1,721,054 research outputs found
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
Development and validation of an analytical method for quantification of topiramate and its metabolites in plasma samples by liquid chromatography coupled with mass spectrometry
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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
Quality control of cosmetic products with copper tripeptide and acetyl hexapeptide-8
No full textPeptidi v kozmetičnih izdelkih postajajo vse bolj priljubljeni predvsem zaradi njihove učinkovitosti in visoke stopnje varnosti. Najpogosteje se uporabljajo v izdelkih za aktivno nego kože s ciljem preprečevanja ali zmanjševanja znakov staranja. Glavni učinki peptidov so podpiranje mehanizmov in celic v koži, odgovornih za antioksidativne procese, upočasnjevanje procesov staranja, vlaženje kože, spodbujanje sinteze kolagena in pospeševanje celjenja ran.
Osrednji cilj diplomske naloge je bil ovrednotiti vsebnost in stabilnost bakrovega tripeptida in acetil heksapeptida-8, dveh aktualnih in pogosto uporabljenih hidrofilnih peptidov, v izbranih kozmetičnih izdelkih ter preveriti skladnost z navedbami na ovojnini. V ta namen smo optimizirali in v skladu s smernicami ICH validirali analizno metodo na osnovi tekočinske kromatografije visoke ločljivosti. Po pregledu trga smo izbrali 9 kozmetičnih izdelkov različnih proizvajalcev in cenovnih razredov, ki so vsebovali vsaj enega izmed izbranih peptidov, pri čemer smo vključili tudi izdelke z navedeno vsebnostjo. Ugotovili smo, da večina izdelkov ne vsebuje navedenih peptidov, še posebej pa izstopa odsotnost acetil heksapeptida 8, saj je bil naveden v 8 izdelkih, a ga nismo zaznali v nobenem od izdelkov. Bakrov tripeptid je bil prisoten v treh od petih kozmetičnih izdelkov, pri čemer je bila v vseh treh tudi navedena točna vsebnost peptida na ovojnini. Ugotovili smo, da se pri teh treh izdelkih vsebnost bakrovega tripeptida zelo dobro ujema, saj so bile dejanske vsebnosti le za 5–20 % višje od navedenih. Izkazalo se je, da cena ni povezana s kakovostjo izdelkov.
Stabilnost izbranih peptidov v kozmetičnih izdelkih smo preverjali s stresnimi, pospešenimi in dolgoročnimi testi. V sklopu pospešenega testiranja smo izbrane izdelke izpostavili povišani temperaturi (40 °C) in relativni vlažnosti (75 %) ter jih analizirali tedensko v obdobju enega meseca. Ugotovili smo, da sta pri teh pogojih oba peptida stabilna, saj so bile vsebnosti skozi čas znotraj intervala sprejemljivosti (100 ± 10 %). Dolgoročno stabilnost bakrovega tripeptida v izdelkih smo preverjali po enem mesecu shranjevanja izdelkov pri sobni temperaturi v originalni ovojnini. Ugotovili smo, da je peptid stabilen tudi pri realnih pogojih uporabe izdelkov, kar kaže, da nestabilnost ni razlog za odsotnost peptidov v testiranih kozmetičnih izdelkih. Na podlagi pridobljenih rezultatov lahko zaključimo, da je na področju kozmetičnih izdelkov, ki vsebujejo aktivne komponente, smiseln oziroma potreben večji nadzor.Peptides in cosmetic products are becoming increasingly popular, mainly due to their efficacy and high level of safety. Peptides are most commonly used in active skincare products to prevent or reduce signs of aging. The main effects of peptides are supporting the mechanisms and cells in the skin responsible for antioxidant processes, slowing down the aging processes, skin hydration, stimulation of collagen synthesis, and acceleration of wound healing.
The main objective of our work was to evaluate the content and stability of copper tripeptide and acetyl hexapeptide-8, two current and frequently used hydrophilic peptides in selected cosmetic products, and to verify compliance with the labelling on the packaging. An analytical method based on high-performance liquid chromatography was optimised, and validated according to ICH guidelines. Following a market research, nine cosmetic products from different manufacturers and price categories were selected, each containing at least one of the selected peptides. Products with declared peptide content were also included. We found that most products did not contain any of the specified peptides. Most notably, acetyl hexapeptide-8 was listed on eight products but was not detected in any of them. Copper tripeptide was detected in three out of five cosmetic products, with all three accurately declaring the peptide content on the packaging. For these three products, the actual copper tripeptide content closely matched the declared values, with measured concentrations being only 5–20% higher than claimed. It was found that price does not correlate with quality of the products.
The stability of the selected peptides in cosmetic products was tested using stress, accelerated and long-term tests. For the accelerated testing, selected products were exposed to elevated temperature (40 °C) and relative humidity (75%) and analysed weekly over a period of one month. We found that both copper tripeptide and acetyl hexapeptide-8 remained stable under accelerated conditions, as their contents remained within the acceptable range (100 ± 10%) throughout the study. The long-term stability of copper tripeptide was evaluated after one month of storage at room temperature in the original packaging. The results confirmed that the peptide remained stable under real-life storage conditions, suggesting that instability is not the reason for the absence of peptides in the tested products. Based on the obtained results, we conclude that greater control is necessary in the field of cosmetic products containing active ingredients
Evaluation of forced degradation stability of some benzodiazepines by high-performance liquid chromatography
No full textEvalaution of oxidative instability of ubidecarenone by hig performance liquid chromatography
No full textDevelopment and validation of an analytical method for quantification of selected pharmaceuticals in surface water samples by liquid chromatography coupled with mass spectrometry
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