Pencils on real curves

We consider coverings of real algebraic curves to real rational algebraic curves. We show the existence of such coverings having prescribed topological degree on the real locus. From those existence results we prove some results on Brill-Noether Theory for pencils on real curves. For coverings having topological degree 0 we introduce the covering number k and we prove the existence of coverings of degree 4 with prescribed covering number.Comment: 27 pages, 12 figure

Ultrasound and light: friend or foe? On the role of intravascular ultrasound in the era of optical coherence tomography

More than 20 years after its introduction, intravascular ultrasound (IVUS) has outlived many other intracoronary techniques. IVUS was useful to solve many interventional problems and assisted us in understanding the dynamics of atherosclerosis. It serves as an established imaging endpoint in large progression-regression trial and as an important workhorse in many catheterization laboratories. Nowadays, increasingly complex lesions are treated with drug-eluting stents. The application of IVUS during such interventions can be very useful. Recently, optical coherence tomography (OCT), a light-based imaging technique, has entered the clinical arena. The “omnipresence” of OCT during scientific sessions and live courses with PCI may raise in many the question: Does IVUS have a future in the “era of OCT”? Three review articles, highlighted by this editorial, demonstrate the broad spectrum of current IVUS applications and underline the significant role of IVUS during the last two decades. OCT, the much younger technique, still has to prove its value. Yet OCT is likely to take over some of the current indications of IVUS as a research tool. In addition, OCT is currently gaining clinical significance for stent optimization during complex interventional procedures. Nevertheless, there is little doubt that IVUS still has a major role in studies on coronary atherosclerosis and for guidance of coronary stenting. Thus, ultrasound and light—are they friend or foe? In fact, both methods are good in their own rights. They are complementary rather than competitive. Moreover, in combination, at least for certain indications, they could be even better

Musical complexity and ‘Embodied notation’ : a study of the opus Clavicembalisticum (K. S. Sorabji)

Scores of complex, 20th century, solo piano pieces can be difficult to perform and may even include elements that are physically impossible to play. This article investigates the role of music notation in the Opus Clavicembalisticum of Sorabji, which is a rather extreme case in terms of virtuosity and length. To analyze the effect of score notation on learning and performing, 9 pianists were asked to practice music fragments in 3 different score editions, being the original Urtext edition (a 4-staff score), Performance edition (same notes but organized according to an “embodied” performance viewpoint), and Study edition (further simplified and with added analytical reading aids). The hypothesis was that the “embodied notation”, would have an effect on study time (shorter study time) and errors (less errors). Objective features of the study process and performance, such as study time, error ratio, markings on the score (fingerings, hand distribution, synchronization) were compared. Subjective remarks the performers made about the scores were also analyzed. Findings indicate a significant positive influence of the score type on the study time. These results suggest that players draw on ideomotor principles, which include processes based on learned and “embodied” associations between perceived images of the scores and the motor activity that is directly associated with it

Issues in higher education policy : an update on higher education policy issues in 2004 in 11 Western countries

Higher education is a dynamic field. It is, however, also a field where changes don¿t take place overnight. This 2004 update report covers a period of 1.5 years, a period in which some earlier policy initiatives have been implemented and new ones have emerged. It is therefore not surprising to observe that many of the policy issues on the agenda in the previous Update Report (April, 2003) still are a topic of debate today.\ud The main part of the report are the descriptions of the current (2004) higher education debates and policy initiatives for each of the eleven IHEM countries, arranged in four themes educational and research infrastructure, finance, governance and quality. In conclusion, four `overarching¿ policy issues in contemporary European (and Australian) higher education are discussed. These issues are:\ud * The Bologna process and changing degree structures\ud * The changing organisation of research\ud * Financial accountability and responsibility\ud * Interactive governanc

Combining Column Generation and Lagrangian Relaxation

Although the possibility to combine column generation and Lagrangian relaxation has been known for quite some time, it has only recently been exploited in algorithms. In this paper, we discuss ways of combining these techniques. We focus on solving the LP relaxation of the Dantzig-Wolfe master problem. In a first approach we apply Lagrangian relaxation directly to this extended formulation, i.e. no simplex method is used. In a second one, we use Lagrangian relaxation to generate new columns, that is Lagrangian relaxation is applied to the compact for-mulation. We will illustrate the ideas behind these algorithms with an application in Lot-sizing. To show the wide applicability of these techniques, we also discuss applications in integrated vehicle and crew scheduling, plant location and cutting stock problems

Serial intravascular ultrasound assessment of changes in coronary atherosclerotic plaque dimensions and composition: an update

