Home About us Contact
|
Home About us Contact | ||
|
|
||
Practical Questions (practical + question)
Selected AbstractsPractical questions in liver metastases of colorectal cancer: general principles of treatmentHPB, Issue 4 2007Héctor Daniel González Abstract Liver metastases of colorectal cancer are currently treated by multidisciplinary teams using strategies that combine chemotherapy, surgery and ablative techniques. Many patients classically considered non-resectable can now be rescued by neoadjuvant chemotherapy followed by liver resection, with similar results to those obtained in initial resections. While many of those patients will recur, repeat resection is a feasible and safe approach if the recurrence is confined to the liver. Several factors that until recently were considered contraindications are now recognized only as adverse prognostic factors and no longer as contraindications for surgery. The current evaluation process to select patients for surgery is no longer focused on what is to be removed but rather on what will remain. The single most important objective is to achieve a complete (R0) resection within the limits of safety in terms of quantity and quality of the remaining liver. An increasing number of patients with synchronous liver metastases are treated by simultaneous resection of the primary and the liver metastatic tumours. Multilobar disease can also be approached by staged procedures that combine neoadjuvant chemotherapy, limited resections in one lobe, embolization or ligation of the contralateral portal vein and a major resection in a second procedure. Extrahepatic disease is no longer a contraindication for surgery provided that an R0 resection can be achieved. A reverse surgical staged approach (liver metastases first, primary second) is another strategy that has appeared recently. Provided that a careful selection is made, elderly patients can also benefit from surgical treatment of liver metastases. [source] Analysis of parameter sensitivity and experimental design for a class of nonlinear partial differential equationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2005Michael L. Anderson Abstract The purpose of this work is to analyse the parameter sensitivity problem for a class of nonlinear elliptic partial differential equations, and to show how numerical simulations can help to optimize experiments for the estimation of parameters in such equations. As a representative example we consider the Laplace,Young problem describing the free surface between two fluids in contact with the walls of a bounded domain, with the parameters being those associated with surface tension and contact. We investigate the sensitivity of the solution and associated functionals to the parameters, examining in particular under what conditions the solution is sensitive to parameter choice. From this, the important practical question of how to optimally design experiments is discussed; i.e. how to choose the shape of the domain and the type of measurements to be performed, such that a subsequent inversion of the measured data for the model parameters yields maximal accuracy in the parameters. We investigate this through numerical studies of the behaviour of the eigenvalues of the sensitivity matrix and their relation to experimental design. These studies show that the accuracy with which parameters can be identified from given measurements can be improved significantly by numerical experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source] State space sampling of feasible motions for high-performance mobile robot navigation in complex environmentsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 6-7 2008Thomas M. Howard Sampling in the space of controls or actions is a well-established method for ensuring feasible local motion plans. However, as mobile robots advance in performance and competence in complex environments, this classical motion-planning technique ceases to be effective. When environmental constraints severely limit the space of acceptable motions or when global motion planning expresses strong preferences, a state space sampling strategy is more effective. Although this has been evident for some time, the practical question is how to achieve it while also satisfying the severe constraints of vehicle dynamic feasibility. The paper presents an effective algorithm for state space sampling utilizing a model-based trajectory generation approach. This method enables high-speed navigation in highly constrained and/or partially known environments such as trails, roadways, and dense off-road obstacle fields. © 2008 Wiley Periodicals, Inc. [source] Recency and duration neglect in subjective assessment of television picture qualityAPPLIED COGNITIVE PSYCHOLOGY, Issue 6 2001David S. Hands Digitally coded television pictures exhibit transient picture impairments that can vary in intensity and duration. It is an important practical question to determine the extent to which these transient impairments affect the overall quality of a television sequence, as a function of their location within the sequence, their duration and