46 research outputs found
The k* - nearest neighbors algorithm and an alternative approach for using the weights
No full textby Athanasios PaschosLiteraturverzeichnis: Blatt 116-121Dissertation Salzburg University 202
Contribution of asymmetric strange–antistrange sea to the Paschos–Wolfenstein relation
No full textAbstractThe NuTeV Collaboration reported a value of sin2θw measured in neutrino–nucleon deep inelastic scattering, and found that the value is three standard deviations from the standard model prediction. This result is obtained under the assumption that the strange quark–antiquark sea of nucleons are symmetric, and that the up and down quark distributions are symmetric with the simultaneous interchange of u↔d and p↔n. We discuss the contribution of asymmetric strange–antistrange sea to the Paschos–Wolfenstein relation in the extraction of weak mixing angle sin2θw. We also point out that the contribution of asymmetric strange–antistrange sea should remove roughly 30–80% of the discrepancy between the NuTeV result and other determinations of sin2θw when using the light-cone meson–baryon model to calculate the contribution of the strange–antistrange sea
Effect due to charge symmetry violation on the Paschos-Wolfenstein relation
No full textThe modification of the Paschos-Wolfenstein relation is investigated when the charge symmetry violations of valence and sea quark distributions in the nucleon are taken into account. We also study qualitatively the impact of charge symmetry violation (CSV) effect on the extraction of sin(2)theta(w) from deep-inelastic neutrino- and antineutrino-nuclei scattering within the light-cone meson-baryon fluctuation model. We find that the effect of CSV is too small to give a sizable contribution to the NuTeV result with various choices of mass difference inputs, which is consistence with the prediction that the strange-antistrange asymmetry can account for largely the NuTeV deviation in this model. It is noticeable that the effect of CSV might contribute to the NuTeV deviation when the larger difference between the internal momentum scales, alpha(p) of the proton and alpha(n) of the neutron, is considered.Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)5ARTICLE5null7
Biosynthese des Metallzentrums von [NiFe]-Hydrogenasen aus E. coli
No full textIn dieser Arbeit wurden drei Aspekte der Reifung der Hydrogenasen in E. coli näher untersucht:
1. Eine Deletion im carAB-Locus führt zum Verlust der Synthese aktiver Hydrogenasen in E. coli. Die Aktivität kann wiederhergestellt werden, wenn der Stamm mit einem carAB-tragenden Plasmid transformiert oder wenn er in Anwesenheit von Citrullin angezogen wird. Da der carAB-Locus für das Enzym der Carbamoylphosphat-Synthese kodiert und Citrullin in der Zelle in Carbamoylphosphats umgewandelt werden kann, ist Carbamoylphosphat die Ausgangssubstanz für die Synthese der Liganden des Metallzentrums. Aufgrund seiner Struktur wurden Reaktionsmechanismen postuliert, über die es in CN- und/oder CO-Einheiten umgewandelt werden kann.
2. Dem HypF-Protein konnte die biochemische Funktion einer Carbamoylphosphat-Phosphatase zugeschrieben werden, zusätzlich besitzt es eine an die Anwesenheit von Carbamoylphosphat gekoppelte ATP-hydrolysierenden Aktivität. Die ATP-Hydrolyse durch HypF führt zur Bildung von AMP und PPi und sie geht parallel mit der Ausbildung eines adenylierten Reaktionsintermediats wie über die Pyrophosphat-ATP-Austausch-Reaktion gezeigt wurde. Beim adenylierten Intermediat handelt es sich aller Wahrscheinlichkeit nach um Carbamoyl-Adenylat. Es wird postuliert, dass dieses Substrat vom HypE-Protein zur Bildung des CN-Liganden durch einen Wasserentzug über eine PurM-ähnliche Reaktion verwendet wird.
Durch spezifische Mutagenisierung konnten HypF-Varianten konstruiert werden, die zur Bildung aktiver Hydrogenasen unfähig waren. Die drei strukturell auffälligsten Motive des HypF-Proteins (Acylphosphat-Phosphatase-, Zink-Finger- und O-Carbamoyl-Transferase-Motiv) sind wichtig für die optimale Reifung der Hydrogenasen. Diese in vivo Unfähigkeit der Mutanten aktive Hydrogenasen zu synthetisieren geht mit dem Verlust der Carbamoylphosphat-Phosphatase einher.
