| 1. |
- Thomas, HS, et al.
(författare)
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- 2019
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swepub:Mat__t
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| 2. |
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| 3. |
- Elhai, M, et al.
(författare)
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Outcomes of patients with systemic sclerosis treated with rituximab in contemporary practice: a prospective cohort study
- 2019
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Ingår i: Annals of the rheumatic diseases. - : BMJ. - 1468-2060 .- 0003-4967. ; 78:7, s. 979-987
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Tidskriftsartikel (refereegranskat)abstract
- To assess the safety and efficacy of rituximab in systemic sclerosis (SSc) in clinical practice.MethodsWe performed a prospective study including patients with SSc from the European Scleroderma Trials and Research (EUSTAR) network treated with rituximab and matched with untreated patients with SSc. The main outcomes measures were adverse events, skin fibrosis improvement, lung fibrosis worsening and steroids use among propensity score-matched patients treated or not with rituximab.Results254 patients were treated with rituximab, in 58% for lung and in 32% for skin involvement. After a median follow-up of 2 years, about 70% of the patients had no side effect. Comparison of treated patients with 9575 propensity-score matched patients showed that patients treated with rituximab were more likely to have skin fibrosis improvement (22.7 vs 14.03 events per 100 person-years; OR: 2.79 [1.47–5.32]; p=0.002). Treated patients did not have significantly different rates of decrease in forced vital capacity (FVC)>10% (OR: 1.03 [0.55–1.94]; p=0.93) nor in carbon monoxide diffusing capacity (DLCO) decrease. Patients having received rituximab were more prone to stop or decrease steroids (OR: 2.34 [1.56–3.53], p<0.0001). Patients treated concomitantly with mycophenolate mofetil had a trend for better outcomes as compared with patients receiving rituximab alone (delta FVC: 5.22 [0.83–9.62]; p=0.019 as compared with controls vs 3 [0.66–5.35]; p=0.012).ConclusionRituximab use was associated with a good safety profile in this large SSc-cohort. Significant change was observed on skin fibrosis, but not on lung. However, the limitation is the observational design. The potential stabilisation of lung fibrosis by rituximab has to be addressed by a randomised trial.
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| 4. |
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| 5. |
- van Bragt, JJMH, et al.
(författare)
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Characteristics and treatment regimens across ERS SHARP severe asthma registries
- 2020
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Ingår i: The European respiratory journal. - : European Respiratory Society (ERS). - 1399-3003 .- 0903-1936. ; 55:1
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the characteristics and treatments of patients with severe asthma across Europe, but both are likely to vary. This is the first study in the European Respiratory Society Severe Heterogeneous Asthma Research collaboration, Patient-centred (SHARP) Clinical Research Collaboration and it is designed to explore these variations. Therefore, we aimed to compare characteristics of patients in European severe asthma registries and treatments before starting biologicals.This was a cross-sectional retrospective analysis of aggregated data from 11 national severe asthma registries that joined SHARP with established patient databases.Analysis of data from 3236 patients showed many differences in characteristics and lifestyle factors. Current smokers ranged from 0% (Poland and Sweden) to 9.5% (Belgium), mean body mass index ranged from 26.2 (Italy) to 30.6 kg·m−2 (the UK) and the largest difference in mean pre-bronchodilator forced expiratory volume in 1 s % predicted was 20.9% (the Netherlands versus Hungary). Before starting biologicals patients were treated differently between countries: mean inhaled corticosteroid dose ranged from 700 to 1335 µg·day−1 between those from Slovenia versus Poland when starting anti-interleukin (IL)-5 antibody and from 772 to 1344 µg·day−1 in those starting anti-IgE (Slovenia versus Spain). Maintenance oral corticosteroid use ranged from 21.0% (Belgium) to 63.0% (Sweden) and from 9.1% (Denmark) to 56.1% (the UK) in patients starting anti-IL-5 and anti-IgE, respectively.The severe asthmatic population in Europe is heterogeneous and differs in both clinical characteristics and treatment, often appearing not to comply with the current European Respiratory Society/American Thoracic Society guidelines definition of severe asthma. Treatment regimens before starting biologicals were different from inclusion criteria in clinical trials and varied between countries.
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| 6. |
- Becker, M, et al.
(författare)
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Predictors of disease worsening defined by progression of organ damage in diffuse systemic sclerosis: a European Scleroderma Trials and Research (EUSTAR) analysis
- 2019
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Ingår i: Annals of the rheumatic diseases. - : BMJ. - 1468-2060 .- 0003-4967. ; 78:9, s. 1242-1248
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Tidskriftsartikel (refereegranskat)abstract
- Mortality and worsening of organ function are desirable endpoints for clinical trials in systemic sclerosis (SSc). The aim of this study was to identify factors that allow enrichment of patients with these endpoints, in a population of patients from the European Scleroderma Trials and Research group database.MethodsInclusion criteria were diagnosis of diffuse SSc and follow-up over 12±3 months. Disease worsening/organ progression was fulfilled if any of the following events occurred: new renal crisis; decrease of lung or heart function; new echocardiography-suspected pulmonary hypertension or death. In total, 42 clinical parameters were chosen as predictors for the analysis by using (1) imputation of missing data on the basis of multivariate imputation and (2) least absolute shrinkage and selection operator regression.ResultsOf 1451 patients meeting the inclusion criteria, 706 had complete data on outcome parameters and were included in the analysis. Of the 42 outcome predictors, eight remained in the final regression model. There was substantial evidence for a strong association between disease progression and age, active digital ulcer (DU), lung fibrosis, muscle weakness and elevated C-reactive protein (CRP) level. Active DU, CRP elevation, lung fibrosis and muscle weakness were also associated with a significantly shorter time to disease progression. A bootstrap validation step with 10 000 repetitions successfully validated the model.ConclusionsThe use of the predictive factors presented here could enable cohort enrichment with patients at risk for overall disease worsening in SSc clinical trials.
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| 7. |
- Palmer, Nicholette D, et al.
(författare)
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A genome-wide association search for type 2 diabetes genes in African Americans.
