206 research outputs found
On the Numerical Integration of Singular Initial and Boundary Value Problems for Generalised Lane-Emden and Thomas-Fermi Equations
We propose a geometric approach for the numerical integration of singular
initial value problems for (systems of) quasi-linear differential equations. It
transforms the original problem into the problem of computing the unstable
manifold at a stationary point of an associated vector field and thus into one
which can be solved in an efficient and robust manner. Using the shooting
method, our approach also works well for boundary value problems. As examples,
we treat some (generalised) Lane-Emden equations and the Thomas-Fermi equation.Comment: 29 pages, 9 figure
Robust interactive cutting based on an adaptive octree simulation mesh
We present an adaptive octree based approach for interactive cutting of deformable objects. Our technique relies on efficient refine- and node split-operations. These are sufficient to robustly represent cuts in the mechanical simulation mesh. A high-resolution surface embedded into the octree is employed to represent a cut visually. Model modification is performed in the rest state of the object, which is accomplished by back-transformation of the blade geometry. This results in an improved robustness of our approach. Further, an efficient update of the correspondences between simulation elements and surface vertices is proposed. The robustness and efficiency of our approach is underlined in test examples as well as by integrating it into a prototype surgical simulato
Ionic liquids as new absorbents for absorption chillers and heat pumps
Part of:
Thermally driven heat pumps for heating and cooling. –
Ed.: Annett Kühn –
Berlin: Universitätsverlag der TU Berlin, 2013
ISBN 978-3-7983-2686-6 (print)
ISBN 978-3-7983-2596-8 (online)
urn:nbn:de:kobv:83-opus4-39458
[http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-39458]In this paper, ionic liquids are proposed as new absorbents for absorption chillers and heat pumps. The theoretical and experimental based research of Technische Universität Berlin, Bavarian Center for Applied Energy Research (ZAE Bayern) and Graz University of Technology is presented and test and simulation results are discussed. The results show the suitability and promising potential of ionic liquids as absorbents but the research organizations agree in the need of further effort in R&D
Countering commoditization through innovation: challenges for European B2B companies
Overview: B2B companies are an important part of the global economy, and traditionally they have relied on technological capabilities to compete. Currently, the B2B sector is under increasing pressure, as many B2B companies no longer have a technological advantage, and they also face commoditization. Companies see innovation as a way to compete against these challenges. Although product and process innovation are important in B2B markets, companies need other forms of innovation such as service and business model innovation to create a differentiated offering. B2B managers’ views on the value of market research vary widely, and many are unaware that sophisticated techniques such as ethnography can effectively identify B2B customer needs. Our Commoditization-Innovativeness Matrix is a diagnosis tool that enables B2B companies to identify actions that can counter commoditization
Tree-ring stable isotopes and radiocarbon reveal pre- and post-eruption effects of volcanic processes on trees on Mt. Etna (Sicily, Italy)
Early detection of volcanic eruptions is of major importance for protecting
human life. Ground deformation and changes in seismicity, geochemistry,
petrology, and gravimetry are used to assess volcanic activity before
eruptions. Studies on Mt. Etna (Italy) have demonstrated that vegetation can be
affected by pre-eruptive activity before the onset of eruptions. During two
consecutive years before Mt. Etna's 2002/2003 flank eruption, enhanced
vegetation index (NDVI) values were detected along a distinct line which later
developed into an eruptive fissure. However, the mechanisms by which volcanic
activity can lead to changes in pre-eruption tree growth processes are still
not well understood. We analysed C, O and
C in the rings of the survived trees growing near to the line where the
pre-eruptive increase in NDVI was observed in order to evaluate whether the
uptake of water vapour or fossil volcanic CO2 could have contributed to the
enhanced NDVI. We found a dramatic decrease in O in tree rings
formed before 2002/2003 in trees close to the eruption fissure, suggesting
uptake of volcanic water by trees during pre-eruptive magma degassing. Moist
conditions caused by outgassing of ascending magma may also have led to an
observed reduction in tree-ring C following the eruption.
Furthermore, only ambiguous evidence for tree uptake of degassed CO2 was found.
Our results suggest that additional soil water condensed from degassed water
vapour may have promoted photosynthesis, explaining local increases in NDVI
before the 2002/2003 Mt. Etna flank eruption. Tree-ring oxygen stable isotopes
might be used as indicators of past volcanic eruptions
Quality-of-life and toxicity in cancer patients treated with multiple courses of radiation therapy
Background
Treatment of metastatic cancer patients with multiple repeat courses of radiotherapy has become more frequent due to their improved overall survival. However, very little is known about their long-term outcome. This analysis reports on the quality-of-life, hematologic toxicity, patient-reported experiences and satisfaction, and psychological distress of cancer patients treated with multiple repeat radiotherapy.