This manuscript reviews the use of serial intravascular ultrasound (IVUS) examination of coronary atherosclerosis in recent observational studies and randomized trials that revealed the effects of cholesterol-lowering and lipid-modifying therapies and offered novel insight into plaque progression and regression. We discuss the value of plaque progression–regression as complementary imaging endpoint and potential surrogate marker of cardiovascular event risk. In addition, the progress in serial assessment of coronary plaque composition and plaque vulnerability by radiofrequency-based analyses is reviewed. Finally, we report on the evaluation of true vessel remodelling in recent serial IVUS trials and discuss the future perspective of serial invasive imaging of coronary atherosclerosis

Feasibility of PET/CT system performance harmonisation for quantitative multicentre Zr-89 studies

PurposeThe aim of this study was to investigate the variability in quantitative performance and feasibility of quantitative harmonisation in Zr-89 PET/CT imaging.MethodsEight EANM EARL-accredited (Kaalep A et al., Eur J Nucl Med Mol Imaging 45:412-22, 2018) PET/CT systems were investigated using phantom acquisitions of uniform and NEMA NU2-2007 body phantoms. The phantoms were filled according to EANM EARL guidelines for [F-18]FDG, but [F-18]FDG solution was replaced by a Zr-89 calibration mixture. For each system, standard uptake value (SUV) accuracy and recovery coefficients (RC) using SUVmean, SUVmax and SUVpeak metrics were determined.ResultsAll eight investigated systems demonstrated similarly shaped RC curves, and five of them exhibited closely aligning recoveries when SUV bias correction was applied. From the evaluated metrics, SUVpeak was found to be least sensitive to noise and reconstruction differences among different systems.ConclusionsHarmonisation of PET/CT scanners for quantitative Zr-89 studies is feasible when proper scanner-dose calibrator cross-calibration and harmonised image reconstruction procedures are followed. An accreditation programme for PET/CT scanners would facilitate multicentre Zr-89 quantitative studies

Impact of New Scatter Correction Strategies on High-Resolution Research Tomograph Brain PET Studies

The aim of this study is to evaluate the impact of different scatter correction strategies on quantification of high-resolution research tomograph (HRRT) data for three tracers covering a wide range in kinetic profiles. Healthy subjects received dynamic HRRT scans using either (R)-[C-11]verapamil (n = 5), [C-11]raclopride (n = 5) or [C-11]flumazenil (n = 5). To reduce the effects of patient motion on scatter scaling factors, a margin in the attenuation correction factor (ACF) sinogram was applied prior to 2D or 3D single scatter simulation (SSS). Some (R)-[C-11]verapamil studies showed prominent artefacts that disappeared with an ACF-margin of 10 mm or more. Use of 3D SSS for (R)-[C-11]verapamil showed a statistically significant increase in volume of distribution compared with 2D SSS (p 0.05). When there is a patient motion-induced mismatch between transmission and emission scans, applying an ACF-margin resulted in more reliable scatter scaling factors but did not change (and/or deteriorate) quantification

Increased cerebral (R)-[11C]PK11195 uptake and glutamate release in a rat model of traumatic brain injury: a longitudinal pilot study

<p>Abstract</p> <p>Background</p> <p>The aim of the present study was to investigate microglia activation over time following traumatic brain injury (TBI) and to relate these findings to glutamate release.</p> <p>Procedures</p> <p>Sequential dynamic <it>(R)</it>-[¹¹C]PK11195 PET scans were performed in rats 24 hours before (baseline), and one and ten days after TBI using controlled cortical impact, or a sham procedure. Extracellular fluid (ECF) glutamate concentrations were measured using cerebral microdialysis. Brains were processed for histopathology and (immuno)-histochemistry.</p> <p>Results</p> <p>Ten days after TBI, <it>(R)</it>-[¹¹C]PK11195 binding was significantly increased in TBI rats compared with both baseline values and sham controls (p < 0.05). ECF glutamate values were increased immediately after TBI (27.6 ± 14.0 μmol·L^-1) as compared with the sham procedure (6.4 ± 3.6 μmol·L^-1). Significant differences were found between TBI and sham for ED-1, OX-6, GFAP, Perl's, and Fluoro-Jade B.</p> <p>Conclusions</p> <p>Increased cerebral uptake of <it>(R)</it>-[¹¹C]PK11195 ten days after TBI points to prolonged and ongoing activation of microglia. This activation followed a significant acute posttraumatic increase in ECF glutamate levels.</p