- 2012
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Ingår i: PloS one. - San Francisco : Public Library of Science (PLoS). - 1932-6203. ; 7:1, s. e29202-
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Tidskriftsartikel (refereegranskat)abstract
- African Americans are disproportionately affected by type 2 diabetes (T2DM) yet few studies have examined T2DM using genome-wide association approaches in this ethnicity. The aim of this study was to identify genes associated with T2DM in the African American population. We performed a Genome Wide Association Study (GWAS) using the Affymetrix 6.0 array in 965 African-American cases with T2DM and end-stage renal disease (T2DM-ESRD) and 1029 population-based controls. The most significant SNPs (n = 550 independent loci) were genotyped in a replication cohort and 122 SNPs (n = 98 independent loci) were further tested through genotyping three additional validation cohorts followed by meta-analysis in all five cohorts totaling 3,132 cases and 3,317 controls. Twelve SNPs had evidence of association in the GWAS (P<0.0071), were directionally consistent in the Replication cohort and were associated with T2DM in subjects without nephropathy (P<0.05). Meta-analysis in all cases and controls revealed a single SNP reaching genome-wide significance (P<2.5×10(-8)). SNP rs7560163 (P = 7.0×10(-9), OR (95% CI) = 0.75 (0.67-0.84)) is located intergenically between RND3 and RBM43. Four additional loci (rs7542900, rs4659485, rs2722769 and rs7107217) were associated with T2DM (P<0.05) and reached more nominal levels of significance (P<2.5×10(-5)) in the overall analysis and may represent novel loci that contribute to T2DM. We have identified novel T2DM-susceptibility variants in the African-American population. Notably, T2DM risk was associated with the major allele and implies an interesting genetic architecture in this population. These results suggest that multiple loci underlie T2DM susceptibility in the African-American population and that these loci are distinct from those identified in other ethnic populations.
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| 8. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 9. |
- Ortiz-Fernandez, Lourdes, et al.
(författare)
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Identification of susceptibility loci for Takayasu arteritis through a large multi-ancestral genome-wide association study
- 2021
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Ingår i: American Journal of Human Genetics. - CAMBRIDGE, MA USA : Cell Press. - 0002-9297 .- 1537-6605. ; 108:1, s. 84-99
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Tidskriftsartikel (refereegranskat)abstract
- Takayasu arteritis is a rare inflammatory disease of large arteries. We performed a genetic study in Takayasu arteritis comprising 6,670 individuals (1,226 affected individuals) from five different populations. We discovered HLA risk factors and four non-HLA susceptibility loci in VPS8, SVEP1, CFL2, and chr13q21 and reinforced IL12B, PTK2B, and chr21q22 as robust susceptibility loci shared across ancestries. Functional analysis proposed plausible underlying disease mechanisms and pinpointed ETS2 as a potential causal gene for chr21q22 association. We also identified >60 candidate loci with suggestive association (p < 5 x 10(-s)) and devised a genetic risk score for Takayasu arteritis. Takayasu arteritis was compared to hundreds of other traits, revealing the closest genetic relatedness to inflammatory bowel disease. Epigenetic patterns within risk loci suggest roles for monocytes and B cells in Takayasu arteritis. This work enhances understanding of the genetic basis and pathophysiology of Takayasu arteritis and provides clues for potential new therapeutic targets.
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| 10. |
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| 11. |
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| 12. |
- Marazioti, Antonia, et al.
(författare)
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KRAS signaling in malignant pleural mesothelioma
- 2022
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Ingår i: EMBO Molecular Medicine. - : EMBO. - 1757-4684 .- 1757-4676. ; 14:2
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Tidskriftsartikel (refereegranskat)abstract
- Malignant pleural mesothelioma (MPM) arises from mesothelial cells lining the pleural cavity of asbestos-exposed individuals and rapidly leads to death. MPM harbors loss-of-function mutations in BAP1, NF2, CDKN2A, and TP53, but isolated deletion of these genes alone in mice does not cause MPM and mouse models of the disease are sparse. Here, we show that a proportion of human MPM harbor point mutations, copy number alterations, and overexpression of KRAS with or without TP53 changes. These are likely pathogenic, since ectopic expression of mutant KRASG12D in the pleural mesothelium of conditional mice causes epithelioid MPM and cooperates with TP53 deletion to drive a more aggressive disease form with biphasic features and pleural effusions. Murine MPM cell lines derived from these tumors carry the initiating KRASG12D lesions, secondary Bap1 alterations, and human MPM-like gene expression profiles. Moreover, they are transplantable and actionable by KRAS inhibition. Our results indicate that KRAS alterations alone or in accomplice with TP53 alterations likely play an important and underestimated role in a proportion of patients with MPM, which warrants further exploration.
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| 13. |
- Stray-Pedersen, Asbjorg, et al.
(författare)
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Primary immunodeficiency diseases : Genomic approaches delineate heterogeneous Mendelian disorders
- 2017
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Ingår i: Journal of Allergy and Clinical Immunology. - : MOSBY-ELSEVIER. - 0091-6749 .- 1097-6825. ; 139:1, s. 232-245
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Tidskriftsartikel (refereegranskat)abstract
- Background: Primary immunodeficiency diseases (PIDDs) are clinically and genetically heterogeneous disorders thus far associated with mutations in more than 300 genes. The clinical phenotypes derived from distinct genotypes can overlap. Genetic etiology can be a prognostic indicator of disease severity and can influence treatment decisions. Objective: We sought to investigate the ability of whole-exome screening methods to detect disease-causing variants in patients with PIDDs. Methods: Patients with PIDDs from 278 families from 22 countries were investigated by using whole-exome sequencing. Computational copy number variant (CNV) prediction pipelines and an exome-tiling chromosomal microarray were also applied to identify intragenic CNVs. Analytic approaches initially focused on 475 known or candidate PIDD genes but were nonexclusive and further tailored based on clinical data, family history, and immunophenotyping. Results: A likely molecular diagnosis was achieved in 110 (40%) unrelated probands. Clinical diagnosis was revised in about half (60/ 110) and management was directly altered in nearly a quarter (26/ 110) of families based on molecular findings. Twelve PIDD-causing CNVs were detected, including 7 smaller than 30 Kb that would not have been detected with conventional diagnostic CNV arrays. Conclusion: This high-throughput genomic approach enabled detection of disease-related variants in unexpected genes; permitted detection of low-grade constitutional, somatic, and revertant mosaicism; and provided evidence of a mutational burden in mixed PIDD immunophenotypes.
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| 14. |
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| 15. |
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| 16. |
- Andreoli, L, et al.
(författare)
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EULAR recommendations for women's health and the management of family planning, assisted reproduction, pregnancy and menopause in patients with systemic lupus erythematosus and/or antiphospholipid syndrome
- 2017
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Ingår i: Annals of the rheumatic diseases. - : BMJ. - 1468-2060 .- 0003-4967. ; 76:3, s. 476-485
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Tidskriftsartikel (refereegranskat)abstract
- Develop recommendations for women's health issues and family planning in systemic lupus erythematosus (SLE) and/or antiphospholipid syndrome (APS).MethodsSystematic review of evidence followed by modified Delphi method to compile questions, elicit expert opinions and reach consensus.ResultsFamily planning should be discussed as early as possible after diagnosis. Most women can have successful pregnancies and measures can be taken to reduce the risks of adverse maternal or fetal outcomes. Risk stratification includes disease activity, autoantibody profile, previous vascular and pregnancy morbidity, hypertension and the use of drugs (emphasis on benefits from hydroxychloroquine and antiplatelets/anticoagulants). Hormonal contraception and menopause replacement therapy can be used in patients with stable/inactive disease and low risk of thrombosis. Fertility preservation with gonadotropin-releasing hormone analogues should be considered prior to the use of alkylating agents. Assisted reproduction techniques can be safely used in patients with stable/inactive disease; patients with positive antiphospholipid antibodies/APS should receive anticoagulation and/or low-dose aspirin. Assessment of disease activity, renal function and serological markers is important for diagnosing disease flares and monitoring for obstetrical adverse outcomes. Fetal monitoring includes Doppler ultrasonography and fetal biometry, particularly in the third trimester, to screen for placental insufficiency and small for gestational age fetuses. Screening for gynaecological malignancies is similar to the general population, with increased vigilance for cervical premalignant lesions if exposed to immunosuppressive drugs. Human papillomavirus immunisation can be used in women with stable/inactive disease.ConclusionsRecommendations for women's health issues in SLE and/or APS were developed using an evidence-based approach followed by expert consensus.
