1,720,966 research outputs found
Photodissociation of aromatic molecules by coincidence spectroscopy
Get PDFThis thesis presents five studies on the gas-phase photodissociation dynamics of eight aromatic molecules: nimorazole, metronidazole, tetrabromothiophene, diiodothio phene, 2-nitroimidazole, 4-bromo-2-nitroimidazole, 4-bromo-5-nitroimidazole, and 2-bromo-5-iodo-4-nitroimidazole. The work is fundamental research on molecular physics, investigating how the molecules break down following photoionisation.
All the samples were powders at room temperature and atmospheric pressure. The dissociation mechanisms could be studied at the molecular level on isolated molecules by evaporating the samples in a vacuum. Molecules in the gas phase were ionised using UV radiation and X-rays. The ensuing fragmentation processes were then investigated using ion time-of-flight spectroscopy, electron spectroscopy, and coincidence methods.
Two of the articles concern the photodissociation dynamics of thiophenes. Em phasis has been put on analysing certain major fragmentation pathways in detail. The remaining articles focus on nitroimidazoles and aspects of their dissociation dynamics that may explain the radiosensitization properties possessed by some nitroimidazoles. The introductory section of the thesis summarises the publications and covers the theoretical background, experimental details, and research context.
Among the key results are i) an explanation for the difference in radiosensitization efficacy between nimorazole and metronidazole, ii) a dissociation model of dicationic tetrabromothiophene, iii) time-scale information on dissociation of dica tionic diiodothiophene, iv) a conclusion that heavy-element-substituted nitroimida zoles seem potential candidates for bifunctional radiosensitizer drugs from a molec ular physics point of view.ei tietoa saavutettavuudest
Misonidatsolin ja 1-(2,3-epoksipropyyli)-2-nitroimidatsolin fragmentaatio fotoionisaation vaikutuksesta
Get PDFSyövän sädehoidossa syöpäsolujen DNA:han pyritään aiheuttamaan pysyviä vaurioita ionisoivalla säteilyllä, minkä seurauksena solut kuolevat. Koska säteily vaurioittaa myös kasvainta ympäröiviä terveitä soluja, on tärkeää saavuttaa hoidon tavoitteet mahdollisimman pienellä säteilyannoksella. Syöpäkudos on usein niukkahappista solujen hallitsemattoman kasvun johdosta, mikä tekee kudoksesta resistentimmän säteilylle kuin normaalisti hapettuneen kudoksen. Yksi ratkaisu tähän ongelmaan on sädeherkistävien lääkemolekyylien käyttö.
Tässä tutkielmassa tarkasteltiin misonidatsolin ja 1-(2,3-epoksipropyyli)-2-nitroimidatsolin fragmentaatiota valenssikuoren fotoionisaation jälkeen. Molekyyleistä misonidatsoli on tunnettu sädeherkiste. 1-(2,3-epoksipropyyli)-2-nitroimidatsolilla ei tiedetä olevan sädeherkistäviä ominaisuuksia mutta sillä on misonidatsolin tavoin 2-nitroimidatsoli-rakenne. Tutkielman tarkoituksena on vertailla miten eri funktionaaliset ryhmät molekyylien hajoamiseen.
Työn kokeellinen osuudessa näytteille tehtiin kahdenlaisia mittauksia. Molekyylejä tutkittuun ensiksi lentoaikamassaspektrometrian avulla käyttäen eri fotonin energioita. Lisäksi tehtiin koinssidenssimittauksia, joissa havaitaan samaan ionisaatiotapahtumasta lähtevä fotoelektroni ja ioni. Tällöin saadaan tietoa ionisoituneen elektronin alkutilan vaikutuksesta molekyylin hajoamiskanavaan. Tulosten perusteella molemmilla molekyyleillä hajoaminen alkaa usein NO2-ejektiolla, mihin liittyy pieni fotoelektronin sidosenergia. Tätä lukuunottamatta funktionaalisen ryhmän vaihtuminen johtaa hyvin erityyppisiin hajoamiskanaviin ja PEPICO-karttoihin. Tulosten perusteella 1-(2,3-epoksipropyyli)-2-nitroimidatsolilla voi mahdollisesti olla sädeherkistäviä ominaisuuksia kuten misonidatsolillakin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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