1,720,957 research outputs found
Development and validation of a stability indicating method for the evaluation of photostability of water soluble vitamins with high performance liquid chromatography
No full textEvaluation of Slovenian waters´ burden with hormones and selected endocrine disruptors
No full textV okviru doktorske naloge smo celovito obravnavali problematiko obremenitve okolja s hormoni in nekaterimi drugimi pomembnimi kemičnimi motilci endokrinega sistema (KMES). Ugotovili smo, da so pomanjkljivi podatki o pojavnosti mnogih spojin in ekotoksikološkem potencialu (EP), še posebej sinteznih steroidov (SS). Na primeru bisfenola B smo pokazali, da je njegov EP podcenjen za vsaj štiri velikostne razrede. Zato smo za vrednotenje pojavnosti v okolju razvili ultra občutljivo analizno metodo za kvantitativno določanje prisotnosti kar 25 različnih KMES iz skupin naravnih hormonov, SS ter bisfenolov. Metodo smo validirali po obsežnem protokolu, ki smo ga predlagali za vpeljavo v validacijo tudi drugih okoljskih analiznih metod. Analizirali smo 36 vzorcev odpadnih in 33 povezanih rečnih vod (RV) in pri tem uspešno kvantificirali 16 KMES, z najvišjimi koncentracijami bisfenolov S, A in F ter estriola in klormadinona. Koncentracije nad priporočenimi varnimi vrednostmi smo določili tudi za estradiol in etinil estradiol. Čistilne naprave so v splošnem uspešne pri odstranjevanju večine KMES, a vseeno dosegajo v povprečju le 36 % uspešno zmanjšanje hormonske aktivnosti. Prisotnost BPA, estradiola, BPS in estrona predstavlja veliko tveganje v večini, prisotnost SS pa v desetini vzorcev RV. V obsežni študiji smo analizirali še 130 vzorcev RV in določili povišanje obremenitve s KMES, ki sledi letnemu ciklu, pri čemer je obremenitev vod pozimi kar šestkrat višja od spomladanske. Pokazali smo tudi, da šest spojin z našega nabora v okolju predstavlja tveganje, ki je višje od visokega tveganja za vsaj dva velikostna razreda. Določili smo tudi, da prisotnost BPS v pitnih vodah predstavlja visoko tveganje v kar dveh tretjinah od 25-ih testiranih vzorcev. Na celični liniji hER?-HeLa-9903 smo ob uporabi modela aditivnih koncentracij (MAK) pokazali, da sledijo estrogenski učinki zmesi MAK, med tem ko okoljski vodni vzorci izkazujejo manjšo učinkovitost od pričakovane. Pokazali smo tudi, da zmes spojin pri koncentracijah, kjer njihov učinek posamezno ni pričakovan, izkazuje merljive učinke. Na primeru modelne spojine noretindrona smo proučevali delovanje treh različnih naprednih oksidacijskih tehnik za razgradnjo in pri tem izvedli še karakterizacijo pretvorbenih produktov (PP), ki v postopku razgradnje nastanejo. Vse tri tehnike so bile učinkovite v zmanjšanju začetne koncentracije noretindrona, a so tretirani vzorci v in vitro testu pokazali zgolj delno znižanje ali celo povišanje estrogenske aktivnosti. Pri tem smo predpostavili in eksperimentalno potrdili nastanek 17-ih PP, za katere smo kot prvi s pomočjo in silico metod pokazali le deloma znižano in tudi povišano estrogensko aktivnost v primerjavi z noretindronom ter potrdili tudi prisotnost sedmih PP v okoljskih vzorcih vod.In the scope of the doctoral thesis, we have comprehensively addressed the issue of environmental pollution with hormones and some other important endocrine disruptor chemicals (EDCs). We found lacking data on the occurrence of many EDCs and their ecotoxicological potential (EP), especially synthetic steroids (SSs). On an example of bisphenol B, we showed that its EP is underestimated by at least four orders of magnitude. Therefore, to evaluate their occurrence in the environment, we have developed an ultra-sensitive analytical method for the quantitative determination of the presence of up to 25 different EDCs from the groups of natural hormones, SSs, and bisphenols. We validated the method according to an extensive protocol, which we also propose for the validation of other environmental analytical methods. We analyzed 36 samples of waste and 33 connected river waters (RW) and successfully quantified 16 EDCs, with the highest concentrations of bisphenols S, A and F, as well as estriol and chlormadinone. Concentrations above the recommended safe values were also determined for estradiol and ethinyl estradiol. Wastewater treatment plants are generally successful in removing most EDCs but achieve on average only 36% reduction in hormonal activity. The presence of BPA, estradiol, BPS and estrone poses a high risk in the majority, and the presence of SS in one tenth of RW samples. In an extensive study, we analyzed another 130 RW samples and determined the increase of EDC burden, which follows an annual cycle, whereby the burden is sixfold higher in winter than in spring. We have also shown that six compounds from our selection pose an environmental risk higher than high risk by at least two orders of magnitude. Additionally, we found that the presence of BPS in drinking water poses a high risk in two-thirds of the 25 samples tested. On the cell line hERα-HeLa-9903, using the additive concentrations model (CAM), we have shown that the estrogenic effects of mixtures follow CAM predictions, while environmental water samples show a lower efficiency than expected. We have also shown that a mixture of compounds at concentrations where their effect is not expected individually, shows measurable effects. Using norethindrone as a model compound, we studied the performance of three different advanced oxidation processes and performed the characterization of transformation products (TPs) that are formed during the degradation processes. All three treatment techniques were effective in reducing the initial concentration of norethindrone, but in vitro, the treated samples showed only a partial decrease or even an increase in estrogenic activity. Therefore, we proposed and experimentally confirmed the formation of 17 TPs, for which we were the first to show only partially reduced and also increased estrogenic activity compared to norethindrone using in silico methods. Additionally, we have confirmed the presence of seven TPs in environmental water samples
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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