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| 17. |
- Bauer, Michael, et al.
(författare)
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Association between solar insolation and a history of suicide attempts in bipolar I disorder.
- 2019
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Ingår i: Journal of psychiatric research. - : Elsevier BV. - 1879-1379 .- 0022-3956. ; 113, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- In many international studies, rates of completed suicide and suicide attempts have a seasonal pattern that peaks in spring or summer. This exploratory study investigated the association between solar insolation and a history of suicide attempt in patients with bipolar I disorder. Solar insolation is the amount of electromagnetic energy from the Sun striking a surface area on Earth. Data were collected previously from 5536 patients with bipolar I disorder at 50 collection sites in 32 countries at a wide range of latitudes in both hemispheres. Suicide related data were available for 3365 patients from 310 onset locations in 51 countries. 1047 (31.1%) had a history of suicide attempt. There was a significant inverse association between a history of suicide attempt and the ratio of mean winter solar insolation/mean summer solar insolation. This ratio is smallest near the poles where the winter insolation is very small compared to the summer insolation. This ratio is largest near the equator where there is relatively little variation in the insolation over the year. Other variables in the model that were positively associated with suicide attempt were being female, a history of alcohol or substance abuse, and being in a younger birth cohort. Living in a country with a state-sponsored religion decreased the association. (All estimated coefficients p<0.01). In summary, living in locations with large changes in solar insolation between winter and summer may be associated with increased suicide attempts in patients with bipolar disorder. Further investigation of the impacts of solar insolation on the course of bipolar disorder is needed.
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| 18. |
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| 19. |
- Kowal-Bielecka, Otylia, et al.
(författare)
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Update of EULAR recommendations for the treatment of systemic sclerosis
- 2017
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 76, s. 1327-1339
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to update the 2009 European League against Rheumatism (EULAR) recommendations for the treatment of systemic sclerosis (SSc), with attention to new therapeutic questions. Update of the previous treatment recommendations was performed according to EULAR standard operating procedures. The task force consisted of 32 SSc clinical experts from Europe and the USA, 2 patients nominated by the pan-European patient association for SSc (Federation of European Scleroderma Associations (FESCA)), a clinical epidemiologist and 2 research fellows. All centres from the EULAR Scleroderma Trials and Research group were invited to submit and select clinical questions concerning SSc treatment using a Delphi approach. Accordingly, 46 clinical questions addressing 26 different interventions were selected for systematic literature review. The new recommendations were based on the available evidence and developed in a consensus meeting with clinical experts and patients. The procedure resulted in 16 recommendations being developed (instead of 14 in 2009) that address treatment of several SSc-related organ complications: Raynaud's phenomenon (RP), digital ulcers (DUs), pulmonary arterial hypertension (PAH), skin and lung disease, scleroderma renal crisis and gastrointestinal involvement. Compared with the 2009 recommendations, the 2016 recommendations include phosphodiesterase type 5 (PDE-5) inhibitors for the treatment of SSc-related RP and DUs, riociguat, new aspects for endothelin receptor antagonists, prostacyclin analogues and PDE-5 inhibitors for SSc-related PAH. New recommendations regarding the use of fluoxetine for SSc-related RP and haematopoietic stem cell transplantation for selected patients with rapidly progressive SSc were also added. In addition, several comments regarding other treatments addressed in clinical questions and suggestions for the SSc research agenda were formulated. These updated data-derived and consensus-derived recommendations will help rheumatologists to manage patients with SSc in an evidence-based way. These recommendations also give directions for future clinical research in SSc.
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| 20. |
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| 21. |
- Valent, P, et al.
(författare)
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Refined diagnostic criteria and classification of mast cell leukemia (MCL) and myelomastocytic leukemia (MML) : a consensus proposal
- 2014
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Ingår i: Annals of Oncology. - : Elsevier BV. - 0923-7534 .- 1569-8041. ; 25:9, s. 1691-1700
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Tidskriftsartikel (refereegranskat)abstract
- Mast cell leukemia (MCL), the leukemic manifestation of systemic mastocytosis (SM), is characterized by leukemic expansion of immature mast cells (MCs) in the bone marrow (BM) and other internal organs; and a poor prognosis. In a subset of patients, circulating MCs are detectable. A major differential diagnosis to MCL is myelomastocytic leukemia (MML). Although criteria for both MCL and MML have been published, several questions remain concerning terminologies and subvariants. To discuss open issues, the EU/US-consensus group and the European Competence Network on Mastocytosis (ECNM) launched a series of meetings and workshops in 2011-2013. Resulting discussions and outcomes are provided in this article. The group recommends that MML be recognized as a distinct condition defined by mastocytic differentiation in advanced myeloid neoplasms without evidence of SM. The group also proposes that MCL be divided into acute MCL and chronic MCL, based on the presence or absence of C-Findings. In addition, a primary (de novo) form of MCL should be separated from secondary MCL that typically develops in the presence of a known antecedent MC neoplasm, usually aggressive SM (ASM) or MC sarcoma. For MCL, an imminent prephase is also proposed. This prephase represents ASM with rapid progression and 5%-19% MCs in BM smears, which is generally accepted to be of prognostic significance. We recommend that this condition be termed ASM in transformation to MCL (ASM-t). The refined classification of MCL fits within and extends the current WHO classification; and should improve prognostication and patient selection in practice as well as in clinical trials.
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| 22. |
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| 23. |
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| 24. |
- Yavuz, Sule, et al.