Methods
All patients treated with ≥5 courses of radiotherapy between 2011 and 2019 at the Department of Radiation Oncology, University Hospital Zurich (USZ) were screened for this study. A course of radiotherapy was defined as all treatment sessions to one anatomical site under one medical indication. All patients completed two questionnaires: EORTC QLQ-C30 questionnaire for quality-of-life and a questionnaire evaluating psychological distress and patient-reported experiences. Hematologic toxicities were assessed via a recent blood sample.
Results
Of n = 33 patients treated with ≥5 radiotherapy courses and being alive, 20 (60.6%) participated in this study. The most common primary tumor was non-small cell lung cancer (n = 14, 42.4%). The most common sites of irradiation were brain (n = 78, 37.1%) and bone metastases (n = 59, 28.1%). All participating patients reported that they had experienced a subjective benefit from multiple repeat radiotherapy and denied increased side effects in later radiotherapy courses. Yet, 45% (n = 9) of the patients reported an increase of psychological distress with increasing numbers of radiotherapy treatments. While global health status was stable, patients having received multiple repeat radiotherapy reported increased fatigue (p = <0.006). Blood analysis showed significantly reduced hemoglobin and lymphocyte levels compared to the healthy population (p = <0.03).
Discussion and conclusion
Patient-reported experiences and satisfaction of long-term cancer patients treated with multiple repeat radiotherapy are positive. However, increased levels of fatigue and significantly reduced hemoglobin and lymphocyte levels were observed. These data indicate the need to further investigate the effects of multiple courses of radiotherapy in chronic cancer patients
Validation and extension of the METSSS score in a metastatic cancer patient cohort after palliative radiotherapy within the last phase of life
Introduction and background
Choosing the right treatment for the right patient in a setting of metastatic cancer disease remains a challenge. To facilitate clinical decision-making, predictive tools have been developed to personalize treatment. Here, we aim to assess the use of the recently proposed "METSSS score" as a prognostic tool for overall survival of cancer patients after palliative radiotherapy in the last phase of life.
Methods
All patients treated with palliative radiotherapy at the end-of-life at the Department of Radiation Oncology of the University Hospital Zurich between January 2010 and December 2019 were included in this study. Data on demographics, diagnosis, treatment and comorbidities was extracted from the treatment planning and the electronical medical records system. To statistically assess the validity of the "METSSS score", the mortality risk score was calculated, followed by stratification of all patients to prognostic risk groups. The prediction of the 1-year overall survival estimates was subsequently calculated.
Results
Over the past decade, 274 patients have received palliative radiotherapy during the end-of-life period. One third of patients was female (34%, n = 93). The most frequent primary tumor was lung cancer (n = 121, 44%), and 55% of patients (n = 152) had no comorbidities according to the Charlson-Deyo comorbidity index. The most common radiotherapy site was the brain and eye region (42%, n = 115). The median actual overall survival of all patients was 40 days from the start of radiotherapy. The "METSSS score" survival model predicted that 269 patients (98.1%) belong into the high-risk, four patients (1.5%) into the medium-risk, and one patient (0.4%) into the low-risk group. The predicted median 1-year overall survival was 10%.
Discussion
The METSSS score correctly predicted the survival of our end-of-life patient cohort by assigning them into the highest risk category, and it can therefore serve as a decision-making tool when assigning patient to symptomatic radiotherapy
Prevalence of sleep-disordered breathing after stroke and TIA: A meta-analysis.
OBJECTIVE
To perform a systematic review and meta-analysis on the prevalence of sleep-disordered breathing (SDB) after stroke.
METHODS
We searched PubMed, Embase (Ovid), the Cochrane Library, and CINAHL (from their commencements to April 7, 2017) for clinical studies reporting prevalence and/or severity of SDB after stroke or TIA. Only sleep apnea tests performed with full polysomnography and diagnostic devices of the American Academy of Sleep Medicine categories I-IV were included. We conducted random-effects meta-analysis. PROSPERO registration number: CRD42017072339.
RESULTS
The initial search identified 5,211 publications. Eighty-nine studies (including 7,096 patients) met inclusion criteria. Fifty-four studies were performed in the acute phase after stroke (after less than 1 month), 23 studies in the subacute phase (after 1-3 months), and 12 studies in the chronic phase (after more than 3 months). Mean apnea-hypopnea index was 26.0/h (SD 21.7-31.2). Prevalence of SDB with apnea-hypopnea index greater than 5/h and greater than 30/h was found in 71% (95% confidence interval 66.6%-74.8%) and 30% (95% confidence interval 24.4%-35.5%) of patients, respectively. Severity and prevalence of SDB were similar in all examined phases after stroke, irrespective of the type of sleep apnea test performed. Heterogeneity between studies () was mostly high.
CONCLUSION
The high prevalence of SDB after stroke and TIA, which persists over time, is important in light of recent studies reporting the (1) feasibility and (2) efficacy of SDB treatment in this clinical setting
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