their magnitude. Five experiments are reported. It is shown that retrospective quality ratings are poorer when the worst-quality video occurs at the end compared to the beginning of a 30 s video sequence. This recency effect was eliminated when subjects were asked to continuously evaluate picture quality. The duration of an impairment was found to have little impact on quality ratings. A regression analysis found that quality ratings were best predicted by the peak impairment intensity. The results were interpreted in terms of Hogarth and Einhorn's (1992) belief-adjustment model. The implications for television picture quality evaluation are discussed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Contemporary management of pulmonary embolism: the answers to ten questionsJOURNAL OF INTERNAL MEDICINE, Issue 3 2010H. Bounameaux Abstract., Bounameaux H (Division of Angiology and Hemostasis, Department of Internal Medicine, University Hospitals of Geneva and Faculty of Medicine, Geneva, Switzerland). Contemporary management of pulmonary embolism: the answers to ten questions (Review). J Intern Med 2010; 268: 218,231. Pulmonary embolism (PE) cannot be diagnosed solely on a clinical basis, because of the lack of sensitivity and specificity of clinical signs and symptoms. Pulmonary angiography is invasive and resource demanding. Because the prevalence of PE is relatively low (20% or less) amongst individuals who are clinically suspected of having the disease, submitting all of them to imaging (multi-detector CT angiography or ventilation/perfusion lung scintigraphy) would not be cost-effective. Therefore, diagnostic algorithms have been developed that include clinical probability assessment and D-dimer measurement to select the patients who require noninvasive imaging. Once the diagnosis is suspected or confirmed, therapy must be started to avoid potentially fatal recurrence. Treatment starts for an initial 3-month period with a 5-day course of parenteral unfractionated or low-molecular-weight heparin or fondaparinux overlapping with and followed by oral vitamin K antagonists monitored to maintain an international normalized ratio of 2,3. This initial period of 3 months may then be followed by a long-term secondary prevention period in patients who experience an idiopathic thromboembolic event and are at low risk of bleeding. New oral anticoagulants that do require patient monitoring and might exhibit a more favourable benefit,risk balance are currently under extensive clinical testing and might change the situation in the near future. A critical appraisal of the contemporary management of suspected PE is given in this overview with the discussion of 10 practical questions. [source] Acupuncture for Chronic Pain: Is Acupuncture More than an Effective Placebo?PAIN PRACTICE, Issue 2 2010A Systematic Review of Pooled Data from Meta-analyses Abstract Objectives: There is controversy as to whether or not acupuncture is more effective than placebo. To help clarify this debate, we synthesized the evidence gathered from systematic reviews on the pooled data of high-quality randomized controlled trials comparing acupuncture to sham acupuncture for chronic pain. Method: Systematic reviews of acupuncture for the most commonly occurring forms of chronic pain (back, knee, and head) published between 2003 and 2008 were sourced from Ovid databases: Medline, Allied and Complementary Medicine database, Cochrane Library and Web of Science during December 2008. Eight systematic reviews with meta-analyses of pooled data were eligible for inclusion. Data were extracted for short- and longer-term outcomes for the most commonly occurring forms of pain. Two independent reviewers assessed methodological quality. Results: For short-term outcomes, acupuncture showed significant superiority over sham for back pain, knee pain, and headache. For longer-term outcomes (6 to12 months), acupuncture was significantly more effective for knee pain and tension-type headache but inconsistent for back pain (one positive and one inconclusive). In general, effect sizes (standardized mean differences) were found to be relatively small. Discussion: The accumulating evidence from recent reviews suggests that acupuncture is more than a placebo for commonly occurring chronic pain conditions. If this conclusion is correct, then we ask the question: is it now time to shift research priorities away from asking placebo-related questions and shift toward asking more practical questions about whether the overall benefit is clinically meaningful and cost-effective? [source] Secret Law and the Value of Publicity*RATIO JURIS, Issue 2 2009CHRISTOPHER KUTZ The dangers of secret law from the perspective of democratic accountability are clear, and need no elaboration. But distaste for secret law goes beyond questions of democracy. Since Plato, and continuing through such non-democratic thinkers as Bodin and Hobbes, secret law has been seen as a mark of tyranny, inconsistent with the notion of law itself. This raises both theoretical and practical questions. The theoretical questions involve the consistency of secret