(författare)
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Mer-tyrosine kinase : a novel susceptibility gene for SLE related end-stage renal disease
- 2022
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Ingår i: Lupus Science and Medicine. - : BMJ Publishing Group Ltd. - 2053-8790. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Objective Lupus nephritis (LN) is a common and severe manifestation of SLE. The genetic risk for nephritis and progression to end-stage renal disease (ESRD) in patients with LN remains unclear. Herein, we aimed to identify novel genetic associations with LN, focusing on subphenotypes and ESRD. Methods We analysed genomic data on 958 patients with SLE (discovery cohort: LN=338) with targeted sequencing data from 1832 immunological pathway genes. We used an independent multiethnic cohort comprising 1226 patients with SLE (LN=603) as a replication dataset. Detailed functional annotation and functional epigenomic enrichment analyses were applied to predict functional effects of the candidate variants. Results A genetic variant (rs56097910) within the MERTK gene was associated with ESRD in both cohorts, meta-analysis OR=5.4 (2.8 to 10.6); p=1.0×10-6. We observed decreased methylation levels in peripheral blood cells from SLE patients with ESRD, compared with patients without renal SLE (p=2.7×10-4), at one CpG site (cg16333401) in close vicinity to the transcription start site of MERTK and located in a DNAse hypersensitivity region in T and B cells. Rs56097910 is linked to altered MERTK expression in kidney tissue in public eQTL databases. Two loci were replicated for association with proliferative LN: PRDM1 (rs6924535, p meta =1.6×10-5, OR=0.58) and APOA1BP (NAXE) (rs942960, p meta =1.2×10-5, OR=2.64). Conclusion We identified a novel genetic risk locus, MERTK, associated with SLE-ESRD using the data from two large SLE cohorts. Through DNA methylation analysis and functional annotation, we showed that the risk could be mediated through regulation of gene expression. Our results suggest that variants in the MERTK gene are important for the risk of developing SLE-ESRD and suggest a role for PRDM1 and APOA1BP in proliferative LN.
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| 25. |
- Arslan, M. Tunc, et al.
(författare)
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Rapid TAURUS for Relaxation-Based Color Magnetic Particle Imaging
- 2022
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Ingår i: IEEE Transactions on Medical Imaging. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0062 .- 1558-254X. ; 41:12, s. 3774-3786
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic particle imaging (MPI) is a rapidly developing medical imaging modality that exploits the non- linear response of magnetic nanoparticles (MNPs). Color MPI widens the functionality of MPI, empowering it with the capability to distinguish differentMNPs and/orMNP environments. The system function approach for color MPI relies on extensive calibrations that capture the differences in the harmonic responses of the MNPs. An alternative calibration-free x-space-basedmethod called TAURUS estimates amap of the relaxation time constant, tau, by recovering the underlyingmirror symmetry in the MPI signal. However, TAURUS requires a back and forth scanning of a given region, restricting its usage to slow trajectories with constant or piecewise constant focus fields (FFs). In this work, we propose a novel technique to increase the performance of TAURUS and enable tau map estimation for rapid andmultidimensional trajectories. The proposed technique is based on correcting the distortions on mirror symmetry induced by time-varying FFs. We demonstrate via simulations and experiments in our in-house MPI scanner that the proposed method successfully estimates high-fidelity tau maps for rapid trajectories that provide orders of magnitude reduction in scanning time (over 300 fold for simulations and over 8 fold for experiments) while preserving the calibration-free property of TAURUS.
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| 26. |
- Bouchal, Johannes M., 1979-
(författare)
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Reconciling the stratigraphy and depositional history of the Lycian orogen-top basins, SW Anatolia
- 2019
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Ingår i: Palaeobiodiversity and Palaeoenvironments. - Heidelberg : Springer Science and Business Media LLC. - 1867-1594 .- 1867-1608. ; 99, s. 551-570
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Tidskriftsartikel (refereegranskat)abstract
- Terrestrial fossil records from the SW Anatolian basins are crucial both for regional correlations and palaeoenvironmental reconstructions. By reassessing biostratigraphic constraints and incorporating new fossil data, we calibrated and reconstructed the late Neogene and Quaternary palaeoenvironments within a regional palaeogeographical framework. The culmination of the Taurides in SW Anatolia was followed by a regional crustal extension from the late Tortonian onwards that created a broad array of NE-trending orogen-top basins with synchronic associations of alluvial fan, fluvial and lacustrine deposits. The terrestrial basins are superimposed on the upper Burdigalian marine units with a c. 7 myr of hiatus that corresponds to a shift from regional shortening to extension. The initial infill of these basins is documented by a transition from marginal alluvial fans and axial fluvial systems into central shallow-perennial lakes coinciding with a climatic shift from warm/humid to arid conditions. The basal alluvial fan deposits abound in fossil macro-mammals of an early Turolian (MN11–12; late Tortonian) age. The Pliocene epoch in the region was punctuated by subhumid/humid conditions resulting in a rise of local base levels and expansion of lakes as evidenced by marsh-swamp deposits containing diverse fossilmammal assemblages indicating late Ruscinian (lateMN15; late Zanclean) age. A second pulse of extension, accompanied by regional climatic changes, prompted subsequent deepening of the lakes as manifested by thick and laterally extensive carbonate successions. These lakes, which prevailed c. 1 myr, later shrank due to renewed progradation of alluvial fans and eventually filled up and dried out, reflected by marsh-swamp deposits at the top of a complete lacustrine succession that contains diverse micro-mammal assemblages indicating a latest Villanyian (MN17; Gelasian) age. A third pulse of tectonic reorganisation and associated extension dissected the basins into their present-day configuration from the early Pleistocene onwards under warm/humid climatic conditions. The new age data provide means to correlate deposits across various basins in the region that help to place the basin development into a regional tectonic framework, which can be attributed to the consequence of the well-articulated regional phenomena of slab-tear/detachmentinduced uplift followed by crustal extension and basin formation (late Tortonian), the outward extension of the Aegean arc (early Pliocene) and eventually accompanied by westward extrusion of the Anatolian Plate (early Pleistocene).
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| 27. |
- Briat, Corentin, et al.
(författare)
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A conservation-law-based modular fluid-flow model for network congestion modeling
- 2012
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Ingår i: 2012 Proceedings - IEEE INFOCOM. - : IEEE Computer Society. - 9781467307758 ; , s. 2050-2058
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Konferensbidrag (refereegranskat)abstract
- A modular fluid-flow model for network congestion analysis and control is proposed. The model is derived from an information conservation law stating that the information is either in transit, lost or received. Mathematical models of network elements such as queues, users, and transmission channels, and network description variables, including sending/ acknowledgement rates and delays, are inferred from this law and obtained by applying this principle locally. The modularity of the devised model makes it sufficiently generic to describe any network topology, and appealing for building simulators. Previous models in the literature are often not capable of capturing the transient behavior of the network precisely, making the resulting analysis inaccurate in practice. Those models can be recovered from exact reduction or approximation of this new model. An important aspect of this particular modeling approach is the introduction of new tight building blocks that implement mechanisms ignored by the existing ones, notably at the queue and user levels. Comparisons with packet-level simulations corroborate the proposed model.
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| 28. |
- Briat, Corentin, et al.
