The complexity of two graph orientation problems

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 ElsevierWe consider two orientation problems in a graph, namely the minimization of the sum of all the shortest path lengths and the minimization of the diameter. Our main result is that for each positive integer k, there is a linear-time algorithm that decides for a planar graph Gwhether there is an orientation for which the diameter is at most k. We also extend this result from planar graphs to any minor-closed family F not containing all apex graphs. In contrast, it is known to be NP-complete to decide whether a graph has an orientation such that the sum of all the shortest path lengths is at most an integer specified in the input. We give a simpler proof of this result.This work is partially supported by EC Marie Curie programme NET-ACE (MEST-CT-2004-6724), and Heilbronn Institute for Mathematical Research, Bristol

Minimizing the oriented diameter of a planar graph

We consider the problem of minimizing the diameter of an orientation of a planar graph. A result of Chvátal and Thomassen shows that for general graphs, it is NP-complete to decide whether a graph can be oriented so that its diameter is at most two. In contrast to this, for each constant l, we describe an algorithm that decides if a planar graph G has an orientation with diameter at most l and runs in time O(c|V|), where c depends on l

The clustering coefficient of a scale-free random graph

We consider a random graph process in which, at each time step, a new vertex is added with m out-neighbours, chosen with probabilities proportional to their degree plus a strictly positive constant. We show that the expectation of the clustering coefficient of the graph process is asymptotically proportional to (log n)/n. Bollobas and Riordan have previously shown that when the constant is zero, the same expectation is asymptotically proportional to ((log n)^2)/n

Some applications of graph theory

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.For the abstract of this thesis, please see the attached PDF.This work was funded by a Marie Curie Early Stage Training Fellowship (NET-ACE-programme) under grant number MEST-CT-2004-6724

Synergistische Effekte von Celecoxib und Zoledronsäre beim humanen Ovarialkarzinom in vitro

In der vorliegenden Arbeit wurde die synergistischen Effekte von Celecoxib und Zoledronsäure auf die humanen Ovarialkarzinomzelllinien BG1 und SKOV-3 mittels Proliferationassays, Flowcytometry und Western blot untersucht

Sexual function after suburethral sling removal for dyspareunia

Introduction: Impact on sexual function has received little attention in the medical literature for a long time. Because of the site of insertion of permanent tension free vaginal tape (TVT) the G spot might be affected or the tape might interfere with arousal and sensory stimulation. Recent studies have reported varying degrees of sexual impairment after TVT insertion ranging from 0% to 15% including dyspareunia. Aim: The aim of this study was to evaluate sexual function before and after suburethral sling removal due to postoperative female de novo dyspareunia. As a secondary outcome, general patients' satisfaction with their overall continence situation was assessed. Patients and methods: Between December 2005 and December 2007, we included 18 female patients who complained of de novo dyspareunia after suburethral sling insertion for urinary stress incontinence. All patients filled in an FSFI questionnaire prior to sling removal and at 3 months postoperatively. Additionally, all women were asked to estimate their general satisfaction regarding their continence situation using a Visual Analogue Scale (VAS) from 0 to 10, with 0 being the least satisfying situation and 10 being the most satisfying situation. All patients underwent gynaecological examination including ICS-pelvic organ prolapse staging (ICS-POP score). Results: Of the 18 slings, ten were transobturator tapes (6 × TVT-O, 2 × Monarch, 2 × unknown) and eight were retropubic tapes (7 × TVT, 1 × SPARC). Desire, arousal, lubrication, satisfaction, and pain improved statistically significant. Orgasm scores were low with median scoring of 1.5 scores before and 1.0 scores after sling removal, and they did not change significantly after sling removal. The satisfaction rate deteriorated from a median of 7 (95% confidence interval [CI] 6.3-7.7) to a median of 4 (95% CI 3.7-5.1; p=0.99) but not statistically significant. Conclusions: Sexual function in patients with de novo dyspareuina is likely to improve after sling removal but not in all domains. Bladder function may deteriorat

The economic impact of wolves on the moose harvest in Sweden

In Sweden hunters and wolves both have an interest in hunting moose. This thesis is therefore a contribution to the current carnivore-game conflict resulting from this interest. The use of a production function approach is applied in order to value the impact of wolves on hunting values. An open access model is developed which derives a regression equation setting hunters’ harvest of moose per km2 as the dependent variable. Data on wolves, the moose harvest, hunting licenses and different Swedish game series is included in the analysis. Estimating empirically for the study period from 2002 to 2011, we identify the marginal product of wolves, the marginal cost in terms of loss in hunting revenues. We also compare the level of hunting effort with and without wolves in the system. This is done in the short term and for a steady-state equilibrium in the long term. The latter assumes a constant moose population and thus an effort adjustment by hunters. Our findings suggest a significant negative impact of the wolf on the moose harvest. When looking at both national data and different county groupings, there appear to be differences in marginal impacts as well as costs. Wolves in the counties with high wolf densities have lower marginal impacts than in counties with fewer wolves. This is reasonable, as wolf packs kill similar amounts of moose per year irrespective of their size. The marginal productivity of hunting effort did not vary much within and between groupings, whether there were wolves present or not. Under the current debate, this study adds in terms of shedding light on the change in hunters’ harvest revenues by wolves. However, the results do not consider social costs and thus conclusions for the wolf policy in Sweden have to be made with caution. Actions already attempt to address the conflict, yet it remains to be seen whether they are effective

