325,023 research outputs found
Influence of modifiers on Palladium based nanoparticles for room temperature formic acid decomposition
No full textHeterogeneous catalysts form a highly important part of everyday life, ranging from the production of fertiliser enabling the growth of crops that sustain much of the world's population to the production of synthetic fuels. They constitute a key part of the chemical industry and contribute towards substantial economic and environmental benefits. Heterogeneous catalysts are also believed to have an important role to play in a future hydrogen economy, reducing our requirements for fossil fuels. To this end, formic acid has been proposed as a potential hydrogen storage material for small portable devices. Additionally, formic acid has historically been used as a probe molecule to study catalyst materials and recent developments in the knowledge of its decomposition pathways and the preferred sites of these reactions, establish a good foundation for further study. This work explores a range of novel modification techniques that alter the activity of Pd nanoparticles to decompose formic acid to H2 and CO2. The methods used are the addition of polymers, attaching various functional groups to the surface of the catalyst support and decoration of nanoparticles with sub-monolayer coverages of another metal. Using a range of characterisation methods including FTIR of an adsorbed CO probe, XRD and XPS coupled with computational modelling, it is found that these methods result in some significant electronic and/or geometric alterations to the Pd nanoparticles. For polymer modification, the nature of the pendent group is highly important in determining the effects of the polymer on the Pd particles, with all the tested polymers resulting in varying degrees of electronic donation to the Pd surface. The geometric modifications caused by the polymers also varied with pendent groups; with amine containing pendent groups found to selectively block low coordinate sites, preventing the undesired dehydration of formic acid which results in poisoning of the Pd catalyst by the resulting CO. Attachment of amine groups to the surface of metal oxide catalyst supports, is demonstrated to result in dramatic electronic promotional effects to the supported Pd nanoparticles, and when an amine polymer is attached to the support surface the geometric modification is again observed. Finally decoration of Pd nanoparticles with a sub-monolayer coverage of a second metal is examined, resulting in some similar electronic and geometric effects on Pd nanoparticle surfaces to those observed with polymer modification with corresponding changes in formic acid decomposition activity. Overall, a number of methods are displayed to tune the catalytic activity and selectivity of Pd nanoparticles for formic acid decomposition, resulting in catalysts with some of the highest reported TOF's at room temperature. These modification methods are believed to be potentially applicable to a wide range of other catalytic reactions that operate under mild conditions
Single molecule dynamics
No full textProperties found in an ensemble of molecules may not be understood if it is not possible to study each molecule one by one. This thesis is concerned with the study of the dynamic properties of individual complex biological molecules as observed by confocal single-molecule fluorescence spectroscopy. Single molecules are studied under conditions that are biologically relevant; in aqueous solution at room temperature.Single DNA molecules upon which a fluorescence sensor is attached (tetrahethylrhodmine, TMR) are detected freely diffusing in solution as well as immobilized in solution. Conformational movements of single species of DNA-TMR induce intramolecular spectroscopic fluctuations. The dynamics of the spectroscopic fluctuations of single DNA-TMR molecules are not ergodic on the observed time scale. The histogram of the transition rates of many single molecules is similar to the distribution of exponential functions leading to stretched exponential transition kinetics found in the ensemble. These results imply that the phase space of the DNA-TMR may be divided into components in which each DNA-TMR molecule becomes trapped on the observed time scale.The enzyme-product complex of single horseradish peroxidase enzyme molecules catalysing the oxidation of dihydrorhodamine 6G (substrate) into rhodamine 6G (product) is observed. While the dissociation of the enzyme-product complex show exponential kinetics, the rate at which the enzyme-product complex is formed show a broad distribution. The data and analysis indicate that substrate interaction with the enzyme select a set of conformational substates (CS) for which the enzyme is active.The quantity of information (combinations of different methodologies to measure a single molecule, for example) as well as the quality in the analysis of the information (higher order correlation analysis, for example) set the limits of future analyses of single molecule dynamics.List of scientific papersI. Edman L, Mets Ü, Rigler R (1995). Revelation of intramolecular transitions in single molecules in solution. Experimental Technique of Physics. 41: 157-163.II. Edman L, Mets Ü, Rigler R (1996). Conformational transitions monitored for single molecules in solution. Proc Natl Acad Sci U S A. 93(13): 6710-6715. https://doi.org/10.1073/pnas.93.13.6710III. Wennmalm S, Edman L, Rigler R. (1997). Conformational fluctuations in single DNA molecules. Proc Natl Acad Sci U S A. 94(20): 10641-10646. https://doi.org/10.1073/pnas.94.20.10641IV. Edman L, Wennmalm S, Tamsen F, Rigler R (1998). Heterogeneity in single DNA conformational fluctuations. Chemical Physics Letters. 292: 15-21. https://doi.org/10.1016/S0009-2614(98)00633-2V. Wennmalm S, Edman L, Rigler R (1999). Non-ergodic behaviour in conformational transitions of single DNA molecules. Chemical Physics. 247: 61-67. https://doi.org/10.1016/S0301-0104(99)00125-1VI. Edman L, Földes-Papp Z, Wennmalm S, Rigler R (1999). The fluctuating enzyme: a single molecule approach. Chemical Physics. 247: 11-22. https://doi.org/10.1016/S0301-0104(99)00098-1VII. Edman L, Rigler R. Memory landscapes of single enzyme molecules. [Manuscript]</p
D. D. Arbor toxicaria Macassariensis. Quam venia exp. Fac. Med. Upsal. / Praeside Carol. Pet. Thunberg, [...] Pro gradu doctoris Publico Subjicit Examini Christen Aejmelaeus, Fenno in audit. Gust. Maj. d. XXI maj MDCCLXXXVIII. H. A. et. P. M. S.