(författare)
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Impact of Queueing Delay Estimation Error on Equilibrium and Its Stability
- 2011
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Ingår i: NETWORKING 2011, PT II. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783642207983 ; , s. 356-367
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Konferensbidrag (refereegranskat)abstract
- Delay-based transmission control protocols need to separate round-trip time (RTT) measurements into their constituting parts: the propagation and the queueing delays. We consider two means for this; the first is to take the propagation delay as the minimum observed RTT value, and the second is to measure the queueing delay at the routers and feed it back to the sources. We choose FAST-TCP as a representative delay-based transmission control protocol for analysis and study the impact of delay knowledge errors on its performance. We have shown that while the first method destroys fairness and the uniqueness of the equilibrium, the stability of the protocol can easily be obtained through tuning the protocol terms appropriately. Even though the second technique is shown to preserve fairness and uniqueness of the equilibrium point, we have presented that unavoidable oscillations can occur around the equilibrium point.
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| 29. |
- Briat, C., et al.
(författare)
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The Conservation of Information, Towards an Axiomatized Modular Modeling Approach to Congestion Control
- 2015
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Ingår i: IEEE/ACM Transactions on Networking. - 1063-6692 .- 1558-2566. ; 23:3, s. 851-865
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Tidskriftsartikel (refereegranskat)abstract
- We derive a modular fluid-flow network congestion control model based on a law of fundamental nature in networks: the conservation of information. Network elements such as queues, users, and transmission channels and network performance indicators like sending/acknowledgment rates and delays are mathematically modeled by applying this law locally. Our contributions are twofold. First, we introduce a modular metamodel that is sufficiently generic to represent any network topology. The proposed model is composed of building blocks that implement mechanisms ignored by the existing ones, which can be recovered from exact reduction or approximation of this new model. Second, we provide a novel classification of previously proposed models in the literature and show that they are often not capable of capturing the transient behavior of the network precisely. Numerical results obtained from packet-level simulations demonstrate the accuracy of the proposed model.
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| 30. |
- Chen, Zhaofei, et al.
(författare)
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Demo of a collaborative music sharing system
- 2012
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Ingår i: MobiOpp'12 - Proceedings of the 3rd ACM International Workshop on Mobile Opportunistic Networks. - New york : ACM. - 9781450312080 ; , s. 77-78
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Konferensbidrag (refereegranskat)abstract
- We demonstrate a wireless real-time music-sharing application that lets users play music directly from their mobiles through a jukebox. We have designed and implemented the application by using a previously developed content-centric opportunistic networking middleware. The jukebox plays the music file that is first in its playlist by streaming it in real-time from the publishing user device. All users can observe the collaboratively formed playlist on their mobiles in real-time. The application shows the usefulness of our middleware and demonstrates a new form of situated applications. The application handles churn and garbage collection after departed users.
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| 31. |
- Erdemir, Sertac, et al.
(författare)
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Noise Analysis of On-Chip Flexing Crossbars With a Geometric Model
- 2016
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Ingår i: 2016 IEEE INTERNATIONAL SYMPOSIUM ON ELECTROMAGNETIC COMPATIBILITY (EMC). - : IEEE. - 9781509014415 ; , s. 478-484
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Konferensbidrag (refereegranskat)abstract
- Recently, a new family of sparse crossbar switches, called flexing crossbars were introduced in [1] for on-chip networking. This paper describes a geometric approach that incorporates victim-aggressor noise models into the noise analysis and layout of such networks to minimize the crosstalk noise caused by the proximity of crosspoints and wires. It has been shown that flexing crossbars have less crosstalk noise than ordinary crossbars. The approach is sufficiently general enough to be applicable to other switching fabrics in which capacitive wire coupling effects dominate other noise factors.
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| 32. |
- Essalhi, Mohamed, et al.
(författare)
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Development of a Lycopodium powder-based superhydrophobic nanofiber membrane suitable for desalination
- 2023
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Ingår i: Separation and Purification Technology. - : Elsevier. - 1383-5866 .- 1873-3794. ; 323
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Tidskriftsartikel (refereegranskat)abstract
- A biobased, green, inexpensive additive, Lycopodium particles, which are spores of the “Lycopodium clavatum” plant, were incorporated in the poly(vinylidene fluoride) PVDF electrospun nanofiber membranes (ENMs) for desalination by direct contact membrane distillation (DCMD). Superhydrophobic ENMs were prepared using this additive (PVDF-ENMs-Lyc). Thanks to their morphological structure and their prominent surface superhydrophobicity (anti-wetting) character, the resulting PVDF-ENMs-Lyc exhibited an improved liquid entry pressure (LEP), a high void volume fraction (greater than 87.2%), a good salt rejection factor (greater than 99.93%) and a reasonably high permeate flux (greater than 51.76 kg·m-2·h-1) at 80 °C, which are of great practical importance for water desalination by DCMD. The optimum membrane prepared with 3 wt% Lycopodium in the dope solution demonstrated a stable permeate flux of 52.4 ± 0.6 kg·m-2·h-1 with an electrical conductivity around 4.76 ± 0.46 μS/cm (NaCl rejection factor of 99.998 ± 0.036%) during 25 h DCMD desalination experiment using 35 g/L NaCl aqueous solution (similar to seawater concentration). The presented results pave the way for superhydrophobic nanofibrous membrane engineering suitable for membrane contactors by electrospinning in a single step without surfactants, organic additives, or chemical post-treatments, just by the incorporation of a green additive like Lycopodium powder.
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| 33. |
- Fortetsanakis, G., et al.
(författare)
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To subscribe, or not to subscribe : Modeling and analysis of service paradigms in cellular markets
- 2012
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Ingår i: 2012 IEEE International Symposium on Dynamic Spectrum Access Networks, DYSPAN 2012. - : IEEE. - 9781467344487 ; , s. 189-200
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Konferensbidrag (refereegranskat)abstract
- Traditionally customers subscribe to specific providers and are served by accessing base stations (BSs) of the network of their provider. Inevitably subscribers with relatively 'high' usage pattern and data-rate requirements are subsidized by the ones with lower usage and data-rates. As the wireless technology advances, a diverse set of services will be available. This paper introduces the 'flex service' paradigm that allows a customer to dynamically access BSs of different providers based on various criteria, such as profile, network conditions, and offered prices. 'Flex users' can select the appropriate provider and BS on a per-session basis. This work considers a diverse customer population with respect to their demand, their preference on data-rate over price, their tolerance on the blocking probabilities of their sessions, and their willingness to pay for certain services. Users can dynamically decide to buy a long-term subscription or become flex users. In this paper, we develop a rich framework for modeling and analysis of such markets in different spatio-temporal scales. We analyze the evolution of markets with the flex service paradigm, focusing on whether it can improve the quality-of-service (QoS), social welfare, flexibility and further enhance the competition among providers. The main contribution of this paper is detailed modeling and indepth performance analysis of such complex markets, in different spatial and temporal scales. It considers the perspective of clients, providers, and regulators. It demonstrates the benefits of markets with the flex service paradigm and compares them with the ones that only offer subscription contracts.
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| 34. |
- Gaget, Elie, et al.