3. Die kristallographische Analyse des HybD-Proteins als Beispiel einer spezifisch an der Hydrogenasen-Reifung beteiligten Protease, zeigte die Anwesenheit einer essentiellen Metallbindetasche, an deren Ausbildung Glu, Asp und His beteiligt sind und die in einer Peptidbindungsfurche liegt. Die Metalltasche fungiert spezifisch als Nickelerkennungsstelle in der Prozessierung, da nur Nickel-enthaltendes Apo-Protein prozessiert werden kan
H οξεία επίδραση ενός μαθήματος ελληνικού παραδοσιακού χορού στο άγχος κατάστασης
No full textΣκοπός της παρούσας εργασίας ήταν να μελετήσουμε την επίδραση της συμμετοχής σε ένα μάθημα ελληνικού παραδοσιακού χορού στο άγχος κατάστασης ενήλικων ατόμων. Το δείγμα της έρευνας αποτέλεσαν 278 ενήλικες (99 άνδρες και 179 γυναίκες), ηλικίας 18 ετών και πάνω κάτοικοι Αθηνών. Για την εκτίμηση του άγχους κατάστασης χρησιμοποιήθηκε το Ερωτηματολόγιο Άγχους Κατάστασης-Προδιάθεσης, το State Trait Anxiety Inventory (SΤAI) (Spielberger, Gorsuch, & Lushere, 1970; Spielberger, Gorsuch, Lushere, Vagg, & Jacobs, 1983) έτσι όπως έχει προσαρμοστεί για τον ελληνικό πληθυσμό από τους Κάκκο, Εκκεκάκη και Ζέρβα (1991). Το συγκεκριμένο ερωτηματολόγιο αποτελείται από 20 ερωτήσεις, οι οποίες συνοδεύονται από μία 4βάθμια κλίμακα απάντησης τύπου Likert, στις οποίες οι εξεταζόμενοι απαντούν σύμφωνα με το πως αισθάνονται "Τώρα, αυτή τη στιγμή" (π.χ. "Αισθάνομαι ήρεμος/η", "Αισθάνομαι ανήσυχος/η). Οι συμμετέχοντες απάντησαν στις ερωτήσεις του SΤAI δύο φορές (πέντε λεπτά πριν και πέντε λεπτά μετά από τη συμμετοχή τους στο μάθημα του ελληνικού παραδοσιακού χορού). Για τη στατιστική ανάλυση των δεδομένων πραγματοποιήθηκαν αναλύσεις διακύμανσης δύο παραγόντων με επαναληπτικές μετρήσεις στον δεύτερο παράγοντα και εξαρτημένες μεταβλητές τις βαθμολογίες που συγκέντρωσαν οι συμμετέχοντες στην κλίμακα άγχους για τον έλεγχο ενδεχόμενων διαφορών των συμμετεχόντων ως προς: (α) το φύλο, (β) την ηλικιακή τους κατηγορία, (γ) την οικογενειακή τους κατάσταση, (δ) την εργασιακή τους κατάσταση, (ε) το μορφωτικό τους επίπεδο, (στ) το τμήμα κατάταξης στον χορό και (ζ) το αντιληπτό επίπεδο χορευτικής ικανότητας, πριν και μετά τη συμμετοχή τους στο μάθημα ελληνικού παραδοσιακού χορού. Επίπεδο στατιστικής σημαντικότητας ορίστηκε σε α < .05. Σύμφωνα με τα ευρήματα, οι συμμετέχοντες οι συμμετέχοντες κατά μέσο όρο πριν το μάθημα είχαν περισσότερο άγχος (M = 1.76, SD = .56) από όσο είχαν μετά το μάθημα (M = 1.37 , SD = .38). Αυτή η διαφορά .38 BCa 95% CI [.32, .45] ήταν στατιστικώς σημαντική t(277) = 11.67, p = .000 και δήλωνε μια επίδραση μεσαίου μεγέθους d = 0.69. Ακόμα οι μέσες τιμές του επιπέδου άγχους πριν και μετά το μάθημα του χορού ανά εργασιακή κατάσταση έδειξε στατιστικώς σημαντική επίδραση της εργασιακής κατάστασης V=0.028 F(2, 275) =3.942, p = .021. Με απλά λόγια, οι εργαζόμενοι ξεκινούν από υψηλότερο άγχος πριν το μάθημα του χορού και έχουν χαμηλότερο μετά. Από τα παραπάνω συμπεραίνεται ότι το μάθημα του ελληνικού παραδοσιακού χορού επηρέασε θετικά το άγχος των συμμετεχόντων, και γι' αυτό τον λόγο προτείνεται για τους ενήλικες και ακόμα περισσότερο για τους εργαζόμενους.The aim of this study was to examine the effect of a single Greek traditional dance lesson in state anxiety. The survey sample consisted of 278 adults (99 males and 179 females), 18 years of age and above, residents of Athens. For the assessment of state anxiety, the State Trait Anxiety Inventory (STAI) (Spielberger, Gorsuch, & Lushere, 1970; Spielberger, Gorsuch, Lushere, Vagg, & Jacobs, 1983) was used as this has been adapted for the Greek population by Kakko, Ecekakis and Zervas (1991). This questionnaire consists of 20 questions that are accompanied by a 4-grade Likert-type response scale, in which the respondents answer according to how they feel "at the moment" (e.g. "I feel calm," "I feel anxious" etc.) The participants responded to STAI's questions twice (five minutes before and five minutes after the end of the Greek traditional dance lesson.) For the statistical analysis of the data, two-way ANOVA analysis was performed using as dependent variables the anxiety scale scores of the participants in order to check for potential differences among the participants with regard to: (a) their gender, (b) their age group, (c) their marital status, (d) their employment status; (e) their educational level; (f) the level of the class (i.e. elementary etc.); and (g) the perceived level of dance skills, before and after their participation in the Greek traditional dance lesson. The level of statistical significance was set to p ˂0.05. According to the results, on average participants before the lesson had more stress (M = 1.76, SD = .56) than they had after the lesson (M = 1.37, SD = .38). This difference .38 BCa 95% CI [.32, .45] was statistically significant t(277) = 11.67, p = .000 and denoted an effect of medium size d = 0.69. Moreover, the mean values of the anxiety level before and after dancing showed a statistically significant effect difference per employment status V = 0.028 F(2, 275) = 3.942, p = .021. Workers started with higher anxiety before dancing and had significantly lower anxiety afterwards. We may thus conclude that a single Greek traditional dance lesson can decrease significantly the stress of the participants, and is therefore beneficial for adults and especially for the employed ones
