, 7Be, 8Li, 8B, 17F, 19O, 18Ne and 25Al have been successfully used in experiments. The facility has been used to develop innovative experimental techniques, such as the low-energy neutron detector RESONEUT, and the active-target detector ANASEN, which has been developed as a collaboration between FSU and LSU. These detectors have been employed in direct and indirect reaction measurements with impact on astrophysics. An Indiana-University led campaign studying fusion cross sections of exotic nuclei at RESOLUT has also been successful. The results from these three recent RIB campaigns at RESOLUT will be summarized. This work was supported by NSF under Grants Nos. PHY-1401574, PHY-0820941 and PHY-1126345 and by DOE under Grant Nos. DE-FG02-02ER41220, DE-FG02-88ER-40404 and DE-FG02-96ER40978.

  11. Quantum dynamics study of H + DBr and D + HBr reaction.

    PubMed

    Zhang, Ai Jie; Jia, JianFeng; Wu, Hai Shun; He, Guo Zhong

    2014-09-01

    Time-dependent quantum wave packet calculations have been performed for the H + DBr and D + HBr reaction using the recent diabatic potential energy surfaces. Reaction probabilities, integral cross sections, and rate constants are obtained. The results show that the isotopic effects have an influence on the nonadiabatic effect which is generally inversely proportional to the atom mass. The calculated rate constants are in good overall agreement with experimental values, indicating that the ab initio surfaces are accurate to describe the isotopic effects.

  12. Multicomponent linchpin couplings. Reaction of dithiane anions with terminal epoxides, epichlorohydrin, and vinyl epoxides: efficient, rapid, and stereocontrolled assembly of advanced fragments for complex molecule synthesis.

    PubMed

    Smith, Amos B; Pitram, Suresh M; Boldi, Armen M; Gaunt, Matthew J; Sfouggatakis, Chris; Moser, William H

    2003-11-26

    The development, application, and advantages of a one-flask multicomponent dithiane linchpin coupling protocol, over the more conventional stepwise addition of dithiane anions to electrophiles leading to the rapid, efficient, and stereocontrolled assembly of highly functionalized intermediates for complex molecule synthesis, are described. Competent electrophiles include terminal epoxides, epichlorohydrin, and vinyl epoxides. High chemoselectivity can be achieved with epichlorohydrin and vinyl epoxides. For vinyl epoxides, the steric nature of the dithiane anion is critical; sterically unencumbered dithiane anions afford S(N)2 adducts, whereas encumbered anions lead primarily to SN2' adducts. Mechanistic studies demonstrate that the SN2' process occurs via syn addition to the vinyl epoxide. Integration of the multicomponent tactic with epichlorohydrin and vinyl epoxides permits the higher-order union of four and five components.

  13. Fragmentation functions in nuclear media

    NASA Astrophysics Data System (ADS)

    Sassot, Rodolfo; Stratmann, Marco; Zurita, Pia

    2010-03-01

    We perform a detailed phenomenological analysis of how well hadronization in nuclear environments can be described in terms of effective fragmentation functions. The medium modified fragmentation functions are assumed to factorize from the partonic scattering cross sections and evolve in the hard scale in the same way as the standard or vacuum fragmentation functions. Based on precise data on semi-inclusive deep-inelastic scattering off nuclei and hadron production in deuteron-gold collisions, we extract sets of effective fragmentation functions for pions and kaons at next-to-leading order accuracy. The obtained sets provide a rather accurate description of the kinematical dependence of the analyzed cross sections and are found to differ significantly from standard fragmentation functions both in shape and magnitude. Our results support the notion of factorization and universality in the studied nuclear environments, at least in an effective way and within the precision of the available data.

  14. CH 1 Introduction to Chemistry. Study Guide to Minicourse I - 13 Chemical Reaction Principles.

    ERIC Educational Resources Information Center

    Schlenker, Richard

    Provided is a study guide for an introductory minicourse to the principles of chemical reactions. This written text is designed to accompany a series of audio tapes and 35mm slides which the student studies at his own pace. The course presents chemical kinetics, reaction mechanisms, reaction rates, and equilibrium. (SL)

  15. Nuclear-reaction studies via the observation of unbound outgoing systems

    SciTech Connect

    Bice, A.N.