Application of the Micro Pixel Photon Counter to calorimetry and PET

Technological solutions are being investigated, in both fields of calorimetry and positron emission tomography, to increase the granularity of the detectors and achieve a better imaging resolution. The Geiger-mode avalanche photodiode looks a promising photo-detector for these compact designs. Up to now, the main limit of its application was the detection of the scintillation light, mostly ranging in the blue region: the traditional Geiger-mode avalanche photodiode is green sensitive. Hamamatsu has recently released a photo-detector of the same family, the Micro Pixel Photon Counter (MPPC), with a high photo-detection efficiency in the 420nm spectral region, opening a new scenario for the scintillator-based systems. The direct readout performances of a MPPC directly coupled to a plastic organic scintillator and to an inorganic scintillator (LSO) are systematically studied. Possible applications in highly granular calorimeters and positron emission tomography detectors are discussed

Präklinische Evaluation des EGF-Rezeptor-Tyrosinkinase-Inhibitors "Gefitinib" an der A 253-Zelllinie bei Kopf- und Halstumoren

Die systemische Chemotherapie hat in der Behandlung der Kopf- und Halstumoren eine zunehmende Bedeutung und wird neben oder in Kombination mit der chirurgischen Therapie und/oder der Radiatio klinisch eingesetzt. Die Signaltransduktion der Familie der humanen epidermalen Wachstumsfaktoren ErbB1 (EGFR), ErbB2, ErbB3 und ErbB4 konnte als neuer Ansatz der antitumoralen Therapie bei Kopf- und Halstumoren definiert werden. EGFR ist ein transmembranes Glykoprotein mit einer extrazellulären Bindungsstelle und einer intrazellulären Tyrosinkinasefunktion und ist in ca. 90% der Tumoren des Kopf- und Halsbereiches expremiert. Die EGFR-Expression ist mit einer erhöhten Proliferationsrate, gesteigerter Angiogenese, Invasivität und verminderter Apoptose der Tumorzelle korreliert und geht mit einer schlechteren Prognose der Erkrankungen einher. Eine Blockade der EGFR-assoziierten Signaltransduktion kann an der ATP-Bindungsstelle der EGFR-Tyrosinkinase mit Gefitinib erfolgen. Gefitinib wird in der Therapie der nichtkleinzelligen Bronchialkarzinome klinisch eingesetzt und ist im Bereich der Kopf- und Halstumoren im klinisch experimentellen Stadium. In experimentellen Untersuchungen wurde der Einfluss von Gefitinib in subtoxischen Konzentrationen in Kombination mit den zytotoxischen Substanzen Cisplatin, Carboplatin, 5-Fluorouracil, Irinotecan und Paclitaxel an der Kopf- und Halstumorzelllinie A253 untersucht. Mittels Westernblot- und RT-PCR-Analysen wurde der Einfluss von Gefitinib mit und ohne Stimulation mit einem Liganden „epithelial growth factor„ (EGF) auf die Expression des EGFR unter Nährstoffmangelbedingungen untersucht. Gefitinib zeigte als Monosubstanz zytotoxische Wirkung auf die Zelllinie A253. Die Kombination von Gefitinib in subtoxischer Konzentration mit den o. a. zytotoxischen Substanzen zeigte keinen zytotoxischen Synergismus. In den RT-PCR-Analysen konnte kein Effekt von Gefitinib oder der Stimulation mit EGF auf Zellen unter Nährstoffmangelbedingungen nachgewiesen werden. Im Westernblot zeigte sich unter optimalen und unter Nährstoffmangelbedingungen ein qualitativer „Shift“ in der EGFR-Proteinbande, der mit Gefitinib zu inhibieren war. In der quantitativen Proteinexpression konnte kein Unterschied festgestellt werden. Diese präklinischen in vitro Daten stehen im Einklang mit den klinischen Daten einer Kombinationstherapie von Gefitinib mit platinbasierter Chemotherapie an Patienten mit nichtkleinzelligen Bronchialkarzinomen und legen Nahe, dass der Einsatz von Gefitinib nicht zu einer erhöhten antitumorale Wirkung dieser Zytostatika führt