197 research outputs found

    Calculating the energy spectra of magnetic molecules: application of real- and spin-space symmetries

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    The determination of the energy spectra of small spin systems as for instance given by magnetic molecules is a demanding numerical problem. In this work we review numerical approaches to diagonalize the Heisenberg Hamiltonian that employ symmetries; in particular we focus on the spin-rotational symmetry SU(2) in combination with point-group symmetries. With these methods one is able to block-diagonalize the Hamiltonian and thus to treat spin systems of unprecedented size. In addition it provides a spectroscopic labeling by irreducible representations that is helpful when interpreting transitions induced by Electron Paramagnetic Resonance (EPR), Nuclear Magnetic Resonance (NMR) or Inelastic Neutron Scattering (INS). It is our aim to provide the reader with detailed knowledge on how to set up such a diagonalization scheme.Comment: 29 pages, many figure

    Regulation of Apoptotic Effects by Erythrocarpine E, a Cytotoxic Limonoid from Chisocheton erythrocarpus in HSC-4 Human Oral Cancer Cells

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    The aim of this study was to determine the cytotoxic and apoptotic effects of erythrocarpine E (CEB4), a limonoid extracted from Chisocheton erythrocarpus on human oral squamous cell carcinoma. Based on preliminary dimethyl-2-thiazolyl-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays, CEB4 treated HSC-4 cells demonstrated a cytotoxic effect and inhibited cell proliferation in a time and dose dependent manner with an IC50 value of 4.0±1.9 µM within 24 h of treatment. CEB4 was also found to have minimal cytotoxic effects on the normal cell line, NHBE with cell viability levels maintained above 80% upon treatment. Annexin V-fluorescein isothiocyanate (FITC), poly-ADP ribose polymerase (PARP) cleavage and DNA fragmentation assay results showed that CEB4 induces apoptosis mediated cell death. Western blotting results demonstrated that the induction of apoptosis by CEB4 appeared to be mediated through regulation of the p53 signalling pathway as there was an increase in p53 phosphorylation levels. CEB4 was also found to up-regulate the pro-apoptotic protein, Bax, while down-regulating the anti-apoptotic protein, Bcl-2, suggesting the involvement of the intrinsic mitochondrial pathway. Reduced levels of initiator procaspase-9 and executioner caspase-3 zymogen were also observed following CEB4 exposure, hence indicating the involvement of cytochrome c mediated apoptosis. These results demonstrate the cytotoxic and apoptotic ability of erythrocarpine E, and suggest its potential development as a cancer chemopreventive agent

    Role of platelet-derived endothelial cell growth factor/thymidine phosphorylase in fluoropyrimidine sensitivity

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    Platelet-derived endothelial cell growth factor (PD-ECGF)/thymidine phosphorylase (TP) catalyses the reversible phosphorolysis of thymidine to thymine and 2-deoxyribose-1-phosphate and is involved in the metabolism of fluoropyrimidines. It can also activate 5'-deoxyfluorouridine (5'DFUR) and possibly 5-fluorouracil (5FU) and Ftorafur (Ft), but inactivates trifluorothymidine (TFT). We studied the contribution of TP activity to the sensitivity for these fluoropyrimidines by modulating its activity and/or expression level in colon and lung cancer cells using a specific inhibitor of TIP (TPI) or by overproduction of TIP via stable transfection of human TP. Expression was analysed using competitive template-RT-PCR (CT-RT-PCR), Western blot and an activity assay. TP activity ranged from nondetectable to 70678 pmol h(-1) 10(-6) cells, in Colo320 and a TP overexpressing clone Colo320TPI, respectively. We found a good correlation between TIP activity and mRNA expression (r = 0.964, P <0.01) in our cell panel. To determine the role of TIP in the sensitivity to 5FU, 5'DFUR, Ft and TFT, cells were cultured with the various fluoropyrimidines with or without TPI and differences in IC50's were established. TPI modified 5'DFUR, increasing the IC50's 2.5- to 1396-fold in WiDR and Colo320TPI, respectively. 5-Fluorouracil could be modified by inhibiting TP but to a lesser extent than 5'DFUR: IC50's increased 1.9- to 14.7-fold for WiDR and Colo320TPI, respectively. There was no effect on TFT or Ft. There appears to be a threshold level of TP activity to influence the 5'DFUR and 5FU sensitivity, which is higher for 5FU. Even high levels of TP overexpression only had a moderate effect on 5FU sensitivity. (C) 2003 Cancer Research UK