(författare)
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Benefits of protected areas for nonbreeding waterbirds adjusting their distributions under climate warming
- 2021
-
Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 35:3, s. 834-845
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Tidskriftsartikel (refereegranskat)abstract
- Climate warming is driving changes in species distributions and community composition. Many species have a so-called climatic debt, that is, shifts in range lag behind shifts in temperature isoclines. Inside protected areas (PAs), community changes in response to climate warming can be facilitated by greater colonization rates by warm-dwelling species, but also mitigated by lowering extirpation rates of cold-dwelling species. An evaluation of the relative importance of colonization-extirpation processes is important to inform conservation strategies that aim for both climate debt reduction and species conservation. We assessed the colonization-extirpation dynamics involved in community changes in response to climate inside and outside PAs. To do so, we used 25 years of occurrence data of nonbreeding waterbirds in the western Palearctic (97 species, 7071 sites, 39 countries, 1993–2017). We used a community temperature index (CTI) framework based on species thermal affinities to investigate species turnover induced by temperature increase. We determined whether thermal community adjustment was associated with colonization by warm-dwelling species or extirpation of cold-dwelling species by modeling change in standard deviation of the CTI (CTISD). Using linear mixed-effects models, we investigated whether communities in PAs had lower climatic debt and different patterns of community change than communities outside PAs. For CTI and CTISD combined, communities inside PAs had more species, higher colonization, lower extirpation, and lower climatic debt (16%) than communities outside PAs. Thus, our results suggest that PAs facilitate 2 independent processes that shape community dynamics and maintain biodiversity. The community adjustment was, however, not sufficiently fast to keep pace with the large temperature increases in the central and northeastern western Palearctic. Our results underline the potential of combining CTI and CTISD metrics to improve understanding of the colonization-extirpation patterns driven by climate warming.
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| 35. |
- Helgason, Ólafur, et al.
(författare)
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A Middleware for Opportunistic Content Distribution
- 2016
-
Ingår i: Computer Networks. - : Elsevier. - 1389-1286 .- 1872-7069. ; 107, s. 178-193
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present a middleware architecture for a mobile peer-to-peer content distribution system. Our architecture allows wireless content dissemination between mobile nodes without relying on infrastructure support. In addition, it supports the dissemination of contents between the wireless ad-hoc domain and the wired Internet. In the ad-hoc domain, contents are exchanged opportunistically when nodes are within communication range. Applications access the service of our platform through a publish/subscribe interface and therefore do not have to deal with low-level opportunistic networking issues or matching and soliciting of contents. Our middleware consists of three key components. A content structure that facilitates dividing contents into logical topics and allows efficient matching of content lookups and downloading under sporadic node connectivity. A solicitation protocol that allows nodes to solicit content meta-information in order to discover contents available at a neighboring node and to download content entries disjointedly from different nodes. An API that allows applications to access the system services through a publish/subscribe interface. In this work we present the design and implementation of our middleware and describe a set of applications that use the services provided by our middleware. We also assess the performance of the system using our Android implementation as well as a simulation implementation for large-scale evaluation.
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| 36. |
- Helgason, Ólafur, et al.
(författare)
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A mobile peer-to-peer system for opportunistic content-centric networking
- 2010
-
Ingår i: Proceedings of the 2nd ACM SIGCOMM Workshop on Networking, Systems, and Applications on Mobile Handhelds, MobiHeld '10, Co-located with SIGCOMM 2010. - New York, NY, USA : ACM. - 9781450301978 ; , s. 21-26
-
Konferensbidrag (refereegranskat)abstract
- In this work we present a middleware architecture for a mobile peer-to-peer content distribution system. Our architecture allows wireless content dissemination between mobile nodes without relying on infrastructure support. Contents are exchanged opportunistically when nodes are within communication range. Applications access the service of our platform through a publish/subscribe interface and therefore do not have to deal with low-level opportunistic networking issues or matching and soliciting of contents. Our architecture consists of three key components. A content structure that facilitates dividing contents into logical topics and allows for efficient matching of content lookups and downloading under sporadic node connectivity. A solicitation protocol that allows nodes to solicit content meta-information in order to discover contents available at a neighboring node and to download content entries disjointedly from different nodes. An API that allows applications to access the system services through a publish/subscribe interface. In this work we describe the design and implementation of our architecture. We also discuss potential applications and present evaluation results from profiling of our system.
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| 37. |
- Karlsson, Gunnar, et al.
(författare)
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A Future Wireless Internet Beyond Generations
- 2010
-
Ingår i: Proceedings of the 5th International Conference on Future Internet Technologies, CFI10. - New York, NY, USA : ACM. - 9781450302302 ; , s. 5-9
-
Konferensbidrag (refereegranskat)abstract
- The use of licensed spectrum for wireless communication is driven by the need to control interference between operators. This regulation leads to inefficient utilization of spectrum and causes shortage of free spectrum that hinders the entry of new operators and introduction of new wireless technologies. In this work, we present an evolutionary model for which license-free operation is the spectrum sharing mode so that networks can be built freely by anyone and new technologies can be deployed as soon as they become available. The paradigm assumes users to have open access to all public networks without prior contracts with operators. Hence, freely roaming users will drive competition among wireless network access providers, who in turn can meet demand quickly by offering access at low price, high quality, in hitherto uncovered areas, and by means of novel superior technology. We present a straw-man design and discuss the inherent technical challenges that must be addressed.
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| 38. |
- Kennedy, Vanessa E., et al.
(författare)
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Mast cell leukemia : clinical and molecular features and survival outcomes of patients in the ECNM Registry
- 2023
-
Ingår i: Blood Advances. - : American Society of Hematology. - 2473-9529 .- 2473-9537. ; 7:9, s. 1713-1724
-
Tidskriftsartikel (refereegranskat)abstract
- Mast cell leukemia (MCL) is a rare subtype of systemic mastocytosis defined by >= 20% mast cells (MC) on a bone marrow aspirate. We evaluated 92 patients with MCL from the European Competence Network on Mastocytosis registry. Thirty-one (34%) patients had a diagnosis of MCL with an associated hematologic neoplasm (MCL-AHN). Chronic MCL (lack of C-findings) comprised 14% of patients, and only 4.5% had "leukemic MCL" (>= 10% circulating MCs). KIT D816V was found in 62/85 (73%) evaluable patients; 9 (11%) individuals exhibited alternative KIT mutations, and no KIT variants were detected in 14 (17%) subjects. Ten evaluable patients (17%) had an abnormal karyotype and the poor-risk SRSF2, ASXL1, and RUNX1 (S/A/R) mutations were identified in 16/36 (44%) patients who underwent next-generation sequencing. Midostaurin was the most common therapy administered to 65% of patients and 45% as first-line therapy. The median overall survival (OS) was 1.6 years. In multivariate analysis (S/A/R mutations excluded owing to low event rates), a diagnosis of MCL-AHN (hazard ratio [HR], 4.7; 95% confidence interval [CI], 1.7-13.0; P = .001) and abnormal karyotype (HR, 5.6; 95% CI, 1.4-13.3; P = .02) were associated with inferior OS; KIT D816V positivity (HR, 0.33; 95% CI, 0.11-0.98; P = .04) and midostaurin treatment (HR, 0.32; 95% CI, 0.08-0.72; P = .008) were associated with superior OS. These data provide the most comprehensive snapshot of the clinicopathologic, molecular, and treatment landscape of MCL to date, and should help further inform subtyping and prognostication of MCL.