No full textProcede de la Biblioteca de la Facultad de FarmaciaEx-libris ms: "Dr. Abbas Pourret"Año de imp. deducido de la fecha del títuloColección de 16 disertaciones académicas presididas por Carl Peter Thunberg, presumiblemente publicadas entre el 1781 y el 1801Enc. PastaSign.: [ ]1, A4, B
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The ABRF Edman Sequencing Research Group 2008 Study: investigation into homopolymeric amino acid N-terminal sequence tags and their effects on automated Edman degradation
No full textThe Edman Sequence Research Group (ESRG) of the Association of Biomolecular Resource designs and executes interlaboratory studies investigating the use of automated Edman degradation for protein and peptide analysis. In 2008, the ESRG enlisted the help of core sequencing facilities to investigate the effects of a repeating amino acid tag at the N-terminus of a protein. Commonly, to facilitate protein purification, an affinity tag containing a polyhistidine sequence is conjugated to the N-terminus of the protein. After expression, polyhistidine-tagged protein is readily purified via chelation with an immobilized metal affinity resin. The addition of the polyhistidine tag presents unique challenges for the determination of protein identity using Edman degradation chemistry. Participating laboratories were asked to sequence one protein engineered in three configurations: with an N-terminal polyhistidine tag; with an N-terminal polyalanine tag; or with no tag. Study participants were asked to return a data file containing the uncorrected amino acid picomole yields for the first 17 cycles. Initial and repetitive yield (R.Y.) information and the amount of lag were evaluated. Information about instrumentation and sample treatment was also collected as part of the study. For this study, the majority of participating laboratories successfully called the amino acid sequence for 17 cycles for all three test proteins. In general, laboratories found it more difficult to call the sequence containing the polyhistidine tag. Lag was observed earlier and more consistently with the polyhistidine-tagged protein than the polyalanine-tagged protein. Histidine yields were significantly less than the alanine yields in the tag portion of each analysis. The polyhistidine and polyalanine protein-R.Y. calculations were found to be equivalent. These calculations showed that the nontagged portion from each protein was equivalent. The terminal histidines from the tagged portion of the protein were demonstrated to be responsible for the high lag during N-terminal sequence analysis
Nova genera plantarum, quorum partem secundam, suffrag. exper. facult. med. Upsal. publice ventilandam exhibent praeses Carol. P. Thunberg ... et respondens Carolus Henr. Salberg ... In audit. Gust. d. 10. julii anno MDCCLXXXII
No full textProcede de la Biblioteca de la Facultad de FarmaciaEx-libris ms: "Dr. Abbas Pourret"Año de imp. deducido de la fecha del títuloColección de 16 disertaciones académicas presididas por Carl Peter Thunberg, presumiblemente publicadas entre el 1781 y el 1801La h. de grab. calc.: "S. N. Casström del."Enc. PastaSign.: π1, E-G
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
D. D. Dissertatio botanica de Moraea. Quam consensu exp. Fac. Med. Upsal. / Praeside Carol. Pet. Thunberg, [...] Publice examinandam sistit Zacharias Colliander, Stipend. Reg. Smolandus. In audit. Gust. Maj. d. VIII. Dec. MDCCLXXXVII. H. A. M. S.
No full textProcede de la Biblioteca de la Facultad de FarmaciaEx-libris ms: "Dr. Abbas Pourret"Año de imp. deducido de la fecha del títuloColección de 16 disertaciones académicas presididas por Carl Peter Thunberg, presumiblemente publicadas entre el 1781 y el 1801Enc. PastaSign.: A-B4, C
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