    1982-01-01

    The mechanisms involved in the production of fast ..cap alpha..-particles in /sup 12/C induced reactions have been investigated for the /sup 12/C + /sup 208/Pb system at bombarding energies of E(/sup 12/C) = 132, 187 and 230 MeV. Absolute cross sections have been determined for the reactions /sup 208/Pb (/sup 12/C, /sup 8/Be (g.s.)), /sup 208/Pb(/sup 12/C, /sup 8/Be (2.94 MeV)) and /sup 208/Pb (/sup 12/C, /sup 12/C* ..-->.. ..cap alpha.. + /sup 8/Be) by double and triple coincidence measurements of the sequential decay ..cap alpha..-particles. Inclusive ..cap alpha..-particle production cross sections were also measured at E (/sup 12/C) = 187 MeV for comparison. It is found that the simple inelastic scattering process (/sup 12/C, /sup 12/C* ..-->.. ..cap alpha.. + /sup 8/Be) does not contribute significantly to the production of fast ..cap alpha..-particles but that the production of /sup 8/Be nuclei by projectile fragmentation is an important source of ..cap alpha..-particles. At the highest bombarding energy investigated (19 MeV/A) it appears that the /sup 12/C ..-->.. 3..cap alpha.. fragmentation reaction becomes more prominent at the expense of the /sup 12/C ..-->.. ..cap alpha.. + /sup 8/Be fragmentation channel. It is concluded that projectile spectroscopic properties and/or final state interactions are important in fragmentation reactions for these bombarding energies. In a kinematically complete experiment the direct and the sequential breakup channels of 10 MeV/A /sup 7/Li projectiles have been investigated with /sup 12/C and /sup 208/Pb targets. By appropriate arrangement of detector telescopes it was possible to define a kinematical window which allowed for the unambigious observation of both the direct (to the ..cap alpha..-t continuum) and the sequential components of a heavy-ion projectile breakup reaction. A semiclassical Monte Carlo type projectile breakup calculation was constructed which qualitatively reproduced the measured ..cap alpha

  16. Neutron-induced reactions in the hohlraum to study reaction in flight neutrons

    NASA Astrophysics Data System (ADS)

    Boswell, M. S.; Elliott, S. R.; Guiseppe, V.; Kidd, M.; Rundberg, B.; Tybo, J.

    2013-04-01

    We are currently developing the physics necessary to measure the Reaction In Flight (RIF) neutron flux from a NIF capsule. A measurement of the RIF neutron flux from a NIF capsule could be used to deduce the stopping power in the cold fuel of the NIF capsule. A foil irradiated at the Omega laser at LLE was counted at the LANL low-background counting facility at WIPP. The estimated production rate of 195Au was just below our experimental sensitivity. We have made several improvements to our counting facility in recent months. These improvements are designed to increase our sensitivity, and include installing two new low-background detectors, and taking steps to reduce noise in the signals.

  17. Feasibility study of the Fab fragment of a monoclonal antibody against tissue factor as a diagnostic tool.

    PubMed

    Tsumura, Ryo; Sato, Ryuta; Furuya, Fumiaki; Koga, Yoshikatsu; Yamamoto, Yoshiyuki; Fujiwara, Yuki; Yasunaga, Masahiro; Matsumura, Yasuhiro

    2015-12-01

    Tissue factor (TF) is expressed strongly in various types of cancer, especially cancers that are often refractory to treatment, such as pancreatic cancer. In this study, we compared the differences in the biophysical and pharmacological properties of whole IgG and the Fab fragment of anti-human TF monoclonal antibody (1849 antibodies), in order to determine their suitability for application in the diagnosis and treatment of cancers. In the biophysical examination, we investigated the characteristics of 1849-whole IgG and 1849-Fab by SPR sensing and confocal fluorescence microscopy analysis using recombinant human TF antigen and TF-overexpressing human pancreatic cancer cell line, BxPC3, respectively. After conjugation with Alexa-Flour-647, in vivo imaging was conducted in mice bearing BxPC3 xenograft tumors. Furthermore, the distribution of the conjugates in tumors and major organs was evaluated by ex vivo study. The in vitro experiments showed that 1849 antibodies had high affinity against TF antigen. In addition, 1849-Fab showed a faster dissociation rate from the antigen than 1849-whole IgG. In mice, 1849-Fab-Alexa-Flour-647 showed rapid renal clearance and faster tumor accumulation, achieving a high contrast signal over nearby normal tissues in the early phase and enhanced tumor penetration after administration. On the other hand, 1849-whole IgG-Alexa-Flour-647 showed slow clearance from the blood and sustained high tumor accumulation. These results suggest that 1849-Fab may be a useful tool for pancreatic cancer diagnosis.

  18. Studies of nuclear reaction at very low energies

    SciTech Connect

    Cecil, F.E.

