131,393 research outputs found
On the Existence of Undominated Elements of Acyclic Relations
No full textWe study the existence of undominated elements of acyclic and irreflexive relations. A sufficient condition for the existence is given in the general case without any topological assumptions. Sufficient conditions are also given when the relation in question is defined on a compact Hausdorff space. We study the existence of fixed points of acyclic correspondences, the existence of stable sets, and the possibility of representing the relation by a real valued function.acyclic relations, undominated elements
Rekombinanttiproteiinien tuotto Lactococcus lactis -bakteerissa – sovelluksena D-tagatoosin tuotto
No full textLactococcus lactis is a commercially attractive host for recombinant protein production with many potential applications, for example, in the food and pharmaceutical industries. Production of recombinant proteins requires a suitable expression system, and the aim of this study was to develop new inducible recombinant protein expression systems for L. lactis. In addition, a special application for a developed expression system in D-tagatose production was investigated. D-Tagatose is a functional low-calorie sweetener, but the production costs still limit its use. Two new protein expression systems were developed, of which the first was based on a phosphate starvation-inducible pstF promoter of L. lactis MG1363. High expression levels of intracellular β-galactosidase (670 µkat g-1) and secreted α-amylase (3.6 μkat l-1) were achieved using this strictly regulated expression system. The other new protein expression system was based on the salt-inducible BusA promoter and the BusR repressor gene of L. lactis MG1363. To achieve salt-inducible protein expression, the BusR expression was adjusted by generating random mutations to its promoter area. In the bioreactor, a 6.0 μkat l-1 α-amylase activity was reached, however, without strict regulation. Inducing agents were not needed with either expression system in the bioreactor. Due to strict regulation and high expression levels, the phosphate starvation-inducible expression system was chosen to overexpress Bifidobacterium longum L-arabinose isomerase. The purified enzyme was characterized, and it turned out to be active and stable at acidic pH (optimum 6.0-6.5), and optimally active at 55 °C. The Km values were 120 mM and 590 mM, and Vmax values were 42 U mg-1 and 7.7 U mg-1, for L-arabinose and D-galactose, respectively. The enzyme bound the metal cofactors (Mg2+, Ca2+) tightly, but the metal ion requirement was low for catalytic activity. Divalent metal ions, preferably Mg2+, were required for enzyme stability at higher temperatures. Because of the promising characteristics of the enzyme and high expression level, the use of resting L. lactis cells harboring B. longum L-arabinose isomerase to produce D-tagatose was investigated. Optimization analysis showed high pH, temperature, and borate concentration favored D-tagatose production. Almost quantitative conversion (92 %) was reached in a borate buffer after five days (20 g l-1 D-galactose, 37.5 °C). D-Tagatose production was also investigated with high substrate concentration (300 g l-1 D-galactose, 1.15 M borate, 41 °C) in a 10-day batch process, changing the production medium every 24 h. A D-tagatose production rate of 185 g l-1 day-1 was achieved, comparable with reported numbers in the literature. The results indicated that the use of resting cells stabilized the enzyme. There was no loss in productivity during the ten sequential batches. To further develop the D-tagatose production process, the cells could be immobilized in a packed-bed bioreactor to enable continuous production. Developing the new expression systems to be food-grade could enable more applications.Lactococcus lactis on kaupallisesti houkutteleva isäntä rekombinanttiproteiinien tuotantoon ja sillä on monia mahdollisia sovelluksia esim. elintarvike- ja lääketeollisuudessa. Rekombinanttiproteiinien