law with positivist legal theory. In principle, while a legal system as a whole could not be secret, publicity need not be part of the validity criteria for particular laws. The practical questions arise from the fact that secret laws, and secret governmental operations, are a common and often well-accepted aspect of governmental power. This paper argues that the flaw of secret law goes beyond accountability and beyond efficiency to the role that law plays, and can only play, in situating subjects' understanding of themselves in relation to the state. Secret law, as such, is inconsistent with this fundamental claim of the law to orient us in moral and political space, and undermines the claim to legitimacy of the state's rulers. [source] Science Driven Restoration: A Candle in a Demon Haunted World,Response to Cabin (2007)RESTORATION ECOLOGY, Issue 2 2007Christian P. Giardina Abstract Cabin (2007) asks whether formal science is an effective framework and methodology for designing and implementing ecological restoration programs. He argues that beyond certain ancillary benefits, restoration science has little of practical value to offer the practice of restoration. He goes on to suggest that restoration science most often represents an impediment to restoration practice because an "ivory tower" mentality limits the utility of experiments and diverts research dollars away from answering practical questions. His conclusion is that a nonscientific gardening approach may be more effective at restoring degraded ecosystems. We disagree with this perspective because: (1) restoration science has moved beyond exclusively using "square grids" placed on small patches of land to examine treatment effects on species representation; (2) Cabin's critique greatly undervalues the contribution of science to restoration practice even where the input of restoration scientists is not directly evident; and (3) the practice of restoration is unlikely to advance beyond small-scale and truly haphazard successes without well-designed studies that can provide peer-reviewed and widely accessible published information on the mechanisms underlying both successes and failures. We conclude that through integration with other disciplines, restoration science increasingly will provide novel approaches and tools needed to restore ecosystem composition, structure, and function at stand to landscape scales. As with the broader role of science in the human enterprise (Sagan 1996), the contribution of restoration science to restoration practice can only grow as the discipline matures. [source] Effect of exercise training on endothelium-derived nitric oxide function in humansTHE JOURNAL OF PHYSIOLOGY, Issue 1 2004Daniel J. Green Vascular endothelial function is essential for maintenance of health of the vessel wall and for vasomotor control in both conduit and resistance vessels. These functions are due to the production of numerous autacoids, of which nitric oxide (NO) has been the most widely studied. Exercise training has been shown, in many animal and human studies, to augment endothelial, NO-dependent vasodilatation in both large and small vessels. The extent of the improvement in humans depends upon the muscle mass subjected to training; with forearm exercise, changes are restricted to the forearm vessels while lower body training can induce generalized benefit. Increased NO bioactivity with exercise training has been readily and consistently demonstrated in subjects with cardiovascular disease and risk factors, in whom antecedent endothelial dysfunction exists. These conditions may all be associated with increased oxygen free radicals which impact on NO synthase activity and with which NO reacts; repeated exercise and shear stress stimulation of NO bioactivity redresses this radical imbalance, hence leading to greater potential for autacoid bioavailability. Recent human studies also indicate that exercise training may improve endothelial function by up-regulating eNOS protein expression and phosphorylation. While improvement in NO vasodilator function has been less frequently found in healthy subjects, a higher level of training may lead to improvement. Regarding time course, studies indicate that short-term training increases NO bioactivity, which acts to homeostatically regulate the shear stress associated with exercise. Whilst the increase in NO bioactivity dissipates within weeks of training cessation, studies also indicate that if exercise is maintained, the short-term functional adaptation is succeeded by NO-dependent structural changes, leading to arterial remodelling and structural normalization of shear. Given the strong prognostic links between vascular structure, function and cardiovascular events, the implications of these findings are obvious, yet many unanswered questions remain, not only concerning the mechanisms responsible for NO bioactivity, the nature of the cellular effect and relevance of other autacoids, but also such practical questions as the optimal intensity, modality and volume of exercise training required in different populations. [source] | ||||||||||||||||