    1992-01-15

    The deuteron radiative capture reactions on {sup 2}H, {sup 6}Li and {sup 10}B have been measured between center of mass energies of 20 and 140 keV. Of note is the observation that the gamma ray-to-charged particle branching ratio for the DD reaction appears independent of energy down to a center of mass energy of 20 keV, consistent with some and contrary to other theoretical models. We have investigated the ratio of the reactions D(d,p)T and D(d,n){sup 3}He down to c.m. energies of 3 keV and the ratio of the reactions 6Li(d,p){sup 7}Li and {sup 6}LI(d,{alpha}){sup 4}He down to a c.m. energy of 19 keV. The DD reaction ratio is independent of energy while the (d,p) branch of the D-{sup 6}Li evinces a significant enhancement at the lowest measured energies. We have continued our investigation of charged particle production from deuterium-metal systems at a modest level of activity. Noteworthy in this investigation is the observation of 3 MeV protons from deuteron beam loaded Ti and LiD targets subjected to extreme thermal disequilibria. Significant facility improvements were realized during the most recent contract period. Specifically the downstream magnetic analysis system proposed to eliminate beam induced contaminants has been installed and thoroughly tested. This improvement should allow the D(a,{gamma}){sup 6}Li reaction to be measured in the coming contract period. A scattering chamber required for the measurement of the {sup 7}Li({sup 3}He,p){sup 9}Be reaction has been designed, fabricated and installed on the accelerator. A CAMAC based charged particle identification system has been assembled also for use in our proposed measurement of the {sup 7}Li({sup 3}He, p){sup 9}Be.

  19. Collision of comet Shoemaker-Levy 9 with Jupiter: impact study of two fragments from the timing of precursor events.

    NASA Astrophysics Data System (ADS)

    Sekanina, Z.

    1996-10-01

    The impacts of fragments K and R of comet Shoemaker-Levy 9 are examined with the aims to interpret the timing of the observed precursors to the main thermal emission event and to correlate the results of ground-based infrared observations with a variety of observations made onboard the Galileo spacecraft. Analysis of the phenomena associated with the impact and explosion of fragment K shows that there is no discrepancy in the timing of the Earth- and Galileo-based observations and that the time of 53+/-3 seconds between the emission peak of Precursor 1 and the onset of Precursor 2, as recorded by terrestrial observers, can be interpreted as the interval between the impactor's disappearance behind the Jovian limb and the first appearance of the ejecta's plume over the limb following the explosion of the fragment's residual mass. It is concluded that the impactor exploded at an altitude of 45 to 50km above the pressure level of 1 bar and that the residual mass involved in the explosion, approximately 6 to 7million tons and about 400meters across, represented only a fraction of 1percent of the fragment's preatmospheric mass. The explosion is calculated to have taken place under a dynamic pressure of several hundred bars and the explosion energy is found to have been on the order of 10^26^erg. The results for fragment R show it to be smaller and less massive than fragment K, exploding slightly higher in the Jovian stratosphere, 50-60km above 1bar. Most of the entry kinetic energy of either impactor was rapidly dissipated during atmospheric flight by prolific mass ablation - dominated by the object's fragmentation - before the point of explosion was reached. The rate of ablation of these massive fragments was comparable with that observed in the Earth's atmosphere for category IIIb fireballs, which belong to the population of "soft" cometary material and whose bulk density was determined to be typically 0.2g/cm^3^. Vigorous fragmentation - both continuous and occurring

  20. IS PROTOSTELLAR HEATING SUFFICIENT TO HALT FRAGMENTATION? A CASE STUDY OF THE MASSIVE PROTOCLUSTER G8.68-0.37

    SciTech Connect

    Longmore, S. N.; Pillai, T.; Keto, E.; Zhang, Q.; Qiu, K.

    2011-01-10

    If star formation proceeds by thermal fragmentation and the subsequent gravitational collapse of the individual fragments, how is it possible to form fragments massive enough for O and B stars in a typical star-forming molecular cloud where the Jeans mass is about 1 M{sub sun} at the typical densities (10{sup 4} cm{sup -3}) and temperatures (10 K)? We test the hypothesis that a first generation of low-mass stars may heat the gas enough that subsequent thermal fragmentation results in fragments {>=}10 M{sub sun}, sufficient to form B stars. We combine ATCA and Submillimeter Array observations of the massive star-forming region G8.68-0.37 with radiative transfer modeling to derive the present-day conditions in the region and use this to infer the conditions in the past, at the time of core formation. Assuming that the current mass/separation of the observed cores equals the fragmentation Jeans mass/length and the region's average density has not changed requires the gas temperature to have been 100 K at the time of fragmentation. The postulated first generation of low-mass stars would still be around today, but the number required to heat the cloud exceeds the limits imposed by the observations. Several lines of evidence suggest the observed cores in the region should eventually form O stars yet none have sufficient raw material. Even if feedback may have suppressed fragmentation, it was not sufficient to halt it to this extent. To develop into O stars, the cores must obtain additional mass from outside their observationally defined boundaries. The observations suggest that they are currently fed via infall from the very massive reservoir ({approx}1500 M{sub sun}) of gas in the larger parsec scale cloud around the star-forming cores. This suggests that massive stars do not form in the collapse of individual massive fragments, but rather in smaller fragments that themselves continue to gain mass by accretion from larger scales.