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| 39. |
- Kouyoumdjieva, Sylvia, et al.
(författare)
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Evaluating an Energy-efficient Radio Architecture for Opportunistic Communication
- 2012
-
Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 5751-5756
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Konferensbidrag (refereegranskat)abstract
- A major challenge for wireless networks is to minimize the energy consumption in the mobile devices. This work evaluates potential performance gains of a dual-radio architecture in which a low power radio is used to wake up the primary high power radio. Our targeted domain is opportunistic communication directly between devices. We show that it can significantly reduce the energy consumption at a price of slightly decreased goodput. We also examine the effect of the MAC protocol on the performance of the dual-radio system and we point out that in dense scenarios MAC layer protocols, such as of 802.15.4, do not perform well. We observe that information on device density of an environment can be used to address this shortcoming.
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| 40. |
- Kouyoumdjieva, Sylvia, et al.
(författare)
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Opportunistic Content-Centric Networking : The Conference Case Demo
- 2011
-
Ingår i: Proceedings of the IEEE International Conference on Computer Communications, INFOCOM’11.
-
Konferensbidrag (refereegranskat)abstract
- We present a demonstration scenario to evaluate a middleware architecture that we designed and implemented for distributing content over mobile ad hoc networks. The peer to-peer networking architecture allows content dissemination between mobile devices without relying on any infrastructure support. Content is exchanged opportunistically when nodes are in proximity. We developed a mobile application utilizing the services provided by the implemented middleware. The application facilitates opportunistic content distribution in both one-to-one and one-to-many dissemination modes.
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| 41. |
- Masoudi, Meysam, et al.
(författare)
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Grant-Free Radio Access IoT Networks : Scalability Analysis in Coexistence Scenarios
- 2018
-
Ingår i: IEEE International Conference on Communications. - : Institute of Electrical and Electronics Engineers Inc.. - 9781538631805
-
Konferensbidrag (refereegranskat)abstract
- IoT networks with grant-free radio access, like SigFox and LoRa, offer low-cost durable communications over unlicensed band. These networks are becoming more and more popular due to the ever-increasing need for ultra durable, in terms of battery lifetime, IoT networks. Most studies evaluate the system performance assuming single radio access technology deployment. In this paper, we study the impact of coexisting competing radio access technologies on the system performance. Considering K technologies, defined by time and frequency activity factors, bandwidth, and power, which share a set of radio resources, we derive closed-form expressions for the successful transmission probability, expected battery lifetime, and experienced delay as a function of distance to the serving access point. Our analytical model, which is validated by simulation results, provides a tool to evaluate the coexistence scenarios and analyze how introduction of a new coexisting technology may degrade the system performance in terms of success probability and battery lifetime. We further investigate solutions in which this destructive effect could be compensated, e.g., by densifying the network to a certain extent and utilizing joint reception.
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| 42. |
- Pajevic, Ljubica, et al.
(författare)
-
Demo : Opportunistic Mobile Social Networking
- 2011
-
Ingår i: Proc. ACM Annual International Conference on Mobile Systems, Applications and Services, MobiSys’11. - New York, NY, USA : ACM.
-
Konferensbidrag (refereegranskat)abstract
- We present a demonstration scenario to validate a middleware architecture that we designed and implemented for distributing content between mobile users in an opportunistic manner. The peer-to-peer networking architecture allows content dissemination between mobile devices without relying on any infrastructure support. We developed a mobile application utilizing the services provided by the implemented middleware. The application facilitates opportunistic content distribution in both one-to-one and one-to-many dissemination modes.
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| 43. |
- Wopereis, Harm, et al.
(författare)
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A specific synbiotic-containing amino acid-based formula restores gut microbiota in non-IgE mediated cow's milk allergic infants : a randomized controlled trial
- 2019
-
Ingår i: Clinical and Translational Allergy. - : BMC. - 2045-7022. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Altered gut microbiota is implicated in cow’s milk allergy (CMA) and differs markedly from healthy, breastfed infants. Infants who suffer from severe CMA often rely on cow’s milk protein avoidance and, when breastfeeding is not possible, on specialised infant formulas such as amino-acid based formulas (AAF). Herein, we report the effects of an AAF including specific synbiotics on oral and gastrointestinal microbiota of infants with non-IgE mediated CMA with reference to healthy, breastfed infants.Methods: In this prospective, randomized, double-blind controlled study, infants with suspected non-IgE mediated CMA received test or control formula. Test formula was AAF with synbiotics (prebiotic fructo-oligosaccharides and probiotic Bifidobacterium breve M-16V). Control formula was AAF without synbiotics. Healthy, breastfed infants were used as a separate reference group (HBR). Bacterial compositions of faecal and salivary samples were analysed by 16S rRNA-gene sequencing. Faecal analysis was complemented with the analysis of pH, short-chain fatty acids (SCFAs) and lactic acids.Results: The trial included 35 test subjects, 36 controls, and 51 HBR. The 16S rRNA-gene sequencing revealed moderate effects of test formula on oral microbiota. In contrast, the gut microbiota was substantially affected across time comparing test with control. In both groups bacterial diversity increased over time but was characterised by a more gradual increment in test compared to control. Compositionally this reflected an enhancement of Bifidobacterium spp. and Veillonella sp. in the test group. In contrast, the control-fed infants showed increased abundance of adult-like species, mainly within the Lachnospiraceaefamily, as well as within the Ruminococcus and Alistipes genus. The effects on Bifidobacterium spp. and Lachnospiraceae spp. were previously confirmed through enumeration by fluorescent in situ hybridization and were shown for test to approximate the proportions observed in the HBR. Additionally, microbial activity was affected as evidenced by an increase of l-lactate, a decrease of valerate, and reduced concentrations of branched-chain SCFAs in test versus control.Conclusions: The AAF including specific synbiotics effectively modulates the gut microbiota and its metabolic activity in non-IgE mediated CMA infants bringing it close to a healthy breastfed profile.
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| 44. |
- Yavuz, Emre A., et al.