    Interaction between gemcitabine and topotecan in human non-small-cell lung cancer cells: effects on cell survival, cell cycle and pharmacogenetic profile

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    The pyrimidine analogue gemcitabine is an established effective agent in the treatment of non-small-cell lung cancer (NSCLC). The present study investigates whether gemcitabine would be synergistic with the topoisomerase I inhibitor topotecan against the NSCLC A549 and Calu-6 cells. Cells were treated with gemcitabine and topotecan for 1 h and the type of drug interaction was assessed using the combination index (CI). Cell cycle alterations were analysed by flow cytometry, while apoptosis was examined by the occurrence of DNA internucleosomal fragmentation, nuclear condensation and caspase-3 activation. Moreover, the possible involvement of the PI3K-Akt signalling pathway was investigated by the measurement of Akt phosphorylation. Finally, quantitative, real-time PCR (QRT-PCR) was used to study modulation of the gemcitabine-activating enzyme deoxycytidine kinase (dCK) and the cellular target enzyme ribonucleotide reductase (RR). In results, it was found that simultaneous and sequential topotecan → gemcitabine treatments were synergistic, while the reverse sequence was antagonistic in both cell lines. DNA fragmentation, nuclear condensation and enhanced caspase-3 activity demonstrated that the drug combination markedly increased apoptosis in comparison with either single agent, while cell cycle analysis showed that topotecan increased cells in S phase. Furthermore, topotecan treatment significantly decreased the amount of the activated form of Akt, and enhanced the expression of dCK (+155.0 and +115.3% in A549 and Calu-6 cells, respectively), potentially facilitating gemcitabine activity. In conclusion, these results indicate that the combination of gemcitabine and topotecan displays schedule-dependent activity in vitro against NSCLC cells. The gemcitabine → topotecan sequence is antagonistic while drug synergism is obtained with the simultaneous and the sequential topotecan → gemcitabine combinations, which are associated with induction of decreased Akt phosphorylation and increased dCK expression

    Ελαστοδυναμική ανάλυση πύργου ανεμογεννήτριας με προσεγγιστικές αναλυτικές μεθόδους