  1. Accuracy of embedded fragment calculation for evaluating electron interactions in mixed valence magnetic systems: study of 2e-reduced lindqvist polyoxometalates.

    PubMed

    Suaud, Nicolas; López, Xavier; Ben Amor, Nadia; Bandeira, Nuno A G; de Graaf, Coen; Poblet, Josep M

    2015-02-10

    Accurate quantum chemical calculations on real-world magnetic systems are challenging, the inclusion of electron correlation being the bottleneck of such task. One method proposed to overcome this difficulty is the embedded fragment approach. It tackles a chemical problem by dividing it into small fragments, which are treated in a highly accurate way, surrounded by an embedding included at an approximate level. For the vast family of medium-to-large sized polyoxometalates, two-electron-reduced systems are habitual and their magnetic properties are interesting. In this paper, we aim at assessing the quality of embedded fragment calculations by checking their ability to reproduce the electronic spectra of a complete system, here the mixed-metal series [MoxW6-xO19](4-) (x = 0-6). The microscopic parameters extracted from fragment calculations (electron hopping, intersite electrostatic repulsion, local orbital energy, etc.) have been used to reproduce the spectra through model Hamiltonian calculations. These energies are compared to the results of the highly accurate ab initio difference dedicated configuration interaction (DDCI) method on the complete system. In general, the model Hamiltonian calculations using parameters extracted from embedded fragments nearly exactly reproduce the DDCI spectra. This is quite an important result since it can be generalized to any inorganic magnetic system. Finally, the occurrence of singlet or triplet ground states in the series of molecules studied is rationalized upon the interplay of the parameters extracted.

  2. Catalytic reactions of titanium alkoxides with Grignard reagents and imines: a mechanistic study.

    PubMed

    Kumar, Akshai; Samuelson, Ashoka G

    2010-08-02

    The reactivity of Grignard reagents towards imines in the presence of catalytic and stoichiometric amounts of titanium alkoxides is reported. Alkylation, reduction, and coupling of imines take place. Whereas reductive coupling is the major reaction in stoichiometric reactions, alkylation is favored in catalytic reactions. Mechanistic studies clearly indicate that intermediates involved in the two reactions are different. Catalytic reactions involve a metal-alkyl complex. This has been confirmed by reactions of deuterium-labeled substrates and different alkylating agents. Under the stoichiometric conditions, however, titanium olefin complexes are formed through reductive elimination, probably through a multinuclear intermediate.

  3. High temperature chemical kinetic study of the H2-CO-CO2-NO reaction system

    NASA Technical Reports Server (NTRS)

    Jachimowski, C. J.

    1975-01-01

    An experimental study of the kinetics of the H2-CO-CO2-NO reaction system was made behind incident shock waves at temperatures of 2460 and 2950 K. The overall rate of the reaction was measured by monitoring radiation from the CO + O yields CO2 + h upoilon reaction. Correlation of these data with a detailed reaction mechanism showed that the high-temperature rate of the reaction N + OH yields NO + H can be described by the low-temperature (320 K) rate coefficient. Catalytic dissociation of molecular hydrogen was an important reaction under the tests conditions.

  4. Characterization of nitrogen-fixing Paenibacillus species by polymerase chain reaction-restriction fragment length polymorphism analysis of part of genes encoding 16S rRNA and 23S rRNA and by multilocus enzyme electrophoresis.

    PubMed

    Coelho, Marcia Reed Rodrigues; von der Weid, Irene; Zahner, Viviane; Seldin, Lucy

    2003-05-28

    Forty-two strains representing the eight recognized nitrogen-fixing Paenibacillus species and 12 non-identified strains were examined by restriction fragment length polymorphism (RFLP) analysis of part of 16S and 23S rRNA genes amplified by polymerase chain reaction (PCR). Eleven different 16S rDNA genotypes were obtained from the combined data of RFLP analysis with four endonucleases and they were in agreement with the established taxonomic classification. Only one group of unclassified strains (Group I) was assigned in a separate genotype, suggesting they belong to a new species. Using the 23S PCR-RFLP method only six genotypes were detected, showing that this method is less discriminative than the 16S PCR-RFLP. Using the multilocus enzyme electrophoresis (MLEE) assay, the 48 strains tested could be classified into 35 zymovars. The seven enzymatic loci tested were polymorphic and the different profiles obtained among strains allowed the grouping of strains into 10 clusters. The PCR-RFLP methods together with the MLEE assay provide a rapid tool for the characterization and the establishment of the taxonomic position of isolates belonging to this nitrogen-fixing group, which shows a great potentiality in promoting plant growth.

  5. Accretion of a Small Continental Fragment to a Larger Continental Plate: Mesozoic Ecuador as a Case-Study Area