Biosynthese des Metallzentrums von [NiFe]-Hydrogenasen aus E. coli Analyse zweier Reifungsenzyme
No full textElastic FemtoCaching: Scale, Cache, and Route
No full textThe advent of elastic Content Delivery Networks (CDNs) enable Content Providers (CPs) to lease cache capacity on demand and at different cloud and edge locations in order to enhance the quality of their services. This article addresses key challenges in this context, namely how to invest an available budget in cache space in order to match spatio-temporal fluctuations of demand, wireless environment and storage prices. Specifically, we jointly consider dynamic cache rental, content placement, and request-cache association in wireless scenarios in order to provide just-in-time CDN services. The goal is to maximize the an aggregate utility metric for the CP that captures both service benefits due to caching and fairness in servicing different end users. We leverage the Lyapunov drift-minus-benefit technique and Jensen's inequality to transform our infinite horizon problem into hour-by-hour subproblems which can be solved without knowledge of future file popularity and transmission rates. For the case of non-overlapping small cells, we provide an optimal subproblem solution. However, in the general overlapping case, the subproblem becomes a mixed integer non-linear program (MINLP). In this case, we employ a randomized cache lease method to derive a scalable solution. We show that the proposed algorithm guarantees the theoretical performance bound by exploiting the submodularity property of the objective function and pick-and-compare property of the randomized cache lease method. Finally, via real dataset driven simulations, we find that the proposed algorithm achieves 154% utility compared to similar static cache storage-based algorithms in a representative urban topology.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Embedded System
Carbamoylphosphate requirement for synthesis of the active center of [NiFe]-hydrogenases
No full textAbstractThe iron of the binuclear active center of [NiFe]-hydrogenases carries two CN and one CO ligands which are thought to confer to the metal a low oxidation and/or spin state essential for activity. Based on the observation that one of the seven auxiliary proteins required for the synthesis and insertion of the [NiFe] cluster contains a sequence motif characteristic of O-carbamoyl-transferases it was discovered that carbamoyl phosphate is essential for formation of active [NiFe]-hydrogenases in vivo and is specifically required for metal center synthesis suggesting that it is the source of the CO and CN ligands. A chemical path for conversion of a carbamoyl group into cyano and carbonyl moieties is postulate
Moderately Exponential Approximation: Bridging the Gap Between Exact Computation and Polynomial Approximation
No full textThis paper proposes a way to bring together two seemingly “foreign” domains that are the polynomial approximation and the exact computation for NP-hard problems. We show how one can match ideas from both areas in order to design approximation algorithms achieving ratios unachievable in polynomial time (unless a very unlikely complexity conjecture is confirmed) with worst-case complexity much lower (though super-polynomial) than that of an exact computation
Optimistic No-regret Algorithms for Discrete Caching
No full textWe take a systematic look at the problem of storing whole files in a cache with limited capacity in the context of optimistic learning, where the caching policy has access to a prediction oracle. The successive file requests are assumed to be generated by an adversary, and no assumption is made on the accuracy of the oracle. We provide a universal lower bound for prediction-Assisted online caching and proceed to design a suite of policies with a range of performance-complexity trade-offs. All proposed policies offer sublinear regret bounds commensurate with the accuracy of the oracle. In this pursuit, we design, to the best of our knowledge, the first optimistic Follow-The-Perturbed leader policy, which generalizes beyond the caching problem. We also study the problem of caching files with different sizes and the bipartite network caching problem.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Networked System