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    105 σ.Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Εφαρμοσμένη ΜηχανικήΣτην εργασία αυτή γίνεται χρήση αναλυτικής προσεγγιστικής μεθόδου για την επίλυση ενός σχετικά απλού δομικού συστήματος με κατανενημένη μάζα, ακαμψία και απόσβεση. Μετά την επίλυση ακολουθεί η ανάλυση και η μελέτη της συμπεριφοράς του. Κατ’ αρχήν παρουσιάζεται η μεθοδολογία της αναλυτικής προσεγγιστικής «Μεθόδου των Υποθετικών ιδιομορφών» σύμφωνα με την οποία η ζητούμενη απόκριση ενός μηχανικού ή δομικού συστήματος με κατανεμημένες ιδιότητες μάζας ακαμψίας και απόσβεσης έχει την μορφή σειράς, δηλαδή ενός γραμμικού συνδυασμού, επιλεγμένων συναρτήσεων (δοκιμαστικές συναρτήσεις) της χωρικής μεταβλητής πολλαπλασιασμένων με συντελεστές- συναρτήσεις του χρόνου οι οποίες στην συνέχεια πρόκειται να υπολογιστούν. Οι δοκιμαστικές συναρτήσεις της χωρικής μεταβλητής οφείλουν να ικανοποιούν όλες ή ένα μέρος των οριακών συνθηκών του προβλήματος. Οι συντελεστές- συναρτήσεις του χρόνου θεωρούνται ως «γενικευμένες συντεταγμένες» οι οποίες καθορίζουν την απόκριση του συστήματος. Υπολογίζονται οι εκφράσεις της Δυναμικής και Κινητικής ενέργειας του συστήματος και το δυνατό έργο των μη συντηρητικών δυνάμεων συναρτήσει της θεωρηθείσης σειράς των δοκιμαστικών συναρτήσεων. Τα μεγέθη αυτά οφείλουν να ικανοποιούν τις εξισώσεις Lagrange με άγνωστες συναρτήσεις του χρόνου τις προαναφερθείσες γενικευμένες συντεταγμένες. Έτσι προκύπτει ένα σύστημα συνήθων διαφορικών εξισώσεων η επίλυση του οποίου παρέχει τους άγνωστους συντελεστές-συναρτήσεις του χρόνου. Έτσι υπολογίζεται η θεωρηθείσα προσέγγιση της απόκρισης συναρτήσει του χρόνου. Το δομικό σύστημα που επιλύεται στην εργασία αυτή είναι ο πύργος ανεμογεννήτριας που προσομοιώνεται με στοιχείο δοκού σχήματος λεπτότοιχου κοίλου κυκλικού κόλουρου κώνου, ελαστικά πακτωμένου στη βάση του. Ο κινητήρας και τα πτερύγια της ανεμογεννήτριας προσομοιώνονται με μία συγκεντρωμένη μάζα και ροπή αδρανείας στο άνω άκρο του. Η φόρτιση του ανέμου ισοδυναμεί με μία οριζόντια δύναμη μεταβαλλόμενης έντασης ασκούμενη στο άνω άκρο του πύργου. Θεωρούνται τρείς διαφορετικές οικογένειες δοκιμαστικών συναρτήσεων για κάθε μία από τις οποίες εφαρμόζεται η Μέθοδος των υποθετικών ιδιομορφών. Διαπιστώνεται πολύ ικανοποιητική σύγκλιση των αποτελεσμάτων. Στη συνέχεια υιοθετώντας μία από αυτές τις οικογένειες δοκιμαστικών συναρτήσεων, διεξάγεται παραμετρική μελέτη για τις ιδιότητες, την απόκριση, την ένταση και την εν γένει συμπεριφορά του πύργου, από την οποία εξάγονται χρησιμοποιήσιμα συμπεράσματα.In this thesis, an approximate analytical method is used for solving a relatively simple system with distributed mass, stiffness and damping. After solving the following analysis and the study of behavior. First of all, the approximate analytical methodology "Assumed Modes Method" is analysed whereby the desired response of a mechanical or structural system with distributed mass, stiffness and damping have the form of a series, ie a linear combination of selected functions (trial functions) of the spatial variable-rate multiplied by functions of time which will then be calculated. The trial functions of spatial variable must satisfy all or part of the boundary conditions of the problem. The coefficients of time-functions are considered as "generalized coordinates" that define the response of the system. The structural system is solved in this work is the simulated wind turbine tower. The engine and the blades of the turbine are simulated with a concentrated mass androtational inertia at the upper end. The wind load is equivalent to a horizontal force varying intensity exerted at the top of the tower. We consider three different ‘families’ of trial functions for each one of them the ‘Assumed Modes Method’ is applied. There is very good convergence of results. Then taking one of these ‘families’ of the trial functions, parametric study is conducted in terms of the properties, response, intensity and overall behavior of the tower, from which usable conclusions are exported.Κωνσταντίνος Κ. Τόλη

    Melorheostosis of the hand

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    A trajectory data warehouse solution for workforce management decision-making

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    In modern workforce management, the demand for new ways to maximize worker satisfaction, productivity, and security levels is endless. Workforce movement data such as those source data from an access control system can support this ongoing process with subsequent analysis. In this study, a solution for attaining this goal is proposed, based on the design and implementation of a data mart as part of a dimensional trajectory data warehouse (TDW) that acts as a repository for the management of movement data. A novel methodological approach is proposed for modeling multiple spatial and temporal dimensions in a logical model. The case study presented in this paper for modeling and analyzing workforce movement data is to support human resource management decision-making and the following discussion provides a representative example of the contribution of a TDW in the process of information management and decision support systems. The entire process of exporting, cleaning, consolidating, and transforming data is implemented to achieve an appropriate format for final import. Structured query language (SQL) queries demonstrate the convenience of dimensional design for data analysis, and valuable information can be extracted from the movements of employees on company premises to manage the workforce efficiently and effectively. Visual analytics through data visualization support the analysis and facilitate decision-making and business intelligence
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