tuotanto vaatii sopivan tuottosysteemin, ja tämän tutkimuksen tavoitteena oli kehittää uusia indusoituvia tuottosysteemejä L. lactis -bakteerille. Lisäksi tutkittiin kehitetyn tuottosysteemin soveltuvuutta D-tagatoosin tuotantoon. D-Tagatoosi on vähäkalorinen makeutusaine, jolla on monia terveyshyötyjä, mutta tuotantokustannukset rajoittavat yhä sen käyttöä. Työssä kehitettiin kaksi uutta proteiinintuottosysteemiä, joista ensimmäinen perustui L. lactis MG1363:n pstF-promoottoriin. Käyttämällä tätä tiukasti säädeltyä fosfaatin puutoksesta indusoituvaa tuottosysteemiä saavutettiin korkeat solunsisäisen β-galaktosidaasin (670 µkat g-1) ja erittyvän α-amylaasin (3,6 µkat l-1) tuottotasot. Toinen proteiinintuottosysteemi perustui L. lactis MG1363:n suolaindusoituvaan BusA promoottoriin ja BusR säätelygeeniin. Suolaindusoituvan tuottosysteemin aikaansaamiseksi BusR geenin tuottotasoa säädettiin mutatoimalla sen promoottorialuetta. Tällä tuottosysteemillä saavutettiin bioreaktorissa 6,0 μkat l-1 α-amylaasiaktiivisuus, mutta ilman tiukkaa säätelyä. Indusoivia aineita ei tarvittu bioreaktorissa kummallakaan tuottosysteemillä. Tiukan säätelyn ja korkeiden tuottotasojen vuoksi fosfaatinpuutoksesta indusoituva tuottosysteemi valittiin Bifidobacterium longum L-arabinoosi-isomeraasin tuottoon. Puhdistettu entsyymi karakterisoitiin, ja se osoittautui aktiiviseksi ja stabiiliksi happamassa pH:ssa (optimi 6,0–6,5) ja optimaalisesti aktiiviseksi 55 °C:ssa. Km-arvot olivat 120 mM ja 590 mM ja Vmax-arvot olivat 42 U mg-1 ja 7,7 U mg-1, L-arabinoosille ja D-galaktoosille. Entsyymi sitoi metallikofaktorit (Mg2+, Ca2+) tiukasti, mutta sen metallintarve katalyyttistä aktiivisuutta varten oli alhainen. Metalli-ioneja, erityisesti Mg2+, tarvittiin kuitenkin stabiilisuuteen korkeissa lämpötiloissa. Entsyymin lupaavista ominaisuuksista ja korkeasta tuottotasosta johtuen tutkittiin L-arabinoosi isomeraasia sisältävien L. lactis -solujen käyttöä D-tagatoosin tuottoon. Optimointikoe osoitti, että korkea pH, lämpötila ja boraattipitoisuus suosivat tuottoa. Boraattipuskurissa saavutettiin lähes kvantitatiivinen (92 %) konversio viiden päivän kuluessa (20 g l-1 D-galaktoosi, 37,5 °C). D-Tagatoosin tuottoa tutkittiin myös 10 päivän prosessissa (300 g l-1 D-galaktoosi, 1.15 M boraatti, 41 °C), jossa alusta vaihdettiin uuteen kerran vuorokaudessa. Näin saatiin D-tagatoosin tuottotasoksi 185 g l-1 vrk-1, mikä vertautuu kirjallisuudessa raportoituihin lukuihin. Lepäävien solujen käytöllä oli stabiloiva vaikutus entsyymiin, sillä tuottavuus ei heikentynyt 10 peräkkäisen panoksen aikana. Tuotantoprosessin kehittämiseksi jatkuvatoimiseksi solut voitaisiin vielä immobilisoida pakattuun bioreaktoriin. Uusien tuottosysteemien kehittäminen elintarvikelaatuisiksi voisi mahdollistaa lisää sovelluksia
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
The R&D Tax Incentives
No full textThis article sets out some background information and reflections of the author on the R&D tax incentive schemes included in the Common Corporate Tax Base (CCTB) Proposal. In particular the author analyzes the stimulus to private R&D through ad hoc tax incentives included in the CCTB Proposal and dives into the actual provisions included in the Proposal highlighting the most relevant issues connected with their design and interpretation. Moreover, the author explores the interaction between the CCTB Proposal and the granting by Member States of domestic R&D tax incentives
sj-docx-1-jpc-10.1177_21501319211062672 – Supplemental material for Symptoms COVID 19 Positive Vapers Compared to COVID 19 Positive Non-vapers
No full textSupplemental material, sj-docx-1-jpc-10.1177_21501319211062672 for Symptoms COVID 19 Positive Vapers Compared to COVID 19 Positive Non-vapers by David D. McFadden, Shari L. Bornstein, Robert Vassallo, Bradley R. Salonen, Mohammed Nadir Bhuiyan, Darrell R. Schroeder and Ivana T. Croghan in Journal of Primary Care & Community Health</p
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