(författare)
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A practical method for estimating performance metrics of call admission control schemes in wireless mobile networks
- 2005
-
Ingår i: 2005 IEEE Wireless Communications and Networking Conference, Vols 1-4. - 0780389662 ; , s. 1254-1259
-
Konferensbidrag (refereegranskat)abstract
- Providing the desired call blocking probability to not only new but also existing calls has been a challenge for wireless mobile network service providers. To satisfy different requirements for new and handoff call blocking probabilities, several call admission control (CAC) schemes have been proposed in the literature. Exact analysis of these schemes using two dimensional Markov chain is computationally intensive. Therefore under specific assumptions computationally efficient methods to analyze these systems using one dimensional Markov chain models have been considered. The "traditional" approach assumes that channel holding time for new and handoff calls have equal mean values. While the "normalized" approach relaxes this assumption, it is accurate only for the new call bounding CAC scheme. In this paper, we reevaluate the analytical methods for computing call blocking probabilities for several widely known call admission control schemes under more general assumptions by providing an easy to implement method. The numerical results show that when the average values of channel holding times for new and handoff calls are different, the proposed approach gives more accurate results when compared with the traditional and normalized methods based on one dimensional Markov chain modeling, while keeping the computational complexity low.
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| 45. |
- Yavuz, Emre A., et al.
(författare)
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Computationally efficient method to evaluate the performance of guard-channel-based call admission control in cellular networks
- 2006
-
Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 55:4, s. 1412-1424
-
Tidskriftsartikel (refereegranskat)abstract
- Many guard-channel-based call admission control (CAC) schemes for cellular networks have been proposed to provide the desired quality of service to not only new calls but also ongoing calls when they hand off to neighboring cells. Blocking/dropping probabilities of new/handoff calls are generally analyzed using one-dimensional Markov chain modeling under specific assumptions to avoid solving large sets of flow equations that makes exact analyses of these schemes using multidimensional Markov chain models infeasible. This is the case with the "traditional" approach, which assumes that channel holding times for new and handoff calls have equal mean values, and the "normalized" approach, which relaxes this assumption but is accurate only for the new call bounding CAC scheme. In this paper, we reevaluate the analytical methods for computing new/handoff call blocking/dropping probabilities for several widely known CAC schemes and develop an easy-to-implement method under more general assumptions. Numerical results show that when the mean channel holding times for new and handoff calls are different, the proposed "effective holding time" approach gives more accurate results compared with the traditional and the normalized methods while keeping the computational complexity low. The accuracy of these methods and their levels of computational complexity with the exact solution are also compared.
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| 46. |
- Yavuz, Emre A., et al.
(författare)
-
Efficient approximations for call admission control performance evaluations in multi-service networks
- 2006
-
Ingår i: GLOBECOM 2006. - 9781424403561
-
Konferensbidrag (refereegranskat)abstract
- Several dynamic call admission control (CAC) schemes for cellular networks have been proposed in the literature to reserve resources adaptively to provide the desired quality of service (QoS) to not only high priority calls but also to low priority ones. Efficient adaptive reservations depend on reliable and up-to-date system status feedback provided to the CAC mechanism. However exact analysis of these schemes using multidimensional Markov chain models are intractable in real time due to the need to solve large sets of flow equations. Hence performance metrics such as call blocking probabilities of various QoS classes are generally evaluated using one dimensional Markov chain models assuming that channel occupancy times for all QoS classes have equal mean values and all arriving calls have equal capacity requirements. In this paper we re-evaluate the analytical methods to compute call blocking probabilities of various QoS classes for several widely known CAC schemes by relaxing these assumptions, and propose a novel approximation method for performance evaluation with low computational complexity. Numerical results show that proposed method provides results that match well with the exact solutions.
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| 47. |
- Yavuz, Emre A., et al.
(författare)
-
Efficient Methods for Performance Evaluations of Call Admission Control Schemes in Multi-Service Cellular Networks
- 2008
-
Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276 .- 1558-2248. ; 7:9, s. 3468-3476
-
Tidskriftsartikel (refereegranskat)abstract
- Many dynamic call admission control (CAC) schemes have been proposed in the literature for adaptive reservations in cellular networks. Efficient application of these schemes requires reliable and up-to-date feedback of system performance to the CAC mechanism. However, exact analyses of these schemes in real time using multi-dimensional Markov chain models are challenging due to the need to solve large sets of flow equations. One dimensional Markov chain models have been widely used to derive performance metrics such as call blocking probabilities of multiple traffic classes assuming that all classes of calls have equal capacity requirements and exponentially distributed channel holding times with equal mean values. These assumptions need to be relaxed for a more general evaluation of CAC performance in multi-service cellular networks. In this paper we classify CAC schemes according to their Markov chain models into two categories: symmetric and asymmetric, and develop computationally efficient analytical methods to compute call blocking probabilities of various traffic classes for several widely known CAC schemes under relaxed assumptions. We obtain a product form solution to evaluate symmetric schemes and propose a novel performance evaluation approximation method with low computational cost for asymmetric schemes. Numerical results demonstrate the accuracy and efficiency of the proposed method.
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| 48. |
- Yavuz, Emre A., et al.
(författare)
-
Modelling channel occupancy times for voice traffic in cellular networks
- 2007
-
Ingår i: 2007 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, VOLS 1-14. - 9781424403523 ; , s. 332-337
-
Konferensbidrag (refereegranskat)abstract
- Call holding times in telephony networks are commonly approximated by exponential distributions to facilitate traffic engineering. However, for traffic engineering of cellular networks, channel occupancy times need to be modeled instead to facilitate analytical modeling or to feed network simulations. In this paper, we classify channel occupancy times and present an empirical study based on data obtained from a real cellular network to determine which probability distribution functions can approximate them better. The results are environment dependent, but no assumptions that can be influential are made, as opposed to previous analytical and simulation studies which results are highly dependent on the assumptions made by the authors. We show that all types of channel occupancy times can be approximated by lognormal distribution. For stationary users, channel occupancy times are commonly approximated by exponential distribution due to its tractability, assuming that cell residence times are also exponentially distributed. However, we show that lognormal distribution fits much better to both channel occupancy and call holding times regardless of whether users are stationary or mobile.
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| 49. |
- Yavuz, Emre A., et al.
(författare)
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Poster : Collective Mobile Sensing for Wireless Network Performance Monitoring
- 2011
-
Ingår i: Proc. ACM Annual International Conference on Mobile Systems, Applications and Services. - New York, NY, USA : ACM. - 9781450306430 ; , s. 411-
-
Konferensbidrag (refereegranskat)abstract
- Rapid growth of mobile wireless industry has generated numerous challenges for service operators. The provisioning of increasing demand in capacity and higher quality of service can be met with redimensioning of networks which makes a priori network planning difficult. We propose a network performance monitoring system to which all mobile devices contribute by voluntarily submitting periodical reports on the availability and quality of network access that they experience at their current geographical locations. Network performance measures such as signal strength, coverage, call block/drop statistics and operator service capabilities are reported to a server with a network status information database as experienced by mobile devices. The proposed database will indicate areas with lack of coverage, insufficient capacity, and high interference, which may serve as cues for operators to upgrade/retune their infrastructure equipment and for regulators to take action against operators that do not fulfill commitments made to their subscribers.
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